This file was created by the TYPO3 extension publications --- Timezone: CEST Creation date: 2026-05-13 Creation time: 23:37:43 --- Number of references 312 article Urrutia-Fucugauchi2025 Article 2025 10.3389/feart.2025.1550746 Frontiers in Earth Science 13 https://www.scopus.com/inward/record.uri?eid=2-s2.0-105007102466&doi=10.3389%2ffeart.2025.1550746&partnerID=40&md5=36276d70bfefe01bd0d169720552da09 Cited by: 0; All Open Access, Gold Open Access Jaime Urrutia-Fucugauchi Ligia Pérez-Cruz Axel Wittmann José A. ARZ Ignacio ARENILLAS Long Xiao Jiawei Zhao Vicente Gilabert Eduardo Salguero-Hernandez article OMalley20252271 Article 2025 10.1130/B37962.1 Bulletin of the Geological Society of America 137 2271 – 2286 5-6 https://www.scopus.com/inward/record.uri?eid=2-s2.0-105004425147&doi=10.1130%2fB37962.1&partnerID=40&md5=55ed63ed300c53398fa164b4a6d91695 Cited by: 0 Katherine O’Malley David De Vleeschouwer Christopher M. Lowery Sean P. S. Gulick Michael T. Whalen article Sato2025 Article 2025 10.1038/s41467-025-58112-x Nature Communications 16 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-105002981038&doi=10.1038%2fs41467-025-58112-x&partnerID=40&md5=854d5e02fef476398214220993deb01d Cited by: 0; All Open Access, Gold Open Access Honami Sato Akira Ishikawa Ignacio ARENILLAS José A. ARZ Vicente Gilabert Philippe Claeys Steven Goderis Christopher M. Lowery Sean P. S. Gulick Joanna V. Morgan article RN96 2024 10.22498/pages.32.2.82 Past Global Changes Magazine 32 82-83 2 L. Pérez-Cruz J. Urrutia-Fucugauchi article Martell2024 With several upcoming sample return missions, such as the Mars Sample Return Campaign, non-destructive methods will be key to maximizing their scientific output. In this study, we demonstrate that the combination of neutron and X-ray tomography provides an important tool for the characterization of such valuable samples. These methods allow quantitative analyses of internal sample features and also provide a guide for further destructive analyses with little to no sample treatment, which maintains sample integrity, including minimizing the risk of potential contamination. Here, we present and review the results from four case studies of terrestrial impactites and meteorites along with their analytical setup. Using combined X-ray and neutron tomography, a Ni-Fe silicide spherule, that is, projectile material, was located within a Libyan Desert Glass sample and the distribution of hydrous phases was pinpointed in selected impactite samples from the Chicxulub IODP-ICDP Expedition 364 drill core and the Luizi impact structure, as well as in the Miller Range 03346 Martian meteorite. © 2024. The Authors. Review 2024 10.1029/2023JE008222 Journal of Geophysical Research: Planets 129 John Wiley and Sons Inc 2 impact structure; iron; Mars; meteorite; nickel; spherule; X-ray tomography https://www.scopus.com/inward/record.uri?eid=2-s2.0-85184929812&doi=10.1029%2f2023JE008222&partnerID=40&md5=5c306321fd38f66de738d4e447de63f2 Cited by: 1; All Open Access, Hybrid Gold Open Access J. Martell C. Alwmark R. Woracek S. Alwmark S. Hall L. Ferrière L. Daly C. Bender Koch J. Hektor S. Johansson L. Helfen A. Tengattini D. Mannes article Quraish2024 In 2016, IODP-ICDP Expedition 364 recovered an 829-meter-long core within the peak ring of the Chicxulub impact crater (Yucatán, Mexico), allowing us to investigate the post-impact recovery of the heat-sterilized deep continental microbial biosphere at the impact site. We recently reported increased cell biomass in the impact suevite, which was deposited within the first few hours of the Cenozoic, and that the overall microbial communities differed significantly between the suevite and the other main core lithologies (i.e., the granitic basement and the overlying Early Eocene marine sediments; Cockell et al., 2021). However, only seven rock intervals were previously analyzed from the geologically heterogenic and impact-deformed 587-m-long granitic core section below the suevite interval. Here, we used 16S rRNA gene profiling to study the microbial community composition in 45 intervals including (a) 31 impact-shocked granites, (b) 7 non-granitic rocks (i.e., consisting of suevite and impact melt rocks intercalated into the granites during crater formation and strongly serpentinized pre-impact sub-volcanic, ultramafic basanite/dolerite), and (c) 7 cross-cut mineral veins of anhydride and silica. Most recovered microbial taxa resemble those found in hydrothermal systems. Spearman correlation analysis confirmed that the borehole temperature, which gradually increased from 47 to 69°C with core depth, significantly shaped a subset of the vertically stratified modern microbial community composition in the granitic basement rocks. However, bacterial communities differed significantly between the impoverished shattered granites and nutrient-enriched non-granite rocks, even though both lithologies were at similar depths and temperatures. Furthermore, Spearman analysis revealed a strong correlation between the microbial communities and bioavailable chemical compounds and suggests the presence of chemolithoautotrophs, which most likely still play an active role in metal and sulfur cycling. These results indicate that post-impact microbial niche separation has also occurred in the granitic basement lithologies, as previously shown for the newly formed lithologies. Moreover, our data suggest that the impact-induced geochemical boundaries continue to shape the modern-day deep biosphere in the granitic basement underlying the Chicxulub crater. © 2023 The Authors. Geobiology published by John Wiley & Sons Ltd. Article 2024 10.1111/gbi.12583 Geobiology 22 John Wiley and Sons Inc 1 Bacteria; Microbiota; RNA, Ribosomal, 16S; Silicon Dioxide; Mexico [North America]; Yucatan; acid anhydride; chemical compound; mineral; RNA 16S; silicon dioxide; sulfur; basement rock; bioavailability; borehole; cell; crater; granitoid; hydrothermal system; marine sediment; microbial activity; microbial community; separation; sulfur cycle; article; bioavailability; biogeochemical cycling; biomass; biosphere; chemolithoautotroph; correlation analysis; granite; Mexico; microbial community; nonhuman; Paleozoic; rock; sediment; temperature; Ypresian https://www.scopus.com/inward/record.uri?eid=2-s2.0-85181216283&doi=10.1111%2fgbi.12583&partnerID=40&md5=d3c2e59f7ea05b2995eb1152a00a3ee5 Cited by: 0; All Open Access, Hybrid Gold Open Access Sohaib Naseer Quraish Charles Cockell Cornelia Wuchter David Kring Kliti Grice Marco J. L. Coolen article Kaskes2024 Article 2024 10.1093/pnasnexus/pgad414 PNAS Nexus 3 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85182567708&doi=10.1093%2fpnasnexus%2fpgad414&partnerID=40&md5=1da0b1f6695b6952198db5e78492bdfe Cited by: 0; All Open Access, Gold Open Access Pim Kaskes Marta Marchegiano Marion Peral Steven Goderis Philippe Claeys article Alexander2024 Article 2024 10.1029/2023EA003383 Earth and Space Science 11 5 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85192465319&doi=10.1029%2f2023EA003383&partnerID=40&md5=82264c2d665c1720752de3073f2efb0c Cited by: 2 Amanda M. Alexander Simone Marchi Brandon C. Johnson Sean E. Wiggins David A. Kring article Zhao2024 Article 2024 10.1016/j.epsl.2023.118507 Earth and Planetary Science Letters 626 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85179136507&doi=10.1016%2fj.epsl.2023.118507&partnerID=40&md5=ce4c430726a63bc6f3357c2da3a78006 Cited by: 3 Jiawei Zhao Xiang Zhang Long Xiao Aaron J. Cavosie Nicholas E. Timms Alexander Nemchin Zhiyong Xiao Wentao Hu Yuqing Chang Jinfu Shu Qi He Shanrong Zhao Jiang Wang Jiannan Zhao article WOS:001178154800006 Article 2024 10.1130/B36547.1 GEOLOGICAL SOCIETY OF AMERICA BULLETIN 136 GEOLOGICAL SOC AMER, INC 307-328 1-2 Bruno Daniel Leite Mendes Agnes Kontny Michael Poelchau Lennart A. Fischer Ksenia Gaus Katarzyna Dudzisz Bonny W. M. Kuipers Mark J. Dekkers article Garroni2023834 Carbonates from the impact melt-bearing breccia in the 2016 IODP/ICDP Expedition 364 drill core at Site M0077 were systematically documented and characterized petrographically and geochemically. Calcite, the only carbonate mineral present, is abundant throughout this deposit as five distinct varieties: (1) subangular carbonate clasts (Type A); (2) subround/irregular carbonate clasts with clay altered rims (Type B); (3) fine-crystalline matrix calcite (Type C); (4) void-filling sparry calcite (Type D); and (5) microcrystalline carbonate with flow textures (Type E). Quantitative geochemical analysis shows that calcite in all carbonate varieties are low in elemental impurities (<2.0 cumulative wt% on average); however, relative concentrations of MgO and MnO vary, which provides distinction between each variety: MgO is highest in calcite from Types A, B, and C carbonates (0.2–0.8 wt% on average); MnO is highest in calcite from Types B, C, and D carbonates (0.2–1.3 wt% on average); and calcite from Type E carbonate is most pure (<0.1 wt% on average MgO and MnO, cumulatively). Based on textural and geochemical variations between carbonate types, we interpret that some of the carbonate target rocks melted during impact and were immiscible within the silicate-dominated melt sheet prior to the resurgence of seawater. Type B clasts were formed by molten fuel–coolant interaction, as the incoming seawater eroded through the melt sheet and encountered carbonate melt (Type E). Post-impact meteoric-dominated hydrothermal activity produced the Mn-elevated calcite from Type C and D carbonates, and altered the Type B clasts to be elevated in Mn and host a clay-rich rim. © 2023 The Authors. Meteoritics & Planetary Science published by Wiley Periodicals LLC on behalf of The Meteoritical Society. Article 2023 10.1111/maps.13993 Meteoritics and Planetary Science 58 University of Arkansa 834 – 854 6 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85159801790&doi=10.1111%2fmaps.13993&partnerID=40&md5=d015aab37a5d37b12929852e8299cd96 Cited by: 1; All Open Access, Hybrid Gold Open Access Nicolas D. Garroni Gordon R. Osinski article Verhagen2023 Article 2023 10.3390/min13030353 Minerals 13 3 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85152396344&doi=10.3390%2fmin13030353&partnerID=40&md5=78ec2df264b41083ea2c422bb305a1dd Cited by: 1; All Open Access, Gold Open Access Christina M. Verhagen Ji-In Jung Sonia M. Tikoo Axel Wittmann David A. Kring Stefanie Brachfeld Laying Wu Dale H. Burns Sean P. S. Gulick article deGraaff2023 Impact events that create complex craters excavate mid- to lower-crustal rocks, offering a unique perspective on the interior composition and internal dynamics of planetary bodies. On the Yucatán Peninsula, Mexico, the surface geology mainly consists of ∼3 km thick sedimentary rocks, with a lack of exposure of crystalline basement in many areas. Consequently, current understanding of the Yucatán subsurface is largely based on impact ejecta and drill cores recovered from the 180–200-km-diameter Chicxulub impact structure. In this study, we present the first apatite and titanite U–Pb ages for pre-impact dacitic, doleritic, and felsitic magmatic dikes preserved in Chicxulub's peak ring sampled during the 2016 IODP-ICDP Expedition 364. Dating yielded two age groups, with Carboniferous dacites (328–318 Ma) and a felsite (330± 9 Ma) overlapping in age with most of the granitoid basement sampled in the Expedition 364 drill core, as well as Jurassic dolerites (169–159 Ma) and a felsite (158 ± 19 Ma) that represent the first in situ sampling of Jurassic-age magmatic intrusions for the Yucatán Peninsula. Further investigation of the Nd, Sr, and Hf isotopic compositions of these pre-impact lithologies and impact melt rocks from the peak ring structure suggest that dolerites generally contributed up to ∼10 vol% of the Chicxulub impact melt rock sampled in the peak ring. This percentage implies that the dolerites comprised a large part of the Yucatán subsurface by volume, representing a hitherto unsampled pervasive Jurassic magmatic phase. We interpret this magmatic phase to be related to the opening of the Gulf of Mexico, representing the first physical sampling of lithologies associated with the southern extension of the opening of the Gulf of Mexico and likely constraining its onset to the Late Middle Jurassic. © 2022 Elsevier B.V. 2023 10.1016/j.lithos.2022.106953 Lithos 436-437 Research Unit: AMGC, Department of Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, Brussels, 1050, Belgium; Laboratoire G-Time, Université Libre de Bruxelles, ULB, Av. F.D. Roosevelt 50, Brussels, 1050, Belgium; Institute for Geophysics & Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78758, United States; Department of Lithospheric Research, University of Vienna, Althanstrasse 14, Vienna, A-1090, Austria; Center for Planetary Systems Habitability, University of Texas at Austin, Austin, TX 78712, United States; Natural History Museum Vienna, Burgring 7, Vienna, A-1010, Austria https://www.scopus.com/inward/record.uri?eid=2-s2.0-85144048390&doi=10.1016%2fj.lithos.2022.106953&partnerID=40&md5=bfb7cf67afebeed12f538bf2ec24382f cited By 0 S.J. Graaff C.H. Ross J.-G. Feignon P. Kaskes S.P.S. Gulick S. Goderis T. Déhais V. Debaille L. Ferrière C. Koeberl N. Mattielli D.F. Stockli P. Claeys article deGraaff2022293 This study presents petrographic and geochemical characterization of 46 pre-impact rocks and 32 impactites containing and/ or representing impact melt rock from the peak ring of the Chicxulub impact structure (Yucatán, Mexico). The aims were both to investigate the components that potentially contributed to the impact melt (i.e., the preimpact lithologies) and to better elucidate impact melt rock emplacement at Chicxulub. The impactites presented here are subdivided into two sample groups: the lower impact melt rock-bearing unit, which intrudes the peak ring at different intervals, and the upper impact melt rock unit, which overlies the peak ring. The geochemical characterization of five identified pre-impact lithologies (i.e., granitoid, dolerite, dacite, felsite, and limestone) was able to constrain the bulk geochemical composition of both impactite units. These pre-impact lithologies thus likely represent the main constituent lithologies that were involved in the formation of impact melt rock. In general, the composition of both impactite units can be explained by mixing of the primarily felsic and mafic lithologies, but with varying degrees of carbonate dilution. It is assumed that the two units were initially part of the same impact-produced melt, but discrete processes separated them during crater formation. The lower impact melt rock-bearing unit is interpreted to represent impact melt rock injected into the crystalline basement during the compression/excavation stage of cratering. These impact melt rock layers acted as delamination surfaces within the crystalline basement, accommodating its displacement during peak ring formation. This movement strongly comminuted the impact melt rock layers present in the peak ring structure. The composition of the upper impact melt rock unit was contingent on the entrainment of carbonate components and is interpreted to have stayed at the surface during crater development. Its formation was not finalized until the modification stage, when carbonate material would have reentered the crater. © 2022 Geological Society of Amer. All Rights Reserved. 2022 10.1130/B35795.1 Bulletin of the Geological Society of America 134 293-315 Analytical, Environmental & Geo-Chemistry Research Unit, Department of Chemistry, Vrije Universiteit Brussel, AMGC-WE-VUB, Pleinlaan 2, Brussels, 1050, Belgium; Laboratoire G-Time, Université Libre de Bruxelles, ULB, Avenue F.D. Roosevelt 50, Brussels, 1050, Belgium; Institute for Geophysics & Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78758, United States; Center for Planetary Systems Habitability, University of Texas at Austin, Austin, TX 78712, United States; Department of Lithospheric Research, University of Vienna, Althanstrasse 14, Vienna, A-1090, Austria; Natural History Museum, Burgring 7, Vienna, A-1010, Austria; Department of Earth Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1085, HV, Amsterdam, 1081, Netherlands 1-2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85125720004&doi=10.1130%2fB35795.1&partnerID=40&md5=afc34e8e75b06844aea68c953123480f cited By 10 S.J. Graaff P. Kaskes T. Déhais S. Goderis V. Debaille C.H. Ross S.P.S. Gulick J.-G. Feignon L. Ferrière C. Koeberl J. Smit N. Mattielli P. Claeys article WOS:000781695800001 The extinction of the dinosaurs and around three-quarters of all living species was almost certainly caused by a large asteroid impact 66 million years ago. Seismic data acquired across the impact site in Mexico have provided spectacular images of the approximately 200-kilometre-wide Chicxulub impact structure. In this Review, we show how studying the impact site at Chicxulub has advanced our understanding of formation of large craters and the environmental and palaeontological consequences of this impact. The Chicxulub crater’s asymmetric shape and size suggest an oblique impact and an impact energy of about 1023 joules, information that is important for quantifying the climatic effects of the impact. Several thousand gigatonnes of asteroidal and target material were ejected at velocities exceeding 5 kilometres per second, forming a fast-moving cloud that transported dust, soot and sulfate aerosols around the Earth within hours. These impact ejecta and soot from global wildfires blocked sunlight and caused global cooling, thus explaining the severity and abruptness of the mass extinction. However, it remains uncertain whether this impact winter lasted for many months or for more than a decade. Further combined palaeontological and proxy studies of expanded Cretaceous–Palaeogene transitions should further constrain the climatic response and the precise cause and selectivity of the extinction. © 2022, Springer Nature Limited. Review 2022 10.1038/s43017-022-00283-y NATURE REVIEWS EARTH & ENVIRONMENT 3 338-354 Department of Earth Science and Engineering, Imperial College London, London, United Kingdom; Department of Geosciences, Pennsylvania State University, University Park, PA, United States; Senckenberg Biodiversity and Climate Research Centre, Frankfurt am Main, Germany; Earth System Analysis, Potsdam Institute for Climate Impact Research, Member of the Leibniz Association, Potsdam, Germany; Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Berlin, Germany; Institute of Geological Sciences, Planetary Sciences and Remote Sensing, Freie Universität Berlin, Berlin, Germany 5 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85128065124&doi=10.1038%2fs43017-022-00283-y&partnerID=40&md5=9e926e9d3dc36571643f8a5c616ba5b1 cited By 6 Joanna Morgan Timothy J. Bralower Julia Brugger Kai Wuennemann article Hernández-Terrones2022 The aim of the study is to evaluate fluids circulation through the Chicxulub crater, and to determine the composition of hydrothermal fluids after the impact. Rock-Eval pyrolysis and fluid inclusion micro-thermometry analyses were performed. The technique has been routinely used for about fifteen years and has become a standard tool for hydrocarbon exploration. Rock-Eval pyrolysis reveals the distribution of organic and mineral carbon affected by the impact and later affected by hydrothermal activity. All measured inclusions are primary and were found in basement samples only. Both the fluid inclusions data and Rock-Eval pyrolysis show that composition and temperature of the fluids changed as the fluids migrated though crater rocks. An evolution of temperatures occurs (vertical, horizontal, or both), from the surface and from the center of the crater; this spatial evolution is consistent with model of Abramov and Kring, showing a thermal evolution of temperature with depth in the crater as well as its influence on the hydrothermal system. Post-impact fluid circulation modifies the temperature distribution. © 2022 Elsevier Ltd 2022 10.1016/j.apgeochem.2021.105194 Applied Geochemistry 137 Universidad Del Caribe, L-1, Mz 1, Esq. Fracc. Tabachines SM 78, Cancún, Quintana Roo CP 77528, Mexico; Institut de Physique Du Globe de Strasbourg, UMR [7516 Ou 7517], CNRS-Université, de Strasbourg EOST, 1 Rue Blessig, Strasbourg Cedex, 67084, France; Unidad de Investigación en Ciencias de La Tierra Campus UNAM Juriquilla, A.P. # 15 JuriquillaQro, Mexico; Dept. of Earth Science and Engineering, Imperial College London SW7 2AZUK, United Kingdom; Institute for Geophysics Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78758, United States; Dept. of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78758, United States; Center for Planetary Systems Habitability, University of Texas at Austin, Austin, TX 78712, United States; SM 312, Mza 7, Chipre 5, Resid. Isla Azul, Cancun, Quintana Roo, Mexico; Lunar and Planetary Institute, USRA, Houston, TX 77058, United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-85122938042&doi=10.1016%2fj.apgeochem.2021.105194&partnerID=40&md5=ccdd2a3f41f463634e3e32404aa27eac cited By 0 L. Hernández-Terrones L. Martínez J. Szamotulski E. González-Partida J.V. Morgan C.M. Lowery S.P.S. Gulick M. Rebolledo-Vieyra D. Kring article Feignon202274 Constraining the degree of preservation of a meteoritic signature within an impact structure provides vital insights in the complex pathways and processes that occur during and after an impact cratering event, providing information on the fate of the projectile. The IODP-ICDP Expedition 364 drilling recovered a ∼829 m continuous core (M0077A) of impactites and basement rocks within the ∼200-km diameter Chicxulub impact structure peak ring. No highly siderophile element (HSE) data have been reported for any of the impact melt rocks of this drill core to date. Previous work has shown that most Chicxulub impactites contain less than 0.1% of a chondritic component. Only few impact melt rock samples in previous drill cores recovered from the Chicxulub might contain such a signal. Therefore, we analyzed impact melt rock and suevite samples, as well as pre-impact lithologies of the Chicxulub peak ring, with a focus on the HSE concentrations and Re–Os isotopic compositions. Similar to the concentrations of the other major and trace elements, those of the moderately siderophile elements (Cr, Co, Ni) of impact melt rock samples primarily reflect mixing between a mafic (dolerite) and felsic (granite) components, with the incorporation of carbonate material in the upper impact melt rock unit (from 715.60 to 747.02 meters below seafloor). The HSE concentrations of the impact melt rocks and suevites are generally low (&lt;39 ppt Ir, &lt;96 ppt Os, &lt;149 ppt Pt), comparable to the values of the average upper continental crust, yet three impact melt rock samples exhibit an enrichment in Os (125–410 ppt) and two of them also in Ir (250–324 ppt) by one order of magnitude relative to the other investigated samples. The 187Os/188Os ratios of the impact melt rocks are highly variable, ranging from 0.18 to 2.09, probably reflecting heterogenous target rock contributions to the impact melt rocks. The significant amount of mafic dolerite (mainly ∼20–60% and up to 80–90%), which is less radiogenic (187Os/188Os ratio of 0.17), within the impact melt rocks makes an unambiguous identification of an extraterrestrial admixture challenging. Granite samples have unusually low 187Os/188Os ratios (0.16 on average), while impact melt rocks and suevites broadly follow a mixing trend between upper continental crust and chondritic/mantle material. Only one of the investigated samples of the upper impact melt rock unit could also be interpreted in terms of a highly diluted (∼0.01–0.05%) meteoritic component. Importantly, the impact melt rocks and pre-impact lithologies were affected by post-impact hydrothermal alteration processes, probably remobilizing Re and Os. The mafic contribution, explaining the least radiogenic 187Os/188Os values, is rather likely. The low amount of meteoritic material preserved within impactites of the Chicxulub impact structure may result from a combination of the assumed steeply-inclined trajectory of the Chicxulub impactor (enhanced vaporization, and incorporation of projectile material within the expansion plume), the impact velocity, and the volatile-rich target lithologies. © 2022 The Author(s) 2022 10.1016/j.gca.2022.02.006 Geochimica et Cosmochimica Acta 323 74-101 Department of Lithospheric Research, University of Vienna, Althanstrasse 14, Vienna, A-1090, Austria; Institute for Geology and Mineralogy, University of Cologne, Zülpicher Strasse 49b, Cologne, 50674, Germany; Natural History Museum, Burgring 7, Vienna, 1010, Austria; Research Unit: Analytical, Environmental & Geo-Chemistry, Department of Chemistry, Vrije Universiteit Brussel, AMGC-WE-VUB, Pleinlaan 2, Brussels, 1050, Belgium; Laboratoire G-Time, Université Libre de Bruxelles, Av. F.D. Roosevelt 50, Brussels, 1050, Belgium https://www.scopus.com/inward/record.uri?eid=2-s2.0-85125716964&doi=10.1016%2fj.gca.2022.02.006&partnerID=40&md5=bc1dea5f378ee1172610c64f5dc8a0e0 cited By 2 J.-G. Feignon T. Schulz L. Ferrière S. Goderis S.J. Graaff P. Kaskes T. Déhais P. Claeys C. Koeberl article Déhais2022 This work presents isotopic data for the non-traditional isotope systems Fe, Cu, and Zn on a set of Chicxulub impactites and target lithologies with the aim of better documenting the dynamic processes taking place during hypervelocity impact events, as well as those affecting impact structures during the post-impact phase. The focus lies on material from the recent IODP-ICDP Expedition 364 Hole M0077A drill core obtained from the offshore Chicxulub peak ring. Two ejecta blanket samples from the UNAM 5 and 7 cores were used to compare the crater lithologies with those outside of the impact structure. The datasets of bulk Fe, Cu, and Zn isotope ratios are coupled with petrographic observations and bulk major and trace element compositions to disentangle equilibrium isotope fractionation effects from kinetic processes. The observed Fe and Cu isotopic signatures, with δ56/54Fe ranging from −0.95‰ to 0.58‰ and δ65/63Cu from −0.73‰ to 0.14‰, mostly reflect felsic, mafic, and carbonate target lithology mixing and secondary sulfide mineral formation, the latter associated to the extensive and long-lived (&gt;105 years) hydrothermal system within Chicxulub structure. On the other hand, the stable Zn isotope ratios provide evidence for volatility-governed isotopic fractionation. The heavier Zn isotopic compositions observed for the uppermost part of the impactite sequence and a metamorphic clast (δ66/64Zn of up to 0.80‰ and 0.87‰, respectively) relative to most basement lithologies and impact melt rock units indicate partial vaporization of Zn, comparable to what has been observed for Cretaceous-Paleogene boundary layer sediments around the world, as well as for tektites from various strewn fields. In contrast to previous work, our data indicate that an isotopically light Zn reservoir (δ66/64Zn down to −0.49‰), of which the existence has previously been suggested based on mass balance considerations, may reside within the upper impact melt rock (UIM) unit. This observation is restricted to a few UIM samples only and cannot be extended to other target or impact melt rock units. Light isotopic signatures of moderately volatile elements in tektites and microtektites have previously been linked to (back-)condensation under distinct kinetic regimes. Although some of the signatures observed may have been partially overprinted during post-impact processes, our bulk data confirm impact volatilization and condensation of Zn, which may be even more pronounced at the microscale, with variable degrees of mixing between isotopically distinct reservoirs, not only at proximal to distal ejecta sites, but also within the lithologies associated with the Chicxulub impact crater. © 2022 China University of Geosciences (Beijing) and Peking University 2022 10.1016/j.gsf.2022.101410 Geoscience Frontiers 13 Analytical, Environmental and Geo-Chemistry, Vrije Universiteit Brussel, Brussels, Belgium; Laboratoire G-Time, Université Libre de Bruxelles, Brussels, Belgium; Department of Chemistry, Atomic & Mass Spectrometry, Ghent University, Ghent, Belgium 5 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85131909400&doi=10.1016%2fj.gsf.2022.101410&partnerID=40&md5=a7de8ed71f6bbaf59e490315722ee5de cited By 0 T. Déhais S.M. Chernonozhkin P. Kaskes S.J. Graaff V. Debaille F. Vanhaecke P. Claeys S. Goderis article LeBer2022 A new set of physical property measurements was undertaken on 29 peak-ring samples from the IODP-ICDP Expedition 364. Among the studied lithologies, the dominant one recovered in the peak ring consists of shocked granitoid rocks (19 samples). Porosity measurements with two independent methods (triple weight and 14C-PMMA porosity mapping) concur and bring new observations on the intensity and distribution of fracturing and porosity in these shocked target rocks. Characterization of the porous network is taken a step further with two other independent methods (electrical and permeability measurements). Electrical properties such as the cementation exponent (1.59 &lt; m &lt; 1.87) and the formation factor (21 &lt; F &lt; 103) do not compare with other granites from the published literature; they point at a type of porosity closer to clastic sedimentary rocks than to crystalline rocks. Permeabilities of the granitoid rocks range from 0.1 to 7.1 mD under an effective pressure of ∼10 MPa. Unlike other fresh to deformed and altered granitoid rocks from the literature compared in this study, this permeability appears to be relatively insensitive to increasing stress (up to ∼40 MPa), with implications for the nature of the porous network, again, behaving more like cemented clastic rocks than fractured crystalline rocks. Other analyzed lithologies include suevite and impact melt rocks. Relatively low permeability (10−3 mD) measured in melt-rich facies suggest that, at the matrix scale, these lithologies cutting through more permeable peak-ring granitoid rocks may have been a barrier to fluid flow, with implications for hydrothermal systems. © 2022 The Authors. 2022 10.1029/2021JB023801 Journal of Geophysical Research: Solid Earth 127 Géosciences Montpellier, Université de Montpellier (UMR5243), CNRS, Montpellier, France; Lunar and Planetary Institute, Universities Space Research Association, Houston, TX, United States; Institut de Chimie des Milieux et des Matériaux de Poitiers (IC2MP), Université de Poitiers, Poitiers, France; Department of Chemistry, University of Helsinki, Helsinki, Finland 5 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85134075567&doi=10.1029%2f2021JB023801&partnerID=40&md5=99cc2f0b0feff8d5307192e98b684049 cited By 0 E. Le Ber D. Loggia N. Denchik J. Lofi D.A. Kring P. Sardini M. Siitari-Kauppi P. Pezard G. Olivier IODP-ICDP Expedition 364 Science Party article WOS:000831563400008 Article 2022 10.1016/j.epsl.2022.117589 EARTH AND PLANETARY SCIENCE LETTERS 589 biomarker; C/N/S-stable isotopes; TEX86; primary productivity; paleosalinity; pigments Bettina Schaefer Lorenz Schwark Michael E. Böttcher Vann Smith Marco J. L. Coolen Kliti Grice article Arz2022415 Book chapter 2022 10.1130/2022.2557(20) Special Paper of the Geological Society of America 557 415 – 448 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85143871178&doi=10.1130%2f2022.2557%2820%29&partnerID=40&md5=8f572b09c87918a4626fbc9f52079de2 Cited by: 9 José A. ARZ I. Arenillas J.M. Grajales-Nishimura C.L. Liesa A.R. Soria R. Rojas T. Calmus V. Gilabert article Kaskes2022895 This study presents a new classification of a ~100-m-thick crater suevite sequence in the recent International Ocean Discovery Program (IODP)-International Continental Scientific Drilling Program (ICDP) Expedition 364 Hole M0077A drill core to better understand the formation of suevite on top of the Chicxulub peak ring. We provide an extensive data set for this succession that consists of whole-rock major and trace element compositional data (n = 212) and petrographic data supported by digital image analysis. The suevite sequence is subdivided into three units that are distinct in their petrography, geochemistry, and sedimentology, from base to top: the ~5.6-m-thick non-graded suevite unit, the ~89-m-thick graded suevite unit, and the ~3.5-m-thick bedded suevite unit. All of these suevite units have isolated Cretaceous planktic foraminifera within their clastic groundmass, which suggests that marine processes were responsible for the deposition of the entire M0077A suevite sequence. The most likely scenario describes that the first ocean water that reached the northern peak ring region entered through a N-NE gap in the Chicxulub outer rim. We estimate that this ocean water arrived at Site M0077 within 30 minutes after the impact and was relatively poor in rock debris. This water caused intense quench fragmentation when it interacted with the underlying hot impact melt rock, and this resulted in the emplacement of the ~5.6-m-thick hyaloclastite-like, non-graded suevite unit. In the following hours, the impact structure was flooded by an ocean resurge rich in rock debris, which caused the phreatomagmatic processes to stop and the ~89-m-thick graded suevite unit to be deposited. We interpret that after the energy of the resurge slowly dissipated, oscillating seiche waves took over the sedimentary regime and formed the ~3.5-m-thick bedded suevite unit. The final stages of the formation of the impactite sequence (estimated to be <20 years after impact) were dominated by resuspension and slow atmospheric settling, including the final deposition of Chicxulub impactor debris. Cumulatively, the Site M0077 suevite sequence from the Chicxulub impact site preserved a high-resolution record that provides an unprecedented window for unravelling the dynamics and timing of proximal marine cratering processes in the direct aftermath of a large impact event. © 2021 The Authors. Gold Open Access 2022 10.1130/B36020.1 Bulletin of the Geological Society of America 134 895-927 Research Unit: Analytical, Environmental & Geo-Chemistry, Department of Chemistry, Vrije Universiteit Brussel, AMGC-WE-VUB, Pleinlaan 2, Brussels, 1050, Belgium; Laboratoire G-Time, Université Libre de Bruxelles, ULB, Av. F.D. Roosevelt 50, Brussels, 1050, Belgium; Department of Lithospheric Research, University of Vienna, Althanstrasse 14, Vienna, A-1090, Austria; Natural History Museum, Burgring 7, Vienna, A-1010, Austria; Department of Earth Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1085, Amsterdam, 1081 HV, Netherlands; Eyring Materials Center, Arizona State University, Tempe, AZ 85287, United States; Institute for Geophysics & Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78758, United States; Center for Planetary Systems Habitability, University of Texas at Austin, Austin, TX 78712, United States 3-4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85113288682&doi=10.1130%2fB36020.1&partnerID=40&md5=77a53069f3320d8fecfb282dbd3ce529 cited By 11 P. Kaskes S.J. Graaff J.-G. Feignon T. Déhais S. Goderis L. Ferrière C. Koeberl J. Smit A. Wittmann S.P.S. Gulick V. Debaille N. Mattielli P. Claeys article Rodríguez-Tovar2022 To fully assess the resilience and recovery of life in response to the Cretaceous-Paleogene (K-Pg) boundary mass extinction ~ 66 million years ago, it is paramount to understand biodiversity prior to the Chicxulub impact event. The peak ring of the Chicxulub impact structure offshore the Yucatán Peninsula (México) was recently drilled and extracted a ~ 100 m thick impact-generated, melt-bearing, polymict breccia (crater suevite), which preserved carbonate clasts with common biogenic structures. We pieced this information to reproduce for the first time the macrobenthic tracemaker community and marine paleoenvironment prior to a large impact event at the crater area by combining paleoichnology with micropaleontology. A variable macrobenthic tracemaker community was present prior to the impact (Cenomanian–Maastrichtian), which included soft bodied organisms such as annelids, crustaceans and bivalves, mainly colonizing softgrounds in marine oxygenated, nutrient rich, conditions. Trace fossil assemblage from these upper Cretaceous core lithologies, with dominant Planolites and frequent Chondrites, corresponds well with that in the overlying post-impact Paleogene sediments. This reveals that the K-Pg impact event had no significant effects (i.e., extinction) on the composition of the macroinvertebrate tracemaker community in the Chicxulub region. © 2022, The Author(s). 2022 10.1038/s41598-022-15566-z Scientific Reports 12 Departamento de Estratigrafía y Paleontología, Universidad de Granada, Granada, Spain; Research Unit: Analytical, Environmental and Geo-Chemistry, Department of Chemistry, Vrije Universiteit Brussel, AMGC-WE-VUB, Pleinlaan 2, Brussels, 1050, Belgium; Laboratoire G-Time, Université Libre de Bruxelles, Av. F.D. Roosevelt 50, Brussels, 1050, Belgium; Centro de Astrobiologia CSIC-INTA, Torrejon de Ardoz, Spain; Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, United States; Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, United States; Center for Planetary Systems Habitability, University of Texas at Austin, Austin, United States; Department of Geosciences, University of Alaska Fairbanks, Fairbanks, AK, United States; Department of Geosciences, The Pennsylvania State University, College town, United States; Faculty of Sciences (FALW), Vrije Universiteit Amsterdam, Amsterdam, Netherlands; Department of Geosciences, Auburn University, Auburn, AL, United States 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85133415149&doi=10.1038%2fs41598-022-15566-z&partnerID=40&md5=47c7880c77a3fe31a9f2153bf9693c3e cited By 0 F.J. Rodríguez-Tovar P. Kaskes J. Ormö S.P.S. Gulick M.T. Whalen H.L. Jones C.M. Lowery T.J. Bralower J. Smit Jr. King S. Goderis P. Claeys article García-Garnica202299 Based on geochemical and magnetic susceptibility analyses, maximum warming events (hyperthermal) in the Palaeogene are recognized in the carbonate rocks of the Santa Elena borehole (SEB) in the Yucatan Peninsula, the Palaeocene-Eocene Thermal Maximum (PETM) and the Eocene Thermal Maximum 2 (ETM-2). The site records the continental shelf marine response during these global events. Major and trace element records (Al, Ba, Ca, Fe, K, Si, and Ti), Ca/Fe, Si/Al ratios, and magnetic susceptibility are used as proxies of terrigenous input, and Ba/Al ratio as a proxy of palaeoproductivity. The hyperthermal events are characterized by the dilution and/or dissolution of biogenic carbonates. The high input of terrigenous materials is linked to extreme precipitation, common during these warming events. Our records suggest a decrease in palaeoproductivity associated with a nutrients gradient in a shallow ecosystem, with deeper thermocline and stratified column water. The PETM is characterized by high eustatic sea-level conditions, with a high contribution of detrital material, indicating sedimentary condensation and marked increase in precipitation, calcite dilution and/or dissolution, and low productivity. The ETM-2 event is less extreme than the PETM, with high precipitation, although evaporation could also play an important role, as evidenced by the presence of evaporites in this interval. These changes might affect the higher trophic levels of the shelf sea ecosystem, declining productivity. The study contributes to our understanding of the global and regional effects of these past warming events and the future climate change. © 2021 John Wiley & Sons Ltd. 2022 10.1002/gj.4285 Geological Journal 57 99-113 Posgrado en Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Ciudad de México, Mexico; Instituto de Geofísica, Universidad Nacional Autónoma de México, Ciudad de México, Mexico; Instituto de Investigación Científica y Estudios Avanzados Chicxulub, Mérida, Mexico 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85116842306&doi=10.1002%2fgj.4285&partnerID=40&md5=031388feb5ee04bfe541298f8b1a3afb cited By 0 E.M. García-Garnica L. Pérez-Cruz article Ross2022241 Determining the nature and age of the 200-km-wide Chicxulub impact target rock is an essential step in advancing our understanding of the Maya Block basement. Few age constraints exist for the northern Maya Block crust, specifically the basement underlying the 66 Ma, 200 km-wide Chicxulub impact structure. The International Ocean Discovery Program-International Continental Scientific Drilling Program Expedition 364 core recovered a continuous section of basement rocks from the Chicxulub target rocks, which provides a unique opportunity to illuminate the pre-impact tectonic evolution of a terrane key to the development of the Gulf of Mexico. Sparse published ages for the Maya Block point to Mesoproterozoic, Ediacaran, Ordovician to Devonian crust are consistent with plate reconstruction models. In con- trast, granitic basement recovered from the Chicxulub peak ring during Expedition 364 yielded new zircon U-Pb laser ablation-in-ductively coupled plasma-mass spectrometry (LA-ICP-MS) concordant dates clustering around 334 ± 2.3 Ma. Zircon rare earth element (REE) chemistry is consistent with the granitoids having formed in a continental arc setting. Inherited zircon grains fall into three groups: 400-435 Ma, 500-635 Ma, and 940-1400 Ma, which are consistent with the incorporation of Peri-Gondwanan, PanAfrican, and Grenvillian crust, respectively. Carboniferous U-Pb ages, trace element compositions, and inherited zircon grains indicate a pre-collisional continental volcanic arc located along the Maya Block’s northern margin before NW Gondwana collided with Laurentia. The existence of a continental arc along NW Gondwana suggests southward-directed subduction of Rheic oceanic crust beneath the Maya Block and is similar to evidence for a continental arc along the northern margin of Gondwana that is documented in the Suwannee terrane, Florida, USA, and Coahuila Block of NE México. © 2022 Geological Society of America. All Rights Reserved. 2022 10.1130/B35831.1 Bulletin of the Geological Society of America 134 241-260 Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, 22275 Speedway Stop C9000, Austin, TX 78712, United States; Institute for Geophysics, J.J. Pickle Research Campus, Building ROC, University of Texas at Austin, 10100 Burnet Road (R2200), Austin, TX 78758, United States; Center for Planetary Systems Habitability, University of Texas at Austin, Austin, TX 78712, United States; Analytical, Environmental and Geo-Chemistry, Department of Chemistry, Vrije Universiteit Brussel, AMGC-WE-VUB, Pleinlaan 2, Brussels, 1050, Belgium; Laboratoire G-Time, Université Libre de Bruxelles, Av. F.D. Roosevelt 50, Brussels, 1050, Belgium; State Key Laboratory of Geological Processes and Mineral Resources, Planetary Science Institute, School of Earth Sciences, China University of Geosciences, Wuhan, China; State Key Laboratory of Space Science Institute, Lunar and Planetary Science, Macau University of Science and Technology, Macau, Taipa, Macau; School of Geographical and Earth Sciences, University of Glasgow, Glasgow, G12 8QQ, United Kingdom; NERC Argon Isotope Facility, Scottish Universities Environmental Research Centre (SUERC), Glasgow, United Kingdom; Center for Lunar Science and Exploration, Lunar and Planetary Institute, Houston, TX 77058, United States; Eyring Materials Center, Arizona State University, Tempe, AZ 85281, United States; Department of Earth Science and Engineering, Imperial College London, London, SW7 2AZ, United Kingdom 1-2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85109154731&doi=10.1130%2fB35831.1&partnerID=40&md5=0baa371434419788c182b46335e2c16d cited By 9 C.H. Ross D.F. Stockli C. Rasmussen S.P.S. Gulick S.J. Graaff P. Claeys J. Zhao L. Xiao A.E. Pickersgill M. Schmieder D.A. Kring A. Wittmann J.V. Morgan article Huber2022 The timescale of the modification stage of basin-sized impact structures is not well understood. Owing to ca. 10 km of erosion since its formation, the Vredefort impact structure, South Africa, is an ideal testing ground for deciphering post-impact modification. Here, we present geophysical and geochemical evidence from the Vredefort Granophyre Dikes, which were derived from the - now eroded - Vredefort impact melt sheet. The dikes have been studied mostly in terms of their composition, while the timing and duration of their emplacement remain controversial. We examined the modern depth extent of five dikes, with three from the inner crystalline core of the central uplift, and two from the boundary between the core and the supracrustal collar of the central uplift, using two-dimensional electrical resistivity tomography. We found that the core dikes terminate near the present erosion surface (i.e., &lt;5 m depth). In contrast, the dikes at the core-collar boundary extend to a depth ≥ 9 m. These observations suggest that the core dikes are exposed near their lowermost terminus. In addition, we obtained bulk geochemical composition of the dikes, finding that the andesitic composition phase is present in the core-collar dikes that is not found in the core dikes. The presence of this phase indicates the episodic emplacement of impact melt into subvertical crater floor fractures. We conclude that the dike formation was protracted and occurred over a time span of at least 104 years. The sequential formation of the Vredefort Granophyre Dikes points to horizontal extension of crust below the impact melt sheet above a kinematic velocity discontinuity, a crustal instability resulting from the dynamic collapse of the transient cavity. © 2021 Elsevier Inc. 2022 10.1016/j.icarus.2021.114812 Icarus 374 Department of Earth Sciences, University of the Western Cape, Robert Sobukwe Road, Bellville, 7535, South Africa; Department of Geology, University of the Free State, 205 Nelson Mandela Drive, Bloemfontein, 9300, South Africa; Institut für Geologie, Universität Hamburg, Bundesstraße 55, Hamburg, 20146, Germany; Institute for Groundwater Studies, University of the Free State, 205 Nelson Mandela Drive, Bloemfontein, 9300, South Africa https://www.scopus.com/inward/record.uri?eid=2-s2.0-85119893631&doi=10.1016%2fj.icarus.2021.114812&partnerID=40&md5=156a5e1c7822afa57711526f9dd50ca9 cited By 1 M.S. Huber E. Kovaleva M.D. Clark U. Riller F.D. Fourie article Davison2022 Almost all meteorite impacts occur at oblique incidence angles, but the effect of impact angle on crater size is not well understood, especially for large craters. To improve oblique impact crater scaling, we present a suite of simulations of complex crater formation on Earth and the Moon over a range of impact angles, velocities and impactor sizes. We show that crater diameter is larger than predicted by existing scaling relationships for oblique impacts; there is little dependence on obliquity for impacts steeper than 45° from the horizontal. Crater depth, volume and diameter depend on impact angle in different ways—relatively shallower craters are formed by more oblique impacts. Our simulation results have implications for how crater populations are determined from impactor populations and vice-versa. They suggest that existing approaches to account for impact obliquity may underestimate the number of complex craters larger than a given size by as much as one-third. © 2022. The Authors. 2022 10.1029/2022GL101117 Geophysical Research Letters 49 Department of Earth Science and Engineering, Impacts & Astromaterials Research Centre, Imperial College London, London, United Kingdom 21 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85141934192&doi=10.1029%2f2022GL101117&partnerID=40&md5=362a3e22f57c5a248ed8538f88e698be cited By 0 T.M. Davison G.S. Collins article Urrutia-Fucugauchi20222735 Modeling gravity and magnetic anomalies over the Chicxulub crater are used to constrain the structure, stratigraphy, and asymmetries. Chicxulub is a multiring ~ 200 km rim diameter structure with a central uplift and well-preserved peak ring. The low relief terrain and physical property contrasts have facilitated geophysical modeling of the structure and impactite deposits. Nevertheless, contrasting models have been obtained due to data resolution limitations, uneven coverage, non-uniqueness solutions, boundary conditions, and heterogeneous/anisotropic media. We employ a multi-technique approach based on regional–residual separation, spectral analysis, first and second derivatives, upward and downward analytical continuations, horizontal gradients, analytical signal, Euler deconvolution, reduction to the pole, and forward modeling to constraint the anomaly sources, geometry and depths. Forward modeling of gravity anomaly favors central uplift flat-top models, whereas magnetic models show irregular shapes with a peak towards the NE, at 4–5 km depth. Analysis shows the effects of intersecting regional anomalies in the semicircular pattern that limit the definition of asymmetries, which constrains impact angle and trajectory, crater structure and pre-existing target features. Models link lateral–vertical density and magnetic property contrasts, distinguishing non-magnetic pre-and post-impact carbonates and carbonate-rich breccias from melt and basement rich breccias, and displaced, fractured impactites and basement uplift. © 2022, The Author(s), under exclusive licence to Springer Nature Switzerland AG. 2022 10.1007/s00024-022-03074-0 Pure and Applied Geophysics 179 2735-2756 Programa Universitario de Perforaciones en Océanos y Continentes, Instituto de Geofísica, Universidad Nacional Autónoma de México, Ciudad Universitaria, Mexico City, 04510, Mexico; Instituto de Investigación Científica y Estudios Avanzados Chicxulub, Parque Científico y Tecnológico de Yucatán, Sierra Papacal, Yucatán, Merida, 97302, Mexico; Grupo KB de Mexico SA de CV, Av. Rio Mixocac 66-101, Colonia del Valle, Mexico City, 03100, Mexico; Coordinación de Plataformas Oceanográficas, Coordinación de la Investigación Científica, Universidad Nacional Autónoma de México, Ciudad Universitaria, Mexico City, 04510, Mexico 8 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85131535563&doi=10.1007%2fs00024-022-03074-0&partnerID=40&md5=7d22a5ca14f23c2a27150a03272833ed cited By 0 J. Urrutia-Fucugauchi O. Arellano-Catalán L. Pérez-Cruz I.A. Romero-Galindo article Nixon2022 We conducted a vertical seismic profile (VSP) in the borehole of International Ocean Discovery Program/International Continental Scientific Drilling Program Expedition 364 Site M0077 to better understand the nature of the seismic reflectivity and the in situ seismic properties associated with the Chicxulub impact structure peak ring. Extraction of the up-going wavefield from the VSP shows that a strong seismic reflection event imaged in seismic reflection data results from discontinuities in the elastic impedance Z (the product of density and wave speed) at the top and bottom of a zone of hydrothermally altered melt-bearing polymict breccia (suevite) that are characterized by anomalously low Z. Below this strong carbonate/suevite reflection event, the upgoing seismic wavefield is chaotic, indicating high levels of scattering from the suevites and underlying melt rocks and shocked granitoids of the peak ring, in contrast to the clear coherent reflections throughout the overlying Cenozoic sediments. We extract shear wave speeds, which, together with those provided from the complementary sonic log and densities from core scanning, allowed determination of VP/VS and Poisson's ratio v. These values are anomalously high relative to comparable terrestrial lithologies. We also calculate a variety of damage parameters for the disrupted peak ring granitoids. These values may assist in linking seismic observations to shock levels that are necessary to calibrate current impact models and may also be useful in assessing levels of fracturing within major fault zones. © 2022. The Authors. 2022 10.1029/2021GC009959 Geochemistry, Geophysics, Geosystems 23 Department of Physics, University of Alberta, Edmonton, AB, Canada; Department of Earth, Atmospheric and Planetary Science, Purdue University, West Lafayette, IN, United States; Géosciences Montpellier, Université de Montpellier, Montpellier, France; Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, TX, United States; Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, TX, United States; Center for Planetary Systems Habitability, University of Texas at Austin, Austin, TX, United States; Lunar and Planetary Institute, Houston, TX, United States 3 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85127271273&doi=10.1029%2f2021GC009959&partnerID=40&md5=89bbbebeffbdfb758c298d435ddc4461 cited By 0 C.G. Nixon R. Kofman J. Lofi S.P.S. Gulick S. Saustrup G.L. Christeson D.A. Kring article Simpson2022 The peak-ring of the 66 Ma, ~180 km Chicxulub impact structure in the northern Yucatán peninsula and southern Gulf of Mexico was sampled during the International Ocean Discovery Program and International Continental Scientific Drilling Program (IODP–ICDP) Expedition 364 at Site M0077 (21.45° N, 89.95° W). Secondary clay minerals are pervasive throughout the upper peak-ring lithologies as a product of ubiquitous altered glass present throughout the impact melt and melt-bearing breccia sequence. Here we present the first detailed study of the clay mineralogy (microprobe, pXRD, spectral reflectance from 350 to 2500 nm) and isotope geochemistry (δ2H and δ18O) of the &lt;0.2 μm size-fraction from upper peak-ring lithologies. The clay mineralogy is dominated by smectitic clay minerals, whose composition varies with stratigraphic position. Trioctahedral Mg[sbnd]Fe smectite (var. saponite) is most common in Units or Subunits 2A, 2C, 3 and 4, while a section of Subunit 2B contains a more dioctahedral, Al-rich smectite. Higher porosity regions of the lower to mid, dioctahedral smectite-dominated intervals have higher δ18O (+14.2 to +18.6‰) whereas intervals dominated by trioctahedral smectite have lower δ18O (+10.4 to +14.1‰). The range of smectite δ2H (−105 to −87‰), in comparison to that of oxygen isotopes, is proportionally much less variable and unrelated to smectite mineralogy. When combined, the oxygen and hydrogen isotope compositions of the smectitic clay minerals suggest low temperature (~20 to 50 °C) formation from meteoric water-dominated fluids. The lower end of this temperature range is below current ambient conditions, which conceivably could suggest smectite formation before much of the overlying sedimentary rocks were deposited (~56 Ma?). Calculated temperatures are generally lower than those associated with impact-generated hydrothermal alteration. Calculated δ18O and δ2H of meteoric water-dominated fluids associated with low-temperature formation of these clay minerals are lower than known for modern meteoric water in the Yucatán region. The simplest explanation for the source of these ancient fluids is meteoric water-dominated Gulf Coast brines. A more remote possibility is orogenically-driven, long-distance transport of groundwater from highlands to the east via an artesian aquifer formed in part by fractured Mesozoic rocks extending laterally beneath the impact structure. © 2021 Elsevier B.V. 2022 10.1016/j.chemgeo.2021.120639 Chemical Geology 588 Department of Earth Sciences, The University of Western OntarioON N6A 3K7, Canada; Institute for Earth and Space Exploration, The University of Western OntarioON N6A 3K7, Canada; NASA Johnson Space Center, Universities Space Research Association, Houston, TX 77058, United States; Lunar and Planetary Institute, Universities Space Research Association, Houston, TX 77058, United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-85120414325&doi=10.1016%2fj.chemgeo.2021.120639&partnerID=40&md5=c3858c4e22d05a57283419069c66fa46 cited By 0 S.L. Simpson F.J. Longstaffe G.R. Osinski C.M. Caudill D.A. Kring article Kring2021103 Target lithologies and post-impact hydrothermal mineral assemblages in a new 1.3 km deep core from the peak ring of the Chicxulub impact crater indicate sulfate reduction was a potential energy source for a microbial ecosystem (Kring et al., 2020). That sulfate was metabolized is confirmed here by microscopic pyrite framboids with δ34S values of -5 to -35 ‰ and ΔSsulfate-sulfide values between pyrite and source sulfate of 25 to 54 ‰, which are indicative of biologic fractionation rather than inorganic fractionation processes. These data indicate the Chicxulub impact crater and its hydrothermal system hosted a subsurface microbial community in porous permeable niches within the crater's peak ring. © David A. Kring et al., 2021; Published by Mary Ann Liebert, Inc. 2021. 2021 10.1089/ast.2020.2286 Astrobiology 21 103-114 Lunar and Planetary Institute, Universities Space Research Association, 3600 Bay Area Blvd., Houston, TX 77058-1113, United States; Department of Geosciences, Swedish Museum of Natural History, Stockholm, Sweden; HNU-Neu-Ulm University of Applied Sciences, Neu-Ulm, Germany 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85099136093&doi=10.1089%2fast.2020.2286&partnerID=40&md5=8ab6220dd61a88923bebc3afc69cd434 cited By 10 D.A. Kring M.J. Whitehouse M. Schmieder article Zhao2021755 Large impact structures with peak rings are common landforms across the solar system, and their formation has implications for both the interior structure and thermal evolution of planetary bodies. Numerical modeling and structural studies have been used to simulate and ground truth peak-ring formative mechanisms, but the shock metamorphic record of minerals within these structures remains to be ascertained. We investigated impact-related microstructures and high-pressure phases in zircon from melt-bearing breccias, impact melt rock, and granitoid basement from the Chicxulub peak ring (Yucatán Peninsula, Mexico), sampled by the International Ocean Discovery Program (IODP)/International Continental Drilling Project (IODP-ICDP) Expedition 364 Hole M0077A. Zircon grains exhibit shock features such as reidite, zircon twins, and granular zircon including “former reidite in granular neoblastic” (FRIGN) zircon. These features record an initial high-pressure shock wave (>30 GPa), subsequent relaxation during the passage of the rarefaction wave, and a final heating and annealing stage. Our observed grain-scale deformation history agrees well with the stress fields predicted by the dynamic collapse model, as the central uplift collapsed downward-then-outward to form the peak ring. The occurrence of reidite in a large impact basin on Earth represents the first such discovery, preserved due to its separation from impact melt and rapid cooling by the resurging ocean. The coexistence of reidite and FRIGN zircon within the impact melt–bearing breccias indicates that cooling by seawater was heterogeneous. Our results provide valuablen information on when different shock microstructures form and how they are modified according to their position in the impact structure, and this study further improves on the use of shock barometry as a diagnostic tool in understanding the cratering process. © 2021 Geological Society of America. For permission to copy, contact editing@geosociety.org. 2021 10.1130/G48278.1 Geology 49 755-760 State Key Laboratory of Geological Processes and Mineral Resources, Planetary Science Institute, School of Earth Sciences, China University of Geosciences, Wuhan, 430074, China; Chinese Academy of Sciences Center for Excellence in Comparative Planetology, Hefei, 230026, China; Planetary Environmental and Astrobiological Research Laboratory, School of Atmospheric Sciences, Sun Yat-sen University, Zhuhai, 519082, China; Department of Earth Science and Engineering, Imperial College London, London, SW7 2BP, United Kingdom; Department of Earth Sciences, University of Western Ontario, London, ON N6A 5B7, Canada; Institute for Earth and Space Exploration, University of Western Ontario, London, ON N6A 5B7, Canada; Department of Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame, Indiana 46556, United States; Institute for Geophysics & Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, Texas 78758-4445, United States; Center for Planetary Systems Habitability, University of Texas at Austin, Austin, Texas 78758-4445, United States; Institut für Geologie, Universität Hamburg, Hamburg, 20146, Germany; Analytical, Environmental and Geo-Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, Brussels, 1050, Belgium; Centre for Earth Evolution and Dynamics, University of Oslo, Oslo, NO-0315, Norway; Department of Applied Geology, The Institute for Geoscience Research, Curtin University, GPO Box U1987, Perth, WA 6845, Australia; State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau, China 7 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85109462138&doi=10.1130%2fG48278.1&partnerID=40&md5=9d9c6422882283b5b86ceac0e685d77c cited By 5 J. Zhao L. Xiao Z. Xiao J.V. Morgan G.R. Osinski C.R. Neal S.P.S. Gulick U. Riller P. Claeys S. Zhao N.C. Prieur A. Nemchin S. Yu article Wittmann2021 Zircon is a precise chronometer and prominent recorder of impact deformation. However, many impact-induced features in zircon are poorly calibrated, sometimes due to contradicting experimental data, in other instances due to the lack of systematic studies of impact-deformed zircon. To resolve issues with the shock petrographic use of zircon, we classified impact deformation features in 429 zircon grains in a continuous drill core of uplifted, granitic bedrock in the peak ring of the 200-km-diameter K-Pg Chicxulub impact structure. Following initial identification in backscattered electron (BSE) images, Raman spectroscopy and electron backscatter diffraction confirmed one reidite-bearing zircon grain. Quartz-based shock barometry indicates the host rock of this zircon-reidite grain experienced an average shock pressure of 17.5 GPa. A survey of BSE images of 429 ZrSiO4 grains found brittle deformation features are ubiquitous, with planar fractures in one to five sets occurring in 23% of all zircon grains. Our survey also reveals a statistically significant correlation of the occurrence of planar fractures in zircon with the types of host materials. Compared to zircon enclosed in mafic, higher density mineral hosts, felsic, low-density minerals show a much higher incidence of zircon with planar fractures. This finding suggests amplification of pressure due to shock impedance contrasts between zircon and its mineral hosts. Using the impedance matching method, we modeled the shock impedance pressure amplification effect for zircon inclusions in Chicxulub granitic hosts. Our modeling indicates shock impedance could have amplified the average 17.5 GPa shock pressure in a zircon inclusion in quartz or feldspar in the Chicxulub granitic rocks to 24 ± 1 GPa, suggesting that reidite in these rocks formed between 17.5 and 25 GPa. In essence, our study of impedance-induced shock pressure amplification in zircon assemblages, including the onset of reidite formation, details how shock impedance in mineral associations can be quantified to refine shock pressure estimates. © 2021 The Author(s) 2021 10.1016/j.epsl.2021.117201 Earth and Planetary Science Letters 575 Eyring Materials Center, Arizona State University, 1001 S. McAllister Avenue, Tempe, AZ 85287-8301, United States; Space Science and Technology Centre, School of Earth and Planetary Sciences, Curtin University, GPO Box U1987, Perth, Western Australia 6845, Australia; Natural History Museum, Burgring 7, Vienna, 1010, Austria; Institute of Earth and Environmental Sciences - Geology, Albert-Ludwigs Universität Freiburg, Freiburg, Germany; Department of Earth Sciences, University of Cambridge, Cambridge, UK, United Kingdom; Institute for Geophysics, Jackson School of Geosciences, University of Texas at AustinTX 78758-4445, United States; Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, 22275 Speedway Stop C9000, Austin, TX 78712, United States; HNU Neu-Ulm University of Applied Sciences, Neu-Ulm, Germany; Lunar and Planetary Institute, Houston, TX, United States; State Key Laboratory of Geological Processes and Mineral Resources, Planetary Science Institute, School of Earth Sciences, China University of Geosciences, Wuhan, China; Chinese Academy of Sciences, Center for Excellence in Comparative Planetology, Hefei, 230026, China; Department of Earth Science and Engineering, Imperial College LondonUK, United Kingdom; Center for Planetary Systems Habitability, University of Texas at Austin, Austin, TX, United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-85115630556&doi=10.1016%2fj.epsl.2021.117201&partnerID=40&md5=3e515abbaab9310683e401769afc64be cited By 5 A. Wittmann A.J. Cavosie N.E. Timms L. Ferrière A. Rae C. Rasmussen C. Ross D. Stockli M. Schmieder D.A. Kring J. Zhao L. Xiao J.V. Morgan S.P.S. Gulick IODP-ICDP Expedition 364 Scientists article Cockell2021 We report on the effect of the end-Cretaceous impact event on the present-day deep microbial biosphere at the impact site. IODP-ICDP Expedition 364 drilled into the peak ring of the Chicxulub crater, México, allowing us to investigate the microbial communities within this structure. Increased cell biomass was found in the impact suevite, which was deposited within the first few hours of the Cenozoic, demonstrating that the impact produced a new lithological horizon that caused a long-term improvement in deep subsurface colonization potential. In the biologically impoverished granitic rocks, we observed increased cell abundances at impact-induced geological interfaces, that can be attributed to the nutritionally diverse substrates and/or elevated fluid flow. 16S rRNA gene amplicon sequencing revealed taxonomically distinct microbial communities in each crater lithology. These observations show that the impact caused geological deformation that continues to shape the deep subsurface biosphere at Chicxulub in the present day. © Copyright © 2021 Cockell, Schaefer, Wuchter, Coolen, Grice, Schnieders, Morgan, Gulick, Wittmann, Lofi, Christeson, Kring, Whalen, Bralower, Osinski, Claeys, Kaskes, de Graaff, Déhais, Goderis, Hernandez Becerra, Nixon and IODP-ICDP Expedition 364 Scientists. 2021 10.3389/fmicb.2021.668240 Frontiers in Microbiology 12 UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom; WA-Organic and Isotope Geochemistry Centre (WA-OIGC), School of Earth and Planetary Sciences, The Institute for Geoscience Research, Curtin University, Bentley, WA, Australia; MARUM-Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany; Department of Earth Science and Engineering, Imperial College London, London, United Kingdom; Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, TX, United States; Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, TX, United States; Center for Planetary Systems Habitability, University of Texas at Austin, Austin, TX, United States; Arizona State University, Eyring Materials Center, Tempe, AZ, United States; Géosciences Montpellier, Université de Montpellier, CNRS, Montpellier, France; Lunar and Planetary Institute, Houston, TX, United States; Department of Geosciences, University of Alaska Fairbanks, Fairbanks, AK, United States; Department of Geosciences, Pennsylvania State University, University Park, PA, United States; Institute for Earth and Space Exploration and Department of Earth Sciences, University of Western Ontario, London, ON, Canada; Environmental and Geo-Chemistry, Vrije Universiteit Brussel, Brussels, Belgium; Department of Earth and Environmental Sciences, University of Manchester, Manchester, IN, United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-85109762410&doi=10.3389%2ffmicb.2021.668240&partnerID=40&md5=ab7628f5005cc36ae73afb10c6612615 cited By 4 C.S. Cockell B. Schaefer C. Wuchter M.J.L. Coolen K. Grice L. Schnieders J.V. Morgan S.P.S. Gulick A. Wittmann J. Lofi G.L. Christeson D.A. Kring M.T. Whalen T.J. Bralower G.R. Osinski P. Claeys P. Kaskes S.J. Graaff T. Déhais S. Goderis N. Hernandez Becerra S. Nixon IODP-ICDP Expedition 364 Scientists article Guzmán-Hidalgo2021 Fifty-four 2D seismic profiles and 13 boreholes were used to describe pre-impact and post-impact deposits in the Yucatán Shelf. Previous work has identified a pre-impact basin in the northwest portion of the Chicxulub structure. The geometry of seismic reflectors associated with the Mesozoic Era shows that this pre-impact depression, here named Yucatán Trough, extends from the southern part of the Yucatán Peninsula to the northern face of the Campeche Escarpment. Stratigraphic data from boreholes of the Yucatán Platform suggest that the main sedimentary fills of the Yucatán Trough are a thin series of Upper Jurassic-Lower Cretaceous red beds, followed by the evaporite-dominated Lower Cretaceous and the carbonate-dominated Upper Cretaceous sedimentary successions. Mapping of the Cretaceous-Paleogene (K/Pg) deposits allowed us to observe the morphology of the Yucatán Shelf by the time of the Chicxulub impact event. The two-way seismic time K/Pg deposits map in conjunction with the free-air gravity anomaly map of the northern Yucatán Block reveals that, before the impact, the carbonate platform was divided into two blocks by a ~ 95–205 km wide and ~ 470-km long trough-shaped depression, probably a rift-basin with a north-south orientation, in which the central structure of Chicxulub impact crater is contained. The seismic reflectors overlying the top of the K/Pg deposits show that, during the Cenozoic Era, both the Yucatán Trough and impact basin were filled by progradational sequences which flattened the surface completely until the current block of the Yucatán Platform was configured. © 2021 Elsevier B.V. 2021 10.1016/j.margeo.2021.106594 Marine Geology 441 Posgrado en Ciencias de la Tierra, Instituto de Geología, Universidad Nacional Autónoma de México, Cd. Universitaria, Coyoacán, Ciudad de México, C. P. 04510, Mexico; Seminario Universitario sobre Investigación en Hidrocarburos and Instituto de Geología, Universidad Nacional Autónoma de México, Cd. Universitaria, Coyoacán, Ciudad de México, C. P. 04510, Mexico; Rosenstiel School of Marine and Atmospheric Science, University of Miami, Florida, 33149-1031, United States; Facultad de Ingeniería, Universidad Nacional Autónoma de México, Cd. Universitaria, Coyoacán, Ciudad de México, C. P. 04510, Mexico; Instituto de Geofísica, Universidad Nacional Autónoma de México, Cd. Universitaria, Coyoacán, Ciudad de México, C. P. 04510, Mexico https://www.scopus.com/inward/record.uri?eid=2-s2.0-85113350278&doi=10.1016%2fj.margeo.2021.106594&partnerID=40&md5=9e93bd277f736f7f90aaf77b6dbd9064 cited By 0 E. Guzmán-Hidalgo J.M. Grajales-Nishimura G.P. Eberli J.E. Aguayo-Camargo J. Urrutia-Fucugauchi L. Pérez-Cruz article Salge2021207 A combined petrographic and chemical study of ejecta particles from the Cretaceous- Paleogene boundary sequence of El Guayal, Tabasco, Mexico (520 km SW of Chicxulub crater), was carried out to assess their formation conditions and genetic relation during the impact process. The reaction of silicate ejecta particles with hot volatiles during atmospheric transport may have induced alteration processes, e.g., silicification and cementation, observed in the ejecta deposits. The various microstructures of calcite ejecta particles are interpreted to reflect different thermal histories at postshock conditions. Spherulitic calcite particles may represent carbonate melts that were quenched during ejection. A recrystallized microstructure may indicate short, intense thermal stress. Various aggregates document particleparticle interactions and intermixing of components from lower silicate and upper sedimentary target lithologies. Aggregates of recrystallized calcite with silicate melt indicate the consolidation of a hot suevitic component with sediments at > 750°C. Accretionary lapilli formed in a turbulent, steam-condensing environment at ∼100°C by aggregation of solid, ash-sized particles. Concentric zones with smaller grain sizes of accreted particles indicate a recurring exchange with a hotter environment. Our results suggest that during partial ejecta plume collapse, hot silicate components were mixed with the fine fraction of local surface-derived sediments, the latter of which were displaced by the preceding ejecta curtain. These processes sustained a hot, gas-driven, lateral basal transport that was accompanied by a turbulent plume at a higher level. The exothermic back-reaction of CaO from decomposed carbonates and sulfates with CO2 to form CaCO3 may have been responsible for a prolonged release of thermal energy at a late stage of plume evolution. © 2021, The Trustees of the Natural History Museum, London. 2021 10.1130/2021.2550(08) Special Paper of the Geological Society of America 550 207-233 Natural History Museum, Imaging and Analysis Centre, Cromwell Road, London, SW7 5BD, United Kingdom; Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstrasse 43, Berlin, 10115, Germany; Bruker Nano GmbH, Am Studio 2d, Berlin, 12489, Germany; Institut für Geologische Wissenschaften, Freie Universität Berlin, Malteserstraße 74-100, Berlin, 12249, Germany https://www.scopus.com/inward/record.uri?eid=2-s2.0-85126354171&doi=10.1130%2f2021.2550%2808%29&partnerID=40&md5=0d36a9723b7a22cac2d6252d738312f2 cited By 1 T. Salge R. Tagle R.-T. Schmitt L. Hecht article Smith2021283 Palynological analysis of Site M0077A in the Chicxulub impact crater has yielded a record of the immediate Cretaceous/Paleogene (K/Pg) recovery from ground zero of the end-Cretaceous mass extinction, followed by a record of the Paleocene–Eocene Thermal Maximum (PETM) and later Ypresian (Eocene), including the Early Eocene Climatic Optimum (EECO). Eight specimens of the dinoflagellate cyst Trithyrodinium evittii have been observed near the base of the K/Pg transitional unit; these likely represent a post-impact dinoflagellate disaster recovery assemblage deposited within several days following the impact, although the possibility that some or all of the T. evittii specimens are reworked Maastrichtian cysts cannot be fully excluded. Despite high-resolution sampling of the lowermost Paleocene successions, the oldest identifiable terrestrial palynomorphs observed in the Site M0077A core, two specimens of Deltoidospora fern spores, occur at least ∼200,000 years after the impact. Other than these occurrences, the Paleocene section is nearly barren in terms of palynomorphs, likely a result of poor preservation of organic material combined with a long recovery time for vegetation in the vicinity of the crater. Pollen and fungal spore concentrations spike in an anoxic dark shale deposited during the PETM around 56 Ma, with a diverse pollen assemblage indicating the presence of a coastal shrubby tropical forest in the geographic vicinity, likely in the Yucatán Peninsula to the south. In the marine realm, this interval is characterized by thermophilic assemblages of dinoflagellate cysts. Stratigraphically constrained cluster analysis identified four statistically robust sample clusters in the lower Eocene successions, with Malvacipollis spp. and Milfordia spp. abundances driving the highest average dissimilarity between clusters. A second notable spike in palynological concentrations above the PETM section may represent another early Eocene hyperthermal event. Pollen and plant spore concentrations generally increased during the EECO, associated with increases in terrestrial input during basin infilling. © 2020 AASP–The Palynological Society. 2021 10.1080/01916122.2020.1813826 Palynology 45 283-299 Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA, United States; Museum of Natural Science, Louisiana State University, Baton Rouge, LA, United States; Department of Earth and Environmental Sciences, Division of Geology, KU Leuven, Heverlee, Belgium; Analytical, Environmental and Geochemistry (AMGC), Vrije Universiteit Brussel, Brussels, Belgium; Department of Palaeobiology, Swedish Museum of Natural History, Stockholm, Sweden; Université Lyon, UMR5023 Ecologie des Hydrosystèmes Naturels et Anthropisés, ENTPE, CNRS, Université Lyon 1, Lyon, France; Paleobotany and Paleoecology Department, Cleveland Museum of Natural History, Cleveland, OH, United States 2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85091140595&doi=10.1080%2f01916122.2020.1813826&partnerID=40&md5=4e215d80043bb69494282f7ddb2bf5b6 cited By 3 V. Smith S. Warny J. Vellekoop V. Vajda G. Escarguel D.M. Jarzen article McCall2021 Hypervelocity impact cratering is an important geologic process but the rarity of large terrestrial impact craters on Earth and the limited technical options to study cratering processes in the laboratory hinders our understanding of large-scale impact processes. Drill core recovered from the peak ring of the Chicxulub impact crater during International Ocean Discovery Program (IODP)/International Continental scientific Drilling Program (ICDP) Expedition 364 provides an opportunity to examine target rock deformation and thus, to assess cratering models in this regard. Using oriented computer tomography (CT) scans and line scan images of the core, we present the orientations of mm-to-cm-scale planar cataclasite and ultracataclasite zones in the deformed granitoid target rock of the peak ring. In the upper 470 m of the target rock, the cataclasite zones dip towards the crater center, whereas the dip directions for the ultracataclasite zones are approximately tangential to the peak ring. These two orientations are consistent with deformation expected from hydrocode-modeled principal stress directions for the outward movement of rocks as the transient crater develops, and the inward movement of rocks associated with collapse of the transient crater. Near the base of the core is a 96 m-thick interval of highly-deformed target rock with impact melt rock and rock fragments not observed elsewhere in the core; this interval has previously been interpreted as an imbricate thrust zone within the peak ring. The cataclasite zones below this thrust zone have different orientations than those in the 470 m-thick block above. This observation implies a differential rotation from the overlying block during the final stages of peak-ring formation. Our results support an acoustic fluidization process, wherein blocks that vibrate or slide relative to each other allow the target rock to flow during transient crater collapse, and that the size of coherent rock blocks increases over the course of crater modification as the target rock regains its cohesive strength and acoustic fluidization decreases. © 2021 2021 10.1016/j.epsl.2021.117236 Earth and Planetary Science Letters 576 University of Texas at Austin, Jackson School of Geosciences, Institute for Geophysics, Department of Geological Sciences, J.J. Pickle Research Campus, Austin, TX 78758, United States; Center for Planetary Systems Habitability, University of Texas at Austin, Austin, TX, United States; Enthought, Inc., Austin, TX, United States; Institute of Earth and Environmental Sciences—Geology, Albert-Ludwigs Universität Freiburg, Albertstrasse 23b, Freiburg, 79110, Germany; Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ, United Kingdom; Institut für Geologie, Universität Hamburg, Bundesstrasse 55, Hamburg, 20146, Germany; Géosciences Montpellier, Université de Montpellier, CNRS, France; Department of Earth Science and Engineering, Imperial College LondonSW7 2AZ, United Kingdom https://www.scopus.com/inward/record.uri?eid=2-s2.0-85117124335&doi=10.1016%2fj.epsl.2021.117236&partnerID=40&md5=cd6b733a8d2a5d872b00c64c2a13f623 cited By 1 N. McCall S.P.S. Gulick A.S.P. Rae M.H. Poelchau U. Riller J. Lofi J.V. Morgan article Schulte20212619 Core from Hole M0077 from IODP/ICDP Expedition 364 provides unprecedented evidence for the physical processes in effect during the interaction of impact melt with rock-debris-laden seawater, following a large meteorite impact into waters of the Yucatán shelf. Evidence for this interaction is based on petrographic, microstructural and chemical examination of the 46.37-m-thick impact melt rock sequence, which overlies shocked granitoid target rock of the peak ring of the Chicxulub impact structure. The melt rock sequence consists of two visually distinct phases, one is black and the other is green in colour. The black phase is aphanitic and trachyandesitic in composition and similar to melt rock from other sites within the impact structure. The green phase consists chiefly of clay minerals and sparitic calcite, which likely formed from a solidified water–rock debris mixture under hydrothermal conditions. We suggest that the layering and internal structure of the melt rock sequence resulted from a single process, i.e., violent contact of initially superheated silicate impact melt with the ocean resurge-induced water–rock mixture overriding the impact melt. Differences in density, temperature, viscosity, and velocity of this mixture and impact melt triggered Kelvin–Helmholtz and Rayleigh–Taylor instabilities at their phase boundary. As a consequence, shearing at the boundary perturbed and, thus, mingled both immiscible phases, and was accompanied by phreatomagmatic processes. These processes led to the brecciation at the top of the impact melt rock sequence. Quenching of this breccia by the seawater prevented reworking of the solidified breccia layers upon subsequent deposition of suevite. Solid-state deformation, notably in the uppermost brecciated impact melt rock layers, attests to long-term gravitational settling of the peak ring. © 2021, The Author(s). 2021 10.1007/s00531-021-02008-w International Journal of Earth Sciences 110 2619-2636 Institut Für Geologie, Universität Hamburg, Bundesstraße 55, Hamburg, 20146, Germany; Eyring Materials Center, Arizona State UniversityAZ, United States; Mineralogisch-Petrographisches Institut, Universität Hamburg, Grindelallee 48, Hamburg, 20146, Germany; Department of Earth Science and Engineering, Imperial College London, London, SW7 2AZ, United Kingdom; Institute of Geophysics and Department of Geological Sciences, University of Texas at Austin, Austin, TX 78758, United States; Center for Planetary Systems Habitability, University of Texas at Austin, Austin, TX 78712, United States; Lunar and Planetary Institute, Houston, TX 77058, United States; Department of Earth Sciences, University of Western Ontario, London, ON N6A 5B7, Canada; Institute for Earth and Space Exploration, University of Western Ontario, London, ON N6A 5B7, Canada 7 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85113794003&doi=10.1007%2fs00531-021-02008-w&partnerID=40&md5=1296ec1be952508891f64d48b100e173 cited By 4 F.M. Schulte A. Wittmann S. Jung J.V. Morgan S.P.S. Gulick D.A. Kring R.A.F. Grieve G.R. Osinski U. Riller T.J. Bralower E. Chenot G.L. Christeson P. Claeys C.S. Cockell M.J.L. Coolen L. Ferrière C. Gebhardt K. Goto S. Green H. Jones E. LeBer J. Lofi C.M. Lowery R. Ocampo-Torres L. Pérez-Cruz A.E. Pickersgill M.H. Poelchau A.S.P. Rae C. Rasmussen M. Rebolledo-Vieyra H. Sato D. Schmitt J. Smit S.M. Tikoo N. Tomioka J. Urrutia-Fucugauchi M.T. Whalen L. Xiao K.E. Yamaguchi IODP-ICDP Expedition 364 Science Party article Kaskes2021171 Quantitative insights into the geochemistry and petrology of proximal impactites are fundamental to understand the complex processes that affected target lithologies during and after hypervelocity impact events. Traditional analytical techniques used to obtain major- and trace-element data sets focus predominantly on either destructive whole-rock analysis or laboratory-intensive phase-specific micro-analysis. Here, we present micro–X-ray fluorescence (µXRF) as a state-of-the-art, time-efficient, and nondestructive alternative for major- and trace-element analysis for both small and large samples (up to 20 cm wide) of proximal impactites. We applied µXRF element mapping on 44 samples from the Chicxulub, Popigai, and Ries impact structures, including impact breccias, impact melt rocks, and shocked target lithologies. The µXRF mapping required limited to no sample preparation and rapidly generated high-resolution major- and trace-element maps (~1 h for 8 cm2, with a spatial resolution of 25 µm). These chemical distribution maps can be used as qualitative multi-element maps, as semiquantitative single-element heat maps, and as a basis for a novel image analysis workflow quantifying the modal abundance, size, shape, and degree of sorting of segmented components. The standardless fundamental parameters method was used to quantify the µXRF maps, and the results were compared with bulk powder techniques. Concentrations of most major elements (Na2O-CaO) were found to be accurate within 10% for thick sections. Overall, we demonstrate that μXRF is more than only a screening tool for heterogeneous impactites, because it rapidly produces bulk and phase-specific geochemical data sets that are suitable for various applications within the earth sciences. © 2021 The Authors. 2021 10.1130/2021.2550(07) Special Paper of the Geological Society of America 550 171-206 Analytical, Environmental & Geo-Chemistry Research Unit, Department of Chemistry, Vrije Universiteit Brussel (AMGC-WE-VUB), Pleinlaan 2, Brussels, 1050, Belgium; Laboratoire G-Time, Université Libre de Bruxelles, Avenue F.D. Roosevelt 50, Brussels, 1050, Belgium https://www.scopus.com/inward/record.uri?eid=2-s2.0-85111935442&doi=10.1130%2f2021.2550%2807%29&partnerID=40&md5=b8c1f8cc3ea17d0ac2f2924f20afc403 cited By 10 P. Kaskes T. Déhais S.J. Graaff S. Goderis P. Claeys article Yanev202145 The described exotic rock block (60×80×13-15 cm) was found at 290 m depth in a lower.middle Badenian gypsum layer in the Koshava mine, NW Bulgaria, near the Danube River. It is greyish-black, granular, with layered structure and layers composed of α-quartz rosettes covered with organic matter (kerogen-like type with high contents of Ge, Mo and B), wood relicts with chalcedony replacement, and porous lenses with compact accumulation of organic matter. The block is coated with quartz crust, up to 2 cm thick, with regmaglypt-like forms, also replaced by quartz. Aside from the surface, melting phenomena were also observed inside the quartz rosettes and especially in the wood relicts and porous lenses. The melted drops are actually crystallized chalcedony. The organic matter accumulations contain Si-organic zoned micrometre-sized spherules. Fe silicides were found in the organic matter of all parts of the block, in which hapkeite was determined by X-ray analysis. Other detected minerals include graphite, cristobalite, coesite, skeletal and framboidal pyrite, moassanite, magnetite, suessite, sphalerite and minerals formed in the gypsum lagoon (gypsum, celestine, barite, calcite, halite and clays). The geological position of the block in the gypsum without any other sediments, the extensive melting phenomena with melted spherules, crushed quartz, its enrichment in 18O isotope and the presence of coesite suggest that it is shock ejecta, in certain aspects resembling the large Muong Nong-type tektites, but its characteristics could be the basis for distinguishing it as a new tektite type. The fact that it was found in a gypsum layer of early.middle Badenian age points to its probable association with the Ries-Steinheim impact event, despite the long distance between them (~1100 km). © 2021 Geological Institute â€Strashimir Dimitrovâ€, Bulgarian Academy of Sciences. 2021 10.52321/GeolBalc.50.1.45 Geologica Balcanica 50 45-65 Geological Institute, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 24, Sofia, 1113, Bulgaria; University of Stuttgart, Stuttgart, 70569, Germany; Institute of Geology of Ore Deposits, Mineralogy, Petrography and Geochemistry (IGEM), Russian Academy of Sciences, 35/1 Staromonetnyi pereulok, Moscow, 119017, Russian Federation; Bulgarian Geological Society, Bulgaria 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85123594717&doi=10.52321%2fGeolBalc.50.1.45&partnerID=40&md5=0894f71d491415e900af44a7f60ea39b cited By 1 Y. Yanev A. Benderev N. Zotov E. Dubinina I. Iliev S. Georgiev I. Ilieva I. Sergeeva article Ormö2021 The rim wall of water formed from even a modestly-sized marine impact may be kilometers in height. Although modeling has shown that this wave swiftly breaks and relatively rapidly loses energy during outwards travel from the impact site, the portion of the rim wall that collapses inwards may generate a resurge flow with tremendous transport energy. Here we compare the deposits generated by this ocean resurge inside one of the largest marine-target craters on Earth, the 200-km wide Chicxulub crater, Yucatán Peninsula, México, with resurge deposits (breccias) in eight drill cores from five other marine-target craters in Sweden and the United States. Examination of the wide range of cored locations within the craters, and target water depths (H) relative to modeled projectile diameters (d) reveal a high correlation between location, average clast frequency (〈N〉), and d/H from which any of the four variables can be obtained. The relationship shown here may provide an important tool for diagnosing marine impact cratering processes where there is limited understanding of crater size and/or paleobathymetry. © 2021 The Authors 2021 10.1016/j.epsl.2021.116915 Earth and Planetary Science Letters 564 Centro de Astrobiologia (INTA-CSIC), Ctra Torrejon a Ajalvir km4, Torrejon de Ardoz, 28850, Spain; Inst. for Geophysics, Dept. of Geological Sciences, Jackson School of Geosciences, Univ. of Texas at Austin, 10100 Burnet Rd Bldg. ROC, Austin, TX 78758, United States; Center for Planetary Systems Habitability, Univ. of Texas at Austin, Austin, TX 78712, United States; Dept. of Geosciences, University of Alaska Fairbanks, United States; Dept. of Geosciences, Auburn University, 2058 Memorial Coliseum, Auburn, AL 36849, United States; Earth Sciences Centre, Univ. of Gothenburg, Sweden; Dept. of Earth Science and Engineering, Imperial College London, United Kingdom https://www.scopus.com/inward/record.uri?eid=2-s2.0-85104366669&doi=10.1016%2fj.epsl.2021.116915&partnerID=40&md5=394b9686c2db99a3b56fdbf5cf243b5a cited By 8 J. Ormö S.P.S. Gulick M.T. Whalen Jr. King E. Sturkell J. Morgan article Feignon20211243 The IODP-ICDP Expedition 364 drilling recovered a 829 m core from Hole M0077A, sampling ~600 m of near continuous crystalline basement within the peak ring of the Chicxulub impact structure. The bulk of the basement consists of pervasively deformed, fractured, and shocked granite. Detailed geochemical investigations of 41 granitoid samples, that is, major and trace element contents, and Sr-Nd isotopic ratios are presented here, providing a broad overview of the composition of the granitic crystalline basement. Mainly granite but also granite clasts (in impact melt rock), granite breccias, and aplite were analyzed, yielding relatively homogeneous compositions between all samples. The granite is part of the high-K, calc-alkaline metaluminous series. Additionally, they are characterized by high Sr/Y and (La/Yb)N ratios, and low Y and Yb contents, which are typical for adakitic rocks. However, other criteria (such as Al2O3 and MgO contents, Mg#, K2O/Na2O ratio, Ni concentrations, etc.) do not match the adakite definition. Rubidium–Sr errorchron and initial 87Sr/86Srt=326Ma suggest that a hydrothermal fluid metasomatic event occurred shortly after the granite formation, in addition to the postimpact alteration, which mainly affected samples crosscut by shear fractures or in contact with aplite, where the fluid circulation was enhanced, and would have preferentially affected fluid-mobile element concentrations. The initial (ɛNd)t=326Ma values range from −4.0 to 3.2 and indicate that a minor Grenville basement component may have been involved in the granite genesis. Our results are consistent with previous studies, further supporting that the cored granite unit intruded the Maya block during the Carboniferous, in an arc setting with crustal melting related to the closure of the Rheic Ocean associated with the assembly of Pangea. The granite was likely affected by two distinct hydrothermal alteration events, both influencing the granite chemistry: (1) a hydrothermal metasomatic event, possibly related to the first stages of Pangea breakup, which occurred approximately 50 Myr after the granite crystallization, and (2) the postimpact hydrothermal alteration linked to a long-lived hydrothermal system within the Chicxulub structure. Importantly, the granites sampled in Hole M0077A are unique in composition when compared to granite or gneiss clasts from other drill cores recovered from the Chicxulub impact structure. This marks them as valuable lithologies that provide new insights into the Yucatán basement. © 2021 The Authors. Meteoritics & Planetary Science published by Wiley Periodicals LLC on behalf of The Meteoritical Society (MET) 2021 10.1111/maps.13705 Meteoritics and Planetary Science 56 1243-1273 Department of Lithospheric Research, University of Vienna, Althanstrasse 14, Vienna, A-1090, Austria; Research Unit: Analytical, Environmental & Geo-Chemistry, Department of Chemistry, Vrije Universiteit Brussel, AMGC-WE-VUB, Pleinlaan 2, Brussels, 1050, Belgium; Laboratoire G-Time, Université Libre de Bruxelles, Av. F.D. Roosevelt 50, Brussels, 1050, Belgium; Natural History Museum, Burgring 7, Vienna, A-1010, Austria 7 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85111937863&doi=10.1111%2fmaps.13705&partnerID=40&md5=7b181a4562612d56d0a5dfaa9a5d409e cited By 3 J.-G. Feignon S.J. Graaff L. Ferrière P. Kaskes T. Déhais S. Goderis P. Claeys C. Koeberl article Ebert2021479 During hypervelocity impacts, target rocks are subjected to shock wave compression with high pressures and differential stresses. These differential stresses cause microscopic shear-induced deformation, which can be observed in the form of kinking, twinning, fracturing, and shear faulting in a range of minerals. The orientation of these shear-induced deformation features can be used to constrain the maximum shortening axis. Under the assumption of pure shear deformation, the maximum shortening axis is parallel to the maximum principal axis of stress, σ1, which gives the propagation direction of the shock wave that passed through a rock sample. In this study, shocked granitoids cored from the uppermost peak ring of the Chicxulub crater (International Ocean Discovery Program [IODP]/International Continental Drilling Project [ICDP] Expedition 364) were examined for structures formed by shearing. Orientations of kink planes in biotite and basal planar deformation features (PDFs) in quartz were measured with a U-stage and compared to a previous study of feather feature orientations in quartz from the same samples. In all three cases, the orientations of the shortening axis derived from these measurements were in good agreement with each other, indicating that the shear deformation features all formed in an environment with similar orientations of the maximum principal axis of stress. These structures formed by shearing are useful tools that can aid in understanding the deformational effects of the shock wave, as well as constraining shock wave propagation and postshock deformation during the cratering process. © 2021 The Geological Society of America. 2021 10.1130/2021.2550(21) Special Paper of the Geological Society of America 550 479-493 Institute of Earth and Environmental Sciences-Geology, Universität Freiburg, Albertstraße 23B, Freiburg, 79104, Germany; Center for Planetary Systems Habitability, Jackson School of Geosciences, Institute for Geophysics, Department of Geological Sciences, University of Texas at Austin, 10100 Burnet Road Building ROC, Austin, TX 78758, United States; Enthought Inc., Austin, TX 78701, United States; Géosciences Montpellier, Université de Montpellier, Centre National de la Recherche Scientifique, Université des Antilles, Place E. Bataillon, Montpellier cedex 5, 34095, France; Department of Earth Sciences, University of Cambridge, Cambridge, CB2 3EQ, United Kingdom https://www.scopus.com/inward/record.uri?eid=2-s2.0-85126303789&doi=10.1130%2f2021.2550%2821%29&partnerID=40&md5=d3797a32e28345969beb11584ad30f9e cited By 0 M. Ebert M.H. Poelchau T. Kenkmann S.P.S. Gulick J. Lofi N. McCall A.S.P. Rae article Christeson2021 We integrate high-resolution full-waveform velocity models with seismic reflection images to map the peak ring and impactite stratigraphy at the Chicxulub structure. International Ocean Discovery Program/International Continental scientific Drilling Program Site M0077 provides ground truth for our interpretations. The peak ring is narrower (∼10 km width) where it is high relief (600–700 m below seafloor) and wider (∼15 km width) where it is lower relief (1,000–1,200 m below seafloor). Both target asymmetry and angle of impact could have contributed to observed differences in peak ring morphology. We interpret a layer of lowered velocities as a resurge layer formed from the ocean resurge, seiche, and returning tsunami flowing into the newly formed impact basin. This graded suevite layer has an average thickness of 187 ± 58 m with only local thickness differences within the annular trough, peak ring, and central basin. These observations suggest that the returning ocean was of substantial height and energetic enough to carry debris across the entire topographic peak ring. We map impact melt rock throughout the crater, with a thick impact melt sheet in the central basin (>500 m), thin intermittent melt rock capping the peak ring, and a ∼500-m thick layer of melt rock in the annular trough near the peak ring that thins toward the crater rim. We estimate that ∼70%–75% of the melt rock volume is in the central basin. We image features above and adjacent to the central basin melt sheet that we interpret as upflow zones associated with a long-lasting hydrothermal system. © 2021. American Geophysical Union. All Rights Reserved. 2021 10.1029/2021JE006938 Journal of Geophysical Research: Planets 126 Jackson School of Geosciences, Institute for Geophysics, University of Texas at Austin, Austin, TX, United States; Department of Earth Science and Engineering, Imperial College London, London, United Kingdom; Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, TX, United States; Center for Planetary Systems Habitability, University of Texas at Austin, Austin, TX, United States 8 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85113741472&doi=10.1029%2f2021JE006938&partnerID=40&md5=07f7d40d0fe3a17cefa6922354461584 cited By 5 G.L. Christeson J.V. Morgan S.P.S. Gulick article Goderis2021 The Cretaceous-Paleogene (K-Pg) mass extinction is marked globally by elevated concentrations of iridium, emplaced by a hypervelocity impact event 66 million years ago. Here, we report new data from four independent laboratories that reveal a positive iridium anomaly within the peak-ring sequence of the Chicxulub impact structure, in drill core recovered by IODP-ICDP Expedition 364. The highest concentration of ultrafine meteoritic matter occurs in the post-impact sediments that cover the crater peak ring, just below the lowermost Danian pelagic limestone. Within years to decades after the impact event, this part of the Chicxulub impact basin returned to a relatively low-energy depositional environment, recording in unprecedented detail the recovery of life during the succeeding millennia. The iridium layer provides a key temporal horizon precisely linking Chicxulub to K-Pg boundary sections worldwide. Copyright © 2021 The Authors, some rights reserved. 2021 10.1126/sciadv.abe3647 Science Advances 7 Analytical, Environmental, and Geochemistry, Vrije Universiteit Brussel, Brussels, Belgium; Department of Geosciences, University of Padova, Padova, Italy; Sub-marine Resources Research Center, Research Institute for Marine Resources Utilization, Japan Agency for Marine-Earth Science and Technology, Kanagawa, Japan; Natural History Museum, Vienna, Austria; Astrogeobiology Laboratory, Division of Nuclear Physics, Department of Physics, Lund University, Lund, Sweden; Depart-ment of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN, United States; Laboratoire G-Time, Université Libre de Bruxelles, Brussels, Belgium; Department of Geology, KU Leuven, Leuven, Belgium; Eyring Materials Center, Arizona State University, Tempe, AZ, United States; Department of Lithospheric Research, University of Vienna, Vienna, Austria; Institut für Geologie und Mineralogie, Universität zu Köln, Köln, Germany; Atomic and Mass Spectrometry-A&MS research group, Department of Chemistry, Ghent University, Ghent, Belgium; Department of Earth Sciences, Utrecht University, Utrecht, Netherlands; Depart-ment of Earth and Planetary Sciences, Tokyo Institute of Technology, Tokyo, Japan; Department of Earth, Ocean and Atmospheric Science and National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, United States; HNU Neu-Ulm University of Applied Sciences, Neu-Ulm, Germany; Lunar and Planetary Institute-USRA, Houston, TX, United States; Department of Earth Sciences, Durham University, Durham, United Kingdom; Department of Geosciences, Pennsylvania State University, University Park, PA, United States; Institute for Geophysics, University of Texas at Austin, Austin, TX, United States; Department of Geological Sciences, University of Texas at Austin, Austin, TX, United States; Center for Planetary Systems Habitability, University of Texas, Austin, TX, United States; Department of Earth Science and Engineering, Imperial College London, London, United Kingdom; Department of Earth Sciences, Vrije Universiteit Amsterdam, Amsterdam, Netherlands; Depart-ment of Geosciences, University of Alaska Fairbanks, Fairbanks, AK, United States 9 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85102098183&doi=10.1126%2fsciadv.abe3647&partnerID=40&md5=4c9345ae7f6088338602dfb83ae92121 cited By 24 S. Goderis H. Sato L. Ferrière B. Schmitz D. Burney P. Kaskes J. Vellekoop A. Wittmann T. Schulz S.M. Chernonozhkin P. Claeys S.J. Graaff T. Déhais N.J. Winter M. Elfman J.-G. Feignon A. Ishikawa C. Koeberl P. Kristiansson C.R. Neal J.D. Owens M. Schmieder M. Sinnesael F. Vanhaecke S.J.M. Malderen T.J. Bralower S.P.S. Gulick D.A. Kring C.M. Lowery J.V. Morgan J. Smit M.T. Whalen IODP-ICDP Expedition 364 Scientists article Kring20211547 A sulfate-reducing population of thermophiles grew in porous, permeable niches within glass-bearing impact breccias of the Chicxulub impact crater. The microbial community grew in an impact-generated hydrothermal system that vented on the seafloor several hundred meters beneath the sea surface. Potential electron donors for that metabolism are hydrocarbons, although a strong C-isotope signature of that source does not exist. Model calculations explored here suggest that alteration of glass within the impact breccias may have produced H2 in sufficient quantities for population growth as the hydrothermal system cooled through thermophilic temperatures, although it is sensitive to the oxidation state of iron in the melt rock prior to hydrothermal alteration and the secondary mineral assemblage. At high water-to-rock ratios and temperatures below 45°C, H2 yields are insufficient to maintain a population of hydrogenotrophic sulfate-reducing bacteria, but yields double with a higher proportion of ferrous iron between 45 and 65°C. The most reduced rocks (i.e., highest proportion of ferrous iron) that are allowed to form andradite, which is observed in core samples, produce copious amounts of H2 in the temperature window for thermophiles and hyperthermophiles. Mixtures of melt rock and carbonate, which is observed in breccia matrices, produce somewhat less H2, and the onset of massive H2 production is shifted to higher temperatures (i.e., lower W/R). © Copyright 2021, Mary Ann Liebert, Inc., publishers 2021. 2021 10.1089/ast.2021.0045 Astrobiology 21 1547-1564 Lunar and Planetary Institute, Universities Space Research Association, Houston, Texas, United States; Geoscience Department and MARUM, Center for Marine Environmental Sciences, Universität Bremen, Bremen, Germany 12 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85121355110&doi=10.1089%2fast.2021.0045&partnerID=40&md5=967ef120fc982d73f5dff3bd1f3658a2 cited By 1 D.A. Kring W. Bach article Ortiz-Aleman202155 Large impact structures are characterized by peak ring and central uplifts with lateral/vertical mass transport during late formation stages. Here we investigate the Chicxulub crater, which has been surveyed by an array of marine, aerial and land-borne geophysical methods. Seismic reflection surveys in its central sector have shown lack of resolution, making it difficult to image the central uplift. We develop an integrated seismic and gravity model for the structural elements, imaging the central uplift and melt and breccia units. The 3D velocity model built from interpolation of seismic data is validated using perfectly matched layer seismic acoustic wave propagation modeling, optimized at grazing incidence using the shift in the frequency domain. Modeling shows that lack of illumination relates to seismic energy that remains trapped in an upper low-velocity zone corresponding to the carbonate sediments, upper melt/breccias and surrounding faulted blocks. After conversion of seismic velocities into a volume of density values, we apply parallel forward gravity modeling to constrain the size and shape of the central uplift, which has a ~ 40 km diameter concave upwards top lying at ~ 3.5–4.5 km depth. The preferred model provides a high-resolution image of crater units and structure. The gravity response of modeled units shows asymmetries in structure and the distribution of breccias, melt and target carbonates. Finally, we apply an adjoint reverse time migration approach for seismic imaging using the density and velocity models built for the acoustic wave propagation and gravity modeling, which allows improved modeling of the crater structure. © 2021, Springer Nature Switzerland AG. 2021 10.1007/s00024-020-02638-2 Pure and Applied Geophysics 178 55-77 Litoteca Nacional de Hidrocarburos Sede Merida, Parque Cientifico y Tecnologico de Yucatan, Sierra Papacal, Mérida, Yucatán, Mexico; Laboratoire GET/Géosciences Environnement Toulouse, UMR CNRS 5563, Observatoire Midi Pyrénées, Université Paul Sabatier, 14 avenue Edouard Belin, Toulouse, 31400, France; Programa de Perforaciones en Océanos y Continentes, Instituto de Geofisica, Universidad Nacional Autónoma de Mexico, Coyoacan, Mexico City, 04510, Mexico; Instituto de Investigaciòn Cientìfica y Estudios Avanzados Chicxulub, Parque Cientifico y Tecnologico de Yucatan, Sierra Papacal, Mérida, Yucatán 97302, Mexico; Tecnológico Nacional de México/IT de Mérida, Departamento de Sistemas y Computación, Mérida, Yucatán, Mexico 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85099082352&doi=10.1007%2fs00024-020-02638-2&partnerID=40&md5=85a68c903744118862c97f6fe41568be cited By 2 C. Ortiz-Aleman R. Martin J. Urrutia-Fucugauchi M.O. Castillo M. Nava-Flores article Arp2021 Since its recognition as an impact structure 60 years ago, no volcanics were anticipated in the circular depression of the 14.8 Ma old Nördlinger Ries. Here, we describe for the first time a volcanic ash-derived clinoptilolite-heulandite-buddingtonite bed within the 330 m thick Miocene lacustrine crater fill. Zircon U-Pb ages of 14.20 ± 0.08 Ma point to the source of the volcanic ash in the Pannonian Basin, 760 km east of the Ries. The diagenetically derived zeolite-feldspar bed occurs in laminated claystones of the Ries soda-lake stage and represents the first unequivocal stratigraphic marker bed in this basin, traceable from marginal surface outcrops to 218 m below surface in the crater center. These relationships demonstrate a deeply bowl-shaped geometry of crater fill sediments, not explainable by sediment compaction and corresponding stratigraphic backstripping alone. Since most of the claystones formed at shallow water depths, the bowl-shaped geometry must reflect 134 +23/−49 m of sagging of the crater floor. We attribute the sagging to compaction and closure of the dilatant macro-porosity of the deeply fractured and brecciated crater floor during basin sedimentation and loading, a process that lasted for more than 0.6 Myr. As a result, the outcrop pattern of the lithostratigraphic crater-fill units in its present erosional plane forms a concentric pattern. Recognition of this volcanic ash stratigraphic marker in the Ries crater provides insights into the temporal and stratigraphic relationships of crater formation and subsidence that have implications for impact-hosted lakes on Earth and Mars. © 2021. The Authors. 2021 10.1029/2020JE006764 Journal of Geophysical Research: Planets 126 Geoscience Center, Georg-August-University, Göttingen, Germany; Geological Survey, Bavarian Environment Agency, Hof/Saale, Germany; MTA-ELTE Volcanology Research Group, Budapest, Hungary; Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, RI, United States 4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85104590683&doi=10.1029%2f2020JE006764&partnerID=40&md5=505e70dbb1e5e615f49eb400ff114452 cited By 4 G. Arp I. Dunkl D. Jung V. Karius R. Lukács L. Zeng A. Reimer III Head article Whalen2020 The Chicxulub impact led to the formation of a ~ 200-km wide by ~1-km deep crater on México's Yucatán Peninsula. Over a period of hours after the impact the ocean re-entered and covered the impact basin beneath several hundred meters of water. A suite of impactites were deposited across the crater during crater formation, and by the resurge, tsunami and seiche events that followed. International Ocean Discovery Program/International Continental Scientific Drilling Program Expedition 364 drilled into the peak ring of the Chicxulub crater, and recovered ~130 m of impact deposits and a 75-cm thick, fine-grained, carbonate-rich “Transitional Unit”, above which normal marine sedimentation resumed. Here, we describe the results of analyses of the uppermost impact breccia (suevite) and the Transitional Unit, which suggests a gradual waning of energy recorded by this local K-Pg boundary sequence. The dominant depositional motif in the upper suevite and the Transitional Unit is of rapid sedimentation characterized by graded bedding, local cross bedding, and evidence of oscillatory currents. The lower Transitional Unit records the change from deposition of dominantly sand-sized to mainly silt to clay sized material with impact debris that decreases in both grain size and abundance upward. The middle part of the Transitional Unit is interrupted by a 20 cm thick soft sediment slump overlain by graded and oscillatory current cross-laminated beds. The uppermost Transitional Unit is also soft sediment deformed, contains trace fossils, and an increasing abundance of planktic foraminifer and calcareous nannoplankton survivors. The Transitional Unit, as with similar deposits in other marine target impact craters, records the final phases of impact-related sedimentation prior to resumption of normal marine conditions. Petrographic and stable isotopic analyses of carbon from organic matter provide insight into post-impact processes. δ13Corg values are between terrestrial and marine end members with fluctuations of 1–3‰. Timing of deposition of the Transitional Unit is complicated to ascertain. The repetitive normally graded laminae, both below and above the soft sediment deformed interval, record rapid deposition from currents driven by tsunami and seiches, processes that likely operated for weeks to potentially years post-impact due to subsequent continental margin collapse events. Highly siderophile element-enrichment at the top of the unit is likely from fine-grained ejecta that circulated in the atmosphere for several years prior to settling. The Transitional Unit is thus an exquisite record of the final phases of impact-related sedimentation related to one of the most consequential events in Earth history. © 2020 The Authors 2020 10.1016/j.margeo.2020.106368 Marine Geology 430 Dept. of Geosciences and Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK 99775, United States; Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78758, United States; Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 79712, United States; Center for Planetary Systems Habitability, University of Texas at Austin, Austin, TX 79712, United States; Department of Geosciences, Pennsylvania State University, University ParkPA 16801, United States; Department of Earth Science and Engineering, Imperial College London, London, SW7 2AZ, United Kingdom; Western Australian Organic and Isotope Geochemistry Centre, The Institute for Geoscience Research, School of Earth and Planetary Science, Curtin University, Perth, WA 6102, Australia; Faculty of Earth and Life Sciences (FALW), Vrije Universiteit Amsterdam, Amsterdam, 1081 HV, Netherlands; Centro de Astrobiología Instituto Nacional de Técnica Aeroespacial-Spanish National Research Council (INTA-CSIC), Instituto Nacional de Técnica Aeroespacial, Torrejon de Ardoz, 28850, Spain; Eyring Materials Center, Arizona State University, Tempe, AZ 85287-1704, United States; Lunar and Planetary Institute, Houston, TX 77058, United States; Analytical, Environmental and Geo-Chemistry, Vrije Universiteit Brussel, Brussels, Belgium https://www.scopus.com/inward/record.uri?eid=2-s2.0-85095704506&doi=10.1016%2fj.margeo.2020.106368&partnerID=40&md5=9062d5371f10f30888417b6040880eb2 cited By 14 M.T. Whalen S.P.S. Gulick C.M. Lowery T.J. Bralower J.V. Morgan K. Grice B. Schaefer J. Smit J. Ormö A. Wittmann D.A. Kring S. Lyons S. Goderis article Simpson2020 The 66 Ma, ∼180 km Chicxulub impact structure in the northern Yucatán peninsula and southern Gulf of Mexico is the best-preserved large impact crater on Earth with a well-developed peak ring. The most recent drilling campaign took place offshore during the joint International Ocean Discovery Program – International Continental Scientific Drilling Program (IODP–ICDP) Expedition 364 at site M0077A (21.45°N, 89.95°W) and recovered ∼830 m of continuous core. Initial examination revealed that the peak-ring comprises four main lithological units (from the base upwards): crystalline basement granitoid rocks (Unit 4); a thin layer of impact melt rocks (Units 3A and B); melt-bearing breccias (Units 2A–C); and post-impact sedimentary rocks (Unit 1). Preliminary analysis of the drill core indicated that hydrothermal alteration has affected all lithologies and is especially pervasive in the melt-bearing breccias of Unit 2 (721.6 to 617.33 meters below sea floor, mbsf). Here we present the first detailed investigation of hydrothermal alteration within the melt-bearing breccias. Alteration phases are predominantly Fe-Mg clay minerals, zeolites, alkali feldspars, calcite and minor sulfides, sulfates, opal and Fe-Ti oxides. Alteration is especially intense proximal to lithologic contacts, particularly at the base of subunit 2B where there is an abrupt increase in host rock porosity ∼30 m above the impact melt rocks. The pervasiveness of clay minerals and zeolites is attributed to the high amounts of devitrified silicate glass throughout Unit 2. The phases preserved here are consistent with the findings of previous hydrothermal studies in other areas of the Chicxulub structure, and suggest an evolving water-rock system that was alkaline-saline, comparable to seawater-volcanic glass alteration. © 2020 Elsevier B.V. 2020 10.1016/j.epsl.2020.116425 Earth and Planetary Science Letters 547 Department of Earth Sciences, Institute for Earth and Space Exploration, The University of Western OntarioON N6A 3K7, Canada; Lunar and Planetary Institute, Universities Space Research Association, Houston, TX 77058, United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-85088226608&doi=10.1016%2fj.epsl.2020.116425&partnerID=40&md5=4fe32f301e3861274f69391e1e6510de cited By 16 S.L. Simpson G.R. Osinski F.J. Longstaffe M. Schmieder D.A. Kring article Osinski20201121 The conditions, timing, and setting for the origin of life on Earth and whether life exists elsewhere in our solar system and beyond represent some of the most fundamental scientific questions of our time. Although the bombardment of planets and satellites by asteroids and comets has long been viewed as a destructive process that would have presented a barrier to the emergence of life and frustrated or extinguished life, we provide a comprehensive synthesis of data and observations on the beneficial role of impacts in a wide range of prebiotic and biological processes. In the context of previously proposed environments for the origin of life on Earth, we discuss how meteorite impacts can generate both subaerial and submarine hydrothermal vents, abundant hydrothermal-sedimentary settings, and impact analogues for volcanic pumice rafts and splash pools. Impact events can also deliver and/or generate many of the necessary chemical ingredients for life and catalytic substrates such as clays as well. The role that impact cratering plays in fracturing planetary crusts and its effects on deep subsurface habitats for life are also discussed. In summary, we propose that meteorite impact events are a fundamental geobiological process in planetary evolution that played an important role in the origin of life on Earth. We conclude with the recommendation that impact craters should be considered prime sites in the search for evidence of past life on Mars. Furthermore, unlike other geological processes such as volcanism or plate tectonics, impact cratering is ubiquitous on planetary bodies throughout the Universe and is independent of size, composition, and distance from the host star. Impact events thus provide a mechanism with the potential to generate habitable planets, moons, and asteroids throughout the Solar System and beyond. © G.R. Osinski et al., 2020; Published by Mary Ann Liebert, Inc. 2020. 2020 10.1089/ast.2019.2203 Astrobiology 20 1121-1149 Institute for Earth and Space Exploration, University of Western Ontario, London, Canada; Department of Earth Sciences, University of Western Ontario, 1151 Richmond Street, London, ON N6A 5B7, Canada; Uk Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom; Department of Biology, Georgetown University, Washington, DC, United States; Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, United States; Department of Earth Sciences, University of Southern California, Los Angeles, CA, United States 9 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85088226467&doi=10.1089%2fast.2019.2203&partnerID=40&md5=f7f9a825384539b81757ba1231ea024c cited By 34 G.R. Osinski C.S. Cockell A. Pontefract H.M. Sapers article Osinski2020 The origin of the Stac Fada Member has been debated for decades with several early hypotheses being proposed, but all invoking some connection to volcanic activity. In 2008, the discovery of shocked quartz led to the hypothesis that the Stac Fada Member represents part the continuous ejecta blanket of a meteorite impact crater, the location of which was, and remains, unknown. In this paper, we confirm the presence of shock-metamorphosed and-melted material in the Stac Fada Member; however, we also show that its properties are unlike any other confirmed and well documented proximal impact ejecta deposits on Earth. Instead, the properties of the Stac Fada Member are most similar to the Onaping Formation of the Sudbury impact structure (Canada) and impact melt-bearing breccias from the Chicxulub impact structure (Mexico). We thus propose that, like the Sudbury and Chicxulub deposits, Melt Fuel Coolant Interactions – akin to what occur during phreatomagmatic volcanic eruptions – played a fundamental role in the origin of the Stac Fada Member. We conclude that these rocks are not primary impact ejecta but instead were deposited beyond the extent of the continuous ejecta blanket as high-energy ground-hugging sediment gravity flows. © 2020 The Author(s). Published by The Geological Society of London. All rights reserved. 2020 10.1144/jgs2020-056 Journal of the Geological Society 178 Department of Earth Sciences, University of Western Ontario, London, ON N6A 5B7, Canada; Institute for Earth and Space Exploration, University of Western Ontario, London, ON N6A 5B7, Canada; Natural History Museum, Burgring 7, Vienna, A-1010, Austria; Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB T6G 2E3, Canada; School of Earth and Environmental Sciences, University of St Andrews, St Andrews, Fife, KY16 9AL, United Kingdom; Department of Earth Sciences, The Natural History Museum, Cromwell Road, London, SW7 5BD, United Kingdom; School of Geographical and Earth Sciences, University of Glasgow, Glasgow, G12 8QQ, United Kingdom 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85100491204&doi=10.1144%2fjgs2020-056&partnerID=40&md5=5d0f02264b99c26fc17b05a45f9788ee cited By 1 G.R. Osinski L. Ferrière P.J.A. Hill A.R. Prave L.J. Preston A. Singleton A.E. Pickersgill article Timms202012 Hydrothermal activity is a common phenomenon in the wake of impact events, yet identifying and dating impact hydrothermal systems can be challenging. This study provides the first detailed assessment of the effects of shock microstructures and impact-related alteration on the U-Pb systematics and trace elements of titanite (CaTiSiO5), focusing on shocked granite target rocks from the peak ring of the Chicxulub impact structure, Mexico. A &gt; 1 mm long, shock-twinned titanite grain preserves a dense network of irregular microcracks, some of which exploit shock twin interfaces. Secondary microcrystalline anatase and pyrite are heterogeneously distributed along some microcracks. In situ laser ablation multi-collector inductively-coupled plasma mass spectrometry (LA-MC-ICPMS) analysis reveals a mixture of three end-member Pb components. The Pb components are: 1) common Pb, consistent with the Pb isotopic signature of adjacent alkali feldspar; 2) radiogenic Pb accumulated since magmatic crystallization; and 3) a secondary, younger Pb signature due to impact-related complete radiogenic Pb loss. The youngest derived ages define a regression from common Pb that intersects Concordia at 67 ± 4 Ma, in agreement with the established age of 66.04 ± 0.05 Ma for the Chicxulub impact event. Contour maps of LA-MC-ICPMS data reveal that the young ages are spatially restricted to microstructurally-complex domains that correlate with significant depletion in trace elements (REE-Y-Zr-Nb-Mo-Sn-Th) and reduction in magnitude of the Eu/Eu* anomaly. Mapping by time-of-flight secondary ion mass spectrometry (ToF-SIMS) show that patterns of localised element depletion in titanite are spatially related to microcracks, which are enriched in Al. The spatial correlation of ages and trace element abundance is consistent with localised removal of Pb and other trace elements from a pervasive network of fast fluid pathways in fractured domains via a fluid-mediated element transport process associated with the impact event. Here we interpret the 67 ± 4 Ma U-Pb age to represent hydrothermal Pb-loss in the Chicxulub peak ring in the wake of the impact event. These results highlight the potential of our analytical approach using titanite geochronology and geochemistry for dating post-impact hydrothermal activity in impact structures elsewhere. © 2020 Elsevier Ltd 2020 10.1016/j.gca.2020.04.031 Geochimica et Cosmochimica Acta 281 12-30 The Institute for Geoscience Research (TIGeR), Curtin University, Perth, GPO Box U1987WA 6845, Australia; Space Science and Technology Centre, Curtin University, Perth, GPO Box U1987WA 6845, Australia; School of Earth and Planetary Sciences, Curtin University, Perth, GPO Box U1987WA 6845, Australia; Centre for Exploration Targeting – Curtin Node, Curtin University, Perth, GPO Box U1987WA 6845, Australia; John de Laeter Centre, Curtin University, Perth, GPO Box U1987WA 6845, Australia; Institute of Geology, Albert-Ludwigs-Universität, Freiburg, Albertstraße 23b, Freiburg, 79104, Germany; Jacobs – JETS, NASA Johnson Space Center, Astromaterials Research and Exploration Science Division, Mailcode XI3, 2101 NASA Parkway, Houston, TX, United States; Eyring Materials Center, Arizona State University, Tempe, AZ, United States; Natural History Museum, Burgring 7, 1010, Vienna, Austria; Department of Earth Science and Engineering, Imperial College London, London, United Kingdom; Center for Planetary Systems Habitability, Institute for Geophysics and Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, TX, United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-85084995397&doi=10.1016%2fj.gca.2020.04.031&partnerID=40&md5=b275e7ae541a27aacdc2dec1cf4b83ea cited By 16 N.E. Timms C.L. Kirkland A.J. Cavosie A.S.P. Rae W.D.A. Rickard N.J. Evans T.M. Erickson A. Wittmann L. Ferrière G.S. Collins S.P.S. Gulick article Salguero-Hernández2020627 Chicxulub crater formed ~ 66 Ma ago by an asteroid impact on the Yucatan platform in the southern Gulf of Mexico. The crater has a ~ 200 km rim diameter and has been covered by carbonate sediments up to ~ 1.1 km thick in the central zone. Previous studies have identified the structure and major crater units through geophysical models from seismic reflection and potential field data, classified as the central uplift, terrace zone, outer and inner ring fault zones and impactite deposits. Impact produced a deep excavation cavity, with fragmentation and ejection of large volumes of crustal target rocks. Understanding the pre-existing structures, impact-induced deformation and post-impact processes requires high-resolution images of the crater and target zone. For this study, we use complex trace attributes of instantaneous phase, frequency, envelope amplitude and similarity, in an E-W seismic reflection profile crossing the crater in the marine sector. Geophysical logs and borehole lithological columns from the on-land drilling projects are used to constrain the petrophysical analysis. Seismic attributes aid to characterize the radial fault zones and physical property contrasts, revealing asymmetries in the crater structure. The reflector packages in the post-impact sediments and target Cretaceous sequence are identified in the frequency and phase attributes. The bottom crater reflectors, with the basal sediments filling the crater floor topography, are enhanced with the envelope amplitude attribute. A set of high-amplitude reflectors is shown in the similarity attribute, in which the reflector geometry is delineated on the target carbonate sequence. The offsets in the high-amplitude reflectors between the eastern and western sectors are possibly associated to target pre-impact asymmetries, impact deformation and effects of central crater collapse. © 2020, Institute of Geophysics, Polish Academy of Sciences & Polish Academy of Sciences. 2020 10.1007/s11600-020-00442-z Acta Geophysica 68 627-640 Facultad de Ingeniería, Universidad Autónoma del Carmen, Ciudad del Carmen, Campeche 24180, Mexico; Programa Universitario de Perforaciones en Océanos y Continentes, Instituto de Geofísica, Universidad Nacional Autónoma de México, Ciudad Universitaria, México, 04510, Mexico; Coordinación de Plataformas Oceanográficas, Coordinación de la Investigación Científica, Universidad Nacional Autónoma de México, Ciudad Universitaria, México, 04510, Mexico; Instituto de Investigación Científica y Estudios Avanzados Chicxulub, Parque Científico y Tecnológico de Yucatán, Sierra Papacal, Mérida, Yucatán 97302, Mexico 3 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085291034&doi=10.1007%2fs11600-020-00442-z&partnerID=40&md5=402dc453e354caa5cea6d9ca96aa1d81 cited By 2 E. Salguero-Hernández L. Pérez-Cruz J. Urrutia-Fucugauchi article Kring2020 The ~180-km-diameter Chicxulub peak-ring crater and ~240-km multiring basin, produced by the impact that terminated the Cretaceous, is the largest remaining intact impact basin on Earth. International Ocean Discovery Program (IODP) and International Continental Scientific Drilling Program (ICDP) Expedition 364 drilled to a depth of 1335 m below the sea floor into the peak ring, providing a unique opportunity to study the thermal and chemical modification of Earth's crust caused by the impact. The recovered core shows the crater hosted a spatially extensive hydrothermal system that chemically and mineralogically modified ~1.4 × 105 km3 of Earth's crust, a volume more than nine times that of the Yellowstone Caldera system. Initially, high temperatures of 300° to 400°C and an independent geomagnetic polarity clock indicate the hydrothermal system was long lived, in excess of 106 years. © 2020 American Association for the Advancement of Science. All rights reserved. 2020 10.1126/sciadv.aaz3053 Science Advances 6 Universities Space Research Association, Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, TX 77058, United States; Department of Earth and Planetary Sciences, Rutgers University New Brunswick, Piscataway Township, NJ 08854, United States; Institut fur Geologie, Universitat Hamburg, Bundesstrase 55, Hamburg, 20146, Germany; Departamento de Recursos Del Mar, CINVESTAV-MERIDA, Carret. Merida-Progreso, S/N, Merida, Yucatan, 97215, Mexico; Institute for Earth and Space Exploration and Department of Earth Sciences, University of Western Ontario, London, ON N6A 5B7, Canada; Institut Pour la Recherche et le Developpement, Aix Marseille Universite, CNRS, Coll France, INRA, Cerege, Aix-en-Provence, France; Eyring Materials Center, Arizona State University, Tempe, AZ 85287-8301, United States; Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, EH9 3FD, United Kingdom; WA-Organic and Isotope Geochemistry Centre (WA-OIGC), School of Earth and Planetary Sciences, Curtin University, Bentley, WA 6102, Australia; Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78758-4445, United States; Department of Earth Science and Engineering, Imperial College London, London, SW7 2AZ, United Kingdom; Department of Geosciences, Pennsylvania State UniversityPA 16802, United States; GeoRessources, Universite de Lorraine, Cnrs, Vandoeuvre-les-Nancy, 54 500, France; Analytical, Environmental and Geo-Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, Brussels, 1050, Belgium; Natural History Museum, Burgring 7, Vienna, 1010, Austria; Alfred Wegener Institute Helmholtz Centre of Polar and Marine Research, Bremerhaven, 27568, Germany; Department of Earth and Planetary Science, University of Tokyo, Hongo 7-3-1, Tokyo, 113-0033, Japan; British Geological Survey, Edinburgh, United Kingdom; Geosciences Montpellier, Universite de Montpellier, Montpellier Cedex 05, 34095, France; Groupe de Physico-Chimie de l'Atmosphere, L'Institut de Chimie et Procedes Pour l'Energie, L'Environnement et la Sante (ICPEES), Umr 7515 Universite de Strasbourg-CNRS, 1 rue Blessig, Strasbourg, 67000, France; Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, Cd. Universitaria, Coyoacan, Ciudad de Mexico, C. P. 04510, Mexico; School of Geographical and Earth Sciences, University of Glasgow, Gregory, Lilybank Gardens, Glasgow, G12 8QQ, United Kingdom; University of Freiburg, Geology, Albertstrase 23b, Freiburg, 79104, Germany; Department of Geology and Geophysics, University of Utah, 115 S 1460 E (FASB), Salt Lake City, UT 84112, United States; Ocean Resources Research Center for Next Generation, Chiba Institute of Technology, 2-17-1, Tsudanuma, Narashino-city, Chiba275-0016, Japan; Faculty of Earth and Life Sciences (FALW), Vrije Universiteit Amsterdam, de Boelelaan 1085, Amsterdam, 1018HV, Netherlands; Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, 200 Monobe Otsu, Nankoku, Kochi, 783-8502, Japan; Department of Geosciences, University of Alaska Fairbanks, 1930 Yukon Drive, Fairbanks, AK 99775, United States; Planetary Science Institute, School of Earth Sciences, China University of Geosciences (Wuhan), 388 Lumo Rd. Hongshan Dist., Wuhan, China; Department of Chemistry, Toho University, Funabashi, Chiba, 274-8510, Japan 22 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086355179&doi=10.1126%2fsciadv.aaz3053&partnerID=40&md5=ec98d66c05f8bd266193849788c99e8f cited By 49 D.A. Kring S.M. Tikoo M. Schmieder U. Riller M. Rebolledo-Vieyra S.L. Simpson G.R. Osinski J. Gattacceca A. Wittmann C.M. Verhagen C.S. Cockell M.J.L. Coolen F.J. Longstaffe S.P.S. Gulick J.V. Morgan T.J. Bralower E. Chenot G.L. Christeson P. Claeys L. Ferrière C. Gebhardt K. Goto S.L. Green H. Jones J. Lofi C.M. Lowery R. Ocampo-Torres L. Pérez-Cruz A.E. Pickersgill M.H. Poelchau A.S.P. Rae C. Rasmussen H. Sato J. Smit N. Tomioka J. Urrutia-Fucugauchi M.T. Whalen L. Xiao K.E. Yamaguchi article Pittarello20201082 Shocked quartz and feldspar grains commonly exhibit planar microstructures, such as planar fractures, planar deformation features, and possibly microtwins, which are considered to have formed by shock metamorphism. Their orientation and frequency are typically reported to be randomly distributed across a sample. The goal of this study is to investigate whether such microstructures are completely random within a given sample, or whether their orientation might also retain information on the direction of the local shock wave propagation. For this work, we selected samples of shatter cones, which were cut normal to the striated surface and the striation direction, from three impact structures (Keurusselkä, Finland, and Charlevoix and Manicouagan, Canada). These samples show different stages of pre-impact tectonic deformation. Additionally, we investigated several shocked granite samples, selected at different depths along the drill core recovered during the joint IODP-ICDP Chicxulub Expedition 364 (Mexico). In this case, thin sections were cut along two orthogonal directions, one parallel and one normal to the drill core axis. All the results refer to optical microscopy and universal-stage analyses performed on petrographic thin sections. Our results show that such shock-related microstructures do have a preferred orientation, but also that relating their orientation with the possible shock wave propagation is quite challenging and potentially impossible. This is largely due to the lack of dedicated experiments to provide a key to interpret the observed preferred orientation and to the lack of information on postimpact orientation modifications, especially in the case of the drill core samples. © 2020 The Authors. Meteoritics & Planetary Science published by Wiley Periodicals LLC on behalf of The Meteoritical Society (MET) 2020 10.1111/maps.13490 Meteoritics and Planetary Science 55 1082-1092 Natural History Museum Vienna, Burgring 7, Vienna, A-1010, Austria; Department of Lithospheric Research, University of Vienna, Althanstrasse 14, Vienna, A-1090, Austria; Department of Earth Sciences, University of Western Ontario, 1151 Richmond Street, London, ON N6A 5B7, Canada; Institute for Earth and Space Exploration, University of Western Ontario, 1151 Richmond Street, London, ON N6A 3K7, Canada 5 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085878809&doi=10.1111%2fmaps.13490&partnerID=40&md5=6fe7d790144d911c5696a5e4d3c36f86 cited By 7 L. Pittarello L. Ferrière J.-G. Feignon G.R. Osinski C. Koeberl article Heap2020 The physical properties and mechanical behaviour of impactites are an important parameter in fluid flow models and slope stability and landscape evolution assessments for heavily impacted planetary bodies. We first present porosity, permeability, Young's modulus, and uniaxial compressive strength measurements for three suevites from the Ries impact crater (Germany). Porosity ranges from 0.18 to 0.43, permeability from 5.8 × 10− 16 to 5.1 × 10− 14 m2, Young's modulus from 1.4 to 8.1 GPa, and uniaxial compressive strength from 7.3 to 48.6 MPa. To explore their mechanical behaviour, we performed triaxial deformation experiments on these samples at a range of confining pressures. The brittle–ductile transition for the lowest (0.25) and highest (0.38) porosity suevite samples was at a confining pressure of ~30 and ~10 MPa, respectively (corresponding to, for example, depths of ~1 and ~4 km on Mars, respectively). Microstructural observations show that the dominant deformation micromechanism during brittle deformation is microcracking, and during ductile deformation is distributed cataclastic pore collapse. We show that a theoretically grounded permeability model for welded granular media accurately captures the permeability of the studied suevites, and we use micromechanical models to glean insight as to their mechanical behaviour. Finally, we upscale our laboratory measurements to provide physical property values for length scales more relevant for large-scale models, and we compare these data with those for basalt (a lithology representative of the surface of the inner Solar System bodies). These analyses show how macroscopic fractures serve to increase the permeability and decrease the strength and Young's modulus of suevite and basalt. We also find, for example, that basalt can be a factor of 2–5 stronger than suevite in the shallow crust. Our study suggests, therefore, that the rock masses comprising older, bombarded crusts are substantially weaker and more porous and permeable than the younger plains material on these bodies. These findings should be considered in large-scale fluid flow modelling and when providing crustal strength estimates or slope stability assessments for planetary bodies on which protracted records of impact bombardment are preserved. © 2020 Elsevier Inc. 2020 10.1016/j.icarus.2020.113873 Icarus 349 Géophysique Expérimentale, Institut de Physique de Globe de Strasbourg (UMR 7516 CNRSUniversité de Strasbourg/EOST), 5 rue René Descartes, Strasbourg cedex, 67084, France; Lehrstuhl für Ingenieurgeologie, Technische Universität München, Munich, Germany; Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Raleigh, NC, United States; Department of Earth Sciences, Science Labs, Durham University, Durham, DH1 3LE, United Kingdom https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085599886&doi=10.1016%2fj.icarus.2020.113873&partnerID=40&md5=d1c6d7d3cb6c9e3b002692c1a832b571 cited By 3 M.J. Heap H.A. Gilg P.K. Byrne F.B. Wadsworth T. Reuschlé article Bralower2020 Microcrystalline calcite (micrite) dominates the sedimentary record of the aftermath of the Cretaceous–Paleogene (K–Pg) impact at 31 sites globally, with records ranging from the deep ocean to the Chicxulub impact crater, over intervals ranging from a few centimeters to more than seventeen meters. This micrite-rich layer provides important information about the chemistry and biology of the oceans after the impact. Detailed high-resolution scanning electron microscopy demonstrates that the layer contains abundant calcite crystals in the micron size range with a variety of forms. Crystals are often constructed of delicate, oriented agglomerates of sub-micrometer mesocrystals indicative of rapid precipitation. We compare the form of crystals with natural and experimental calcite to shed light on their origin. Close to the crater, a significant part of the micrite may derive from the initial backreaction of CaO vaporized during impact. In more distal sites, simple interlocking rhombohedral crystals resemble calcite precipitated from solution. Globally, we found unique calcite crystals associated with fossilized extracellular materials that strikingly resemble calcite precipitated by various types of bacteria in natural and laboratory settings. The micrite-rich layer contains abundant bacterial and eukaryotic algal biomarkers and most likely represents global microbial blooms initiated within millennia of the K–Pg mass extinction. Cyanobacteria and non-haptophyte microalgae likely proliferated as dominant primary producers in cold immediate post-impact environments. As surface-water saturation state rose over the following millennia due to the loss of eukaryotic carbonate producers and continuing river input of alkalinity, “whitings” induced by cyanobacteria replaced calcareous nannoplankton as major carbonate producers. We postulate that the blooms grew in supersaturated surface waters as evidenced by crystals that resemble calcite precipitates from solution. The microbial biomass may have served as a food source enabling survival of a portion of the marine biota, ultimately including life on the deep seafloor. Although the dominance of cyanobacterial and algal photosynthesis would have weakened the biological pump, it still would have removed sufficient nutrients from surface waters thus conditioning the ocean for the recovery of biota at higher trophic levels. © 2020 Elsevier B.V. 2020 10.1016/j.epsl.2020.116476 Earth and Planetary Science Letters 548 Department of Geosciences, Pennsylvania State University, University Park, PA 16802, United States; Department of Geosciences, Earth and Environmental Systems Institute, Pennsylvania State University, University Park, PA 16802, United States; Department of Earth Science and Engineering, Imperial College, London, United Kingdom; Department of Geology, The University of Kansas, Lawrence, KS 66045, United States; WA-Organic and Isotope Geochemistry Centre, The Institute for Geoscience Research, School of Earth and Planetary Science, Curtin University, Perth, WA, Australia; Institute of Geosciences, Friedrich-Schiller-University Jena, Burgweg 11, Jena, 07749, Germany; Earth and Planetary Sciences, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States; Planetary Science Institute, Tucson, AZ, United States; Institute for Geophysics, Dept. of Geological Sciences, Jackson School of Geosciences, Center for Planetary Systems Habitability, University of Texas at Austin, United States; Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, United States; Department of Geology and Geophysics, Yale University, New Haven, CT 06520, United States; Department of Earth & Environmental Sciences, Wesleyan University, Middletown, CT 06459, United States; Department of Palaeobiology, Swedish Museum of Natural History, Stockholm, Sweden https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089102470&doi=10.1016%2fj.epsl.2020.116476&partnerID=40&md5=1eb387da505f135a88234d62fe83d75d cited By 20 T.J. Bralower J. Cosmidis P.J. Heaney L.R. Kump J.V. Morgan D.T. Harper S.L. Lyons K.H. Freeman K. Grice J.E. Wendler J.C. Zachos N. Artemieva S.A. Chen S.P.S. Gulick C.H. House H.L. Jones C.M. Lowery C. Nims B. Schaefer E. Thomas V. Vajda article Lyons202025327 An asteroid impact in the Yucatán Peninsula set off a sequence of events that led to the Cretaceous-Paleogene (K-Pg) mass extinction of 76% species, including the nonavian dinosaurs. The impact hit a carbonate platform and released sulfate aerosols and dust into Earth's upper atmosphere, which cooled and darkened the planet - a scenario known as an impact winter. Organic burn markers are observed in K-Pg boundary records globally, but their source is debated. If some were derived from sedimentary carbon, and not solely wildfires, it implies soot from the target rock also contributed to the impact winter. Characteristics of polycyclic aromatic hydrocarbons (PAHs) in the Chicxulub crater sediments and at two deep ocean sites indicate a fossil carbon source that experienced rapid heating, consistent with organic matter ejected during the formation of the crater. Furthermore, PAH size distributions proximal and distal to the crater indicate the ejected carbon was dispersed globally by atmospheric processes. Molecular and charcoal evidence indicates wildfires were also present but more delayed and protracted and likely played a less acute role in biotic extinctions than previously suggested. Based on stratigraphy near the crater, between 7.5 × 1014and 2.5 × 1015g of black carbon was released from the target and ejected into the atmosphere, where it circulated the globe within a few hours. This carbon, together with sulfate aerosols and dust, initiated an impact winter and global darkening that curtailed photosynthesis and is widely considered to have caused the K-Pg mass extinction. © 2020 National Academy of Sciences. All rights reserved. 2020 10.1073/pnas.2004596117 Proceedings of the National Academy of Sciences of the United States of America 117 25327-25334 Department of Geosciences, Pennsylvania State University, University Park, PA 16802, United States; Western Australia Organic and Isotope Geochemistry Centre, School of Earth and Planetary Sciences, Institute for Geoscience Research, Curtin University, Perth, WA 6102, Australia; Institute for Geophysics, University of Texas at Austin, Austin, TX 78758, United States; Department of Geological Sciences, University of Texas at Austin, Austin, TX 78712, United States; Center for Planetary Systems Habitability, University of Texas at Austin, Austin, TX 78712, United States; Department of Earth Science and Engineering, Imperial College London, London, SW7 2AZ, United Kingdom 41 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85092914280&doi=10.1073%2fpnas.2004596117&partnerID=40&md5=a4ab4b648612480f4fe423fff4fa27fc cited By 24 S.L. Lyons A.T. Karp T.J. Bralower K. Grice B. Schaefer S.P.S. Gulick J.V. Morgan K.H. Freeman article Ebert2020814 The Chicxulub crater (Yucatan Peninsula, Mexico) is considered exceptional in many scientific aspects; morphologically it is the only known impact structure on Earth with a wellpreserved peak ring. Recent drilling (International Ocean Discovery Program-International Continental Scientific Drilling Program Expedition 364) into this topographic feature provides insights into the structural properties and complex formation of a peak ring. By means of U-stage microscopy on shocked quartz grains from the granitic section of the recovered drill core, orientations of feather features (FFs) were determined and local principal axis of stress (σ1) orientations of the shock wave were derived. The FF orientations are strongly confined to a radially outward trend (WNW) relative to the crater center, which emphasizes a link between FF formation and the direction of shock-wave propagation. Thus, FFs represent an excellent tool as a stress-orientation indicator for the shock wave. Our microstructural data set shows that the granitic basement of the peak ring between ~750 and ~1200 m below seafloor behaved as a semi-coherent block above an imbricate thrust zone, and underwent both rotation and local folding during cratering. This validates the block sizes of acoustic fluidization employed in most Chicxulub-scale impact simulations. The folding of the upper part of the granitic basement may have developed by either (1) compression of the crater wall at the transient cavity and/or (2) dragging by the centripetal flow of the overlying crater material. © 2020 Geological Society of America. 2020 10.1130/G47129.1 Geology 48 814-818 Department of Geology, University of Freiburg, Albertstraße 23b, Freiburg, 79104, Germany 8 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089438030&doi=10.1130%2fG47129.1&partnerID=40&md5=c479ce75d7045d2f280a6cc11bc85173 cited By 5 M. Ebert M.H. Poelchau T. Kenkmann B. Schuster article Osinski2020108 The impact of asteroids and comets with planetary surfaces is one of the most catastrophic, yet ubiquitous, geological processes in the solar system. The Chicxulub impact event, which has been linked to the Cretaceous-Paleogene (K-Pg) mass extinction marking the beginning of the Cenozoic Era, is arguably the most significant singular geological event in the past 100 million years of Earth's history. The Chicxulub impact occurred in a marine setting. How quickly the seawater re-entered the newly formed basin after the impact, and its effects of it on the cratering process, remain debated. Here, we show that the explosive interaction of seawater with impact melt led to molten fuel-coolant interaction (MFCI), analogous to what occurs during phreatomagmatic volcanic eruptions. This process fractured and dispersed the melt, which was subsequently deposited subaqueously to form a series of well-sorted deposits. These deposits bear little resemblance to the products of impacts in a continental setting and are not accounted for in current classification schemes for impactites. The similarities between these Chicxulub deposits and the Onaping Formation at the Sudbury impact structure, Canada, are striking, and suggest that MFCI and the production of volcaniclastic-like deposits is to be expected for large impacts in shallow marine settings. © 2019 Geological Society of America. 2020 10.1130/G46783.1 Geology 48 108-112 Department of Earth Sciences, University of Western Ontario, London, ON N6A 5B7, Canada; Institute for Earth and Space Exploration, University of Western Ontario, London, ON N6A 5B7, Canada; School of Physics and Astronomy, University of Edinburgh, Edinburgh, EH9 3FD, United Kingdom; Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, Texas, 78758, United States; Department of Geology, Universität Freiburg, Freiburg, 79085, Germany; Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78758, United States; Departments of Earth, Atmospheric, and Planetary Sciences, and Physics and Aerospace Engineering, Purdue University, West Lafayette, IN 47907, United States; Institute of Geology, Universität Hamburg, Hamburg, 20146, Germany; Department of Geophysics, Stanford University, Stanford, CA 95305, United States; Eyring Materials Center, Arizona State University, Tempe, AZ 85287, United States 2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85079774039&doi=10.1130%2fG46783.1&partnerID=40&md5=a44ef4b2ecea1068d95428dd5ab30eb0 cited By 21 G.R. Osinski R.A.F. Grieve P.J.A. Hill S.L. Simpson C. Cockell G.L. Christeson M. Ebert S. Gulick H.J. Melosh U. Riller S.M. Tikoo A. Wittmann article Cox2020 2020 10.1111/maps.13541 Meteoritics and Planetary Science 55 Space Science and Technology Centre (SSTC), School of Earth and Planetary Science, Curtin University, Perth, WA 6102, Australia; Lunar and Planetary Institute (LPI)—USRA, 3600 Bay Area Boulevard, Houston, TX 77058, United States; Jacobs-JETS, Astromaterials Research and Exploration Science Division, NASA Johnson Space Center, Houston, TX 77058, United States; United States; United Kingdom; France; Belgium; Australia; Austria; Germany; Japan; Mexico; Netherlands; China 8 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85088926758&doi=10.1111%2fmaps.13541&partnerID=40&md5=7587801cade0a9fed2b6e7658ce3fe1d cited By 12 M.A. Cox T.M. Erickson M. Schmieder R. Christoffersen D.K. Ross A.J. Cavosie P.A. Bland D.A. Kring S. Gulick J.V. Morgan G. Carter E. Chenot G. Christeson P. Claeys C. Cockell M.J.L. Coolen L. Ferrière C. Gebhardt K. Goto H. Jones J. Lofi C. Lowery R. Ocampo-Torres L. Pérez-Cruz A. Pickersgill M. Poelchau A. Rae C. Rasmussen M. Rebolledo-Vieyra U. Riller H. Sato J. Smit S. Tikoo N. Tomioka M. Whalen A. Wittmann J. Urrutia-Fucugauchi L. Xiao K.E. Yamaguchi IODP-ICDP Expedition 364 Scientists article Feignon20202206 Planar deformation features (PDFs) in quartz are a commonly used and well-documented indicator of shock metamorphism in terrestrial rocks. The measurement of PDF orientations provides constraints on the shock pressure experienced by a rock sample. A total of 963 PDF sets were measured in 352 quartz grains in 11 granite samples from the basement of the Chicxulub impact structure’s peak ring (IODP-ICDP Expedition 364 drill core), with the aim to quantify the shock pressure distribution and a possible decay of the recorded shock pressure with depth, in the attempt to better constrain shock wave propagation and attenuation within a peak ring. The investigated quartz grains are highly shocked (99.8% are shocked), with an average of 2.8 PDF sets per grain; this is significantly higher than in all previously investigated drill cores recovered from Chicxulub and also for most K-Pg boundary samples (for which shocked quartz data are available). PDF orientations are roughly homogenous from a sample to another sample and mainly parallel to {10 (Formula presented.) 3} and {10 (Formula presented.) 4} orientations (these two orientations representing on average 68.6% of the total), then to {10 (Formula presented.) 2} orientation, known to form at higher shock pressure. Our shock pressure estimates are within a narrow range, between ~16 and 18 GPa, with a slight shock attenuation with increasing depth in the drill core. The relatively high shock pressure estimates, coupled with the rare occurrence of basal PDFs, i.e., parallel to the (0001) orientation, suggest that the granite basement in the peak ring could be one of the sources of the shocked quartz grains found in the most distal K-Pg boundary sites. © 2020 The Authors. Meteoritics & Planetary Science published by Wiley Periodicals LLC on behalf of The Meteoritical Society (MET) 2020 10.1111/maps.13570 Meteoritics and Planetary Science 55 2206-2223 Department of Lithospheric Research, University of Vienna, Althanstrasse 14, Vienna, A-1090, Austria; Natural History Museum, Burgring 7, Vienna, A-1010, Austria; Univ-Lille, CNRS, INRAE, Centrale Lille, UMR 8207 – UMET – Unité Matériaux et transformations, Villeneuve d'Ascq, 59655, France 10 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85091786850&doi=10.1111%2fmaps.13570&partnerID=40&md5=88b9ed7c55daad7634052fe26b2c905a cited By 11 J.-G. Feignon L. Ferrière H. Leroux C. Koeberl article 10.1130/G46799.1 {The Chicxulub crater was formed by an asteroid impact at ca. 66 Ma. The impact is considered to have contributed to the end-Cretaceous mass extinction and reduced productivity in the world’s oceans due to a transient cessation of photosynthesis. Here, biomarker profiles extracted from crater core material reveal exceptional insights into the post-impact upheaval and rapid recovery of microbial life. In the immediate hours to days after the impact, ocean resurge flooded the crater and a subsequent tsunami delivered debris from the surrounding carbonate ramp. Deposited material, including biomarkers diagnostic for land plants, cyanobacteria, and photosynthetic sulfur bacteria, appears to have been mobilized by wave energy from coastal microbial mats. As that energy subsided, days to months later, blooms of unicellular cyanobacteria were fueled by terrigenous nutrients. Approximately 200 k.y. later, the nutrient supply waned and the basin returned to oligotrophic conditions, as evident from N2-fixing cyanobacteria biomarkers. At 1 m.y. after impact, the abundance of photosynthetic sulfur bacteria supported the development of water-column photic zone euxinia within the crater.} 2020 01 0091-7613 10.1130/G46799.1 Geology 48 328-332 4 https://doi.org/10.1130/G46799.1 Bettina Schaefer Kliti Grice Marco J.L. Coolen Roger E. Summons Xingqian Cui Thorsten Bauersachs Lorenz Schwark Michael E. Böttcher Timothy J. Bralower Shelby L. Lyons Katherine H. Freeman Charles S. Cockell Joanna V. Morgan Michael T. Whalen Christopher M. Lowery Vivi Vajda article Collins2020 The environmental severity of large impacts on Earth is influenced by their impact trajectory. Impact direction and angle to the target plane affect the volume and depth of origin of vaporized target, as well as the trajectories of ejected material. The asteroid impact that formed the 66 Ma Chicxulub crater had a profound and catastrophic effect on Earth’s environment, but the impact trajectory is debated. Here we show that impact angle and direction can be diagnosed by asymmetries in the subsurface structure of the Chicxulub crater. Comparison of 3D numerical simulations of Chicxulub-scale impacts with geophysical observations suggests that the Chicxulub crater was formed by a steeply-inclined (45–60° to horizontal) impact from the northeast; several lines of evidence rule out a low angle (<30°) impact. A steeply-inclined impact produces a nearly symmetric distribution of ejected rock and releases more climate-changing gases per impactor mass than either a very shallow or near-vertical impact. © 2020, The Author(s). 2020 10.1038/s41467-020-15269-x Nature Communications 11 Department Earth Science and Engineering, Imperial College London, London, SW7 2AZ, United Kingdom; Institute of Geology, University of Freiburg, Freiburg, 79104, Germany; Institute for Geophysics and Department of Geological Sciences, University of Texas at Austin, Austin, TX 78758, United States; Institute for Geophysics, University of Texas at Austin, Austin, TX, United States; Laboratoire GeoRessources, Université de Lorraine, Vandoeuvre-lés-Nancy, France; Analytical, Environmental and Geochemistry, Vrije Universiteit Brussel, Brussels, Belgium; UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom; Western Australia Organic and Isotope Geochemistry Centre, School of Earth and Planetary Sciences, Curtin University, Bentley, WA 6102, Australia; Natural History Museum, Vienna, Austria; Alfred Wegener Institute Helmholtz Centre of Polar and Marine Research, Bremerhaven, Germany; Department of Earth and Planetary Science, University of Tokyo, Tokyo, Japan; Department of Geosciences, Pennsylvania State University, University Park, PA, United States; Lunar and Planetary Institute, Houston, TX, United States; Géosciences Montpellier, CNRS, Université de Montpellier, Montpellier, France; Groupe de Physico-Chimie de l’Atmosphère, L’Institut de Chimie et Procédés pour l’Énergie, l’Environnement et la Santé, Université de Strasbourg, Strasbourg, France; Instituto de Geofísica, Universidad Nacional Autónoma De México, Ciudad De México, Mexico; School of Geographical and Earth Sciences, University of Glasgow, Glasgow, United Kingdom; Argon Isotope Facility, Scottish Universities Environmental Research Centre, East Kilbride, United Kingdom; Department of Geology and Geophysics, University of Utah, Salt Lake City, UT, United States; Unidad de Ciencias del Agua, Mérida, Mexico; Institut für Geologie, Universität Hamburg, Hamburg, Germany; Japan Agency for Marine-Earth Science and Technology, Kanagawa, Japan; Faculty of Earth and Life Sciences, Vrije Universiteit Amsterdam, Amsterdam, Netherlands; Department of Earth and Planetary Sciences, Rutgers University, Piscataway Township, NJ, United States; Department of Geophysics, Stanford University, Stanford, CA, United States; Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, Kochi, Japan; Department of Geosciences, University of Alaska Fairbanks, Fairbanks, AK, United States; Eyring Materials Center, Arizona State University, Tempe, AZ, United States; School of Earth Sciences, Planetary Science Institute, China University of Geosciences, Wuhan, China; Department of Chemistry, Toho University, Funabashi, Chiba, Japan; NASA Astrobiology Institute, Mountain View, CA, United States; Planetary Science Institute, Tucson, AZ, United States 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085513257&doi=10.1038%2fs41467-020-15269-x&partnerID=40&md5=6b7520fd50e30e75f10f8f3affe95b2b cited By 40 G.S. Collins N. Patel T.M. Davison A.S.P. Rae J.V. Morgan S.P.S. Gulick G.L. Christeson E. Chenot P. Claeys C.S. Cockell M.J.L. Coolen L. Ferrière C. Gebhardt K. Goto H. Jones D.A. Kring J. Lofi C.M. Lowery R. Ocampo-Torres L. Pérez-Cruz A.E. Pickersgill M.H. Poelchau C. Rasmussen M. Rebolledo-Vieyra U. Riller H. Sato J. Smit S.M. Tikoo N. Tomioka J. Urrutia-Fucugauchi M.T. Whalen A. Wittmann L. Xiao K.E. Yamaguchi N. Artemieva T.J. Bralower IODP-ICDP Expedition 364 Science Party Third-Party Scientists article Zhao2020128 The Late Paleozoic tectono–magmatic history and basement of the Maya block are poorly understood due to the lack of exposures of coeval magmatic rocks in the region. Recently, IODP–ICDP Expedition 364 recovered drill core samples at borehole M0077A from the peak ring of the Chicxulub impact crater, offshore of the Yucatán peninsula in the Gulf of México, have been studied comprehensively. In the lowermost ~600 m of the drill core, impact–deformed granitoids, and minor felsite and dolerite dykes are intercalated with impact melts and breccias. Zircon U-Pb dating of granitoids yielded ages of around 326 ± 5 Ma, representing the first recovery of Late Paleozoic magmatic rocks from the Maya block, which could be genetically related to the convergence of Laurentia and Gondwana. The granitoids show the features of high K2O/Na2O, LaN/YbN and Sr/Y ratios, but very low Yb and Y contents, indicating an adakitic affinity. They are also characterized by slightly positive ԑNd(326Ma) of 0.17–0.68, intermediate initial 87Sr/86Sr(326Ma) of 0.7036–0.7047 and two–stage Nd model age (TDM2) of 1027–1069 Ma, which may indicate a less evolved crustal source. Thus, the adakitic granitoids were probably generated by partial melting of thickened crust, with source components similar to Neoproterozoic metagabbro in the Carolina block (Pan–African Orogeny materials) along Peri–Gondwana. Felsite dykes are shoshonitic with typical continental arc features that are sourced from a metasomatic mantle wedge by slab–fluids. Dolerite dykes display OIB–type features such as positive Nb and Ta anomalies and low ThNpm/NbNpm. In our interpretation, the Chicxulub adakitic granitoids of this study are formed by crustal anatexis due to asthenospheric upwelling resulting from slab breakoff. Through comparing sources and processes of Late Paleozoic magmatism along the Peri–Gondwanan realm, a tearing slab breakoff model may explain the discontinuous magmatism that appears to have occurred during the convergence of Laurentia and Gondwana. © 2020 International Association for Gondwana Research 2020 10.1016/j.gr.2019.12.003 Gondwana Research 82 128-150 State Key Laboratory of Geological Processes and Mineral Resources, Planetary Science Institute, School of Earth Sciences, China University of Geosciences, Wuhan, China; State Key Laboratory of Space Science Institute, Lunar and Planetary Science, Macau university of Science and Technology, Taipa, Macau, China; Institute for Geophysics, Jackson School of Geosciences, University of Texas at AustinTX 78758-4445, United States; Department of Earth Science and Engineering, Imperial College London, London, SW7 2BP, United Kingdom; Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, TX 77058, United States; Instituto de Geofisica, Universidad Nacional Autónoma de México, México D.F., Mexico; Analytical, Environmental and Geo–Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, Elsene, 1050, Belgium; Eyring Materials Center for Solid State Science, Physical Sciences, Arizona State University, Tempe, AZ 85287–8301, United States; School of Geographical and Earth Sciences, University of Glasgow, Gregory, Lilybank Gardens, Glasgow, G12 8QQ, United Kingdom; University of Utah, Department of Geology and Geophysics, 115 S 1460 E (FASB), Salt Lake City, UT 84112, United States; Department of Palaeobiology, Swedish Museum of Natural History, Stockholm, Sweden; Natural History Museum, Burgring 7, Vienna, 1010, Austria; Department of Lithospheric Research, University of Vienna, Althanstrasse 14, Vienna, A–1090, Austria; Biogéosciences, UMR 6282, CNRS, University of Bourgogne Franche–Comté, 6 boulevard Gabriel, Dijon, F–21000, France; Instituto de Geofísica, Universidad Nacional Autónoma de México, Cd. Universitaria, Coyoacán Ciudad de México, C. P. 04510, Mexico; Japan Agency for Marine–Earth Science and Technology, 2–15, Natsushima–cho, Yokosuka–city, Kanagawa 237–0061, Japan; Department of Chemistry, Toho University, Funabashi, Chiba, 274–8510, Japan; NERC Argon Isotope Facility, Scottish Universities Environmental Research Centre (SUERC), Rankine Avenue, East Kilbride G75 0QF, United Kingdom https://www.scopus.com/inward/record.uri?eid=2-s2.0-85079391651&doi=10.1016%2fj.gr.2019.12.003&partnerID=40&md5=1316c93044e567c4e04b8e4e9f4363b7 cited By 23 J. Zhao L. Xiao S.P.S. Gulick J.V. Morgan D. Kring J.U. Fucugauchi M. Schmieder S.J. Graaff A. Wittmann C.H. Ross P. Claeys A. Pickersgill P. Kaskes S. Goderis C. Rasmussen V. Vajda L. Ferrière J.-G. Feignon E. Chenot L. Pérez-Cruz H. Sato K. Yamaguchi IODP-ICDP Expedition 364 Scientists article Dorfler2020441 Depending on their sizes, impact craters have either simple or complex geometries. Peak-ring craters such as the Chicxulub impact structure possess a single interior ring of peaks and hills and a flat interior floor. The exact mechanisms leading to the formation of a morphological peak-ring are still a matter of debate. In this study, analog modeling was used to study the flow field of a collapsing central uplift. A 3-D-printed cast was used to bring the analog material in the shape of an overheightened central uplift that was based on numerical modeling. The cast was then quickly removed and the central peak collapsed, forming a flattened broad mound that spread out onto the annular moat of the crater cavity. A subwoofer was used to fluidize the granular target material. The kinematics of the collapse were analyzed with the aid of particle image velocimetry, revealing a downward and outward collapse of the central uplift. This mode of collapse is partly in agreement with numerical models, in particular for the initial and middle phases. The overthrusting of the collapsing central peak onto the inward moving crater floor predicted by numerical modeling was observed, though to a lesser degree. A peak-ring, however, could not be reproduced since the collapse came to a halt before the central peak was completely leveled. Nevertheless, the method provides qualitative insights into the kinematics of collapse phenomena. This experimental study provides independent support of the theory of acoustic fluidization, in addition to numerical simulations. © 2020 The Authors. Meteoritics & Planetary Science published by Wiley Periodicals, Inc. on behalf of The Meteoritical Society (MET) 2020 10.1111/maps.13442 Meteoritics and Planetary Science 55 441-456 Institut für Geo- und Umweltnaturwissenschaften, Geologie, Albert-Ludwigs-Universität Freiburg, Albertstrasse 23-B, Freiburg, 79104, Germany 2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85079047705&doi=10.1111%2fmaps.13442&partnerID=40&md5=6c9fd4bfe65a0e1131c1f44b254ed06a cited By 2 M.A. Dörfler T. Kenkmann conference Nixon2020 Anomalous values of in-situ compressional wave speeds (VP) and quality factors (Q), determined from analysis of borehole seismic measurements are found within the highly damaged rock mass in the peak ring materials of the K-Pg Chicxulub impact structure. The data is obtained from vertical seismic profiling of IODP/ICDP hole M0077A, drilled to 1335 m depth. VP, calculated by local slope regression, are ~4 km/s, only about 60% that for similar unshocked polycrystalline granite. Attenuation is quantified using the spectral ratios method that gives low Q factors of 10 to 35, values that are significantly less than expected for unshocked granites. Previous in-situ studies measuring physical properties of complex crater central uplifts remain rare; the extraordinary geo-mechanical results from these analyses are presented as impetus for future studies on the poorly understood physical properties and formation of impact basin peak rings as well as providing insight into seismic wave propagation through highly damaged rock masses. © 2020 ARMA, American Rock Mechanics Association 2020 54th U.S. Rock Mechanics/Geomechanics Symposium University of Alberta, Edmonton, AB, Canada; Purdue University, West Lafayette, IN, United States; University of Texas Institute for Geophysics, Austin, TX, United States; Université de Montpellier, Montpellier, Languedoc-Roussillon, France; Imperial College London, London, United Kingdom https://www.scopus.com/inward/record.uri?eid=2-s2.0-85097945980&partnerID=40&md5=8bae17c025d401e4a81952b079df529a cited By 0 C.G. Nixon R. Kofman S.P.S. Gulick G.L. Christeson S. Saustrup J. Lofi J.V. Morgan article Scheller2020 The western part of the Isidis basin structure hosts a well-characterized Early Noachian to Amazonian stratigraphy. The Noachian Basement comprises its oldest exposed rocks (Early to Mid-Noachian) and was previously considered a single low-Ca pyroxenes (LCP)- and Fe/Mg-smectite-bearing unit. Here, we divide the Noachian Basement Group into five distinct geological units (Stratified Basement Unit, Blue Fractured Unit, Mixed Lithology Plains Unit, LCP-bearing Plateaus Unit, and Fe/Mg-smectite-bearing Mounds Unit), two geomorphological features (megabreccia and ridges), and a mineral deposit (kaolinite-bearing bright materials), based on geomorphology, spectral characteristics, and stratigraphic relationships. Megabreccia contain four different pre-Isidis lithologies, possibly including deeper crust or mantle materials, formed through mass wasting associated with transient crater collapse during Isidis basin formation. The Fe/Mg-smectite-bearing Stratified Basement Unit and LCP-bearing Blue Fractured Unit likewise represent pre-Isidis units within the Noachian Basement Group. Multiple Fe/Mg-smectite-bearing geological units with different stratigraphic positions and younger kaolinite-bearing bright materials indicate several aqueous alteration episodes of different ages and styles. Units with slight changes in pyroxene spectral properties suggest a transition from low-Ca pyroxene-containing materials to those with higher proportions of pyroxenes higher in Ca and/or glass that could be related to different impact and/or igneous processes, or provenance. This long history of Noachian and potentially Pre-Noachian geological processes, including impact basin formation, aqueous alteration, and multiple igneous and sedimentary petrogeneses, records changing ancient Mars environmental conditions. All units defined by this study are available 20 km outside of Jezero crater for in situ analysis and sampling during a potential extended mission scenario for the Mars 2020 rover. ©2020. The Authors. 2020 10.1029/2019JE006190 Journal of Geophysical Research: Planets 125 Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, United States; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States 7 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85088599065&doi=10.1029%2f2019JE006190&partnerID=40&md5=8fb5bf285b0909d7eb2496ff748f8217 cited By 16 E.L. Scheller B.L. Ehlmann article Jacob2020 We have investigated the laboratory-scale, high-strain rate tensile failure processes responsible for Mode-I breccia dike formation in impact structures. Brazilian disc experiments with granite (isotropic) and gneiss (foliated) samples were performed on a Split Hopkinson Pressure Bar, equipped with high-speed photography. For the gneiss samples, the gneissic foliation was oriented (θ) at 0, 45 and 90° to the compression direction. Time-series images show the transient states of tensile rupture localization and propagation, leading to in situ fragmentation of the rocks. Granite samples produced a single incipient tensile rupture, accommodating pulverized clasts, whereas the gneisses underwent failure by way of major fracture and a network of secondary tensile fractures, forming large elongate clasts. For gneisses, θ greatly influenced the secondary crack growth, forcing propagation trajectories to orient preferentially either along or across the foliation. The two types of target rocks produced contrasting clast geometry in the fracture zones. The granite had mostly small clasts (<10 mm), with average aspect ratios around 1:2, whereas the gneisses produced larger clasts (<40 mm) with aspect ratios, 1:5, 1:4 and 1:4 for θ = 0, 45 and 90°, respectively. This study demonstrates that monomict breccia dikes could form in situ, rather than by a tensile dilation followed by infilling. © 2020 Elsevier Ltd 2020 10.1016/j.jsg.2020.104148 Journal of Structural Geology 140 Department of Earth Sciences, IIT, Kanpur, Uttar Pradesh 208016, India; Department of Mechanical Engineering, IIT, Kanpur, Uttar Pradesh 208016, India; Department of Geological Sciences, Jadavpur University, Kolkata, 700032, India https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089277522&doi=10.1016%2fj.jsg.2020.104148&partnerID=40&md5=368e1a1b5744e99f331f95fc4b335b4d cited By 1 B.J. Jacob S. Misra V. Parameswaran N. Mandal article Harms2020 2020 10.1007/978-3-030-10475-7_195-1 Encyclopedia of Earth Sciences Series PartF4 Scientific Drilling, German Research Centre for Geosciences GFZ, Potsdam, Germany; Department of Earth and Space Sciences, University of Washington, Seattle, WA, United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-85133938650&doi=10.1007%2f978-3-030-10475-7_195-1&partnerID=40&md5=e6fbf8ccf08e216e65cd1d69f73ab68d cited By 0 U. Harms H. Tobin article Kletetschka2020 Chicxulub impact (66 Ma) event resulted in deposition of spheroids and melt glass, followed by deposition of diamectite and carbonate ejecta represented by large polished striated rounded pebbles and cobbles, henceforth, called Albion Formation1 Pook’s Pebbles, name given from the first site identified in central Belize, Cayo District. Here we report that magnetic analysis of the Pook’s Pebbles samples revealed unique electric discharge signatures. Sectioning of Pook’s Pebbles from the Chicxulub ejecta from the Albion Formation at Belize showed that different parts of Pook’s Pebbles had not only contrasting magnetization directions, but also sharply different level of magnetizations. Such behavior is indicative of electric discharge taking place sometimes during the formation of the Chicxulub ejecta blanket. In addition, some of the Pook’s Pebbles’ surface had recrystallized down to 0.2 mm depth. This is evidence of localized extreme pressures and temperatures during the fluidized ejecta formation which was imprinted in the outer layer of Pook’s Pebbles. Recrystallization caused formation of nanophase iron along the surface, which was revealed by mapping of both natural remanent magnetization and of saturation remanence magnetization signatures. While the spheroids’ magnetization orientation is consistent with reversed magnetic field at the time of impact, the study of the Pook’s Pebbles provided, in addition, new evidence of electric charging during the vapor plume cloud processes. © 2020, The Author(s). 2020 10.1038/s41598-020-65974-2 Scientific Reports 10 Institute of Geology, Czech Academy of Sciences, Rozvojová 269, Prague 6, 16500, Czech Republic; Department of Applied Geophysics, Charles University, Albertov 6, Prague 2, 12843, Czech Republic; Geophysical Institute, University of Alaska, Fairbanks, 903 N Koyukuk Drive, Fairbanks, AK, United States; NASA Headquarters, Washington, DC 20546, United States; Department of Infectious Diseases, Virology, University of Heidelberg, Heidelberg, Germany 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086007779&doi=10.1038%2fs41598-020-65974-2&partnerID=40&md5=a2b93c9d8ea0960b526302690fbcf10b cited By 6 G. Kletetschka A. Ocampo Uria V. Zila T. Elbra article Navarro2020 A plume of vaporized sediments and basement rocks was ejected to the top of atmosphere when a 10–15 km asteroid impacted on Yucatan in the Southern Gulf of Mexico about 66 million years ago. The Chicxulub impact-vapor plume emitted a flash of light that had clues on the chemistry and degree of vaporization of the target surface material. Here we simulate the asteroid impact by vaporizing marine carbonate sediments cored in the Yaxcopoil-1 borehole in the Chicxulub crater using an intense infrared laser pulse. We investigate two sedimentary layers that represent the most dominant mineral phases of the target sequence: carbonates and sulfates. Their main constituents are 86% calcite and 74% anhydrite, respectively. The laser-induced vapor plumes were produced from each layer in a background simulated late Cretaceus atmosphere (0.16% CO2, 30% O2, and 69.84% N2). Time-resolved spectroscopic analyses from the laser-induced plumes were carried out using experimental and synthetic spectra. The vapor plumes had similar temperatures (≥7800 K) at 1 μs and their spectra showed similar emissions. The spectra contained the following lines in nm: Ca+ (mostly at 393.4 and 396.9 with less prominence at 370.6 and 373.7), Ca (422.7, 430.3, 443.6, 445.5, 527.0, 560.3, 616.4, and 657.3), N (746.8 and 821.6), O (777.7), and C (794.5). Molecular bands were not conspicuous which indicated complete vaporization of the target material by the laser pulse. The contribution of the granitic basement was examined using synthetic spectra. The expected emissions according to their intensities are: Na (589.6), Ca+ (393.4), Al (396.2, 309.3), Ca+ (396.9), Ca (422.7), Na (819.5) and K (766.5, 769.9). The results suggest that the emission corresponded to Ca+ and Ca originated mostly from the volatilization of the marine sediments, and Na, Al, and K from the basement rocks. The physico-chemical evolution of the Chicxulub impact-vapor plume could be deduced by deciphering the temperature and electron density from the emission lines of Ca and Ca+. These physical parameters can be used in gas dynamic models to predict the fluxes and nature of gases, vapors and mineral phases that were introduced into the atmosphere and better assess their impact to the environment and the biosphere. © 2020 Elsevier Inc. 2020 10.1016/j.icarus.2020.113813 Icarus 346 Posgrado en Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Avenida Ciudad Universitaria 3000, Ciudad de México, Coyoacán C.P. 04510, Mexico; Programa Universitario de Perforaciones en Océanos y Continentes, Instituto de Geofísica, Universidad Nacional Autónoma de México, Ciudad Universitaria, Ciudad de México, Coyoacán C.P. 04510, Mexico; Laboratorio de Química de Plasmas y Estudios Planetarios, Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Ciudad de México, Coyoacán C.P. 04510, Mexico; Laboratorio de Fotofísica y Películas Delgadas, Instituto de Ciencias Aplicadas y Tecnología, Universidad Nacional Autónoma de México, Ciudad Universitaria, Ciudad de México, Coyoacán C.P. 04510, Mexico; Laboratorio de Difracción de Rayos X and Laboratorio Nacional de Geoquímica y Mineralogía, Instituto de Geología, Universidad Nacional Autónoma de México, Ciudad Universitaria, Ciudad de México, Coyoacán C.P. 04510, Mexico https://www.scopus.com/inward/record.uri?eid=2-s2.0-85084039851&doi=10.1016%2fj.icarus.2020.113813&partnerID=40&md5=af6bc22e6b517b3cdb6b8d2bda783489 cited By 2 K.F. Navarro J. Urrutia-Fucugauchi M. Villagran-Muniz C. Sánchez-Aké T. Pi-Puig L. Pérez-Cruz R. Navarro-González article Veneranda2020349 In the present work, near-infrared, laser-induced breakdown spectroscopy, Raman, and X-ray diffractometer techniques have been complementarily used to carry out a comprehensive characterization of a terrestrial analogue selected from the Chesapeake Bay impact structure (CBIS). The obtained data clearly highlight the key role of Raman spectroscopy in the detection of minor and trace compounds, through which inferences about geological processes occurred in the CBIS can be extrapolated. Beside the use of commercial systems, further Raman analyses were performed by the Raman laser spectrometer (RLS) ExoMars Simulator. This instrument represents the most reliable tool to effectively predict the scientific capabilities of the ExoMars/Raman system that will be deployed on Mars in 2021. By emulating the analytical procedures and operational restrictions established by the ExoMars mission rover design, it was proved that the RLS ExoMars Simulator can detect the amorphization of quartz, which constitutes an analytical clue of the impact origin of craters. Beside amorphized minerals, the detection of barite and siderite, compounds crystallizing under hydrothermal conditions, helps indirectly to confirm the presence of water in impact targets. Furthermore, the RLS ExoMars Simulator capability of performing smart molecular mappings was successfully evaluated. © Copyright 2020, Mary Ann Liebert, Inc., publishers 2020. 2020 10.1089/ast.2019.2095 Astrobiology 20 349-363 CSIC-CAB Associated Unit Erica, Department of Condensed Matter Physics, University of Valladolid, Boecillo, Spain; Department of Analytical Chemistry, University of the Basque Country (UPV/EHU), Leioa, Spain; Institut d'Astrophysique Spatiale, CNRS/Université Paris-Sud, Orsay, France; Department of Geosciences, CEED/GEO, University of Oslo, Oslo, Norway 3 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85081146972&doi=10.1089%2fast.2019.2095&partnerID=40&md5=b49739d9a3dfb978a78b45348cbcff03 cited By 14 M. Veneranda G. Lopez-Reyes J.A. Manrique J. Medina P. Ruiz-Galende I. Torre-Fdez K. Castro C. Lantz F. Poulet H. Dypvik S.C. Werner F. Rull article 10.1130/G46783.1 {The impact of asteroids and comets with planetary surfaces is one of the most catastrophic, yet ubiquitous, geological processes in the solar system. The Chicxulub impact event, which has been linked to the Cretaceous-Paleogene (K-Pg) mass extinction marking the beginning of the Cenozoic Era, is arguably the most significant singular geological event in the past 100 million years of Earth’s history. The Chicxulub impact occurred in a marine setting. How quickly the seawater re-entered the newly formed basin after the impact, and its effects of it on the cratering process, remain debated. Here, we show that the explosive interaction of seawater with impact melt led to molten fuel–coolant interaction (MFCI), analogous to what occurs during phreatomagmatic volcanic eruptions. This process fractured and dispersed the melt, which was subsequently deposited subaqueously to form a series of well-sorted deposits. These deposits bear little resemblance to the products of impacts in a continental setting and are not accounted for in current classification schemes for impactites. The similarities between these Chicxulub deposits and the Onaping Formation at the Sudbury impact structure, Canada, are striking, and suggest that MFCI and the production of volcaniclastic-like deposits is to be expected for large impacts in shallow marine settings.} 2019 11 0091-7613 10.1130/G46783.1 Geology 48 108-112 2 https://doi.org/10.1130/G46783.1 Gordon R. Osinski Richard A.F. Grieve Patrick J.A. Hill Sarah L. Simpson Charles Cockell Gail L. Christeson Matthias Ebert Sean Gulick H. Jay Melosh Ulrich Riller Sonia M. Tikoo Axel Wittmann article Urrutia-Fucugauchi201968 The IODP-ICDP Expedition 364 drilled into the Chicxulub crater, peering inside its well-preserved peak ring. The borehole penetrated a sequence of post-impact carbonates and a unit of suevites and clast-poor impact melt rock at the top of the peak ring. Beneath this sequence, basement rocks cut by pre-impact and impact dykes, with breccias and melt, were encountered at shallow depths. The basement rocks are fractured, shocked and uplifted, consistent with dynamic collapse, uplift and long-distance transport of weakened material during collapse of the transient cavity and final crater formation. © 2019 John Wiley & Sons Ltd, The Geologists' Association & The Geological Society of London 2019 10.1111/gto.12261 Geology Today 35 68-72 Universidad Nacional Autonoma de Mexico, Mexico; Coordinacion Plataformas Oceanograficas, UNAM, Mexico; Imperial College London, United Kingdom; University of Texas at Austin, United States; Arizona State University, United States; Montpellier University, France; United Kingdom; United States; France; Belgium; Australia; Japan; Germany; Mexico; Netherlands; China 2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85063648912&doi=10.1111%2fgto.12261&partnerID=40&md5=e60e9c51355824d5270d5baf7899c04c cited By 0 J. Urrutia-Fucugauchi L. Pérez-Cruz J. Morgan S. Gulick A. Wittmann J. Lofi J.V. Morgan S.P.S. Gulick E. Chenot G. Christeson P. Claeys C. Cockell M.J.L. Coolen L. Ferrière C. Gebhardt K. Goto H. Jones D.A. Kring C. Lowery C. Mellett R. Ocampo-Torres A. Pickersgill M. Poelchau A. Rae C. Rasmussen M. Rebolledo-Vieyra U. Riller H. Sato J. Smit S. Tikoo-Schantz N. Tomioka M. Whalen L. Xiao K.E. Yamaguchi T. Bralower G.S. Collins IODP-ICDP Expedition 364 Science Party article Rasmussen2019356 The zircon U-Pb system is one of the most robust geochronometers, but during an impact event individual crystals can be affected differently by the passage of the shock wave and impact generated heat. Unraveling the potentially complex thermal history recorded by zircon crystals that experienced variable levels of shock and heating, as well as additioanl pre- and post-impact thermal events, has been difficult using classical geochronological methods. The existing high-precision 40Ar/39Ar age constraints for the K-Pg Chicxulub event, and the previous U-Pb dating of the basement rocks from the impact site, make Chicxulub an ideal location to study impact-induced effects on the zircon U-Pb systematics and to evaluate potential 'memory effects' of pre-impact U-Pb signatures preserved within those individual zircon crystals. Recent IODP-ICDP drilling of the Chicxulub impact structure recovered 580 m of uplifted shocked granitoid and 130 m of melt and suevite, providing an unprecedented opportunity to study zircon crystals subjected to a range of shock pressures, thermal, and deformational histories. Zircon morphologies were classified using scanning electron microscopy (SEM) imaging and then samples were depth profiled using laser ablation inductively coupled plasma mass-spectrometry (LA-ICP-MS) to document the range of preserved age domains from rim-to-center within individual crystals. The results show U-Pb ages range from 66 to 472 Ma, which are consistent with both inherited Carboniferous and Late Paleozoic basement ages as well as Pb loss ages in response to the K-Pg impact event. While the bulk of the zircon grains preserve Paleozoic ages, high U (metamict) zones within fractured zircon crystals exhibited an age within uncertainty (66 ± 6.2 Ma) of the impact age (66.038 ± 0.049 Ma), indicating that inherited intragrain U-Pb kinetics and/or hydrothermal fluid flow may have controlled age resetting those zircon crystals rather than impact-induced shock and heating alone. Moreover, the calculated α-decay doses suggest that the zircon crystals experienced Stage 1 or early Stage 2 radiation damage accumulation. Therefore, we suggest that the lowered crystal annealing temperature in crystals that previoulsy experienced radiation damage make the zircon U-Pb clock either more susceptible to the relatively short heat pulse of the impact event, the moderate pressure and temperature conditions in the peak ring, and/or to hot-fluid flow in the long-lasting post impact hydrothermal system. © 2019 Elsevier B.V. 2019 10.1016/j.chemgeo.2019.07.029 Chemical Geology 525 356-367 Institute for Geophysics and Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, TX, United States; School of Geographical and Earth Sciences, University of Glasgow, Glasgow, United Kingdom; Argon Isotope Facility, Scottish Universities Environmental Research Centre (SUERC), East Kilbride, United Kingdom; Center for Lunar Science and Exploration, Universities Space Research Association Lunar and Planetary Institute, Houston, TX, United States; Eyring Materials Center, Arizona State University, Tempe, AZ, United States; Department of Earth Science and Engineering, Imperial College LondonSW7 2AZ, United Kingdom https://www.scopus.com/inward/record.uri?eid=2-s2.0-85070198430&doi=10.1016%2fj.chemgeo.2019.07.029&partnerID=40&md5=2441976b9bacd28edadd72562b906e11 cited By 13 C. Rasmussen D.F. Stockli C.H. Ross A. Pickersgill S.P. Gulick M. Schmieder G.L. Christeson A. Wittmann D.A. Kring J.V. Morgan IODP-ICDP Expedition 364 Science Party book Snedden20191 The Gulf of Mexico Basin is one of the most prolific hydrocarbon-producing basins in the world, with an estimated endowment of 200 billion barrels of oil equivalent. This book provides a comprehensive overview of the basin, spanning the US, Mexico and Cuba. Topics covered include conventional and unconventional reservoirs, source rocks and associated tectonics, basin evolution from the Mesozoic to Cenozoic Era, and different regions of the basin from mature onshore fields to deep-water subsalt plays. Cores, well logs and seismic lines are all discussed providing local, regional and basin-scale insights. The scientific implications of seminal events in the basin’s history are also covered, including sedimentary effects of the Chicxulub Impact. Containing over 200 color illustrations and 50 stratigraphic cross-sections and paleogeographic maps, this is an invaluable resource for petroleum industry professionals, as well as graduate students and researchers interested in basin analysis, sedimentology, stratigraphy, tectonics and petroleum geology. © John W. Snedden and William E. Galloway 2019. 2019 10.1017/9781108292795 The Gulf of Mexico Sedimentary Basin: Depositional Evolution and Petroleum Applications 1-326 Institute for Geophysics, University of Texas at Austin, United States; Department of Geological Sciences, Institute for Geophysics, University of Texas at Austin, United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-85092173394&doi=10.1017%2f9781108292795&partnerID=40&md5=fd9886c8a177e2594b03e346830f9739 cited By 47 J.W. Snedden W.E. Galloway article Gulick201919342 Highly expanded Cretaceous-Paleogene (K-Pg) boundary section from the Chicxulub peak ring, recovered by International Ocean Discovery Program (IODP)-International Continental Scientific Drilling Program (ICDP) Expedition 364, provides an unprecedented window into the immediate aftermath of the impact. Site M0077 includes ∼130 m of impact melt rock and suevite deposited the first day of the Cenozoic covered by <1 m of micrite-rich carbonate deposited over subsequent weeks to years. We present an interpreted series of events based on analyses of these drill cores. Within minutes of the impact, centrally uplifted basement rock collapsed outward to forma peak ring capped in melt rock. Within tens of minutes, the peak ring was covered in ∼40 m of brecciated impact melt rock and coarsegrained suevite, including clasts possibly generated by melt-water interactions during ocean resurge. Within an hour, resurge crested the peak ring, depositing a 10-m-thick layer of suevite with increased particle roundness and sorting.Within hours, the full resurge deposit formed through settling and seiches, resulting in an 80-m-thick fining-upward, sorted suevite in the flooded crater. Within a day, the reflected rim-wave tsunami reached the crater, depositing a cross-bedded sand-to-fine gravel layer enriched in polycyclic aromatic hydrocarbons overlain by charcoal fragments. Generation of a deep crater open to the ocean allowed rapid flooding and sediment accumulation rates among the highest known in the geologic record. The high-resolution section provides insight into the impact environmental effects, including charcoal as evidence for impactinduced wildfires and a paucity of sulfur-rich evaporites from the target supporting rapid global cooling and darkness as extinction mechanisms. © 2019 National Academy of Sciences. All rights reserved. 2019 10.1073/pnas.1909479116 Proceedings of the National Academy of Sciences of the United States of America 116 19342-19351 Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78758, United States; Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 79712, United States; Department of Geosciences, Pennsylvania State University, University Park, PA 16801, United States; Centro de Astrobiologia Instituto Nacional de Tecnica Aeroespacial-Spanish National Research Council, Instituto Nacional de Técnica Aeroespacial, Torrejon de Ardoz, 28850, Spain; Enthought, Inc., Austin, TX 78701, United States; Western Australian Organic and Isotope Geochemistry Centre, Institute for Geoscience Research, School of Earth and Planetary Science, Curtin University, Perth, WA 6102, Australia; Department of Earth Science and Engineering, Imperial College London, London, SW7 2AZ, United Kingdom; Planetary Science Institute, Tucson, AZ 85719-2395, United States; Analytical, Environmental and Geo-Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, Brussels, B-1050, Belgium; Department of Geosciences, University of Alaska Fairbanks, Fairbanks, AK 99775, United States; Department of Earth and Planetary Sciences, Rutgers University, New Brunswick, NJ 08854, United States; International Research Institute of Disaster Science, Tohoku University, Sendai, 980-8572, Japan; Department of Earth Sciences, University of Western Ontario, London, ON N6A 3K7, Canada; Institut für Geologie, Universität Hamburg, Hamburg, 20146, Germany; Faculty of Earth and Life Sciences (FALW), Vrije Universiteit Amsterdam, Amsterdam, 1081 HV, Netherlands; Swedish Museum of Natural History, Stockholm, 114 18, Sweden; Eyring Materials Center, Arizona State University, Tempe, AZ 85287-1704, United States 39 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85072638126&doi=10.1073%2fpnas.1909479116&partnerID=40&md5=9e9ef9ec1b056adbd8f5d307962f49bb cited By 79 S.P.S. Gulick T.J. Bralower J. Ormö K. Grice B. Schaefer S. Lyons K.H. Freeman J.V. Morgan N. Artemieva P. Kaskes S.J. De Graaff M.T. Whalen G.S. Collins S.M. Tikoo C. Verhagen G.L. Christeson P. Claeys M.J.L. Coolen S. Goderis K. Goto R.A.F. Grieve N. McCall G.R. Osinski A.S.P. Rae U. Riller J. Smit V. Vajda A. Wittmann article Rae2019396 Deformation is a ubiquitous process that occurs to rocks during impact cratering; thus, quantifying the deformation of those rocks can provide first-order constraints on the process of impact cratering. Until now, specific quantification of the conditions of stress and strain within models of impact cratering has not been compared to structural observations. This paper describes a methodology to analyze stress and strain within numerical impact models. This method is then used to predict deformation and its cause during peak-ring formation: a complex process that is not fully understood, requiring remarkable transient weakening and causing a significant redistribution of crustal rocks. The presented results are timely due to the recent Joint International Ocean Discovery Program and International Continental Scientific Drilling Program drilling of the peak ring within the Chicxulub crater, permitting direct comparison between the deformation history within numerical models and the structural history of rocks from a peak ring. The modeled results are remarkably consistent with observed deformation within the Chicxulub peak ring, constraining the following: (1) the orientation of rocks relative to their preimpact orientation; (2) total strain, strain rates, and the type of shear during each stage of cratering; and (3) the orientation and magnitude of principal stresses during each stage of cratering. The methodology and analysis used to generate these predictions is general and, therefore, allows numerical impact models to be constrained by structural observations of impact craters and for those models to produce quantitative predictions. ©2019. American Geophysical Union. All Rights Reserved. 2019 10.1029/2018JE005821 Journal of Geophysical Research: Planets 124 396-417 Department of Earth Science and Engineering, Imperial College London, London, United Kingdom; Institut für Geo- und Umweltnaturwissenschaften, Albert-Ludwigs-Universität Freiburg, Geologie, Freiburg, Germany; Institut für Geologie, Universität Hamburg, Hamburg, Germany; Department of Earth Sciences/Centre for Planetary Science and Exploration, Western University, London, ON, Canada 2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85061564680&doi=10.1029%2f2018JE005821&partnerID=40&md5=66c0622c1c42f72ecffa147d91189719 cited By 25 A.S.P. Rae G.S. Collins M. Poelchau U. Riller T.M. Davison R.A.F. Grieve G.R. Osinski J.V. Morgan E. Iodp-Icdp article Tillberg2019 Impact-generated hydrothermal systems have been suggested as favourable environments for deep microbial ecosystems on Earth, and possibly beyond. Fossil evidence from a handful of impact craters worldwide have been used to support this notion. However, as always with mineralized remains of microorganisms in crystalline rock, certain time constraints with respect to the ecosystems and their subsequent fossilization are difficult to obtain. Here we re-evaluate previously described fungal fossils from the Lockne crater (458 Ma), Sweden. Based on in-situ Rb/Sr dating of secondary calcite-albite-feldspar (356.6 ± 6.7 Ma) we conclude that the fungal colonization took place at least 100 Myr after the impact event, thus long after the impact-induced hydrothermal activity ceased. We also present microscale stable isotope data of13C-enriched calcite suggesting the presence of methanogens contemporary with the fungi. Thus, the Lockne fungi fossils are not, as previously thought, related to the impact event, but nevertheless have colonized fractures that may have been formed or were reactivated by the impact. Instead, the Lockne fossils show similar features as recent findings of ancient microbial remains elsewhere in the fractured Swedish Precambrian basement and may thus represent a more general feature in this scarcely explored habitat than previously known. © 2019 by the authors. Licensee MDPI, Basel, Switzerland. 2019 10.3390/geosciences9050202 Geosciences (Switzerland) 9 Department of Biology and Environmental Science, Linnaeus University, Kalmar, 392 31, Sweden; Department of Earth Sciences, University of Gothenburg, Box 460, Göteborg, 40530, Sweden; Department of Biology, University of Southern Denmark, Campusvej 55, Odense, 5230, Denmark; Department of Paleobiology, Swedish Museum of Natural History, Box 50 007, Stockholm, 104 05, Sweden; Department of Geosciences, Swedish Museum of Natural History, Box 50 007, Stockholm, 104 05, Sweden 5 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85067627284&doi=10.3390%2fgeosciences9050202&partnerID=40&md5=057fef97b6a1e9d6544c97d47265fbac cited By 6 M. Tillberg M. Ivarsson H. Drake M.J. Whitehouse E. Kooijman M. Schmitt article Rae20191960 Porosity and its distribution in impact craters has an important effect on the petrophysical properties of impactites: seismic wave speeds and reflectivity, rock permeability, strength, and density. These properties are important for the identification of potential craters and the understanding of the process and consequences of cratering. The Chicxulub impact structure, recently drilled by the joint International Ocean Discovery Program and International Continental scientific Drilling Program Expedition 364, provides a unique opportunity to compare direct observations of impactites with geophysical observations and models. Here, we combine small-scale petrographic and petrophysical measurements with larger-scale geophysical measurements and numerical simulations of the Chicxulub impact structure. Our aim is to assess the cause of unusually high porosities within the Chicxulub peak ring and the capability of numerical impact simulations to predict the gravity signature and the distribution and texture of porosity within craters. We show that high porosities within the Chicxulub peak ring are primarily caused by shock-induced microfracturing. These fractures have preferred orientations, which can be predicted by considering the orientations of principal stresses during shock, and subsequent deformation during peak ring formation. Our results demonstrate that numerical impact simulations, implementing the Dynamic Collapse Model of peak ring formation, can accurately predict the distribution and orientation of impact-induced microfractures in large craters, which plays an important role in the geophysical signature of impact structures. ©2019. American Geophysical Union. All Rights Reserved. 2019 10.1029/2019JE005929 Journal of Geophysical Research: Planets 124 1960-1978 Department of Earth Science and Engineering, Imperial College London, London, United Kingdom; Institut für Geo- und Umweltnaturwissenschaften, Albert-Ludwigs-Universität Freiburg, Geologie, Freiburg, Germany; Imaging and Analysis Centre, Natural History Museum, London, United Kingdom; Institute for Geophysics and Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, TX, United States; Gèosciences Montpellier, Universitè de Montpellier, Montpellier, France; Institut für Geologie, Universität Hamburg, Hamburg, Germany; Alfred Wegener Institute, Helmholtz Centre of Polar and Marine Research, Bremerhaven, Germany; Department of Earth Sciences/Centre for Planetary Science and Exploration, Western University, London, ON, Canada 7 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85070207698&doi=10.1029%2f2019JE005929&partnerID=40&md5=6440580a2a4ab3c7d2bca7e6d22e8598 cited By 17 A.S.P. Rae G.S. Collins J.V. Morgan T. Salge G.L. Christeson J. Leung J. Lofi S.P.S. Gulick M. Poelchau U. Riller C. Gebhardt R.A.F. Grieve G.R. Osinski article Lowery2019120 Extraterrestrial impacts that reshape the surfaces of rocky bodies are ubiquitous in the solar system. On early Earth, impact structures may have nurtured the evolution of life. More recently, a large meteorite impact off the Yucatán Peninsula in Mexico at the end of the Cretaceous caused the disappearance of 75% of species known from the fossil record, including non-avian dinosaurs, and cleared the way for the dominance of mammals and the eventual evolution of humans. Understanding the fundamental processes associated with impact events is critical to understanding the history of life on Earth, and the potential for life in our solar system and beyond. Scientific ocean drilling has generated a large amount of unique data on impact processes. In particular, the Yucatán Chicxulub impact is the single largest and most significant impact event that can be studied by sampling in modern ocean basins, and marine sediment cores have been instrumental in quantifying its environmental, climatological, and biological effects. Drilling in the Chicxulub crater has significantly advanced our understanding of fundamental impact processes, notably the formation of peak rings in large impact craters, but these data have also raised new questions to be addressed with future drilling. Within the Chicxulub crater, the nature and thickness of the melt sheet in the central basin is unknown, and an expanded Paleocene hemipelagic section would provide insights to both the recovery of life and the climatic changes that followed the impact. Globally, new cores collected from today’s central Pacific could directly sample the downrange ejecta of this northeast-southwest trending impact. Extraterrestrial impacts have been controversially suggested as primary drivers for many important paleoclimatic and environmental events throughout Earth history. However, marine sediment archives collected via scientific ocean drilling and geochemical proxies (e.g., osmium isotopes) provide a long-term archive of major impact events in recent Earth history and show that, other than the end-Cretaceous, impacts do not appear to drive significant environmental changes. © 2019 The Oceanography Society, Inc. 2019 10.5670/oceanog.2019.133 Oceanography 32 120-134 University of Texas Institute for Geophysics, Jackson School of Geosciences, Austin, TX, United States; Department of Earth Science and Engineering, Imperial College, London, United Kingdom; Department of Geosciences, Pennsylvania State University, University Park, PA, United States; University of Texas Institute for Geophysics, Jackson School of Geosciences, Austin, TX, United States 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85065918866&doi=10.5670%2foceanog.2019.133&partnerID=40&md5=f6cdf244574bb6d3971efec054ec6f2c cited By 4 C.M. Lowery J.V. Morgan S.P.S. Gulick T.J. Bralower G.L. Christeson E. Chenot P. Claeys C. Cockell M.J.L. Coolen L. Ferrière C. Gebhardt K. Goto S. Green H. Jones D.A. Kring J. Lofi C. Mellett R. Ocampo-Torres L. Pérez-Cruz A. Pickersgill M. Poelchau A. Rae C. Rasmussen M. Rebolledo-Vieyra U. Riller H. Sato J. Smit S. Tikoo N. Tomioka J. Urrutia-Fucugauchi M. Whalen A. Wittmann L. Xiao K. Yamaguchi Expedition 364 Scientists article Siegert20192409 Impact melt-bearing clastic deposits (suevites) are one of the most important records of the impact cratering process. A deeper understanding of their composition and formation is therefore essential. This study focuses on impact melt particles in suevite at Ries, Germany. Textures and chemical evidence indicate that the suevite contains three melt types that originate from different shock levels in the target. The most abundant melt type (“melt type 1”) represents well-mixed whole-rock melting of crystalline basement and includes incompletely mixed mafic melt schlieren (“melt type 1 mafic”). Polymineralic melt type 2 comprises mixes between monomineralic melt types 3 and melt type 1. Melt types 2 and 3 are located within melt type 1 as small patches or schlieren but also isolated within the suevite matrix. The main melt type 1 is heterogeneous with respect to trace elements, varying geographically around the crater: in the western sector, it has lower values in trace elements, e.g., Ba, Zr, Th, and Ce, than in the eastern sector. The west–east zoning likely reflects the heterogeneous nature of crystalline basement target rocks with lower trace element contents, e.g., Ba, Zr, Th, and Ce, in the west compared to the east. The chemical zoning pattern of suevite melt type 1 indicates that mixing during ejection and emplacement occurred only on a local (hundreds of meters) scale. The incomplete larger scale mixing indicated by the preservation of these local chemical signatures, and schlieren corroborate the assumption that mixing, ejection, and quenching were very rapid, short-lived processes. © The Meteoritical Society, 2018. 2019 10.1111/maps.13210 Meteoritics and Planetary Science 54 2409-2447 Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstraße 43, Berlin, 10115, Germany; Freie Universität Berlin, Institut für Geologische Wissenschaften, Malteserstraße 74-100, Berlin, 12249, Germany 10 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85057114107&doi=10.1111%2fmaps.13210&partnerID=40&md5=d8aed236041dd6a9b3dc39b7c67365db cited By 4 S. Siegert L. Hecht article Salge20192334 Drill core UNAM-7, obtained 126 km from the center of the Chicxulub impact structure, outside the crater rim, contains a sequence of 126.2 m suevitic, silicate melt-rich breccia on top of a silicate melt-poor breccia with anhydrite megablocks. Total reflection X-ray fluorescence analysis of altered silicate melt particles of the suevitic breccia shows high concentrations of Br, Sr, Cl, and Cu, which may indicate hydrothermal reaction with sea water. Scanning electron microscopy and energy-dispersive spectrometry reveal recrystallization of silicate components during annealing by superheated impact melt. At anhydrite clasts, recrystallization is represented by a sequence of comparatively large columnar, euhedral to subhedral anhydrite grains and smaller, polygonal to interlobate grains that progressively annealed deformation features. The presence of voids in anhydrite grains indicates SOx gas release during anhydrite decomposition. The silicate melt-poor breccia contains carbonate and sulfate particles cemented in a microcrystalline matrix. The matrix is dominated by anhydrite, dolomite, and calcite, with minor celestine and feldspars. Calcite-dominated inclusions in silicate melt with flow textures between recrystallized anhydrite and silicate melt suggest a former liquid state of these components. Vesicular and spherulitic calcite particles may indicate quenching of carbonate melts in the atmosphere at high cooling rates, and partial decomposition during decompression at postshock conditions. Dolomite particles with a recrystallization sequence of interlobate, polygonal, subhedral to euhedral microstructures may have been formed at a low cooling rate. We conclude that UNAM-7 provides evidence for solid-state recrystallization or melting and dissociation of sulfates during the Chicxulub impact event. The lack of anhydrite in the K-Pg ejecta deposits and rare presence of anhydrite in crater suevites may indicate that sulfates were completely dissociated at high temperature (T &gt; 1465 °C)—whereas ejecta deposited near the outer crater rim experienced postshock conditions that were less effective at dissociation. © The Trustees of the Natural History Museum, London, 2019. 2019 10.1111/maps.13283 Meteoritics and Planetary Science 54 2334-2356 Natural History Museum, Imaging and Analysis Centre, Cromwell Road, London, SW7 5BD, United Kingdom; Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstrasse 43, Berlin, 10115, Germany; Bruker Nano GmbH, Am Studio, Berlin, 12489, Germany; Dipertimento Disputer, Università G. d'Annunzio, Chieti, 66100, Italy; Institut für Geologische Wissenschaften, Freie Universität Berlin, Malteserstraße 74-100, Berlin, 12249, Germany; Laboratory of Geochronology, Instituto de Geociências, Universidade de Brasília, Brasília, DF 70910 900, Brazil 10 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85063860385&doi=10.1111%2fmaps.13283&partnerID=40&md5=457457f70366179870d7ce3fadba827b cited By 3 T. Salge H. Stosnach G. Rosatelli L. Hecht W.U. Reimold article Jankowski2019106 The irregular distribution of sand injections, traditionally termed “dykes" in the Polish geological literature, within individual Carpathian units and within individual lithofacies were observed during long-lasting field works. Injectites have been observed in the Magura Beds and in the Inoceramian Beds of the Polish and Romanian Carpathians, and in the Central Carpathian Paleogene deposits. However, they are most common in the Oligocene-Miocene Menilite Beds, where they are typical and abundant, particularly in the Skole Unit. Two clastic injectite types were distinguished: sedimentary (S-type) and tectonized (T-type). Based on the occurrence and interpretation of these injectites a new two-stage conceptual model is proposed for the Polish segment of the progressive Oligocene-Miocene Carpathian orogenic belt evolution. Type S clastic injectites are interpreted as having formed in the compressional stage, during foredeep basin migration while depositional slope changes were taking place in the Late Oligocene to Early Miocene. Type T injectites are interpreted as having formed by reactivation of S-type injectites in the last, mainly strike-slip, phases of Carpathian orogenic belt formation. © 2019, Polish Geological Institute. All rights reserved. 2019 10.7306/gq.1460 Geological Quarterly 63 106-125 Polish Geological Institute – National Research Institute, Rakowiecka 4, Warszawa, 00-975, Poland; University of Warsaw, Faculty of Geology, Żwirki i Wigury 93, Warszawa, 02-089, Poland 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85067936758&doi=10.7306%2fgq.1460&partnerID=40&md5=b1842bfd87f1b8794231a912bc7bf029 cited By 8 L. Jankowski A. Wysocka article Coldwell2019209 Potassium feldspar present in global mineral aerosol (<5%) plays a disproportionate role in modulating the microphysics of mixed-phase cloud. Via exceptional ice nucleation properties, it is capable of changing cloud properties and behaviour. Here we identify times of substantial and abrupt change in the global availability of potassium feldspar since 600 Ma. Normally, weathering and vegetation cover contribute to low availability, with clay dominating mineral aerosol. Periods of maximum availability are reasoned to follow the emplacement and remobilization of ejecta blankets from major meteorite impact events, before returning to background after some hundreds to thousands of years. We review the 44 largest confirmed craters and evaluate the potassium feldspar content of their target rocks, which range from c. 0 to >30%. By combining crater size and tectonic reconstructions, we are able to provide a quantitative and self-consistent assessment of changes to global potassium feldspar availability. Considerable differences in potassium feldspar availability following meteorite impact events are revealed. Different impact events generated dust containing different amounts of potassium feldspar. Differing levels of influence upon climate are hypothesized, and should now be tested by looking at stratigraphic records of these events to reveal the sensitivity of climate to different dust mineralogy. © 2018 The Author(s). 2019 10.1144/jgs2018-084 Journal of the Geological Society 176 209-224 Instituto Tecnológico y de Energías Renovables (ITER), Granadilla de Abona, Santa Cruz de Tenerife 38600, Spain; Instituto Volcanológico de Canarias (INVOLCAN), Calle Álvaro Martín Díaz 1, San Cristóbal de La Laguna, Santa Cruz de Tenerife 38320, Spain; School of Materials, University of Manchester, Manchester, M13 9PJ, United Kingdom; Research Complex at Harwell, Harwell Campus, Didcot, OX11 0FA, United Kingdom; School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, United Kingdom 2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85063353451&doi=10.1144%2fjgs2018-084&partnerID=40&md5=72ba72c040095c8bca3dec26864cb7e2 cited By 1 B.C. Coldwell M.J. Pankhurst article Timms2019 Accessory mineral geochronometers such as apatite, baddeleyite, monazite, xenotime and zircon are increasingly being recognized for their ability to preserve diagnostic microstructural evidence of hypervelocity-impact processes. To date, little is known about the response of titanite to shock metamorphism, even though it is a widespread accessory phase and a U–Pb geochronometer. Here we report two new mechanical twin modes in titanite within shocked granitoid from the Chicxulub impact structure, Mexico. Titanite grains in the newly acquired core from the International Ocean Discovery Program Hole M0077A preserve multiple sets of polysynthetic twins, most commonly with composition planes (K1) = ~ { 1 ¯ 11 } , and shear direction (η1) = &lt; 110 &gt; , and less commonly with the mode K1 = {130}, η1 = ~ &lt;522 &gt;. In some grains, {130} deformation bands have formed concurrently with the deformation twins, indicating dislocation slip with Burgers vector b = &lt; 341 &gt; can be active during impact metamorphism. Titanite twins in the modes described here have not been reported from endogenically deformed rocks; we, therefore, propose this newly identified twin form as a result of shock deformation. Formation conditions of the twins have not been experimentally calibrated, and are here empirically constrained by the presence of planar deformation features in quartz (12 ± 5 and ~ 17 ± 5 GPa) and the absence of shock twins in zircon (&lt; 20 GPa). While the lower threshold of titanite twin formation remains poorly constrained, identification of these twins highlight the utility of titanite as a shock indicator over the pressure range between 12 and 17 GPa. Given the challenges to find diagnostic indicators of shock metamorphism to identify both ancient and recent impact evidence on Earth, microstructural analysis of titanite is here demonstrated to provide a new tool for recognizing impact deformation in rocks where other impact evidence may be erased, altered, or did not manifest due to generally low (&lt; 20 GPa) shock pressure. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature. 2019 10.1007/s00410-019-1565-7 Contributions to Mineralogy and Petrology 174 The Institute for Geoscience Research (TIGeR), Space Science and Technology Centre, School of Earth and Planetary Sciences, Curtin University, GPO Box U1987, Perth, WA 6845, Australia; CSIRO Mineral Resources, Australian Resources Research Centre, 26 Dick Perry Avenue, Kensington, WA 6151, Australia; Jacobs-JETS, NASA Johnson Space Center, Astromaterials Research and Exploration Science Division, Mailcode XI3, 2101 NASA Parkway, Houston, TX 77058, United States; Department of Earth Science and Engineering, Imperial College London, London, United Kingdom; Institut für Geo- und Umweltnaturwissenschaften, Albert-Ludwigs-Universität, Freiburg, Albertstraße 23b, Freiburg, 79104, Germany; Department of Earth and Ocean Sciences, University of Liverpool, Liverpool, L69 3GP, United Kingdom; Eyring Materials Center, Arizona State University, Tempe, AZ, United States; Natural History Museum, Burgring 7, Vienna, 1010, Austria; Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, Kochi, Japan; Institute for Geophysics and Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, TX, United States 5 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85065307578&doi=10.1007%2fs00410-019-1565-7&partnerID=40&md5=509f1d3079d4816026936f190bd7f097 cited By 18 N.E. Timms M.A. Pearce T.M. Erickson A.J. Cavosie A.S.P. Rae J. Wheeler A. Wittmann L. Ferrière M.H. Poelchau N. Tomioka G.S. Collins S.P.S. Gulick C. Rasmussen J.V. Morgan E. Chenot G.L. Christeson P. Claeys C.S. Cockell M.J.L. Coolen C. Gebhardt K. Goto S. Green H. Jones D.A. Kring J. Lofi C.M. Lowery R. Ocampo-Torres L. Pérez-Cruz A.E. Pickersgill M. Rebolledo-Vieyra U. Riller H. Sato J. Smit S.M. Tikoo J. Urrutia-Fucugauchi M.T. Whalen L. Xiao K.E. Yamaguchi IODP-ICDP Expedition 364 Scientists article Kontny2018921 We studied the effect of 973 K heating in argon atmosphere on the magnetic and structural properties of a magnetite-bearing ore, which was previously exposed to laboratory shock waves between 5 and 30 GPa. For this purpose magnetic properties were studied using temperature-dependent magnetic susceptibility, magnetic hysteresis and low-temperature saturation isothermal remanent magnetization. Structural properties of magnetite were analyzed using X-ray diffraction, high-resolution scanning electron microscopy and synchrotron-assisted X-ray absorption spectroscopy. The shock-induced changes include magnetic domain size reduction due to brittle and ductile deformation features and an increase in Verwey transition temperature due to lattice distortion. After heating, the crystal lattice is relaxed and apparent crystallite size is increased suggesting a recovery of lattice defects documented by a mosaic recrystallization texture. The structural changes correlate with modifications in magnetic domain state recorded by temperature-dependent magnetic susceptibility, hysteresis properties and low-temperature saturation isothermal remanent magnetization. These alterations in both, magnetic and structural properties of magnetite can be used to assess impact-related magnetic anomalies in impact structures with a high temperature overprint. © 2018. American Geophysical Union. All Rights Reserved. 2018 10.1002/2017GC007331 Geochemistry, Geophysics, Geosystems 19 921-931 Institute of Applied Geosciences, Karlsruhe Institute of Technology, Karlsruhe, Germany; SLAC National Accelerator Laboratory, Stanford Synchrotron Radiation Lightsource (SSRL), Menlo Park, CA, United States; Synchrotron Radiation Facility ANKA, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany 3 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85044219734&doi=10.1002%2f2017GC007331&partnerID=40&md5=8de02fa1cf1a17cf1390cc580d43ec72 cited By 9 A. Kontny B. Reznik A. Boubnov J. Göttlicher R. Steininger article Glikson201861 As distinct from small to medium-size impact events, large asteroid impacts producing explosions more powerful than 107 TNT-equivalent, represented by craters and rebound domes larger than about 100 km in diameter have major consequences including the triggering of major seismic events, tsunami events and extinction episodes. Such events are manifested by the Archaean ~3.25–3.24 Ga impact cluster and associated transformation from greenstone-granite terrains to semi-continental assemblages (Glikson AY, Vickers J, Earth Planet Sci Lett 241:11–20, 2006). These impact events are considered in Chap. 6. The oldest identified mega-impact is the ~3 Ga Maniitsoq structure in southwest Greenland, while younger mega-impact structures &gt;100 km in diameter include the Vredefort and Sudbury structures. Phanerozoic mega-impacts include the Woodleigh impact structure, Warburton twin structures, Chicxulub and Popigai structures. The global tectonic consequences of some of these mega-impacts are yet to be elucidated. © 2018, Springer International Publishing AG. 2018 10.1007/978-3-319-74545-9_3 Modern Approaches in Solid Earth Sciences 14 61-78 Planetary Science Institute, Australian National University, Canberra, ACT, Australia; Centre for Exploration Targeting, The University of Western Australia, Crawley, WA, Australia https://www.scopus.com/inward/record.uri?eid=2-s2.0-85044166424&doi=10.1007%2f978-3-319-74545-9_3&partnerID=40&md5=f19b4ec783e27cadedd0c1d676eaab12 cited By 0 A.Y. Glikson F. Pirajno article Canales-García2018215 Chicxulub Crater, formed ~66Ma ago by an asteroid impact on the southern Gulf of Mexico, is the best preserved of the three large multi-ring basins in the terrestrial record. The crater structure is characterized by a semi-circular concentric ring pattern, marking the crater basin, peak ring, terrace zone and basement uplift. Analysis of a grid of 19 seismic reflection profiles using seismic attributes, marker horizons, contour surfaces and 3-D views is used to investigate the stratigraphy of the central zone. We used interactive software and routine applications to map the impact breccias, breccia-carbonate contact and post-impact carbonates. Four horizons marked by high-amplitude reflectors representing high-impedance contrasts were identified and laterally correlated in the seismic images. Complex trace attribute analysis was applied for petrophysical characterization. Surface contour maps of base and top of stratigraphic packages were constructed, which mapped the impactites and post-and pre-impact carbonate stratigraphy. Basin floor, marked by the contact between the impact breccias and overlying carbonates is shown by laterally discontinuous high-amplitude reflectors. Discontinuous scattered reflectors interpreted as the upper breccias beneath the crater floor, have an average thickness of ~300msm. The Paleogene sedimentary units are characterized by multiple reflectors with lateral continuity, which contrast with the seismic response of underlying breccias. The basal Paleocene sediments follow the basin floor relief. Upwards in the section, the carbonate strata are characterized by horizontal reflectors, which are interrupted by a regional unconformity. Onlap/downlap packages over the unconformity record a period of sea level change. ©I. Canales-García, J. Urrutia-Fucugauchi, E. Aguayo-Camargo, 2018 CC BY-SA. 2018 10.1344/GeologicaActa2018.16.2.6 Geologica Acta 16 215-235 Universidad Nacional Autónoma de México, Ciudad Universitaria, Delegación Coyoacán, México, 04510, Mexico; Instituto de Geofísica, Universidad Nacional Autónoma de México, Departamento de Geomagnetismo y Exploración, Ciudad Universitaria, Delegación Coyoacán, México, 04510, Mexico; Facultad de Ingeniería, Universidad Nacional Autónoma de México, Departamento de Geología, Ciudad Universitaria, Delegación Coyoacán, México, 04510, Mexico 2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85051627567&doi=10.1344%2fGeologicaActa2018.16.2.6&partnerID=40&md5=abb4ebcc5d820b9b65393f9191b1ae52 cited By 4 I. Canales-García J. Urrutia-Fucugauchi E. Aguayo-Camargo article Riller2018511 Large meteorite impact structures on the terrestrial bodies of the Solar System contain pronounced topographic rings, which emerged from uplifted target (crustal) rocks within minutes of impact. To flow rapidly over large distances, these target rocks must have weakened drastically, but they subsequently regained sufficient strength to build and sustain topographic rings. The mechanisms of rock deformation that accomplish such extreme change in mechanical behaviour during cratering are largely unknown and have been debated for decades. Recent drilling of the approximately 200-km-diameter Chicxulub impact structure in Mexico has produced a record of brittle and viscous deformation within its peak-ring rocks. Here we show how catastrophic rock weakening upon impact is followed by an increase in rock strength that culminated in the formation of the peak ring during cratering. The observations point to quasi-continuous rock flow and hence acoustic fluidization as the dominant physical process controlling initial cratering, followed by increasingly localized faulting. © 2018, Springer Nature Limited. 2018 10.1038/s41586-018-0607-z Nature 562 511-518 Institut für Geologie, Universität Hamburg, Hamburg, Germany; Department of Geology, Universität Freiburg, Freiburg, Germany; Department of Earth Science and Engineering, Imperial College London, London, United Kingdom; Department of Earth, Atmospheric and Planetary Sciences, Purdue University, West Lafayette, IN, United States; Centre for Planetary Science and Exploration, Western University, London, ON, Canada; Institute for Geophysics, University of Texas, Austin, TX, United States; Department of Geological Sciences, Jackson School of Geosciences, University of Texas, Austin, TX, United States; Géosciences Montpellier, CNRS, Université de Montpellier, Montpellier, France; Universities Space Research Association, Lunar and Planetary Institute, Houston, TX, United States; British Geological Survey, The Lyell Centre, Research Avenue South, Edinburgh, United Kingdom; Université de Bourgogne-CNRS, Biogeosciences Laboratory, Dijon, France; Analytical, Environmental and Geochemistry (AMGC), Vrije Universiteit Brussel (VUB), Brussels, Belgium; School of Physics and Astronomy, UK Center for Astrobiology, University of Edinburgh, Edinburgh, United Kingdom; Western Australia Organic and Isotope Geochemistry Centre, School of Earth and Planetary Sciences, Curtin University, Bentley, WA, Australia; Natural History Museum, Vienna, Austria; Alfred Wegener Institute Helmholtz Centre of Polar and Marine Research, Bremerhaven, Germany; International Research Institute of Disaster Science, Tohoku University, Sendai, Japan; Pennsylvania State University, University Park, PA, United States; China University of Geosciences (Wuhan), School of Earth Sciences, Planetary Science Institute, Wuhan, China; National Center of Scientific Research (CNRS), Groupe de Physico-Chimie de l’Atmosphère, Institut de Chimie et Procédés pour l’Energie, l’Environnement et la Santé ICPEES, Université de Strasbourg, Strasbourg, France; Instituto de Geofísica, Universidad Nacional Autónoma De México, México City, Mexico; School of Geographical and Earth Sciences, University of Glasgow, Glasgow, United Kingdom; Argon Isotope Facility, Scottish Universities Environmental Research Centre (SUERC), East Kilbride, United Kingdom; Department of Geology, University of Freiburg, Freiburg, Germany; Department of Earth Science and Engineering, Imperial College London, London, United Kingdom; Unidad de Ciencias del Agua, Mérida, Mexico; Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan; Faculty of Earth and Life Sciences, Amsterdam, Netherlands; Earth and Planetary Sciences, Rutgers University—New Brunswick, Piscataway, NJ, United States; Japan Agency for Marine-Earth Science and Technology, Kochi Institute for Core Sample Research, Kochi, Japan; Department of Geosciences, University of Alaska Fairbanks, Fairbanks, AK, United States; Eyring Materials Center, Arizona State University, Tempe, AZ, United States; Department of Chemistry, Tohu University, Funabashi, Japan; NASA Astrobiology Institute, Mountain View, CA, United States 7728 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85055416559&doi=10.1038%2fs41586-018-0607-z&partnerID=40&md5=53993392074e42eeda2f50f11a27862e cited By 52 U. Riller M.H. Poelchau A.S.P. Rae F.M. Schulte G.S. Collins H.J. Melosh R.A.F. Grieve J.V. Morgan S.P.S. Gulick J. Lofi A. Diaw N. McCall D.A. Kring S.L. Green E. Chenot G.L. Christeson P. Claeys C.S. Cockell M.J.L. Coolen L. Ferrière C. Gebhardt K. Goto H. Jones L. Xiao C.M. Lowery R. Ocampo-Torres L. Pérez-Cruz A.E. Pickersgill C. Rasmussen M. Rebolledo-Vieyra H. Sato J. Smit S.M. Tikoo-Schantz N. Tomioka M.T. Whalen A. Wittmann K. Yamaguchi T.J. Bralower J.U. Fucugauchi IODP-ICDP Expedition 364 Science Party article Lowery2018288 The Cretaceous/Palaeogene mass extinction eradicated 76% of species on Earth 1,2. It was caused by the impact of an asteroid 3,4 on the Yucatán carbonate platform in the southern Gulf of Mexico 66 million years ago 5, forming the Chicxulub impact crater 6,7. After the mass extinction, the recovery of the global marine ecosystem - measured as primary productivity - was geographically heterogeneous 8 ; export production in the Gulf of Mexico and North Atlantic-western Tethys was slower than in most other regions 8-11, taking 300 thousand years (kyr) to return to levels similar to those of the Late Cretaceous period. Delayed recovery of marine productivity closer to the crater implies an impact-related environmental control, such as toxic metal poisoning 12, on recovery times. If no such geographic pattern exists, the best explanation for the observed heterogeneity is a combination of ecological factors - trophic interactions 13, species incumbency and competitive exclusion by opportunists 14 - and 'chance' 8,15,16. The question of whether the post-impact recovery of marine productivity was delayed closer to the crater has a bearing on the predictability of future patterns of recovery in anthropogenically perturbed ecosystems. If there is a relationship between the distance from the impact and the recovery of marine productivity, we would expect recovery rates to be slowest in the crater itself. Here we present a record of foraminifera, calcareous nannoplankton, trace fossils and elemental abundance data from within the Chicxulub crater, dated to approximately the first 200 kyr of the Palaeocene. We show that life reappeared in the basin just years after the impact and a high-productivity ecosystem was established within 30 kyr, which indicates that proximity to the impact did not delay recovery and that there was therefore no impact-related environmental control on recovery. Ecological processes probably controlled the recovery of productivity after the Cretaceous/Palaeogene mass extinction and are therefore likely to be important for the response of the ocean ecosystem to other rapid extinction events. © 2018 Macmillan Publishers Ltd., part of Springer Nature. 2018 10.1038/s41586-018-0163-6 Nature 558 288-291 Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, TX, United States; Department of Geosciences, Pennsylvania State University, University Park, PA, United States; Department of Earth, Ocean and Atmospheric Science, National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, United States; Departamento de Estratigrafía y Paleontología, Universidad de Granada, Granada, Spain; Faculty of Earth and Life Sciences (FALW), Vrije Universiteit Amsterdam, Amsterdam, Netherlands; Department of Geosciences, University of Alaska Fairbanks, Fairbanks, AK, United States; Analytical, Environmental and Geo-Chemistry, Vrije Universiteit Brussel, Brussels, Belgium; Division of Geological and Planetary Sciences, California Institute of Technology, MS 170-25, Pasadena, CA, United States; Department of Earth Science and Engineering, Imperial College London, London, United Kingdom; British Geological Survey, Edinburgh, United Kingdom; Biogéosciences Laboratory, Université de Bourgogne-Franche Comté, Dijon, France; UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom; School of Earth and Planetary Sciences, WA-Organic and Isotope Geochemistry Centre (WA-OIGC), Curtin University, Bentley, WA, Australia; Natural History Museum, Vienna, Austria; Alfred Wegener Institute, Helmholtz Centre of Polar and Marine Research, Bremerhaven, Germany; International Research Institute of Disaster Science, Tohoku University, Sendai, Japan; Lunar and Planetary Institute, Houston, TX, United States; Géosciences Montpellier, CNRS, Université de Montpellier, Montpellier, France; Groupe de Physico-Chimie de ĹAtmosphère, Institut de Chimie et Procédés pour l'Énergie, l'Environnement et la Sante, Université de Strasbourg, Strasbourg, France; Instituto de Geofísica, Universidad Nacional Autónoma De México, Mexico City, Mexico; School of Geographical and Earth Sciences, University of Glasgow, Glasgow, United Kingdom; Argon Isotope Facility, Scottish Universities Environmental Research Centre (SUERC), East Kilbride, United Kingdom; Department of Geology, University of Freiburg, Frieburg, Germany; Cancun, Mexico; Institut für Geologie, Universität Hamburg, Hamburg, Germany; Ocean Resources Research Center for Next Generation, Chiba Institute of Technology, Chiba, Japan; Earth and Planetary Sciences, Rutgers University, New Brunswick, NJ, United States; Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, Kochi, Japan; LeRoy Eyring Center for Solid State Science, Physical Sciences, Arizona State University, Tempe, AZ, United States; Planetary Science Institute, School of Earth Sciences, China University of Geosciences, Wuhan, China; Department of Chemistry, Toho University, Chiba, Japan; NASA, Astrobiology Institute, Mountain View, CA, United States; CNRS, Institut pour la Recherche et le Développement, Aix Marseille University, Marseille, France 7709 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048588275&doi=10.1038%2fs41586-018-0163-6&partnerID=40&md5=6e85bc0855bc8e749ce2dc49f7f91dc0 cited By 86 C.M. Lowery T.J. Bralower J.D. Owens F.J. Rodríguez-Tovar H. Jones J. Smit M.T. Whalen P. Claeys K. Farley S.P.S. Gulick J.V. Morgan S. Green E. Chenot G.L. Christeson C.S. Cockell M.J.L. Coolen L. Ferrière C. Gebhardt K. Goto D.A. Kring J. Lofi R. Ocampo-Torres L. Pérez-Cruz A.E. Pickersgill M.H. Poelchau A.S.P. Rae C. Rasmussen M. Rebolledo-Vieyra U. Riller H. Sato S.M. Tikoo N. Tomioka J. Urrutia-Fucugauchi J. Vellekoop A. Wittmann L. Xiao K.E. Yamaguchi W. Zylberman article Glikson201861 As distinct from small to medium-size impact events, large asteroid impacts producing explosions more powerful than 107 TNT-equivalent, represented by craters and rebound domes larger than about 100 km in diameter have major consequences including the triggering of major seismic events, tsunami events and extinction episodes. Such events are manifested by the Archaean ~3.25–3.24 Ga impact cluster and associated transformation from greenstone-granite terrains to semi-continental assemblages (Glikson AY, Vickers J, Earth Planet Sci Lett 241:11–20, 2006). These impact events are considered in Chap. 6. The oldest identified mega-impact is the ~3 Ga Maniitsoq structure in southwest Greenland, while younger mega-impact structures &gt;100 km in diameter include the Vredefort and Sudbury structures. Phanerozoic mega-impacts include the Woodleigh impact structure, Warburton twin structures, Chicxulub and Popigai structures. The global tectonic consequences of some of these mega-impacts are yet to be elucidated. © 2018, Springer International Publishing AG. 2018 10.1007/978-3-319-74545-9_3 Modern Approaches in Solid Earth Sciences 14 61-78 Planetary Science Institute, Australian National University, Canberra, ACT, Australia; Centre for Exploration Targeting, The University of Western Australia, Crawley, WA, Australia https://www.scopus.com/inward/record.uri?eid=2-s2.0-85044166424&doi=10.1007%2f978-3-319-74545-9_3&partnerID=40&md5=f19b4ec783e27cadedd0c1d676eaab12 cited By 0 A.Y. Glikson F. Pirajno article Weber2018393 We summarize and then build on the three decades of geological mapping and analyses done by Ray Gutschick at the Newton County (Kentland) quarry. We present our own new data and ideas on the kinematics and significance of radial faults, shock metamorphism, petrography and diagenesis of impact breccia dikes, impactite geochemistry, and a preliminary new paleomagnetically determined Jurassic age for the crater. We list and describe the stops for this field excursion. © 2018 The Geological Society of America. 2018 10.1130/2018.0051(15) GSA Field Guides 51 393-407 Department of Geology, Grand Valley State University, Allendale, MI 49401, United States; School of Geology and Geophysics, University of Oklahoma, Norman, OK, United States; Department of Lithospheric Research, University of Vienna, Althanstrasse 14, Vienna, A-1090, Austria; Natural History Museum, Burgring 7, Vienna, A-1010, Austria; Department of Geology and Geophysics, Texas A and M University, College Station, TX 77843-3115, United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062097963&doi=10.1130%2f2018.0051%2815%29&partnerID=40&md5=e827ffa77e5d6305a7e7fe11b0c19110 cited By 0 J.C. Weber R. Douglas Elmore C. Hamilton A. Alder C. Koeberl M. Pope article Chang20181323 Core samples from the Chicxulub impact structure provide insights into the formation processes of a shallow-marine-target, complex crater. Although previous studies investigated the impactites (generally suevitic and polymict breccias) of the Yaxcopoil-1 (YAX-1) drill core in the Chicxulub impact structure, the interpretation of its deposition remains controversial. Here, we analyze planar deformation features (PDFs), grain size, and abundance of shocked quartz throughout the YAX-1 impactite sequence (794–895 m in depth). PDF orientations of most quartz grains in YAX-1 impactites show a distribution of both low angles ({10 (Formula presented.) 4}, {10 (Formula presented.) 3}, {10 (Formula presented.) 2}) and high angles (orientations higher than 55° to c-axis), while the lower part of the impactite sequence contains quartz showing only PDF orientations of low angles. High-abundance, coarse-grained shocked quartz is found from the lower to middle parts of the impactites, whereas it abruptly changes to low-abundance, fine-grained shocked quartz within the upper part. In the uppermost part of the impactites, repeated oscillations in contents of these two components are observed. PDF orientation pattern suggests most of the shocked quartz grains experienced a range of shock pressure, except two samples in the lower part of impactites, which experienced only a high level of shock. We suggest that the base and lower part of the impactite sequence were formed by ejecta curtain and melt surge deposits, respectively. Our results are also consistent with the interpretation that the middle part of the impactite sequence is fallback ejecta from the impact plume. Additionally, we support the contention that massive seawater resurges into the crater occurred during the deposition of the upper and uppermost part of the impactites. © The Meteoritical Society, 2018. 2018 10.1111/maps.13082 Meteoritics and Planetary Science 53 1323-1340 Department of Earth and Planetary Science, The University of Tokyo, Faculty of Science Bldg. 1, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8654, Japan; International Research Institute of Disaster Science, Tohoku University, 468-1 Aramaki Aza-Aoba, Aoba-ku, Sendai, 980-0845, Japan 7 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85045465497&doi=10.1111%2fmaps.13082&partnerID=40&md5=d10de74b3d85f81ca1bf50daf44f02af cited By 2 Y. Chang K. Goto Y. Sekine E. Tajika article Pilles2018224 Hypervelocity impacts frequently result in the formation of dikes in the crater floor and central uplift. Impact melt-bearing dikes in large terrestrial impact basins – such as the Offset Dikes at the Sudbury impact structure – occur at a large scale, often tens of meters wide and several kilometers in length. The Offset Dikes host significant Ni–Cu–PGE deposits, which include several well-known mines, such as Totten and Copper Cliff that have been mined for nearly 100 years. The Offset Dikes typically consist of a clast- and sulfide-rich core and clast-poor margins. Their formation has been a subject of debate for decades. The most widely proposed model is the early emplacement of clast-poor impact melt shortly after the impact event, followed by the later emplacement of clast- and sulfide-rich impact melt in the center of the dike. An alternative hypothesis is that a single pulse of clast-rich impact melt flowed into the fractured target rocks and flow differentiation resulted in a clast-rich core and a clast-poor margin. In this study, we examine field and petrographic relationships of the Foy Offset Dike to better understand its emplacement. Our results show that the characteristics of the Foy Offset Dike – namely the gradational nature of the contact between the clast-rich and clast-poor phases, the alignment of clasts sub-parallel to this contact, the geochemical similarities and the presence of sulfides within both phases of the dike – are more consistent with the single injection and flow differentiation hypothesis. © 2018 Elsevier B.V. 2018 10.1016/j.epsl.2018.05.023 Earth and Planetary Science Letters 495 224-233 Department of Earth Sciences, Centre for Planetary Science and Exploration, University of Western Ontario, London, Ontario N6A 5B7, Canada; Department of Physics and Astronomy, University of Western Ontario, London, Ontario N6A 5B7, Canada; Wallbridge Mining Company Limited, 129 Fielding Road, Sudbury, ON P3Y 1L7, Canada https://www.scopus.com/inward/record.uri?eid=2-s2.0-85047251885&doi=10.1016%2fj.epsl.2018.05.023&partnerID=40&md5=9746303574732dafc5534de6fcc518b7 cited By 10 E.A. Pilles G.R. Osinski R.A.F. Grieve D. Smith J. Bailey article Glikson2018173 In this chapter we discuss hydrothermal and metasomatic processes that have taken place in impact structures, subsequent to the collapse of the transient cavity and the cooling of the melt sheet and melt rocks. Most of what follows is drawn from Pirajno et al. (Aust J Earth Sci 50:775–796, 2003), Pirajno (Aust J Earth Sci 52:587–620, 2005) and Pirajno and Van Kranendonk (Aust J Earth Sci 52:329–352, 2005), particularly for the Australian examples. The flow of hot aqueous solutions commonly results in the formation of mineral deposits. Therefore, knowledge of post-impact hydrothermal activity is important because it may have resulted in economic mineral deposits. The world-class and widely known Sudbury mineral deposits (Ni, Cu, PGE, Pb, Zn, Au) are perhaps the best and most celebrated expression of mineralization directly related to a meteorite impact (Lightfoot, Nickel sulfide ores and impact melts – origin of the Sudbury Igneous Complex. Elsevier, Amsterdam, 662pp, 2016). Several lines of evidence suggest that the giant gold deposits of the Witwatersrand in South Africa may have been reworked or even enhanced by the effects of the large Vredefort impact structure. These cases will be examined briefly in the sections that follow. Hydrothermal circulation systems associated with impact events have been reported from the Ries (Germany), Puchezh-Katunki (Russia), Jämtland (Sweden), Roter Kamm (Namibia), Manson (USA), the above-mentioned Vredefort, Kärdla (Estonia), Sudbury and Haughton (Canada) structures (Newsom et al., J Geophys Res 91:E239–E251, 1986; Koeberl et al., Geoch Cosmo Acta 53:2113–2118, 1989; Naumov, Meteoritics 28:408–409, 1993; Sturkel et al., Eur J Miner 10: 589–609, 1998; Ames et al., Geology 26: 447–450, 1998; McCarville and Crossey, Geol Soc Am Sp Pap 302:347–379, 1996); Grieve and Thierriault, Annu Rev Earth Planet Sci 28: 305–338, 2000; Osinski et al., Meteor Planet Sci 36:731–745, 2001; Molnár et al., Econ Geol 96:1645–1670, 2001; Puura et al., Impact-induced replacement of plagioclase by K-feldspar in granitoids and amphibolites at the Kärdla crater, Estonia. In: Gilmour I, Koeberl C (eds) Impacts and the early earth. Springer-Verlag, Berlin, pp 417–445, 2000 and Geochemistry of K-enriched impactites, based on drillings into the Kärdla Crater, Estonia. Geol Soc Am Abs with Programs, Denver, Oct. 2002, p 341, 2002). Recently, aspects of hydrothermal alteration in the Chicxulub impact structure have been published in Meteoritic and Space Science (Lüders and Rickers, Meteor Planet Sci 39:1187–1198, 2004; Zürcher and Kring, Meteor Planet Sci 39:1199–1222, 2004; Goto et al., Meteor Planet Sci 39:1233–1247, 2004). © 2018, Springer International Publishing AG. 2018 10.1007/978-3-319-74545-9_7 Modern Approaches in Solid Earth Sciences 14 173-205 Planetary Science Institute, Australian National University, Canberra, ACT, Australia; Centre for Exploration Targeting, The University of Western Australia, Crawley, WA, Australia https://www.scopus.com/inward/record.uri?eid=2-s2.0-85044126254&doi=10.1007%2f978-3-319-74545-9_7&partnerID=40&md5=00dcdc50750e9dbaa378e32946cd11c4 cited By 0 A.Y. Glikson F. Pirajno article Vellekoop2018683 The Chicxulub asteroid impact at the Cretaceous-Paleogene (K-Pg) boundary resulted in one of the most abrupt global warming events in the past 100 m.y., presenting an analogue to current global warming. Here, we present high-resolution geochemical, micropaleontological, and palynological records of the Brazos-1 (Texas, USA), Stevns Klint (Denmark), and Caravaca (Spain) K-Pg boundary sections to assess the rapid environmental changes during the global warming following the brief K-Pg boundary impact winter. Warming during the first millennia after the impact is associated with hypoxic bottom waters at the studied shelf sites, as indicated by molybdenum enrichments, causing major stress for benthic communities. We attribute this decline in dissolved oxygen to a combination of decreased gas solubility and ocean ventilation resulting from the warming of the sea water, and increased oxygen demand in shelf bottom waters due to increased nutrient inputs and associated high productivity. © 2018 Geological Society of America. 2018 10.1130/G45000.1 Geology 46 683-686 Department of Earth and Environmental Sciences, KU Leuven, Heverlee, 3001, Belgium; Analytical, Environmental and Geo-Chemistry (AMGC), Vrije Universiteit Brussel, Brussels, B-1050, Belgium; Department of Earth Sciences, Utrecht University, Utrecht, 3508 TA, Netherlands; Department of Earth, Life and Environmental Sciences, University of Urbino 'Carlo Bo', Urbino, 61029, Italy; Department of Sedimentology and Marine Geology, VU University Amsterdam, Amsterdam, 1018HV, Netherlands 8 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050501777&doi=10.1130%2fG45000.1&partnerID=40&md5=f8835f60e053533d1a9b1063ecb4b11c cited By 25 J. Vellekoop L. Woelders N.A.G.M. Helmond S. Galeotti J. Smit C.P. Slomp H. Brinkhuis P. Claeys R.P. Speijer article Christeson20181 Joint International Ocean Discovery Program and International Continental Scientific Drilling Program Expedition 364 drilled into the peak ring of the Chicxulub impact crater. We present P-wave velocity, density, and porosity measurements from Hole M0077A that reveal unusual physical properties of the peak-ring rocks. Across the boundary between post-impact sedimentary rock and suevite (impact melt-bearing breccia) we measure a sharp decrease in velocity and density, and an increase in porosity. Velocity, density, and porosity values for the suevite are 2900–3700 m/s, 2.06–2.37 g/cm3, and 20–35%, respectively. The thin (25 m) impact melt rock unit below the suevite has velocity measurements of 3650–4350 m/s, density measurements of 2.26–2.37 g/cm3, and porosity measurements of 19–22%. We associate the low velocity, low density, and high porosity of suevite and impact melt rock with rapid emplacement, hydrothermal alteration products, and observations of pore space, vugs, and vesicles. The uplifted granitic peak ring materials have values of 4000–4200 m/s, 2.39–2.44 g/cm3, and 8–13% for velocity, density, and porosity, respectively; these values differ significantly from typical unaltered granite which has higher velocity and density, and lower porosity. The majority of Hole M0077A peak-ring velocity, density, and porosity measurements indicate considerable rock damage, and are consistent with numerical model predictions for peak-ring formation where the lithologies present within the peak ring represent some of the most shocked and damaged rocks in an impact basin. We integrate our results with previous seismic datasets to map the suevite near the borehole. We map suevite below the Paleogene sedimentary rock in the annular trough, on the peak ring, and in the central basin, implying that, post impact, suevite covered the entire floor of the impact basin. Suevite thickness is 100–165 m on the top of the peak ring but 200 m in the central basin, suggesting that suevite flowed downslope from the collapsing central uplift during and after peak-ring formation, accumulating preferentially within the central basin. © 2018 Elsevier B.V. 2018 10.1016/j.epsl.2018.05.013 Earth and Planetary Science Letters 495 1-11 University of Texas Institute for Geophysics, Jackson School of Geosciences, Austin, United States; Department of Geological Sciences, Jackson School of Geosciences, Austin, United States; Department of Earth Science and Engineering, Imperial College, London, United Kingdom; Alfred Wegener Institute Helmholtz Centre of Polar and Marine Research, Bremerhaven, Germany; Lunar and Planetary Institute, Houston, United States; Department of Geology, University of Leicester, United Kingdom; Géosciences Montpellier, Université de Montpellier, France; Department of Physics, University of Alberta, Canada; Department of Geology, University of Freiburg, Germany; SM 312, Mza 7, Chipre 5, Resid. Isla Azul, Cancun, Quintana Roo, Mexico; Institut für Geologie, Universität Hamburg, Germany; Eyring Materials Center, Arizona State University, Tempe, United States; Department of Geosciences, Pennsylvania State University, University Park, United States; Biogéosciences Laboratory, Université de Bourgogne-Franche Comté, France; Analytical, Environmental and Geo-Chemistry, Vrije Universiteit Brussel, Brussels, Belgium; School of Physics and Astronomy, University of Edinburgh, United Kingdom; Department of Chemistry, WA-Organic and Isotope Geochemistry Centre (WA-OIGC), Curtin University, Bentley, Australia; Natural History Museum, Vienna, Austria; British Geological Survey, Edinburgh, United Kingdom; International Research Institute of Disaster Science, Tohoku University, Sendai, Japan; United Kingdom Hydrographic Office, Taunton, United Kingdom; Groupe de Physico-Chimie de l'Atmosphère, L'Institut de Chimie et Procédés pour l'Énergie, l'Environnement et la Santé (ICPEES), Université de Strasbourg, France; Instituto de Geofísica, Universidad Nacional Autónoma De México, Ciudad de México, Mexico; School of Geographical and Earth Sciences, University of Glasgow, United Kingdom; Argon Isotope Facility, Scottish Universities Environmental Research Centre (SUERC), East Kilbride, United Kingdom; Department of Geology and Geophysics, University of Utah, Salt Lake City, United States; Japan Agency for Marine–Earth Science and Technology, Kanagawa, Japan; Faculty of Earth and Life Sciences (FALW), Vrije Universiteit, Amsterdam, Netherlands; Earth and Planetary Sceinces, Rutgers University, New Brunswick, United States; Kochi Institute for Core Sample Research, Japan Agency for Marine–Earth Science and Technology, Kochi, Japan; Department of Geosciences, University of Alaska, Fairbanks, United States; School of Earth Sciences, Planetary Science Institute, China University of Geosciences (Wuhan), China; Department of Chemistry, Toho University, Chiba, Japan; NASA Astrobiology Institute, United States; Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, United States; University of Texas Institute for Geophysics, Jackson School of Geosciences, Austin, United States; Ocean Resources Research Center for Next Generation, Chiba Institute of Technology, Chiba, Japan https://www.scopus.com/inward/record.uri?eid=2-s2.0-85047062192&doi=10.1016%2fj.epsl.2018.05.013&partnerID=40&md5=5f49ee7757f4f43bed4cd388b01f3f95 cited By 46 G.L. Christeson S.P.S. Gulick J.V. Morgan C. Gebhardt D.A. Kring E. Le Ber J. Lofi C. Nixon M. Poelchau A.S.P. Rae M. Rebolledo-Vieyra U. Riller A. Wittmann T.J. Bralower E. Chenot P. Claeys C.S. Cockell M.J.L. Coolen L. Ferrière S. Green K. Goto H. Jones C.M. Lowery C. Mellett R. Ocampo-Torres L. Pérez-Cruz A.E. Pickersgill C. Rasmussen H. Sato J. Smit S.M. Tikoo N. Tomioka J. Urrutia-Fucugauchi M.T. Whalen L. Xiao K.E. Yamaguchi article Lofi20181 Expedition 364 was a joint IODP and ICDP mission-specific platform (MSP) expedition to explore the Chicxulub impact crater buried below the surface of the Yucatán continental shelf seafloor. In April and May 2016, this expedition drilled a single borehole at Site M0077 into the crater's peak ring. Excellent quality cores were recovered from ~ 505 to ~1335m below seafloor (m b.s.f.), and high-resolution open hole logs were acquired between the surface and total drill depth. Downhole logs are used to image the borehole wall, measure the physical properties of rocks that surround the borehole, and assess borehole quality during drilling and coring operations. When making geological interpretations of downhole logs, it is essential to be able to distinguish between features that are geological and those that are operation-related. During Expedition 364 some drilling-induced and logging-related features were observed and include the following: effects caused by the presence of casing and metal debris in the hole, logging-tool eccentering, drilling-induced corkscrew shape of the hole, possible re-magnetization of low-coercivity grains within sedimentary rocks, markings on the borehole wall, and drilling-induced changes in the borehole diameter and trajectory. © Author(s) 2018. 2018 10.5194/sd-24-1-2018 Scientific Drilling 24 1-13 Géosciences Montpellier, University of Montpellier, CNRS, University of Antilles, Montpellier, France; British Geological Survey, Edinburgh, United Kingdom; DOSECC Exploration Services, Salt Lake City, UT, United States; Department of Geology, University of Leicester, United Kingdom; Department of Earth and Planetary Sciences, Rutgers UniversityNJ, United States; Centre Européen de Recherche et d'Enseignement des Géosciences de l'Environnement, Aix-en-Provence, France; Department of Physics, University of Alberta, Canada; Department of Earth, Atmospheric and Planetary Sciences, Purdue UniversityIN, United States; Institute for Geophysics and Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, TX, United States; Department of Earth Science and Engineering, Imperial College London, London, United Kingdom; Biogéosciences Laboratory, Université de Bourgogne-Franche Comté, Dijon, France; Analytical, Environmental and Geo-Chemistry, Vrije Universiteit Brussel, Brussels, Belgium; Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom; Department of Chemistry, WA-Organic and Isotope Geochemistry Centre, Curtin University, Perth, WA, Australia; Natural History Museum, Vienna, Austria; Alfred Wegener Institute Helmholtz Centre of Polar and Marine Research, Bremerhaven, Germany; International Research Institute of Disaster Science, Tohoku University, Sendai, Japan; Department of Geosciences, Pennsylvania State University, University Park, PA, United States; Lunar and Planetary Institute, Houston, TX, United States; ICPEES, Université de Strasbourg, Strasbourg, France; Instituto de Geofísica, Universidad Nacional Autónoma De México, Mexico City, Mexico; School of Geographical and Earth Sciences, University of Glasgow, Glasgow, United Kingdom; Department of Geology, University of Freiburg, Freiberg, Germany; Independent consultant, Cancun, Mexico; Institut für Geologie, Universität Hamburg, Hamburg, Germany; Japan Agency for Marine-Earth Science and Technology, Kanagawa, Japan; Faculty of Earth and Life Sciences FALW, Vrije Universiteit Amsterdam, Amsterdam, Netherlands; Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, Kochi, Japan; Department of Geosciences, University of Alaska Fairbanks, Fairbanks, AK, United States; LeRoy Eyring Center for Solid State Science, Arizona State University, Tempe, AZ, United States; School of Earth Sciences, Planetary Science Institute, China University of Geosciences, Wuhan, China; Department of Chemistry, Toho University, Chiba, Japan https://www.scopus.com/inward/record.uri?eid=2-s2.0-85055514599&doi=10.5194%2fsd-24-1-2018&partnerID=40&md5=be1f05cf2d1a0fbe00532464fb4900ee cited By 4 J. Lofi D. Smith C. Delahunty E. Le Ber L. Brun G. Henry J. Paris S. Tikoo W. Zylberman P.A. Pezard B. Célérier C. Nixon S.P.S. Gulick J.V. Morgan E. Chenot G.L. Christeson P. Claeys C.S. Cockell M.J.L. Coolen L. Ferrière C. Gebhardt K. Goto S. Green H. Jones D.A. Kring C.M. Lowery C. Mellett R. Ocampo-Torres L. Pérez-Cruz A.E. Pickersgill M. Poelchau A.S.P. Rae C. Rasmussen M. Rebolledo-Vieyra U. Riller H. Sato J. Smit N. Tomioka J. Urrutia-Fucugauchi M.T. Whalen A. Wittmann L. Xiao K.E. Yamaguchi T.J. Bralower article 2018 10.1029/2018EO104123 Eos 99 L. Joel article Grieve20171 The current record of large-scale impact on Earth consists of close to 200 impact structures and some 30 impact events recorded in the stratigraphic record, only some of which are related to known structures. It is a preservation sample of a much larger production population, with the impact rate on Earth being higher than that of the moon. This is due to the Earth’s larger physical and gravitational cross-sections, with respect to asteroidal and cometary bodies entering the inner solar system. While terrestrial impact structures have been studied as the only source of ground-truth data on impact as a planetary process, it is becoming increasingly acknowledged that large-scale impact has had its effects on the geologic history of the Earth, itself. As extremely high energy events, impacts redistribute, disrupt and reprocess target lithologies, resulting in topographic, structural and thermal anomalies in the upper crust. This has resulted in many impact structures being the source of natural resources, including some worldclass examples, such as gold and uranium at Vredefort, South Africa, Ni-Cu-PGE sulphides at Sudbury, Canada and hydrocarbons from the Campeche Bank, Mexico. Large-scale impact also has the potential to disrupt the terrestrial biosphere. The most devastating known example is the evidence for the role of impact in the Cretaceous-Paleocene (K-Pg) mass extinction event and the formation of the Chicxulub structure, Mexico. It also likely had a role in other, less dramatic, climatic excursions, such as the Paleocene-Eocene-Thermal Maximum (PETM) event. The impact rate was much higher in early Earth history and, while based on reasoned speculation, it is argued that the early surface of the Hadean Earth was replete with massive impact melt pools, in place of the large multiring basins that formed on the lower gravity moon in the same time-period. These melt pools would differentiate to form more felsic upper lithologies and, thus, are a potential source for Hadean-aged zircons, without invoking more modern geodynamic scenarios. The Earth-moon system is unique in the inner solar system and currently the best working hypothesis for its origin is a planetary-scale impact with the proto-Earth, after core formation at ca. 4.43 Ga. Future large-scale impact is a low probability event but with high consequences and has the potential to create a natural disaster of proportions unequalled by other geologic processes and threaten the extended future of human civilization, itself. © 2017 GAC/AGC®. 2017 10.12789/geocanj.2017.44.113 Geoscience Canada 44 1-26 Department of Earth Sciences, University of Western Ontario, 1151 Richmond Street, London, ON N6A 5B7, Canada 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018348620&doi=10.12789%2fgeocanj.2017.44.113&partnerID=40&md5=170a6a51f561730602fb072c911155a8 cited By 5 R.A.F. Grieve article Kring20174 The Chicxulub crater is the only wellpreserved peak-ring crater on Earth and linked, famously, to the K-T or K-Pg mass extinction event. For the first time, geologists have drilled into the peak ring of that crater in the International Ocean Discovery Program and International Continental Scientific Drilling Program (IODP-ICDP) Expedition 364. The Chicxulub impact event, the environmental calamity it produced, and the paleobiological consequences are among the most captivating topics being discussed in the geologic community. Here we focus attention on the geological processes that shaped the ~200-km-wide impact crater responsible for that discussion and the expedition's first year results. Copyright 2017, The Geological Society of America. 2017 10.1130/GSATG352A.1 GSA Today 27 4-8 Lunar and Planetary Institute, Houston, TX 77058, United States; Analytical, Environmental and Geo-Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, Brussels, 1050, Belgium; Institute for Geophysics, Dept. of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78758, United States; Dept. of Earth Science and Engineering, Imperial College LondonSW7 2AZ, United Kingdom; United States; France; United Kingdom; Australia; Austria; Germany; Japan; Mexico; Netherlands; China 10 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85032494931&doi=10.1130%2fGSATG352A.1&partnerID=40&md5=c2c21bc59483ee15f51e32b66ed72013 cited By 19 D.A. Kring P. Claeys S.P.S. Gulick J.V. Morgan G.S. Collins T. Bralower E. Chenot G. Christeson C. Cockell M.J.L. Coolen L. Ferrière C. Gebhardt K. Goto H. Jones J. Lofi C. Lowery C. Mellett R. Ocampo-Torres L. Pérez-Cruz A. Pickersgill M. Poelchau A. Rae C. Rasmussen M. Rebolledo-Vieyra U. Riller H. Sato J. Smit S. Tikoo N. Tomioka J. Urrutia-Fucugauchi M. Whalen A. Wittmann L. Xiao K.E. Yamaguchi W. Zylberman IODP-ICDP Expedition 364 Science Party article DasGupta201751 The ∼1.88 km diameter Lonar impact crater formed ∼570 ka ago and is an almost circular depression hosted entirely in the Poladpur suite of the ∼65 Ma old basalts of the Deccan Traps. To understand the effects of impact cratering on basaltic targets, commonly found on the surfaces of inner Solar System planetary bodies, major and trace element concentrations as well as Nd and Sr isotopic compositions were determined on a suite of selected samples composed of: basalts, a red bole sample, which is a product of basalt alteration, impact breccia, and impact glasses, either in the form of spherules (&lt;1 mm in diameter) or non-spherical impact glasses (&gt;1 mm and &lt;1 cm). These data include the first highly siderophile element (HSE) concentrations for the Lonar spherules. The chemical index of alteration (CIA) values for the basalts and impact breccia (36.4–42.7) are low while the red bole sample shows a high CIA value (55.6 in the acid-leached sample), consistent with its origin by aqueous alteration of the basalts. The Lonar spherules are classified into two main groups based on their CIA values. Most spherules show low CIA values (Group 1: 34.7–40.5) overlapping with the basalts and impact breccia, while seven spherules show significantly higher CIA values (Group 2: &gt;43.0). The Group 1 spherules are further subdivided into Groups 1a and 1b, with Group 1a spherules showing higher Ni and mostly higher Cr compared to the Group 1b spherules. Iridium and Cr concentrations of the spherules are consistent with the admixture of 1–8 wt% of a chondritic impactor to the basaltic target rocks. The impactor contribution is most prominent in the Group 1a and Group 2 spherules, which show higher Ni/Co, Ni/Cr and Cr/Co ratios compared to the target basalts. In contrast, the Group 1b spherules show major and trace element compositions that overlap with those of the impact breccia and are characterized by high EFTh (Enrichment Factor for Th defined as the Nb-normalized concentration of Th relative to that of the average basalt) as well as fractionated La/Sm(N), and higher large ion lithophile element (LILE) concentrations compared to the basalts. The relatively more radiogenic Sr and less radiogenic Nd isotopic composition of the impact breccia and non-spherical impact glasses compared to the target basalts are consistent with melting and mixing of the Precambrian basement beneath the Deccan basalt with up to 15 wt% contribution of the basement to these samples. Variations in the moderately siderophile element (MSE) concentration ratios of the impact breccia as well as all the spherules are best explained by contributions from three components – a chondritic impactor, the basaltic target rocks at Lonar and the basement underlying the Deccan basalts. The large variations in concentrations of volatile elements like Zn and Cu and correlated variations of EFCu-EFZn, EFPb-EFZn, EFK-EFZn and EFNa-EFZn, particularly in the Group 1a spherules, are best explained by evaporation-condensation effects during impact. While most spherules, irrespective of their general major and trace element composition, show a loss in volatile elements (e.g., Zn and Cu) relative to the target basalts, some spherules, mainly of Group 1, display enrichments in these elements that are interpreted to reflect the unique preservation of volatile-rich vapour condensates resulting from geochemical fractionation in a vertical direction within the vapour cloud. © 2017 Elsevier Ltd 2017 10.1016/j.gca.2017.07.022 Geochimica et Cosmochimica Acta 215 51-75 Centre for Earth Sciences, Indian Institute of Science, Bangalore, 560012, India; Vrije Universiteit Brussel, Analytical-, Environmental- & Geo-Chemistry, Pleinlaan 2, Brussels, 1050, Belgium; Ghent University, Department of Analytical Chemistry, Campus Sterre, Krijgslaan, 281 – S12, Ghent, 9000, Belgium https://www.scopus.com/inward/record.uri?eid=2-s2.0-85026498285&doi=10.1016%2fj.gca.2017.07.022&partnerID=40&md5=7153de6833c6a68026675473f838e2f9 cited By 13 R. Das Gupta A. Banerjee S. Goderis P. Claeys F. Vanhaecke R. Chakrabarti article Pati2017722 The Paleoproterozoic Dhala structure with an estimated diameter of ~11 km is a confirmed complex impact structure located in the central Indian state of Madhya Pradesh in predominantly granitic basement (2.65 Ga), in the northwestern part of the Archean Bundelkhand craton. The target lithology is granitic in composition but includes a variety of meta-supracrustal rock types. The impactites and target rocks are overlain by ~1.7 Ga sediments of the Dhala Group and the Vindhyan Supergroup. The area was cored in more than 70 locations and the subsurface lithology shows pseudotachylitic breccia, impact melt breccia, suevite, lithic breccias, and postimpact sediments. Despite extensive erosion, the Dhala structure is well preserved and displays nearly all the diagnostic microscopic shock metamorphic features. This study is aimed at identifying the presence of an impactor component in impact melt rock by analyzing the siderophile element concentrations and rhenium-osmium isotopic compositions of four samples of impactites (three melt breccias and one lithic breccia) and two samples of target rock (a biotite granite and a mafic intrusive rock). The impact melt breccias are of granitic composition. In some samples, the siderophile elements and HREE enrichment observed are comparable to the target rock abundances. The Cr versus Ir concentrations indicate the probable admixture of approximately 0.3 wt.% of an extraterrestrial component to the impact melt breccia. The Re and Os abundances and the 187Os/188Os ratio of 0.133 of one melt breccia specimen confirm the presence of an extraterrestrial component, although the impactor type characterization still remains inconclusive. © The Meteoritical Society, 2017. 2017 10.1111/maps.12826 Meteoritics and Planetary Science 52 722-736 Department of Earth and Planetary Sciences, Nehru Science Centre, University of Allahabad, Allahabad, 211 002, India; National Center of Experimental Mineralogy and Petrology, University of Allahabad, 14 Chatham Lines, Allahabad, 211 002, India; National Research Center for Geoanalysis, 26 Baiwanzhuang Dajie, Xicheng District, Beijing, 100037, China; Department of Lithospheric Research, University of Vienna, Althanstrasse 14, Vienna, A-1090, Austria; Natural History Museum, Burgring 7, Vienna, A-1010, Austria; Museum für Naturkunde – Leibniz Institute for Evolution and Biodiversity Science, Invalidenstrasse 43, Berlin, 10115, Germany; Humboldt-Universität zu Berlin, Unter den Linden 6, Berlin, 10099, Germany; Geochronology Laboratory, University of Brasilia, Brasilia, Brazil 4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85012996321&doi=10.1111%2fmaps.12826&partnerID=40&md5=248bc8d4f7dd1491af61f26aeaaa18fc cited By 15 J.K. Pati W.J. Qu C. Koeberl W.U. Reimold M. Chakarvorty R.T. Schmitt article Artemieva201710 Potentially hazardous asteroids and comets have hit Earth throughout its history, with catastrophic consequences in the case of the Chicxulub impact. Here we reexamine one of the mechanisms that allow an impact to have a global effect—the release of climate-active gases from sedimentary rocks. We use the SOVA hydrocode and model ejected materials for a sufficient time after impact to quantify the volume of gases that reach high enough altitudes (&gt; 25 km) to have global consequences. We vary impact angle, sediment thickness and porosity, water depth, and shock pressure for devolatilization and present the results in a dimensionless form so that the released gases can be estimated for any impact into a sedimentary target. Using new constraints on the Chicxulub impact angle and target composition, we estimate that 325 ± 130 Gt of sulfur and 425 ± 160 Gt CO2 were ejected and produced severe changes to the global climate. ©2017. American Geophysical Union. All Rights Reserved. 2017 10.1002/2017GL074879 Geophysical Research Letters 44 10,180-10,188 Planetary Science Institute, Tucson, AZ, United States; Department of Earth Science and Engineering, Imperial College London, London, United Kingdom 20 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85034048486&doi=10.1002%2f2017GL074879&partnerID=40&md5=9b0a881b45d734a2174e2d5e08b3ed7c cited By 60 N. Artemieva J. Morgan Expedition 364 Science Party article Shanmugam201712 At present, there are no criteria to distinguish soft-sediment deformation structures (SSDS) formed by earthquakes from SSDS formed by the other 20 triggering mechanisms (see a companion paper in Vol. 5, No. 4 of this journal by Shanmugam, 2016). Even if one believes that earthquakes are the true triggering mechanism of SSDS in a given case, the story is still incomplete. This is because earthquakes (seismic shocks) are induced by a variety of causes: 1) global tectonics and associated faults (i.e., mid-ocean ridges, trenches, and transform faults); 2) meteorite-impact events; 3) volcanic eruptions; 4) post-glacial uplift; 5) tsunami impact; 6) cyclonic impact; 7) landslides (mass-transport deposits); 8) tidal activity; 9) sea-level rise; 10) erosion; and 11) fluid pumping. These different causes are important for developing SSDS. Breccias are an important group of SSDS. Although there are many types of breccias classified on the basis of their origin, five types are discussed here (fault, volcanic, meteorite impact, sedimentary-depositional, sedimentary-collapse). Although different breccia types may resemble each other, distinguishing one type (e.g., meteorite breccias) from the other types (e.g., fault, volcanic, and sedimentary breccias) has important implications. 1) Meteorite breccias are characterized by shock features (e.g., planar deformation features in mineral grains, planar fractures, high-pressure polymorphs, shock melts, etc.), whereas sedimentary-depositional breccias (e.g., debrites) do not. 2) Meteorite breccias imply a confined sediment distribution in the vicinity of craters, whereas sedimentary-depositional breccias imply an unconfined sediment distribution, variable sediment transport, and variable sediment provenance. 3) Meteorite, volcanic, and fault breccias are invariably subjected to diagenesis and hydrothermal mineralization with altered reservoir quality, whereas sedimentary-depositional breccias exhibit primary (unaltered) reservoir quality. And finally, 4) sedimentary-collapse breccias are associated with economic mineralization (e.g., uranium ore), whereas sedimentary-depositional breccias are associated with petroleum reservoirs. Based on this important group of SSDS with breccias, the current practice of interpreting all SSDS as “seismites” is inappropriate. Ending this practice is necessary for enhancing conceptual clarity and for advancing this research domain. © 2016 China University of Petroleum (Beijing) 2017 10.1016/j.jop.2016.09.001 Journal of Palaeogeography 6 12-44 Department of Earth and Environmental Sciences, The University of Texas at Arlington, Arlington, TX 76019, United States 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85016238193&doi=10.1016%2fj.jop.2016.09.001&partnerID=40&md5=f5a66895c1ed986c488c1d5cf345eb37 cited By 15 G. Shanmugam article Schultze2016323 Impact melt rocks from the 1.9 km diameter, simple bowl-shaped Tenoumer impact crater in Mauritania have been analyzed chemically and petrologically. They are heterogeneous and can be subdivided into three types based on melt matrix color, occurrence of lithic clast components, amount of vesiculation (melt degassing), different proportions of carbonate melt mingled into silicate melt, and bulk rock chemical composition. These heterogeneities have two main causes (1) due to the small size of the impact crater, there was probably no coherent melt pool where a homogeneous mixture of melts, derived from different target lithologies, could be created; and (2) melt rock heterogeneity occurring at the thin section scale is due to fast cooling during and after the dynamic ejection and emplacement process. The overall period of crystal growth from these diverse melts was extremely short, which provides a further indication that complete chemical equilibration of the phases could not be achieved in such short time. Melt mixing processes involved in the generation of impact melts are, thus, recorded in nonequilibrium growth features. Variable mixing processes between chemically different melt phases and the formation of hybrid melts can be observed even at millimeter scales. Due to extreme cooling rates, different mixing and mingling stages are preserved in the varied parageneses of matrix minerals and in the mineral chemistry of microlites. 40Ar39Ar step-heating chronology on specimens from three melt rock samples yielded five concordant inverse isochron ages. The inverse isochron plots show that minute amounts of inherited 40Ar* are present in the system. We calculated a weighted mean age of 1.57 ± 0.14 Ma for these new results. This preferred age represents a refinement from the previous range of 21 ka to 2.5 Ma ages based on K/Ar and fission track dating. © 2016 The Meteoritical Society. 2016 10.1111/maps.12593 Meteoritics and Planetary Science 51 323-350 Museum für Naturkunde-Leibniz-Institute of Evolution and Biodiversity Research, Invalidenstrasse 43, Berlin, 10115, Germany; Technische Universität Berlin, Institut für Mineralogie-Petrologie, Ackerstrasse 76, Berlin, 13355, Germany; JdL Centre and Department of Applied Geology, Curtin University-Western Australian Argon Isotope Facility, GPO Box U1987, Perth, WA 6845, Australia; Humboldt Universität zu Berlin, Unter den Linden 6, Berlin, 10099, Germany 2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957960639&doi=10.1111%2fmaps.12593&partnerID=40&md5=e010e496e497fe2ed43a58af654eb926 cited By 12 D.S. Schultze F. Jourdan L. Hecht W.U. Reimold R.-T. Schmitt article Darlington20162416 The Lawn Hill Impact Structure (LHIS) is located 250 km N of Mt Isa in NW Queensland, Australia, and is marked by a highly deformed dolomite annulus with an outer diameter of ~18 km, overlying low metamorphic grade siltstone, sandstone, and shale, along the NE margin of the Georgina Basin. This study provides detailed field observations from sections of the Lawn Hill annulus and adjacent areas that demonstrate a clear link between the deformation of the dolomite and the Lawn Hill impact. 40Ar-39Ar dating of impact-related melt particles provides a time of impact in the Ordovician (472 ± 8 Ma) when the Georgina Basin was an active depocenter. The timing and stratigraphic thickness of the dolomite sequence in the annulus suggest that there was possibly up to 300 m of additional sedimentary rocks on top of the currently exposed Thorntonia Limestone at the time of impact. The exposed annulus is remarkably well preserved, with preservation attributed to postimpact sedimentation. The LHIS has an atypical crater morphology with no central uplift. The heterogeneous target materials at Lawn Hill were probably low-strength, porous, and water-saturated, with all three properties affecting the crater morphology. The water-saturated nature of the carbonate unit at the time of impact is thought to have influenced the highly brecciated nature of the annulus, and restricted melt production. The impact timing raises the possibility that the Lawn Hill structure may be a member of a group of impacts resulting from an asteroid breakup that occurred in the mid-Ordovician (470 ± 6 Ma). © The Meteoritical Society, 2016. 2016 10.1111/maps.12734 Meteoritics and Planetary Science 51 2416-2440 College of Science and Engineering, James Cook University, Townsville, QLD, Australia; School of Earth and Ocean Science, Cardiff University, Cardiff, United Kingdom; School of Geosciences, Monash University, Melbourne, VIC, Australia 12 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84992359610&doi=10.1111%2fmaps.12734&partnerID=40&md5=4709c73cd17046ae21c56c4b730cfae3 cited By 13 V. Darlington T. Blenkinsop P. Dirks J. Salisbury A. Tomkins article Espinosa-Cardeña2016135 Along an east-west profile crossing the Chicxulub impact structure in northern Yucatán, México, Curie depths were obtained from statistical-spectral analysis of a grid of aeromagnetic data (256 km wide and 600 km long). These depths were corrected for flight height and depth to the sea floor to determine the geothermal gradient, assuming a temperature of 580 °C for the Curie temperature. Heat flow was then calculated from the geothermal gradients using a value of 2.67 W/m-for the mean crustal thermal conductivity. The results show a conspicuous heat flow high above on the impact basin. In this location, the heat flow is 80 mW/m2 approximately. Available offshore estimates of the depth to the crustal magnetic source bases, on the northern Yucatán platform, and onshore heat flow determination on 8 shallow bore holes, and in a 1511 m deep one, support the existence of this major high heat flow anomaly associated with the impact crater. This high heat flow might be related to the impact through: (1) an uplift of the crystalline basement rocks in the center of the crater; and (2) impact induced radioactive element concentration into the crust below the impact structure. Higher thermal conductivities at the lower crust might also play a key role. Available seismological and thermal property data are compatible with these mechanisms. © 2016 Elsevier B.V. 2016 10.1016/j.jvolgeores.2015.12.013 Journal of Volcanology and Geothermal Research 311 135-149 División de Ciencias de la Tierra, CICESE, Ensenada, Baja California, Mexico; Instituto de Geofísica, Universidad Nacional Autónoma de México, D.F. México, Mexico; University of Alberta, Canada https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957916324&doi=10.1016%2fj.jvolgeores.2015.12.013&partnerID=40&md5=3882a548ca146c62b8dabc3b3f5c04ca cited By 4 J.M. Espinosa-Cardeña J.O. Campos-Enríquez M. Unsworth article Sato201636 Positive platinum group element (PGE) concentration and negative Os isotope anomalies reported from a claystone layer in the Upper Triassic bedded chert succession of the Sakahogi section, Mino Belt, central Japan, are thought to have been derived from an impact event. Stratigraphic variations and concentrations of PGE were examined in the Sakahogi section to determine the type of the impactor. Upper Triassic claystone layers, where PGE anomalies have been newly discovered in bedded chert successions in southwest Japan, were also examined. These include (i) the Unuma section in the Inuyama area, Mino Belt; (ii) the Hisuikyo section in the Kamiaso area, Mino Belt; and (iii) the Enoura section in the Tsukumi area, Chichibu Belt. Radiolarian and conodont biostratigraphic data indicate that these claystone layers are of upper-middle Norian age. Reconstruction of bedded chert in these sections suggests that they originate from open-ocean pelagic deep-sea sediments deposited in the Panthalassa Ocean.The relatively flat CI chondrite-normalized patterns of the least mobile PGEs (Ir, Ru, and Rh) and the Ru/Ir ratio determined by linear regression analysis suggest that a chondritic impactor is the source of the PGE anomalies preserved in claystone samples from the study sections. Although Ru/Ir ratios cannot conclusively distinguish chondrites from iron meteorites, the Cr/Ir ratios of the claystone layers range from 104 to 105, clearly indicating contribution from chondritic materials. The chondritic impactor of the suggested size (3.3-7.8km in diameter) implies that a large amount of debris and/or climatically active gasses (e.g., sulfur oxides) would have been released from the impactor, which would have had a marked effect on the environment. © 2015 Elsevier B.V. 2016 10.1016/j.palaeo.2015.11.015 Palaeogeography, Palaeoclimatology, Palaeoecology 442 36-47 Department of Earth and Planetary Sciences, Kyushu University, Fukuoka, 812-8581, Japan; Department of Chemistry, Tokyo Metropolitan University, Tokyo, 192-0397, Japan; Department of Earth and Environmental Sciences, Kumamoto University, Kumamoto, 860-8555, Japan; Japan Agency for Marine-Earth Science and Technology, Yokosuka, 237-0061, Japan https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949239143&doi=10.1016%2fj.palaeo.2015.11.015&partnerID=40&md5=3a2efff68d43dd82735e4860f06014db cited By 8 H. Sato N. Shirai M. Ebihara T. Onoue S. Kiyokawa article Kring2016 The Schrödinger basin on the lunar farside is â ;1/4320 km in diameter and the best-preserved peak-ring basin of its size in the Earth-Moon system. Here we present spectral and photogeologic analyses of data from the Moon Mineralogy Mapper instrument on the Chandrayaan-1 spacecraft and the Lunar Reconnaissance Orbiter Camera (LROC) on the LRO spacecraft, which indicates the peak ring is composed of anorthositic, noritic and troctolitic lithologies that were juxtaposed by several cross-cutting faults during peak-ring formation. Hydrocode simulations indicate the lithologies were uplifted from depths up to 30 km, representing the crust of the lunar farside. Through combining geological and remote-sensing observations with numerical modelling, we show that a Displaced Structural Uplift model is best for peak rings, including that in the K-T Chicxulub impact crater on Earth. These results may help guide sample selection in lunar sample return missions that are being studied for the multi-Agency International Space Exploration Coordination Group. © The Author(s) 2016. 2016 10.1038/ncomms13161 Nature Communications 7 Center for Lunar Science and Exploration, Lunar and Planetary Institute, Universities Space Research Association, 3600 Bay Area Boulevard, Houston, TX 77058, United States; Impacts and Astromaterials Research Centre, Department of Earth Science and Engineering, Imperial College London, London, SW7 2AZ, United Kingdom; Department of Geosciences, University of Alaska, Fairbanks, AK 99775, United States; Department of Earth, Environmental and Planetary Sciences, Brown University Providence, Rhode Island, 02912, United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-84992437254&doi=10.1038%2fncomms13161&partnerID=40&md5=5032a69faec571de4d14ff16f9f84282 cited By 33 D.A. Kring G.Y. Kramer G.S. Collins R.W.K. Potter M. Chandnani article Fritz20162441 A Paleoarchean impact spherule-bearing interval of the 763 m long International Continental Scientific Drilling Program (ICDP) drill core BARB5 from the lower Mapepe Formation of the Fig Tree Group, Barberton Mountain Land (South Africa) was investigated using nondestructive analytical techniques. The results of visual observation, infrared (IR) spectroscopic imaging, and micro-X-ray fluorescence (μXRF) of drill cores are presented. Petrographic and sedimentary features, as well as major and trace element compositions of lithologies from the micrometer to kilometer-scale, assisted in the localization and characterization of eight spherule-bearing intervals between 512.6 and 510.5 m depth. The spherule layers occur in a strongly deformed section between 517 and 503 m, and the rocks in the core above and below are clearly less disturbed. The μXRF element maps show that spherule layers have similar petrographic and geochemical characteristics but differences in (1) sorting of two types of spherules and (2) occurrence of primary minerals (Ni-Cr spinel and zircon). We favor a single impact scenario followed by postimpact reworking, and subsequent alteration. The spherule layers are Al2O3-rich and can be distinguished from the Al2O3-poor marine sediments by distinct Al-OH absorption features in the short wave infrared (SWIR) region of the electromagnetic spectrum. Infrared images can cover tens to hundreds of square meters of lithologies and, thus, may be used to search for Al-OH-rich spherule layers in Al2O3-poor sediments, such as Eoarchean metasediments, where the textural characteristics of the spherule layers are obscured by metamorphism. © The Meteoritical Society, 2016. 2016 10.1111/maps.12736 Meteoritics and Planetary Science 51 2441-2458 Saalbau Weltraum Projekt, Wilhelmstrasse 38, Heppenheim, 64646, Germany; Museum für Naturkunde—Leibniz Institute for Evolution and Biodiversity Science, Invalidenstrasse 43, Berlin, 10115, Germany; Bruker-Nano GmbH, Am Studio 2D, Berlin, 12489, Germany; GeoSpectral Imaging, Office E6 Block E, Somerset Office Estate, 604 Kudu Street, Allens Nek, Johannesburg, 1737, South Africa; Department of Geology, University of Johannesburg, PO Box 524, Auckland Park, Johannesburg, 2006, South Africa; Centre de Recherches Pétrographiques et Géochimiques, CRPG UMR 7358 CNRS-UL, 15 rue Notre Dame des Pauvres, Vandœuvre les Nancy, 54500, France; Institut für Erd und Umweltwissenschaften, Universität Potsdam, Karl-Liebknecht-Str. 24-25, Potsdam-Golm, 14476, Germany; Department of Lithospheric Research, University of Vienna, Althanstrasse 14, Vienna, 1090, Austria; Institut für Geologische Wissenschaften, Freie Universität Berlin (FU Berlin), Malteserstrasse 74-100, Berlin, D-12249, Germany; Natural History Museum, Burgring 7, Vienna, 1010, Austria 12 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84990866317&doi=10.1111%2fmaps.12736&partnerID=40&md5=3619380019ac2201d6de67f714f91807 cited By 14 J. Fritz R. Tagle L. Ashworth R.T. Schmitt A. Hofmann B. Luais P.D. Harris D. Hoehnel S. Özdemir T. Mohr-Westheide C. Koeberl article Abed20154025 Twenty-seven samples from Waqf as Suwwan structure in the southeastern desert of Jordan were analyzed for their petrography, mineralogy, and geochemistry. All three types of analysis failed to show any evidence supporting the structure as an impact crater, but they cannot be used as an evidence discrediting the structure as an impact crater. This is because of the presence of shatter cones and rare shock metamorphic features. Shatter cones are well established in the Waqf as Suwwan structures and are accepted internationally as a criterion for impact craters. Shock metamorphic features reported in previous works are extremely rare and atypical. Planar features (PFs) were reported in one single quartz grain taken from a 30-m-thick Kurnub sandstone horizon. They are also reported from one single loose chert nodule, despite the extremely abundant bedded and loose chert within the structure. The PFs in the chert nodule are questioned because they are possibly due to diagenesis. More important is the complete absence of any type of breccias, lithic, melt, or suevitic and ejecta within and around the structure. The "deep erosion of the crater" used by advocates cannot stand for rigorous discussion on the amount of erosion in the desert environment in southeastern Jordan. Given the exact age of the cratering event is not yet known, and an approximate long-term rate of erosion of 1 m/Ma breccias and ejecta should be present in and/or around the structure. © 2014, Saudi Society for Geosciences. 2015 10.1007/s12517-014-1427-6 Arabian Journal of Geosciences 8 4025-4037 Department of Geology, The University of Jordan, Amman, 11942, Jordan; Department of Earth and Environmental Sciences, The Hashemite University, Zarqa, Jordan 6 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930183291&doi=10.1007%2fs12517-014-1427-6&partnerID=40&md5=dfe31e2b07cf48ab20314af91279d51a cited By 3 A.M. Abed B.S. Amireh K. Al Zghoul article Delgadillo-Peralta2015145 Results of a paleomagnetic and magnetic fabrics study of the basal suevitic breccias in the Chicxulub impact crater, Yucatán platform, Gulf of Mexico are presented. The breccias were cored in the Yaxcopoil-1 borehole, which is located at about 62 km radial distance from the crater center. The impactite sequence in the Yaxcopoil-1 borehole is ~100 m thick and formed by six subunits with distinct petrographic and geochemical characteristics. Here we investigate the basal subunit interpreted as: a ground surge in the transient cavity, a melt breccia with clastic material, or an excavation flow from the ejecta curtain interacting with the ejecta plume collapse. Characterization of the magnetic fabrics using rock magnetics and anisotropy of magnetic susceptibility (AMS) are used to investigate on the emplacement mechanism of the suevites. Magnetic hysteresis and k-T curves show that the magnetic mineralogy is dominated by low-Ti titanomagnetites and magnetite. The AMS fabrics record mixtures of oblate and prolate ellipsoids and principal susceptibility axial distributions with relatively high angular scatter, related to turbulent high temperature conditions during ejecta emplacement. Magnetic fabric parameters and principal susceptibility axial distributions correlate with modal composition, relative contents and orientation of melt particles. Results are interpreted in terms of an emplacement mode as an early excavation flow that incorporated ground surge components. 2015 Revista Mexicana de Ciencias Geologicas 32 145-155 Laboratorio de Paleomagnetismo y Paleoambientes, Instituto de Geofísica, Universidad Nacional Autónoma de México, Coyoacán México D.F., 04510, Mexico 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930145698&partnerID=40&md5=ef25a10ddea591278abef6f363f4c831 cited By 3 M. Delgadillo-Peralta J. Urrutia-Fucugauchi L. Pérez-Cruz M. Velasco-Villarreal article Wittmann2015326 The Northwest Africa (NWA) 7475 meteorite is one of the several stones of paired regolith breccias from Mars based on petrography, oxygen isotope, mineral compositions, and bulk rock compositions. Its inventory of lithic clasts is dominated by vitrophyre impact melts that were emplaced while they were still molten. Other clast types include crystallized impact melt rocks, evolved plutonic rocks, possible basalts, contact metamorphosed rocks, and siltstones. Impact spherules and vitrophyre shards record airborne transport, and accreted dust rims were sintered on most clasts, presumably during residence in an ejecta plume. The clast assemblage records at least three impact events, one that formed an impact melt sheet on Mars ≤4.4 Ga ago, a second that assembled NWA 7475 from impactites associated with the impact melt sheet at 1.7-1.4 Ga, and a third that launched NWA 7475 from Mars ~5 Ma ago. Mildly shocked pyroxene and plagioclase constrain shock metamorphic conditions during launch to >5 and <15 GPa. The mild postshock-heating that resulted from these shock pressures would have been insufficient to sterilize this water-bearing lithology during launch. Magnetite, maghemite, and pyrite are likely products of secondary alteration on Mars. Textural relationships suggest that calcium-carbonate and goethite are probably of terrestrial origin, yet trace element chemistry indicates relatively low terrestrial alteration. Comparison of Mars Odyssey gamma-ray spectrometer data with the Fe and Th abundances of NWA 7475 points to a provenance in the ancient southern highlands of Mars. Gratteri crater, with an age of ~5 Ma and an apparent diameter of 6.9 km, marks one possible launch site of NWA 7475. © The Meteoritical Society, 2015. 2015 10.1111/maps.12425 Meteoritics and Planetary Science 50 326-352 Department of Earth and Planetary Sciences, Washington University in St. Louis, Campus Box 1169, 1 Brookings Dr., St. Louis, MI 63130-4899, United States; Department of Earth and Space Sciences, University of Washington, 4000 15 Avenue NE, Seattle, WA 98195, United States; Department of Earth Sciences, University of Western Ontario, 1151 Richmond Street N., London, ON N6A 5B7, Canada; Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015, United States 2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923028390&doi=10.1111%2fmaps.12425&partnerID=40&md5=7a2cb49f9dd5e88fa4100f3ad6e9cff6 cited By 76 A. Wittmann R.L. Korotev B.L. Jolliff A.J. Irving D.E. Moser I. Barker D. Rumble article Quek20152303 The Bukit Bunuh in Malaysia has recently been identified as an impact structure after the discovery of possible impact-melt-like rocks and impact breccias from this area. The impact event is believed to have occurred around 1.34-1.84 Ma. Twelve impact-related rocks from this suspected impact structure were analysed in the present study for platinum group of element (PGE) content. The sample population includes proximal impactites (two impact-melt rocks and three impact breccias) and possible impact-related rocks (four mylonites) and basement granite (three in number). The results showed no observable clear distinction between the impactites and basement granite. Compared to other asteroid impact sites in the world, the impactites and impact-related rocks in the Bukit Bunuh structure clearly contain a lower concentration of PGEs. Even though previous studies reported possible evidences of shock metamorphism in the Bukit Bunuh structure and electrical resistivity survey favoured the presence of asteroid impact structure in this area as well, the absence of a clear projectile signature in our study on PGE hinders further discussion on the existence and nature of the impact. We suggest that the absence of any PGE signature in the Bukit Bunuh impactites could be indicative either of (1) an achondrite projectile, or (2) an oblique impact or (3) the presence of a volatile-rich layer. 2015 10.18520/v109/i12/2303-2308 Current Science 109 2303-2308 Department of Geology, University of Malaya, Kuala Lumpur, 50603, Malaysia; Centre for Global Archaeological Research, Universiti Sains Malaysia, Penang, 11800, Malaysia; Institute of Petroleum Engineering, Heriot-Watt University Precinct 2, Putrajaya, 62100, Malaysia 12 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84953397795&doi=10.18520%2fv109%2fi12%2f2303-2308&partnerID=40&md5=e575bd065591609be464969ae3595296 cited By 0 L.X. Quek A.A. Ghani M.H. Badruldin M. Saidin Z.Z.T. Harith M.H. Roselee article Nuhn201565 The ~31.7-km-diameter Betio crater (23.15°S, 281.38°E), located within the Hesperian-aged Ridged Plains material in Thaumasia Planum, Mars, contains a wellpreserved asymmetrical central floor pit (~10.8 km NW-SE and ~8.8 km NE-SW in diameter) covering an area of ~67 km2 that exposes discrete megablocks of layered bedrock and preserves a variety of impact-generated deposits. High-resolution images taken by the Mars Reconnaissance Orbiter (MRO) are combined with other data sets to study and map the morphology and structure of the central floor pit. The excellent bedrock exposure of the floor pit enables the comparison of mapped structures with observations from terrestrial craters. Our mapping of the central uplift has revealed a variety of faults, folds (likely radial transpression ridges), and many breccia dikes, in addition to different types of impactites (e.g., breccias, impact melt deposits, and uplifted bedrock [i.e., parautochthonous bedrock]). Through structural mapping, we show that the central portion of the central uplift is characterized by smaller (~60- 300 m in diameter) blocks with high dips of ~45°-85°, and the outer sections of the floor pit have larger (>800 m in diameter) blocks with shallow dip angles of ~5°-15°. Our work shows that extensive brittle deformation and brecciation increase toward the center of the crater and particularly in the SW sector of the central pit. There is also an overall decrease in block size toward the center of the crater. © 2015 The Geological Society of America. All rights reserved. 2015 10.1130/2015.25184 Special Paper of the Geological Society of America 518 65-83 Department of Earth Sciences, Centre for Planetary Science and Exploration, University of Western Ontario, London, ON N6A 5B7, Canada; Department of Physics and Astronomy, University of Western Ontario, London, ON N6A 5B7, Canada; Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-84948459145&doi=10.1130%2f2015.25184&partnerID=40&md5=0cdca396b8477759c3a5fe24dd25e556 cited By 4 A.M. Nuhn L.L. Tornabene G.R. Osinski A.S. McEwen article Premović2015721 Remarkably high arsenic (As) contents have been reported in numerous Cretaceous-Paleogene boundary (KPB) clays worldwide including those from Spain (at Caravaca and Agost) and New (N.) Zealand (at Woodside Creek). Two interpretations have been offered to explain this anomaly. The first one suggests that this As was generated by the combustion of fossil fuels (such as crude oil, coal or oil shales) near the Chicxulub impact site and the second interpretation proposes the post-impact combustion of the global biomass at the KPB. Both types of combustion were presumably triggered by the Chicxulub impactor. This report shows that the estimated surface densities of As in Spain and N. Zealand strongly contradict the fossil fuel hydrocarbons/biomass hypotheses. In addition, we also show that previously reported global abundances of As at KPB are greatly overestimated. The high abundances of iron (Fe) in the ejecta layers from Spain and N. Zealand lead us to a working hypothesis that a major fraction of their anomalous As was adsorbed from seawater by the Fe-oxides. These oxides were mainly derived of Fe from the vaporized carbonaceous chondrite impactor. These were originally deposited on the local (topographically high) oxic soils in Spain and N. Zealand and then laterally transported to the KPB sites by the impactinduced surface waters. © 2015 Pavle I. Premović 2015. 2015 10.1515/geo-2015-0052 Open Geosciences 7 721-731 Laboratory for Geochemistry, Cosmochemistry and Astrochemistry, University of Niš, P.O. Box 224, Nis, 18000, Serbia 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949201109&doi=10.1515%2fgeo-2015-0052&partnerID=40&md5=f0bad5d1207df62b48203c9837fa9623 cited By 2 P.I. Premović article Larsen2015103 The origin of clays and clay minerals in the Paleocene Clayton (CF) and Porters Creek (PCF) Formations within the Mississippi embayment of central North America has been debated for more than 50 years. X-ray diffraction and petrographic analysis of samples of the CF and PCF from a mine in southeastern Missouri are used to evaluate contributions from Cretaceous-Paleogene (K-Pg) impact debris and the role of sediment diagenesis in the fine-grained sediment. Expandable clay minerals increase in abundance relative to illite and kaolinite above the K-Pg unconformity in the CF and PCF, and include dioctahedral smectite, vermiculite, and minor mixed-layered clay components, along with trioctahedral smectitic clays in the CF and lowermost PCF. Additional diagenetic phases include clinoptilolite (in the CF and lower PCF), pyrite, siderite, and opal CT (mainly in the PCF). The results of the petrographic analysis show no evidence for volcanic ash contributing directly to the sediment in the PCF. The detrital silicate minerals are mainly quartz, muscovite, biotite, and metamorphic minerals, consistent with an ancestral Appalachian Mountains source rather than volcanic ash or a Cretaceous western interior sediment source. The illite, kaolinite, dioctahedral smectite, and ordered illite-smectite mixed-layered clays are present in varying quantities in Cretaceous through Paleogene marine and nonmarine mudstones from the Mississippi embayment, and appear to be detrital in origin. Trioctahedral smectite and clinoptilolite in the CF and lowermost PCF are argued to derive from alteration of glassy impact debris; clasts in the basal CF contain microtektites replaced by trioctahedral smectitic mixed-layered clay with randomly interstratified illite. The X-ray diffraction characteristics of the vermiculite in the PCF indicate a hydroxyl-interlayered aluminous variety that is argued to have a diagenetic origin, formed by clay mineral reactions under variably anoxic conditions in the PCF sediments during early diagenesis. Throughout the CF and PCF, pyrite precipitated under reducing conditions during diagenesis, locally along with siderite replacement of micritic carbonate. In addition, opal-CT precipitated as a result of silicate reactions and dissolution of diatoms under alkaline conditions and replaced matrix and calcitic microfossils throughout much of the upper PCF. © 2015 The Geological Society of America. All rights reserved. 2015 10.1130/2015.2515(06) Special Paper of the Geological Society of America 515 103-123 Department of Earth Sciences, University of Memphis, Memphis, TN 38152, United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941754174&doi=10.1130%2f2015.2515%2806%29&partnerID=40&md5=a3f0b2042e9fa3ce38b371b36325411a cited By 0 D. Larsen D.J. Ashe J. Gustavson article Duncan2015172 New evidence suggests that seismic waves from the Chicxulub meteorite impact doubled the eruption rate of lavas on the opposite side of the planet - a combination that led to the mass extinction at the end of the Cretaceous period. © 2015 Macmillan Publishers Limited. All rights reserved. 2015 10.1038/527172a Nature 527 172-173 College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, United States 7577 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946898798&doi=10.1038%2f527172a&partnerID=40&md5=bdcd6237b27d0820738fa9ce9e548116 cited By 0 R. Duncan book Werner2015327 Impact craters on terrestrial planets are key to studying planetary geology and geophysics as well as the planetary evolution remaining as geologic features at a planet's surface. To best use the cratering record history and interpret the planetary evolution, one needs to combine a wide set of processes and parameters. This chapter reviews impact cratering processes, estimates of average impact velocities, and impact probabilities for terrestrial planets. The basics of the impact crater scaling are outlined at an up-to-date level, describing the correlation of a measured impact crater diameter and the mass and size of a body that created the impact structure. Scaling laws for large impact craters are compared with the results of the direct numerical modeling of impact cratering.The accumulation rate for impact craters on terrestrial planets is univocally considered to be constant (within a factor of 2) during the youngest 3. Ga of the solar system history, while crater-forming projectile flux evolution for the very earliest phase is debated and relates to the preferred solar system evolution concept. The intermediate flux is constrained by observations from the Earth's Moon. Different cratering chronology models are described. Measuring the number of accumulated craters at predefined sizes in a geologically outlined area of interest, one can estimate the relative and model absolute ages of the visible surface, assuming older surfaces accumulate larger number of craters. Possible challenges for this technique and the interpretation of measured size-frequency distributions of impact craters are discussed, including secondary cratering, atmospheric breakup, geologic activity, and target properties, which all modify the cratering record. © 2015 Elsevier B.V. All rights reserved. 2015 10.1016/B978-0-444-53802-4.00170-6 Treatise on Geophysics: Second Edition 10 327-365 University of Oslo, Oslo, Norway; Institute for Dynamics of Geospheres, Moscow, Russian Federation https://www.scopus.com/inward/record.uri?eid=2-s2.0-84984927548&doi=10.1016%2fB978-0-444-53802-4.00170-6&partnerID=40&md5=346c5913dfcf2112e9f5774c5f21670f cited By 26 S.C. Werner B.A. Ivanov article Whalen2014282 Stratigraphic analysis of the Yaxcopoil-1 core (Yax-1) and seismic analysis of offshore two-dimensional (2D) seismic data provide insight into the Paleogene history of the Chicxulub impact basin and Yucatàn platform development. Ten facies were identified based on core and petrographic analysis. Slope sediments include redeposited and background facies. The former are carbonate supportstones and finer-grained facies with evidence of soft sediment deformation deposited as gravity flows. Background facies are shales and mud-wackestone interpreted as sub-storm wave base suspension deposits. Depositional setting ranged from a steep bathyal slope inside the crater rim to neritic outer carbonate platform environments of the seaward prograding Yucatàn platform. Through sequence stratigraphic analysis of Yax-1, we documented five sequences based on identification of transgressive and maximum flooding surfaces and facies stacking patterns. Biostratigraphic ages are equivocal, but they imply that sequences 1 and 2 are Early Paleocene, sequences 3 and 4 are Early Eocene, and sequence 5 is Middle Eocene. Coarse-grained redeposited carbonates in lower sequences 1 to 4 indicate slope gravity flow processes. Upper sequence 3 records the first evidence of fine-grained turbidites, indicating progradation of the Yucatàn platform. By the top of sequence 4, facies indicate that the platform margin had prograded over the position of Yax-1. Seismic analysis identified six units, the lower five of which appear to correlate with cored Yax-1 sequences. The geometry and distribution of seismic units A and B indicate deposition confined to the western and central parts of the basin. Unit C, with two sets of clinoforms, records a major progradational event in the eastern part of the basin likely related to Yax-1 sequence 3 turbidites. Mainly parallel reflectors in seismic units D and E indicate relatively level bottom conditions similar to the environments of facies in upper sequence 4 and 5. The tops of units D and E, in proximal settings, are erosionally truncated. This unconformity marks the base of unit F, which is characterized by discontinuous reflectors and is restricted to the northeastern portion of the basin. Stratal patterns in seismic units C to E are more controlled by relative sea-level change, as suggested by the development of clinoforms and regional unconformities. If Chicxulub and others like the Chesapeake Bay structure are representative, large marine impacts in tectonically quiescent regions may dominate local depositional environments for millions to tens of millions of years postimpact before returning control to eustasy. Copyright © 2013 SEPM (Society for Sedimentary Geology). 2014 10.2110/sepmsp.105.04 SEPM Special Publications 105 282-304 Department of Geology and Geophysics, University of Alaska-Fairbanks, Fairbanks, AK 99775, United States; Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, J.J. Pickle Research Campus, 10100 Burnet Road, Austin, TX 78758, United States; Scripps Institution of Oceanography, 301 Vaughan Hall, MS-0244, San Diego, CA 92093, United States; Instituto de Geofisica, Universidad Nacional Autónoma de México, Ciudad Universitaria, Mexico City, CP 04510, Mexico https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957872527&doi=10.2110%2fsepmsp.105.04&partnerID=40&md5=39840355b7bf2b0c0c42d6786feea449 cited By 11 M.T. Whalen S.S.P. Gulick Z.F. Pearson R.D. Norris L.P. Cruz J.U. Fucugauchi article Popov2014896 We reanalyzed and compared unique data sets, which we obtained in the frame of combined petrophysical and geothermal investigations within scientific drilling projects on four impact structures: the Puchezh-Katunki impact structure (Vorotilovo borehole, Russia), the Ries impact structure (Noerdlingen-73 borehole, Germany), the Chicxulub impact structure (ICDP Yaxcopoil-1 borehole, Mexico), and the Chesapeake impact structure (ICDP-USGS-Eyreville borehole, USA). For a joined interpretation, we used the following previously published data: thermal properties, using the optical scanning technique, and porosities, both measured on densely sampled halfcores of the boreholes. For the two ICDP boreholes, we also used our previously published P-wave velocities measured on a subset of cores. We show that thermal conductivity, thermal anisotropy, porosity, and velocity can be correlated with shock metamorphism (target rocks of the Puchezh-Katunki and Ries impact structures), and confirm the absence of shock metamorphism in the samples taken from megablocks (Chicxulub and Chesapeake impact structure). The physical properties of the lithic impact breccias and suevites are influenced mainly by their impact-related porosity. Physical properties of lower porosity lithic impact breccias and suevites are also influenced by their chemical composition. These data allow for a distinction between different types of breccias due to differences concerning the texture and chemistry and the different amounts of melt and rock clasts. © The Meteoritical Society, 2014. 2014 10.1111/maps.12299 Meteoritics and Planetary Science 49 896-920 Schlumberger Moscow Research Centre, Moscow, Russian Federation; Department Section Geophysics, Freie Universität Berlin, Berlin, Germany; Department of Applied Geosciences, Technische Universität Berlin, Berlin, Germany; Geophysical Institute, Karlsruhe Institute of Technology, Karlsruhe, Germany 5 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900812435&doi=10.1111%2fmaps.12299&partnerID=40&md5=d9e395827c80b7e60ffcf7484bbd0884 cited By 5 Y. Popov S. Mayr R. Romushkevich H. Burkhardt H. Wilhelm article Urrutia-Fucugauchi2014100 Magnetic susceptibility logging is used to study the impact breccias in the Chicxulub crater. The basic premise is that the high contrasts in magnetic properties can be used to characterize the breccias. The Santa Elena borehole was drilled 110 km radial distance from crater center and sampled a 172 m thick sequence of impact breccias, between 332 and 504 m depth. Breccia units are distinguished from differences in composition, size, and relative contents of clasts, type of matrix and textural and lithological assemblages, which can be resolved in the susceptibility logs. The whole-core log shows characteristic variation patterns with high, intermediate and low susceptibilities. High resolution logging of matrix and clasts records the heterogeneous nature of impactites, with higher variability at smaller spatial scales. Measurements confirm that diamagnetic susceptibilities characterize the carbonate clasts, high susceptibilities the basement granitic clasts and intermediate values the silicate melt-rich and silicate-poor matrix. Intermediate variable susceptibilities characterize breccias rich in melt particles. Correlation of matrix and clast logs with whole-core log shows that signal is controlled by the matrix. Logs for clast shows a discrete distribution with peaks of intermediate to high values, which correlate with large clast distributions. The ejecta blanket includes the fallback suevites rich in silicate melt particles and shocked minerals, the high temperature vapor deposits from ejecta curtain collapse and high velocity basal flows, and the carbonate rich deposits from lateral basal flows and secondary cratering. Late fallback suevites record minor turbulent conditions resulting from progressive cooling of the ejecta plume. © 2013 Institute of Geophysics of the ASCR, v.v.i. 2014 10.1007/s11200-013-0803-0 Studia Geophysica et Geodaetica 58 100-120 Programa Universitario de Perforaciones en Océanos y Continentes, Instituto de Geofisica, Universidad Nacional Autónoma de México, Ciudad Universitaria, Coyoacan, 04510 D.F, Mexico 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893714213&doi=10.1007%2fs11200-013-0803-0&partnerID=40&md5=ab8793c484c4f4842a526175de98d4ec cited By 6 J. Urrutia-Fucugauchi L. Pérez-Cruz S.E. Campos-Arriola E. Escobar-Sánchez M. Velasco-Villarreal article Kenkmann2014156 The formation of impact craters is a highly dynamic and complex process that subjects the impacted target rocks to numerous types of deformation mechanisms. Understanding and interpreting these styles of micro-, meso- and macroscale deformation has proved itself challenging for the field of structural geology. In this paper, we give an overview of the structural inventory found in craters of all size ranges on Earth, and look into the structures of craters on other planetary bodies. Structural features are discussed here that are caused by i) extremely high pressures and temperatures that occur during the initial passage of the shock wave through the target rock and projectile, ii) the resulting flow field in the target that excavates and ejects rock materials, and iii) the gravitationally induced modification of the crater cavity into the final crater form. A special focus is put on the effects that low-angle impacting bodies have on crater formation. We hope that this review will help both planetary scientists and structural geologists understand the deformation processes and resulting structures generated by meteorite impact. © 2014. 2014 10.1016/j.jsg.2014.01.015 Journal of Structural Geology 62 156-182 Institut für Geo- und Umweltnaturwissenschaften - Geologie, Albert-Ludwigs-Universität Freiburg, Albertstraße 23-B, D-79104 Freiburg, Germany https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896866618&doi=10.1016%2fj.jsg.2014.01.015&partnerID=40&md5=4d34785764a78d1ccfcd4471a83f9006 cited By 124 T. Kenkmann M.H. Poelchau G. Wulf article Glombick2014872 Geological and geophysical evidence is presented for a newly discovered, probable remnant complex impact structure. The structure, located near Bow City, southern Alberta, has no obvious morphological expression at surface. The geometry of the structure in the shallow subsurface, mapped using downhole geophysical well logs, is a semicircular structural depression approximately 8 km in diameter with a semicircular uplifted central region. Detailed subsurface mapping revealed evidence of localized duplication of stratigraphic section in the central uplift area and omission of strata within the surrounding annular region. Field mapping of outcrop confirmed an inlier of older rocks present within the center of the structure. Evidence of deformation along the eastern margin of the central uplift includes thrust faulting, folding, and steeply dipping bedding. Normal faults were mapped along the northern margin of the annular region. Isopach maps reveal that structural thickening and thinning were accommodated primarily within the Belly River Group. Evidence from legacy 2-D seismic data is consistent with the subsurface mapping and reveals additional insight into the geometry of the structure, including a series of listric normal faults in the annular region and complex faulting within the central uplift. The absence of any ejecta blanket, breccia, suevite, or melt sheet (based on available data) is consistent with the Bow City structure being the remnant of a deeply eroded, complex impact structure. Accordingly, the Bow City structure may provide rare access and insight into zones of deformation remaining beneath an excavated transient crater in stratified siliciclastic target rocks. © The Meteoritical Society, 2014. 2014 10.1111/maps.12296 Meteoritics and Planetary Science 49 872-895 Alberta Geological Survey, Alberta Energy Regulator, 402 Twin Atria Building, 4999 - 98 Avenue, Edmonton, Alberta, T6B 2X3, Canada; Department of Physics, Institute for Geophysical Research, CCIS 4-183, University of Alberta, Edmonton, Alberta, T6G 2E1, Canada; OptaSense Canada, 10911 - 50 Street SE, Calgary, Alberta, T2C 3E5, Canada; Schlumberger Information Solutions, Kirkhill House, Aberdeen Business Park, Dyce, Aberdeen, United Kingdom; Box 1403, Fort Macleod, Alberta, T0L 0Z0, Canada 5 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900542313&doi=10.1111%2fmaps.12296&partnerID=40&md5=0b2383e1935863659cd5f9b5b6ba85f4 cited By 5 P. Glombick W. Xie T. Bown B. Hathway C. Banks conference Popov20143263 The present work summarizes the results of analysis of unique experimental data on vertical heat flow variations in different geological structures obtained from 15 scientific supper-deep and deep boreholes drilled to the depths of 1600-12 262 m within Russian and ICDP programs. The new workflow was applied for the heat flow estimation which is based on (1) precise and detailed thermal conductivity measurements on more than 30 000 cores with the new emerging technologies, (2) usage of more than 100 equilibrium and non-equilibrium temperature logs, and (3) determination of conductive heat flow component within 20-100 m intervals along every borehole studied. The data on conductive heat flow variations provides an estimate of vertical variations in the convective heat flow component. The latter reflects the information on variations in reservoir and formation properties and heat- and mass transfer processes in reservoirs and formations. It was established that a conductive component of the heat flow varies between 70 and 100% for the boreholes studied with essential (up to 100%) increase in heat flow within upper depth intervals of 2-4 km in some cases. Terrestrial heat flow values established from the measurements in deep and super-deep boreholes exceed the previous experimental heat flow estimates by 30...130% depending on a region of drilling. During the previous estimates the heat flow values were obtained from the measurements in shallow boreholes and heat flow was determined from averaging temperature gradient and thermal conductivity along boreholes. The established heat flow variations play an important role in the improvement of reliability of basin and petroleum system modeling and prediction of temperatures below the borehole depths. The use of calibrated heat flow distributions is shown to increase the confidence of such studies. Copyright © 2014, International Petroleum Technology Conference. 2014 10.2523/iptc-18095-ms Society of Petroleum Engineers - International Petroleum Technology Conference 2014, IPTC 2014 - Innovation and Collaboration: Keys to Affordable Energy 4 3263-3274 Schlumberger, Venezuela https://www.scopus.com/inward/record.uri?eid=2-s2.0-84934287259&doi=10.2523%2fiptc-18095-ms&partnerID=40&md5=b934f12a34f138fe85239cd848770b2a cited By 1 Yu. Popov E. Popov D. Miklashevskiy D. Korobkov article Wittmann20131199 El'gygytgyn is a 18km diameter, 3.6Ma old impact crater in NE Siberia. International Continental Scientific Drilling Program-El'gygytgyn hole 1C was drilled on the frozen crater lake, 2.3km from the crater center to a final depth of 517m below the lake floor. Petrographic and geochemical analyses of 26 drill core samples, three impact melt rocks from the surface, and seven glass spherules from surface deposits outside the crater are used to characterize the impactite inventory at El'gygytgyn. The bottom 98m of hole 1C intersected monomict brecciated, unshocked, rhyolitic ignimbrite with minor intercalations of polymict breccia and mafic inclusions. These lithologies are overlain by 89m of polymict breccia whose components occasionally exhibit scarce, low-degree shock metamorphic features. This unit is succeeded by 10m of suevite that contains about 1 vol% glassy impact melt shards <1cm in size and a low amount of shock metamorphosed lithic clasts. The suevite is capped by a reworked fallout deposit that constitutes a transition over 4m into lacustrine sedimentation. A higher abundance of shock metamorphosed lithic clasts, and glass spherules, some with Ni-rich spinel and admixture of an ultramafic component, characterize this unit. We tentatively interpret this impactite section as allochthonous breccia in the vicinity of El'gygytgyn's central ring uplift. The geochemical compositions of seven glass spherules from terrace deposits 2km outside the crater and eight spherules from the reworked fallout deposit in hole 1C show far greater variability than the composition of impact melt shards and impact melt rocks. Some of these spherules also show strong enrichments in siderophile elements. © The Meteoritical Society, 2013. 2013 10.1111/maps.12019 Meteoritics and Planetary Science 48 1199-1235 Department of Earth and Planetary Sciences, Washington University St. Louis, Campus Box 1169, 1 Brookings Dr., St. Louis, MO 63130-4899, United States; Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, TX 77058, United States; Earth System Science, Department of Geology, Vrije Universiteit Brussel, Pleinlaan 2, BE-1050 Brussels, Belgium; Department of Analytical Chemistry, Ghent University, Krijgslaan 281-S12, BE - 9000 Ghent, Belgium; Institut für Planetologie (IfP), Westfälische Wilhelms-Universität Münster (WWU), Wilhelm-Klemm-Str. 10, D-48149 Münster, Germany 7 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876407831&doi=10.1111%2fmaps.12019&partnerID=40&md5=cfe31d510535e499b160ba4116236e1b cited By 29 A. Wittmann S. Goderis P. Claeys F. Vanhaecke A. Deutsch L. Adolph article Goderis20131296 The geochemical nature of the impactites from International Continental Scientific Drilling Project-El'gygytgyn lake drill core 1C is compared with that of impact melt rock fragments collected near the western rim of the structure and literature data. Concentrations of major and trace elements, with special focus on siderophile metals Cr, Co, Ni, and the platinum group elements, and isotope ratios of osmium (Os), were determined to test the hypothesis of an ureilite impactor at El'gygytgyn. Least squares mixing calculations suggest that the upper volcanic succession of rhyolites, dacites, and andesites were the main contributors to the polymict impact breccias. Additions of 2-13.5 vol% of basaltic inclusions recovered from drill core intervals between 391.6 and 423.0 mblf can almost entirely account for the compositional differences observed for the bottom of a reworked fallout deposit at 318.9 mblf, a polymict impact breccia at 471.4 mblf, and three impact melt rock fragments. However, the measured Os isotope ratios and slightly elevated PGE content (up to 0.262 ng g-1 Ir) of certain impactite samples, for which the CI-normalized logarithmic PGE signature displays a relatively flat (i.e., chondritic) pattern, can only be explained by the incorporation of a small meteoritic contribution. This component is also required to explain the exceptionally high siderophile element contents and corresponding Ni/Cr, Ni/Co, and Cr/Co ratios of impact glass spherules and spherule fragments that were recovered from the reworked fallout deposits and from terrace outcrops of the Enmyvaam River approximately 10 km southeast of the crater center. Mixing calculations support the presence of approximately 0.05 wt% and 0.50-18 wt% of ordinary chondrite (possibly type-LL) in several impactites and in the glassy spherules, respectively. The heterogeneous distribution of the meteoritic component provides clues for emplacement mechanisms of the various impactite units. © The Meteoritical Society, 2013. 2013 10.1111/maps.12047 Meteoritics and Planetary Science 48 1296-1324 Department of Geology, Earth System Science, Vrije Universiteit Brussel, Pleinlaan 2, Brussels, BE-1050, Belgium; Department of Analytical Chemistry, Ghent University, Krijgslaan 281-S12, Ghent, BE-9000, Belgium; Department of Earth and Planetary Sciences, Washington University St. Louis, Campus Box 1169, 1 Brookings Dr., St. Louis, MO, 63130-4899, United States; Lunar and Planetary Institute, 3600 Bay Area Blvd., Houston, TX, 77058, United States; Department of Geology and Geophysics, University of Hawaii at Manoa, Honolulu, HI, United States; Department of Geology and Soil Sciences, Ghent University, Krijgslaan 281-S8, Ghent, BE-9000, Belgium; School of Agricultural, Earth and Environmental Sciences, University of KwaZulu-Natal, Durban, South Africa; Institut für Planetologie, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Str. 10, Münster, D-48149, Germany 7 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880159710&doi=10.1111%2fmaps.12047&partnerID=40&md5=df03802e99801688dea1e0c663fc3ae8 cited By 15 S. Goderis A. Wittmann J. Zaiss M. Elburg G. Ravizza F. Vanhaecke A. Deutsch P. Claeys article Mang201364 Shock experiments with pressures ranging from 3 to 30 GPa have been conducted on a mixed assemblage of hexagonal and monoclinic pyrrhotite. All samples were studied with respect to their particular shock-induced microstructures and magnetic properties at high and low temperatures. Up to 8 GPa, microstructures in shocked pyrrhotite are characterized by mechanical deformation producing a damage of the crystal structure. At pressures of 20 GPa and upward, amorphization and mechanical twinning are the dominant structural features induced by shock. Within the lower-pressure range coercivity, saturation isothermal remanent magnetization and coercivity of remanence increase with shock pressures, in agreement with more single-domain (SD)-like behavior. Simultaneously, the λ-peak of hexagonal pyrrhotite decreases and the 34 K transition of monoclinic pyrrhotite broadens and is depressed. Magnetic hardening is triggered by grain-size reduction, but also by the formation of SD within discrete multidomain grains. Planar deformation features subdivide such multidomain grains into lath-shaped domains with average sizes lying in the SD range. The planar deformation features disappear at 20 GPa and irregular, nanometer-sized "amorphous domains" occur instead. Pressure release from 30 GPa finally triggers partial melting of pyrrhotite. The sharp interfaces between molten and crystalline pyrrhotite document a rapid change of thermal conditions. Within molten pyrrhotite, quenched iron crystals occur. The presence of native iron strongly influences the magnetic properties, depending on the particular amount in the studied sample and likely affects the magnetic properties of impact lithologies on Earth and extraterrestrial material. ©2013. American Geophysical Union. All Rights Reserved. 2013 10.1029/2012GC004242 Geochemistry, Geophysics, Geosystems 14 64-85 Institut für Angewandte Geowissenschaften, Karlsruher Institut für Technologie, Adenauerring 20, Geb. 50.40, D-76131 Karlsruhe, Germany; Museum für Naturkunde, Leibniz-Institut, Humboldt Universität zu Berlin, Berlin, Germany; Laboratorium für Elektronenmikroskopie, Karlsruher Institut für Technologie, Karlsruhe, Germany 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879807327&doi=10.1029%2f2012GC004242&partnerID=40&md5=4ee9274ee3c5d51772d1bf852c98572f cited By 21 C. Mang A. Kontny J. Fritz R. Schneider article Artemieva2013590 We present the results of numerical modeling of the formation of the Ries crater utilizing the two hydrocodes SOVA and iSALE. These standard models allow us to reproduce crater shape, size, and morphology, and composition and extension of the continuous ejecta blanket. Some of these results cannot, however, be readily reconciled with observations: the impact plume above the crater consists mainly of molten and vaporized sedimentary rocks, containing very little material in comparison with the ejecta curtain; at the end of the modification stage, the crater floor is covered by a thick layer of impact melt with a total volume of 6-11 km3; the thickness of true fallback material from the plume inside the crater does not exceed a couple of meters; ejecta from all stratigraphic units of the target are transported ballistically; no separation of sedimentary and crystalline rocks-as observed between suevites and Bunte Breccia at Ries-is noted. We also present numerical results quantifying the existing geological hypotheses of Ries ejecta emplacement from an impact plume, by melt flow, or by a pyroclastic density current. The results show that none of these mechanisms is consistent with physical constraints and/or observations. Finally, we suggest a new hypothesis of suevite formation and emplacement by postimpact interaction of hot impact melt with water or volatile-rich sedimentary rocks. © The Meteoritical Society, 2013. 2013 10.1111/maps.12085 Meteoritics and Planetary Science 48 590-627 Planetary Science Institute, 1700 E. Fort Lowell Rd., Tucson, AZ, 85719, United States; Museum für Naturkunde, Leibniz Institute for Research on Evolution and Biodiversity, Invalidenstrasse 43, Berlin, 10115, Germany; Institute for the Dynamics of Geospheres, Russian Academy of Sciences, Moscow, 119334, Russian Federation; Humboldt Universität zu Berlin, Unter den Linden 6, Berlin, 10099, Germany 4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876416674&doi=10.1111%2fmaps.12085&partnerID=40&md5=260528458ab7ea8e4f841ab4e2e60513 cited By 77 N.A. Artemieva K. Wünnemann F. Krien W.U. Reimold D. Stöffler article Stöffler2013515 We report results of an interdisciplinary project devoted to the 26 km-diameter Ries crater and to the genesis of suevite. Recent laboratory analyses of "crater suevite" occurring within the central crater basin and of "outer suevite" on top of the continuous ejecta blanket, as well as data accumulated during the past 50 years, are interpreted within the boundary conditions imposed by a comprehensive new effort to model the crater formation and its ejecta deposits by computer code calculations (Artemieva et al. 2013). The properties of suevite are considered on all scales from megascopic to submicroscopic in the context of its geological setting. In a new approach, we reconstruct the minimum/maximum volumes of all allochthonous impact formations (108/116 km3), of suevite (14/22 km3), and the total volume of impact melt (4.9/8.0 km3) produced by the Ries impact event prior to erosion. These volumes are reasonably compatible with corresponding values obtained by numerical modeling. Taking all data on modal composition, texture, chemistry, and shock metamorphism of suevite, and the results of modeling into account, we arrive at a new empirical model implying five main consecutive phases of crater formation and ejecta emplacement. Numerical modeling indicates that only a very small fraction of suevite can be derived from the "primary ejecta plume," which is possibly represented by the fine-grained basal layer of outer suevite. The main mass of suevite was deposited from a "secondary plume" induced by an explosive reaction ("fuel-coolant interaction") of impact melt with water and volatile-rich sedimentary rocks within a clast-laden temporary melt pool. Both melt pool and plume appear to be heterogeneous in space and time. Outer suevite appears to be derived from an early formed, melt-rich and clast-poor plume region rich in strongly shocked components (melt ≫ clasts) and originating from an upper, more marginal zone of the melt pool. Crater suevite is obviously deposited from later formed, clast-rich and melt-poor plumes dominated by unshocked and weakly shocked clasts and derived from a deeper, central zone of the melt pool. Genetically, we distinguish between "primary suevite" which includes dike suevite, the lower sublayer of crater suevite, and possibly a basal layer of outer suevite, and "secondary suevite" represented by the massive upper sublayer of crater suevite and the main mass of outer suevite. © The Meteoritical Society, 2013. 2013 10.1111/maps.12086 Meteoritics and Planetary Science 48 515-589 Museum für Naturkunde, Leibniz Institute for Research on Evolution and Biodiversity, Invalidenstraße 43, Berlin, D-10115, Germany; Humboldt-Universität zu Berlin, Unter den Linden 6, Berlin, D-10099, Germany; Russian Academy of Sciences, Institute for the Dynamics of Geospheres, Leninskii prosp. 38/6, Moscow, 117334, Russian Federation; Planetary Science Institute, 1700 E. Fort Lowell Rd. #106, Tucson, AZ, 85719, United States 4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876415232&doi=10.1111%2fmaps.12086&partnerID=40&md5=60f7fd85850d8913147c41f8141cc552 cited By 121 D. Stöffler N.A. Artemieva K. Wünnemann W.U. Reimold J. Jacob B.K. Hansen I.A.T. Summerson article Morgan20131508 The discovery of large amounts of soot in clays deposited at the Cretaceous-Paleogene (K-Pg) boundary and linked to the ~65 Ma Chicxulub impact crater led to the hypothesis that major wildfires were a consequence of the asteroid impact. Subsequently, several lines of evidence, including the lack of charcoal in North American sites, were used to argue against global wildfires. Close to the impact site fires are likely to be directly ignited by the impact fireball, whereas globally they could be ignited by radiation from the reentry of hypervelocity ejecta. To-date, models of the latter have yet to take into account that ejection - and thus the emission of thermal radiation - is asymmetric and dependent on impact angle. Here, we model: (1) the impact and ejection of material, (2) the ballistic continuation of ejecta around a spherical Earth, and (3) the thermal pulse delivered to the Earth's surface when ejecta reenters the atmosphere. We find that thermal pulses in the downrange direction are sufficient to ignite flora several thousand kilometers from Chicxulub, whereas pulses at most sites in the uprange direction are too low to ignite even the most susceptible plant matter. Our analyses and models suggest some fires were ignited by the impact fireball and ejecta reentry, but that the nonuniform distribution of thermal radiation across the surface of the Earth is inconsistent with the ignition of fires globally as a direct and immediate result of the Chicxulub impact. Instead, we propose that the desiccation of flora by ejecta reentry, as well as the effects of postimpact global cooling/darkness, left much of the terrestrial flora prone to fires, and that the volume of soot in the global K-Pg layer is explained by a combination of syn- and postimpact wildfires. Key Points K-Pg thermal radiation from re-entering ejecta is simulated with a new 3D model Radiation varied with distance and direction from Chicxulub Wildfires were ignited in some directions, but they were not global ©2013. American Geophysical Union. All Rights Reserved. 2013 10.1002/2013JG002428 Journal of Geophysical Research: Biogeosciences 118 1508-1520 Department of Earth Science and Engineering, Imperial College London, South Knesington Campus, London, SW7 2AZ, United Kingdom; Planetary Science Institute, Tucson, AZ, United States; Institute for Dynamics of Geospheres, Moscow, Russian Federation; Department of Lithospheric Research, University of Vienna, Vienna, Austria; Nature Geoscience, Nature Publishing Group, London, United Kingdom 4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892945774&doi=10.1002%2f2013JG002428&partnerID=40&md5=82a863c4a5ac336d915367120a2d4e32 cited By 41 J. Morgan N. Artemieva T. Goldin article Goderis2013417 The discovery over 30years ago at Gubbio (Italy) and Caravaca (Spain) of an enrichment in the concentrations of iridium (Ir) and the other platinum group elements (PGE) by up to four orders of magnitude (Irmax=0.10-87ng/g) compared to average continental crustal background levels remains one of the most important discoveries in the Earth sciences. Since then, similar anomalies have been detected in more than 120 Cretaceous-Paleogene (K-Pg) boundary sites worldwide. Highly elevated Ir and other siderophile element abundances in roughly chondritic ratios are considered strong indicators for the presence of a meteoritic contribution in impact-related lithologies (melt rocks, impact ejecta material, etc.), delivered when an extraterrestrial object strikes Earth. The presented work adds 113 unpublished PGE analyses of 38 K-Pg sections worldwide to the existing literature. The analytical protocol relied on for this purpose consisted of a combination of a nickel-sulfide fire assay pre-concentration technique and subsequent trace metal determination via inductively coupled plasma-mass spectrometry (ICP-MS). Through repeated determination of key siderophile elements (i.e., Cr, Co, Ni, and PGE), the importance of sampling, nugget effects, and analytical methodologies applied becomes more apparent. Even more critically, these analytical effects are superimposed by the local syn- and post-depositional conditions that have affected the pristine meteoritic signature of the K-Pg impactor, including potential fractionation during vaporization and condensation, dissimilar PGE carrier phases, terrestrial PGE input, sedimentation rate, reworking, diagenesis, bioturbation, and chemical diffusion. While chondrite-normalized PGE patterns of individual sites appear relatively flat (i.e., chondritic), strong variations in siderophile element content and inter-element ratios exist between K-Pg locations, inter-laboratory measurements, and replicate analyses, hampering a precise projectile identification using (highly) siderophile elements. Only when considering improved databases of siderophile element concentrations in meteorites, in combination with linear regression analysis to calculate inter-element ratios from a large suite of ejecta deposit sites, the nature of the K-Pg projectile can be resolved. Application of this methodology to an extensive data set of continental and marine sites, very proximal to distal to the Chicxulub impact structure, supports a carbonaceous chondritic impactor (type CM or CO). © 2013 Elsevier Ltd. 2013 10.1016/j.gca.2013.06.010 Geochimica et Cosmochimica Acta 120 417-446 Earth System Science, Vrije Universiteit Brussel, Pleinlaan 2, BE-1050 Brussels, Belgium; Department of Analytical Chemistry, Universiteit Gent, Krijgslaan 281-S12, BE-9000 Ghent, Belgium; Bruker Nano GmbH, Schwarzschildstrasse 12, 12489 Berlin, Germany; Department of Sedimentology, Vrije Universiteit Amsterdam, de Boelelaan 1085, 1081HV Amsterdam, Netherlands; Osservatorio Geologico di Coldigioco, Cda. Coldigioco 4, 62021 Apiro (MC), Italy; Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum GFZ, Telegrafenberg, D-14473 Potsdam, Germany https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882729988&doi=10.1016%2fj.gca.2013.06.010&partnerID=40&md5=3014b4cd6b3f9a757ecb49ad01a13d3a cited By 61 S. Goderis R. Tagle J. Belza J. Smit A. Montanari F. Vanhaecke J. Erzinger P. Claeys article Mang20135195 We observed two different Verwey transition temperatures in fragments of crystalline basement rocks and impact sediments from the Chesapeake Bay impact structure, USA. Our study aims to the question if this feature can be used as shock indicator in impact craters. We distinguished three generations of magnetite. (1) Primary magnetite in crystalline basement rocks has average grain sizes up to several hundreds of micrometers and shows a regular TV at ≈ 121 K. (2) Shocked magnetite occurs in fragments of crystalline basement rocks and also in the suevite and impact breccia. These magnetites show two Verwey transitions - a regular one and a "lowerature transition" (LTV) at around 89 K. LTV is related to a small grain size fraction, whereas a larger grain size fraction (some hundreds of micrometers) causes the regular TV. The small grain size fraction contains a distinctly higher amount of superficially oxidized material due to the high surface/volume ratio, which causes a decrease of the Verwey transition temperature (LTV). (3) A secondary magnetite generation shows also two Verwey transition temperatures, one at 121 K and a LTV range between 91 and 105 K. The LTV in this generation is also linked to thin oxidized surface layers. This study shows that especially the Verwey transition temperature of small magnetite grains reacts very sensitively to surface oxidation and can therefore not be used as a reliable pressure indicator for impact structures on Earth. Key Points Reduction of Verwey transition due to nonstoichiometry Degree of nonstoichiometry triggered by grain size Surface/volume ratio crucial for reduction of Verwey transition ©2013. American Geophysical Union. All Rights Reserved. 2013 10.1002/jgrb.50291 Journal of Geophysical Research: Solid Earth 118 5195-5207 Institut für Angewandte Geowissenschaften, Karlsruher Institut für Technologie, Adenauerring 20, Geb. 50.41, Karlsruhe, D-76131, Germany 10 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84889009695&doi=10.1002%2fjgrb.50291&partnerID=40&md5=fb1a878d995dd75640733f1a885e6aaa cited By 9 C. Mang A. Kontny article Meyer2013417 The processes of formation and transport of particles in suevite during impact crater formation remain poorly understood. This paper gives a summary of the investigations at the 14.6 Ma old, 25 km wide Nördlinger Ries Crater in Southern Germany, performed during the last years. The suevite of the Ries Crater occurs in three different geological settings: (1) crater suevite in the central crater cavity inside the inner ring, (2) outer suevite on top of the continuous ejecta blanket, and (3) dikes in the crater basement and in displaced megablocks. For suevite genesis, the following processes have been discussed to-date in literature: (1) fall-back of material into the crater and its periphery upon collapse of an ejecta plume, and (2) horizontal transport of ejected material, akin to (a) an impact melt flow, (b) a pyroclastic flow, or (c) initiated by phreatomagmatic explosion. On the basis of geophysical investigations, numerical models, 3D shape fabrics, modal composition, stereometric and geochemical characteristics fi ve stages will be distinguished for the formation and deposition of the Ries Suevite: (1) an early ejecta plume, (2) a phreatomagmatic explosion after a hiatus, (3) a basal, non-erosive pyroclastic surge, (4) a pyroclastic flow, (5) a second ejecta plume with accretionary lapilli. © 2013 E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Germany. 2013 10.1127/1860-1804/2013/0019 Zeitschrift der Deutschen Gesellschaft fur Geowissenschaften 164 417-432 not available, Torstrasse 25, 10119 Berlin, Deutschland, Germany 3 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884250151&doi=10.1127%2f1860-1804%2f2013%2f0019&partnerID=40&md5=71c0740a0b588a9a0afa71f3fab294fb cited By 2 C. Meyer article Osinski2013347 It has long been suggested that hydrothermal systems might have provided habitats for the origin and evolution of early life on Earth, and possibly other planets such as Mars. In this contribution we show that most impact events that result in the formation of complex impact craters (i.e., >2-4 and >5-10. km diameter on Earth and Mars, respectively) are potentially capable of generating a hydrothermal system. Consideration of the impact cratering record on Earth suggests that the presence of an impact crater lake is critical for determining the longevity and size of the hydrothermal system. We show that there are six main locations within and around impact craters on Earth where impact-generated hydrothermal deposits can form: (1) crater-fill impact melt rocks and melt-bearing breccias; (2) interior of central uplifts; (3) outer margin of central uplifts; (4) impact ejecta deposits; (5) crater rim region; and (6) post-impact crater lake sediments. We suggest that these six locations are applicable to Mars as well. Evidence for impact-generated hydrothermal alteration ranges from discrete vugs and veins to pervasive alteration depending on the setting and nature of the system. A variety of hydrothermal minerals have been documented in terrestrial impact structures and these can be grouped into three broad categories: (1) hydrothermally-altered target-rock assemblages; (2) primary hydrothermal minerals precipitated from solutions; and (3) secondary assemblages formed by the alteration of primary hydrothermal minerals. Target lithology and the origin of the hydrothermal fluids strongly influences the hydrothermal mineral assemblages formed in these post-impact hydrothermal systems. There is a growing body of evidence for impact-generated hydrothermal activity on Mars; although further detailed studies using high-resolution imagery and multispectral information are required. Such studies have only been done in detail for a handful of martian craters. The best example so far is from Toro Crater (Marzo, G.A., Davila, A.F., Tornabene, L.L., Dohm, J.M., Fairèn, A.G., Gross, C., Kneissl, T., Bishop, J.L., Roush, T.L., Mckay, C.P. [2010]. Icarus 208, 667-683). We also present new evidence for impact-generated hydrothermal deposits within an unnamed ∼32-km diameter crater ∼350. km away from Toro and within the larger Holden Crater. Synthesizing observations of impact craters on Earth and Mars, we suggest that if there was life on Mars early in its history, then hydrothermal deposits associated with impact craters may provide the best, and most numerous, opportunities for finding preserved evidence for life on Mars. Moreover, hydrothermally altered and precipitated rocks can provide nutrients and habitats for life long after hydrothermal activity has ceased. © 2012 Elsevier Inc. 2013 10.1016/j.icarus.2012.08.030 Icarus 224 347-363 Centre for Planetary Science and Exploration, University of Western Ontario, London, ON N6A 5B7, Canada; Dept. of Earth Sciences, University of Western Ontario, London, ON N6A 5B7, Canada; Dept. of Physics and Astronomy, University of Western Ontario, London, ON N6A 5B7, Canada; School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom; Dept. of Geology, University of Aberdeen, Aberdeen AB24 3UE, United Kingdom 2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878256506&doi=10.1016%2fj.icarus.2012.08.030&partnerID=40&md5=eb6b8be9ff0c25fb218e77689c3c5947 cited By 178 G.R. Osinski L.L. Tornabene N.R. Banerjee C.S. Cockell R. Flemming M.R.M. Izawa J. McCutcheon J. Parnell L.J. Preston A.E. Pickersgill A. Pontefract H.M. Sapers G. Southam article Gulick201331 Geophysical data indicate that the 65.5 million years ago Chicxulub impact structure is a multi-ring basin, with three sets of semicontinuous, arcuate ring faults and a topographic peak ring (PR). Slump blocks define a terrace zone, which steps down from the inner rim into the annular trough. Fault blocks underlie the PR, which exhibits variable relief, due to target asymmetries. The central structural uplift is >10 km, and the Moho is displaced by 1-2 km. The working hypothesis for the formation of Chicxulub is: a 50 km radius transient cavity, lined with melt and impact breccia, formed within 10 s of the impact, and within minutes, weakened rebounding crust rose kilometers above the surface, the transient crater rim underwent localized deformation and collapsed into large slump blocks, resulting in a inner rim at 70-85 km radius, and outer ring faults at 70-130 km radius. The overheightened structural uplift collapsed outward, buried the inner slump blocks, and formed the PR. Most of the impact melt was ultimately emplaced as a coherent <3 km thick melt sheet within the central basin that shallows within the inner regions of the PR. Smaller pockets of melt flowed into the annular trough. Subsequently, slope collapse, ejecta, ground surge, and tsunami waves infilled the annular trough and annular basin with sediments up to 3 km and 900 m thick, respectively. Testing this working hypothesis requires direct observation of the impactites, within and adjacent to the PR and central basin. Key PointsA review of all geophysical data imaging ChicxulubSummary of the key features of the impact structureAn assessment of the relative timing of impact processes © 2013. American Geophysical Union. All Rights Reserved. 2013 10.1002/rog.20007 Reviews of Geophysics 51 31-52 University of Texas, Institute for Geophysics, Jackson School of Geosciences, 10100 Burnet Rd., Austin, TX 78758, United States; Bullard Laboratories, Department of Earth Sciences, University of Cambridge, Cambridge, United Kingdom; Department of Earth Sciences, University of Western Ontario, London ON, Canada; Department of Earth Science and Engineering, Imperial College London, London, United Kingdom; Instituto de Geofísica, Universidad Nacional Autõnoma de México, Ciudad Universitaria, Coyoacán, Mexico 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879075868&doi=10.1002%2frog.20007&partnerID=40&md5=bfb0665e34df7b8cbff5a8ffb6df63e9 cited By 62 S.P.S. Gulick G.L. Christeson P.J. Barton R.A.F. Grieve J.V. Morgan J. Urrutia-Fucugauchi book Lambert20131 2013 10.1002/9781118622612.ch1 Materials under Extreme Loadings: Application to Penetration and Impact 1-43 Sciences and Applications, Applied Research under Contract, Bordeaux Merignac, France; CEA Le Ripault, Monts, France https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886345132&doi=10.1002%2f9781118622612.ch1&partnerID=40&md5=585567a7d25d6cc28cec279801df43e3 cited By 0 P. Lambert H. Trumel article Reimold20131531 Suevite and melt breccia compositions in the boreholes Enkingen and Polsingen are compared with compositions of suevites from other Ries boreholes and surface locations and discussed in terms of implications for impact breccia genesis. No significant differences in average chemical compositions for the various drill cores or surface samples are noted. Compositions of suevite and melt breccia from southern and northeastern sectors of the Ries crater do not significantly differ. This is in stark contrast to the published variations between within-crater and out-of-crater suevites from northern and southern sectors of the Bosumtwi impact structure, Ghana. Locally occurring alteration overprint on drill cores-especially strong on the carbonate-impregnated suevite specimens of the Enkingen borehole-does affect the average compositions. Overall, the composition of the analyzed impact breccias from Ries are characterized by very little macroscopically or microscopically recognized sediment-clast component; the clast populations of suevite and impact melt breccia are dominated consistently by granitic and intermediate granitoid components. The Polsingen breccia is significantly enriched in a dioritic clast component. Overall, chemical compositions are of intermediate composition as well, with dioritic-granodioritic silica contents, and relatively small contributions from mafic target components. Selected suevite samples from the Enkingen core have elevated Ni, Co, Cr, and Ir contents compared with previously analyzed suevites from the Ries crater, which suggest a small meteoritic component. Platinum-group element (PGE) concentrations for some of the enriched samples indicate somewhat elevated concentrations and near-chondritic ratios of the most immobile PGE, consistent with an extraterrestrial contribution of 0.1-0.2% chondrite-equivalent. © The Meteoritical Society, 2013. 2013 10.1111/maps.12175 Meteoritics and Planetary Science 48 1531-1571 Museum für Naturkunde-Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstrasse 43, 10115 Berlin, Germany; Humboldt Universität zu Berlin, Unter den Linden 6, 10099 Berlin, Germany; School of Earth And Ocean Sciences, Cardiff University, Park Place, Cardiff CF10 3YE, United Kingdom; Department of Lithospheric Research, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria; Natural History Museum, Burgring 7, 1010 Vienna, Austria 9 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884974822&doi=10.1111%2fmaps.12175&partnerID=40&md5=d6bbb5b03ab8c406f07f657d23a47dfc cited By 9 W.U. Reimold I. Mcdonald R.-T. Schmitt B. Hansen J. Jacob C. Koeberl article Ehlmann2013329 Clays form on Earth by near-surface weathering, precipitation in water bodies within basins, hydrothermal alteration (volcanic- or impact-induced), diagenesis, metamorphism, and magmatic precipitation. Diverse clay minerals have been detected from orbital investigation of terrains on Mars and are globally distributed, indicating geographically widespread aqueous alteration. Clay assemblages within deep stratigraphic units in the Martian crust include Fe/Mg smectites, chlorites and higher temperature hydrated silicates. Sedimentary clay mineral assemblages include Fe/Mg smectites, kaolinite, and sulfate, carbonate, and chloride salts. Stratigraphic sequences with multiple clay-bearing units have an upper unit with Al-clays and a lower unit with Fe/Mg-clays. The typical restriction of clay minerals to the oldest, Noachian terrains indicates a distinctive set of processes involving water-rock interaction that was prevalent early in Mars history and may have profoundly influenced the evolution of Martian geochemical systems. Current analyses of orbital data have led to the proposition of multiple clay-formation mechanisms, varying in space and time in their relative importance. These include near-surface weathering, formation in ice-dominated near-surface groundwaters, and formation by subsurface hydrothermal fluids. Near-surface, open system formation of clays would lead to fractionation of Mars' crustal reservoir into an altered crustal reservoir and a sedimentary reservoir, potentially involving changes in the composition of Mars' atmosphere. In contrast, formation of clays in the subsurface by either aqueous alteration or magmatic cooling would result in comparatively little geochemical fractionation or interaction of Mars' atmospheric, crustal, and magmatic reservoirs, with the exception of long-term sequestration of water. Formation of clays within ice would have geochemical consequences intermediate between these endmembers. We outline the future analyses of orbital data, in situ measurements acquired within clay-bearing terrains, and analyses of Mars samples that are needed to more fully elucidate the mechanisms of martian clay formation and to determine the consequences for the geochemical evolution of the planet. © 2012 Springer Science+Business Media B.V. 2013 10.1007/s11214-012-9930-0 Space Science Reviews 174 329-364 Institut d'Astrophysique Spatiale, Université Paris-Sud, Orsay 91405, France; Division of Geological and Planetary Sciences, Jet Propulsion Laboratory, California Institute of Technology, Pasadena CA 91125, United States; IRAP, CNRS-Université Toulouse, 31400 Toulouse, France; Laboratoire Planétologie et Géodynamique de Nantes, CNRS, Université de Nantes, Nantes, France; Planetary Science Institute, Tucson AZ 85719, United States; Mineralogy, Natural History Museum, London, United Kingdom; Department of Earth and Space Sciences, Astrobiology Program, University of Washington, Seattle WA 98195, United States; School of Earth and Space Exploration, Arizona State University, Tempe AZ 85287, United States; Laboratoire IDES, UMR 8148, CNRS, 91405 Orsay, France; Astromaterials Research and Exploration Science, NASA Johnson Space Center, Houston TX 77058, United States; W.M. Keck Laboratory for Space and Planetary Simulation, Arkansas Center for Space and Planetary Science, University of Arkansas, Fayetteville AR 72701, United States 1-4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871780802&doi=10.1007%2fs11214-012-9930-0&partnerID=40&md5=83dddcf65a8769fed9d33ceaadfb85bc cited By 91 B.L. Ehlmann G. Berger N. Mangold J.R. Michalski D.C. Catling S.W. Ruff E. Chassefière P.B. Niles V. Chevrier F. Poulet article Sears20131733 In this interview, Dieter Stöffler (Fig. 1) describes how his interest in meteorites and impact craters dates from his Ph.D. studies at the University of Tübingen when it was learned that the Ries crater was formed by impact. A paper by Dieter's advisor, Wolf von Engelhardt, also triggered an interest in meteorites. After graduation, Dieter helped to establish a laboratory for high pressure mineralogy and he examined rocks from the Ries crater, which led to the concept of progressive shock metamorphism. The group also worked on newly returned Apollo samples and guided astronauts over the crater. A year at the NASA Ames Research Center taught Dieter about experimental impact research with a light-gas gun. After a few more years at Tübingen, Dieter obtained a professorship at the University of Münster where he created the Institute of Planetology, got involved in planning space missions including comet sample return, and continued high pressure mineralogy in collaboration with colleagues in Freiburg. Through several decades of research, Dieter and colleagues have documented the effects of shock on all the major rock-forming minerals and devised widely accepted schemes for the classification of shocked rocks. After the unification of Germany, Dieter became Director of the Natural History Museum in Berlin, during which he made much progress rebuilding the laboratories and the collections. Dieter also helped to create a museum and research center in the Ries crater. He received the Barringer Award of the Meteoritical Society in 1994 and several prestigious awards in Germany. © 2013 The Meteoritical Society. 2013 10.1111/maps.12179 Meteoritics and Planetary Science 48 1733-1751 Space Science and Astrobiology Division, NASA Ames Research Center/Bay Area Environmental Research Institute, MS245-3, Moffett Field, Mountain View, CA 94035, United States 9 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884939978&doi=10.1111%2fmaps.12179&partnerID=40&md5=bedd7a92e95d42fc7df9e92dd435dabc cited By 0 D.W.G. Sears article Nelson20121 The drill core from the International Continental Drill Program's Chicxulub Scientific Drilling Project Yaxcopoil-1 (Yax-1) borehole, in the annular trough of the Chicxulub crater, exhibits from 794 to 895. m a continuous sequence of impactites consisting of reworked fallout, fallout suevite, and brecciated impact melt rock. These impact breccias exhibit a complex history of deposition, fracturing, matrix emplacement and hydrothermal alteration. Detailed investigation of the mineralogy and chemistry of these breccias has led to a better understanding of the complex events involved in their formation. We find that the paragenesis of the brecciated impact melt rock (unit 5, 861-885. m) involved fracturing of melt rock and early K-metasomatism during a hydrothermal alteration episode as suggested by earlier work. However, the present work has identified the role of multiple episodes of precipitation of Mg-rich phyllosilicates and formation and dissolution of accessory minerals in a relatively high temperature (>300. °C) hydrothermal event. The earliest matrix formation event involved precipitation of Mg-rich phyllosilicate, accessory quartz, calcite, apatite, and andradite garnet from a hydrothermal fluid with a brine or seawater component. The fluid could have partly incorporated elements and shock-metamorphosed mineral phases derived from sedimentary lithologies, including calcite and dolomite that underwent complex phase transformations such as melting, decomposition and possible back-reactions. The discovery of andradite garnet in the matrix confirms the presence of an early high temperature hydrothermal event previously identified by mineralogical, stable isotope and fluid inclusion studies. The mineral assemblage, including Mg-rich saponite, suggests the involvement of seawater by comparison with similar alteration assemblages in hydrothermal systems involving seawater around the world. The presence of a later, low-temperature phase of the hydrothermal system, with different fluid chemistry is indicated by the partial dissolution of andradite garnet, and continued precipitation of matrix phyllosilicate minerals, but without the accessory quartz, abundant calcite or andradite, and without an accompanying K-metasomatism event. © 2012 Elsevier Ltd. 2012 10.1016/j.gca.2012.02.022 Geochimica et Cosmochimica Acta 86 1-20 Univ. of New Mexico MSC03 2050, Institute of Meteoritics, Dept. of Earth and Planetary Sciences, Albuquerque, NM 87131, United States; Bruker Nano GmbH, Schwarzschildstrasse 12, 12489 Berlin, Germany https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860550760&doi=10.1016%2fj.gca.2012.02.022&partnerID=40&md5=b2706d92b2fafc1d0de4ed4115b05013 cited By 11 M.J. Nelson H.E. Newsom M.N. Spilde T. Salge article Schulte2012737 The La Popa Basin in north-eastern Mexico features outstanding, continuous three-dimensional exposures of the Cretaceous-Palaeogene boundary event deposit in shallow shelf environments pierced by salt stocks. In the area to the south-east of the El Papalote diapir, the Cretaceous-Palaeogene deposit consists of two superimposed sedimentary units and erosively overlies upper Maastrichtian sand-siltstones with soft-sediment deformation and liquefaction structures. The basal unit 1 is an up to 8m thick chaotic, carbonate-rich bed that discontinuously fills incised gutters and channels. Besides abundant silicic and carbonate ejecta spherules from the Chicxulub impact, unit 1 includes large sandstone boulders and abundant shallow-water debris (for example, mud clasts, algae, bivalve shells, gastropod shells and vertebrate remains). Unit 1 is conformably overlain by unit 2. Distal to the diapir, unit 2 consists of a centimetre to decimetre-thick conglomeratic, coarse bioclast and spherule-bearing sandstone bed. Closer to the diapir, unit 2 becomes a metre-thick series of four to eight conglomeratic to fine-grained graded sandstone beds rich in shell debris and ejecta spherules. Unit 2 is conformably overlain by structureless to parallel laminated sandstone beds that may mark the return to the pre-event depositional regime. The sedimentary characteristics of the Cretaceous-Palaeogene deposit, including its erosive base, its sheet-like geometry, the presence of multiple, graded beds, evidence for upper flow regime conditions and the absence of bioturbation, support an origin by a short-term multiphase depositional event. The occurrence of soft-sediment deformation structures (for example, liquefaction) below the Cretaceous-Palaeogene deposit suggests that earthquakes were the first to occur at La Popa. Then, shelf collapse and strong backflow from the first tsunami waves may have triggered erosion and deposition by violent ejecta-rich hyperconcentrated density flows (unit 1). Subsequently, a series of concentrated density flows resulting from tsunami backwash surges may have deposited the multiple-graded bedding structures of unit 2. The specific depositional sequence and the Fe-Mg-rich as well as Si-K-rich composition of the ejecta spherules both provide a critical link to the well-known deep marine Cretaceous-Palaeogene boundary sites in the adjacent Burgos basin in north-eastern Mexico. Moreover, the pulse-like input of Chicxulub ejecta material at the base of the event deposit allows for correlation with other Cretaceous-Palaeogene boundary sites in the Gulf of Mexico and the Atlantic, as well as in Central and Northern America. The presence of diverse dinosaur and mosasur bones and teeth in the event deposit is the first observation of such remains together with Chicxulub ejecta material. These findings indicate that dinosaurs lived in the area during the latest Maastrichtian and suggest that the tsunami waves not only eroded deltas and estuaries but the coastal plain as well. © 2011 The Authors. Journal compilation © 2011 International Association of Sedimentologists. 2012 10.1111/j.1365-3091.2011.01274.x Sedimentology 59 737-765 GeoZentrum Nordbayern, Universität Erlangen, D-91054 Erlangen, Germany; Department of Sedimentary Geology, VU University of Amsterdam, Po Box 7161, 1007 MC Amsterdam, Netherlands; Institut für Planetologie, Universität Münster, D-48149 Münster, Germany; Bruker Nano GmbH, Schwarzschildstrasse 12, D-12489 Berlin, Germany 3 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84858701883&doi=10.1111%2fj.1365-3091.2011.01274.x&partnerID=40&md5=0a4a69929dc4c04dee30814691fe717e cited By 29 P. Schulte J. Smit A. Deutsch T. Salge A. Friese K. Beichel book Keller2012759 After three decades of nearly unchallenged wisdom that a large impact (Chicxulub) on Yucatan caused the end-Cretaceous mass extinction, this theory is facing its most serious challenge from the Chicxulub impact itself, as based on evidence in Texas and Mexico and from Deccan volcanism in India. Data generated from over 150 Cretaceous-Tertiary (KT) boundary sequences to date make it clear that the long-held belief in the Chicxulub impact as the sole or even major contributor to the KT mass extinction is not supported by evidence. The stratigraphic position of the Chicxulub impact ejecta spherules in NE Mexico and Texas and the impact breccia within the crater on Yucatan demonstrate that this impact predates the KTB by about 300,000 years. Planktic foraminiferal and stable isotope analyses across the primary impact ejecta layer reveal that not a single species went extinct as a result of this impact and no significant environmental changes could be determined. The catastrophic effects of this impact have been vastly overestimated. In contrast, recent advances in Deccan volcanic studies indicate three volcanic phases with the smallest at 67.5 Ma, the main phase at the end of the Maastrichtian (C29r), and the third phase in the early Danian C29r/C29n transition (Chenet et al. 2007). The main phase of eruptions occurred rapidly, was marked by the longest lava flows spanning 1500 km across India, and ended coincident with the KT boundary. The KT mass extinction may have been caused by these rapid and massive Deccan lava and gas eruptions that account for ~80% of the entire 3500 m thick Deccan lava pile. © Springer Science+Business Media B.V. 2012. 2012 10.1007/978-90-481-3428-1_25 Earth and Life: Global Biodiversity, Extinction Intervals and Biogeographic Perturbations Through Time 759-793 Department of Geosciences, Princeton University, Princeton, NJ 08544, United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-85012096265&doi=10.1007%2f978-90-481-3428-1_25&partnerID=40&md5=4088e6b0b3e8b3205108a43dcb0de6a3 cited By 32 G. Keller book Goderis2012223 2012 10.1002/9781118447307.ch15 Impact Cratering: Processes and Products 223-239 Earth System Science, Vrije Universiteit Brussel, Pleinlaan 2, BE-1050 Brussels, Belgium; Department of Analytical Chemistry, Universiteit Gent, Krijgslaan 281 - S12, BE-9000 Ghent, Belgium; Department of Geology and Geophysics, University of Hawaii at Manoa, Honolulu, HI, United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883214338&doi=10.1002%2f9781118447307.ch15&partnerID=40&md5=16a29e5b97cf929ed5805213270b3fd6 cited By 37 S. Goderis F. Paquay P. Claeys article Park201263 Platinum group element (PGE) abundances in the upper continental crust (UCC) are poorly constrained with published values varying by up to an order of magnitude. We evaluated the validity of using loess to estimate PGE abundances in the UCC by measuring these elements in seven Chinese loess samples using a precise method that combines NiS fire assay with isotope dilution. Major and trace elements of the Chinese loess show a typical upper crustal composition and PGE abundances are consistent with literature data on Chinese loess, except for Ru, which is a factor of 10 lower than published values. We suggest that the high Ru data and RuN/IrN values of Chinese loess reported by Peucker-Ehrenbrink and Jahn (2001) (Geochem. Geophys. Geosys. 2, 2001GC000172) are an analytical artifact, rather than a true geochemical characteristic of loess because likely sources of loess are not significantly enriched in Ru and transport and deposition processes cannot preferentially enrich Ru in loess. The effect of eolian fractionation on PGE abundances in loess appears to be limited because Chinese loess from different locations shows similar PGE patterns and concentrations. This conclusion is supported by strong positive correlations between the PGE (except for Pt) and other compatible elements such as Fe2O3, Ni, Cr, Co. Using a compilation of PGE data for loess from China, Argentina and Europe, including our data but excluding one sample with an anomalously high Pt content, we propose average PGE abundances for global loess of Ir = 0.022 ppb (ng/g), Ru = 0.030 ppb, Rh = 0.018 ppb, Pt = 0.599 ppb, and Pd = 0.526 ppb, and suggest that these are the best current estimates for the PGE abundances of the UCC. © 2012 Elsevier Ltd. 2012 10.1016/j.gca.2012.06.026 Geochimica et Cosmochimica Acta 93 63-76 Research School of Earth Sciences, Australian National University, Canberra 0200, ACT, Australia; State Key Laboratory of Geological Processes and Mineral Resources, Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China; State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864748372&doi=10.1016%2fj.gca.2012.06.026&partnerID=40&md5=4506b2b2e172f1b97e1d999d11ab9d81 cited By 56 J.-W. Park Z. Hu S. Gao I.H. Campbell H. Gong article Urrutia-Fucugauchi2012769 Initial results of a thermal treatment study on the anisotropy of magnetic susceptibility (AMS) of impact breccias from Chicxulub crater are used to investigate the nature of the magnetic fabrics. Chicxulub impact breccias are heterogeneous materials, with carbonate, basement and melt clasts within carbonate-rich or melt-rich matrix. Samples studied come from the carbonate-rich basal unit Lower Suevite in the Yaxcopoil-1 borehole impactite sequence (core depth interval: 885-895 m). The Lower Suevite is characterized by mixed prolate and oblate ellipsoids with shallow to steep principal susceptibility axes, which had been related to emplacement as an excavation flow with ground-surge components during the early cratering stages. Thermal treatment results in changes in the fabrics with a tendency to oblate fabrics. Stepwise thermal treatment up to 700°C reveals different behaviors for the oblate, neutral and prolate fabrics marked by changes in AMS parameters and principal susceptibility axis orientations. A sample with oblate fabrics and vertical minimum axes showed an increase of magnetic susceptibility at high temperatures, indicating formation of secondary magnetite and fabric enhancement. A sample with neutral ellipsoid showed heating-induced changes towards oblate fabrics and vertical minimum susceptibility axes. Samples characterized by prolate ellipsoids with horizontal maximum axes showed no directional changes. In a sample with apparent intermediate or inverse fabrics, vertical maximum axes showed changes to horizontal inclinations, with the intermediate and maximum axes switching positions. Changes induced by stepwise thermal treatment appear useful to characterize the fabrics of impact lithologies. Further investigation of heating-induced effects in mineralogy, grain size and textural changes is, however, required to relate the different behaviors observed after stepwise thermal treatment with the magnetic mineralogy and emplacement mode of the breccias. © 2012 Institute of Geophysics of the ASCR, v.v.i. 2012 10.1007/s11200-010-0292-3 Studia Geophysica et Geodaetica 56 769-787 Programa Universitario de Perforaciones en Oceanos y Continentes, Laboratorio de Paleomagnetismo y Paleoambientes, Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, D. Coyoacan, 04510 Mexico, Mexico 3 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864278897&doi=10.1007%2fs11200-010-0292-3&partnerID=40&md5=4bb9b77e05a22b2ed7ed983902eef564 cited By 3 J. Urrutia-Fucugauchi M. Delgadillo-Peralta L. Pérez-Cruz M. Velasco-Villarreal book Grieve201290 2012 10.1002/9781118447307.ch7 Impact Cratering: Processes and Products 90-105 Departments of Earth Sciences, Departments of Physics and Astronomy, Western University, 1151 Richmond Street, London, ON N6A 5B7, Canada; Earth Sciences Sector, Natural Resources Canada, Ottawa, Ontario K1A 0E8, Canada https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886332471&doi=10.1002%2f9781118447307.ch7&partnerID=40&md5=4755773cc9b1cf56db9e9f303b55dea7 cited By 17 R.A.F. Grieve A.M. Therriault book Kirsimäe201276 2012 10.1002/9781118447307.ch6 Impact Cratering: Processes and Products 76-89 Department of Geology, University of Tartu, Ravila 14a, Tartu 50411, Estonia; Departments of Earth Sciences, Departments of Physics and Astronomy, Western University, 1151 Richmond Street, London, ON N6A 5B7, Canada https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883244975&doi=10.1002%2f9781118447307.ch6&partnerID=40&md5=617940f70341a4e62a7bb5a88648b1d3 cited By 20 K. Kirsimäe G.R. Osinski article Poag20121 The Chickahominy Formation is the initial postimpact deposit in the 85km-diameter Chesapeake Bay impact crater, which is centered under the town of Cape Charles, Virginia, USA. The formation comprises dominantly microfossil-rich, silty, marine clay, which accumulated during the final ~1.6myr of late Eocene time. At cored sites, the Chickahominy Formation is 16.8-93.7m thick, and fills a series of small troughs and subbasins, which subdivide the larger Chickahominy basin. Nine coreholes drilled through the Chickahominy Formation (five inside the crater, two near the cratermargin, and two ~3km outside the crater) record the stratigraphic and paleoecologic succession of 301 indigenous species of benthic foraminifera, as well as associated planktonic foraminifera and bolboformids. Two hundred twenty of these benthic species are described herein, and illustrated with scanning electron photomicrographs. The Chickahominy Formation can be categorized as a single benthic foraminiferal biozone (Cibicidoides pippeni Biozone), subdivided into five subzones, in stratigraphic order from bottom to top: Bulimina jacksonensis Subzone; Lagenoglandulina virginiana Subzone; Uvigerina dumblei Subzone; Bolivina tectiformis Subzone, and; Siphonina jacksonensis Subzone. Two planktonic datums and four benthic datums provide a biochronostratigraphic framework in which to estimate the duration and temporal distribution patterns of discrete microfossil assemblages. Apaleoseral succession from pioneer to equilibrium paleocommunities reflects the temporal and spatial evolution from early unstable benthic paleoenvironments to later stable benthic paleoenvironments. Initial reoccupation of the newly formed crater basin is marked by a dramatic immigration of 32 indigenous species, which replaced the sparse, entirely reworked (allochthonous) foraminiferal assemblages of a preceding inhospitable dead zone. At all nine core sites, attainment of benthic paleoenvironmental equilibrium (29-190kyr postimpact) is signaled by a notable reduction in the number of new immigrant species arriving in the Chickahominy basin. In addition, at five sites inside the crater, early unstable benthic paleoenvironments can be differentiated from later stable benthic paleoenvironments by the presence of an agglutinated Psammosiphonella biofacies in basalChickahominy strata and a shift from short-term to long-term benthic foraminiferal generic dominance facies. Restriction of the dead zone and Psammosiphonella biofacies to intracrater sites indicates unusual benthic paleoenvironmental conditions (warm, saline bottomwater and porewater) derived from the impact, which lasted as long as ~350kyr postimpact at one site. Absence of key planktonic foraminiferal and Bolboforma species in early Chickahominy sediments indicates that detrimental effects of the impact also disturbed the upper oceanic water column for at least 80-100kyr postimpact. Nine genera (Bolivina, Uvigerina, Gyroidinoides, Globocassidulina, Angulogerina, Nuttallides, Cibicidina, Caucasina, Epistominella) and two generic groups (buliminids, stilostomellids) are the most abundant taxa among 17 generic dominance facies that characterize Chickahominy core sites. Most dominant taxa were epifaunal or shallow infaunal opportunists, which thrived under conditions of oxygen depletion (dysoxia) and high organic flux rates. After an average of ~73kyr of stressed, rapidly fluctuating paleoenvironments, which were destabilized by after-effects of the impact, most of the cored Chickahominy subbasins maintained stable, nutrient-rich, low-oxygen bottom waters and interstitial microhabitats for the remaining ~1.3myr of late Eocene time. 2012 Micropaleontology 58 1-206 U.S. Geological Survey, 384 Woods Hole Road, Woods Hole, MA 02543-1598, United States 1-2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864360305&partnerID=40&md5=cc47e77c1eaa28f62a606730ce123227 cited By 4 C.W. Poag article Vasconcelos2012 Several geophysical methods have been used for decades for the identification and exploration of impact craters. Most of them are based on seismic, potential fields and electrical data, focusing on exploration of anomalies caused by changes in physical properties or by structures associated with the formation of the crater. Gamma-ray spectrometry is usually not mentioned among the geophysical methods employed in crater studies, although it is known that impact cratering processes cause a number of physical/chemical changes in the country rocks. These changes include the remobilization of hydrothermal fluids which directly modify the composition of target rocks and, subsidiarily, of soils related to these rocks. Therefore, the distribution of radioactive elements K, Th and U has the potential to map such modifications. We present the analysis of gamma-ray signatures at the Serra da Cangalha impact structure, located in northeastern Brazil, using methods for enhancing K anomalies and also the overall gamma-ray signatures. These results provide valuable information on the distinct zones within the crater and might contribute to the understanding of hydrothermal enrichment processes produced as a result of the impact event. Copyright 2012 by the American Geophysical Union. 2012 10.1029/2011GL050525 Geophysical Research Letters 39 Institute of Geosciences, University of Campinas, Rua João Pandiá Calógeras, 51, Campinas, SP 13083-870, Brazil 4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857602659&doi=10.1029%2f2011GL050525&partnerID=40&md5=05ba9f86f513485a7b5de5f5a6d774f1 cited By 10 M.A.R. Vasconcelos E.P. Leite A.P. Crósta article Belza2012400 To better constrain the emplacement mechanism of the so-called "mega-block zone," a structurally complex unit of target rocks within the Chicxulub impact structure, the stratigraphic coherence of this zone is tested using its strontium isotopic composition. Forty-eight samples across the 616m sequence of deformed Cretaceous rocks in the lower part of the Yaxcopoil-1 core, drilled by ICDP in 2002, were analyzed for their 87Sr/ 86Sr isotope ratio. The oceanic anoxic event 2 (OAE2 event), located near the base of the core forms the only stratigraphic anchor point. From this point upward to approximately 1050m depth, the 87Sr/ 86Sr trend shows small oscillations, between approximately 0.7074 and 0.7073, characteristic of Cenomanian to Santonian values. This is followed by an increase to approximately 0.7075, similar to the one reported in the seawater strontium curve during the Campanian. Scattered Sr isotope ratios are attributed to local diagenetic effects, such as those expected from the possible presence of hot, impact-induced dikes and hydrothermal fluid flow, originating from the thick central melt sheet. The absence of Upper Maastrichtian Sr isotope values may result from the removal of upper target lithologies during the impact cratering process. Based on these results, the displaced Cretaceous sequence in Yax-1 appears to have preserved its stratigraphic coherence. During the modification stage, it probably moved as a whole into the annular basin during collapse of the crater wall, thereby breaking up into discrete units along previously weakened detachment zones. This model is consistent with the emplacement mechanism postulated by Kenkmann et al. (2004). © 2012 The Meteoritical Society. 2012 10.1111/j.1945-5100.2012.01345.x Meteoritics and Planetary Science 47 400-413 Department of Geology, Vrije Universiteit Brussels, Pleinlaan 2, BE1050 Brussels, Belgium; Department of Analytical Chemistry, Universiteit Gent, Krijgslaan 281-S12, BE9000 Ghent, Belgium 3 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859203668&doi=10.1111%2fj.1945-5100.2012.01345.x&partnerID=40&md5=232f01620d5a690d83ee42c43fcc5015 cited By 10 J. Belza S. Goderis E. Keppens F. Vanhaecke P. Claeys article Urrutia-Fucugauchi201199 The Chicxulub impact crater is part of a select group of unique geological sites, being a natural laboratory to investigate crater formation processes and global effects of large-scale impacts. Chicxulub is one of only three multi-ring craters documented in the terrestrial record and impact has been related to the global environmental/climatic effects and mass extinction that mark the Cretaceous/Paleogene (K/Pg) boundary. The crater is buried under ~1.0 km of carbonate sediments in the Yucatan peninsula. The buried structure was initially identified from geophysical surveys of the PEMEX oil exploration program in southeastern Mexico. On the surface its influence is marked by the circular ring of cenotes that have formed from differential compaction and fracturing between the impact breccias and surrounding limestone sequences. The crater is about ~200 km in rim diameter, half on-land and half off-shore with geometric center at Chicxulub Puerto, making it possible to use land, marine and aerial geophysical methods. The Yucatan carbonate platform is an ideal place to have the crater, tectonically stable with no volcanic activity, having formed by slow deposition of carbonate sediments. These characteristics permit high resolution imagery of the crater underground structure with unprecedented detail. The impact and crater formation occur instantaneously, with excavation of the crust down to ~25 km depths in fractions of a second and lower crust uplift and crater formation in the next few hundred seconds. Energy release results in intense fracturing and deformation at the target site, generating seismic waves traveling the whole Earth. Understanding the physics of impacts on planetary surfaces and modeling of crustal deformation and rheological behavior of materials at high temperatures and pressures remain major challenges in geosciences. The K/Pg ejecta layer is the only global stratigraphic marker in the geological record, allowing correlation of events worldwide. In the last 20 years much has been learned about the Chicxulub crater and the K/Pg boundary; however what is perhaps most interesting are the questions remaining, which include fundamental aspects of Chicxulub impact and its environmental effects. 2011 Geofisica Internacional 50 99-127 Proyecto Universitario de Perforaciones en Océanos y Continentes, Instituto de Geofísica, Universidad Nacional Autónoma de México, Delegación Coyoacan 04510, Mexico; Petróleos Mexicanos, PEMEX Exploración y Producción (retired), Blvd. A. Ruiz Cortines 1202, Villahermosa, Tabasco, 86030, Mexico; Facultad de Ingeniería, Universidad Nacional Autónoma de México, Delegación Coyoacan 04510, Mexico 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650813917&partnerID=40&md5=866bb9cf94dfafac2322449068c38646 cited By 34 J. Urrutia-Fucugauchi A. Camargo-Zanoguera L. Pérez-Cruz G. Pérez-Cruz article Kamo2011401 The U-Pb ages of shocked zircon crystals from the Chicxulub impact crater and Cretaceous-Paleogene (K-Pg) boundary sites in Haiti, the USA, and Canada, and the pattern of decreasing particle size with paleodistance from the crater, have been used as evidence of a genetic link between Chicxulub and the K-Pg boundary. Despite this, the inference that the K-Pg boundary layer formed as a direct consequence of the Chicxulub impact has been repeatedly questioned. Here we present U-Pb (ID-TIMS) ages and textural evidence of shock metamorphosed zircon grains from the K-Pg boundary at Caravaca, Spain, and Petriccio, Italy, that establish a causal connection between the impact and formation of the K-Pg boundary layer. The shocked zircon grains give data that produce a characteristic age pattern, which indicates a primary source age of 549.5 ± 5.7 Ma and a secondary event at the approximate time of impact at 66. Ma. The intensity of the shock features is proportional to the degree of isotopic resetting, and all textural features and ages are analytically identical to those of previously analyzed zircon from Chicxulub and K-Pg boundary sites in North America. Caravaca and Petriccio were > 8000 km from Chicxulub at the time of impact, and are therefore the farthest K-Pg sites identified that can be linked to Chicxulub through the dating of individual shocked zircon grains. We conclude that the combined age data and textural observations provide unambiguous evidence that ejecta from the Chicxulub impact formed the global K-Pg boundary layer. These data cannot be explained by the alternative scenario that the Chicxulub impact occurred ~. 300. ka prior to the K-Pg boundary. © 2011 Elsevier B.V.. 2011 10.1016/j.epsl.2011.08.031 Earth and Planetary Science Letters 310 401-408 Jack Satterly Geochronology Laboratory, Department of Geology, University of Toronto, 22 Russell St., Toronto, ON, Canada; Departamento de Geologia, Universidade Federal de Ouro Preto, Ouro Preto, Minas Gerais, 35400000, Brazil; Department of Earth Science and Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom 3-4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053376976&doi=10.1016%2fj.epsl.2011.08.031&partnerID=40&md5=4d09016b104dfa478894ee09d6ff886a cited By 30 S.L. Kamo C. Lana J.V. Morgan article Popov2011729 The results of thermal property measurements on cores from the scientific well Yaxcopoil-1 (1511 m in depth) drilled in the Chicxulub impact structure (Mexico) are described. The thermal conductivity, thermal diffusivity, volumetric heat capacity, thermal anisotropy coefficient, thermal heterogeneity factor, and, in addition, porosity and density were measured on 451 dry and water-saturated cores from the depth interval of 404-1511 m. The acoustic velocities were determined on a subgroup of representative samples. Significant vertical short- and long-scale variations of physical properties related to the grade of shock-thermal metamorphism and correlations between thermal and other physical properties are established. Rocks of the post-impact and impact complexes differ significantly in heterogeneity demonstrating that the impact complex has larger micro- heterogeneity on sample scale. The pre-impact rocks differ essentially from the impact and post-impact rocks in the thermal conductivity, thermal diffusivity, density and porosity. The thermal anisotropy of rocks of all structural-lithological complexes is very low (K = 1.02 ... 1.08), which is similar to the situation in the Puchezh-Katunk and Ries impact structures. Correlations are established between the thermal conductivity and elastic wave velocities measured in laboratory. For limestone-calcarenites, the thermal conductivity (λ) can be calculated from the compressional wave velocity (Vp) using the formula λ= 0.346 Vp + 0.844, and for dolomite-anhydrites this relation has the form λ= 0.998 Vp + 1.163 [for λ in W (m K)-1 and Vp in km s-1]. These correlations are used for downscaling of the sonic velocities to the decimetre scale. The effective medium theory is applied to invert the matrix thermal conductivity and pore/crack geometry from the thermal conductivity measured on the studied samples. Representative experimental data on the thermal properties for all lithological groups encountered by the Yaxcopoil-1 well essentially extend an existing database on the thermal properties of rocks of impact structures and can be used for determination of the heat flow density, interpretation of temperature logging data, theoretical modelling of heat and mass transfer processes and constructing thermal models of the Chicxulub impact structure as well as for the lithological interpretation. The research results confirm the necessity of dense sampling for the thermal property measurements to obtain reliable results in petrophysical and geothermal investigations of impact structure formations. © 2010 The Authors Geophysical Journal International © 2010 RAS. 2011 10.1111/j.1365-246X.2010.04839.x Geophysical Journal International 184 729-745 Moscow State Geological Prospecting University, Russian Federation; Fachgebeit Angewante Geophysik, Technische Universitaet Berlin, Sekr. ACK 2, Ackerstrasse 71-76, D-13355, Berlin, Germany; Geophysical Institute, University Karlsruhe, Germany 2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-78751542871&doi=10.1111%2fj.1365-246X.2010.04839.x&partnerID=40&md5=74ed70699096d3d674d3af7da0028881 cited By 17 Y. Popov R. Romushkevich D. Korobkov S. Mayr I. Bayuk H. Burkhardt H. Wilhelm article https://doi.org/10.1029/2011EO250001 Three decades ago, a landmark paper by Alvarez et al. [1980] proposed that an asteroid impact 65.5 million years ago was the cause of the mass extinction of about 75% of species, including the dinosaurs, at the boundary between the Cretaceous and Paleogene periods (K-Pg), formerly known as the Cretaceous-Tertiary (K-T) boundary. Alvarez et al. used geochemical studies on carbonate sequences from Italy, Denmark, and New Zealand to study the boundary layer, which was enriched in iridium and other platinum group elements (PGEs) at concentrations well above background levels. They associated these enrichments with the collision of an asteroid that injected large amounts of pulverized debris into the atmosphere, resulting in blockage of solar radiation, global cooling, and a shutdown of photosynthesis. 2011 https://doi.org/10.1029/2011EO250001 Eos, Transactions American Geophysical Union 92 209-210 25 Chicxulub impact crater, history https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2011EO250001 Jaime Urrutia-Fucugauchi Antonio Camargo-Zanoguera Ligia Pérez-Cruz article Elbra20111640 The Chicxulub structure in Mexico, one of the largest impact structures on Earth, was formed 65Ma by a hypervelocity impact that led to the large mass extinction at the K-Pg boundary. The Chicxulub impact structure is well preserved, but is buried beneath a sequence of carbonate sediments and, thus, requires drilling to obtain subsurface information. The Chicxulub Scientific Drilling Program was carried out at Hacienda Yaxcopoil in the framework of the International Continental Scientific Drilling Program in 2001-2002. The structure was cored from 404m down to 1511m, through three intervals: 794m of postimpact Tertiary sediments, a 100m thick impactite sequence, and 616m of preimpact Cretaceous rocks thought to represent a suite of megablocks. Physical property investigations show that the various lithologies, including the impactite units and the K-Pg boundary layer, can be characterized by their physical properties, which depend on either changes in fabric or on mineralogical variations. The magnetic properties show mostly dia- or paramagnetic behavior, with the exception of the impactite units that indicate the presence of ferromagnetic, probably hydrothermally deposited magnetite and pyrrhotite. The magnetic fraction contributes mainly to enhanced magnetization in the impactite lithologies and, in this way, to the observed magnetic anomalies. The shape and orientation of the magnetic grains are varied and reflect inhomogeneous fabric development and the influence of impact-related redeposition and hydrothermal activity. The Chicxulub impact occurred at the time of the reverse polarity geomagnetic chron 29R, and this finding is consistent with the age of the K-Pg boundary. © The Meteoritical Society, 2011. 2011 10.1111/j.1945-5100.2011.01253.x Meteoritics and Planetary Science 46 1640-1652 Division of Geophysics and Astronomy, Department of Physics, 00014 University of Helsinki, P.O. Box 64, Helsinki, Finland 11 https://www.scopus.com/inward/record.uri?eid=2-s2.0-80155180620&doi=10.1111%2fj.1945-5100.2011.01253.x&partnerID=40&md5=2524f21eaf8e7f86f515756d4d9940d2 cited By 13 T. Elbra L.J. Pesonen article Bartosova2011396 The center of the 35.3Ma Chesapeake Bay impact structure (85km diameter) was drilled during 2005/2006 in an ICDP-USGS drilling project. The Eyreville drill cores include polymict impact breccias and associated rocks (1397-1551m depth). Tens of melt particles from these impactites were studied by optical and electron microscopy, electron microprobe, and microRaman spectroscopy, and classified into six groups: m1-clear or brownish melt, m2-brownish melt altered to phyllosilicates, m3-colorless silica melt, m4-melt with pyroxene and plagioclase crystallites, m5-dark brown melt, and m6-melt with globular texture. These melt types have partly overlapping major element abundances, and large compositional variations due to the presence of schlieren, poorly mixed melt phases, partly digested clasts, and variable crystallization and alteration. The different melt types also vary in their abundance with depth in the drill core. Based on the chemical data, mixing calculations were performed to determine possible precursors of these melt particles. The calculations suggest that most melt types formed mainly from the thick sedimentary section of the target sequence (mainly the Potomac Formation), but an additional crystalline basement (schist/gneiss) precursor is likely for the most abundant melt types m2 and m5. Sedimentary rocks with compositions similar to those of the melt particles are present among the Eyreville core samples. Therefore, sedimentary target rocks were the main precursor of the Eyreville melt particles. However, the composition of the melt particles is not only the result of the precursor composition but also the result of changes during melting and solidification, as well as postimpact alteration, which must also be considered. The variability of the melt particle compositions reflects the variety of target rocks and indicates that there was no uniform melt source. Original heterogeneities, resulting from melting of different target rocks, may be preserved in impactites of some large impact structures that formed in volatile-rich targets, because no large melt body exists, in which homogenization would have taken place. © The Meteoritical Society, 2011. 2011 10.1111/j.1945-5100.2011.01162.x Meteoritics and Planetary Science 46 396-430 Department of Lithospheric Research, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria; Museum für Naturkunde, Leibniz-Institute at Humboldt University Berlin, Invalidenstrasse 43, 10115 Berlin, Germany; Natural History Museum, Burgring 7, A-1010 Vienna, Austria; Institute of Mineralogy and Crystallography, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria 3 https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952727590&doi=10.1111%2fj.1945-5100.2011.01162.x&partnerID=40&md5=ae9a6c7aed42d58457019f9684b35feb cited By 3 K. Bartosova L. Hecht C. Koeberl E. Libowitzky W.U. Reimold article Meyer20112312 The transport mechanism of suevite particles during impact cratering is poorly understood and was studied at the 15 Ma Ries crater in southern Germany. Two emplacement modes of suevite deposits are generally discussed: (1) fallback of plume material into the crater and its periphery upon collapse of an ejecta plume; and (2) horizontal transport of ejected material, akin to emplacement of pyroclastic deposits erupting from volcanic centers. In order to differentiate between the two emplacement modes of suevite deposition, we analyzed the shape fabrics of suevite components from two localities outside the Ries crater by fitting shape-fabric ellipsoids to measured shape-fabric ellipses and by applying high-resolution, X-ray- computed tomography to analyze the threedimensional shape and orientation of the suevite particles. We show that the preferred orientation of long axes of elongate particles is disposed either radially or concentrically with respect to the crater center. Our observations indicate that suevite material was not only derived from an ejecta plume, but was transported by lateral flow under viscous conditions upon fallback. This flow regime resembles that known from pyroclastic flows. © 2011 Geological Society of America. 2011 10.1130/B30393.1 Bulletin of the Geological Society of America 123 2312-2319 Museum of Natural History Berlin, Leibniz Institute at the Humboldt University Berlin, Invalidenstrasse 43, 10115 Berlin, Germany; Université du Québec à Montréal, Département des Sciences de la Terre et de l'Atmosphère, CP 8888, Centre-Ville, Montréal, QC H4A 1N4, Canada; McMaster University Hamilton, School of Geography and Earth Sciences and Origins Institute, 1280 Main Street West, Hamilton, ON L8S 4K1, Canada 11-12 https://www.scopus.com/inward/record.uri?eid=2-s2.0-80055097141&doi=10.1130%2fB30393.1&partnerID=40&md5=04f3f34f53eab5788530a98b8628b71a cited By 20 C. Meyer M. Jébrak D. Stöffler U. Riller article Velasco-Villareal2011154 Results of a paleomagnetic study of 89 samples from impact breccias from the Chicxulub crater are presented and used to investigate on ejecta emplacement, hydrothermal and alteration processes. The impactite sequence sampled in cores from Yaxcopoil-1 borehole is ∼100. m thick and formed by six subunits characterized by petrographic, scan images, geochemical and textural analyses, which point to different emplacement modes. Impact occurred within reverse polarity chron C29r; therefore, magnetization acquired at crater formation and shortly thereafter will present reverse polarity, which is supported by paleomagnetic measurements on melt samples from Yucatan-6 borehole. Results after step-wise thermal and alternating field demagnetization document a pattern of 23 upward and 29 downward inclinations at Yaxcopoil-1 around -33° and 38°, respectively. Measurements of magnetic hysteresis and variation of low-field susceptibility with temperature suggest low-Ti titanomagnetites and magnetite as main magnetic carriers. Petrographic observations indicate the presence of fine-grained magnetite, hematite and Fe-oxyhydroxides, related to hydrothermal alteration processes. Curie points are in the range of 520-580 °C. The wide range of unblocking temperature spectra points to variable grain sizes of a magnetic phase that unblocks around 580 °C. Hysteresis ratio plots indicate most samples fall in the pseudo-single domain field. In some samples, wasp-waist constrained hysteresis loops suggest magnetite and hematite. Analyses of vector plots and coercivity and unblocking temperature spectra do not show apparent differences within and between subunits. Subunits are characterized by distinct textural and compositional differences in size, type and relative abundance of clasts and melt-rich or carbonate-rich matrix types. Bulk properties vary with composition and clast contents, particularly within the Middle Suevite and Brecciated Melt Rock subunits that show higher values, while low values characterize the Lower Suevite carbonate-rich with rare basement clasts subunit. Magnetization acquisition mechanisms are discussed, with reference to impactite characteristics, and may relate to remagnetization from hydrothermal and post-impact alteration processes. © 2011 Elsevier B.V. 2011 10.1016/j.pepi.2011.04.003 Physics of the Earth and Planetary Interiors 186 154-171 Proyecto Universitario de Perforaciones en Océanos y Continentes, Instituto de Geofísica, Universidad Nacional Autónoma de México, Coyoacan, 04510 México D.F., Mexico; Unidad de Ciencias del Agua, Centro de Investigación Científica de Yucatán (CICY), Mérida, Yucatán, Mexico 3-4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-79957847736&doi=10.1016%2fj.pepi.2011.04.003&partnerID=40&md5=773af3c3404c6acc798787e3cf95f919 cited By 9 M. Velasco-Villareal J. Urrutia-Fucugauchi M. Rebolledo-Vieyra L. Pérez-Cruz article Bartosova20101021 The ICDP-USGS Eyreville drill cores in the Chesapeake Bay impact structure reached a total depth of 1766 m and comprise (from the bottom upwards) basement-derived schists and granites/pegmatites, impact breccias, mostly poorly lithified gravelly sand and crystalline blocks, a granitic slab, sedimentary breccias, and postimpact sediments. The gravelly sand and crystalline block section forms an approximately 26 m thick interval that includes an amphibolite block and boulders of cataclastic gneiss and suevite. Three gravelly sands (basal, middle, and upper) are distinguished within this interval. The gravelly sands are poorly sorted, clast supported, and generally massive, but crude size-sorting and subtle, discontinuous layers occur locally. Quartz and K-feldspar are the main sand-size minerals and smectite and kaolinite are the principal clay minerals. Other mineral grains occur only in accessory amounts and lithic clasts are sparse (only a few vol%). The gravelly sands are silica rich (∼80 wt% SiO2). Trends with depth include a slight decrease in SiO2 and slight increase in Fe2O3. The basal gravelly sand (below the cataclasite boulder) has a lower SiO2 content, less K-feldspar, and more mica than the higher sands, and it contains more lithic clasts and melt particles that are probably reworked from the underlying suevite. The middle gravelly sand (below the amphibolite block) is finer-grained, contains more abundant clay minerals, and displays more variable chemical compositions than upper gravelly sand (above the block). Our mineralogical and geochemical results suggest that the gravelly sands are avalanche deposits derived probably from the nonmarine Potomac Formation in the lower part of the target sediment layer, in contrast to polymict diamictons higher in the core that have been interpreted as ocean-resurge debris flows, which is in agreement with previous interpretations. The mineralogy and geochemistry of the gravelly sands are typical for a passive continental margin source. There is no discernible mixing with marine sediments (no glauconite or Paleogene marine microfossils noted) during the impact remobilization and redeposition. The unshocked amphibolite block and cataclasite boulder might have originated from the outer parts of the transient crater. © 2010 The Meteoritical Society. 2010 10.1111/j.1945-5100.2010.01077.x Meteoritics and Planetary Science 45 1021-1052 Department of Lithospheric Research, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria; Department of Geodynamics and Sedimentology, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria; U.S. Geological Survey, 926A National Center, Reston, VA 20192, United States; Department of Geosciences, University of Oslo, P.O. Box 1047, Blindern, NO-0316 Oslo, Norway; Natural History Museum, Burgring 7, A-1010 Vienna, Austria 6 https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957318316&doi=10.1111%2fj.1945-5100.2010.01077.x&partnerID=40&md5=dea78112779d625894bc2c5dbdee4439 cited By 1 K. Bartosova S. Gier J.W. Horton Jr. C. Koeberl D. Mader H. Dypvik article French2010123 In the geological sciences it has only recently been recognized how important the process of impact cratering is on a planetary scale, where it is commonly the most important surface-modifying process. On the Moon and other planetary bodies that lack an appreciable atmosphere, meteorite impact craters are well preserved, and they can commonly be recognized from morphological characteristics, but on Earth complications arise as a consequence of the weathering, obliteration, deformation, or burial of impact craters and the projectiles that formed them. These problems made it necessary to develop diagnostic criteria for the identification and confirmation of impact structures on Earth. Diagnostic evidence for impact events is often present in the target rocks that were affected by the impact. The conditions of impact produce an unusual group of melted, shocked, and brecciated rocks, some of which fill the resulting crater, and others which are transported, in some cases to considerable distances from the source crater. Only the presence of diagnostic shock-metamorphic effects and, in some cases, the discovery of meteorites, or traces thereof, is generally accepted as unambiguous evidence for an impact origin. Shock deformation can be expressed in macroscopic form (shatter cones) or in microscopic forms (e.g., distinctive planar deformation features [PDFs] in quartz). In nature, shock-metamorphic effects are uniquely characteristic of shock levels associated with hypervelocity impact. The same two criteria (shock-metamorphic effects or traces of the impacting meteorite) apply to distal impact ejecta layers, and their presence confirms that materials found in such layers originated in an impact event at a possibly still unknown location. As of 2009 about 175 impact structures have been identified on Earth based on these criteria. A wide variety of shock-metamorphic effects has been identified, with the best diagnostic indicators for shock metamorphism being features that can be studied easily by using the polarizing microscope. These include specific planar microdeformation features (planar fractures [PFs], PDFs), isotropization (e.g., formation of diaplectic glasses), and phase changes (high pressure phases; melting). The present review provides a detailed discussion of shock effects and geochemical tracers that can be used for the unambiguous identification of impact structures, as well as an overview of doubtful criteria or ambiguous lines of evidence that have erroneously been applied in the past. © 2009 Elsevier B.V. All rights reserved. 2010 10.1016/j.earscirev.2009.10.009 Earth-Science Reviews 98 123-170 Department of Paleobiology, Smithsonian Institution, PO Box 37012, Washington, DC 20013-7012, United States; Department of Lithospheric Research, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria 1-2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-75449090246&doi=10.1016%2fj.earscirev.2009.10.009&partnerID=40&md5=966d6b872a555d79d536dcb18f91cc95 cited By 369 B.M. French C. Koeberl article Lambert2010509 The 200 Ma, 24-km-diameter Rochechouart impact structure was formed in granitic intrusive and metamorphic rocks of Variscan age (400-300 Ma) close to the margin of the Mesozoic sea. Fractured basement and autochthonous breccias form a several-decameter-thick semicontinuous zone over an 18-20-km-diameter zone. Impact melt rocks, suevite, and polymict lithic breccia are spread over an ∼15 km inner zone, forming a centro-symmetric deposit inclined 0.6°N. No topographic expression of the central uplift exists. The crater floor is at the same elevation (∼±50 m) over a zone at least 20 km in diameter, corresponding to the central part of the original crater. The pre-erosional diameter of the crater is probably larger than previously thought and possibly reached 40-50 km. The structure appears much less eroded than previously thought, as the sequence of crater fill is complete as exposed near Chassenon. The suevite in Chassenon is capped by an ash-like horizontal deposit of very glass-poor, fine-grained, lithic debris derived from basement rocks. Material with similar grain size and composition is observed in centimeter-to meter-thick multilayered glassbearing intercalations (dikes) cutting through the suevite. The integrity of the Chassenon sequence strikingly contrasts with the age and morphology of the structure, implying that a rapid and thick sedimentary deposit has covered the crater to protect it from erosion. The impactoclastic top deposit also firmly constrains the thickness and volume of the initial crater fill, which appear extremely depleted (by a factor of 5 or more) compared with similar-sized impact structures and model-based calculations. This anomaly remains unexplained. All the impactites, including the glass-poor and glass-free impactites, are characterized by a prominent K-metasomatism signifying pronounced postimpact hydrothermal activity. Exposed in isolated occurrences from the center to the periphery of the inner 15-km-diameter zone, impact melt rocks are extremely unlikely to have formed a continuous sheet. They display a large variety of textures, grading from pure melt rock into basal suevite, which are distinct in composition, texture, and setting from the main suevite body forming the top of the impact deposit. Heterogeneity and relative inefficiency in mixing are characteristic of the whole impact deposit, resulting in heterogeneous melts at the scale of hand specimens, but also at the kilometer scale, as suggested by close ties between the composition of melt-bearing rocks and the subjacent target rocks.. © 2010 The Geological Society of America. All rights reserved. 2010 10.1130/2010.2465(25) Special Paper of the Geological Society of America 465 509-541 Sciences et Applications, Le Lafayette, avenue Kennedy, 33700 Bordeaux-Mérignac, France https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650943083&doi=10.1130%2f2010.2465%2825%29&partnerID=40&md5=be0f14b7ad518b68a1f210d1e099ceff cited By 21 P. Lambert article Goderis2010395 Fifteen impactites from various intervals within the Eyreville cores of the Chesapeake Bay impact structure were sampled to measure siderophile element concentrations. The sampled intervals include basement-derived rocks with veins, polymict impact breccias and associated rocks, and crater-fill sediments. The platinum group element (PGE) concentrations obtained are generally low (e.g., iridium concentrations less than 0.1 ng/g) and are fractionated relative to chondrites. There is no clear distinction in concentration between the different impactite units. So far in the Chesapeake Bay material, only the impact melt rocks from the 823-m-deep Cape Charles test hole, drilled over the central uplift of the structure, have generated a bulk chondritic signature of 0.01-0.1 wt% meteoritic contribution based on a mixing model of 187 Os/ 188 Os isotopic ratios and Os concentrations. However, none of the samples studied shows PGE abundances that enable identification of the type of projectile responsible for the formation of the structure. Hence, it is at present not possible to link the Chesapeake Bay impact to the proposed ordinary chondrite falls by projectiles recorded for other late Eocene craters, namely the 100-km-diameter Popigai impact structure in Siberia and 7.5-km-diameter Wanapitei structure in Canada. The absence of a clear projectile signature hinders further discussions on the existence and the nature of the late Eocene shower event (asteroid versus comet). © 2010 The Geological Society of America. All rights reserved. 2010 10.1130/2010.2465(20) Special Paper of the Geological Society of America 465 395-409 Earth System Science, Vrije Universiteit Brussel, Pleinlaan 2, BE-1050 Brussels, Belgium; Department of Analytical Chemistry, Universiteit Gent, Krijgslaan 281-S12, BE-9000 Ghent, Belgium; Department of Geology, Katholieke Universiteit Leuven, Celestijnenlaan 200E, BE-3001 Heverlee, Belgium https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650937770&doi=10.1130%2f2010.2465%2820%29&partnerID=40&md5=2f27c59a6b7c2e5b1ab814394c3a679c cited By 10 S. Goderis J. Hertogen F. Vanhaecke Ph. Claeys article Barton2010103 Chicxulub is the only known impact structure on Earth with a fully preserved peak ring, and it forms an important natural laboratory for the study of large impact structures and understanding of large-scale cratering on Earth and other planets. Seismic data collected in 1996 and 2005 reveal detailed images of the uppermost crater in the central basin at Chicxulub. Seismic reflection profiles show a reflective layer ∼1 km beneath the apparent crater floor, topped by upwardly concave reflectors interpreted as saucer-shaped sills. The upper part of this reflective layer is coincident with a thin high-velocity layer identified by analyzing refractions on the 6 km seismic streamer data. The high-velocity layer is almost horizontal and appears to be contained within the peak ring structure. We argue that this reflective layer is the predicted coherent melt sheet formed during impact, and it may be comparable with the unit known as the Sudbury Igneous Complex at the Sudbury impact structure. The Sudbury Igneous Complex, interpreted as a differentiated impact melt sheet, appears to have a similar scale and geometry, and an uppermost lithological sequence consisting of a high velocity layer at the top and a velocity inversion beneath. This comparison suggests that the Chicxulub impact structure also contains a coherent differentiated melt sheet. © 2010 The Geological Society of America. All rights reserved. 2010 10.1130/2010.2465(07) Special Paper of the Geological Society of America 465 103-113 Bullard Laboratories, University of Cambridge, Madingley Road, Cambridge CB3 OEZ, United Kingdom; Geological Survey of Canada, 601 Booth Street, Ottawa, ON K1A 0Y3, Canada; Department of Earth Science and Engineering, South Kensington Campus, Imperial College, London, London SW7 2AZ, United Kingdom; Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78758, United States; Surendra-Shell International, Hague, Netherlands; Vermeesch-National Oceanography Centre, University of Southampton, European Way, Southampton SO14 3ZH, United Kingdom https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650951364&doi=10.1130%2f2010.2465%2807%29&partnerID=40&md5=d917cf3dca0845007069930b52695c97 cited By 20 P.J. Barton R.A.F. Grieve J.V. Morgan A.T. Surendra P.M. Vermeesch G.L. Christeson S.P.S. Gulick M.R. Warner article Schulte20101214 The Cretaceous-Paleogene boundary ∼65.5 million years ago marks one of the three largest mass extinctions in the past 500 million years. The extinction event coincided with a large asteroid impact at Chicxulub, Mexico, and occurred within the time of Deccan flood basalt volcanism in India. Here, we synthesize records of the global stratigraphy across this boundary to assess the proposed causes of the mass extinction. Notably, a single ejecta-rich deposit compositionally linked to the Chicxulub impact is globally distributed at the Cretaceous-Paleogene boundary. The temporal match between the ejecta layer and the onset of the extinctions and the agreement of ecological patterns in the fossil record with modeled environmental perturbations (for example, darkness and cooling) lead us to conclude that the Chicxulub impact triggered the mass extinction. 2010 10.1126/science.1177265 Science 327 1214-1218 GeoZentrum Nordbayern, Universität Erlangen-Nürnberg, Schlossgarten 5, D-91054 Erlangen, Germany; Departamento de Ciencias de la Tierra, Instituto Universitario de Investigación de Ciencias Ambientales de Aragón, Universidad de Zaragoza, Pedro Cerbuna 12, E-50009 Zaragoza, Spain; Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EO, United Kingdom; Department of Earth Sciences, University College London, Gower Street, London WC1E 6BT, United Kingdom; Department of Geosciences, Pennsylvania State University, University Park, PA 16802, United States; Institute for Geophysics, University of Texas at Austin, J. J. Pickle Research Campus, 10100 Burnet Road 196-ROC, Austin, TX 78759, United States; Earth System Science, Vrije Universiteit Brussel, Pleinlaan 2, B1050 Brussels, Belgium; Centre for Earth, Planetary, Space and Astronomical Research, Open University, Milton Keynes MK7 6AA, United Kingdom; Earth Science and Engineering, Imperial College London, London SW7 2BP, United Kingdom; Institut für Planetologie, Universität Münster, D-48149 Münster, Germany; Department of Lithospheric Research, University of Vienna, Althanstrasse 14, A1090 Vienna, Austria; Tsunami Engineering Laboratory, Graduate School of Engineering, Tohoku University, 6-6-11-1106 Aoba, Aramaki, Sendai 980-8579, Japan; Programa de Geología de Exploración y Explotación, Dirección de Investígacìón y Posgrado, Instituto Mexicano Del Petróleo, Eje Lázaro Cárdenas No. 152, C. P. 07730, México City, Mexico; Earth Sciences Sector, Natural Resources Canada, Ottawa, ON K1A OE4, Canada; Research and Collections Division, Denver Museum of Nature and Science, 2001 Colorado Boulevard, Denver, CO 80205, United States; Museum für Naturkunde, Leibniz Institute, Humboldt University Berlin, Invalidenstrasse 43, D-10115 Berlin, Germany; Center for Lunar Science and Exploration, Universities Space Research Association-Lunar, Planetary Institute, 3600 Bay Area Boulevard, Houston, TX 77058-1113, United States; Department of Geological Sciences, University of Missouri, Columbia, MO 65211, United States; Planetary Exploration Research Center, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016, Japan; Earth and Atmospheric Sciences, Purdue University, 550 Stadium Mall Drive, West Lafayette, IN 47907-2051, United States; Osservatorio Geologico di Coldigioco, 62021 Apiro (MC), Italy; Department of Civil Engineering and Geological Sciences, 156 Fitzpatrick Hall, University of Notre Dame, Notre Dame, IN 46556, United States; SIO Geological Collections, 301 Vaughan Hall, Scripps Institution of Oceanography, San Diego, CA 92093-0244, United States; Planetary Science Institute, 1700 East Fort Lowell Road, Tucson, AZ 85719, United States; Department of Geology and Geophysics, School of Ocean and Earth Science and Technology, University of Hawaii, Manoa, Honolulu, HI 96822, United States; Unidad de Ciendas Del Agua, Centro de Investigación Científica de Yucatán, A. C., Calle 8, No. 39, Mz. 29, S.M. 64, Cancún, Quintana Roo, 77500, Mexico; Laboratoire des Sciences du Climat et de l'Environnement, Institut Pierre et Simon Laplace, Université de Versailles Saint Quentin en Yveunes-UMR 1572, Avenue de la Terrasse, F-91198 Gif-surYvette Cedex, France; Bruker Nano GmbH, Schwarzschildstraße 12, D-12489 Berlin, Germany; Department of Earth and Environmental Sciences, K.U.Leuven, Box 2408, Celestijnenlaan 200E, 3001 Leuven, Belgium; Natural Resources Canada, Geological Survey of Canada Calgary, 3303 33rd Street NW, Calgary, AB T2L 2A7, Canada; Laboratorio de Paleomagnetismo y Paleoambientes, Programa Universitario de Perforadones en Oceanos y Continentes, Universidad Nadonal Autónoma de México (UNAM), DF 04510 Mexico, Mexico; Department of Earth and Ecosystem Sciences, Lund University, Sölvegatan 12, 223 62 Lund, Sweden; Department of Geology and Geophysics, University of Alaska, Fairbanks, AK 99775, United States 5970 https://www.scopus.com/inward/record.uri?eid=2-s2.0-77749279680&doi=10.1126%2fscience.1177265&partnerID=40&md5=d4ef063d50386d2b1859b4da5242d3a9 cited By 947 P. Schulte L. Alegret I. Arenillas J.A. Arz P.J. Barton P.R. Bown T.J. Bralower G.L. Christeson P. Claeys C.S. Cockell G.S. Collins A. Deutsch T.J. Goldin K. Goto J.M. Grajales-Nishimura R.A.F. Grieve S.P.S. Gulick K.R. Johnson W. Kiessling C. Koeberl D.A. Kring K.G. MacLeod T. Matsui J. Melosh A. Montanari J.V. Morgan C.R. Neal D.J. Nichols R.D. Norris E. Pierazzo G. Ravizza M. Rebolledo-Vieyra W.U. Reimold E. Robin T. Salge R.P. Speijer A.R. Sweet J. Urrutia-Fucugauchi V. Vajda M.T. Whalen P.S. Willumsen article Kalleson2010798 Melt-bearing impactites dominated by suevite, and with a minor content of clast-rich impact melt rock, are found within the central part of the Gardnos structure. They are preserved as the eroded remnants in the relatively small complex impact structure with a present diameter of 5 km. These rocks have been mapped in the field and in the Branden drill core, and described according to mineralogy/petrology, including matrix, litho clast, and melt content, as well as geochemistry. Based on our extensive field mapping, a simple 3-D model of the original crater was constructed to estimate tentative volumes for the melt-bearing impactites. The variations in lithic and melt fragment content and chemistry of suevite matrix can mostly be explained by incorporation of mafic rocks into a dominant mixture of granitic, gneissic, and quartzitic target rocks, reflecting mixing of material from different parts of the crater. Melt fragments within suevite occur with a variety of shapes and textures, probably related to different original target rock composition, to the various temperatures the individual fragments were subjected to during the impact event and deposition processes. This study discusses the impact-related deposits based on a sedimentological approach. Their overall composition and structures indicate dominating gravity flow processes in the final transportation and deposition of the suevite. © 2010 The Meteoritical Society. 2010 10.1111/j.1945-5100.2010.01055.x Meteoritics and Planetary Science 45 798-827 Department of Geosciences, University of Oslo, P.O. 1047, Blindern, NO-0316 Oslo, Norway; Natural History Museum, University of Oslo, P.O. 172, Blindern, NO-0318 Oslo, Norway 5 https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956573774&doi=10.1111%2fj.1945-5100.2010.01055.x&partnerID=40&md5=25280fe6865b1db7f4df449937105109 cited By 14 E. Kalleson H. Dypvik O. Nilsen article Bahlburg2010170 The crater fill units that were deposited during the terminal stages of the formation of the shallow marine Chicxulub crater in northern Yucatan were interpreted by some authors as products of a catastrophic resurge of water. This interpretation contrasts markedly with the dominant sand grain size &lt;300μm and the abundant small-scale current cross bedding structures indicative of low energy deposition. To solve this discrepancy we applied first principles of physical sedimentology in an analysis of grain size and sedimentary structures to determine current velocities and minimum water depths required to generate the observed sedimentary bedforms. We combine this approach with numerical modeling of crater formation in order to explore the dimensions of the ejecta ring wall being formed by a Chicxulub impactor in water depths of 1000m. We find that the ejecta wall reaches heights in the order of 1200m above sea floor and 200m above sea level. It thus prevented the resurge of water into the crater cavity and consequently also the subsequent formation of a collapse wave. The ring wall significantly retarded the refilling of the crater cavity with seawater, and refilling took place by permeation through and localized erosion of the ring wall. This resulted in low-energy currents with velocities between 1.5 and 0.18ms-1 slowly reentering the crater and depositing the cm-scale, low energy laminated and crossbedded sandy terminal impact deposits. © 2010 Elsevier B.V. 2010 10.1016/j.epsl.2010.03.037 Earth and Planetary Science Letters 295 170-176 Institut für Geologie und Paläontologie, Westfälische Wilhelms-Universität Münster, Corrensstrasse 24, 48149 Münster, Germany; Department of Geology and Geophysics, Texas AandM University, College Station, TX 77843, United States; Museum für Naturkunde, Leibniz Institute at the Humboldt Universität zu Berlin, Invalidenstr. 43, 10115 Berlin, Germany 1-2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953025410&doi=10.1016%2fj.epsl.2010.03.037&partnerID=40&md5=5a452f60f4880f277bdbe72423faac22 cited By 8 H. Bahlburg R. Weiss K. Wünnemann article Gondwe20101 The Yucatan Peninsula is one of the world's largest karstic aquifer systems. It is the sole freshwater source for human users and ecosystems. The region hosts internationally important groundwater-dependent ecosystems (GDEs) in the 5280km2 Sian Ka'an Biosphere Reserve. The GDEs are threatened by increasing groundwater abstractions and risks of pollution. Hydrogeological exploration work is needed as basis for sound groundwater management. A multidisciplinary approach was used to study this data-scarce region. Geochemical data and phreatic surface measurements showed distinct hydrogeological units in the groundwater catchment of Sian Ka'an. The hilly southwestern areas had a low hydraulic permeability, likely caused by a geology containing gypsum, whereas the transition zone and flat areas in the east and north had a high permeability. In the latter areas, the fresh groundwater could be described by a Dupuit-Ghyben-Herzberg lens. Geophysical borehole logging and time-domain electromagnetic soundings identified a shallow, low-resistive and high-gamma-radiation layer present throughout the hilly area and transition zone. Its thickness was 3-8m, apparent conductivity was 200-800mS/m and natural gamma-radiation about 80 counts pr. second. The layer is proposed to be ejecta from the Chicxulub impact (Cretaceous/Paleogene boundary). Spatial estimates of recharge were calculated from MODIS imagery using the 'triangle method'. Average recharge constituted 17% of mean annual precipitation in the study area. Recharge was greatest in the hilly area and towards Valladolid. Near the coast, average actual evapotranspiration exceeded annual precipitation. The multidisciplinary approach used in this study is applicable to other catchment-scale studies. © 2010 Elsevier B.V. 2010 10.1016/j.jhydrol.2010.04.044 Journal of Hydrology 389 1-17 Department of Environmental Engineering, Technical University of Denmark, Miljoevej,Building 113, DK-2800 Kgs. Lyngby, Denmark; Geological Survey of Denmark and Greenland (GEUS), Oester Voldgade 10, DK-1350 Copenhagen, Denmark; Instituto de Geofísica, Universidad Nacinal Autónoma de México, Cd. Universitaria, México DF 04510, Mexico; Centro para el Estudio del Agua, CICY-Quintana Roo, Calle 8, Lote 1, No. 39, Manzana 20 SM 64, Cancún, Quintana Roo 77500, Mexico; Amigos de Sian Ka'an, Calle Fuego No. 2, Manzana 10 SM 4, Cancún, Quintana Roo 77500, Mexico 1-2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954386651&doi=10.1016%2fj.jhydrol.2010.04.044&partnerID=40&md5=64e397cb7dd9ae790c707d3354602289 cited By 72 B.R.N. Gondwe S. Lerer S. Stisen L. Marín M. Rebolledo-Vieyra G. Merediz-Alonso P. Bauer-Gottwein article Ortiz-Alemán2010127 The analytic signal method and forward modeling in three dimensions are applied to magnetic field data over the Chicxulub crater in order to determine and document the main magnetic anomaly sources and crater structure in the central zone. Aeromagnetic data over the structure reveal three strong, well-defined concentric patterns, with a central 40-km diameter zone of high amplitude anomalies. Magnetic anomalies are interpreted to be associated with the melt sheet, upper breccias and central uplift, which present three to four orders of magnitude contrasts with the surrounding carbonate units. The limited number of magnetic property measurements, apparent wide range in the remanent intensity and susceptibility in the upper breccias and possible yet unconstrained zones of hydrothermal systems have restricted our ability to determine the characteristics and distribution of major structural elements of the Chicxulub crater. The amplitude of the analytic signal produces maxima over magnetization contrasts, independent of the direction of magnetization. Interpretation of maxima location and depth distribution is used, in a second stage, as a priori information in the construction of an input prism assemblage magnetic configuration and its properties for three-dimensional forward modeling. Results indicate that magnetic sources extend to a radial distance of ∼45. km from the center of the structure with average depths ranging between 2 and 4. km. The magnetic anomaly sources in the central structural uplift zone are located in the range from 3.5 to 8. km depth, with dominant contributions from an apparent large body forming the basement uplift. © 2010 Elsevier B.V. 2010 10.1016/j.pepi.2010.01.007 Physics of the Earth and Planetary Interiors 179 127-138 Instituto Mexicano del Petroleo, Avenida de los Cien Metros 152, 07730 Mexico, D.F., Mexico; Proyecto Universitario de Perforaciones en Oceanos y Continentes, Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, 04510 Mexico D.F., Mexico 3-4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951090728&doi=10.1016%2fj.pepi.2010.01.007&partnerID=40&md5=25bf81ec76a2f8a5e97566ec741d6a1a cited By 27 C. Ortiz-Aleman J. Urrutia-Fucugauchi article Kikuchi201014 The extinction pattern of the Maastrichtian indicates that long-term and short-term events contributed to the Cretaceous-Tertiary (K-T) mass extinction at 65 Ma. However, it is not clear how the impact events are linked with the extinction selectivity; e.g. non-avian dinosaurs became extinct, whereas birds survived. The post-impact air quality is discussed, and attention is focused on the then land vertebrates. Although ground-level (tropospheric) O3 is a powerful irritant on the order of 0.1 ppm toxicity, the presence of ground-level O3 has hardly been considered since the K-T impact theory was reported about 30 years ago. Under the post-impact conditions reconstructed by simulating the carbon cycle (including isotope balance) and impact chemistry, a trajectory model suggests that the then photochemical reactions formed ground-level O3 whose concentration was apparently low at ∼ 1.0 ppm, but it is much greater than the current level of ∼ 0.04 ppm: that is, an O3 concentration above the health-threatening level persisted on the ground after the K-T impact. All land vertebrates must have suffered from respiratory O3 irritation at the time. However, analysis suggests that variables of O3 characteristics - hourly variation, short half-life in water and decomposition due to catalytic effects in soil - were randomly combined with variables of lifestyle features such as habitat, torpor, etc. to form new variables (i.e. survival rates): a high survival probability for amphibians; middle/high probabilities for semi-aquatic reptiles, mammals and birds; low/middle probabilities for marsupials and terrestrial reptiles; and a zero probability for non-avian dinosaurs. © 2010 Elsevier B.V. All rights reserved. 2010 10.1016/j.palaeo.2010.01.027 Palaeogeography, Palaeoclimatology, Palaeoecology 288 14-23 ESAC - Instituto Politécnico de Coimbra, Bencanta, 3040-316 Coimbra, Portugal; Norwegian Geotechnical Institute, Sognsveien 72, 0806 Oslo, Norway 1-4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-77649234062&doi=10.1016%2fj.palaeo.2010.01.027&partnerID=40&md5=ef6f70131bd8b51ca8028acc9b8b0f54 cited By 6 R. Kikuchi M. Vanneste article Coney2010411 A petrographic and geochemical comparison of suevites from the LB-07A and LB-08A cores recovered during 2004 by the International Continental Scientific Drilling Program with suevites from outside of the crater rim of the Bosumtwi impact structure indicates contrasting mechanisms of formation for these respective impact breccias. The within-crater suevites form only a small part of the lithic impact breccia-dominated impactite crater fill, in contrast to the impactites from outside of the crater, which consist solely of suevite. The clasts of suevites from within the crater display relatively low levels of shock (for most material <45 GPa). The numbers of shocked quartz grains, as well as fragments of diaplectic glass of quartz and feldspar in suevites decrease with depth through the LB-07A core (maximum three sets of planar deformation features [PDFs]). In contrast, the out-of-crater suevites sampled north and south of the crater contain up to four PDF sets in quartz clasts, ballen cristobalite, and higher proportions of diaplectic glass than the within-crater suevites. In addition, the suevites from outside of the crater contain significantly more melt particles (18-37 vol%) than the within-crater suevites (<5 vol%). Melt fragment sizes in suevites from outside the crater are much larger than those from suevites within the crater (maximum 40 cm versus 1 cm). The currently known distribution of impactites outside of the crater would be consistent with a low-angle impact from the east. We propose that the within-crater suevites and polymict lithic breccias were emplaced either via slumping off the crater walls or lateral movement of some melted and much displaced target rock within the crater. Limited admixture of fallback material from the ejecta plume is evident in the uppermost impactite deposit encountered in core LB-05B. In contrast, the out-of-crater suevites formed by fallout from a laterally differentiated ejecta plume, which resulted in different clast populations to the north and south of the crater. © 2010 The Geological Society of America. All rights reserved. 2010 10.1130/2010.2465(21) Special Paper of the Geological Society of America 465 411-442 Impact Cratering Research Group, School of Geosciences, University of the Witwatersrand, Private Bag 3, P.O. WITS, Johannesburg, 2050, South Africa; Museum für Naturkunde, Leibniz-Institute, Humboldt University Berlin, Invalidenstrasse 43, D-10115 Berlin, Germany; Department of Lithospheric Research, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria; Natural History Museum, Burgring 7, 1010 Vienna, Austria https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650939968&doi=10.1130%2f2010.2465%2821%29&partnerID=40&md5=8d22d7c325bc4a147acc229b0b80bd6b cited By 12 L. Coney W.U. Reimold R.L. Gibson C. Koeberl P. Ogilvie article Townsend2009255 The Eyreville B core from the Chesapeake Bay impact structure, Virginia, USA, contains a lower basement-derived section (1551.19 m to 1766.32 m deep) and two megablocks of dominantly (1) amphibolite (1376.38 m to 1389.35 m deep) and (2) granite (1095.74 m to 1371.11 m deep), which are separated by an impactite succession. Metasedimentary rocks (muscovite-quartz-plagioclase-biotite-graphite ± fibrolite ± garnet ± tourmaline ± pyrite ± rutile ± pyrrhotite mica schist, hornblende-plagioclase-epidote-biotite- K-feldspar-quartz-titanite-calcite amphibolite, and vesuvianite-plagioclase- quartz-epidote calc-silicate rock) are dominant in the upper part of the lower basement-derived section, and they are intruded by pegmatitic to coarse-grained granite (K-feldspar-plagioclase-quartz-muscovite ± biotite ± garnet) that increases in volume proportion downward. The granite megablock contains both gneissic and weakly or nonfoliated biotite granite varieties (K-feldspar-quartz-plagioclase-biotite ± muscovite ± pyrite), with small schist xenoliths consisting of biotite-plagioclase-quartz ± epidote ± amphibole. The lower basement-derived section and both megablocks exhibit similar middleto upper-amphibolite-facies metamorphic grades that suggest they might represent parts of a single terrane. However, the mica schists in the lower basement-derived sequence and in the megablock xenoliths show differences in both mineralogy and whole-rock chemistry that suggest a more mafi c source for the xenoliths. Similarly, the mineralogy of the amphibolite in the lower basement-derived section and its association with calc-silicate rock suggest a sedimentary protolith, whereas the bulk-rock and mineral chemistry of the megablock amphibolite indicate an igneous protolith. The lower basement-derived granite also shows bulk chemical and mineralogical differences from the megablock gneissic and biotite granites. © 2009 The Geological Society of America. 2009 10.1130/2009.2458(13) Special Paper of the Geological Society of America 458 255-275 Impact Cratering Research Group, School of Geosciences, University of the Witwatersrand, P.O. WITS, Johannesburg 2050, South Africa; U.S. Geological Survey, 926A National Center, Reston, VA 20192, United States; Museum für Naturkunde-Leibniz Institute, Humboldt University Berlin, Invalidenstrasse 43, 10115 Berlin, Germany; Department of Geological Sciences, University of Vienna, Althanstrasse 14, Vienna A-1090, Austria https://www.scopus.com/inward/record.uri?eid=2-s2.0-74949135099&doi=10.1130%2f2009.2458%2813%29&partnerID=40&md5=1c0a2e477486c4610058a2cc1a6ec85c cited By 18 G.N. Townsend R.L. Gibson J.W. Horton Jr. W.U. Reimold R.T. Schmitt K. Bartosova article Šafanda20099 Geothermal research of the Chicxulub impact structure on the Yucatan Peninsula, Mexico, included repeated temperature logs following 0.3-0.8, 15, 24, 34 and 50 months after shut-in of drilling operations at the 1.5 km deep Yaxcopoil-1 borehole. A gradual distortion of the linear temperature profile by a cold wave propagating downward from 145 m to 317 m was detected within the observational period of 49 months (March 2002-April 2006). The amplitude of the cold wave was increasing with depth and time in the range of 0.8-1.6 °C. As an explanation of this unusual phenomenon, the hypothesis of downward migration of a large volume of drilling mud, reported lost during drilling within the overlying and cooler highly porous and permeable karstic rocks, has been proposed. The thermal effects of the migrating fluid have been evaluated by solving numerically the heat conduction-convection equation in appropriate geothermal models. The best coincidence between the observed data and the simulations was yielded by the model of the drilling mud migrating as a large body. Parameters of this model are constrained by the measured temperature logs relatively tightly: (i) the vertical extent of the downward migrating fluid body is about 5-10 m, possibly increasing within the observational period of 49 months by a factor of 2; (ii) the horizontal extent of the body must be at least 15-20 m, i.e. by order(s) of magnitude larger than the diameter of the borehole; (iii) the average speed of the migration is about 5 metres per month and (iv) the fluid must migrate through a highly porous rock (80% porosity or more). This high porosity, which is necessary for the model to fit the observed data, and the observed relatively stable velocity of the migration indicate the existence of a well-developed system of interconnected cavities down to more than 300 m about 150 m more than the deepest cave system known in Yucatan yet. © 2009 Elsevier B.V. All rights reserved. 2009 10.1016/j.jhydrol.2009.03.023 Journal of Hydrology 372 9-16 Institute of Geophysics, Boční II/1401, 141 31 Praha, Czech Republic; Geophysical Institute, University of Karlsruhe, Hertzstrasse 16, 76187 Karlsruhe, Germany 1-4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-65649099795&doi=10.1016%2fj.jhydrol.2009.03.023&partnerID=40&md5=205f7cf6e7f24ef232585d170ac84f2e cited By 3 J. Šafanda H. Wilhelm P. Heidinger V. Čermák article Christeson2009249 The surface expression of impact craters is well-known from visual images of the Moon, Venus, and other planets and planetary bodies, but constraints on deep structure of these craters is largely limited to interpretations of gravity data. Although the gravity models are non-unique, they do suggest that large impact craters are associated with structure at the base of the crust. We use seismic data to map Moho (crust-mantle interface) topography beneath the Chicxulub crater, the youngest and best preserved of the three largest known terrestrial impact craters. The Moho is upwarped by ~ 1.5-2 km near the center of the Chicxulub crater, and depressed by ~ 0.5-1.0 km at a distance of ~ 30-55 km from the crater center. A comparison with numerical modeling results reveal that immediately following impact a transient crater reached a maximum depth of at least 30 km prior to collapse, and that subsequent collapse of the transient crater uplifted target material from deep below the crater floor. These results demonstrate that deformation from large terrestrial impacts can extend to the base of the continental crust. A similar Moho topography is also modeled for some large lunar and Martian craters, which suggests that mantle deformation may play a prominent role in large crater formation. © 2009 Elsevier B.V. All rights reserved. 2009 10.1016/j.epsl.2009.04.033 Earth and Planetary Science Letters 284 249-257 University of Texas, Institute for Geophysics, Jackson School of Geosciences, 10100 Burnet Rd, Austin, TX 78758, United States; Department of Earth Science and Engineering, Imperial College, South Kensington Campus, London, SW7 2AZ, United Kingdom; Bullard Laboratories, Department of Earth Sciences, University of Cambridge, Cambridge, CB2 3EQ, United Kingdom 1-2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-67549146397&doi=10.1016%2fj.epsl.2009.04.033&partnerID=40&md5=12301d7d8c30da682b2d7ac3ed748a43 cited By 28 G.L. Christeson G.S. Collins J.V. Morgan S.P.S. Gulick P.J. Barton M.R. Warner article Artemieva2009768 In this paper we investigate the formation of the Cretaceous-Paleogene (K-Pg) boundary layer through numerical modeling. The K-Pg layer is widely agreed to be composed of meteoritic material and target rock from the Chicxulub impact site, that has been ejected around the globe and mixed with local material during final deposition. The observed composition and thickness of the K-Pg boundary layer changes with azimuth and distance from the impact site. We have run a suite of numerical simulations to investigate whether we can replicate the observational data, with a focus on the distal K-Pg layer and the impact glasses at proximal sites such as Beloc, Haiti. Previous models of the K-Pg ejecta have assumed an initial velocity distribution and tracked the ejecta to its final destination. Here, we attempt to model the entire process, from impact to the arrival of the ejecta around the globe. Our models replicate the observed ejecta thickness at proximal sites, and the modeled ejecta is composed of sediments and silicate basement rocks, in agreement with observational data. Models that use a 45° impact angle are able to replicate the total ejecta and iridium volume at distal sites, and the majority of the ejecta is composed of meteorite and target sediments. Sub-vertical impacts generate too little iridium, and oblique impacts of ≤30 degrees generate too much. However, in contrast to observations, models that involve ballistic transport of ejecta lead to ejecta thickness decreasing with increasing distance, and are unable to transport shocked minerals (quartz and zircon) from the Chicxulub basement rocks around the globe. We suggest that much of the K-Pg ejecta is transported non-ballistically, and that the most plausible mechanism is through re-distribution from a hot, expanding atmosphere. The results are important for future investigations of the environmental effects of the Chicxulub impact. © 2009 Elsevier Inc. All rights reserved. 2009 10.1016/j.icarus.2009.01.021 Icarus 201 768-780 Planetary Science Institute, 1700 E. Ft. Lowell, suite 106, Tucson, AZ 85719, United States; Institute for Dynamics of Geospheres, Leninsky pr., 38, Moscow, 119334, Russian Federation; Earth Science and Engineering, Imperial College London, South Kensington Campus, SW7 2AZ London, United Kingdom 2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-67349263403&doi=10.1016%2fj.icarus.2009.01.021&partnerID=40&md5=03d561871e5b314d4e6036ec00b6a3f8 cited By 74 N. Artemieva J. Morgan article Poag2009747 The late Eocene Chesapeake Bay bolide impact transformed its offshore target site from an outer neritic, midshelf seafl oor into a bathyal crater basin. To obtain a depositional record from one of the deepest parts of this basin, the U.S. Geological Survey (USGS) and the International Continental Scientifi c Drilling Program (ICDP) drilled a 1.76-km-deep core hole near Eyreville, Virginia. The Eyreville core and eight previously cored boreholes contain a rarely obtainable record of marine deposition and microfossil assemblages that characterize the transition from synimpact to postimpact paleoenvironments inside and near a submarine impact crater. I used depositional style and benthic foraminiferal assemblages to recognize a four-step transitional succession, with emphasis on the Eyreville core. Step 1 is represented by small-scale, silt-rich turbidites, devoid of indigenous microfossils, which lie directly above the crater-fi lling Exmore breccia. Step 2 is represented by very thin, parallel, silt and clay laminae, which accumulated on a relatively tranquil and stagnant seafl oor. This stagnation created a dead zone, which excluded seafl oor biota, and it lasted ~3-5 ka. Step 3 is an interval of marine clay deposition, accompanied by a burst of microfaunal activity, as a species-rich pioneer community of benthic foraminifera repopulated the impact site. The presence of a diagnostic suite of agglutinated foraminifera during step 3 indicates that paleoenvironmental stress related to the impact lasted from ~9 ka to 400 ka at different locations inside the crater. During step 4, the agglutinated assemblage disappeared, and an equilibrium foraminiferal community developed that contained nearly 100% calcareous species. In contrast to intracrater localities, core sites outside and near the crater rim show neither evidence of the agglutinated assemblage, nor other indications of long-term biotic disruption from the bolide impact. © 2009 The Geological Society of America. 2009 10.1130/2009.2458(32) Special Paper of the Geological Society of America 458 747-773 U.S. Geological Survey, 384 Woods Hole Road, Woods Hole, MA 02543-1598, United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-74949120031&doi=10.1130%2f2009.2458%2832%29&partnerID=40&md5=0791f092ca8f00cfdb1c1b54ddd82c0e cited By 7 C.W. Poag article McDonald2009469 This paper documents an attempt to detect a meteoritic component in both washback (resurge) crater-fill breccia (the so-called Exmore breccia) and in suevites from the Eyreville core hole, which was drilled several kilometers from the center of the 85-km-diameter Chesapeake Bay impact structure, Virginia, USA. Determining the presence of an extraterrestrial component and, in particular, the projectile type for this structure, which is the largest impact structure currently known in the United States, is of importance because it marks one of several large impact events in the late Eocene, during which time the presence of extraterrestrial 3He and multiple impact ejecta layers provide evidence for a comet or asteroid shower. Previous work has indicated an ordinary chondritic projectile for the largest of the late Eocene craters, the Popigai impact structure in Siberia. The exact relation between the Chesapeake Bay impact event and siderophile element anomalies documented in late Eocene ejecta layers from around the world is not clear. The only clear indication for an extraterrestrial component related to this structure has been the discovery of a meteoritic osmium isotopic signature in impact melt rocks recovered from a hydrogeologic test hole located on Cape Charles near the center of the structure, and confirmation of a similar signature in suevitic rocks would have been desirable in order to place constraints on the type of projectile involved in formation of the Chesapeake Bay crater. Unfortunately, the current data show no discernible differences in the contents of the platinum group elements (PGEs) among the suevite, the Exmore breccia, and several crystalline basement rocks, all from the Eyreville core hole. Abundances of PGEs are uniformly low (e.g., <0.1 ppb Ir), and chondrite-normalized abundance patterns are nonchondritic. These data do not allow unambiguous verification of an extraterrestrial signature. Thus, the nature of the Chesapeake Bay projectile remains ambiguous. © 2009 The Geological Society of America. 2009 10.1130/2009.2458(21) Special Paper of the Geological Society of America 458 469-479 School of Earth, Ocean and Planetary Sciences, Cardiff University, Park Place, Cardiff CF10 3YE, United Kingdom; Department of Lithospheric Research, University of Vienna, Althanstrasse 14, Vienna, A-1090, Austria https://www.scopus.com/inward/record.uri?eid=2-s2.0-74949113207&doi=10.1130%2f2009.2458%2821%29&partnerID=40&md5=e7dacf6de41d8b08642e5cbda3f4ac73 cited By 10 I. Mcdonald K. Bartosova C. Koeberl article Wittmann2009377 The Eyreville B drill core in the inner annular moat of the 85-km-diameter Chesapeake Bay impact structure recovered the first coherent impact melt volumes from within the crater as two bodies, 1 and 5.5 m thick. This study focuses on the petrogenesis of these well-preserved rocks. Mixing calculations reveal that the chemical composition of these melts can be modeled as a hybrid of ̃40% sedimentary target and ̃60% crystalline basement component. The melt rocks contain abundant lithic and mineral clasts that display all stages of shock metamorphism. Zircon clasts record the cooling of the melt from temperatures above 1700 °C to below 1200 °C within the first minutes after formation. Glassy melt with a peraluminous, rhyolitic composition that contains ̃5 wt% water is preserved. This melt records a crystallization sequence of aluminum-rich orthopyroxene and hercynitic spinel, followed by plagioclase, titanomagnetite and cordierite, and late sanidine. Spherulitic aluminosilicate-SiO 2 -cordierite aggregates that are comparable to buchites at temperatures below ̃1465 °C complement this assemblage. Lack of hyaloclastic fragmentation suggests dry emplacement conditions. Complete cooling by conductive heat transfer took ̃7 weeks and ̃4 years for the 1-m- and the 5.5-m-thick melt bodies, respectively. Alteration stages below ̃100 °C produced smectite, phillipsite, chalcedony, and a rare zeolite phase that is tentatively identified as terranovaite. © 2009 The Geological Society of America. 2009 10.1130/2009.2458(17) Special Paper of the Geological Society of America 458 377-396 Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, TX 77058, United States; Museum für Naturkunde-Leibniz Institute, Humboldt University Berlin, Invalidenstrasse 43, 10115 Berlin, Germany; Florida Institute of Technology, Melbourne, FL 32901, United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-74949125572&doi=10.1130%2f2009.2458%2817%29&partnerID=40&md5=e7616e231af48a47e2a9002b0853c5b7 cited By 40 A. Wittmann R.T. Schmitt L. Hecht D.A. Kring W.U. Reimold H. Povenmire article Mayr2009137 The physical properties of rocks in drill core from impact structures can be used to distinguish individual nonimpact and impact-generated lithologies, and to investigate the effect of the impact process on the target rocks. Here, we present the results of laboratory measurements of porosity, density, velocity, and thermal properties on the densely sampled cores from the Eyreville borehole in the Chesapeake Bay impact structure, USA. With increasing depth, the lithologies encountered (and porosities) are: postimpact sediments (40%-60%), Exmore breccia and sedimentary blocks (27%-44%), a large megablock of granitoids (<1%), suevite and polymict lithic impact breccia (1%-25%), and schist, granite, and pegmatite of the basementderived section (1%-13%). The low bulk densities and thermal properties of the postimpact sediments show a good correlation with the high porosity values. The physical properties within the Exmore bed sequence overall display relatively small variation but are heterogeneous on the core sample scale. Physical properties along the impact-breccia sequence are highly variable on all scales, and they are interpreted to be controlled by the structural arrangement of particles as well as by the highly variable mineral and clast compositions of the samples. The physical properties of the rocks of the lowermost basement-derived section are also heterogeneous and are interpreted as having been influenced by both lithology and overprinting as a result of the impact process. These results are important for further lithological and petrophysical interpretation and for calibrating future geophysical models of the Chesapeake Bay impact structure. © 2009 The Geological Society of America. 2009 10.1130/2009.2458(07) Special Paper of the Geological Society of America 458 137-163 Fachgebiet Angewandte Geophysik, Technische Universität Berlin, Sekr. ACK 2, Ackerstrasse 71-76, D-13355 Berlin, Germany; Russian State Geological Prospecting University, 23 Miklukho-Maklai Street, Moscow, 117997, Russian Federation; Geophysical Institute, Universität Karlsruhe, Hertzstrasse 16, 76187 Karlsruhe, Germany https://www.scopus.com/inward/record.uri?eid=2-s2.0-74949128569&doi=10.1130%2f2009.2458%2807%29&partnerID=40&md5=be039756fc59ae4363635ea566115c4d cited By 8 S.I. Mayr H. Burkhardt Y. Popov R. Romushkevich D. Miklashevskiy D. Gorobtsov P. Heidinger H. Wilhelm article Larsen2009699 In this study, we extend the knowledge of postimpact alteration processes through an investigation of mineralogy and petrology of 24 samples from the Exmore Formation and sedimentary megablock intervals in the Eyreville borehole within the Chesapeake Bay impact structure and comparisons to similar studies of cored intervals of the Cape Charles borehole. The bulk mineralogical studies reveal quartz, feldspars (microcline and albite), muscovite, smectite-vermiculite clays, and kaolinite with variable quantities of pyrite, zeolites, calcite, and chlorite. X-ray diffraction analysis of the clay (<2 μm) fraction of samples indicates that the clays are dominated by expandable clays with lesser quantities of illite, kaolinite, glauconite, and mixed- layered clays. The expandable clays include smectite, vermiculite, and smectite-vermiculite intergrade varieties; illite interlayering is minimal (generally, <10% illite layers). Thin section and scanning electron microscope petrography in the Exmore breccia show evidence for extensive authigenic expandable clay in the matrix and dispersed pyrite lepispheres and fine calcite rhombs. Grain alteration includes feldspar dissolution and albitization, glauconite recrystallization, and dissolution and expandable-clay replacement of micas. Taken together, the results indicate that low-temperature alteration (maximum temperatures 60-80 °C) is prevalent in the sedimentary clast-rich intervals in the Eyreville cores, and the maximum effects are observed between 600 and 970 m depth. In comparison, the Exmore Formation from the Cape Charles borehole, 8 km to the southwest and overlying the central peak of the inner crater, shows more advanced authigenesis with Fe-rich chlorite, common quartz overgrowths, and mixed-layered illite-smectite clay with as much as 20% interlayered illite. A low-temperature hydrothermal mineral assemblage is documented in suevite and crystalline-clast breccia at depths of 725-820 m in the Cape Charles borehole. The fine-grained clastic target material and contained seawater are argued to have limited initial target melting and initial crater-floor temperatures in the Chesapeake Bay impact structure to an even greater degree than that of other marine craters targeted in consolidated sedimentary substrates. Subsequent hydrothermal circulation was confined to the central uplift and neighboring fractured zones, whereas alteration in the overlying sedimentary breccias involved conductive heat flow, reaction with hypersaline pore fluids, and minor fluid flow into more porous, permeable sedimentary blocks adjacent to the central uplift. © 2009 The Geological Society of America. 2009 10.1130/2009.2458(30) Special Paper of the Geological Society of America 458 699-721 Department of Earth Sciences, University of Memphis, Memphis, TN 38152, United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-74949114717&doi=10.1130%2f2009.2458%2830%29&partnerID=40&md5=84830b590c51f1bd871febf0271f576c cited By 7 D. Larsen E.C. Stephens V.B. Zivkovic article Wittmann2009349 The International Continental Scientific Drilling Program (ICDP)-U.S. Geological Survey (USGS) Eyreville boreholes through the annular moat of the Chesapeake Bay crater recovered polymict impact breccias and associated rocks from the depth range of 1397-1551 m. These rocks record cratering processes before burial beneath resurge deposits. Quantitative analyses of clast sizes, matrix contents, and distribution of impact melt reveal a shock metamorphic gradient in these impactites. The reason for the low estimated quantity of impact melt in the crater (̃10 km3) remains elusive. Possible causes may relate to increased excavation efficiency due to a high ratio of water column and sedimentary target to depth of excavation, an oblique impact, or a buried melt sheet at depth. A plausible petrogenetic scenario consists of a lower blockrich section that slumped from an outer region of the transient cavity into the annular moat ̃1.5 min after impact. This blocky debris was mixed with the remains of the excavation fl ow, which contained a pod of melt entrained in ground-surge debris on top. Subsequently, melt-rich suevites were emplaced that record interaction of the expanding ejecta plume with fallback material related to the evolving central uplift. A clast-rich impact melt rock that likely shed off the central uplift covers these suevites. Incipient collapse of the ejecta plume is recorded in the uppermost subunit, but the arrival of resurge fl ow terminated its continuous deposition ̃6-8 min after impact. Limited thermal annealing allowed preservation of glassy melt and high-pressure polymorphs. Mild hydrothermal overprint in the central crater was likely driven by the structural uplift of ̃100 °C warmer basement rocks. © 2009 The Geological Society of America. 2009 10.1130/2009.2458(16) Special Paper of the Geological Society of America 458 349-376 Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, TX 77058, United States; Museum für Naturkunde-Leibniz Institute, Humboldt University Berlin, Invalidenstrasse 43, 10115 Berlin, Germany https://www.scopus.com/inward/record.uri?eid=2-s2.0-74949108058&doi=10.1130%2f2009.2458%2816%29&partnerID=40&md5=0961170ceac9858e8ce5a69c92465198 cited By 28 A. Wittmann W.U. Reimold R.T. Schmitt L. Hecht T. Kenkmann article Cermak2009131 For better understanding of temperature state in the subsurface, temperature-depth logs can be suitably completed by high-resolution long-run temperature-time monitoring at selected depths. The results of temperature monitoring at three depth levels in borehole Yaxcopoil-1, Chicxulub impact structure, Mexico (April/May 2006) proved that even when a borehole is in "fully" stabilized conditions, temperature may exhibit certain unrest resembling irregular oscillations in the order of hundredths or (in the extreme case) even first tenths of degree. Two novel methods for detection of the weak fingerprints of stable periodic components in long noisy records, namely the RQI (Recurrence Quantification Interval) analysis and the HiCum (Histograms Cumulation) were used to isolate the constituents with tidal periodicities from temperature oscillations measured in borehole Yaxcopoil-1. Both analyses revealed that temperature series contain perceptible tidal component. The field data were correlated with the simulated synthetic tides. The comparison of staked HiCum records for the theoretical gravity tide and monitored temperature shows significant positive linear correlation between both variables. There is a small lag between two signals corresponding to ~ 25 min phase difference. © 2009 Elsevier B.V. All rights reserved. 2009 10.1016/j.epsl.2009.03.009 Earth and Planetary Science Letters 282 131-139 Institute of Geophysics, Academy of Sciences of the Czech Republic, Praha, Czech Republic; Geophys. and Environ. Physics Res. Group, Hung. Acad. Sci., Budapest, Hungary 1-4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-67349136481&doi=10.1016%2fj.epsl.2009.03.009&partnerID=40&md5=bb0c25effce7b98ddbc7992ee86222d9 cited By 2 V. Čermák L. Bodri J. Šafanda book Pirajno20091 Hydrothermal processes on Earth have played an important role in the evolution of our planet. These processes link the lithosphere, hydrosphere and biosphere in continuously evolving dynamic systems. Terrestrial hydrothermal processes have been active since water condensed to form the hydrosphere, most probably from about 4.4 Ga. The circulation of hot aqueous solution (hydrothermal systems) at, and below, the Earth's surface is ultimately driven by magmatic heat. This book presents an in-depth review of hydrothermal proceses and systems that form beneath the oceans and in intracontinental rifts, continental margins and magmatic arcs. The interaction of hydrothermal fluids with rockwalls, the hydrophere and the biophere, together with changes in their composition through time and space, contribute to the formation of a wide range of mineral deposit types and associated wallrock alteration. On Earth, sites of hydrothermal activity support varied ecosystems based on a range of chemotrophic microorganisms both at surface and in the subsurface. This book also provides an overview of hydrothermal systems associated with meteorite impacts and explores the possibility that hydrothermal processes operate on other terrestrial planets, such as Mars, or satellites of the outer planets such as Titan and Europa. Possible analogues of extraterrestrial putative hydrothermal processes pose the intriguing question of whether primitive life, as we know it, may exist or existed in these planetary bodies. © Springer Science+Business Media B.V. 2009, 2010. 2009 10.1007/978-1-4020-8613-7 Hydrothermal Processes and Mineral Systems 1-1250 Geological Survey of Western Australia, 100 Plain St., East Perth, WA 6004, Australia https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890254144&doi=10.1007%2f978-1-4020-8613-7&partnerID=40&md5=6b42fc3ee6d5840860e548573d5ad734 cited By 775 F. Pirajno article Tagle20094891 A set of 11 impact melt rock samples from the Rochechouart impact structure, France and nine impact melt rock samples from Sääksjärvi impact structure, Finland were studied for their major and trace element compositions, including the abundances of the platinum group elements. The main goal of this study was to identify the projectile type(s) responsible for the formation of these two impact structures. The results confirmed previous studies that suggested extraterrestrial contamination in both the Rochechouart and Sääksjärvi impact melt rocks. The projectile types found for Rochechouart and Sääksjärvi are quite similar, and compatible with the composition of non-magmatic iron meteorites (IA and IIIC). This interpretation is based on: identical platinum group element patterns as well as peculiar Ni/Cr, Ni/Ir and Cr/Ir ratios, which can be explained by mixing of the different components of non-magmatic iron meteorites. This result indicates that, besides ordinary chondrites, non-magmatic iron may be among the most common material impacting the Earth, as they also represent the majority of the projectiles for craters smaller that 1.5 km. The abundance of non-magmatic irons as projectiles as well as their composition (olivine, pyroxene and iron) supports the assumption that a fraction of the S-type asteroids could by related to this type of material. © 2009. 2009 10.1016/j.gca.2009.05.044 Geochimica et Cosmochimica Acta 73 4891-4906 Dept. of Geology, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium; Mineralogy, Natural History Museum, Humboldt-University Berlin, D-10099 Berlin, Germany; GeoForschungsZentrum Potsdam, D-14473 Potsdam, Germany 16 https://www.scopus.com/inward/record.uri?eid=2-s2.0-67650233378&doi=10.1016%2fj.gca.2009.05.044&partnerID=40&md5=cc40dd28e86e76701b9af8d8b1bbed3f cited By 27 R. Tagle R.T. Schmitt J. Erzinger article Claeys2009201 The NASA Deep Impact experiment has important implications to better understand cratering processes on planetary bodies and the production and evolution of ejecta. This man-made impact of a solid Cu body on the nucleus of a comet fills the large gap existing between data derived from small-scale cratering experiments and large-scale field or remote sensing observations of craters. DI thus complements hydrocode modeling of cratering processes. The majority of cratering studies focus on solid silicate-rich targets rather than on porous, poorly consolidated and/or volatile-rich materials. However, volatile targets are common in the Solar System. The lessons learned from the DI collision with comet 9P/Tempel not only clarify the composition and physical properties of the cometary nucleus, but also can shed light on cratering mechanisms and evolution of plume and ejecta. © 2009 Springer-Verlag Berlin Heidelberg. 2009 10.1007/978-3-540-76959-0_26 ESO Astrophysics Symposia 2009 201-211 Dept. of Geology, Vrije Universiteit Brussel, B-1050 Brussels, Belgium https://www.scopus.com/inward/record.uri?eid=2-s2.0-54849413005&doi=10.1007%2f978-3-540-76959-0_26&partnerID=40&md5=cf572ae318d3c3b11861315a895914fe cited By 0 P. Claeys article Barton200914 The processes that accompany asteroid impact and the roles they play in creating or destroying petroleum source rocks, reservoirs and traps are discussed. Most asteroids orbit the Sun in the asteroid belt, which lies between Mars and Jupiter but some come closer to the Earth. Excavation produces a bowl-shaped transient crater. Craters larger than a few kilometers in diameter usually have complex morphologies characterized by an uplift central area. The central high consists of shocked target rock that has been structurally uplifted by rebound. The bottom of the crater filled with melt brecias, mixtures of granite, carbonate, and dolomite in a spherulitic matrix. The impact that has drawn the most attention is the collision of the Chicxulub impactor with what is now the Mexican Yucatán Peninsula. A direct hit by an asteroid can also cause the demise of an hydrocarbon accumulation. 2009 Oilfield Review 21 14-29 True Oil LLC Casper, Wyoming, United States; US Geological Survey, Menlo Park, CA, United States; PEMEX Villahermosa, Tabasco, Mexico; Mexican Petroleum Institute, Mexico City, Mexico; University of Colorado, Boulder, CO, United States; University of Vienna, Vienna, Austria; Continental Resources, Inc., Enid, OK, United States 4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-77950981776&partnerID=40&md5=d2fcda7d025e4e1be37612210d4e25b6 cited By 15 R. Barton K. Bird J.G. Hernández J.M. Grajales-Nishimura G. Murillo-Muñetón B. Herber P. Weimer C. Koeberl M. Neumaier O. Schenk J. Stark article Senft2009471 Impact craters are the most common landform on planetary surfaces; however, the mechanics of the end stages of their formation are not fully understood. The final stage of crater formation involves the collapse of a hemispherical transient cavity. Around small craters, the limited amount of collapse preserves a bowl-shaped cavity. In contrast, the observed shallow depths and complex inner morphologies of large craters require very low shear strength in the collapsing material. Because the observed amount of collapse cannot be reproduced using quasi-static values for the frictional strength of fractured rock, a temporary weakening mechanism is necessary. Here, we investigate the hypothesis that craters collapse along a network of impact-generated faults that weaken during long displacements at high slip velocities via, for example, frictional melting. Using the CTH shock physics code, we simulate the formation of about 100-km diameter impact craters using a simple strain-rate weakening model with parameters constrained by fault friction experiments on crystalline rocks. The model reduces the coefficient of friction from a quasi-static value (0.6-0.85) to a weakened value (0.1-0.2) when a parcel of fractured material exceeds thresholds for cumulative plastic shear strain (a proxy for slip distance) and shear strain rate (a proxy for slip velocity). During crater formation, the strain-rate weakening model leads to strain localizations that are interpreted to be fault zones. Fault zones are spontaneously created and slip over discrete time intervals during collapse. The strain-rate weakening model reproduces the major geologic features observed around the largest terrestrial craters (Vredefort, Sudbury, and Chicxulub), including shallow depths, fault structures, frictional melt distributions, and deep-seated central uplifts. The good agreement between calculations and observations supports the hypothesis that small volumes of transiently weakened material in fault zones control the collapse of large impact craters. © 2009 Elsevier B.V. All rights reserved. 2009 10.1016/j.epsl.2009.08.033 Earth and Planetary Science Letters 287 471-482 Harvard University, United States 3-4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350130551&doi=10.1016%2fj.epsl.2009.08.033&partnerID=40&md5=f11907c03761d7f7a7b196d68e7d0f69 cited By 60 L.E. Senft S.T. Stewart article Perry200927 We report 87Sr/86Sr and ion concentrations of sulfate, chloride, and strontium in the groundwater of the northern and central Yucatan Peninsula, Mexico. Correlation between these data indicates that ejecta from the 65.95 m.y. old Chicxulub impact crater have an important effect on hydrogeology, geomorphology, and soil development of the region. Ejecta are present at relatively shallow subsurface depths in north-central Yucatan and at the surface along the Rio Hondo escarpment in southeast Quintana Roo, where they are referred to as the Albion Formation. Anhydrite/gypsum (and by inference celestite) are common in impact ejecta clasts and in beds and cements of overlying Paleocene and Lower Eocene rocks cored around the margin of the crater. The sulfate-rich minerals that are found in rocks immediately overlying the impact ejecta blanket, may either be partially mobilized from the ejecta layer itself or may have been deposited after the K/T impact event in an extensive pre-Oligocene shallow sea. These deposits form a distinctive sedimentary package that can be easily traced by the Eocene-Cretaceous 87Sr/86Sr signal. A distinct Sr isotopic signature and high SO4/Cl ratios are observed in groundwater of northwestern and north-central Yucatan that interacts with these rocks. Moreover, the distribution of the gypsum-rich stratigraphic unit provides a solution-enhanced subsurface drainage pathway for a broad region characterized by dissolution features (poljes) extending from Chetumal, Quintana Roo to Campeche, Campeche. The presence of gypsum quarries in the area is also consistent with a sulfate-rich stratigraphic "package" that includes ejecta. The distinctive chemistry of groundwater that has been in contact with evaporite/ejecta can be used to trace flow directions and confirms a groundwater divide in the northern Peninsula. Information about groundwater flow directions and about deep subsurface zones of high permeability is useful for groundwater and liquid waste management in the area. Where it discharges at the coast, the unique chemistry of the groundwater that has interacted with the evaporite/ejecta strata may also have significant geomorphologic implications. While groundwater-seawater mixing at the coast has been shown to dissolve and erode limestone, PHREEQC modeling shows that mixing of water nearly saturated in CaSO4 with seawater has a less vigorous dissolution effect due to its high Ca content. © 2009 Elsevier B.V. All rights reserved. 2009 10.1016/j.jhydrol.2008.12.026 Journal of Hydrology 367 27-40 Department of Geology and Environmental Geosciences, Northern Illinois University, Davis Hall 312, DeKalb, IL 60115, United States; Institute of Marine Sciences University of California Santa Cruz, Santa Cruz, CA 95064, United States; Cancun Q.R., Mexico 1-2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-60549095828&doi=10.1016%2fj.jhydrol.2008.12.026&partnerID=40&md5=5d9f6e72c254ec7413ff07fbc30f1d6c cited By 96 E. Perry A. Paytan B. Pedersen G. Velazquez-Oliman article Kenkmann2009571 The combination of petrographic analysis of drill core from the recent International Continental Scientific Drilling Program (ICDP)-U.S Geological Survey (USGS) drilling project and results from numerical simulations provides new constraints for reconstructing the kinematic history and duration of different stages of the Chesapeake Bay impact event. The numerical model, in good qualitative agreement with previous seismic data across the crater, is also roughly consistent with the stratigraphy of the new borehole. From drill core observations and modeling, the following conclusions can be drawn: (1) The lack of a shock metamorphic overprint of cored basement lithologies suggests that the drill core might not have reached the parautochthonous shocked crater floor but merely cored basement blocks that slumped off the rim of the original cavity into the crater during crater modification. (2) The sequence of polymict lithic breccia, suevite, and impact melt rock (1397-1551 m) must have been deposited prior to the arrival of the 950-m-thick resurge and avalanche-delivered beds and blocks within 5-7 min after impact. (3) This short period for transportation and deposition of impactites may suggest that the majority of the impactites of the Eyreville core never left the transient crater and was emplaced by ground surge. This is in accordance with observations of impact breccia fabrics. However, the uppermost part of the suevite section contains a pronounced component of airborne material. (4) Limited amounts of shock-deformed debris and melt fragments also occur throughout the Exmore beds. Shard-enriched intervals in the upper Exmore beds indicate that some material interpreted to be part of the hot ejecta plume was incorporated and dispersed into the upper resurge deposits. This suggests that collapse of the ejecta plume was contemporaneous with the major resurge event(s). Modeling indicates that the resurge flow should have been concluded some 20 min after impact; hence, this also likely marked the end of the major episode of deposition from the ejecta plume. © 2009 The Geological Society of America. 2009 10.1130/2009.2458(25) Special Paper of the Geological Society of America 458 571-585 Museum für Naturkunde-Leibniz Institute, Humboldt University Berlin, Invalidenstrasse 43, 10115 Berlin, Germany; Impact and Astromaterials Research Centre, Department of Earth Science and Engineering, Imperial College London, London, SW7 2AZ, United Kingdom; Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, TX 77058, United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-74949105414&doi=10.1130%2f2009.2458%2825%29&partnerID=40&md5=21bb78a881f3fc2407033566586ddc4d cited By 31 T. Kenkmann G.S. Collins A. Wittmann K. Wünnemann W.U. Reimold H.J. Melosh article Goderis2009145 The goal of this study is to identify the type of projectile responsible for the formation of the late Precambrian Gardnos impact structure in Norway. Fifteen impactite samples, predominantly impact breccias and suevites from the central and northeastern part of the structure, were analyzed for platinum group elements (PGE) and Au using nickel-sulfide fire assay combined with inductively coupled plasma mass spectrometry (ICP-MS). Major and trace elements were measured in the same samples using X-ray fluorescence (XRF). In addition, the concentrations of siderophile elements Ni, Cr, and Co were determined by ICP-MS after acid digestion. The samples collected at the contact between suevite and the sedimentary infill yielded the highest PGE concentrations (Ir = 1.926 ng/g, Ru = 3.494 ng/g, Pt = 4.716 ng/g, Rh = 0.766 ng/g, Pd = 2.842 ng/g for GC6). The CI-normalized PGE patterns are characterized by Ru and Rh enrichments suggesting a non-chondritic impactor. Concentration plots of the different PGE display an excellent correlation (R > 0.99), indicative of a single source for the PGE enrichment. The Ni/Cr ratio of the Gardnos impactor (2.56 ± 0.20) agrees with that of chondrites (2 to 7), whereas Ir is depleted relative to Ni in this projectile (Ni/Ir ratio of 92 000 ± 8000 compared to an average Ni/Ir ratio of 23 150 ± 4250 for chondrites). There is no clear indication of selective post-depositional remobilization of the characteristic highly siderophile elements. The Ni/Ir and Cr/Ir data combined with the non-chondritic PGE ratios probably indicate a differentiated projectile. Based on (1) the similarity of the inter-element ratios of the impactor with the iron phase of non-magmatic iron meteorites and (2) the presence of characteristics of both chondrites and iron meteorites (Ni/Cr and Ni/Ir ratios), an IA or IIIC non-magmatic iron meteorite is a very plausible impactor. © 2008 Elsevier B.V. All rights reserved. 2009 10.1016/j.chemgeo.2008.09.025 Chemical Geology 258 145-156 Department of Geology, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium; Department of Analytical Chemistry, Ghent University, Krijgslaan 281, -S12, B-9000 Ghent, Belgium; Natural History Museum, University of Oslo, N-0316 Oslo, Norway; Department of Geosciences, University of Oslo, N-0316 Oslo, Norway; Department of Mineralogy, Natural History Museum, Berlin, D-10099 Berlin, Germany; GeoForschungsZentrum Potsdam, D-14473 Potsdam, Germany 3-4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-58149234108&doi=10.1016%2fj.chemgeo.2008.09.025&partnerID=40&md5=b9ac2bedec093f5f7912a419c6f27722 cited By 15 S. Goderis E. Kalleson R. Tagle H. Dypvik R.-T. Schmitt J. Erzinger P. Claeys article Vanko2009543 Core samples from the International Continental Scientific Drilling Program (ICDP)-U.S Geological Survey (USGS) Eyreville B core, located in the central crater of the Chesapeake Bay impact structure, were studied to determine the degree to which postimpact hydrothermal activity is recorded in secondary minerals and fluid inclusions. The Chesapeake Bay impact event occurred ̃35 Ma ago on the siliciclastic continental shelf of eastern North America, in up to several hundred meters of water. The combination of hot materials, such as impact melts and suevite breccias, with overlying crater-fill material and seawater is hypothesized to have led to postimpact hydrothermal circulation. Secondary minerals are distinguished from pre-impact minerals by textural features such as the presence or absence of shock metamorphic effects. Minerals in veins and cavities that are shown to have formed after the impact include secondary calcite, chalcedony, phillipsite, clinoptilolite-heulandite, mordenite, and montmorillonite. Some secondary calcite contains liquid-only fluid inclusions with trapping temperatures constrained to be less than or equal to ̃50 °C. Salinities of the inclusion fluids are mostly around 4.3 ± 1 wt% NaCl equivalent, or ̃43 ± 10 g/L total dissolved solids. This salinity is similar to that of the anomalously saline groundwater that currently exists within the crater-fill material, and that could be relict brine that originated just after the impact. © 2009 The Geological Society of America. 2009 10.1130/2009.2458(23) Special Paper of the Geological Society of America 458 543-557 Department of Physics, Astronomy and Geosciences, Towson University, Towson, MD 21252, United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-74949126684&doi=10.1130%2f2009.2458%2823%29&partnerID=40&md5=045dc6251fd625bf66017647f824a6ed cited By 4 D.A. Vanko article Keller200952 Biotic effects of the Chicxulub impact, the K-T event and sea level change upon planktic foraminifera were evaluated in a new core and outcrops along the Brazos River, Texas, about 1000 km from the Chicxulub impact crater on Yucatan, Mexico. Sediment deposition occurred in a middle neritic environment that shallowed to inner neritic depths near the end of the Maastrichtian. The sea level fall scoured submarine channels, which were infilled by a sandstone complex with reworked Chicxulub impact spherules and clasts with spherules near the base. The original Chicxulub impact ejecta layer was discovered 45-60 cm below the sandstone complex, and predates the K-T mass extinction by about 300,000 years. Results show that the Chicxulub impact caused no species extinctions or any other significant biotic effects. The subsequent sea level fall to inner neritic depth resulted in the disappearance of all larger (&gt; 150 μm) deeper dwelling species creating a pseudo-mass extinction and a survivor assemblage of small surface dwellers and low oxygen tolerant taxa. The K-T boundary and mass extinction was identified 40-80 cm above the sandstone complex where all but some heterohelicids, hedbergellids and the disaster opportunistic guembelitrids went extinct, coincident with the evolution of first Danian species and the global δ13C shift. These data reveal that sea level changes profoundly influenced marine assemblages in near shore environments, that the Chicxulub impact and K-T mass extinction are two separate and unrelated events, and that the biotic effects of this impact have been vastly overestimated. © 2008 Elsevier B.V. 2009 10.1016/j.palaeo.2008.09.007 Palaeogeography, Palaeoclimatology, Palaeoecology 271 52-68 Department of Geosciences, Princeton University, Princeton, NJ 08540, United States; Department of Geoloigcal and Environmental Sciences, Ben-Gurion University of the Negev, Beer Sheba, 84105, Israel; Institute for Mineralogy and Geochemistry, University of Karlsruhe, 76128 Karlsruhe, Germany; Geological and Paleontological Institute, Anthropole, CH-1015 Lausanne, Switzerland 1-2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-57849140528&doi=10.1016%2fj.palaeo.2008.09.007&partnerID=40&md5=eb3852c7d70afd1c4355304655fd2af7 cited By 42 G. Keller S. Abramovich Z. Berner T. Adatte article Kawaragi200956 Shock-induced devolatilization in hypervelocity impacts has been considered to play important roles in the atmospheric evolution and mass extinctions in Earth's history. Although the chemical composition of shock-induced gas species from carbonate rocks has been considered as a key to understand the environmental change after the Chicxulub impact, it has not been investigated extensively before. Here, we conduct direct measurements of the chemical composition (CO/CO2) of shock-induced gas species from calcite (CaCO3) using both a laser gun system and an isotopic labeling technique. The CO/CO2 ratio of the shock-induced gas species from calcite is measured to be 2.02 ± 0.41, suggesting that gaseous CO has been dominant in the shock-induced gases in the Chicxulub impact. In order to evaluate the environmental effects of the injection of CO gas, we investigated the post-impact atmospheric chemistry by incorporating our experimental results into a tropospheric photochemical model. The results suggest that an intense (2-5 °C) global warming would have lasted for several years after a Chicxulub-size impact mainly due to the greenhouse effect of tropospheric O3, which is produced via photochemical reactions associated with CO gas. Such an intense global warming could have damaged the biosphere in the mass extinction at the Cretaceous-Paleogene (K-P) boundary. © 2009 Elsevier B.V. All rights reserved. 2009 10.1016/j.epsl.2009.02.037 Earth and Planetary Science Letters 282 56-64 Department of Complexity Science and Engineering, Graduate School of Frontier Sciences, University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba, 277-8561, Japan; Institute of Laser Engineering Osaka University, 2-6 Yamadaoka, Suita, Osaka, 565-0871, Japan; Institute for Study of the Earth's Interior, Okayama University, 827 Yamada, Misasa, Tottori, 682-0193, Japan; Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba, 277-8561, Japan 1-4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-67349202838&doi=10.1016%2fj.epsl.2009.02.037&partnerID=40&md5=d62acb0a5af817d243acf51a9d60a93f cited By 30 K. Kawaragi Y. Sekine T. Kadono S. Sugita S. Ohno K. Ishibashi K. Kurosawa T. Matsui S. Ikeda article HortonJr.2009277 The 1766-m-deep Eyreville B core from the late Eocene Chesapeake Bay impact structure includes, in ascending order, a lower basement-derived section of schist and pegmatitic granite with impact breccia dikes, polymict impact breccias, and cataclas tic gneiss blocks overlain by suevites and clast-rich impact melt rocks, sand with an amphibolite block and lithic boulders, and a 275-m-thick granite slab overlain by crater-fill sediments and postimpact strata. Graphite-rich cataclasite marks a detachment fault atop the lower basement-derived section. Overlying impactites consist mainly of basement-derived clasts and impact melt particles, and coastalplain sediment clasts are underrepresented. Shocked quartz is common, and coesite and reidite are confirmed by Raman spectra. Silicate glasses have textures indicating immiscible melts at quench, and they are partly altered to smectite. Chrome spinel, baddeleyite, and corundum in silicate glass indicate high-temperature crystallization under silica undersaturation. Clast-rich impact melt rocks contain α- cristobalite and monoclinic tridymite. The impactites record an upward transition from slumped ground surge to melt-rich fallback from the ejecta plume. Basement-derived rocks include amphibolite-facies schists, greenschist(?)-facies quartz-feldspar gneiss blocks and subgreenschist-facies shale and siltstone clasts in polymict impact breccias, the amphibolite block, and the granite slab. The granite slab, underlying sand, and amphibolite block represent rock avalanches from inward collapse of unshocked bedrock around the transient crater rim. Gneissic and massive granites in the slab yield U-Pb sensitive high-resolution ion microprobe (SHRIMP) zircon dates of 615 ± 7 Ma and 254 ± 3 Ma, respectively. Postimpact heating was 7lt;~350 °C in the lower basementderived section based on undisturbed 40 Ar/ 39 Ar plateau ages of muscovite and &lt;~150 &lt;C in sand above the suevite based on 40 Ar/ 39 Ar age spectra of detrital microcline. © 2009 The Geological Society of America. 2009 10.1130/2009.2458(14) Special Paper of the Geological Society of America 458 277-316 U.S. Geological Survey, MS 926A, 12201 Sunrise Valley Drive, Reston, VA 20192, United States; U.S. Geological Survey, MS 956, 12201 Sunrise Valley Drive, Reston, VA 20192, United States; U.S. Geological Survey, MS 963, Denver Federal Center, Denver, CO 80225, United States; U.S. Geological Survey, MS 954, 12201 Sunrise Valley Drive, Reston, VA 20192, United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-74949124057&doi=10.1130%2f2009.2458%2814%29&partnerID=40&md5=6074c29ddf5110532968a2d9be35b5f9 cited By 24 J.W. Horton Jr. M.J. Kunk H.E. Belkin J.N. Aleinikoff J.C. Jackson I.-M. Chou article Declercq2009559 The alteration or transformation of impact melt rock to clay minerals, particularly smectite, has been recognized in several impact structures (e.g., Ries, Chicxulub, Mjølnir). We studied the experimental alteration of two natural impact melt rocks from suevite clasts that were recovered from drill cores into the Chesapeake Bay impact structure and two synthetic glasses. These experiments were conducted at hydrothermal temperature (265 °C) in order to reproduce conditions found in meltbearing deposits in the first thousand years after deposition. The experimental results were compared to geochemical modeling (PHREEQC) of the same alteration and to original mineral assemblages in the natural melt rock samples. In the alteration experiments, clay minerals formed on the surfaces of the melt particles and as fine-grained suspended material. Authigenic expanding clay minerals (saponite and Ca-smectite) and vermiculite/chlorite (clinochlore) were identified in addition to analcime. Ferripyrophyllite was formed in three of four experiments. Comparable minerals were predicted in the PHREEQC modeling. A comparison between the phases formed in our experiments and those in the cores suggests that the natural alteration occurred under hydrothermal conditions similar to those reproduced in the experiment. © 2009 The Geological Society of America. 2009 10.1130/2009.2458(24) Special Paper of the Geological Society of America 458 559-569 Department of Geosciences, University of Oslo, P.O. Box 1047, Oslo, NO 316, Norway; Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70803, United States; U.S. Geological Survey, 926A National Center, Reston, VA 20192, United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-74949088037&doi=10.1130%2f2009.2458%2824%29&partnerID=40&md5=ef733bf9762a7e3aad0172fe8b93cf51 cited By 7 J. Declercq H. Dypvik P. Aagaard J. Jahren R.E. Ferrell Jr. J. Wright Horton Jr. article Schmitt2009481 We investigated whole-rock chemical compositions of 318 samples of Exmore breccia (diamicton), impactite (suevite, impact melt rock, polymict lithic impact breccia), and crystalline basement-derived rocks from 444 to 1766 m depth in the International Continental Scientific Drilling Program (ICDP)-U.S. Geological Survey (USGS) Eyreville A and B drill cores (Chesapeake Bay impact structure, Virginia, USA). Here, we compare the average chemical compositions for the Exmore breccia (diamicton), the impactites and their subunits, sandstone, granite, granitic gneiss, and amphibolite of the lithic block section (1095.7-1397.2 m depth), cataclastic gneiss of the impact breccia section, and schist and pegmatite/granite of the basal crystalline section (1551.2-1766.3 m depth). The granite of the megablock (1097.7-1371.1 m depth) is of I-type and is seemingly related to a syncollisional setting. The amphibolite (1377.4-1387.5 m depth) of the lithic block section is of igneous origin and has a tholeiitic character. Based on chemical composition, the Exmore breccia (diamicton) can be subdivided into five units (444.9-450.7, 450.7-468, 468-518, 518-528, and 528-̃865 m depth). The units in the depth intervals of 450.7-468 and 518-528 m are enriched in TiO2, MgO, Sc, V, Cr, and Zn contents compared to the other Exmore breccia units. In some samples, especially at ̃451-455 m depth, the Exmore breccia contains significant amounts of P 2 O 5 . The Exmore breccia is recognized as a mixture of all sedimentary and crystalline target components, and, when compared to the impactites, it contains a significant amount of a SiO 2 -rich target component of sedimentary origin. The chemical composition of the impactites overlaps the compositional range for the Exmore breccia. The impactites generally display a negative correlation of SiO 2 and CaO, and a positive correlation of TiO 2 , Al 2 O 3 , Fe 2 O 3 , and MgO with depth. This is the result of an increasing basement schist component, and a decreasing sedimentary and/or granitic component with depth. Suevite units S2 and S3 display distinct enrichment of Na 2 O by a factor of ̃2 compared to all other impactite units, which is interpreted to reflect a higher granitic component in these units. © 2009 The Geological Society of America. 2009 10.1130/2009.2458(22) Special Paper of the Geological Society of America 458 481-541 Museum für Naturkunde-Leibniz Institute, Humboldt University Berlin, Invalidenstrasse 43, 10115 Berlin, Germany; Department of Lithospheric Research, Center for Earth Sciences, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria; Impact Cratering Research Group, School of Geosciences, University of the Witwatersrand, Private Bag 3, PO Wits, Johannesburg, 2050, South Africa; Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, TX 77058, United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-74949119586&doi=10.1130%2f2009.2458%2822%29&partnerID=40&md5=4d98fae5966f516484085e0f3568d599 cited By 18 R.T. Schmitt K. Bartosova W.U. Reimold D. Mader A. Wittmann C. Koeberl R.L. Gibson article Bartosova2009397 The Chesapeake Bay impact structure, which is 85 km in diameter and 35.5 Ma old, was drilled and cored in a joint International Continental Scientific Drilling Program (ICDP) and U.S. Geological Survey (USGS) drilling project at Eyreville Farm, Virginia, U.S.A. In the Eyreville drill core, 154 m of impact breccia were recovered from the depth interval 1397-1551 m. Major- and trace-element concentrations were determined in 75 polymict impactite samples, 10 samples of cataclastic gneiss blocks, and 24 clasts from impactites. The chemical composition of the polymict impactites does not vary much in the upper part of the section (above ̃1450 m), whereas in the lower part, larger differences occur. Polymict impactites show a decrease of SiO 2 content, and slight increases of TiO 2 , Al 2 O 3 , and Fe 2 O 3 abundances, with depth. This is in agreement with an increase of the schist/gneiss component with depth. Concentrations of siderophile elements (Co, Ni) are lower in the polymict impactites than in the basement-derived schists and do not indicate the presence of an extraterrestrial component. The fi ve petrographically determined types of melt particles, i.e., clear glass, altered melt, recrystallized silica melt, melt with microlites, and dark-brown melt, have distinct chemical compositions. Mixing calculations of the proportions of rocks involved in the formation of various polymict impactites and melt particles were carried out using the Harmonic least-squares MiXing (HMX) calculation program. The calculations suggest that the metamorphic basement rocks (i.e., gneiss and schist) constitute the main component of the polymict impactites, together with significant sedimentary and possible minor pegmatite/granite and amphibolite components. The sedimentary component is derived mostly from a sediment characterized by a composition similar to that of the Cretaceous Potomac Formation. Compositions of the melt particles were modeled as mixtures of target rocks or major rock-forming minerals. However, the results of the mixing calculations for the melt particles are not satisfactory, and the composition of the particles could have been modified by hydrothermal alteration. Carbon isotope ratios were determined for 18 samples. The results imply a hydrothermal origin for the carbonate veins from the basement-derived core section; carbon-rich sedimentary clasts from the Exmore breccia and suevite have a δ 13 C range typical for organic matter in sediments. © 2009 The Geological Society of America. 2009 10.1130/2009.2458(18) Special Paper of the Geological Society of America 458 397-433 Department of Lithospheric Research, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria; Museum für Naturkunde-Leibniz Institute, Humboldt University Berlin, Invalidenstrasse 43, 10115 Berlin, Germany; Department of Earth Science, University of Western Ontario, 1151 Richmond Street, London, ON N6A 5B7, Canada; Natural History Museum, Burgring 7, A-1010 Vienna, Austria https://www.scopus.com/inward/record.uri?eid=2-s2.0-74949095526&doi=10.1130%2f2009.2458%2818%29&partnerID=40&md5=a301fa5740f3c47995c05de4253e7778 cited By 13 K. Bartosova D. Mader R.T. Schmitt L. Ferrière C. Koeberl W.U. Reimold F. Brandstätter article WrightHortonJr.200921 The International Continental Scientific Drilling Program (ICDP)-U.S. Geological Survey (USGS) Eyreville drill cores from the Chesapeake Bay impact structure provide one of the most complete geologic sections ever obtained from an impact structure. This paper presents a series of geologic columns and descriptive lithologic information for the lower impactite and crystalline-rock sections in the cores. The lowermost cored section (1766-1551 m depth) is a complex assemblage of mica schists that commonly contain graphite and fibrolitic sillimanite, intrusive granite pegmatites that grade into coarse granite, and local zones of mylonitic deformation. This basement-derived section is variably overprinted by brittle cataclastic fabrics and locally cut by dikes of polymict impact breccia, including several suevite dikes. An overlying succession of suevites and lithic impact breccias (1551-1397 m) includes a lower section dominated by polymict lithic impact breccia with blocks (up to 17 m) and boulders of cataclastic gneiss and an upper section (above 1474 m) of suevites and clast-rich impact melt rocks. The uppermost suevite is overlain by 26 m (1397-1371 m) of gravelly quartz sand that contains an amphibolite block and boulders of cataclasite and suevite. Above the sand, a 275-m-thick allochthonous granite slab (1371-1096 m) includes gneissic biotite granite, fine- and medium-to-coarse-grained biotite granites, and red altered granite near the base. The granite slab is overlain by more gravelly sand, and both are attributed to debris-avalanche and/or rockslide deposition that slightly preceded or accompanied seawater-resurge into the collapsing transient crater. © 2009 The Geological Society of America. 2009 10.1130/2009.2458(02) Special Paper of the Geological Society of America 458 21-49 U.S. Geological Survey, 12201 Sunrise Valley Drive, Reston, VA 20192, United States; Impact Cratering Research Group, School of Geosciences, University of the Witwatersrand, P.O. Wits, Johannesburg 2050, South Africa; Museum für Naturkunde-Leibniz Institute, Humboldt University Berlin, Invalidenstrasse 43, 10115 Berlin, Germany; Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, TX 77058-1113, United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-74949138582&doi=10.1130%2f2009.2458%2802%29&partnerID=40&md5=27102863d25ef1c8ea299619c263b6e4 cited By 40 J. Wright Horton Jr. R.L. Gibson W.U. Reimold A. Wittmann G.S. Gohn L.E. Edwards article Schulte20091180 An up to ∼2-cm thick Chicxulub ejecta deposit marking the Cretaceous-Paleogene (K-Pg) boundary (the "K-T" boundary) was recovered in six holes drilled during ODP Leg 207 (Demerara Rise, tropical western Atlantic). Stunning features of this deposit are its uniformity over an area of 30 km2 and the total absence of bioturbation, allowing documentation of the original sedimentary sequence. High-resolution mineralogical, petrological, elemental, isotopic (Sr-Nd), and rock magnetic data reveal a distinct microstratigraphy and a range of ejecta components. The deposit is normally graded and composed predominantly of rounded, 0.1- to max. 1-mm sized spherules. Spherules are altered to dioctahedral aluminous smectite, though occasionally relict Si-Al-rich hydrated glass is also present, suggesting acidic precursor lithologies. Spherule textures vary from hollow to vesicle-rich to massive; some show in situ collapse, others include distinct Fe-Mg-Ca-Ti-rich melt globules and lath-shaped Al-rich quench crystals. Both altered glass spherules and the clay matrix (Site 1259B) display strongly negative εNdT = 65 Ma values (-17) indicating uptake of Nd from contemporaneous ocean water during alteration. Finally, Fe-Mg-rich spherules, shocked quartz and feldspar grains, few lithic clasts, as well as abundant accretionary and porous carbonate clasts are concentrated in the uppermost 0.5-0.7 mm of the deposit. The carbonate clasts display in part very unusual textures, which are interpreted to be of shock-metamorphic origin. The preservation of delicate spherule textures, normal grading with lack of evidence for traction transport, and sub-millimeter scale compositional trends provide evidence for this spherule deposit representing a primary air-fall deposit not affected by significant reworking. The ODP Leg 207 spherule deposit is the first known dual-layer K-Pg boundary in marine settings; it incorporates compositional and stratigraphic aspects of both proximal and distal marine sites. Its stratigraphy strongly resembles the dual-layer K-Pg boundary deposits in the terrestrial Western Interior of North America (although there carbonate phases are not preserved). The occurrence of a dual ejecta layer in these quite different sedimentary environments - separated by several thousands of kilometers - provides additional evidence for an original sedimentary sequence. Therefore, the layered nature of the deposit may document compositional differences between ballistic Chicxulub ejecta forming the majority of the spherule deposit, and material falling out from the vapor (ejecta) plume, which is concentrated in the uppermost part. © 2008 Elsevier Ltd. All rights reserved. 2009 10.1016/j.gca.2008.11.011 Geochimica et Cosmochimica Acta 73 1180-1204 GeoZentrum Nordbayern, Universität Erlangen-Nürnberg, Schlossgarten 5, D-91054 Erlangen, Germany; Institut für Planetologie, Universität Münster, D-48149 Muenster, Germany; Bruker AXS Microanalysis GmbH, Schwarzschildstr. 12, D-12489 Berlin, Germany; Institut für Mineralogie, Universität Münster, D-48149 Muenster, Germany; Geologisches Institut der Universität Karlsruhe, Strukturgeologie und Tektonophysik, D-76187 Karlsruhe, Germany; Department of Geological Sciences, University of Missouri, Columbia, MO 65211, United States; Department of Geology, Mineralogy and Geophysics, Ruhr-Universität Bochum, D-44801 Bochum, Germany 4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-58549085746&doi=10.1016%2fj.gca.2008.11.011&partnerID=40&md5=77108d71476736120eec21f9eaf0ca86 cited By 45 P. Schulte A. Deutsch T. Salge J. Berndt A. Kontny K.G. MacLeod R.D. Neuser S. Krumm article Gilli2009723 The surface geology of the site of the Chicxulub impact crater in northwestern Yucatán, Mexico, has not been studied extensively since the discovery of the crater almost two decades ago. Strontium isotope (87Sr/86Sr) measurements in carbonate rock outcrops reveal near-uniform strontium signatures of 0.70905 inside the ring of cenotes (water-filled sinkholes), which represents the rim of the crater basin. Measured strontium isotope ratios were used to infer rock ages, employing the marine Sr isotope curve. We estimate the age of the exposed limestone within the Chicxulub crater basin to be late Miocene to early Pliocene, representing the age of the youngest sediment fill. Discovery of a large terrain of near-uniform strontium isotope ratios in northwestern Yucatán offers new geoarchaeological opportunities to track ancient Maya migration and determine sources of manufactured goods. Our results have implications for applying the Sr isotope method to Maya archaeological sites, such as Mayapán, the last Maya capital, and Chichén Itzá. © 2009 Geological Society of America. 2009 10.1130/G30098A.1 Geology 37 723-726 Geological Institute, ETH Zurich, Sonneggstrasse 5, 8092 Zurich, Switzerland; Department of Geological Sciences, Land Use and Environmental Change Institute (LUECI), University of Florida, 241 Williamson Hall, Gainesville, FL 32611, United States; Godwin Laboratory for Palaeoclimate Research, Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, United Kingdom 8 https://www.scopus.com/inward/record.uri?eid=2-s2.0-69649097569&doi=10.1130%2fG30098A.1&partnerID=40&md5=d4933b5a2cbf92877b6218db629bc54a cited By 19 A. Gilli D.A. Hodell G.D. Kamenov M. Brenner article Grieve2008855 The structural, topographic and other characteristics of the Vredefort, Sudbury, and Chicxulub impact structures are described. Assuming that the structures originally had the same morphology, the observations/ interpretations for each structure are compared and extended to the other structures. This does not result in any major inconsistencies but requires that the observations be scaled spatially. In the case of Vredefort and Sudbury, this is accomplished by scaling the outer limit of particular shock metamorphic features. In the case of Chicxulub, scaling requires a reasoned assumption as to the formation mechanism of an interior peak ring. The observations/interpretations are then used to construct an integrated, empirical kinematic model for a terrestrial peak-ring basin. The major attributes of the model include: a set of outward-directed thrusts in the parautochthonous rocks of the outermost environs of the crater floor, some of which are pre-existing structures that have been reactivated during transient cavity formation; inward-directed motions along the same outermost structures and along a set of structures, at intermediate radial distances, during transient cavity collapse; structural uplift in the center followed by a final set of radially outward-directed thrusts at the outer edges of the structural uplift, during uplift collapse. The rock displacements on the intermediate, inward and innermost, outward sets of structures are consistent with the assumption that a peak ring will result from the convergence of the collapse of the transient cavity rim area and the collapse of the structural uplift. © The Meteoritical Society, 2008. 2008 10.1111/j.1945-5100.2008.tb01086.x Meteoritics and Planetary Science 43 855-882 Earth Sciences Sector, Natural Resources Canada, Ottawa, ON K1A 0E4, Canada; Humboldt Universität zu Berlin, Museum für Naturkunde, D-10115 Berlin, Germany; Department of Earth Science and Engineering, Imperial College London, London SW7 2AZ, United Kingdom 5 https://www.scopus.com/inward/record.uri?eid=2-s2.0-51449087806&doi=10.1111%2fj.1945-5100.2008.tb01086.x&partnerID=40&md5=c8f8de471d99d6e5d5f4bdf185a49d68 cited By 72 R.A.F. Grieve W.U. Reimold J. Morgan U. Riller M. Pilkington article Burt2008755 Before base surges were described in association with nuclear blasts and explosive volcanic eruptions (especially, the 1980 eruption of Mount St. Helens, Washington), laminar and cross-bedded volcanogenic surge deposits were commonly misinterpreted as being of fluvial or aeolian origin. One well-documented example involves the "water-laid tuffs" in and near the Spor Mountain beryllium mine, Utah; other examples abound. In light of how frequently volcanogenic surge deposits have been misinterpreted on Earth, extreme caution is urged for Mars studies. Contrary to what has been claimed, the markedly cross-bedded, salty deposits at Meridiani Planum on Mars need not have been formed by a combination of aeolian and aqueous processes, and their contained hematitic spherules need not have formed as aqueous concretions. Given the lack of indications of volcanism in the vicinity, and the planet-wide abundance of impact craters, deposition by surges associated with distant impact targets consisting of brine-soaked, locally sulfidic regolith is a reasonable explanation for all features observed, especially if diagenesis and weathering are considered. The uniformly sized and shaped, Ni-enriched blue-gray hematitic spherules would then be some type of vapor condensation spherules (including accretionary lapilli). A similar interpretation is possible for deposits in the Home Plate area, Gusev Crater. Unlike on the dry and atmosphereless Moon, salty impact surge deposits containing spherules should be common, and well-preserved, on Mars. © 2008 Elsevier B.V. 2008 10.1016/j.jvolgeores.2008.01.044 Journal of Volcanology and Geothermal Research 177 755-759 School of Earth and Space Exploration, Arizona State University, Box 871404, Tempe, AZ 85287-1404, United States; Los Alamos National Laboratory, Los Alamos, NM 87545, United States; Deparment of Geology, SUNY at Buffalo, 876 Natural Science Complex, Buffalo, NY 14260, United States 4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-55649095529&doi=10.1016%2fj.jvolgeores.2008.01.044&partnerID=40&md5=cf3e24f04b371cfb2ae13e843ab0dd2c cited By 3 D.M. Burt L.P. Knauth K.H. Wohletz M.F. Sheridan article Paquay2008 Morgan argues that excursions in the marine Os record are of little value for estimating impactor size. This claim is based on computer simulations of the formation of the Chicxulub crater and distribution of the ejecta, which are difficult to validate. More important, by narrowly focusing on the Cretaceous-Tertiary event Morgan's comment misses the broader implications of our study. 2008 10.1126/science.1159234 Science 321 1158b Department of Geology and Geophysics, University of Hawaii, Honolulu, HI 96822-2225, United States; Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur 721302, India; Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, United States 5893 https://www.scopus.com/inward/record.uri?eid=2-s2.0-50649089574&doi=10.1126%2fscience.1159234&partnerID=40&md5=68561a1b6de04649562f469c91984438 cited By 1 F.S. Paquay G.E. Ravizza T.K. Dalai B. Peucker-Ehrenbrink article Keller2008621 2008 10.1016/j.epsl.2007.12.025 Earth and Planetary Science Letters 269 621-629 Geosciences, Princeton University, Princeton, NJ 08540, United States; Geological Institute, University of Neuchatel, Neuchatel, CH-2007, Switzerland; Baum and Associates LLC, 53 Inwood Heights Dr. N, San Antonio, TX 78248, United States; Institute for Mineralogy and Geochemistry, University of Karlsruhe, 76128 Karlsruhe, Germany 3-4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-43249128540&doi=10.1016%2fj.epsl.2007.12.025&partnerID=40&md5=e4f5c1d11590b6eacc8fa617f6583acf cited By 13 G. Keller T. Adatte G. Baum Z. Berner article Urrutia-Fucugauchi2008248 The Chicxulub crater has attracted considerable attention as one of the largest terrestrial impact structures and its association with the Cretaceous/Palaeogene boundary. Analyses of stable isotopes and magnetostratigraphic results for the Paleocene carbonate sequence in the Santa Elena borehole are used to investigate the post-impact sequence and estimate the age of basal sediments in the southern crater sector. Studies of impact ejecta and cover sediments and modelling of post-impact processes suggest erosion effects due to seawater back surge, block slumping and partial rim collapse of post-impact crater modification. Correlation of stable isotope patterns with the global pattern for marine carbonate sediments provides a stratigraphic framework for the basal Paleocene carbonates. Magnetic polarity constrains correlation of stable isotope variations with the reference Cenozoic isotopic data suggest that the first 17 m above the breccia-carbonate contact represents about 2.5 Ma. The stable isotope data suggest a gap of less than 0.1 Ma, whereas the magnetic polarity data (absence of reverse-polarity samples above impact breccia contact) suggest a gap up to 0.25 Ma. 2008 Current Science 95 248-252 Laboratorio de Paleomagnetismo Y Paleoambientes, Instituto de Geofisica, Ciudad Universitaria, Circuito Exterior S/N, Coyoacan, DF 04510, Mexico 2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-47949100674&partnerID=40&md5=e9a656aac3631cde4da80f3a5ce665b5 cited By 12 J. Urrutia-Fucugauchi L. Pérez-Cruz article Nakano2008745 We measured 852 sets of planar deformation features (PDFs) in shocked quartz grains in impactite samples of the Yaxcopoil (YAX-1) core and from 4 Cretaceous/Tertiary (K/T) boundary deposits: the Monaca, the Cacarajícara, and the Peñalver formations in Cuba, and DSDP site 536, within 800 km of the Chicxulub crater, in order to investigate variations of PDF orientations in the proximity of the crater. Orientations of PDFs show a broad distribution with peaks at ω {1013}, π {1012}, and ξ {1112}, plus r, z {1011} orientations with minor c(0001), s{1121}, t{2241} plus x{5161}, and m{1010} plus a{1120} orientations. Planar deformation features with c(0001) orientation are relatively more abundant in the proximity of the Chicxulub crater than in distal sites such as North America, the Pacific Ocean, and Europe. This feature indicates that in the proximity of the crater, part of the shocked quartz grains in the K/T boundary deposits were derived from the low shock pressure zones. Moreover, the orientations of PDFs with ξ {1122} plus r, z {1011} are high in our studied sites, and frequencies of these orientations decrease with increasing distance from the crater. On the other hand, absence of c(0001) and the rare occurrence of PDFs with ξ {1122} plus r, z {1011} orientations in the sample from the YAX-1 core that was taken at the top of the impactite layer of the Chicxulub crater suggests that the sampling horizon that reflects a certain cratering stage is also an important factor for variations in shocked quartz. © The Meteoritical Society, 2008. 2008 10.1111/j.1945-5100.2008.tb00682.x Meteoritics and Planetary Science 43 745-760 Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Build 5, 7-3-1 Hongo, Tokyo 113-0033, Japan; Tsunami Engineering Laboratory, Disaster Control Research Center, Tohoku University, Aoba 06-6-11, Aramaki, Sendai 980-8579, Japan; Department of Complexity Science and Engineering, Graduate School of Frontier Science, The University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan 4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-52949154356&doi=10.1111%2fj.1945-5100.2008.tb00682.x&partnerID=40&md5=339fcbc0a0e760a74c3c0b7c4775a986 cited By 5 Y. Nakano K. Goto T. Matsui R. Tada E. Tajika article Mayr2008385 Internal surface, formation factor, Nuclear Magnetic Resonance (NMR)-T2 relaxation times and pore radius distributions were measured on representative core samples for the estimation of hydraulic permeability. Permeability is estimated using various versions of the classic Kozeny-Carman-equation (K-C) and a further development of K-C, the fractal PaRiS-model, taking into account the internal surface. In addition to grain and pore size distribution, directly connected to permeability, internal surface reflects the internal structure ("micro morphology"). Lithologies could be grouped with respect to differences in internal surface. Most melt rich impact breccia lithologies exhibit large internal surfaces, while Tertiary post-impact sediments and Cretaceous lithologies in displaced megablocks display smaller internal surfaces. Investigations with scanning electron microscopy confirm the correlation between internal surface and micro morphology. In addition to different versions of K-C, estimations by means of NMR, pore radius distributions and some gas permeability measurements serve for cross-checking and calibration. In general, the different estimations from the independent methods and the measurements are in satisfactory accordance. For Tertiary limestones and Suevites bulk with very high porosities (up to 35%) permeabilites between 10-14 and 10-16 m2 are found, whereas in lower Suevite, Cretaceous anhydrites and dolomites, bulk permeabilites are between 10-15 and 10-23m2. © Springer-Verlag 2007. 2008 10.1007/s00531-007-0227-6 International Journal of Earth Sciences 97 385-399 Department of Applied Geosciences, Technical University Berlin, Sekr. ACK 2, Ackerstraße 71-76, 13355 Berlin, Germany; Technical physics and rock physics, Russian State Geological Prospecting University, Miklukho-Maklaya street 23, 117997 Moscow, Russian Federation; Humboldt-Universität zu Berlin, Museum für Naturkunde, Mineralogie, Invalidenstrasse 43, 10115 Berlin, Germany 2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-41349086215&doi=10.1007%2fs00531-007-0227-6&partnerID=40&md5=8a122981f2c65859e22e734a326797b8 cited By 17 S.I. Mayr H. Burkhardt Yu. Popov A. Wittmann article Mayr2008 The borehole Yaxcopoil-1, drilled within the Chicxulub meteoritic impact structure (Mexico), was completely cored from 404 to 1511 in through postimpact Tertiary limestones underlain by impactites. The impactites comprise impact melt-rich, suevitic breccia followed by megablocks of Cretaceous limestones, calcarenites, dolomites, and anhydrites. Measurements of porosity, density, and thermal parameters on 450 samples (equidistant sampling, complete depth range) and of ultrasonic velocities and electric resistivity on 80 representative samples are used to investigate the physical properties of carbonate rocks and to study the influence of the impact. Experiments under elevated pressure, calculations using frequency-dependent Biot-Gassmann theory, and cross-checking with borehole logs, where available, show that ultrasonic laboratory and sonic in situ data correspond. Sonic and electric quasi-continuous logs are obtained from empirical correlations with thermal conductivity, density, and porosity and consideration of mineralogical composition and microstructure. These data give constraints on interpretation and geophysical modeling of, e.g., seismic and gravity data. In the Tertiary postimpact limestone section, the rock fabric (porosity) influences the physical properties. The upper boundary of the impactites is distinctly determined by the high inhomogeneity factor and anisotropy coefficient of thermal conductivity and by the temperature gradient from high-resolution borehole temperature measurements. All physical properties indicate that the upper part of the suevitic breccia can be distinguished from the lower suevite unit. In the Cretaceous megablocks, a high variability of all properties (particularly, thermal conductivity, density of solid material, and temperature gradient) due to the high variability in the mineral composition (calcite, dolomite, anhydrite) is observed. Copyright 2008 by the American Geophysical Union. 2008 10.1029/2007JB005420 Journal of Geophysical Research: Solid Earth 113 Angewandte Geophysik, Technische Universitaet Berlin, Sekr. ACK 2, Ackerstrasse 71-76, D-13355 Berlin, Germany; Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, TX 77058, United States; Laboratory of Technical Physics, Russian State Geological Prospecting University, Miklukho-Maklaya street 23, 117997 Moscow, Russian Federation; Geophysikalisches Institut, Universitaet Karlsruhe, Hertzstrase 16, D-76187 Karlsruhe, Germany 7 https://www.scopus.com/inward/record.uri?eid=2-s2.0-51449121163&doi=10.1029%2f2007JB005420&partnerID=40&md5=ffd6edd61e56b93ea14c32828340ffa4 cited By 23 S.I. Mayr A. Wittmann H. Burkhardt Y. Popov R. Romushkevich I. Bayuk P. Heidinger H. Wilhelm article Urrutia-Fucugauchi2008801 The Chicxulub 200 km diameter crater located in the Yucatan platform of the Gulf of Mexico formed 65 Myr ago and has since been covered by Tertiary post-impact carbonates. The sediment cover and absence of significant volcanic and tectonic activity in the carbonate platform have protected the crater from erosion and deformation, making Chicxulub the only large multi-ring crater in which ejecta is well preserved. Ejecta deposits have been studied by drilling/coring in the southern crater sector and at outcrops in Belize, Quintana Roo and Campeche; little information is available from other sectors. Here, we report on the drilling/coring of a section of ∼34 m of carbonate breccias at 250 m depth in the Valladolid area (120 km away from crater center), which are interpreted as Chicxulub proximal ejecta deposits. The Valladolid breccias correlate with the carbonate breccias cored in the Peto and Tekax boreholes to the south and at similar radial distance. This constitutes the first report of breccias in the eastern sector close to the crater rim. Thickness of the Valladolid breccias is less than that at the other sites, which may indicate erosion of the ejecta deposits before reestablishment of carbonate deposition. The region east of the crater rim appears different from regions to the south and west, characterized by high density and scattered distribution of sinkholes. © 2008 Académie des sciences. 2008 10.1016/j.crte.2008.09.001 Comptes Rendus - Geoscience 340 801-810 Laboratorio de Paleomagnetismo y Paleoambientes, Programa Universitario de Perforaciones en Oceanos y Continentes, Instituto de Geofísica, DF, 04510 Mexico, Mexico; Departamento de Geología, Comisión Federal de Electricidad (CFE), GEIC-CFE, Mexico DF, Mexico; Residencia de Geohidrologia, Comisión Federal de Electricidad (CFE), Mérida, Yucatan, Mexico 12 https://www.scopus.com/inward/record.uri?eid=2-s2.0-57049165378&doi=10.1016%2fj.crte.2008.09.001&partnerID=40&md5=21d1de6b6e69ed07be60b405841751ae cited By 30 J. Urrutia-Fucugauchi J.M. Chavez-Aguirre L. Pérez-Cruz J.L. Rosa book Ivanov2008163 To date around 180 impact structures have been identified on Earth. The diameters of these structures are from ∼10 to ∼200-250 km. Knowledge about terrestrial impact structures accumulated during many decades includes a large amount of geological and geophysical data. These data are very useful in formulating important constraints for impact model parameters reaching a double goal: (1) to fit parameters in the available mechanical models of planetary crust reaction to the impact event, and (2) to use numerical modeling to make an insight into the possible original structure of partially eroded terrestrial impact structures. This chapter presents results of numerical modeling for selected terrestrial impact craters (Puchezh-Karunki, Popigai, Vredefort, Sudbury, and Chicxulub) and compares model results with available geologic and geophysical data, obtained in the field study of aforementioned structures. © 2008 Springer. 2008 10.1007/978-1-4020-6452-4_5 Catastrophic Events Caused by Cosmic Objects 163-205 Institute for Dynamics of Geospheres, Russian Academy of Sciences, Moscow 119334, Russian Federation https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891367573&doi=10.1007%2f978-1-4020-6452-4_5&partnerID=40&md5=157f0a56d954484fb698fec979e61926 cited By 6 B. Ivanov article Collins2008221 We investigate the cause of terrace zone asymmetry in the Chicxulub impact crater using dynamic models of crater formation. Marine seismic data acquired across the crater show that the geometry of the crater's terrace zone, a series of sedimentary megablocks that slumped into the crater from the crater rim, varies significantly around the offshore half of the crater. The seismic data also reveal that, at the time of impact, both the water depth and sediment thickness varied with azimuth around the impact site. To test whether the observed heterogeneity in the pre-impact target might have affected terrace zone geometry we constructed two end-member models of upper-target structure at Chicxulub, based on the seismic data at different azimuths. One model, representing the northwest sector, had no water layer and a 3-km thick sediment layer; the other model, representing the northeast sector, had a 2-km water layer above a 4-km sediment layer. Numerical models of vertical impacts into these two targets produced final craters that differ substantially in terrace zone geometry, suggesting that the initial water depth and sediment thickness variations affected the structure of the terrace zone at Chicxulub. Moreover, the differences in terrace zone geometry between the two numerical models are consistent with the observed differences in the geometry of the terrace zone at different azimuths around the Chicxulub crater. We conclude that asymmetry in the pre-impact target rocks at Chicxulub is likely to be the primary cause of asymmetry in the terrace zone. © 2008 Elsevier B.V. All rights reserved. 2008 10.1016/j.epsl.2008.03.032 Earth and Planetary Science Letters 270 221-230 Earth Science and Engineering, Imperial College, London, United Kingdom; Earth Sciences, University of Cambridge, United Kingdom; Institute for Geophysics, Jackson School of Geosciences, TX, United States; Institute of Geophysics, UNAM, Mexico; Museum für Naturkunde, Humboldt-Universität Berlin, Germany 3-4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-44649194411&doi=10.1016%2fj.epsl.2008.03.032&partnerID=40&md5=6f1127866871d2bb514b64e133deb029 cited By 96 G.S. Collins J. Morgan P. Barton G.L. Christeson S. Gulick J. Urrutia M. Warner K. Wünnemann article Gohn20081740 Samples from a 1.76-kilometer-deep corehole drilled near the center of the late Eocene Chesapeake Bay impact structure (Virginia, USA) reveal its geologic, hydrologic, and biologic history. We conducted stratigraphic and petrologic analyses of the cores to elucidate the timing and results of impact-melt creation and distribution, transient-cavity collapse, and ocean-water resurge. Comparison of post-impact sedimentary sequences inside and outside the structure indicates that compaction of the crater fill influenced long-term sedimentation patterns in the mid-Atlantic region. Salty connate water of the target remains in the crater fill today, where it poses a potential threat to the regional groundwater resource. Observed depth variations in microbial abundance indicate a complex history of impact-related thermal sterilization and habitat modification, and subsequent post-impact repopulation. 2008 10.1126/science.1158708 Science 320 1740-1745 U.S. Geological Survey, Reston, VA 20192, United States; Department of Lithospheric Research, Center for Earth Sciences, University of Vienna, Althanstrasse 14, Vienna A-1090, Austria; Department of Geological Sciences, Rutgers University, 610 Taylor Road, Piscataway, NJ 08854, United States; Museum of Natural History (Mineralogy), Humboldt-University Berlin, Invalidenstrasse 43, Berlin 10115, Germany; Centre for Earth, Planetary, Space, and Astronomical Research, Open University, Milton Keynes MK7 6AA, United Kingdom 5884 https://www.scopus.com/inward/record.uri?eid=2-s2.0-46449110214&doi=10.1126%2fscience.1158708&partnerID=40&md5=cb49fd084b10d1cb6073d9c85b47ff28 cited By 92 G.S. Gohn C. Koeberl K.G. Miller W.U. Reimold J.V. Browning C.S. Cockell J.W. Horton Jr. T. Kenkmann A.A. Kulpecz D.S. Powars W.E. Sanford M.A. Voytek article Schulte2008614 2008 10.1016/j.epsl.2007.11.066 Earth and Planetary Science Letters 269 614-620 Institut für Geologie und Mineralogie, Universität Erlangen, Schlossgarten 5, D-91054 Erlangen, Germany; Department of Geography-Geology, K.U.Leuven, Celestijnenlaan 200E, B-3001 Leuven, Belgium; Institute of Environmental Biology (IEB), Laboratory of Palaeobotany and Palynology, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, Netherlands; Geologisch-Paläontologisches Institut, Universität Heidelberg, Im Neuenheimer Feld 234, D-69120 Heidelberg, Germany; Department of Geology, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium; Istituto di Scienze della Terra, Università degli Studi di Urbino, Campus Scientifico, Localita Crocicchia, 61029 Urbino, Italy; Sedimentology Group, Vrije Universiteit, de Boelelaan 1085, 1081 HV Amsterdam, Netherlands 3-4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-43249094377&doi=10.1016%2fj.epsl.2007.11.066&partnerID=40&md5=94b61551ad046cc3716fdf8d310c93ed cited By 13 P. Schulte R.P. Speijer H. Brinkhuis A. Kontny P. Claeys S. Galeotti J. Smit article Kramar2007824 Synchrotron radiation, collimated to a μm scale was used for the determination of trace elements in micro-tektites and spherule material for the first time. The experimental set-up of the SXRF microprobe at beamline L at HASYLAB at DESY offers a suitable method for performing non-destructive in situ multi-element analysis focusing on spatial trace element distributions and mineral phases of the melted ejecta material from the Cretaceous/Tertiary boundary. The spatial distribution of trace elements was determined in melt inclusions as well as in phase transitions in selected parts of chlorite-smectite spherules and tektite glass material by using a beam with a diameter of 15 μm collimated with a glass capillary for line- and area scans as well as for single point measurements for elements with Z between 19 and 92. The analyzed spherules show alteration features but also zonation and carbonate inclusions, originating from the Chicxulub impact event. These initial results demonstrate the potential of μ-SXRF analysis for the discrimination of alteration and primary signals of the spherules and re-construction of their genetic evolution. It could be shown that the spherules represent a complex mixture of different materials from the subsurface at the Chicxulub impact site. © 2007 Elsevier B.V. All rights reserved. 2007 10.1016/j.sab.2007.06.012 Spectrochimica Acta - Part B Atomic Spectroscopy 62 824-835 Universität Karlsruhe (TH), Institut für Mineralogie und Geochemie, Kaiserstraße 12, D-76128 Karlsruhe, Germany; Utrecht University, Department of Earthsciences, Budapestlaan 4, 3508 TA Utrecht, Netherlands; Hamburger Synchrotronstrahlungslabor HASYLAB at Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany; GeoForschungsZentrum Potsdam, Division 4.1, Telegrafenberg, 14473 Potsdam, Germany 8 https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547951153&doi=10.1016%2fj.sab.2007.06.012&partnerID=40&md5=2d65eff9a3d50638cf40f7e394f84f94 cited By 3 U. Kramar M. Harting K. Rickers D. Stüben article Morgan200742 2007 10.2204/iodp.sd.4.11.2007 Scientific Drilling 42-44 Department of Earth Science and Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom; University of Texas Institute for Geophysics, J.J. Pickle Research Campus, 10100 Burnet Rd., Austin, TX 78759-8500, United States; Natural Resources Canada, 580 Booth Street, Ottawa, ON K1A 0E4, Canada; Instituto de Geofisica, Universidad Nacional Autónoma de México, Del Coyoacan Mexico D.F. 04510, Mexico; Department of Earth Sciences, University of Cambridge, Madingley Rise, Cambridge CB3 0EZ, United Kingdom; Centro de Investigación Cientifica de Yucatán, Calle 8 39, Cancun, México 77500, Mexico; Lunar and Planetary Laboratory, University of Arizona, Tuscon, AZ 85721, United States 4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-69649099663&doi=10.2204%2fiodp.sd.4.11.2007&partnerID=40&md5=18e83ff3df39616811dae65a0e2f3947 cited By 2 J.V. Morgan G. Christeson S. Gulick R. Grieve J. Urrutia P. Barton M. Rebolledo J. Melosh article Wittmann20071151 Formation conditions of suevite-like impactites from an ∼100 m thick drill core sequence through the Cretaceous-Tertiary Chicxulub crater were reconstructed from empirical data obtained by petrologic and image analytical methods. The temporal evolution of the cratering process from the initial stage of excavation to the collapse of the ejecta plume is evidenced by the petrographic characteristics and modal composition of the suevitic rocks, including the size distribution and shape parameters of melt particles. Emplacement of the lowermost suevitic deposits likely started in the first minute after the impact by the passing ejecta curtain that interacted with the expanding ejecta plume. These ejecta deposits were capped by a tongue of coherent impact melt that was transported outward from the crater center during the collapse of the central uplift ∼5 min after impact. On top of this brecciated impact melt rock, the collapsing ejecta plume deposited air-fall suevites. The basal air-fall unit, Middle Suevite, may have been deposited due to a density current-like clumping of hot debris. With progressive cooling, regions of the ejecta plume were entrained in its collapse that produced vapor condensates, accretionary rims, and different oxygen fugacities. After cooling progressed, atmospheric conditions began to reestablish over the crater and turbulence decreased, supposedly after the first 10 min of initial ejecta plume collapse. This led to a winnowing out of fine matrix material and distinct sorting. However, due to aquatic reworking, only material that was deposited until ∼1 h after cessation of turbulent atmospheric conditions was retained. © 2007 Geological Society of America. 2007 10.1130/B26116.1 Bulletin of the Geological Society of America 119 1151-1167 Museum für Naturkunde, Mineralogie, Invalidenstrasse 43, 10115 Berlin, Germany; 250 Little St., Athens, GA 30605, United States 9-10 https://www.scopus.com/inward/record.uri?eid=2-s2.0-34648846171&doi=10.1130%2fB26116.1&partnerID=40&md5=990afa31bfc215efb0d28145210bb5e8 cited By 27 A. Wittmann T. Kenkmann L. Hecht D. Stöffler article Tsikalas20072013 Post-impact crater morphology and structure modifications due to sediment loading are analyzed in detail and exemplified in five well-preserved impact craters: Mjølnir, Chesapeake Bay, Chicxulub, Montagnais, and Bosumtwi. The analysis demonstrates that the geometry and the structural and stratigraphic relations of post-impact strata provide information about the amplitude, the spatial distribution, and the mode of post-impact deformation. Reconstruction of the original morphology and structure for the Mjølnir, Chicxulub, and Bosumtwi craters demonstrates the long-term subsidence and differential compaction that takes place between the crater and the outside platform region, and laterally within the crater structure. At Mjølnir, the central high developed as a prominent feature during post-impact burial, the height of the peak ring was enhanced, and the cumulative throw on the rim faults was increased. The original Chicxulub crater exhibited considerably less prominent peak-ring and inner-ring/crater-rim features than the present crater. The original relief of the peak ring was on the order of 420-570 m (currently 535-575 m); the relief on the inner ring/ crater rim was 300-450 m (currently ∼700 m). The original Bosumtwi crater exhibited a central uplift/high whose structural relief increased duringburial (current height 101-110 m, in contrast to the original height of 85-110 m), whereas the surrounding western part of the annular trough was subdued more that the eastern part, exhibiting original depths of 43-68 m (currently 46 m) and 49-55 m (currently 50 m), respectively. Furthermore, a quantitative model for the porosity change caused by the Chesapeake Bay impact was developed utilizing the modeled density distribution. The model shows that, compared with the surrounding platform, the porosity increased immediately after impact up to 8.5% in the collapsed and brecciated crater center (currently +6% due to post-impact compaction). In contrast, porosity decreased by 2-3% (currently -3 to -4.5% due to post-impact compaction) in the peak-ring region. The lateral variations in porosity at Chesapeake Bay crater are compatible with similar porosity variations at Mjølnir crater, and are considered to be responsible for the moderate Chesapeake Bay gravity signature (annular low of -8 mGal instead of -15 mGal). The analysis shows that the reconstructions and the long-term alterations due to post-impact burial are closely related to the impact-disturbed target-rock volume and a brecciated region of laterally varying thickness and depth-varying physical properties. The study further shows that several crater morphological and structural parameters are prone to post-impact burial modification and are either exaggerated or subdued during post-impact burial. Preliminary correction factors are established based on the integrated reconstruction and post-impact deformation analysis. The crater morphological and structural parameters, corrected from post-impact loading and modification effects, can be used to better constrain cratering scaling law estimates and impact-related consequences. © The Meteoritical Society, 2007. 2007 10.1111/j.1945-5100.2007.tb00557.x Meteoritics and Planetary Science 42 2013-2029 Department of Geosciences, University of Oslo, P.O. Box 1047 Blindern, NO-0316 Oslo, Norway; ENI Norge AS, P.O. Box 101 Forus, NO-4064 Stavanger, Norway 11 https://www.scopus.com/inward/record.uri?eid=2-s2.0-41549143722&doi=10.1111%2fj.1945-5100.2007.tb00557.x&partnerID=40&md5=c78c1e98890dfb566c012c2b14a32776 cited By 11 F. Tsikalas J.I. Faleide article Šafanda2007423 As part of the International Continental Scientific Drilling Program (ICDP), the 1.5-km-deep borehole Yaxcopoil-1, located in the Chixculub meteor impact structure in Mexico, has undergone further study after drilling operations ceased. Temperature logs were repeated ten times at intervals 0.3-0.8, 15, 24 and 34 months after borehole shut-in. The logs bear a distinct signature of transient heat transfer by groundwater flow manifested by a gradual distortion of the linear temperature profile when acoldwaveof0.8-1.6°C amplitude was detected propagating downward from 145 to 312 m at a rate of 4-6 m/month. To understand the nature of this moving anomaly, a 20-day monitoring of the cold wave was carried out at a depth of 307 m that showed further cooling of 0.6°C during the first 16 days of the passage followed by temperature stabilisation. As an explanation of this unusual phenomenon, a theory is proposed, whereby the drilling mud has accumulated within the overlying and cooler highly porous and permeable karstic rocks during the drilling and migrates downward. The observed migration rate suggests a permeability higher than 10-11 m2. This indicates a high vulnerability to contamination of the only freshwater aquifer in the Yucatan region. © Springer-Verlag 2006. 2007 10.1007/s10040-006-0082-8 Hydrogeology Journal 15 423-428 Geophysical Institute, Boční II/1401, 14131 Prague, Czech Republic; Geophysical Institute, University Karlsruhe, Hertzstrasse 16, 76187 Karlsruhe, Germany 2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-65649098531&doi=10.1007%2fs10040-006-0082-8&partnerID=40&md5=f1a7a79479f1054af06c33d7b828ab5c cited By 8 J. Šafanda P. Heidinger H. Wilhelm V. Čermák article Artemieva2007883 Pre-drilling numerical modeling of the Bosumtwi impact event predicted a 200 m thick coherent melt layer, as well as abundant highly shocked target material within the central part of the crater structure. However, these predictions are in disagreement with data from drill core obtained in 2004-2005. Here I provide a brief overview of previous results and discuss possible reasons behind melt deficiency, such as specific impact scenarios (low impact velocity and/or low impact angle), and specific target properties (different composition, high porosity, high content of volatiles). I conclude that the most likely explanation is the dispersion of impactites due to the vaporization of pore water, which was not included in the original numerical model. © The Meteoritical Society, 2007. Printed in USA. 2007 10.1111/j.1945-5100.2007.tb01083.x Meteoritics and Planetary Science 42 883-894 Institute for Dynamics of Geospheres, Leninsky Prospect 38, 119334 Moscow, Russian Federation; Planetary Science Institute, 1700 East Fort Lowell, Tucson, AZ 85719, United States 4-5 https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250642321&doi=10.1111%2fj.1945-5100.2007.tb01083.x&partnerID=40&md5=f2e1cc99158466407479c5270ed72b8b cited By 23 N. Artemieva article Goderis2007731 In an attempt to identify the type of projectile, 14 samples from the Bosumtwi crater in Ghana were analyzed for platinum group element (PGE) concentrations by nickel sulfide fire assay inductively coupled plasma-mass spectrometry (ICP-MS). The majority of the samples come from the impactite material recovered by cores LB-07A and LB-08A, which were drilled by the International Continental Scientific Drilling program (ICDP). One sample originates from the fallback material found at the contact between the impactite and the overlying lake sediment in core LB-05B. No clear signature of a meteoritic contamination was identified in the 13 impactite samples. The target rock apparently dominates the PGE contribution in the impactites. These results agree with the PGE concentrations reported for the suevites collected at the crater rim and in other parts of the Bosumtwi ICDP cores. However, based on Cr and Os isotopic signatures, a meteoritic component could be present in the sample of fallback material, supporting the reports of the existence of meteoritic material in the Ivory Coast tektites. Further analyses of the fallback material from the Bosumtwi drill cores should confirm (or not) this first result. © The Meteoritical Society, 2007. Printed in USA. 2007 10.1111/j.1945-5100.2007.tb01070.x Meteoritics and Planetary Science 42 731-741 Department of Geology, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium; Department of Geology and Soil Science, Ghent University, Krijgslaan 281, 9000 Ghent, Belgium; Department of Mineralogy, Natural History Museum Berlin, 10099 Berlin, Germany; GeoForschungsZentrum Potsdam, 14473 Potsdam, Germany 4-5 https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250635058&doi=10.1111%2fj.1945-5100.2007.tb01070.x&partnerID=40&md5=457f83b4d36929ae843896d436d3eb39 cited By 17 S. Goderis R. Tagle R.T. Schmitt J. Erzinger Ph. Claeys article Deutsch2007155 In context of the “K/T” Chicxulub cratering event, the amounts of impact-released CO2and SOxas well as the consequences of this gaseous input into the atmosphere are discussed. It has been assumed that degassing of the sediments is an abrupt and violent effect, only related to the amplitude of the post-shock temperature after pressure decay. Here we provide evidence for a different, slow and probably equally important process of devolatilization: degassing and dissociation of sedimentary clasts in impact breccias. The sulfate and carbonate clasts in suevites, melt breccias, and melt rocks from the Chicxulub drill cores Y-6, C-1, and YAX-1, underwent various thermal effects, ranging from solid state re-crystallization over reaction with silicate melt to form pyroxene (diopside), melting (and re-crystallization) to total decomposition with dissolution of the lime in the melt matrix. These features reflect high, yet different formation temperatures of the breccias, and to a smaller degree, the fragment size. © 1996 Scandinavian University Press. 2007 10.1080/11035890701292155 GFF 129 155-160 Institut für Planetologie (IfP), Westfälische Wilhelms-Universität Münster (WWU), Wilhelm-Klemm-Str. 10, Münster, D-48149, Germany; Institut für Geowissenschaften, Friedrich-Schiller-Universität Jena, Burgweg 11, Jena, D-07749, Germany 2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547116853&doi=10.1080%2f11035890701292155&partnerID=40&md5=b1231327ec11f9dba855630773096122 cited By 18 A. Deutsch F. Langenhorst article Abramov200793 Large impact events like the one that formed the Chicxulub crater deliver significant amounts of heat that subsequently drive hydrothenmal activity. We report on numerical modeling of Chicxulub crater cooling with and without the presence of water. The model inputs are constrained by data from borehole samples and seismic, magnetic, and gravity surveys. Model results indicate that initial hydrothermal activity was concentrated beneath the annular trough as well as in the permeable breccias overlying the melt. As the system evolved, the melt gradually cooled and became permeable, shifting the bulk of the hydrothermal activity to the center of the crater. The temperatures and fluxes of fluid and vapor derived from the model are consistent with alteration patterns observed in the available borehole samples. The lifetime of the hydrothermal system ranges from 1.5 to 2.3 Myr depending on assumed permeability. The long lifetimes are due to conduction being the dominant mechanism of heat transport in most of the crater, and significant amounts of heat being delivered to the near-surface by hydrothermal upwellings. The long duration of the hydrothermal system at Chicxulub should have provided ample time for colonization by thermophiles and/or hyperthermophiles. Because habitable conditions should have persisted for longer time in the central regions of the crater than on the periphery, a search for prospective biomarkers is most likely to be fruitful in samples from that region. © The Meteoritical Society, 2007. 2007 10.1111/j.1945-5100.2007.tb00220.x Meteoritics and Planetary Science 42 93-112 Lunar Planetary Laboratory, The University of Arizona, 1629 East University Boulevard, Tucson, AZ 85721-0092, United States; Department of Space Studies, Southwest Research Institute, 1050 Walnut Street, Boulder, CO 80302, United States; Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, TX 77058, United States 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846436763&doi=10.1111%2fj.1945-5100.2007.tb00220.x&partnerID=40&md5=ca89f6d57dcbb831e13edce5136ebf7f cited By 78 O. Abramov D.A. Kring article Kring20074 An impact-mass extinction hypothesis for the Cretaceous-Tertiary (K/T) boundary transition has been confirmed with multiple lines of evidence, beginning with the discovery of impact-derived Ir in K/T boundary sediments and culminating in the discovery of the Chicxulub impact crater. Likewise, a link between the Chicxulub impact crater and K/T boundary sediments has been confirmed with multiple lines of evidence, including stratigraphic, petrological, geochemical, and isotopic data. The environmental effects of the Chicxulub impact event were global in their extent, largely because of the interaction of ejected impact debris with the atmosphere. The environmental consequences of the Chicxulub impact event and their association with the K/T boundary mass extinction event indicate that impact cratering processes can affect both the geologic and biologic evolution of our planet. © 2007 Elsevier B.V. All rights reserved. 2007 10.1016/j.palaeo.2007.02.037 Palaeogeography, Palaeoclimatology, Palaeoecology 255 4-21 Lunar and Planetary Laboratory, Department of Geosciences, The University of Arizona, Tucson, AZ 85721, United States 1-2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-34948856485&doi=10.1016%2fj.palaeo.2007.02.037&partnerID=40&md5=637be1308034a8f641227ac4a9f9ee0a cited By 161 D.A. Kring article Osinski20071 Despite being present in the target sequence of ∼70% of the world's known impact structures, the response of sedimentary rocks to hypervelocity impact remains poorly understood. Of particular significance is the relative importance and role of impact melting versus decomposition in carbonate and sulfate lithologies. In this work, we review experimental evidence and phase equilibria and synthesize these data with observations from studies of naturally shocked rocks from several terrestrial impact sites. Shock experiments on carbonates and sulfates currently provide contrasting and ambiguous results. Studies of naturally shocked materials indicate that impact melting is much more common in sedimentary rocks than previously thought. This is in agreement with the phase relations for calcite. A summary of the criteria for the recognition of impact melts derived from sedimentary rocks is presented, and it is hoped that this will stimulate further studies of impact structures in sedimentary target rocks. This assessment leads us to conclude that impact melting is common during hypervelocity impact into both crystalline and sedimentary rocks. However, the products are texturally and chemically distinct, which has led to much confusion in the past, particularly in terms of the recognition of impact melts derived from sedimentary rocks. © 2008 The Geological Society of America. All rights reserved. 2007 10.1130/2008.2437(01) Special Paper of the Geological Society of America 437 1-18 Department of Earth Sciences/Physics and Astronomy, University of Western Ontario, London, ON N6A 5B7, Canada; Planetary and Space Science Centre, Department of Geology, University of New Brunswick, 2 Bailey Drive, Fredericton, NB E3B 5A3, Canada; Earth Sciences Sector, Natural Resources Canada, Ottawa, ON K1A 0E4, Canada https://www.scopus.com/inward/record.uri?eid=2-s2.0-75749106193&doi=10.1130%2f2008.2437%2801%29&partnerID=40&md5=171f0209e8e261b9b240cc1b5933c7c1 cited By 41 G.R. Osinski J.G. Spray R.A.F. Grieve article Petersen2007655 Drill-core samples from the Bosumtwi impact structure (1.07 Myr old and 10.5 km in diameter) in Ghana exhibit mineralogical evidence for post-impact hydrothermal alteration. Nine samples of drill core obtained through the 2004 International Continental Scientific Drilling Project (ICDP) were studied, including an uppermost fallback layer overlying impactite breccias, and partly deformed massive meta-graywacke bedrock. The petrographic study revealed alteration veins containing secondary sericitic muscovite (comparable to 2M1-muscovite) crosscutting original bedding in meta-graywacke and forming a matrix between clasts in impactite breccias. X-ray diffraction (XRD) shows that these impactite samples are rich in 2M1-muscovite, consistent with post-impact fluid deposition and alteration. Optical analysis indicates the presence of a pre-impact stratiform chlorite in meta-graywacke samples and a secondary alteration chlorite occurring in all samples. Secondary illite was detected in upper impactites of drill core LB-08A and samples containing accretionary lapilli. The lower temperature constraint for the hydrothermal event is given by 2M1-muscovite, secondary chlorite, and illite, all of which form at temperatures greater than 280 °C. An absence of recrystallization of quartz and feldspar indicates an upper temperature constraint below 900 °C. The presence of alteration materials associated with fractures and veins in the uppermost impactites of drill cores LB-07A and LB-08A indicates that a post-impact hydrothermal system was present in and adjacent to the central uplift portion of the Bosumtwi impact structure. A sample containing accretionary lapilli obtained from drill core LB-05A exhibits limited evidence that hydrothermal processes were more widespread within the impactites on the crater floor. © The Meteoritical Society, 2007. Printed in USA. 2007 10.1111/j.1945-5100.2007.tb01066.x Meteoritics and Planetary Science 42 655-666 Institute of Meteoritics, University of New Mexico, Albuquerque, NM 87131, United States; Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131, United States 4-5 https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250666647&doi=10.1111%2fj.1945-5100.2007.tb01066.x&partnerID=40&md5=e3ee7ec17b4aa211974e2983ae696398 cited By 8 M.T. Petersen H.E. Newsom M.J. Nelson D.M. Moore article Coney2007667 In 2004, a drilling project by the International Continental Scientific Drilling Program (ICDP) at the Bosumtwi impact crater, Ghana (1.07 Myr old and 10.5 km in diameter), obtained drill core LB-07A, which sampled impactites and underlying metasediments in the crater moat surrounding the small central uplift of the structure. The LB-07A core consists of three sequences: 82.29 m of an upper impactite sequence of alternating polymict lithic and suevitic impact breccias overlying 54.88 m of so-called lower impactite of monomict impact breccia with several suevite intercalations, and 74.53 m of meta-graywacke and altered shale of the basement, also containing a number of suevite intercalations. Major- and trace-element characteristics of all three sequences have been determined to investigate breccia formation and the role of the respective basement lithologies therein. Compositions of polymict impact breccias of the crater fill revealed by core LB-07A are compared with the compositions of the Ivory Coast tektites and the fallout suevites. The impactites of the LB-07A borehole appear well homogenized with respect to the silicate component, and little change in the ranges of many major- and trace-element differences is seen along the length of the borehole (except for Fe2O3, MgO, and CaO contents). Much scatter is observed for a number of elements, and in many cases this increases with depth. It is proposed that any variability in composition is likely the function of clast population differences (i.e., also of relatively small sample sizes). No systematic compositional difference between polymict lithic and suevitic impact breccias is evident. An indication of carbonate enrichment due to hydrothermal alteration is observed in samples from all lithologies. The impactites of the borehole generally show intermediate compositions to previously defined target rocks. The fallout suevites have comparable major element abundances, except for relatively lower MgO contents. The Ivory Coast tektites are generally similar in composition to the LB-07A suevites, but broader ranges in MgO and CaO contents are observed for the LB-07A suevites. © The Meteoritical Society, 2007. Printed in USA. 2007 10.1111/j.1945-5100.2007.tb01067.x Meteoritics and Planetary Science 42 667-688 Impact Cratering Research Group, School of Geosciences, University of the Witwatersrand, Private Bag 3, Johannesburg 2050, South Africa; Museum for Natural History, Department of Mineralogy, Humboldt University Berlin, Invalidenstrasse 43, D-10115 Berlin, Germany; Department of Geological Sciences, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria 4-5 https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250612631&doi=10.1111%2fj.1945-5100.2007.tb01067.x&partnerID=40&md5=d88eb0e070deddf53b50a3f762008eb4 cited By 17 L. Coney W.U. Reimold R.L. Gibson C. Koeberl book Ivanov2007207 To use the information about impact craters on terrestrial planets for study of planetary geology and geophysics, one should combine a wide set of processes and parameters. The chapter presents a review of impact cratering processes, estimates of average impact velocities, and impact probability for terrestrial planets. Basics of the impact crater scaling is discussed to present to date level of confidence in problems, where one needs to correlate measured size of an impact crater and mass and size of a body, created the impact structure. Scaling laws for large impact crates are discussed in comparison with results of the direct numerical modeling of impact cratering. The accumulation rate for impact craters on terrestrial planets is believed to be constant (within a factor of 2) during the last ∼3 Ga of the solar system history. Measuring the number of accumulated craters of a given size in the area of interest, one can estimate relative age of the visible surface, provided the older surfaces accumulate larger number of craters. In connection with this technique measured size-frequency distribution of impact craters is discussed, including the now widely disputable topic of secondary cratering, preventing the simple interpretation of cratering record for small craters. © 2007 Elsevier B.V. All rights reserved. 2007 10.1016/B978-044452748-6.00158-9 Treatise on Geophysics 10 207-242 Institute for Dynamics of Geospheres, Moscow, Russian Federation; Planetary Science Institute, Tucson AZ, United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-61849115344&doi=10.1016%2fB978-044452748-6.00158-9&partnerID=40&md5=82b1fc1d827959e7cb976afde09568fa cited By 29 B.A. Ivanov W.K. Hartmann article deNiem2007900 In this work the meteorite and target mass partition into high-speed ejecta during the formation of terrestrial impact craters is investigated. Multi-material hydrocode calculations are carried out through the entire excavation phase, and the mass of each material moving upwards with velocities inside a range of intervals is obtained. Impact of a 10 km diameter stony asteroid with 20 km s- 1 into the continental crust is compared for the cases of a single layer of granite, taken to be representative for the crust, and of a two-layer crust with a 3 km thick sedimentary cover of limestone on top of granite basement, more appropriate for the Chicxulub crater. The proportion of meteorite and crustal material in high-speed ejecta is found as a function of velocity and time, and maximum distances to the crater can be estimated. The resulting distal (&gt; 7000 km) ejecta mass for vertical impact is less than a percent of the impactor mass, assuming ballistic transport. Simulations of oceanic impact of a 1 km-sized stony asteroid into 5.5 km deep sea are also presented. Here, ejection of meteorite material initially is delayed, but finally it leaves the ocean in a cloud of steam and water. The velocities of meteorite material are much lower compared with the continental impact, insufficient to reach large distances on ballistic trajectories. © 2007 Elsevier Ltd. All rights reserved. 2007 10.1016/j.pss.2006.12.002 Planetary and Space Science 55 900-914 Institute of Planetary Research, German Aerospace Center, Rutherford Str. 2, D-12489 Berlin, Germany; Institute of Theoretical Physics, Technical University of Braunschweig, Mendelssohnstr. 3, D-38106 Braunschweig, Germany 7-8 https://www.scopus.com/inward/record.uri?eid=2-s2.0-34247466021&doi=10.1016%2fj.pss.2006.12.002&partnerID=40&md5=36400b0feea59729e17598d5734c9801 cited By 2 D. Niem E. Kührt U. Motschmann book Koeberl200795 Currently about 170 impact craters are known on Earth; about one third of those structures are not exposed on the surface and can only be studied by geophysics or drilling. The impact origin of geological structures can only be confirmed by petrographic and geochemical studies; thus, it is of crucial importance to obtain samples of subsurface structures. In addition, structures that have surface exposures commonly require drilling and drill cores to obtain information of the subsurface structure, to provide ground-truth for geophysical studies, and to obtain samples of rock types not exposed at the surface. For many years, drilling of impact craters was rarely done in dedicated projects, mainly due to the high cost involved. Structures were most often drilled for reasons unrelated to their impact origin. In the former Soviet Union a number of impact structures were drilled for scientific reasons, but in most of these cases the curation and proper care of the cores was not guaranteed. More recently the International Continental Scientific Drilling Program (ICDP) has supported projects to study impact craters. The first ICDPsupported study of an impact structure was the drilling into the 200-kmdiameter, K-T boundary age, subsurface Chicxulub impact crater, Mexico, which occurred between December 2001 and February 2002. The core retrieved from the borehole Yaxcopoil-1, 60 km SSW from the center of the structure, reached a depth of 1511 m and intersected 100 m of impact melt breccia and suevite, which has been studied by an international team. From June to October 2004, the 10.5 km Bosumtwi crater, Ghana, was drilled within the framework of an ICDP project, to obtain a complete 1 million year paleoenvironmental record in an area for which only limited data exist, and to study the subsurface structure and crater fill of one of the best preserved large, young impact structures. From September to December 2005, the main part of another ICDP-funded drilling project was conducted, at the 85-km-diameter Chesapeake Bay impact structure, eastern USA, which involved drilling to a depth of 1.8 km. In 2008, it is likely that the El'ygytgyn structure (Arctic Russia) will be drilled as well. So far only few craters have been drilled - not enough to gain a broad understanding of impact crater formation processes and consequences. In this chapter we summarize the current status of scientific drilling at impact craters, and provide some guidance and suggestions about future drilling projects that are relevant for impact research. Points we cover include: what is the importance of studying impact craters and processes, why is it important to drill impact craters or impact crater lakes, which important questions can be answered by drilling, which craters would be good targets and why; is there anything about the impact process, or of impact relevance, that can be learned by drilling outside any craters; what goals should be set for the future; how important is collaboration between different scientific fields? In the following report, we first briefly discuss the importance of impact cratering, then summarize experience from past drilling projects (ICDP and others), and finally we try to look into the future of scientific drilling of impact structures. © 2007 Springer-Verlag Berlin Heidelberg. 2007 10.1007/978-3-540-68778-8_3 Continental Scientific Drilling: A Decade of Progress, and Challenges for the Future 95-161 Department of Geological Sciences, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria; Department of Physics, University of Toronto, 60 St. George Street, Toronto, ON M5S 1A7, Canada https://www.scopus.com/inward/record.uri?eid=2-s2.0-62849087451&doi=10.1007%2f978-3-540-68778-8_3&partnerID=40&md5=9355d072f6daf494807ad2d6383dc4f9 cited By 11 C. Koeberl B. Milkereit article Keller2007339 Multidisciplinary studies, including stratigraphy, sedimentology, mineralogy and geochemistry, of the new core Mullinax-1 and outcrops along the Brazos River and Cottonmouth Creek, Falls County, Texas, reveal the complex history of the Chicxulub impact, the event deposit and the K-T boundary event. The K-T boundary, as identified by the negative δ13C shift, first occurrence of Danian planktic foraminifera and palynomorphs occurs 80 cm above the event deposit in core Mullinax-1. The underlying 80 cm interval was deposited in a shallow low oxygen environment during the latest Maastrichtian, as indicated by high stress microfossil assemblages, small shells and burrows infilled with framboidal pyrite. The underlying event deposit, commonly interpreted as K-T impact tsunami, consists of a basal conglomerate with clasts containing Chicxulub impact spherules, repeated upward fining units of spherule-rich sands, followed by hummocky cross-bedded and laminated sands, which are burrowed by Thalassinoides, Planolites and Ophiomorpha and truncated by erosion. This suggests a series of temporally separated storm events with re-colonization of the ocean floor by invertebrates between storms, rather than a series of waning tsunami-generated waves. The lithified clasts with impact spherules at the base of the event deposit provide strong evidence that the Chicxulub impact ejecta layer predates the event deposit, but was eroded and re-deposited during the latest Maastrichtian sea level lowstand. The original Chicxulub ejecta layer was discovered in a 3 cm thick yellow clay layer interbedded in undisturbed late Maastrichtian clay- and mudstones 40 cm below the base of the event deposit and near the base of planktic foraminiferal zone CF1, which spans the last 300 kyr of the Maastrichtian. The yellow clay consists of cheto smectite derived from alteration of impact glass, as indicated by rare altered glass spherules with similar chemical compositions as reworked spherules from the event deposit and Chicxulub impact spherules from NE Mexico and Haiti. The Brazos sections thus provide strong evidence that the Chicxulub impact predates the K-T boundary by about 300 kyr, consistent with earlier observations in NE Mexico and the Chicxulub crater core Yaxcopoil-1. © 2007 Elsevier B.V. All rights reserved. 2007 10.1016/j.epsl.2006.12.026 Earth and Planetary Science Letters 255 339-356 Geosciences, Princeton University, Princeton, NJ 08540, United States; Geological Institute, University of Neuchatel, Neuchatel, CH-2007, Switzerland; Institute for Mineralogy and Geochemistry, University of Karlsruhe, 76128 Karlsruhe, Germany; Department of Earth Sciences, Utrecht University, Utrecht, Netherlands; Lewis Energy Group, 10101 Reunion Square, Suite 1000, San Antonio, TX 78216, United States; Free University Berlin, Institute for Geosciences, Section Paleontology, D-12249 Berlin, Germany; Geology Department, South Valley University, Asswan, Egypt 3-4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847333344&doi=10.1016%2fj.epsl.2006.12.026&partnerID=40&md5=d1dad90df4dd22a0ac1d942d151f6131 cited By 77 G. Keller T. Adatte Z. Berner M. Harting G. Baum M. Prauss A. Tantawy D. Stueben article Bottke200748 The terrestrial and lunar cratering rate is often assumed to have been nearly constant over the past 3 Gyr. Different lines of evidence, however, suggest that the impact flux from kilometre-sized bodies increased by at least a factor of two over the long-term average during the past ∼100 Myr. Here we argue that this apparent surge was triggered by the catastrophic disruption of the parent body of the asteroid Baptistina, which we infer was a ∼170-km-diameter body (carbonaceous-chondrite-like) that broke up Myr ago in the inner main asteroid belt. Fragments produced by the collision were slowly delivered by dynamical processes to orbits where they could strike the terrestrial planets. We find that this asteroid shower is the most likely source (>90 per cent probability) of the Chicxulub impactor that produced the Cretaceous/Tertiary (K/T) mass extinction event 65 Myr ago. ©2007 Nature Publishing Group. 2007 10.1038/nature06070 Nature 449 48-53 Southwest Research Institute, 1050 Walnut St, Boulder, CO 80302, United States; Institute of Astronomy, Charles University, V Holesovickach 2, 18000 Prague 8, Czech Republic 7158 https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548510857&doi=10.1038%2fnature06070&partnerID=40&md5=c8056b1d871dc5fef1d1e5cb54facc69 cited By 142 W.F. Bottke D. Vokrouhlický D. Nesvorný book Ivanov2007207 To use the information about impact craters on terrestrial planets for study of planetary geology and geophysics, one should combine a wide set of processes and parameters. The chapter presents a review of impact cratering processes, estimates of average impact velocities, and impact probability for terrestrial planets. Basics of the impact crater scaling is discussed to present to date level of confidence in problems, where one needs to correlate measured size of an impact crater and mass and size of a body, created the impact structure. Scaling laws for large impact crates are discussed in comparison with results of the direct numerical modeling of impact cratering. The accumulation rate for impact craters on terrestrial planets is believed to be constant (within a factor of 2) during the last ∼3 Ga of the solar system history. Measuring the number of accumulated craters of a given size in the area of interest, one can estimate relative age of the visible surface, provided the older surfaces accumulate larger number of craters. In connection with this technique measured size-frequency distribution of impact craters is discussed, including the now widely disputable topic of secondary cratering, preventing the simple interpretation of cratering record for small craters. © 2007 Elsevier B.V. All rights reserved. 2007 10.1016/B978-044452748-6.00158-9 Treatise on Geophysics: Volume 1-10 1-10 207-242 Institute for Dynamics of Geospheres, Moscow, Russian Federation; Planetary Science Institute, Tucson, AZ, United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-85146742339&doi=10.1016%2fB978-044452748-6.00158-9&partnerID=40&md5=ef83e1f3feb20b9c656e1635463e825f cited By 0 B.A. Ivanov W.K. Hartmann article Pati200781 Impact cratering is a geological process characterized by ultra-fast strain rates, which generates extreme shock pressure and shock temperature conditions on and just below planetary surfaces. Despite initial skepticism, this catastrophic process has now been widely accepted by geoscientists with respect to its importance in terrestrial - indeed, in planetary - evolution. About 175 impact structures have been discovered on Earth so far, and some more structures are considered to be of possible impact origin. One major extinction event, at the Cretaceous-Paleogene boundary, has been firmly linked with catastrophic impact, but whether other important extinction events in Earth history, including the so-called "Mother of All Mass Extinctions" at the Permian-Triassic boundary, were triggered by huge impact catastrophes is still hotly debated and a subject of ongoing research. There is a beneficial side to impact events as well, as some impact structures worldwide have been shown to contain significant (in some cases, world class) ore deposits, including the gold-uranium province of the Witwatersrand basin in South Africa, the enormous Ni and PGE deposits of the Sudbury structure in Canada, as well as important hydrocarbon resources, especially in North America. Impact cratering is not a process of the past, and it is mandatory to improve knowledge of the past-impact record on Earth to better constrain the probability of such events in the future. In addition, further improvement of our understanding of the physico-chemical and geological processes fundamental to the impact cratering process is required for reliable numerical modeling of the process, and also for the correlation of impact magnitude and environmental effects. Over the last few decades, impact cratering has steadily grown into an integrated discipline comprising most disciplines of the geosciences as well as planetary science, which has created positive spin-offs including the study of paleo-environments and paleo-climatology, or the important issue of life in extreme environments. And yet, in many parts of the world, the impact process is not yet part of the geoscience curriculum, and for this reason, it deserves to be actively promoted not only as a geoscientific discipline in its own right, but also as an important life-science discipline. 2007 10.1007/s12040-007-0009-3 Journal of Earth System Science 116 81-98 Department of Earth and Planetary Sciences, Nehru Science Centre, University of Allahabad, Allahabad 211 002, India; Museum f. Natural History (Mineralogy), Humboldt-University in Berlin, Invalidenstrasse 43, D-10115 Berlin, Germany 2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-34247367579&doi=10.1007%2fs12040-007-0009-3&partnerID=40&md5=22769c24efd84e321553edd29fa7f4c3 cited By 22 J.K. Pati W.U. Reimold article Lefticariu200651 The Chicxulub Sedimentary Basin of the northwestern Yucatan Peninsula, Mexico, which was formed because of the largest identified Phanerozoic bolide impact on Earth, became a site of deposition of dominantly marine carbonate sediments during most of the Cenozoic Era. This is a study of the filling and diagenetic history of this basin and surrounding areas. The study makes use of lithologic, biostratigraphic, petrographic, and geochemical data obtained on core samples from boreholes drilled throughout the northwestern Yucatan Peninsula. The core sample data indicate that: 1) The Chicxulub Sedimentary Basin concentrated the deposition of pelagic and outer-platform sediments during the Paleocene and Eocene, and, in places, during the Early Oligocene, as well, and filled during the Middle Miocene, 2) deeper-water limestone also is present within the Paleocene and Lower Eocene of the proposed Santa Elena Depression, which is located immediately south of the Basin, 3) shallow-water deposits are relatively more abundant outside the Basin and Depression than inside, 4) the autigenic and allogenic silicates from the Paleogene formations are the most abundant inside the Depression, 5) sediment deposition and diagenesis within the Basin also were controlled by impact crater topography, 6) the abundance of the possible features of subaerial exposure increases upward and outward from the center of the Basin, and 7) the formation of replacive low-magnesium calcite and dolomite, dedolomitization, dissolution, and precipitation of vug-filling calcite and dolomite cement have been more common outside the Basin than inside. δ18O in whole-rock (excluding vug-filling) calcite from core samples ranges from -7.14‰ to + 0.85‰ PDB. δ13C varies from -6.92‰ to +3.30‰ PDB. Both stable isotopes correlate inversely with the abundance of subaerial exposure features indicating that freshwater diagenesis has been extensive especially outside and at the edge of the Chicxulub Sedimentary Basin. δ18O and δ13C in w hole-rock (excluding vug-filling) dolomite ranges from -5.54‰ to +0.87‰ PDB and -4.63‰ to +3.38‰ PDB, respectively. Most dolomite samples have negative δ18O and positive δ13C suggesting that replacive dolomitization involved the presence of a fluid dominated by freshwater and/or an anomalously high geothermal gradient. Most dolomite XRD-determined mole percent CaCO3 varies between 51 and 56. Replacive dolomite is larger, more euhedral, and less stoichiometric inside the Chicxulub Sedimentary Basin than outside. © 2005 Elsevier B.V. All rights reserved. 2006 10.1016/j.sedgeo.2005.09.008 Sedimentary Geology 183 51-69 Northern Illinois University, Department of Geology and Environmental Geosciences, DeKalb, IL 60115, United States; University of New Orleans, Department of Geology and Geophysics, New Orleans, LA 70148, United States; Indiana University Bloomington, Department of Geological Sciences, Bloomington, IN 47405, United States; TTL Associates Inc., 1916 N12th Street, Toledo, OH 43624, United States 1-2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-29844451829&doi=10.1016%2fj.sedgeo.2005.09.008&partnerID=40&md5=44cc05603534b7db962fc79736335c6c cited By 25 M. Lefticariu E.C. Perry W.C. Ward L. Lefticariu article Schulte200677 Two cores from Brazos, Texas, spanning the Cretaceous-Paleogene (K-P) boundary, are investigated by a multidisciplinary approach aiming at unraveling environmental changes and sequence stratigraphic setting. In addition, the sedimentology of the K-P event deposit and its correlation with the K-P boundary is studied. Foraminifera and nannofossil stratigraphy indicates that both cores include a latest Maastrichtian (Zone CF1-CF2) and earliest Danian (P0, Pα and P1a) shale sequence with a sandy and Chicxulub ejecta-bearing event deposit at the K-P boundary; a hiatus of unknown duration may be present by the unconformable base of the event deposit. Planktic foraminifera as well as calcareous nannofossil abundance and diversity both decline abruptly above the event deposit (K-P mass extinction), whereas benthic foraminifera show a pronounced faunal change but no mass extinction. Mineralogical and geochemical proxies suggest that-except for the sandwiched K-P event deposit-no facies change took place across the K-P boundary and no evidence for adverse an- or dysoxic sedimentary conditions following the Chicxulub impact was observed. Therefore, the interval bracketing the K-P event deposit is considered as highstand systems tract. Increased coarse detritus input and low planktic/benthic (P/B) foraminifera ratios during the earliest Paleocene (P0 and Pα) both suggest an increased coastal proximity or relative sea-level lowering, although the K-P mass extinction of planktic foraminifera might have influenced the P/B ratios as well. Consequently, the sandy shales of the early Paleocene are considered as late regressive highstand or as lowstand deposit. During P1a, shales assigned as transgressive systems tract overlie a pyrite- and glauconite-rich bioturbated transgressive surface or type-2-sequence boundary. The smectite-dominated clay assemblage, with minor illite, kaolinite and chlorite indicates semiarid-humid climates with no obvious shifts across the K-P boundary. The magnetic susceptibility signature during the Maastrichtian reveals a subtle cyclic (or rhythmic) pattern, whereas a high-amplitude cyclic pattern is present during the early Danian. The K-P event deposit shows a succession of high-energetic debris flows and turbidites derived from multiple source areas, followed by a period of decreasing current energy. Deposition was likely triggered by multiple tsunami or tempestites followed by a prolonged period of reworking and settling. The Chicxulub ejecta at the base of the K-P event deposit consists of Mg-rich smectite-as well as Fe-Mg-rich chlorite-spherules. Their mineralogical composition points to target rocks of mafic to intermediate composition, presumably situated in the northwestern sector of the Chicxulub impact structure. Besides these silicic phases, the most prominent ejecta components are limestone clasts, accretionary carbonate clasts, and microspar, suggesting that the Texas area received ejecta also from shallow, carbonate-rich lithologies at the impact site on the Yucatán carbonate platform. The excellent correlation of Chicxulub ejecta at Brazos with ejecta found in the K-P boundary layer worldwide - along with the associated mass extinction - provides no evidence that Chicxulub predated the K-P boundary and allows for unequivocal positioning of the K-P boundary at the event deposit. © 2005 Elsevier B.V. All rights reserved. 2006 10.1016/j.sedgeo.2005.09.021 Sedimentary Geology 184 77-109 Institut für Geologie und Mineralogie, Universität Erlangen-Nürnberg, Schloßgarten 5, D-91054 Erlangen, Germany; Department of Geography and Geology, KU Leuven, Redingenstraat 16, B-3000 Leuven, Belgium; Fachbereich 5 Geowissenschaften, Universität Bremen, Postfach 330440, D-28334 Bremen, Germany; Geologisch-Paläontologisches Institut, Universität Heidelberg, Im Neuenheimer Feld 234, D-69120 Heidelberg, Germany 1-2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-30544436024&doi=10.1016%2fj.sedgeo.2005.09.021&partnerID=40&md5=ae84c8ae9b470412e3317b98474a2db2 cited By 80 P. Schulte R. Speijer H. Mai A. Kontny article Kenkmann200615 Subhorizontal shear planes (detachments) are observed in bedded limestones in the periphery of the Ries impact crater, Germany. These detachments occur at 0.8-1.8 crater radii distance from the crater center beneath deposits of the continuous ejecta blanket. Striations on detachment planes and offsets of markers indicate top-outward shearing with radial slip vectors. Detachments were found at depths between a few meters and more than 50 m beneath the target surface. The displacements along these faults range from meters to decameters and decrease with increasing depth and distance from the crater center. With increasing crater distance, detachment horizons tend to climb to shallower levels. Cross-cutting relationships to faults associated with the crater collapse indicate that detachment faulting started prior to the collapse but continued during crater modification. Numerical modeling of the cratering process shows that near-surface deformation outside the transient crater is induced by two separate mechanisms: (i) weak spallation by interference of shock and release waves near the target surface and (ii) subsequent dragging by the deposition of the ejecta curtain. Spallation causes an upward and outward directed motion of target material that increases in magnitude toward the target surface. It leads to decoupling of the uppermost target layers in the early cratering stage without totally disintegrating the rock. The subsequent arrival of the oblique impact shower of the ejecta curtain at the target surface delivers a horizontal momentum to the uppermost target area and results in a second horizontal displacement increment by dragging. With increasing depth this effect vanishes rapidly. Spallation decoupling and subsequent ejecta dragging of near-surface rocks is probably a general cratering mechanism around craters in layered targets with weak interbeds. © 2006 Elsevier B.V. All rights reserved. 2006 10.1016/j.epsl.2006.08.024 Earth and Planetary Science Letters 252 15-29 Museum of Natural History-Mineralogy, Humboldt-University Berlin, Invalidenstrasse 43, D-10115 Berlin, Germany; Institute for Geodynamics and Geospheres, Russian Academy of Science, Leninsky Prospect, 38, 119334 Moscow, Russian Federation 1-2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750974452&doi=10.1016%2fj.epsl.2006.08.024&partnerID=40&md5=0f33c623b6d4da912e5a54b0ff9f9698 cited By 30 T. Kenkmann B.A. Ivanov article Wittmann2006433 To ascertain the progressive stages of shock metamorphism of zircon, samples from three well-studied impact craters were analyzed by optical microscopy, scanning electron microscopy (SEM), and Raman spectroscopy in thin section and grain separates. These samples are comprised of well-preserved, rapidly quenched impactites from the Ries crater, Germany, strongly annealed impactites from the Popigai crater, Siberia, and altered, variably quenched impactites from the Chicxulub crater, Mexico. The natural samples were compared with samples of experimentally shock-metamorphosed zircon. Below 20 GPa, zircon exhibits no distinct shock features. Above 20 GPa, optically resolvable planar microstructures occur together with the high-pressure polymorph reidite, which was only retained in the Ries samples. Decomposition of zircon to ZrO2 only occurs in shock stage IV melt fragments that were rapidly quenched. This is not only a result of post-shock temperatures in excess of ∼1700 °C but could also be shock pressure-induced, which is indicated by possible relics of a high-pressure polymorph of ZrO2. However, ZrO2 was found to revert to zircon with a granular texture during devitrification of impact melts. Other granular textures represent recrystallized amorphous ZrSiO4 and reidite that reverted to zircon. This requires annealing temperatures &gt;1100 °C. A systematic study of zircons from a continuous impactite sequence of the Chicxulub impact structure yields implications for the post-shock temperature history of suevite-like rocks until cooling below ∼600 °C. © The Meteoritical Society, 2006. 2006 10.1111/j.1945-5100.2006.tb00472.x Meteoritics and Planetary Science 41 433-454 Institut für Mineralogie, Museum für Naturkunde, Humboldt Universität zu Berlin, Invalidenstrasse 43, 10115 Berlin, Germany 3 https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646128493&doi=10.1111%2fj.1945-5100.2006.tb00472.x&partnerID=40&md5=1f310cdafabe6c7a667799c9e01ebc27 cited By 131 A. Wittmann T. Kenkmann R.T. Schmitt D. Stöffler article ElwoodMadden2006247 This study examines the effects of shock metamorphism on fluid inclusions in crystalline basement target rocks from the Ries crater, Germany. The occurrence of two-phase fluid inclusions decreases from shock stage 0 to shock stage 1, while single-phase inclusions increase, likely as a result of re-equilibration. In shock stages 2 and 3, both two-phase and single-phase inclusions decrease with increasing shock stage, indicating that fluid inclusion vesicles are destroyed due to plastic deformation and phase changes in the host minerals. However, quartz clasts entrained in shock stage 4 melts contain both single-phase and two-phase inclusions, demonstrating the rapid quenching of the melt and the heterogeneous nature of impact deformation. Inclusions in naturally shocked polycrystalline samples survive at higher shock pressures than those in single crystal shock experiments. However, fluid inclusions in both experimental and natural samples follow a similar trend in re-equilibration at low to moderate shock pressures leading to destruction of inclusion vesicles in higher shock stages. This suggests that shock processing may lead to the destruction of fluid inclusions in many planetary materials and likely contributed to shock devolatilization of early planetesimals. © The Meteoritical Society, 2006. 2006 10.1111/j.1945-5100.2006.tb00208.x Meteoritics and Planetary Science 41 247-262 Department of Geosciences, Virginia Polytechnic Institute, Blacksburg, VA 24060, United States; Lunar and Planetary Laboratory, The University of Arizona, Tucson, AZ 85721, United States; Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6036, United States 2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-33645468128&doi=10.1111%2fj.1945-5100.2006.tb00208.x&partnerID=40&md5=6a2dff61c05b11df647ca70b3674a005 cited By 3 M.E. Elwood Madden D.A. Kring R.J. Bodnar article Martinez-Ruiz20061 The Chicxulub impact event led to a worldwide deposition of impact materials originated from target rocks and the vaporized bolide. Relative contributions of both types of material to the K/T ejecta deposits vary with distance to the crater site. At distal sites (e.g., Agost and Caravaca in the SE of Spain) a major contribution of extraterrestrial material is indicated by different impact signatures, such as Os and Cr isotope composition, abundant microkrystites, platinum group elements and other siderophile elements that are typical of extraterrestrial components. Closer settings to the Chicxulub crater, for example the Blake Nose Plateau in the North American margin, display major continental crustal rock contributions in the ejecta layer. REE compositions provide additional evidence for terrestrial vs. extraterrestrial rock contributions. Previous research has not focused specifically on REE concentrations and corresponding C1- and NASC-normalized patterns. However, normalized REE patterns are already generating supplementary insights into the nature of the original material of the K/T boundary layer. Thus, Blake Nose ejecta C1-normalized patterns indicate a derivation from continental crustal target rocks. In more distal sections REE compositions point to a probable mafic precursor and confirm that extraterrestrial materials represent a major contribution the ejecta layer. © 2006 Elsevier B.V. All rights reserved. 2006 10.1016/j.chemgeo.2006.02.013 Chemical Geology 232 1-11 Instituto Andaluz de Ciencias de la Tierra, CSIC - Universidad de Granada, Facultad de Ciencias, Avda. Fuentenueva, s/n, 18002 Granada, Spain; Departamento de Mineralogía y Petrología, Facultad de Ciencias, Universidad de Granada, Avda. Fuentenueva, s/n, 18002 Granada, Spain; Centro Andaluz de Medio Ambiente (CEAMA), Junta de Andalucía - Universidad de Granada, Avda. del Mediterráneo, s/n, 18006 Granada, Spain 1-2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746415305&doi=10.1016%2fj.chemgeo.2006.02.013&partnerID=40&md5=86cae94e481c26ba05cf75e658a1bc73 cited By 16 F. Martínez-Ruiz M. Ortega-Huertas P. Rivas article Newsom20061929 The concentrations of the fluid mobile trace elements lithium, beryllium, boron, and barium were measured in samples of the altered matrix of several impactite breccias of the Yaxcopoil-1 drill core using secondary ion mass spectrometry (SIMS) to determine the extent of transport due to aqueous or hydrothermal processes. Three of the elements, Li, Be, and B, have higher concentrations in the upper suevite impact breccias than in the lower impact melt deposits by factors of 3.5, 2.2, and 1.5, respectively. Lithium and B are the most enriched elements up section, and appear to have had the greatest mobility. The similar fractionation of Li and B is consistent with fluid transport and alteration under low-temperature conditions of less than 150 °C based on published experimental studies. In contrast to Li, Be, and B, the concentration of Ba in the altered matrix materials decreases upward in the section, and the concentration of Ba in the matrix is an order of magnitude less than the bulk concentrations, likely due to the presence of barite. The origin of the elemental variations with depth may be related to different protolith compositions in the upper versus the lower impactite units. A different protolith in the altered matrix is suggested by the Mg-rich composition of the tower units versus the Al-rich composition of the upper units, which largely correlates with the mobile element variations. The possibility that vertical transport of mobile elements is due to a postimpact hydrothermal system is supported by published data showing that the sediments immediately overlying the impactites are enriched in mobile elements derived from a hydrothermal system. However, the mobile elements in the sediments do not have to originate from the underlying impactites. In conclusion, our data suggests that the impactites at this location did not experience extensive high-temperature hydrothermal processing, and that only limited transport of some elements, including Li, Be, and B, occurred. © The Meteoritical Society, 2006. 2006 10.1111/j.1945-5100.2006.tb00461.x Meteoritics and Planetary Science 41 1929-1945 Institute of Meteoritics, Department of Earth and Planetary Sciences, Albuquerque, NM 87131, United States; 5481 Oceanview Terrace, Nanaimo, BC V9V 1G7, Canada 12 https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846096690&doi=10.1111%2fj.1945-5100.2006.tb00461.x&partnerID=40&md5=13dc09879add2395bfe3ecc1d11de3b5 cited By 6 H.E. Newsom M.J. Nelson C.K. Shearer B.O. Dressler article Morgan2006264 The precise cause and timing of the Cretaceous-Paleocene (K-P) mass extinction 65 Ma ago remains a matter of debate. Many advocate that the extinction was caused by a meteorite impact at Chicxulub, Mexico, and a number of potential kill-mechanisms have been proposed for this. Although we now have good constraints on the size of this impact and chemistry of the target rocks, estimates of its environmental consequences are hindered by a lack of knowledge about the obliquity of this impact. An oblique impact is likely to have been far more catastrophic than a sub-vertical one, because greater volumes of volatiles would have been released into the atmosphere. The principal purpose of this study was to characterize shocked quartz within distal K-P ejecta, to investigate whether the quartz distribution carried a signature of the direction and angle of impact. Our analyses show that the total number, maximum and average size of shocked quartz grains all decrease gradually with paleodistance from Chicxulub. We do not find particularly high abundances in Pacific sites relative to Atlantic and European sites, as has been previously reported, and the size-distribution around Chicxulub is relatively symmetric. Ejecta samples at any one site display features that are indicative of a wide range of shock pressures, but the mean degree of shock increases with paleodistance. These shock- and size-distributions are both consistent with the K-P layer having been formed by a single impact at Chicxulub. One site in the South Atlantic contains quartz indicating an anomalously high average shock degree, that may be indicative of an oblique impact with an uprange direction to the southeast ± 45°. The apparent continuous coverage of proximal ejecta in this quadrant of the crater, however, suggests a relatively high impact angle of > 45°. We conclude that some of the more extreme predictions of the environmental consequences of a low-angle impact at Chicxulub are probably not applicable. © 2006 Elsevier B.V. All rights reserved. 2006 10.1016/j.epsl.2006.09.009 Earth and Planetary Science Letters 251 264-279 Earth Science and Engineering, Imperial College London, South Kensington Campus, SW7 2AZ London, United Kingdom; Department of Mineralogy, The Nature History Museum, Cromwell Road, SW7 5BD London, United Kingdom; Department of Geology, Royal Holloway University of London, Egham, TW20 0EX, United Kingdom; Osservatorio Geologico di Coldigioco, 62020 Frontale di Apiro, Italy; Geological Survey of Spain (IGME), Calera 1, Tres Cantos, 28760 Madrid, Spain; Departamento de Geologia, Universidade Federal de Pernambuco, 50.740-530 Recife, PEI, Brazil 3-4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750496928&doi=10.1016%2fj.epsl.2006.09.009&partnerID=40&md5=c9217c3990a34da1399a481d4e5ad191 cited By 51 J. Morgan C. Lana A. Kearsley B. Coles C. Belcher S. Montanari E. Díaz-Martínez A. Barbosa V. Neumann article Rebolledo-Vieyra20061309 We report on the magnetostratigraphy of the Chicxulub crater impact breccias and first 15 meters of the Paleocene sedimentary sequence recovered in three boreholes of the UNAM Scientific Drilling Program. Three geomagnetic polarity zones are documented in the impact breccias and sedimentary sequence, which span from chron 29R to 28N. For the 15 m interval they represent~2.5 Ma, which yields low apparent sedimentary rates for boreholes UNAM-5 (110 km from the center of the crater) and UNAM-7 (127 km from the center of the crater). The carbonate sedimentary sequence can be associated to a shallow basin depositional environment. In these boreholes the thickness between the 29R and the 29N chrons is just 0.5 m, suggesting that during the 100 ka from the K/T boundary to the polarity transition sediments were not deposited or eroded. Within borehole UNAM-6 (152 km from the center of the crater) it appears that sediments containing chron 29N are missing, the lack of the upper breccias, the long duration of a reversal event within the base of the sequence and low apparent sedimentary rate of 3.3 m/Ma, suggests a hiatus within the impact breccias and the basal Paleocene sedimentary sequence. Magnetic susceptibility logs confirm absence of the upper breccias at UNAM-6 borehole. Magnetic susceptibility values increase towards the base of the sequence, suggesting that basement and melt clasts were subjected to a low temperature hydrothermal alteration. © 2006, The Seismological Society of Japan, Society of Geomagnetism and Earth, Planetary and Space Sciences, The Volcanological Society of Japan, The Geodetic Society of Japan, The Japanese Society for Planetary Sciences. All rights reserved. 2006 10.1186/BF03352626 earth, planets and space 58 1309-1314 Laboratorio de Paleomagnetismo, Instituto de Geofisica, UNAM, Circuito Exterior SIN, Coyoacan, Mexico 10 https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846072659&doi=10.1186%2fBF03352626&partnerID=40&md5=61a56c41e1903c93fb34d47e0225a9db cited By 15 M. Rebolledo-Vieyra J. Urrutia-Fucugauchi article Tagle20061721 The three major geochemical methods for impactor identification are evaluated with respect to their potential and limitations with regards to the precise detection and identification of meteoritic material in impactites. The identification of a projectile component in impactites can be achieved by determining certain isotopic and elemental ratios in contaminated impactites. The isotopic methods are based on Os and Cr isotopic ratios. Osmium isotopes are highly sensitive for the detection of minute amounts of extraterrestrial components of even ≪0.05 wt% in impactites. However, this only holds true for target lithologies with almost no chemical signature of mantle material or young mantle-derived mafic rocks. Furthermore, this method is not currently suitable for the precise identification of the projectile type. The Cr-isotopic method requires the relatively highest projectile contamination (several wt%) in order to detect an extraterrestrial component, but may allow the identification of three different groups of extraterrestrial materials, ordinary chondrites, an enstatite chondrites, and differentiated achondrites. A significant advantage of this method is its independence of the target lithology and post-impact alteration. The use of elemental ratios, including platinum group elements (PGE: Os, Ir, Ru, Pt, Rh, Pd), in combination with Ni and Cr represents a very powerful method for the detection and identification of projectiles in terrestrial and lunar impactites. For most projectile types, this method is almost independent of the target composition, especially if PGE ratios are considered. This holds true even in cases of terrestrial target lithologies with a high component of upper mantle material. The identification of the projectile is achieved by comparison of the "projectile elemental ratio" derived from the slope of the mixing line (target-projectile) with the elemental ratio in the different types of possible projectiles (e.g., chondrites). However, this requires a set of impactite samples of various degree of projectile contamination. © The Meteoritical Society, 2006. 2006 10.1111/j.1945-5100.2006.tb00448.x Meteoritics and Planetary Science 41 1721-1735 Department of Geology, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium; Museum für Naturkunde Mineralogie, Humboldt-Universität zu Berlin, D-10099 Berlin, Germany 11 https://www.scopus.com/inward/record.uri?eid=2-s2.0-33751372115&doi=10.1111%2fj.1945-5100.2006.tb00448.x&partnerID=40&md5=fa8b9cfe110d653fd7ee7f98171772fa cited By 69 R. Tagle L. Hecht article Maier2006203 Meteorites provide a sample of Solar System bodies and so constrain the types of objects that have collided with Earth over time. Meteorites analysed to date, however, are unlikely to be representative of the entire population and it is also possible that changes in their nature have occurred with time 1. Large objects are widely believed to be completely melted or vaporized during high-angle impact with the Earth2,3. Consequently, identification of large impactors relies on indirect chemical tracers, notably the platinum-group elements4. Here we report the discovery of a large (25-cm), unaltered, fossil meteorite, and several smaller fragments within the impact melt of the giant (&gt;70 km diameter), 145-Myr-old Morokweng crater, South Africa. The large fragment (clast) resembles an LL6 chondrite breccia, but contains anomalously iron-rich silicates, Fe-Ni sulphides, and no troilite or metal. It has chondritic chromium isotope ratios and identical platinum-group element ratios to the bulk impact melt. These features allow the unambiguous characterization of an impactor at a large crater. Furthermore, the unusual composition of the meteorite suggests that the Morokweng asteroid incorporated part of the LL chondrite parent body not represented by objects at present reaching the Earth. © 2006 Nature Publishing Group. 2006 10.1038/nature04751 Nature 441 203-206 Sciences de la Terre, Université du Québec À Chicoutimi, Chicoutimi, Que. G7H 2B1, Canada; Department of Geology, University of Pretoria, Pretoria 0002, South Africa; South African Nuclear Energy Corporation, Pretoria 0001, South Africa; School of Geosciences, University of the Witwatersrand, Wits 2050, South Africa; School of Earth, Ocean and Planetary Sciences, Cardiff University, Cardiff CF10 3YE, United Kingdom; Scottish Universities Environmental Research Centre, East Kilbride G75 0QF, United Kingdom; Scripps Institution of Oceanography, University of California, San Diego, San Diego, CA 92093, United States; Department of Geological Sciences, Indiana University, Bloomington, IN 47405-7000, United States; Ithemba LABS - Gauteng, Wits 2050, South Africa 7090 https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646550544&doi=10.1038%2fnature04751&partnerID=40&md5=9fe684fb82fdf13a7278b4f59032bdbb cited By 62 W.D. Maier M.A.G. Andreoli I. Mcdonald M.D. Higgins A.J. Boyce A. Shukolyukov G.W. Lugmair L.D. Ashwal P. Gräser E.M. Ripley R.J. Hart article Stöffler2006519 2006 10.2138/rmg.2006.60.05 Reviews in Mineralogy and Geochemistry 60 519-596 Institut für Mineralogie, Museum für Naturkunde, Humboldt Universität zu Berlin, Invalidenstrasse 43, 10099 Berlin, Germany; Lunar and Planetary Institute, 3600 Bay Area Blvd., Houston, TX 77058, United States; Institute for Dynamics of Geospheres, Leninsky Prospect 38 Bldg. 1, 119334 Moscow, Russian Federation; NASA Johnson Space Center, Houston, TX 77058, United States; Natural Resources Canada, 588 Booth Street, Ottawa, Ont. K1A 0Y7, Canada https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745991997&doi=10.2138%2frmg.2006.60.05&partnerID=40&md5=b035aba5bf6ead8078d7ec7f8e3fff54 cited By 281 D. Stöffler G. Ryder B.A. Ivanov N.A. Artemieva M.J. Cintala R.A.F. Grieve article Arenillas2006241 High-resolution and quantitative planktic foraminiferal biostratigraphy from two SE Mexico stratigraphic sections (Bochil, Guayal) shows that the Chicxulub-related Complex Clastic Unit (CCU) is synchronous with the ejecta-rich airfall layer and the Cretaceous/Paleogene (K/Pg) catastrophic mass extinction horizon in the El Kef (Tunisia) and Caravaca (Spain) sections. The lowermost Danian H. holmdelensis subzone (= Biozone P0) was identified in both sections in a thin dark clay bed just above the CCU, proving that such bed is chronostratigraphically equivalent to the K/Pg boundary clay of the El Kef stratotype. These new micropaleontogical data confirm that the K/Pg impact event and the Chicxulub impact event are the same one. This contradicts the suggestion by others that the Chicxulub impact predated the K/Pg boundary by about 300 ka. © 2006 Elsevier B.V. All rights reserved. 2006 10.1016/j.epsl.2006.07.020 Earth and Planetary Science Letters 249 241-257 Departamento de Ciencias de la Tierra (Paleontología), Universidad de Zaragoza, 50009 Zaragoza, Spain; Instituto Mexicano del Petróleo (Exploración y Producción), Eje Lazaro Cardenas # 152, Mexico D.F. 07730, Mexico; Department of Earth and Planetary Science, University of California, 307 McCone Hall, Berkeley, CA 94720-4767, United States; Petróleos Mexicanos, Exploración y Producción, Blvd. A. Ruiz Cortines 1202, Villahermosa, Tabasco, 86030, Mexico 3-4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749334489&doi=10.1016%2fj.epsl.2006.07.020&partnerID=40&md5=b26a3659aa560054bcc5e4f7dad6bb51 cited By 78 I. Arenillas J.A. Arz J.M. Grajales-Nishimura G. Murillo-Muñetón W. Alvarez A. Camargo-Zanoguera E. Molina C. Rosales-Domínguez article Tuchscherer20061361 Melt particles found at various depths in impactites from the Yaxcopoil-1 borehole into the Chicxulub impact structure (Yucatán) have been analyzed for their major and trace element abundances. A total of 176 electron microprobe and 45 LA-ICP-MS analyses from eight different melt particles were investigated. The main purpose of this work was to constrain the compositions of precursor materials and secondary alteration characteristics of these melt particles. Individual melt particles are highly heterogeneous, which makes compositional categorization extremely difficult. Melt particles from the uppermost part of the impactite sequence are Ca- and Na-depleted and show negative Ce anomalies, which is likely a result of seawater interaction. Various compositional groupings of melt particles are determined with ternary and binary element ratio plots involving major and trace elements. This helps distinguish the degree of alteration versus primary heterogeneity of melt phases. Comparison of the trace element ratios Sc/Zr, Y/Zr, Ba/ Zr, Ba/Rb, and Sr/Rb with compositions of known target rocks provides some constraints on protolith compositions; however, the melt compositions analyzed exceed the known compositional diversity of possible target rocks. Normalized REE patterns are unique for each melt particle, likely reflecting precursor mineral or rock compositions. The various discrimination techniques indicate that the highly variable compositions are the products of melting of individual minerals or of mixtures of several minerals. Small, angular shards that are particularly abundant in units 2 and 3 represent rapidly quenched melts, whereas larger particles (>0.5 mm) that contain microlites and have fluidal, schlieric textures cooled over a protracted period. Angular, shard-like particles with microlites in unit 5 likely crystallized below the glass transition temperature or underwent fragmentation during or after deposition. © The Meteoritical Society, 2006. 2006 10.1111/j.1945-5100.2006.tb00527.x Meteoritics and Planetary Science 41 1361-1379 Impact Cratering Research Group, School of Geosciences, University of the Witwatersrand, Private Bag 3, 2050 Johannesburg, South Africa; Caracle Creek International Consulting Inc., Private Bag X9, Melville 2109, South Africa; Museum für Naturkunde, Humboldt-Universität, Invalidenstrasse 43, D-10115 Berlin, Germany; Council for Geoscience, Private Bag X112, 0001 Pretoria, South Africa; Department of Geological Sciences, University of Cape Town, Rondesbosch 7701, South Africa 9 https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749249955&doi=10.1111%2fj.1945-5100.2006.tb00527.x&partnerID=40&md5=cf65b86b23d5ddfb398aff839098a0d3 cited By 12 M.G. Tuchscherer W.U. Reimold R.L. Gibson D. De Bruin A. Späth article Pirajno2005587 Meteorite impacts cause conversion of kinetic energy into thermal energy. Part of this thermal energy is used to form a melt sheet, part is dissipated to heat the target rocks and these together with the hot rocks that elastically rebound from the depth of several kilometres (central uplift) activate hydrothermal circulation. Impact-generated hydrothermal systems have been documented from several impact structures world-wide. Three Australian examples-Shoemaker, Woodleigh and Yarrabubba-provide evidence of hydrothermal fluid flow both within and around the structures. Field observations, and petrographic and geochemical data suggest a common evolutionary trend of post-impact hydrothermal activity from early high-temperature alkali metasomatism to a later lower temperature H+ metasomatism, resulting in the overprinting by hydrous mineral assemblages. Hydrothermal systems activated by meteorite-impact events are important because they may also form economic mineral deposits, as is documented for several impact structures in the world. A working model of hydrothermal circulation in terrestrial impact structures posits two main stages: (i) initial high-temperature fluids percolate downward causing widespread alkali metasomatism of the shattered target rocks below the melt sheet, resulting in their modification to rocks of syenitic affinity; and (ii) inflow of meteoric water and progressive cooling of the melt sheet leads to a lower temperature stage, in which hydrothermal fluid flow tends to move upward, resulting in mineral assemblages and alteration patterns that resemble those of epithermal systems. In addition, these fluids can discharge at the surface as hot springs. © Geological Society of Australia. 2005 10.1080/08120090500170468 Australian Journal of Earth Sciences 52 587-605 Geological Survey of Western Australia, 100 Plain Street, East Perth, WA 6004, Australia 4-5 https://www.scopus.com/inward/record.uri?eid=2-s2.0-27344457427&doi=10.1080%2f08120090500170468&partnerID=40&md5=2e5e9aa1e78f749314b4376625470230 cited By 25 F. Pirajno article Turtle20051 The diameter of an impact crater is one of the most basic and important parameters used in energy scaling and numerical modeling of the cratering process. However, within the impact and geological communities and literature, there is considerable confusion about crater sizes due to the occurrence of a variety of concentric features, any of which might be interpreted as defining a crater's diameter. The disparate types of data available for different craters make the use of consistent metrics difficult, especially when comparing terrestrial to extraterrestrial craters. Furthermore, assessment of the diameters of terrestrial craters can be greatly complicated due to post-impact modification by erosion and tectonic activity. We analyze the terminology used to describe crater geometry and size and attempt to clarify the confusion over what exactly the term "crater diameter" means, proposing a consistent terminology to help avert future ambiguities. We discuss several issues of crater-size in the context of four large terrestrial examples for which crater diameters have been disputed (Chicxulub, Sudbury, Vredefort, and Chesapeake Bay) with the aim of moving toward consistent application of terminology. © 2005 Geological Society of America. 2005 10.1130/0-8137-2384-1.1 Special Paper of the Geological Society of America 384 1-24 Lunar and Planetary Laboratory, Department of Planetary Sciences, University of Arizona, Tucson, AZ 85721-0092, United States; Planetary Science Institute, 1700 E. Fort Lowell, Tucson, AZ 85719-2395, United States; Department of Earth Science and Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom; Impact Cratering Research Group, School of Geosciences, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg, South Africa; Canadian Space Agency, 6767 Route de l'Aeroport, Saint-Hubert, QC J3Y 8Y9, Canada https://www.scopus.com/inward/record.uri?eid=2-s2.0-73949102617&doi=10.1130%2f0-8137-2384-1.1&partnerID=40&md5=23d21d9a5fa01676fb8d016a97934942 cited By 106 E.P. Turtle E. Pierazzo G.S. Collins G.R. Osinski H.J. Melosh J.V. Morgan W.U. Reimold article Osinski20051789 Contrary to the previous interpretation of a single allochthonous impactite lithology, combined field, optical, and analytical scanning electron microscopy (SEM) studies have revealed the presence of a series of impactites at the Haughton impact structure. In the crater interior, there is a consistent upward sequence from parautochthonous target rocks overlain by parautochthonous lithic (monomict) breccias, through allochthonous lithic (polymict) breccia, into pale grey allochthonous impact melt breccias. The groundmass of the pale grey impact melt breccias consists of microcrystalline calcite, silicate impact melt glass, and anhydrite. Analytical data and microtextures indicate that these phases represent a series of impact-generated melts that were molten at the time of, and following, deposition. Impact melt glass clasts are present in approximately half of the samples studied. Consideration of the groundmass phases and impact glass clasts reveal that impactites of the crater interior contain shock-melted sedimentary material from depths of >920 to <1880 m in the pre-impact target sequence. Two principal impactites have been recognized in the near-surface crater rim region of Haughton. Pale yellow-brown allochthonous impact melt breccias and megablocks are overlain by pale grey allochthonous impact melt breccias. The former are derived from depths of >200 to <760 m and are interpreted as remnants of the continuous ejecta blanket. The pale grey impact melt breccias, although similar to the impact melt breccias of the crater interior, are more carbonate-rich and do not appear to have incorporated clasts from the crystalline basement. Thus, the spatial distribution of the crater-fill impactites at Haughton, the stratigraphic succession from target rocks to allochthonous impactites, the recognition of large volumes of impact melt breccias, and their probable original volume are all analogous to characteristics of coherent impact melt layers in comparatively sized structures formed in crystalline targets. © The Meteoritical Society, 2005. 2005 10.1111/j.1945-5100.2005.tb00147.x Meteoritics and Planetary Science 40 1789-1812 Planetary and Space Science Centre, Department of Geology, University of New Brunswick, 2 Bailey Drive, Fredericton, NB E3B 5A3, Canada; Canadian Space Agency, 6767 Route de l'Aeroport, Saint-Hubert, Que. J3Y 8Y9, Canada; Mars Institute, NASA Ames Research Center, Moffett Field, CA 94035-1000, United States 12 https://www.scopus.com/inward/record.uri?eid=2-s2.0-33244466987&doi=10.1111%2fj.1945-5100.2005.tb00147.x&partnerID=40&md5=da09b23d420ccb4a96027d24d6eea642 cited By 51 G.R. Osinski J.G. Spray P. Lee article Adatte200537 The late Maastrichtian to early Danian at Mishor Rotem, Israel, was examined based on geochemistry, bulk rock and clay mineralogies, biostratigraphy and lithology. This section contains four red clay layers of suspect impact or volcanic origin interbedded in chalk and marly chalks. PGE anomalies indicate that only the K/T boundary red layer has an Ir dominated PGE anomaly indicative of an impact source. The late Maastrichtian red clays have Pd dominated PGE anomalies which coincide with increased trace elements of terrigenous and volcanogenic origins. Deccan or Syrian-Turkey arc volcanism is the likely source of volcanism in these clay layers. Glauconite, goethite and translucent amber spherules are present in the clay layers, but the Si-rich spherules reported by Rosenfeld et al. [1989] could not be confirmed. The absence of Cheto smectite indicates that no altered impact glass has been present. The red layers represent condensed sedimentation on topographic highs during sea level highstands. In the Negev area, during the late Maastrichtian, the climate ranged from seasonally wet to more arid conditions during zones CF3 and CF2, with more humid wet conditions in the latest Maastrichtian zone CF1 and in the early Danian, probably linked to greenhouse conditions. Planktic foraminifera experienced relatively high stress conditions during this time as indicated by the low species richness and low abundance of globotruncanids. Times of intensified stress are indicated by the disaster opportunist Guembelitria blooms, which can be correlated to central Egypt and also to Indian Ocean localities associated with mantle plume volcanism. Marine plankton thus support the mineralogical and geochemical observations of volcanic influx and reveal the detrimental biotic effects of intense volcanism. 2005 10.2113/176.1.37 Bulletin de la Societe Geologique de France 176 37-55 Geological Institut, University of Neuchatel, CH-2007 Neuchatel, Switzerland; Department of Geosciences, Princeton University, Princeton, NJ 08544, United States; Institut of Mineralogy/Geochemistry, University of Karlsruhe, 76128 Karlsruhe, Germany; Geological Institut, University of Karlsruhe, P.O. Box 6980, 76128 Karlsruhe, Germany; Dept. Geol./Environmental Sciences, Ben Gurion University of the Negev, P.O. Box 653, Beer Sheva 84105, Israel 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-15044362467&doi=10.2113%2f176.1.37&partnerID=40&md5=6d2c0c32c2c351cfdba71ca777a2efe1 cited By 22 T. Adatte G. Keller D. Stüben M. Harting U. Kramar W. Stinnesbeck S. Abramovich C. Benjamini article Masaitis2005509 Impact cratering produces not only craterform topographic features, but also structural disturbances at the site of impact, and a spectrum of transformed and newly formed rocks. The term 'coptogenesis' (from the Greek χoπτo, to destroy by shock) may be used collectively to describe the impact process-a process fundamental to all cosmic bodies. Principal coptogenic topographic features of terrestrial impact craters may be subdivided into excavational, structural and accumulative landforms, most of which subsequently experience various processes of degradation. Nevertheless, the original shape of craters may in some cases be reconstructed and compared with fresh craters on other planets. An immediate conformity between the pre-erosional topographic features of complex terrestrial craters, and the morphostructural elements of their erosional remnants, is not a standing rule. Geological observations show that the inner structure of the proximal crater fill and distal ejecta are characterised by pseudo-stratification and that these materials represent a group of facies of impact-derived and impact-related, or coptogenic, lithologies. The study of these facies allows us to distinguish various facies settings of rock-forming processes. Impact lithologies, or coptogenic rocks, may be systematised and classified using the principles adopted by igneous petrology and volcanology. Appropriate geological methods and approaches should be applied to the investigation of terrestrial impact craters, including their identification, mapping, and study of their various physiographic, structural, and lithological features. © Geological Society of Australia. 2005 10.1080/08120090500170427 Australian Journal of Earth Sciences 52 509-528 Karpinsky Geological Institute, Sredny prospect 74, St Petersburg 199106, Russian Federation 4-5 https://www.scopus.com/inward/record.uri?eid=2-s2.0-27344446833&doi=10.1080%2f08120090500170427&partnerID=40&md5=7d46ea45ba9f3dc1845bebe8b52caafd cited By 11 V.L. Masaitis article Ebel2005293 Formation of the giant Chicxulub crater off Mexico's Yucatan Peninsula coincided with deposition of the global Ir-rich Cretaceous-Tertiary (K-T) stratigraphic boundary layer ca. 65 Ma. The boundary is marked most sharply by abundant spherules containing un-altered grains of magnesioferrite spinel. Here we predict for the first time the sequential condensation of solids and liquids from the plume of vaporized rock expected from oblique K-T impacts. We predict highly oxidizing plumes that condense silicate liquid droplets bearing spinel grains whose compositions closely match those marking the actual boundary. Systematic global variations in spinel composition are consistent with higher condensation temperatures for spinels found at Atlantic and European sites than for those in the Pacific. © 2005 Geological Society of America. 2005 10.1130/G21136.1 Geology 33 293-296 Dept. of Earth/Planetary Sciences, American Museum of Natural History, 79th Street at Central Park West, New York, NY 10024-5192, United States; Dept. of the Geophysical Sciences, Enrico Fermi Institute, University of Chicago, Chicago, IL 60637, United States 4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-17144377156&doi=10.1130%2fG21136.1&partnerID=40&md5=755403fa8d3a339c2c3fc198817947d4 cited By 45 D.S. Ebel L. Grossman article Naumov2005165 Any hypervelocity impact generates a hydrothermal circulation system in resulting craters. Common characteristics of hydrothermal fluids mobilized within impact structures are considered, based on mineralogical and geochemical investigations, to date. There is similarity between the hydrothermal mineral associations in the majority of terrestrial craters; an assemblage of clay minerals-zeolites-calcite-pyrite is predominant. Combining mineralogical, geochemical, fluid inclusion, and stable isotope data, the distinctive characteristics of impact-generated hydrothermal fluids can be distinguished as follows: (i) superficial, meteoric and ground water and, possibly, products of dehydration and degassing of minerals under shock are the sources of hot water solutions; (ii) shocked target rocks are sources of the mineral components of the solutions; (iii) flow of fluids occurs mainly in the liquid state; (iv) high rates of flow are likely (10-4 to 10-3 m s-1); (v) fluids are predominantly aqueous and of low salinity; (vi) fluids are weakly alkaline to near-neutral (pH 6-8) and are supersaturated in silica during the entire hydrothermal process because of the strong predominance of shock-disordered aluminosilicates and fusion glasses in the host rocks; and (vii) variations in the properties of the circulating solutions, as well as the spatial distribution of secondary mineral assemblages are controlled by temperature gradients within the circulation cell and by a progressive cooling of the impact crater. Products of impact-generated hydrothermal processes are similar to the hydrothermal mineralization in volcanic areas, as well as in modern geothermal systems, but impacts are always characterized by a retrograde sequence of alteration minerals. © 2005 Blackwell Publishing Ltd. 2005 10.1111/j.1468-8123.2005.00092.x Geofluids 5 165-184 Karpinsky All-Russia Geological Research Institute (VSEGEI), 199106 Sredny pr. 74, St. Petersburg, Russian Federation 3 https://www.scopus.com/inward/record.uri?eid=2-s2.0-22744445294&doi=10.1111%2fj.1468-8123.2005.00092.x&partnerID=40&md5=477bfb8c4fff5946d31415ab743bf354 cited By 91 M.V. Naumov article Sherlock20051777 We have re-evaluated the published age information for the Haughton impact structure, which was believed to have formed ∼23 Ma ago during the Miocene age, and report new Ar/Ar laser probe data from shocked basement clasts. This reveals an Eocene age, which is at odds with the published Miocene stratigraphic, apatite fission track and Ar/Ar data; we discuss our new data within this context. We have found that the age of the Haughton impact structure is ∼39 Ma, which has implications for both crater recolonization models and post-impact hydrothermal activity. Future work on the relationship between flora and fauna within the crater, and others at high latitude, may resolve this paradox. © The Meteoritical Society, 2005. 2005 10.1111/j.1945-5100.2005.tb00146.x Meteoritics and Planetary Science 40 1777-1787 Centre for Earth Planetary Space and Astronomical Research (CEPSAR), Department of Earth Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, United Kingdom; Department of Geology and Petroleum Geology, College of Physical Sciences, University of Aberdeen, Meston Building, Aberdeen AB24 3UE, United Kingdom; Geotrack International, 37 Melville Road, Brunswick West, Vic. 3055, Australia; Mars Institute, NASA Ames Research Center, MS 245-3, Moffett Field, CA 94035-1000, United States; Canadian Space Agency, 6767 Route de l'Aeroport, Saint-Hubert, Que. J3Y 8Y9, Canada; Centre for Earth Planetary Space and Astronomical Research (CEPSAR), Planetary and Space Sciences Research Institute, The Open University, Walton Hall, Milton Keynes MK7 6AA, United Kingdom 12 https://www.scopus.com/inward/record.uri?eid=2-s2.0-33244493970&doi=10.1111%2fj.1945-5100.2005.tb00146.x&partnerID=40&md5=1adf767a3c9a23a32d72545168e851db cited By 41 S.C. Sherlock S.P. Kelley J. Parnell P. Green P. Lee G.R. Osinski C.S. Cockell article Zurcher2005223 Carbon, oxygen, and hydrogen isotope results from carbonate and silicate fractions of altered core samples from the Yaxcopoil-1 borehole drilled into the 65 Ma Chicxulub impact crater provide constraints on the physico-chemical parameters of the hydrothermal solutions, and their likely origin. Yaxcopoil-1 impactites were initially permeated with calcite and halite at ambient temperature. This was followed by thermal metamorphism (diopside after igneous augite) and widespread Na-K metasomatism (feldspar after igneous plagioclase), which were overprinted by abundant lower-temperature clay and calcite. Silicate fraction isotopic values have δ 18O SMOW values between 10 and 23% indicating important isotopic exchange between impact melt (∼8%) and Cretaceous limestone (∼26%). Heavier δ 18 O values occur over depth intervals with intense feldspar alteration (813-833 m and 864-872 m). The δD SMOW values (-34 to -54%) are chiefl y infl uenced by smectite abundance and roughly mirror δ 18 O values. Carbonate fraction δ 18 O SMOW values (22-30%) are controlled by calcite contents, and several exceed the limestone signature. Most δ0.13C PDB (-1 to +2%) values also cluster around that of local limestone, but a number are signifi cantly lighter (down to -7%). Isotopic and fluid inclusion results indicate hydrothermal fluid temperatures between 270 and 100 °C, high salinities (∼20%), and minor kerogen contents. These data are compatible with mineralogical constraints, which further support an increase in oxidation state with decreasing temperature. Isotopic data point to a saline CO 2 -bearing fluid mixed with small amounts of reduced carbon, and decarbonation and infi ltration processes. Combined results are most consistent with a basinal oilfi eld saline brine that was driven by impact-induced heat. © 2005 Geological Society of America. 2005 10.1130/0-8137-2384-1.223 Special Paper of the Geological Society of America 384 223-238 Lunar and Planetary Laboratory, University of Arizona, 1629 E. University Boulevard, Tucson, AZ 85721, United States; Department of Geosciences, University of Arizona, 1040 E. Fourth Street, Tucson, AZ 85721, United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-36448978092&doi=10.1130%2f0-8137-2384-1.223&partnerID=40&md5=aa5bf0bc813dd50f0a919a060b37bd79 cited By 12 L. Zurcher D.A. Kring M.D. Barton D. Dettman M. Rollog article Kinsland2005141 Shuttle Radar Topography Mission (SRTM) data over the Chicxulub impact crater are imaged and compared to previously available topography data. While the two data sets contain different biases related to variations in terrain and vegetation cover, the correspondence of the two sets supports earlier interpretations that the complex structure of the buried crater is expressed in the topography of the northwestern Yucatán Peninsula, México. © 2005 Geological Society of America. 2005 10.1130/0-8137-2384-1.141 Special Paper of the Geological Society of America 384 141-146 Energy Institute, University of Louisiana at Lafayette, Lafayette, LA 70504, United States; Geo Eco Arc Research, 16305 St. Mary's Church Road, Aquasco, MD 20608, United States; Instituto Mexicano del Petróleo, Eje Central Lazaro Cardenas 152, Mexico D.F. 07730, Mexico; Department of Geophysics, University of Witwatersrand, Johannesburg 2050, South Africa; Cowan Geodata Services-Consulting Geophysicists, 12 Edna Road, Dalkeith, WA 6009, Australia; SRTM Project Scientist, Jet Propulsion Laboratory, Pasadena, CA 91109, United States; Regional Application Center, University of Louisiana at Lafayette, Lafayette, LA 70504, United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-73949086112&doi=10.1130%2f0-8137-2384-1.141&partnerID=40&md5=ac108c9f1b0a6565f0999c08a3b7a4df cited By 5 G.L. Kinsland K.O. Pope M.H. Cardador G.R.J. Cooper D.R. Cowan M. Kobrick G. Sanchez article Kring20051 The Chicxulub and Ries impact craters were excavated from layered continental terrains that were composed of carbonate-bearing sedimentary sequences and underlying crystalline silicate basement materials. The Chicxulub and Ries impact events were sufficiently large to produce complex peak-ring impact craters. The walls of transient craters and excavation cavities, with diameters of 12-16 km for the Ries and 90-100 km for Chicxulub, collapsed to form final crater diameters of ∼24 and ∼180 km, respectively. Debris from both the sedimentary and crystalline layers was ejected during crater formation, but the bulk of the melting occurred at depth, in the silicate basement. The volume of melt and proportion of melt among shock-metamorphosed debris was far larger at Chicxulub, producing a central melt sheet ∼3 km in depth. The central melt sheet was covered with melt-bearing polymict breccias and, at the Ries, similar breccias (crater suevites) filled the central cavity. Also at the Ries (and presumably at Chicxulub), large hill-size megablocks of crystalline basement material were deposited near the transient crater rim. Blocks and megablocks of sedimentary lithologies were ejected into the modification zone between the peak ring and final crater rim, while additional material was slumping inward during crater growth, and buried beneath a fallout deposit of melt-bearing polymict breccias. The melt and surviving clasts in the breccias are dominantly derived from the deeper, basement lithologies. At greater distances, however, the ejecta is dominated by near-surface sedimentary lithologies, large blocks of which landed with such high energy that they scoured and eroded the pre-existing surface. The excavation and ejecta pattern produced lithological and chemical variations with radial distance from the crater centers that evolve from basement components near the crater centers to sedimentary components far from the crater centers. In addition, carbonate (and anhydrite in the case of Chicxulub) was vaporized, producing environmentally active gases. The vaporized volume produced by the Ries impact event was too small to dramatically alter the evolution of life, but the vaporized volume produced by the Chicxulub impact event is probably a key factor in the Cretaceous-Tertiary boundary mass extinction event. © 2004 Elsevier GmbH. All rights reserved. 2005 10.1016/j.chemer.2004.10.003 Chemie der Erde 65 1-46 Lunar and Planetary Laboratory, University of Arizona, 1629 E. University Blvd., Tucson, AZ 85721, United States 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-13644259335&doi=10.1016%2fj.chemer.2004.10.003&partnerID=40&md5=5b2173e7027150cfff0ee19159d94331 cited By 58 D.A. Kring article Ivanov2005381 Multi-ring impact basins have been found on the surfaces of almost all planetary bodies in the Solar system with solid crusts. The details of their formation mechanism are still unclear. We present results of our numerical modeling of the formation of the largest known terrestrial impact craters. The geological and geophysical data on these structures accumulated over many decades are used to place constraints on the parameters of available numerical models with a dual purpose: (i) to choose parameters in available mechanical models for the crustal response of planetary bodies to a large impact and (ii) to use numerical modeling to refine the possible range of original diameters and the morphology of partially eroded terrestrial craters. We present numerical modeling results for the Vredefort, Sudbury, Chicxulub, and Popigai impact craters and compare these results with available geological and geophysical information. © 2005 Pleiades Publishing, Inc. 2005 10.1007/s11208-005-0051-0 Solar System Research 39 381-409 Institute for Dynamics of Geospheres, Russian Academy of Sciences, Leninskii pr. 38, Moscow, 117979, Russian Federation 5 https://www.scopus.com/inward/record.uri?eid=2-s2.0-27144546662&doi=10.1007%2fs11208-005-0051-0&partnerID=40&md5=0edd01acdae9945c8fe2689c9e3c0953 cited By 153 B.A. Ivanov article Osinski2005202 Combined field studies, optical and scanning electron microscopy, and electron microprobe studies of impactites from the Ries impact structure, Germany, have allowed a clearer picture of the hydrothermal system associated with the Ries impact event to be made. Hydrothermal alteration is concentrated within impact-generated suevites in the interior of the crater (crater suevites) and around the periphery (surficial suevites), with minor alteration in the overlying sedimentary crater-fill deposits. The major heat source for the Ries hydrothermal system was the suevite units themselves. Hydrothermal alteration of crater-fill suevites is pervasive in nature and comprises several distinct alteration phases that vary with depth. An early phase of K-metasomatism accompanied by minor albitization of crystalline basement clasts and minor chloritization, was followed by pervasive intermediate argillic alteration (predominantly montmorillonite, saponite, and illite) and zeolitization (predominantly analcite, erionite, and clinoptilolite). Hydrothermal fluids were typically weakly alkaline during the main stage of alteration. In contrast to the crater-fill suevites, alteration within surficial suevites was typically restricted to montmorillonite and phillipsite deposition within cavities and fractures. The pervasive nature of the alteration within the crater-fill suevites was likely due to the presence of an overlying crater lake; whereas alteration within surficial suevites typically occurred under undersaturated conditions with the main source of water being from precipitation. There are exceptional outcrops of more pervasively altered surficial suevites, which can be explained as locations where water pooled for longer periods of time. Hydrothermal fluids were likely a combination of meteoric waters that percolated down from the overlying crater lake and groundwaters that flowed in from the surrounding country rocks. © 2005 Blackwell Publishing Ltd. 2005 10.1111/j.1468-8123.2005.00119.x Geofluids 5 202-220 Canadian Space Agency, 6767 Route de l'Aeroport, Saint-Hubert, Que. J3Y 8Y9, Canada 3 https://www.scopus.com/inward/record.uri?eid=2-s2.0-22744458934&doi=10.1111%2fj.1468-8123.2005.00119.x&partnerID=40&md5=3df8be2ed9c0aabec36de13a96914b80 cited By 64 G.R. Osinski article https://doi.org/10.1029/2005EO360001 Sixty-five million years ago, a large meteorite hit the Earth and formed the ∼200-km-wide Chicxulub crater in Yucatán, Mexico. The well-known, massive extinction event at the Cretaceous-Tertiary (K-T) boundary appears to have been caused, at least in part, by this impact. In the first few seconds after impact the surface of the Earth was pushed down to form a cavity ∼35 km deep, and in the next few hundred seconds this cavity collapsed to form a multi-ring basin with an inner peak ring. To examine the rings and subsurface structure of this superbly preserved impact crater, a seismic experiment was shot across the crater in January and February 2005 by a team of scientists from Mexico, the United States, and the United Kingdom (Figure 1). 2005 https://doi.org/10.1029/2005EO360001 Eos, Transactions American Geophysical Union 86 325-328 36 https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2005EO360001 Jo Morgan Jaime Urrutia-Fucugauchi Sean Gulick Gail Christeson Penny Barton Mario Rebolledo-Vieyra Jay Melosh article Stüben20052559 The investigation of eight Cretaceous-Tertiary (K/T) sections in Mexico, based on major and trace element, platinum group element (PGE), stable isotope, and multivariate statistical analysis, reveals a complex depositional history across the Chicxulub and K/T boundary events. At the biostratigraphically determined K/T boundary, a minor but significant Ir-dominated PGE anomaly (0.2-0.8 ng/g) is present in most sections. This Ir anomaly originated from an impact event and is always stratigraphically and geochemically decoupled from the underlying spherule-rich ejecta deposit related to the Chicxulub event. In all sections examined, one to three glass spherule ejecta layers and one or two chondrite-dominated PGE anomalies are separated by a bioturbated siliciclastic deposit and/or hemipelagic marl, which indicates the occurrence of at least two impact events separated by a considerable amount of time. In addition, bentonite layers and Pt and Pd-dominated PGE anomalies below and above the K/T boundary indicate volcanic activity. Above the K/T boundary, reduced bioproductivity is documented by a decrease in the biogenically bound fraction of nutrients and fluctuating ratios of immobile elements (e.g., Ti/Zr). Variations in detrital elements reflect changes in the depositional environment. Carbon and oxygen isotope and trace element distribution patterns indicate a gradually changing climate during the latest Maastrichtian, an abrupt change at the K/T boundary, and a slight recovery during the lowermost Paleocene. Copyright © 2005 Elsevier Ltd. 2005 10.1016/j.gca.2004.11.003 Geochimica et Cosmochimica Acta 69 2559-2579 Institut für Mineralogie und Geochemie, Universität Karlsruhe, D-76128 Karlsruhe, Germany; Geologisches Institut, Universität Karlsruhe, D-76128 Karlsruhe, Germany; Department of Geosciences, Princeton University, Princeton, NJ 08544, United States 10 https://www.scopus.com/inward/record.uri?eid=2-s2.0-19044393897&doi=10.1016%2fj.gca.2004.11.003&partnerID=40&md5=6ae3f602d60c33ee776f5444b0f92c62 cited By 41 D. Stüben U. Kramar M. Harting W. Stinnesbeck G. Keller article Osinski20051859 The well-preserved state and excellent exposure at the 39 Ma Haughton impact structure, 23 km in diameter, allows a clearer picture to be made of the nature and distribution of hydrothermal deposits within mid-size complex impact craters. A moderate- to low-temperature hydrothermal system was generated at Haughton by the interaction of groundwaters with the hot impact melt breccias that filled the interior of the crater. Four distinct settings and styles of hydrothermal mineralization are recognized at Haughton: a) vugs and veins within the impact melt breccias, with an increase in intensity of alteration towards the base; b) cementation of brecciated lithologies in the interior of the central uplift; c) intense veining around the heavily faulted and fractured outer margin of the central uplift; and d) hydrothermal pipe structures or gossans and mineralization along fault surfaces around the faulted crater rim. Each setting is associated with a different suite of hydrothermal minerals that were deposited at different stages in the development of the hydrothermal system. Minor, early quartz precipitation in the impact melt breccias was followed by the deposition of calcite and marcasite within cavities and fractures, plus minor celestite, barite, and fluorite. This occurred at temperatures of at least 200 °C and down to ∼100-120 °C. Hydrothermal circulation through the faulted crater rim with the deposition of calcite, quartz, marcasite, and pyrite, occurred at similar temperatures. Quartz mineralization within breccias of the interior of the central uplift occurred in two distinct episodes (∼250 down to ∼90 °C, and <60 °C). With continued cooling (<90 °C), calcite and quartz were precipitated in vugs and veins within the impact melt breccias. Calcite veining around the outer margin of the central uplift occurred at temperatures of ∼150 °C down to <60 °C. Mobilization of hydrocarbons from the country rocks occurred during formation of the higher temperature calcite veins (>80 °C). Appreciation of the structural features of impact craters has proven to be key to understanding the distribution of hydrothermal deposits at Haughton. © The Meteoritical Society, 2005. 2005 10.1111/j.1945-5100.2005.tb00150.x Meteoritics and Planetary Science 40 1859-1877 Lunar and Planetary Laboratory, University of Arizona, 1629 East University Boulevard, Tucson, AZ 85721-0092, United States; Canadian Space Agency, 6767 Route de l'Aéroport, Saint-Hubert, Que. J3Y 8Y9, Canada; SETI Institute, NASA Ames Research Center, MS 245-3, Moffett Field, CA 94035-1000, United States; Geofluids Research Group, Department of Geology and Petroleum Geology, University of Aberdeen, Aberdeen AB24 3UE, United Kingdom; Planetary and Space Science Centre, Department of Geology, University of New Brunswick, 2 Bailey Drive, Fredericton, NB E3B 5A3, Canada 12 https://www.scopus.com/inward/record.uri?eid=2-s2.0-18944377646&doi=10.1111%2fj.1945-5100.2005.tb00150.x&partnerID=40&md5=c665111c97b972b2c0638646d5af3f24 cited By 86 G.R. Osinski P. Lee J. Parnell J.G. Spray M. Baron article Scasso2005283 A coarse-grained sandstone bed of Cretaceous/Paleogene (K/Pg) boundary age occurs in a homogeneous neritic shelf mudstone sequence (Jagüel Formation) in the Neuquén Basin of Argentina. This bed, 15 - 25 cm thick, contains abundant plagioclase, broken shells and sharks' teeth. Sedimentological features include an erosive base, abundant rip-up clasts, normal grading and hummocky cross-bedding. The K/Pg boundary age of the bed was confirmed by calcareous nannofossils. Similar to other sections in the Gulf Coast region and the Danish Basin, a "dead zone" significantly depleted in macrofossils is evident in the basal 1 m above the clastic layer. In combination, these features suggest that the clastic layer represents a tsunami deposit that was related to the Chicxulub impact event in Yucatan/Mexico. Mechanisms of tsunami wave amplification in this extremely distal and somewhat protected setting are poorly understood but the funnel-shape of the basin may have promoted the unusually strong sedimentological response. © 2005 Elsevier Ltd. All rights reserved. 2005 10.1016/j.cretres.2004.12.003 Cretaceous Research 26 283-297 Departamento de Ciencias Geologicas, FCEN, Universidad de Buenos Aires, 1428 Buenos Aires, Argentina; Museum für Naturkunde, Institut für Paläontologie, Humboldt-Universität Berlin, Invalidenstr. 43, D-10115 Berlin, Germany; Museum für Naturkunde, Institut für Mineralogie, Humboldt-Universität Berlin, Invalidenstr. 43, D-10115 Berlin, Germany 2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-17444383780&doi=10.1016%2fj.cretres.2004.12.003&partnerID=40&md5=bd45acb20457f4a3089ab5852a0f7dec cited By 35 R.A. Scasso A. Concheyro M. Aberhan L. Hecht F.A. Medina R. Tagle article Lawton200581 Ejecta-bearing strata are present at the top of Cretaceous foreland-basin deposits throughout the La Popa basin in northeastern Mexico. In the southeast part of the basin, locally thick (as much as 4.6 m) ejecta-rich conglomeratic strata occupy valley-like features at a bathymetric break that separated Maastrichtian upper shoreface from lower shoreface and prodelta depositional settings. Clast-supported textures, normally graded planar conglomerate-sandstone couplets, upcurrent-dipping low-angle cross-laminae, sparse paleocurrent data, and transported fossils indicate deposition by south- to southeast-directed turbulent, supercritical flow. In the northwest part of the basin, ejecta grains are present but less common in correlative deposits. Sediment, ejecta, and organisms were eroded from shoreward environments and transported basinward by backflow of run-up surge(s) emplaced against the continent by one or several tsunami(s). High-discharge, supercritical offshore-directed flow provides a mechanism for transport of voluminous, ejecta-bearing sediment and late Maastrichtian marine organisms into deep-water Gulf of Mexico settings. © 2005 Geological Society of America. 2005 10.1130/G21057.1 Geology 33 81-84 Institute of Tectonic Studies, New Mexico State University, Las Cruces, NM 88003, United States; Instituto de Geología, Univ. Nac. Autonoma de Mexico, Ciudad Universitaria, Coyoacán, D.F. 04510, Mexico 2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-13944275932&doi=10.1130%2fG21057.1&partnerID=40&md5=15a768335edf0be07bf122810a38602f cited By 49 T.F. Lawton K.W. Shipley J.L. Aschoff K.A. Giles F.J. Vega article Tagle20052877 With a diameter of ∼100 km, Popigai in Northern Siberia is the largest crater known in the Cenozoic. The concentrations in platinum group elements (PGE) were analyzed in twenty samples of homogeneous impact melt collected in the northwestern flank of the crater to identify the composition of the projectile. The method selected was preconcentration by NiS fire assay followed by inductively coupled plasma-mass spectrometry (ICP-MS). This technique measures all the PGE (except Os) and by using aliquots >10g, the results are highly reproducible. The major and trace element composition of the impact melt resembles that of gneissic lithologies of the Anabar shield, which are representative of the target rock. The PGE are enriched in the melt by factors of 3 to 14 compared to the main target lithology, but the meteoritic contamination is only around 0.2 wt.%. Using plots of elemental ratios such as Ru/Rh vs. Pt/Pd or Ru/Rh vs. Pd/Ir, the Popigai impactor is clearly identified as an ordinary chondrite and most likely l-chondrite. This study indicates that PGE elemental ratios allow discrimination of the type of impactor, even in the case of low meteoritic contamination. This study confirms that a significant fraction of the crater-forming projectiles presently documented could have an ordinary chondrite composition. Their probable source, the S-type asteroids, appears to form the majority of the bodies in the main asteroid belt and among Near Earth Objects (NEOs). The ordinary chondrite origin of the Popigai projectile supports an asteroidal origin for the late Eocene impacts as a plausible alternative to the comet shower scenario proposed by Farley et al. (1998). Copyright © 2005 Elsevier Ltd. 2005 10.1016/j.gca.2004.11.024 Geochimica et Cosmochimica Acta 69 2877-2889 Institut für Mineralogie, Museum für Naturkunde, D-10099 Berlin, Germany; Dept. of Geology, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium 11 https://www.scopus.com/inward/record.uri?eid=2-s2.0-20344393592&doi=10.1016%2fj.gca.2004.11.024&partnerID=40&md5=acd32f2bee196156ec6df99a896721a0 cited By 61 R. Tagle P. Claeys article Schulte2005191 The combined petrological and rock magnetic study of the Cretaceous-Paleogene (K-P) boundary in northeastern México revealed compositionally and texturally complex Chicxulub ejecta deposits. The predominant silicic ejecta components are Fe-Mg-rich chlorite and Si-Al-K-rich glass spherules with carbonate inclusions and schlieren. Besides these silica phases, the most prominent ejecta component is carbonate. Carbonate occurs as lithic clasts, accretionary lapilli, melt globules (often with quench textures), and as microspar. The composition of the spherules provides evidence for a range of target rocks of mafi c to intermediate composition, presumably situated in the northwestern sector of the Chicxulub impact structure. The abundance of carbonate ejecta suggests that this area received ejecta mainly from shallow, carbonate-rich lithologies. Rare μm-sized metallic and sulfi dic Ni-Corich inclusions in the spherules indicate a possible contamination by meteoritic material. This complex composition underlines the similarities of ejecta in NE México to Chicxulub ejecta from K-P sections worldwide. Although the ejecta display a great variability, the magnetic susceptibility, remanence, and hysteresis properties of the ejecta deposits are fairly homogeneous, with dominantly paramagnetic susceptibilities and a weak ferromagnetic contribution from hematite and goethite. The absence of spinels and the ubiquitous presence of hematite and goethite points to high oxygen fugacity during the impact process. The microfacies and internal texture of the ejecta deposits show welding and fusing of components, as well as evidence for liquid immiscibility between silicic and carbonate melts. No evidence for binary mixing of ejecta phases was found. Therefore, Chicxulub ejecta in NE México probably derived from less energetic parts of the ejecta curtain. However, welding features of ejecta particles and enclosed marl clasts and/or benthic foraminifera from a siliciclastic environment suggest interaction of the-still hot-ejecta curtain with northern Mexican shelf sediments. In addition, an initial ground surge-like ejecta-dispersion mode seems possible. © 2005 Geological Society of America. 2005 10.1130/0-8137-2384-1.191 Special Paper of the Geological Society of America 384 191-221 Geologisches Institut, Universität Karlsruhe (TH), Kaiserstrasse 12, D-76128 Karlsruhe, Germany; Geologisch-Paläontologisches Institut, Universität Heidelberg, Im Neuenheimer Feld 234, D-69120 Heidelberg, Germany; Institut für Geologie, Mineralogie und Geophysik, Ruhr Universität Bochum, Universitätsstrasse 150, D-44801 Bochum, Germany https://www.scopus.com/inward/record.uri?eid=2-s2.0-73949153227&doi=10.1130%2f0-8137-2384-1.191&partnerID=40&md5=6cdf532522181d6b16b89c0071705285 cited By 23 P. Schulte A. Kontny article Šafanda2005326 Temperature-depth profiles, obtained during three campaigns of temperature logging in boreholes of the Yucatán Peninsula in the period 2002-2004, display the effects of thermal fluid convection. These effects are most pronounced in the uppermost part of the 1.5 km deep borehole Yaxcopoil-1 drilled within the Chicxulub impact crater. The convective zone is clearly discernible in all three profiles measured here in March 2002, May 2003 and February 2004. The loggings have revealed a gradual downward propagation of the convective features from the uppermost 145 m of the temperature profile to 230 m between the first and second loggings (with a propagation rate of 6 m/month) and to 265 m between the second and third loggings (4 m/month). A signature of the fluid convection is also evident in all other temperature logs in the area measured during the 2003 campaign, namely in four UNAM boreholes 2, 5, 7 and 8, three hydrogeological boreholes 1A, 1B and 1C, in a borehole at the meteorological observatory Mérida and in the cenote Ucil. The fresh/salt water interface is clearly visible in most of the logs as a zone of increased temperature gradient. The varying intensity of the convective features among the individual logs seems to be correlated with the borehole position relative to the impact structure. © 2005 Nanjing Institute of Geophysical Prospecting. 2005 10.1088/1742-2132/2/4/S05 Journal of Geophysics and Engineering 2 326-331 Geophysical Institute, Prague, Czech Republic; Geophysical Institute, University Karlsruhe, Germany 4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-28544435362&doi=10.1088%2f1742-2132%2f2%2f4%2fS05&partnerID=40&md5=92d41f931876a8d41e21ae1dc394cf41 cited By 12 J. Šafanda P. Heidinger H. Wilhelm V. Čermák article Tuchscherer20051513 We present major and trace element data as well as petrographic observations for impactites (suevitic groundmass, bulk suevite, and melt rock particles) and target lithologies, including Cretaceous anhydrite, dolomite, argillaceous limestone, and oil shale, from the Yaxcopoil-1 borehole, Chixculub impact structure. The suevitic groundmass and bulk suevite have similar compositions, largely representing mixtures of carbonate and silicate components. The latter are dominated by melt rock particles. Trace element data indicate that dolomitic rocks represented a significant target component that became incorporated into the suevites; in contrast, major elements indicate a strong calcitic component in the impactites. The siliceous end-member requires a mafic component in order to explain the low SiO2 content. Multicomponent mixing of various target rocks, the high alteration state, and dilution by carbonate complicate the determination of primary melt particle compositions. However, two overlapping compositional groups can be discerned - a high-Ba, low-Ta group and a high-Fe, high-Zn, and high-Hf group. Cretaceous dolomitic rocks, argillaceous limestone, and shale are typically enriched in U, As, Br, and Sb, whereas anhydrite contains high Sr contents. The oil shale samples have abundances that are similar to the North American Shale Composite (NASC), but with a comparatively high U content. Clastic sedimentary rocks are characterized by relatively high Th, Hf, Zr, As, and Sb abundances. Petrographic observations indicate that the Cretaceous rocks in the Yaxcopoil-1 drill core likely register a multistage deformation history that spans the period from pre- to post-impact. Contrary to previous studies that claimed evidence for the presence of impact melt breccia injection veins, we have found no evidence in our samples from a depth of 1347-1348 m for the presence of melt breccia. We favor that clastic veinlets occur in a sheared and altered zone that underwent intense diagenetic overprint prior to the impact event. © The Meteoritical Society, 2005. 2005 10.1111/j.1945-5100.2005.tb00415.x Meteoritics and Planetary Science 40 1513-1536 Impact Cratering Research Group, School of Geosciences, University of the Witwatersrand, Private Bag 3, P.O. Wits 2050 Johannesburg, South Africa; Department of Geological Sciences, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria 9-10 https://www.scopus.com/inward/record.uri?eid=2-s2.0-29244476876&doi=10.1111%2fj.1945-5100.2005.tb00415.x&partnerID=40&md5=6c1e073f7b9f4f427d1d6626d25aefa0 cited By 22 M.G. Tuchscherer W.U. Reimold C. Koeberl R.L. Gibson article Müller2005264 The Bedout High in the Roebuck Basin (formerly offshore Canning Basin) on the northwest shelf of Australia is an unusual structure, which has been controversially interpreted as an end-Permian impact structure similar in size to the K-T boundary Chicxulub Crater. We present a geophysical perspective of the associated debate, based on deep seismic reflection, refraction and well data. The basement and crust in the Roebuck Basin display a number of features that distinguish them from other basins along the northwest Australian margin, including major crustal thinning and the presence of a thick layer of interpreted magmatic underplating. The Bedout High consists of two separate highs separated by a Paleozoic fault, and is associated with a Moho uplift of 7-8 km, and is about 40-50 km wide. The normal fault separating the two highs trends NNW-SSE, roughly paralleling a Paleozoic fault system associated with rifting in the Canning Basin and terminating below the interpreted top-Permian reflection. There are no circular, symmetric fault zones bounding the proposed annular trough, and the distinct difference in seismic character normally associated with impact breccias versus layered sediments above are not expressed in deep multichannel seismic data. The end-Permian horizon exhibits little topography, with well-layered units both below and above. The area around the Bedout High stands out as an area of low velocity basement: 5400-5600 m/s compared to 5800-6000 m/s for other nearby basement areas located in a similar depth range, but known complex impact sites are not characterized by a unique seismic basement velocity signature. Both seismic velocity analysis, revealing a thick underplated layer in the lower crust, and thermal modelling based on data from well La Grange-1 and basalts drilled on top of the Bedout High, are consistent with rifting above anomalously hot mantle. The available geophysical and geological data are compatible with an interpretation of the Bedout structure as a basement high formed by two consecutive Paleozoic and Mesozoic episodes of rifting roughly orthogonal to each other, associated with basin formation east and west of the Bedout High, but fail nearly all unequivocal criteria for impact crater recognition. © 2005 Elsevier B.V. All rights reserved. 2005 10.1016/j.epsl.2005.06.014 Earth and Planetary Science Letters 237 264-284 School of Geosciences, University of Sydney, Institute of Marine Science, Build. F05, Sydney, NSW 2006, Australia; Geoscience Australia, GPO Box 378, Canberra, ACT 2601, Australia; Statoil Research Center, Arkitekt Ebbellsvei 10, Rotvoll N-7005 Trondheim, Norway 1-2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-24144465141&doi=10.1016%2fj.epsl.2005.06.014&partnerID=40&md5=24329e8d1670495819a62d4118ec3e57 cited By 32 R.D. Müller A. Goncharov A. Kritski article Wilhelm2005357 Boreholes drilled in impact structures are especially suited for investigations of the influence of heterogeneities on petrophysical properties and thermal field. In the scientific well Yaxcopoil-1 drilled within the frame of the International Continental Deep Drilling Program (ICDP) and as a part of the Chicxulub Scientific Drilling Project (CSDP) high resolution temperature measurements and a dense petrophysical profile measured on core samples at ∼2.2 m depth intervals were recorded. From the calculated vertical component of the thermal gradient and the thermal conductivity measured on the core samples a mean heat flow density of 70.5 ± 1.9 mW m-2 in the depth interval 400-1400 m was determined. On the basis of a simple purely conductive heterogeneous 2D thermal model the effect of the refraction of heat caused by heterogeneities is demonstrated. A statistical investigation shows that if the scales of the heterogeneities influencing the values of the measured thermal conductivity and the calculated thermal gradient are small compared to the length of the borehole the effect of the heterogeneities on the vertical heat flow density can be interpreted as thermal noise. © 2005 Nanjing Institute of Geophysical Prospecting. 2005 10.1088/1742-2132/2/4/S09 Journal of Geophysics and Engineering 2 357-363 Geophysical Institute, University of Karlsruhe, Germany; Geophysical Institute, Czech Academy of Sciences, Prague, Czech Republic; Institute of Applied Geosciences, Technical University of Berlin, Germany; Moscow State Geological Prospecting University, Moscow, Russian Federation 4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-28544436762&doi=10.1088%2f1742-2132%2f2%2f4%2fS09&partnerID=40&md5=2c9f6401e13b37d38154247d3683cef7 cited By 9 H. Wilhelm Y. Popov H. Burkhardt J. Šafanda V. Čermák P. Heidinger D. Korobkov R. Romushkevich S. Mayr article Tagle20041009 This study presents results of platinum group element (PGE) analyses of impactites from the Yaxcopoil-1 (Yax- 1) and Yucatán 6 drill cores of the 180 km-diameter Chicxulub crater. These are the main elements used for projectile identification. They were determined by nickel sulfide fire assay combined with inductively coupled plasma mass spectrometry. The concentration of PGE in the samples are low. The concentration patterns of the suevite samples resemble the pattern of the continental crust. We conclude that any meteoritic fraction in these samples is below 0.05%. A synand post-impact modification of the PGE pattern from meteoritic toward a continental crust pattern is very unlikely. The globally distributed fallout at the Cretaceous-Tertiary (K/T) boundary, however, has high PGE concentrations. Therefore, the lack of a significant meteoritic PGE signature in the crater is not an argument for a PGE-poor impactor. Taking the results of three-dimensional numerical simulations of the Chicxulub event into account, the following conclusions are drawn: 1) The main fraction of the impactor was ejected into and beyond the stratosphere, distributed globally, and deposited in the K/T boundary clay; and 2) the low amount of projectile contamination in the Yax-1 lithologies may reflect an oblique impact. However, the role of volatiles in the mixing process between projectile and target is not well-understood and may also have played a fundamental role. 2004 10.1111/j.1945-5100.2004.tb00942.x Meteoritics and Planetary Science 39 1009-1016 Institut für Mineralogie, Museum für Naturkunde, Humboldt-Universität zu Berlin, Invalidenstrasse 43, Berlin D-10099, Germany; GFZ-Potsdam, Potsdam 14473, Germany; Vrije Universiteit Brussel, Pleinlaan 2, Brussels B-1050, Belgium 6 https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943057392&doi=10.1111%2fj.1945-5100.2004.tb00942.x&partnerID=40&md5=e45a383e937de5e76e83564650ff0335 cited By 25 R. Tagle J. Erzinger L. Hecht R.T. Schmitt D. Stöffler P. Claeys article Keller20041127 Yaxcopoil-1 (Yax-1), drilled within the Chicxulub crater, was expected to yield the final proof that this impact occurred precisely 65 Myr ago and caused the mass extinction at the Cretaceous-Tertiary (K/T) boundary. Instead, contrary evidence was discovered based on five independent proxies (sedimentologic, biostratigraphic, magnetostratigraphic, stable isotopic, and iridium) that revealed that the Chicxulub impact predates the K/T boundary by about 300,000 years and could not have caused the mass extinction. This is demonstrated by the presence of five bioturbated glauconite layers and planktic foraminiferal assemblages of the latest Maastrichtian zone CF1 and is corroborated by magnetostratigraphic chron 29r and characteristic late Maastrichtian stable isotope signals. These results were first presented in Keller et al. (2004). In this study, we present more detailed evidence of the presence of late Maastrichtian planktic foraminifera, sedimentologic, and mineralogic analyses that demonstrate that the Chicxulub impact breccia predates the K/T boundary and that the sediments between the breccia and the K/T boundary were deposited in a normal marine environment during the last 300,000 years of the Cretaceous. © Meteoritical Society, 2004. Printed in USA. 2004 10.1111/j.1945-5100.2004.tb01133.x Meteoritics and Planetary Science 39 1127-1144 Department of Geosciences, Princeton University, Princeton, NJ 08544, United States; Geological Institute, University of Neuchâtel, Neuchâtel CH-2007, Switzerland; Geologisches Institut, Universität Karlsruhe, Karlsruhe 76128, Germany; Institut für Mineral/Geochemie, Universität Karlsruhe, Karlsruhe 76128, Germany 7 https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943071839&doi=10.1111%2fj.1945-5100.2004.tb01133.x&partnerID=40&md5=22c0dc3c1482b077ff53cf95b600ae63 cited By 47 G. Keller T. Adatte W. Stinnesbeck D. Stüben Z. Berner U. Kramar M. Harting article Stöffler20041035 We present and interpret results of petrographic, mineralogical, and chemical analyses of the 1511 in deep ICDP Yaxcopoil-1 (Yax-1 ) drill core, with special emphasis on the impactite units. Using numerical model calculations of the formation, excavation, and dynamic modification of the Chicxulub crater, constrained by laboratory data, a model of the origin and emplacement of the impact formations of Yax-1 and of the impact structure as a whole is derived. The lower part of Yax-1 is formed by displaced Cretaceous target rocks (610 m thick), while the upper part comprises six suevite-type allochthonous breccia units (100 m thick). From the texture and composition of these lithological units and from numerical model calculations, we were able to link the seven distinct impact-induced units of Yax-1 to the corresponding successive phases of the crater formation and modification, which are as follows: 1) transient cavity formation including displacement and deposition of Cretaceous "megablocks;" 2) ground surging and mixing of impact melt and lithic clasts at the base of the ejecta curtain and deposition of the lower suevite right after the formation of the transient cavity; 3) deposition of a thin veneer of melt on top of the lower suevite and lateral transport and brecciation of this melt toward the end of the collapse of the transient cavity (brecciated impact melt rock); 4) collapse of the ejecta plume and deposition of fall-back material from the lower part of the ejecta plume to form the middle suevite near the end of the dynamic crater modification; 5) continued collapse of the ejecta plume and deposition of the upper suevite; 6) late phase of the collapse and deposition of the lower sorted suevite after interaction with the inward flowing atmosphere; 7) final phase of fall-back from the highest part of the ejecta plume and settling of melt and solid particles through the reestablished atmosphere to form the upper sorted suevite; and 8) return of the ocean into the crater after some time and minor reworking of the uppermost suevite under aquatic conditions. Our results are compatible with: a) 180 km and 100 km for the diameters of the final crater and the transient cavity of Chicxulub, respectively, as previously proposed by several authors, and b) the interpretation of Chicxulub as a peak-ring impact basin that is at transition to a multi-ring basin. © Meteoritical Society, 2004. 2004 10.1111/j.1945-5100.2004.tb01128.x Meteoritics and Planetary Science 39 1035-1067 Institut für Mineralogie, Museum fur Naturkunde, Humboldt-Universität zu Berlin, Invalidenstrasse 43, Berlin D-10099, Germany; Institute for Dynamics of Geospheres, Leninsky Prospect 38, Moscow 119334, Russian Federation 7 https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943110343&doi=10.1111%2fj.1945-5100.2004.tb01128.x&partnerID=40&md5=b19e7ace1845c286a4eaf9a68e701e95 cited By 84 D. Stöffler N.A. Artemieva B.A. Ivanov L. Hecht T. Kenkmann R.T. Schmitt R.A. Tagle A. Wittmann article Gelinas20041003 The spatial distribution and amount of material transferred from the bolide involved in the Cretaceous/Tertiary (K/T) event to the target rocks at Chicxulub is still poorly constrained. In this study, Re-Os isotopic analyses of impact melt breccias and lithic clasts from the Yaxcopoil-1 (Yax- 1) borehole were used to determine the distribution and proportion of the bolide component in the target rocks. Because of the much greater concentration of Os in chondritic meteorites compared to the target rocks, little addition of the bolide component would be necessary to greatly perturb the Os concentration and isotopic composition of target rocks. Hence, this is a very sensitive means of examining bolide contributions to the target rocks. For the examined suite of samples, the initial 187OS/188Os ratios vary from 0.19 to 2.3. Conservative mixing calculations suggest that the bolide component comprised as much as approximately 0.1%, by mass, of some samples. Most samples, however, have negligible contributions from the bolide. No samples have Os that is dominated by the bolide component, so for this suite of samples, it is impossible to fingerprint the chemical nature of the bolide using relative abundances of siderophile elements. These results suggest that the bolide did not contribute a significant amount of material to the target rocks. This may, in turn, indicate that most of the bolide was vaporized upon impact or otherwise ejected without mixing with the melt from the target. 2004 10.1111/j.1945-5100.2004.tb00941.x Meteoritics and Planetary Science 39 1003-1008 Isotope Geochemistry Laboratory, Department of Geology, University of Maryland, College Park, MD 20742, United States; Lunar and Planetary Laboratory, University of Arizona, 1629 East University Boulevard, Tucson, AZ 85721, United States; Instituto de Geofísica, Univ. Nacl. Autonoma de Mexico, Coyoacán, D.F. 04510, Mexico 6 https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943066309&doi=10.1111%2fj.1945-5100.2004.tb00941.x&partnerID=40&md5=99fc1ecc30e8782924fdef1c77113b95 cited By 28 A. Gelinas D.A. Kring L. Zurcher J. Urrutia-Fucugauchi O. Morton article Urrutia-Fucugauchi2004843 Results of a detailed paleomagnetic and rock magnetic study of samples of the impact breccia sequence cored in the Yaxcopoil-1 (Yax-1) borehole between about 800 m and 896 m are presented. The Yax-1 breccia sequence occurs from 794.63 m to 894.94 m and consists of redeposited melt-rich, clast-size sorted, fine-grained suevites; melt-rich, no clast-size sorting, medium-grained suevites; coarse suevitic melt agglomerates; coarse melt-rich heterogeneous suevites; brecciated suevites; and coarse carbonate and silicate melt suevites. The low-field susceptibility ranges from -0.3 to 4018 × 10-6 SI, and the NRM intensity ranges from 0.02 mA/m up to 37510 mA/m. In general, the NRM intensity and magnetic susceptibility present wide ranges and are positively correlated, pointing to varying magnetic mineral contents and textures of the melt-rich breccia sequence. The vectorial composition and magnetic stability of NRM were investigated by both stepwise alternating field and thermal demagnetization. In most cases, characteristic single component magnetizations are observed. Both upward and downward inclinations are present through the sequence, and we interpret the reverse magnetization as the primary component in the breccias. Both the clasts and matrix forming the breccia appear to have been subjected to a wide range of temperature/pressure conditions and show distinct rock magnetic properties. An extended interval of remanence acquisition and secondary partial or total remagnetization may explain the paleomagnetic results. © Meteoritical Society, 2004. 2004 10.1111/j.1945-5100.2004.tb00934.x Meteoritics and Planetary Science 39 843-856 Lab. Paleomagnetismo/Geofisica Nucl., Instituto de Geofisica, Univ. Nacional Autonoma Mexico, Coyoacán, Mexico DF 04510, Mexico 6 https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943096576&doi=10.1111%2fj.1945-5100.2004.tb00934.x&partnerID=40&md5=71170e86e0804b5a95a0615973b701dd cited By 16 J. Urrutia-Fucugauchi A.M. Soler-Arechalde M. Rebolledo-Vieyra P. Vera-Sanchez article Popov2004799 Physical properties were determined in a first step on post-impact tertiary limestones from the depth interval of 404-666 m of the Yaxcopoil-1 (Yax-1) scientific well, drilled in the Chicxulub impact crater (Mexico). Thermal conductivity, thermal diffusivity, density, and porosity were measured on 120 dry and water-saturated rocks with a core sampling interval of 2-2.5 m. Non-destructive, non-contact optical scanning technology was used for thermal property measurements including thermal anisotropy and inhomogeneity. Supplementary petrophysical properties (acoustic velocities, formation resisitivity factor, internal surface, and hydraulic permeability) were determined on a selected subgroup of representative samples to derive correlations with the densely measured parameters, establishing estimated depth logs to provide calibration values for the interpretation of geophysical data. Significant short- and long-scale variations of porosity (1-37%) turned out to be the dominant factor influencing thermal, acoustic, and hydraulic properties of this post impact limestone formation. Correspondingly, large variations of thermal conductivity, thermal diffusivity, acoustic velocities, and hydraulic permeability were found. These variations of physical properties allow us to subdivide the formation into several zones. A combination of experimental data on thermal conductivity for dry and water-saturated rocks and a theoretical model of effective thermal conductivity for heterogeneous media have been used to calculate thermal conductivity of mineral skeleton and pore aspect ratio for every core under study. The results on thermal parameters are the necessary basis for the determination of heat flow density, demonstrating the necessity of dense sampling in the case of inhomogeneous rock formations. © Meteoritical Society, 2004. 2004 10.1111/j.1945-5100.2004.tb00930.x Meteoritics and Planetary Science 39 799-812 Moscow State Geol. Prospecting Univ., Moscow, Russian Federation; Department of Applied Geosciences, Technical University, Berlin, Germany; Geophysical Institute, University Karlsruhe, Karlsruhe 76131, Germany 6 https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943074395&doi=10.1111%2fj.1945-5100.2004.tb00930.x&partnerID=40&md5=8969428d578c8eb9dab2d97768c0629e cited By 23 Y. Popov R. Romushkevich I. Bayuk D. Korobkov S. Mayr H. Burkhardt H. Wilhelm article Chapman20041 Near-Earth asteroids (NEAs) have struck the Earth throughout its existence. During epochs when life was gaining a foothold ∼ 4 Ga, the impact rate was thousands of times what it is today. Even during the Phanerozoic, the numbers of NEAs guarantee that there were other impacts, possibly larger than the Chicxulub event, which was responsible for the Cretaceous-Tertiary extinctions. Astronomers have found over 2500 NEAs of all sizes, including well over half of the estimated 1100 NEAs >1 km diameter. NEAs are mostly collisional fragments from the inner half of the asteroid belt and range in composition from porous, carbonaceous- chondrite-like to metallic. Nearly one-fifth of them have satellites or are double bodies. When the international telescopic Spaceguard Survey, which has a goal of discovering 90% of NEAs >1 km diameter, is completed, perhaps as early as 2008, nearly half of the remaining impact hazard will be from land or ocean impacts by bodies 70-600 m diameter. (Comets are expected to contribute only about 1% of the total risk.) The consequences of impacts for civilization are potentially enormous, but impacts are so rare that worldwide mortality from impacts will have dropped to only about 150 per year (averaged over very long durations) after the Spaceguard goal has, presumably, ruled out near- term impacts by 90% of the most dangerous ones; that is, in the mid- range between very serious causes of death (disease, auto accidents) and minor but frightening ones (like shark attacks). Differences in perception concerning this rather newly recognized hazard dominate evaluation of its significance. The most likely type of impact events we face are hyped or misinterpreted predicted impacts or near-misses involving small NEAs. © 2004 Elsevier B.V. All rights reserved. 2004 10.1016/j.epsl.2004.03.004 Earth and Planetary Science Letters 222 1-15 Southwest Research Institute, 1050 Walnut St., Boulder, CO 80302, United States 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-2342457176&doi=10.1016%2fj.epsl.2004.03.004&partnerID=40&md5=2e91c958c587ffbae4a9ff04a0fc52e4 cited By 105 C.R. Chapman article Ames20041145 The 65 Ma Chicxulub impact crater formed in the shallow coastal marine shelf of the Yucatán Platform in Mexico. Impacts into water-rich environments provide heat and geological structures that generate and focus sub-seafloor convective hydrothermal systems. Core from the Yaxcopoil-1 (Yax-1) hole, drilled by the Chicxulub Scientific Drilling Project (CSDP), allowed testing for the presence of an impact-induced hydrothermal system by: a) characterizing the secondary alteration of the 100 m-thick impactite sequence; and b) testing for a chemical input into the lower Tertiary sediments that would reflect aquagene hydrothermal plume deposition. Interaction of the Yax-1 impactites with seawater is evident through redeposition of the suevites (unit 1), secondary alteration mineral assemblages, and the subaqueous depositional environment for the lower Tertiary carbonates immediately overlying the impactites. The least-altered silicate melt composition intersected in Yax-1 is that of a calc-alkaline basaltic andesite with 53.4-56 wt% SiO2 (volatile-free). The primary mineralogy consists of fine microlites of diopside, plagioclase (mainly Ab 47), ternary feldspar (Ab 37 to 77), and trace apatite, titanite, and zircon. The overprinting alteration mineral assemblage is characterized by Mg-saponite, K-montmorillonite, celadonite, K-feldspar, albite, Fe-oxides, and late Ca and Mg carbonates. Mg and K metasomatism resulted from seawater interaction with the suevitic rocks producing smectite-K-feldspar assemblages in the absence of any mixed layer clay minerals, illite, or chlorite. Rare pyrite, sphalerite, galena, and chalcopyrite occur near t he base of the impactites. These secondary alteration minerals formed by low temperature (0-150 °C) oxidation and fixation of alkalis due to the interaction of glass-rich suevite with down-welling seawater in the outer annular trough intersected at Yax-1. The alteration represents a cold, Mg-K-rich seawater recharge zone, possibly recharging higher temperature hydrothermal activity proposed in the central impact basin. Hydrothermal metal input into the Tertiary ocean is shown by elevated Ni, Ag, Au, Bi, and Te concentrations in marcasite and Cd and Ga in sphalerite in the basal 25 m of the Tertiary carbonates in Yax-1. The lower Tertiary trace element signature reflects hydrothermal metal remobilization from a mafic source rock and is indicative of hydrothermal venting of evolved seawater into the Tertiary ocean from an impact-generated hydrothermal convective system. © Meteoritical Society, 2004. Printed in USA. 2004 10.1111/j.1945-5100.2004.tb01134.x Meteoritics and Planetary Science 39 1145-1167 Natural Resources Canada, Geological Survey of Canada, 601 Booth Street, Ottawa, Ont. K1A 0E8, Canada; Mineralogical Consultant, 15 Scotia Place, Ottawa, Ont. K1S 0W2, Canada; Geo Eco Arc Research, 16305 St Mary's Church Road, Aquasco, MD 20608, United States; Lunar and Planet Science Inst., Houston, TX 77058, United States 7 https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943104871&doi=10.1111%2fj.1945-5100.2004.tb01134.x&partnerID=40&md5=55f7d4e441994ef03b425146cf6d6fb3 cited By 37 D.E. Ames I.M. Kjarsgaard K.O. Pope B. Dressler M. Pilkington article Bell20041089 Seismic data across the offshore half of the Chicxulub impact crater reveal a 145 km-diameter post-impact basin to be a thickening of Tertiary sediment, which thickens by ∼0.7 sec from the basin margin to the basin center. The basin existed long after the impact and was gradually infilled to its current flat surface. A suite of seismic horizons within the impact basin have been picked on four reflection lines across the crater. They reveal that the western and northwestern parts of the impact basin were filled first. Subsequently, there was a dramatic change in the depositional environment, indicated by an unconformable surface that can be mapped across the entire basin..A prograding shelf sequence downlaps onto this unconformity in the eastern basin. The seismic stratigraphic relationships suggest a marine regression, with sedimentation becoming gradually more passive as sediments fill the eastern part of the impact basin. The central and northeastern parts of the basin are filled last. The onshore hole Yaxcopoil-1 (Yax-1), which was drilled on the flanks of the southern basin, has been projected onto the offshore seismic data to the west of the crater center. Using dates obtained from this onshore well and regional data, approximate ages have been placed on the most significant horizons in the offshore seismic data. Our preliminary interpretation is that the western and northwestern basins were almost entirely filled by 40 Ma and that the marine regression observed in the eastern basin is early Miocene in age. Offshore seismic stratigraphic analyses and onshore data within Yax-1 suggest that the early Paleocene is highly attenuated across the impact basin. The Mesozoic section appears to be €1 km thicker offshore than onshore. We calculate that, given this offshore thickening, the volume of Mesozoic rocks that have been excavated, melted, or vaporized during impact is around 15% larger than expected from calculations that assume the offshore thickness is equal to that onshore. This has significant consequences for any environmental calculations. The current offset between the K-T boundary outside and inside the crater is ∼700 m. However, infilling of basins with sediments is usually accompanied by subsidence, and immediately following the impact, the difference would have been smaller. We calculate the original topographic offset on the K-T boundary to have been between 450 and 700 m, which is in agreement with depth-diameter scaling laws for a mixed target. © Meteoritical Society, 2004. 2004 10.1111/j.1945-5100.2004.tb01130.x Meteoritics and Planetary Science 39 1089-1098 Department of Earth Science/Eng., Imperial College, London SW7 2AZ, United Kingdom; Department of Geology/Geological Eng, Colorado School of Mines, Colorado 80401, United States 7 https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943056939&doi=10.1111%2fj.1945-5100.2004.tb01130.x&partnerID=40&md5=2d7b3c7a28700c05208022829a65c4e9 cited By 33 C. Bell J.V. Morgan G.J. Hampson B. Trudgill article Kenkmann20041069 As part of the ICDP Chicxulub Scientific Drilling Project, the Yaxcopoil-1 (Yax-1) bore hole was drilled 60 km south-southwest of the center of the 180 km-diameter Chicxulub impact structure down to depth of 1511 m. A sequence of 615 m of deformed Cretaceous carbonates and sulfates was recovered below a 100 m-thick unit of suevitic breccias and 795 m of post-impact Tertiary rocks. The Cretaceous rocks are investigated with respect to deformation features and shock metamorphism to better constrain the deformational overprint and the kinematics of the cratering process. The sequence displays variable degrees of impact-induced brittle damage and post-impact brittle deformation. The degree of tilting and faulting of the Cretaceous sequence was analyzed using 360°-core scans and dip-meter log data. In accordance with lithological information, these data suggest that the sedimentary sequence represents a number of structural units that are tilted and moved with respect to each other. Three main units and nine sub-units were discriminated. Brittle deformation is most intense at the top of the sequence and at 1300-1400 m. Within these zones, suevitic dikes, polymict clastic dikes, and impact melt rock dikes occur and may locally act as decoupling horizons. The degree of brittle deformation depends on lithology; massive dolomites are affected by penetrative faulting, while stratified calcarenites and bituminous limestones display localized faulting. The deformation pattern is consistent with a collapse scenario of the Chicxulub transient crater cavity. It is believed that the Cretaceous sequence was originally located outside the transient crater cavity and eventually moved downward and toward the center to its present position between the peak ring and the crater rim, thereby separating into blocks. Whether or not the stack of deformed Cretaceous blocks was already displaced during the excavation process remains an open question. The analysis of the deformation microstructure indicates that a shock metamorphic overprint is restricted to dike injections with an exception of the so called "paraconglomerate." Abundant organic matter in the Yax-1 core was present before the impact and was mobilized by impact-induced heating and suggests that &gt;12 km3 of organic material was excavated during the cratering process. Meteoritical Society, 2004. 2004 10.1111/j.1945-5100.2004.tb01129.x Meteoritics and Planetary Science 39 1069-1088 Institut für Mineralogie, Museum für Naturkunde, Humboldt Universität Berlin, Invalidenstrasse 43, Berlin 10115, Germany 7 https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943060965&doi=10.1111%2fj.1945-5100.2004.tb01129.x&partnerID=40&md5=86492abe071146954b7763a9b059b28e cited By 30 T. Kenkmann A. Wittmann D. Scherler article Bauluz2004209 Study by transmission electron microscopy of samples from the Cretaceous-Tertiary (K-T) boundary clay at Flaxbourne River and Woodside Creek, New Zealand, has revealed the occurrence of nanometer-sized meteorite impact-derived glass. The average glass composition is exceptionally Ca-rich and is distinct from other glass found on Earth, apart from glass inferred to be of impact origin at Mexican and Haitian K-T sites. The glass shards are partially altered to montmorillonite-like smectite, with the dominant interlayer cation, Ca, reflecting the composition of the parent glass. The data imply a heterogeneous global distribution in composition of K-T boundary impact glass: Si-rich and Ca-rich in Mexico and Haiti, Si-rich in Denmark, and Ca-rich in New Zealand. This heterogeneous distribution may relate to dispersal processes similar to those used to account for the asymmetric distribution of clastic debris from the Chicxulub impact site. However, recent discovery of an impact crater of K-T boundary age in Ukraine raises the possibility of impact clusters which produce material of heterogeneous composition. © 2004 Elsevier B.V. All rights reserved. 2004 10.1016/S0012-821X(04)00011-1 Earth and Planetary Science Letters 219 209-219 Cristalografia y Mineralogía, Depto. de Ciencias de la Tierra, Universidad de Zaragoza, Zaragoza 50009, Spain; Department of Geological Sciences, The University of Michigan, Ann Arbor, MI 48109-1063, United States; Inst. of Geol./Nuclear Sciences, P.O. Box 30-368, Lower Hutt, New Zealand 3-4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-1542644777&doi=10.1016%2fS0012-821X%2804%2900011-1&partnerID=40&md5=11361bcea550fd35556d1fe2c9af9d0b cited By 17 B. Bauluz D.R. Peacor article Urrutia-Fucugauchi2004787 2004 10.1111/j.1945-5100.2004.tb00928.x Meteoritics and Planetary Science 39 787-790 Instituto de Geofisica, Univ. Nacl. Autonoma de Mexico, Mexico City, Coyoacán 04510, Mexico; Earth Sciences and Engineering, Imperial College London, London SW7 2AZ, United Kingdom; Natural History Museum, Humboldt University, Berlin D-10099, Germany; Department of Geology, Vrije Universiteit Brusse, Pleinaan 2, Brussels B-1050, Belgium 6 https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943079941&doi=10.1111%2fj.1945-5100.2004.tb00928.x&partnerID=40&md5=4cbc53cc65325240641ba4cf421427d4 cited By 72 J. Urrutia-Fucugauchi J. Morgan D. Stöffler P. Claeys article Rebolledo-Vieyra2004821 We report the magnetostratigraphy of the sedimentary sequence between the impact breccias and the post-impact carbonate sequence conducted on samples recovered by Yaxcopoil-1 (Yax-1). Samples of impact breccias show reverse polarities that span up to ∼56 cm into the post-impact carbonate lithologies. We correlate these breccias to those of PEMEX boreholes Yucatán-6 and Chicxulub-1, from which we tied our magnetostratigraphy to the radiometric age from a melt sample from the Yucatán-6 borehole. Thin section analyses of the carbonate samples showed a significant amount of dark minerals and glass shards that we identified as the magnetic carriers; therefore, we propose that the mechanism of magnetic acquisition within the carbonate rocks for the interval studied is detrital remanent magnetism (DRM). With these samples, we constructed the scale of geomagnetic polarities where we find two polarities within the sequence, a reverse polarity event within the impact breccias and the base of the post-impact carbonate sequence (up to 794.07 m), and a normal polarity event in the last ∼20 cm of the interval studied. The polarities recorded in the sequence analyzed are interpreted to span from chron 29r to 29n, and we propose that the reverse polarity event lies within the 29r chron. The magnetostratigraphy of the sequence studied shows that the horizon at 794.11 m deep, interpreted as the K/T boundary, lies within the geomagnetic chron 29r, which contains the K/T boundary. © Meteoritical Society, 2004. 2004 10.1111/j.1945-5100.2004.tb00932.x Meteoritics and Planetary Science 39 821-829 Lab. Scis. du Climat/l'Environnement, Unite de Recherche Mixte CNRS-CEA, Gif-sur-Yvette, France; Laboratorio de Paleomagnetismo, Instituto de Geofisica, UNAM, Coyoacán, Mexico City, Mexico 6 https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943080587&doi=10.1111%2fj.1945-5100.2004.tb00932.x&partnerID=40&md5=d9e2a908451b590360715ded1e161272 cited By 30 M. Rebolledo-Vieyra J. Urrutia-Fucugauchi article Nelson2004 2004 Meteoritics and Planetary Science 39 A76 University of New Mexico, Institute of Meteoritics, Albuquerque, NM 87131, United States; Department of Earth/Planetary Sci., Albuquerque, NM 87131, United States SUPPL. https://www.scopus.com/inward/record.uri?eid=2-s2.0-4043083631&partnerID=40&md5=44a7d040414cb1cf4d226603425cbc50 cited By 1 M.J. Nelson H.E. Newsom C.K. Shearer F.J.M. Rietmeijer article Stinnesbeck20041042 CSDP core Yaxcopoil-1 was drilled to a depth of 1,511 m within the Chicxulub crater. An organic-rich marly limestone near the base of the hole (1,495 to 1,452 m) was deposited in an open marine shelf environment during the latest Cenomanian (uppermost Rotalipora cushmani zone). The overlying sequence of limestones, dolomites and anhydrites (1,495 to 894 m) indicates deposition in various carbonate platform environments (e.g., sabkhas, lagoons). A 100-m-thick suevite breccia (894-794 m) identifies the Chicxulub impact event. Above the suevite breccia is a dolomitic limestone with planktic foraminiferal assemblages indicative of Plummerita hantkeninoides zone CF1, which spans the last 300 ky of the Maastrichtian. An erosional surface 50 cm above the breccia/dolomite contact marks the K/T boundary and a hiatus. Limestones above this contact contain the first Tertiary planktic foraminifera indicative of an upper P. eugubina zone P1a(2) age. Another hiatus 7 cm upsection separates zone P1a(2) and hemipelagic limestones of planktic foraminiferal Zone P1c. Planktic foraminiferal assemblages of Zone Plc to P3b age are present from a depth of 794.04 up to 775 m. The Cretaceous carbonate sequence appears to be autochthonous, with a stratigraphic sequence comparable to late Cretaceous sediments known from outside the Chicxulub crater in northern and southern Yucatan, including the late Cenomanian organic-rich marly limestone. There is no evidence that these sediments represent crater infill due to megablocks sliding into the crater, such as major disruption of sediments, chaotic changes in lithology, overturned or deep dipping megablocks, major mechanical fragmentation, shock or thermal alteration, or ductile deformation. Breccia units that are intercalated in the carbonate platform sequence are intraformational in origin (e.g., dissolution of evaporites) and dykes are rare. Major disturbances of strata by the impact therefore appear to have been confined to within less than 60 km from the proposed impact center. Yaxcopoil-1 may be located outside the collapsed transient crater cavity, either on the upper end of an elevated and tilted horst of the terrace zone, or even outside the annular crater cavity. The Chicxulub site thus records a large impact that predates the K/T boundary impact and mass extinction. © Springer-Verlag 2004. 2004 10.1007/s00531-004-0431-6 International Journal of Earth Sciences 93 1042-1065 Geologisches Institut, Universität Karlsruhe, 76128 Karlsruhe, Germany; Department of Geosciences, Princeton University, Princeton, NJ 08544, United States; Geological Institute, University of Neuchâtel, 2007 Neuchâtel, Switzerland; Institut fur Mineralogie/Geochemie, Universität Karlsruhe, 76128 Karlsruhe, Germany 6 https://www.scopus.com/inward/record.uri?eid=2-s2.0-10044288403&doi=10.1007%2fs00531-004-0431-6&partnerID=40&md5=2b968bbd503abe2f17ec5cc32b49b720 cited By 30 W. Stinnesbeck G. Keller T. Adatte M. Harting D. Stüben G. Istrate U. Kramar article Tuchscherer2004955 Approximately 100 m of impactites were retrieved from the ICDP borehole Yaxcopoil-1 (Yax-1), located ∼60 km south-southwest from the center of the Chicxulub impact crater on the Yucatán Peninsula of Mexico. Here, we characterize and discuss this impact breccia interval according to its geochemical characteristics. Chemical analysis of samples from all five recognized breccia units reveals that the impactites are of heterogeneous composition with regard to both major and trace elements at the single sample (8-16 cm3) scale. This is primarily due to a strong mixing relationship between carbonate and silicate fractions. However, averaged compositions for suevitic units 1 to 3 are similar, and the silicate fraction (after removal of the carbonate component) indicates thorough mixing and homogenization. Analysis of the green melt breccia horizon, unit 4, indicates that it contains a distinct mafic component. Large brown melt particles (in units 2, 3, and 4) represent a mixture of feldspathic and mafic components, with high CaO abundances. Unit 5 shows the greatest compositional diversity, with highly variable abundances of SiO2, CaO, and MgO. Inter-sample heterogeneity is the result of small sample size combined with inherent heterogeneous lithological compositions, highly variable particle size of melt and lithic components, and post-depositional alteration. In contrast to samples from the Y6 borehole from closer to the center of the structure, Yax-1 impactites have a strong carbonate component. Elevated loss on ignition, Rb, and Cs contents in the upper two impactite units indicate strong interaction with seawater. The contents of the siderophile elements, including Ni, Co, Ir, and Cr, do not indicate the presence of a significant extraterrestrial component in the Yax-1 impactites. © Meteoritical Society, 2004. 2004 10.1111/j.1945-5100.2004.tb00939.x Meteoritics and Planetary Science 39 955-978 Impact Cratering Research Group, School of Geosciences, University of the Witwatersrand, Private Bag 3, Johannesburg 2050, South Africa; Department of Geological Sciences, University of Vienna, Althanstrasse 14, Vienna A-1090, Austria 6 https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943069009&doi=10.1111%2fj.1945-5100.2004.tb00939.x&partnerID=40&md5=d66521d4bfb9f98ead183089abd39d92 cited By 20 M.G. Tuchscherer M.U. Reimold C. Koeberl R.L. Gibson article Wittman2004931 Petrographic descriptions of three dike breccia lithologies from drill core Yaxcopoil-1 (Yax-1) are presented. They occur within allochthonous units of displaced sedimentary megablocks of the Chicxulub impact structure. The suevitic dike breccias are the uppermost dike lithology. They contain melt rock particles and melt injections into the dike groundmass. Shock features occur ubiquitously and indicate a strong thermal annealing. Flow textures suggest a highly energetic emplacement process, possibly during the excavation stage as a ground-surge related deposit. The impact melt rock dikes are present in a strongly brecciated megablock interval as flow textured, anastomozing veinlets of impact melt rock that were altered to clay minerals. The melt impregnated a dolomitic host rock, indicating a low viscosity and, thus, high initial temperatures. Brecciation of the impact melt rock dikes occurred while they were still below the glass transition temperature, suggesting that dynamic conditions prevailed shortly after the emplacement process. Major element data indicates that the impact melt rock dikes differ in composition from the homogenized impact melt rock of Chicxulub. This could point to an emplacement during the late compression or early excavation stages of cratering. The clastic polymict dike breccias are coeval with pervasive brittle fracturing of the host rocks. They bear clasts including some crystalline basement and possible melt rock particles in a fine-grained dolomite matrix with turbulent flow textures. Fabric and texture indicate a granular flow at ambient pressures. Such conditions could be envisaged for the excavation phase while the transient cavity grew and fractures opened. © Meteoritical Society, 2004. 2004 10.1111/j.1945-5100.2004.tb00938.x Meteoritics and Planetary Science 39 931-954 Institut für Mineralogie, Museum für Naturkunde, Humboldt Universität Berlin, Invalidenstrasse 43, Berlin 10115, Germany 6 https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943104872&doi=10.1111%2fj.1945-5100.2004.tb00938.x&partnerID=40&md5=28665c60f2cf39155d523979d89ace62 cited By 35 A. Wittman T. Kenkmann R.T. Schmitt L. Hecht D. Stöffler article Pilkington2004831 Core from the Yaxcopoil-1 (Yax-1) hole, drilled as a result of the Chicxulub Scientific Drilling Project (CSDP), has been analyzed to investigate the relationship between opaque mineralogy and rock magnetic properties. Twenty one samples of suevite recovered from the depth range 818-894 m are generally paramagnetic, with an average susceptibility of 2000 × 10-6 SI and have weak remanent magnetization intensities (average 0.1 A/m). The predominant magnetic phase is secondary magnetite formed as a result of low temperature (&lt;15 °C alteration. It occurs in a variety of forms, including vesicle infillings associated with quartz and clay minerals and fine aggregates between plagioclase/diopside laths in the melt. Exceptional magnetic properties are found in a basement clast (metamorphosed quartz gabbro), which has a susceptibility of &gt;45000 × 10-6 SI and a remanent magnetization of 77.5 A/m. Magnetic mafic basement clasts are a common component in the Yax-1 impactite sequence. The high susceptibility and remanence in the mafic basement clasts are caused by the replacement of amphiboles and pyroxenes by an assemblage with fine &lt;1 μm magnetite, ilmenite, K-feldspar, and stilpnomelane. Replacement of the mafic minerals by the magnetic alteration assemblage occurred before impact. Similar alteration mechanisms, if operative within the melt sheet, could explain the presence of the high amplitude magnetic anomalies observed at Chicxulub. © Meteoritical Society, 2004. 2004 10.1111/j.1945-5100.2004.tb00933.x Meteoritics and Planetary Science 39 831-841 Geological Survey of Canada, 615 Booth Street, Ottawa, Ont. K1A 0E9, Canada; Department of Geology and Geophysics, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada 6 https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943108811&doi=10.1111%2fj.1945-5100.2004.tb00933.x&partnerID=40&md5=cf6a4f603ed2a7e5186c40995ae0ac2d cited By 14 M. Pilkington D.E. Ames A.R. Hildebrand article Smit20041113 The transition from impact to post-impact rocks in the Yaxcopoil-1 (Yax-1) core is marked by a 2 cm-thick clay layer characterized by dissolution features. The clay overlies a 9 cm-thick hardground, overlying a 66 cm-thick crossbedded unit, consisting of dolomite sandstone alternating with thin micro-conglomerates layers with litho- and bioclasts and the altered remains of impact glass, now smectite. The micro-conglomerates mark erosion surfaces. Microprobe and backscatter SEM analysis of the dolomite rhombs show an early diagenetic, complex-zoned, idiomorphic overgrowth, with Mn-rich zones, possibly formed by hot fluids related to cooling melt sheet in the crater. The pore spaces are filled with several generations of coelestite, barite, K-feldpar, and sparry calcite. XRF core scanning analysis detected high Mn values in the crossbedded sediments but no anomalous enrichment of the siderophile elements Cr, Co, Fe, and Ni in the clay layer. Shocked quartz occurs in the crossbedded unit but is absent in the clay layer. The basal Paleocene marls are strongly dissolved and do not contain a basal Paleocene fauna. The presence of a hardground, the lack of siderophile elements, shocked quartz, or Ni-rich spinels in the clay layer, and the absence of basal Paleocene biozones PO and Pa all suggest that the top of the ejecta sequence and a significant part of the lower Paleocene is missing. Due to the high energy sedimentation infill, a hiatus at the top of the impactite is not unexpected, but there is nothing in the biostratigraphy, geochemistry, and petrology of the Yax-1 core that can be used to argue against the synchroneity of the end-Cretaceous mass-extinctions and the Chicxulub crater. © Meteoritical Society, 2004. 2004 10.1111/j.1945-5100.2004.tb01132.x Meteoritics and Planetary Science 39 1113-1126 Faculty of Earth and Life Sciences, Vrije Universiteit, de Boelaan 1085, Amsterdam HV 1081, Netherlands; NIOZ, P.O. Box 59, Texel, Den Burg AB NL-1790, Netherlands 7 https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943099405&doi=10.1111%2fj.1945-5100.2004.tb01132.x&partnerID=40&md5=a8d32210e24b3aeef1ac16617ef3a559 cited By 40 J. Smit S. Van Der Gaast W. Lustenhouwer article Alegret200459 Sediments recovered at lower bathyal ODP Site 1049 on Blake Nose (Northwestern Atlantic) offer an opportunity to study environmental changes at the Cretaceous/Paleogene (K/P) boundary relatively close to the Chicxulub impact structure on the Yucatan peninsula, Mexico. In Hole 1049C, the boundary is located at the base of a 9-cm-thick layer with abundant spherules, considered to be impact ejecta. Uppermost Maastrichtian oozes below, and lowermost Danian pelagic oozes above the spherule-bed contain well-preserved bathyal benthic foraminifera. The spherule-bed itself, in contrast, contains a mixture of shallow (neritic) and deeper (bathyal) species, and specimens vary strongly in preservation. This assemblage was probably formed by reworking and down-slope transport triggered by the K/P impact. Across the spherule-bed (i.e., the K/P boundary) only ∼7% of benthic foraminiferal species became extinct, similar to the low extinction rates of benthic foraminifera worldwide. Quantitative analysis of benthic foraminiferal assemblages and morphogroups in the >63-μm size fraction indicates a relatively eutrophic, stable environment during the latest Maastrichtian, interrupted by a sudden decrease in the food supply to the benthos at the K/P boundary and a decrease in diversity of the faunas, followed by a stepped recovery during the earliest Danian. The recovery was probably linked to the gradual recovery of surface-dwelling primary producers. © 2004 Elsevier B.V. All rights reserved. 2004 10.1016/j.palaeo.2004.02.028 Palaeogeography, Palaeoclimatology, Palaeoecology 208 59-83 Department of Earth Sciences, University College London, London WC1E-6BT, United Kingdom; Dept. of Earth and Environ. Sciences, Wesleyan University, Middletown, CT 06459-0139, United States; Department of Geology and Geophysics, Ctr. for the Study of Global Change, Yale University, New Haven, CT 06520-8109, United States 1-2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-2642518967&doi=10.1016%2fj.palaeo.2004.02.028&partnerID=40&md5=03361b568aaa4b30b2996ca12cf22a7b cited By 56 L. Alegret E. Thomas article Vermeesch20041019 The Chicxulub crater in Mexico is a nearly pristine example of a large impact crater. Its slow burial has left the central impact basin intact, within which there is an apparently uneroded topographic peak ring. Its burial, however, means that we must rely on drill holes and geophysical data to interpret the crater form. Interpretations of crater structures using geophysical data are often guided by numerical modeling and observations at other large terrestrial craters. However, such endeavors are hindered by uncertainties in current numerical models and the lack of any obvious progressive change in structure with increasing crater size. For this reason, proposed structural models across Chicxulub remain divergent, particularly within the central crater region, where the deepest well is only ∼1.6 km deep. The shape and precise location of the stratigraphic uplift are disputed. The spatial extent and distribution of the allogenic impact breccias and melt rocks remain unknown, as do the lithological nature of the peak ring and the mechanism for its formation. The objective of our research is to provide a well-constrained 3D structural and lithological model across the central region of the Chicxulub crater that is consistent with combined geophysical data sets and drill core samples. With this in mind, we present initial physical property measurements made on 18 core samples from the Yaxcopoil-1 (Yax-1) drill hole between 400 and 1500 m deep and present a new density model that is in agreement with both the 3D velocity and gravity data. Future collation of petrophysical and geochemical data from Yax-1 core, as well as further seismic surveys and drilling, will allow us to calibrate our geophysical models-assigning a suite of physical properties to each lithology. An accurate 3D model of Chicxulub is critical to our understanding of large craters and to the constraining of the environmental effects of this impact. © Meteoritical Society, 2004. Printed in USA. 2004 10.1111/j.1945-5100.2004.tb01127.x Meteoritics and Planetary Science 39 1019-1034 Department of Earth Science/Eng., Imperial College, London SW7 2AZ, United Kingdom 7 https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943072494&doi=10.1111%2fj.1945-5100.2004.tb01127.x&partnerID=40&md5=d5d78f1b1961014bc441408dc52bbe3d cited By 38 P.M. Vermeesch J.V. Morgan article Rowe20041223 Studies of large terrestrial impact craters indicate that post-impact hydrothermal activity is a likely consequence of the crustal deformation and heating induced by such events. In the case of the Chicxulub basin, where marine conditions were re-established soon after the impact, significant fluxing of seawater-through the crust and hydrothermal venting into the water column might be anticipated. We have carried out geochemical analyses of Tertiary carbonate sediments within the Yaxcopoil-1 (Yax-1) drill hole to test for evidence of such post-impact hydrothermal circulation. Hydrothermal activity is most likely to be found close to thick layers of melt rock inside the collapsed transient cavity, and it is estimated that Yax-1 is located ∼20 km outside this cavity. Consequently, the most likely signature of hydrothermal venting into the water column would be geochemical anomalies attributable to fallout of suspended particulate matter from a submarine hydrothermal plume. Samples of Tertiary biomicrites from depths of 794.01 to 777.02 m have high concentrations of manganese, iron, phosphorous, titanium, and aluminium and low iron/manganese ratios relative to samples from higher in the stratigraphic succession. This geochemical anomaly decreases' fairly systematically between 793.13 m and 777.02 m, above which an abrupt change in geochemistry is observed. A mass balance calculation suggests that the anomaly is unlikely to be the result of a decreasing detrital input to the carbonate sediments and the nature of the element enrichments is consistent with expectations for fallout from a distal hydrothermal plume. We conclude that a post-impact hydrothermal system did develop at Chicxulub, which led to the expulsion of hydrothermal fluids into the Tertiary water column. Preliminary biostratigraphic and magnetostratigraphic dating on Yax-1 core suggest that this hydrothermal activity lasted for at least 300 ka. © Meteoritical Society, 2004. Printed in USA. 2004 10.1111/j.1945-5100.2004.tb01138.x Meteoritics and Planetary Science 39 1223-1231 Department of Earth Science/Eng., Imperial College, London SW7 2AZ, United Kingdom 7 https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943111707&doi=10.1111%2fj.1945-5100.2004.tb01138.x&partnerID=40&md5=04ae8d87f1d6c6a6316c03abbd2d6606 cited By 13 A.J. Rowe J.J. Wilkinson B.J. Coles J.V. Morgan article Hecht20041169 Petrographical and chemical analysis of melt particles and alteration minerals of the about 100 m-thick suevitic sequence at the Chicxulub Yax-1 drill core was performed. The aim of this study is to determine the composition of the impact melt, the variation between different types of melt particles, and the effects of post-impact hydrothermal alteration. We demonstrate that the compositional variation between melt particles of the suevitic rocks is the result of both incomplete homogenization of the target lithologies during impact and subsequent post-impact hydrothermal alteration. Most melt particles are andesitic in composition. Clinopyroxene-rich melt particles possess lower SiO2 and higher CaO contents. These are interpreted by mixing of melts from the silicate basement with overlying carbonate rocks. Multi-stage post-impact hydrothermal alteration involved significant mass transfer of most major elements and caused further compositional heterogeneity between melt particles. Following backwash of seawater into the crater, palagonitization of glassy melt particles likely caused depletion of SiO2, A12O3, CaO, Na2O, and enrichment of K2O and FeOtot during an early alteration stage. Since glass is very susceptible to fluid-rock interaction, the state of primary crystallization of the melt particles had a significant influence on the intensity of the post-impact hydrothermal mass transfer and was more pronounced in glassy melt particles than in well-crystallized particles. In contrast to other occurrences of Chicxulub impactites, the Yax-1 suevitic rocks show strong potassium metasomatism with hydrothermal K-feldspar formation and whole rock K2O enrichment, especially in the lower unit of the suevitic sequence. A late stage of hydrothermal alteration is characterized by precipitation of silica, analcime, and Na-bearing Mg-rich smectite, among other minerals. This indicates a general evolution from a silica-undersaturated fluid at relatively high potassium activities at an early stage toward a silica-oversaturated fluid at relatively high sodium activities at later stages in the course of fluid rock interaction. © Meteoritical Society, 2004. Printed in USA. 2004 10.1111/j.1945-5100.2004.tb01135.x Meteoritics and Planetary Science 39 1169-1186 Institut für Mineralogie, Museum für Naturkunde, Humboldt-Universität zu Berlin, Invalidenstrasse 43, Berlin D-10115, Germany 7 https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943087085&doi=10.1111%2fj.1945-5100.2004.tb01135.x&partnerID=40&md5=4f9af36fad91b1b9d7b9217ea1308ba7 cited By 59 L. Hecht A. Wittmann R.-T. Schmitt D. Stöffler article Goto20041233 The possibility of ocean water invasion into the Chicxulub crater following the impact at the Cretaceous/Tertiary boundary was investigated based on examination of an impactite between approximately 794.63 and 894.94 m in the Yaxcopoil-1 (Yax-1) core. The presence of cross lamination in the uppermost part of the impactite suggests the influence òf an oçean current at least during the sedimentation of this interval. Abundant occurrence of nannofossils of late Campanian to early Maastrichtian age in the matrices of samples from the upper part of the impactite suggests that the carbonate sediments deposited on the inner rim margin and outside the crater were eroded and transported into the crater most likely by ocean water that invaded the crater after its formation. The maximum grain size of limestone lithics and vesicular melt fragments, and grain and bulk chemical compositions show a cyclic variation in the upper part of the impactite. The upward fining grain size and the absence of erosional contact at the base of each cycle suggest that the sediments were derived from resuspension of units elsewhere in the crater, most likely by high energy currents association with ocean water invasion. © Meteoritical Society, 2004. Printed in USA. 2004 10.1111/j.1945-5100.2004.tb01139.x Meteoritics and Planetary Science 39 1233-1247 Department of Earth/Planet Science, The University of Tokyo, 7-3-1 Hongo, Tokyo 113 0033, Japan; Department of Geosciences, Pennsylvania State University, University Park, PA 16802, United States; Department of Earth Sciences, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan; Department of Complexity Sci./Eng., The University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan 7 https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943065105&doi=10.1111%2fj.1945-5100.2004.tb01139.x&partnerID=40&md5=763cf7137cd4416d8e213bc91b7a49ed cited By 43 K. Goto R. Tada E. Tajika T.J. Bralower T. Hasegawa T. Matsui article Tuchscherer2004899 The ICDP Yaxcopoil-1 (Yax-1) borehole located 60 km south-southwest of the center of the Chicxulub impact structure intercepted an interval of allogenic impactites (depth of 795-895 m). Petrographic analysis of these impactites allows them to be differentiated into five units based on their textural and modal variations. Unit 1 (795-922 m) comprises an apparently reworked, poorly sorted and graded, fine-grained, clast-supported, melt fragment-bearing suevitic breccia. The interstitial material, similar to units 2 and 3, is permeated by numerous carbonate veinlets. Units 2 (823-846 m) and 3 (846-861 m) are groundmass-supported breccias that comprise green to variegated angular and fluidal melt particles. The groundmass of units 2 and 3 comprises predominantly fine-grained calcite, altered alkali element-, Ca-, and Si-rich cement, as well as occasional lithic fragments. Unit 4 (861-885 m) represents a massive, variably devitrified, and brecciated impact melt rock. The lowermost unit, unit 5 (885-895 m), comprises highly variable proportions of melt rock particles (MRP) and lithic fragments in a fine-grained, carbonate-dominated groundmass. This groundmass could represent either a secondary hydrothermal phase or a carbonate melt phase, or both. Units 1 and 5 contain well-preserved foraminifera fossils and a significantly higher proportion of carbonate clasts than the other units. All units show diagnostic shock deformation features in quartz and feldspar clasts. Our observations reveal that most felsic and all mafic MRP are altered. They register extensive K-metasomatism. In terms of emplacement, we suggest that units 1 to 3 represent fallout suevite from a collapsing impact plume, whereby unit 1 was subsequently reworked by resurging water. Unit 4 represents a coherent impact melt body, the formation of which involved a significant proportion of crystalline basement. Unit 5 is believed to represent an initial ejecta/ground-surge deposit. © Meteoritical Society, 2004. 2004 10.1111/j.1945-5100.2004.tb00937.x Meteoritics and Planetary Science 39 899-930 Impact Cratering Research Group, School of Geosciences, University of the Witwatersrand, Private Bag 3, Johannesburg 2050, South Africa; Department of Geological Sciences, University of Vienna, Althanstrasse 14, Vienna A-1090, Austria; Council for Geosciences, Private Bag X112, Pretoria 0001, South Africa 6 https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943099912&doi=10.1111%2fj.1945-5100.2004.tb00937.x&partnerID=40&md5=7647a561dbe59a29c7c5c27258ca9c70 cited By 33 M.G. Tuchscherer W.U. Reimold C. Koeberl R.L. Gibson D. Bruin article Lüders20041187 Fluid inclusions studies in quartz and calcite in samples from the ICDP-Chicxulub drill core Yaxcopoil-1 (Yax-1) have revealed compelling evidence for impact-induced hydrothermal alteration. Fluid circulation through the melt breccia and the underlying sedimentary rocks was not homogeneous in time and space. The formation of euhedral quartz crystals in vugs hosted by Cretaceous limestones is related to the migration of hot (>200 °C), highly saline, metal-rich, hydrocarbon-bearing brines. Hydrocarbons present in some inclusions in quàrtz are assumed to derive from cracking of pre-impact organic matter. The center of the crater is assumed to be the source of the hot quartz-forming brines. Fluid inclusions in abundant newly-formed calcite indicate lower cyrstallization temperatures (75-100 °C). Calcite crystallization is likely related to a later stage of hydrothermal alteration. Calcite precipitated from saline fluids, most probably from formation water. Carbon and oxygen isotope compositions and REE distributions in calcites and carbonate host rocks suggest that the calcite-forming fluids have achieved close equilibrium conditions with the Cretaceous limestones. The precipitation of calcite may be related to the convection of local pore fluids, possibly triggered by impact-induced conductive heating of the sediments. © Meteoritical Society, 2004. Printed in USA. 2004 10.1111/j.1945-5100.2004.tb01136.x Meteoritics and Planetary Science 39 1187-1197 GeoForschungsZentrum Potsdam, Telegrafenberg, Potsdam D-14473, Germany; Hamburger Synchrotronstrahlungslabor, Deutsches Elektronen-Synchrotron, Notkestrasse 85, Hamburg D-22603, Germany 7 https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943098783&doi=10.1111%2fj.1945-5100.2004.tb01136.x&partnerID=40&md5=520fdc27870cc4fa13b859b134d7e38f cited By 33 V. Lüders K. Rickers article https://doi.org/10.1111/j.1945-5100.2004.tb01131.x Abstract The Yaxcopoil-1 (Yax-1) drill hole comprises Cretaceous limestones and calcarenites, the K/P boundary cocktail unit (including impact breccia), and a Danian marly clay layer overlain by calcareous marls. The biostratigraphy, paleobathymetry, and environmental turnover across the K/P interval were inferred after analyzing the planktic and benthic foraminiferal assemblages. The Cretaceous samples only contain a few poorly preserved planktic foraminifera of a middle Campanian to Maastrichtian age, while low-diversity benthic foraminiferal assemblages suggest a sufficient nutrient supply to the sea floor and a shallow neritic, occasionally stressed environment. The impact breccia and the redeposited suevite are overlain by a 46 cm-thick dolomitic calcareous sandstone unit that contains scarce, reworked planktic foraminiferal specimens. This unit probably represents the uppermost part of the initial infill of the crater. The uppermost centimeters of this unit are bioturbated, and its top represents a hiatus that spans at least the G. cretacea, Pv. eugubina, and part of the P. pseudobulloides biozones. This unit is overlain by a 3–4 cm-thick marly clay layer that represents a condensed layer. Benthic foraminiferal assemblages suggest a low food supply to the sea floor and environmental instability during the deposition of the marly clay layer. The increase in diversity of the assemblages indicates that the environmental conditions improved and stabilized from the G. compressa biozone toward the A. uncinata (P2) biozone. The Danian planktic and benthic foraminiferal assemblages indicate a deeper, probably bathyal environment. 2004 https://doi.org/10.1111/j.1945-5100.2004.tb01131.x Meteoritics & Planetary Science 39 1099-1111 7 https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1945-5100.2004.tb01131.x José A. ARZ Laia ALEGRET Ignacio ARENILLAS article Schmitt2004979 The chemical composition of suevites, displaced Cretaceous target rocks, and impact-generated dikes within these rocks from the Yaxcopoil-1 (Yax-1) drill core, Chicxulub impact crater, Mexico, is reported and compared with the data from the Yucatán 6 (Y6) samples. Within the six suevite subunits of Yax-1, four units with different chemical compositions can be distinguished: a) upper/lower sorted and upper suevite (depth of 795-846 m); b) middle suevite (depth of 846-861 m); c) brecciated impact melt rock (depth of 861-88-5 m); and d) lower suevite (depth of 885-895 m). The suevite sequence (a), (b), and (d) display an increase of the CaO content and a decrease of the silicate basement component from top to bottom. In contrast, the suevite of Y6 shows an inverse trend. The different distances of the Yax-1 and Y6 drilling sites from the crater center (∼60, and ∼47 km, respectively) lead to different suevite sequences. Within the Cretaceous rocks of Yax-1, a suevitic dike (depth of ∼916 m) does not display chemical differences when compared with the suevite, while an impact melt rock dike (depth of ∼1348 m) is significantly enriched in immobile elements. A elastic breccia dike (depth of ∼1316 m) is dominated by material derived locally from the host rock, while the silicate-rich component is similar to that found in the suevite. Significant enrichments of the K2O content were observed in the Yax- 1 suevite and the impact-generated dikes. All impactites of Yax-1 and Y6 are mixtures of a crystalline basement and a carbonate component from the sedimentary cover. An anhydrite component in the impactites is missing (Yax-1) or negligible (Y6). 2004 10.1111/j.1945-5100.2004.tb00940.x Meteoritics and Planetary Science 39 979-1001 Institute of Mineralogy, Museum of Natural History, Humboldt-University of Berlin, Invalidenstrasse 43, Berlin D-10115, Germany 6 https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943111548&doi=10.1111%2fj.1945-5100.2004.tb00940.x&partnerID=40&md5=47357405e9b86e5f254d960ab68c30d2 cited By 37 R.T. Schmitt A. Wittmann D. Stöffler article Wilhelm2004813 Within the frame of the International Continental Deep Drilling Program (ICDP) and as a part of the Chicxulub Scientific Drilling Project (CSDP), high resolution temperature measurements were performed in the borehole Yaxcopoil-1 (Yax-1). The temperature was logged to the depth of 858 m seven times between March 6-19, 2002, starting 10 days after the hole was shut in and mud circulation ceased. Successive logs revealed only small temperature variations in time and space, indicating a fast temperature recovery to almost undisturbed conditions prior to the first log. From these logs, a mean temperature gradient of ∼37 mK/m was determined below the uppermost 250 m. Another temperature log was recorded on May 24, 2003 (15 months after the shut in) to a depth of 895 m. The obtained temperature profile is very similar to the 2002 profile, with an insignificantly higher mean gradient below 250 m that may indicate a long-term return to the pre-drilling temperature. The temperature in the uppermost part of the hole bears signs of considerable influence of a convective contribution to the vertical thermal heat transfer. The depth extent of the convection seems to have deepened from 150 m in March 2002 to 230 m in May 2003. Based on the observed temperature gradient and the rock types encountered in the borehole above 670 m, the conducted heat flow is expected to be in the range 65-80 mW/m2. © Meteoritical Society, 2004. 2004 10.1111/j.1945-5100.2004.tb00931.x Meteoritics and Planetary Science 39 813-819 Geophysical Institute, University of Karlsruhe, Herzstrasse 16, Karlsruhe D-76187, Germany; Geophysical Institute, Czech Academy of Sciences, Prageu, Czech Republic; Institute of Applied Geosciences, Technical University of Berlin, Berlin, Germany; Moscow State Geol. Prospecting Univ., Moscow, Russian Federation 6 https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943062854&doi=10.1111%2fj.1945-5100.2004.tb00931.x&partnerID=40&md5=45688331b1289b14ce7927ec434e905e cited By 20 H. Wilhelm P. Heidinger J. Šafanda V. Čermák H. Burkhardt Yu. Popov article Zürcher20041199 Petrographic, electron microprobe, and Raman spectrometric analyses of Yaxcopoil-1 core samples from the Chicxulub crater indicate that the impact generated a hydrothermal system. Relative textural and vein crosscutting relations and systematic distribution of alteration products reveal a progression of the hydrothermal event in space and time and provide constraints on the nature of the fluids. The earliest calcite, halite, and gaylussite suggest that the impactite sequence was initially permeated by a low temperature saline brine. Subsequent development of a higher temperature hydrothermal regime is indicated by thermal metamorphic diopside-hedenbergite (Aeg3Fs18-33En32-11Wo47-53) after primary augite and widespread Na-K for Ca metasomatic alkali exchange in plagioclase. Hydrothermal sphene, apatite, magnetite ± (bornite), as well as early calcite (combined 3 to 8 vol%) were introduced with metasomatic feldspar. A lower temperature regime characterized by smectite after probable primary glass, secondary chlorite, and other pre-existing mafic minerals, as well as very abundant calcite veins and open-space fillings, extensively overprinted the early hydrothermal stage. The composition of early and late hydrothermal minerals show that the solution was chlorine-rich (Cl/F&gt;10) and that its Fe/Mg ratio and oxidation state increased substantially (4 to 5 logfO2 units) as temperature decreased through time. The most altered zone in the impactite sequence occurs 30 m above the impact melt. The lack of mineralogical zoning about the impact melt and convective modeling constraints suggest that this unit was too thin at Yaxcopoil-1 to provide the necessary heat to drive fluids and implies that the hydrothermal system resulted from the combined effects of a pre-existing saline brine and heat that traveled to the Yaxcopoil-1 site from adjacent areas where the melt sheet was thicker. Limonite after iron oxides is more common toward the top of the sequence and suggests that the impactite section was subjected to weathering before deposition of the Tertiarý marine cover. In addition, scarce latest anatase stringers, chalcopyrite, and barite in vugs, francolite after apatite, and recrystallized halite are the likely products of limited post-hydrothermal ambient-temperature diagenesis, or ocean and/or meteoric water circulation. © Meteoritical Society, 2004. Printed in USA. 2004 10.1111/j.1945-5100.2004.tb01137.x Meteoritics and Planetary Science 39 1199-1221 Lunar and Planetary Laboratory, University of Arizona, 1629 East University Boulevard, Tucson, AZ 85721, United States 7 https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943110342&doi=10.1111%2fj.1945-5100.2004.tb01137.x&partnerID=40&md5=4509b0924dfbe3b773e4f09a9ba1f31c cited By 72 L. Zurcher D.A. Kring article Kring2004879 The Chicxulub Scientific Drilling Project (CSDP), Mexico, produced a continuous core of material from depths of 404 to 1511 m in the Yaxcopoil-1 (Yax-1) borehole, revealing (top to bottom) Tertiary marine sediments, polymict breccias, an impact melt unit, and one or more blocks of Cretaceous target sediments that are crosscut with impact-generated dikes, in a region that lies betweeon the peak ring and final crater rim. The impact melt and breccias in the Yax-1 borehole are 100 m thick, which is approximately 1/5 the thickness of breccias and melts exposed in the Yucatán-6 exploration hole, which is also thought to be located between the peak ring and final rim of the Chicxulub crater. The sequence and composition of impact melts and breccias are grossly similar to those in the Yucatán-6 hole. Compared to breccias in other impact craters, the Chicxulub breccias are incredibly rich in silicate melt fragments (up to 84% versus 30 to 50%, for example, in the Rieś). The melt in the Yax-1 hole was produced largely from the silicate basement lithologies that lie beneath a 3 km- thick carbonate platform in the target area. Small amounts of immiscible molten carbonate were ejected with the silicate melt, and clastic carbonate often forms the matrix of the polymict breccias. The melt unit appears to have been deposited while molten but brecciated after solidification. The melt fragments in the polymict breccias appear to have solidified in flight, before deposition, and fractured during transport and deposition. © Meteoritical Society, 2004. 2004 10.1111/j.1945-5100.2004.tb00936.x Meteoritics and Planetary Science 39 879-897 Lunar and Planetary Laboratory, University of Arizona, 1629 East University Boulevard, Tucson, AZ 85721, United States; Planetary Sciences Branch, SN2, NASA Johnson Space Center, Houston, TX 77058, United States; Instituto de Geofisica, Univ. Nacl. Autonoma de Mexico, Mexico City 04510, Mexico 6 https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943080586&doi=10.1111%2fj.1945-5100.2004.tb00936.x&partnerID=40&md5=e72bfdaaa7e9274ed5390ecc227166b9 cited By 62 D.A. Kring F. Horz L. Zurcher J. Urrutia Fucugauchi article Dressler2004857 The impact breccias encountered in drill hole Yaxcopoil-1 (Yax-1) in the Chicxulub impact structure have been subdivided into six units. The two uppermost units are redeposited suevite and suevite, and together are only 28 m thick. The two units below are interpreted as a ground surge deposit similar to a pyroclastic flow in a volcanic regime with a fine-grained top (unit 3; 23 m thick; nuée ardente) and a coarse breccia (unit 4;∼15 m thick) below. As such, they consist of a mélange of clastic matrix breccia and melt breccia. The pyroclastic ground surge deposit and the two units 5 and 6 below are related to the ejecta curtain. Unit 5 (∼24 m thick) is a silicate impact melt breccia, whereas unit 6 (10 m thick) is largely a carbonate melt breccia with some clastic-matrix components. Unit 5 and 6 reflect an overturning of the target stratigraphy. The suevites of units 1 and 2 were deposited after emplacement of the ejecta curtain debris. Reaction of the super-heated breccias with seawater led to explosive activity similar to phreomagmatic steam explosion in volcanic regimes. This activity caused further brecciation of melt and melt fragments. The fallback suevite deposit of units 1 and 2 is much thinner than suevite deposits at larger distances from the center of the impact structure than the 60 km of the Yax-1 drill site. This is evidence that the fallback suevite deposit (units 1 and 2) originally was much thicker. Unit 1 exhibits sedimentological features suggestive of suevite redeposition. Erosion possibly has occurred right after the K/T impact due to seawater backsurge, but erosion processes spanning thousands of years may also have been active. Therefore, the top of the 100 m thick impactite sequence at Yaxcopoil, in our opinion, is not the K/T boundary. © Meteoritical Society, 2004. 2004 10.1111/j.1945-5100.2004.tb00935.x Meteoritics and Planetary Science 39 857-878 Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, TX 77058, United States; Geophysical Institute, University of Alaska, Fairbanks, AK 99709, United States; Lockheed Martin, 2400 Nasa Road 1, Houston, TX 77058, United States; Geological Survey of Canada, Ottawa, K1A 0E8, Canada 6 https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943082685&doi=10.1111%2fj.1945-5100.2004.tb00935.x&partnerID=40&md5=bcf1d54731e8f67af3b4c4a2bf195e87 cited By 51 B.O. Dressler V.L. Sharpton C.S. Schwandt D. Ames article Wohlgemuth2004791 Impact structures in the solar system are mainly recognized and explored through remote sensing and, on Earth, through geophysical deep sounding. To date, a continuous scientific sampling of large impact craters from cover rocks to target material has only seldom been performed. The first project to deep-drill and core into one of the largest and well-preserved terrestrial impact structures was executed in the winter of 2001/2002 in the 65 Myr-old Chicxulub crater in Mexico using integrated coring sampling and in situ measurements. The combined use of different techniques allows a three-dimensional insight and a better understanding of impact processes. Here, we report the integration of conventional rotary drilling techniques with wireline mining coring technology that was applied to drill the 1510 m-deep Yaxcopoil-1 (Yax-1) well about 40 km southwest of Mérida, Yucatán, Mexico. During the course of the project, we recovered approximately 900 m of intact core samples including the transitions of reworked ejecta to post-impact sediments, and that one from large blocks of tilted target material to impact-generated rocks, i.e., impact melt breccias and suevites. Coring was complemented by wireline geophysical measurements to obtain a continuous set of in situ petrophysical data of the borehole walls. The data acquired is comprised of contents of a natural radioactive element, velocities of compressional sonic waves, and electrical resistivity values. All the digital data sets, including technical drilling parameters, initial scientific sample descriptions, and 360° core pictures, were distributed during the course of the operations via Internet and were stored in the ICDP Drilling Information System (http://www.icdp-online.org), serving the global community of cooperating scientists as a basic information service. © Meteoritical Society, 2004. 2004 10.1111/j.1945-5100.2004.tb00929.x Meteoritics and Planetary Science 39 791-797 Operational Support Group ICDP, GeoForschungsZentrum Potsdam, Telegrafenberg A34, Potsdam D-14473, Germany 6 https://www.scopus.com/inward/record.uri?eid=2-s2.0-4043149925&doi=10.1111%2fj.1945-5100.2004.tb00929.x&partnerID=40&md5=a45511189cd3cf2f79a5a6da2e4f862e cited By 14 L. Wohlgemuth E. Bintakies R. Conze U. Harms article Dressler2003 2003 10.1029/2003EO140001 Eos 84 125+130 Lunar and Planetary Institute, Houston, United States 14 https://www.scopus.com/inward/record.uri?eid=2-s2.0-53549085726&doi=10.1029%2f2003EO140001&partnerID=40&md5=6088a69949b7cdf9b0581d443f2ef8d8 cited By 64 B.O. Dressler V.L. Sharpton J. Morgan R. Buffler D. Moran J. Smit D. Stäffler J. Urrutia article Claeys20031299 The suevite breccia of the Chicxulub impact crater, Yucatàn, Mexico, is more variable and complex in terms of composition and stratigraphy than suevites observed at other craters. Detailed studies (microscope, electron microprobe, SEM, XRF) have been carried out on a noncontinuous set of samples from the drill hole Yucatàn 6 (Y6) located 50 km SW from the center of the impact structure. Three subunits can be distinguished in the suevite: the upper unit is a fine-grained carbonate-rich suevite breccia with few shocked basement clasts, mostly altered melt fragments, and formerly melted carbonate material; the middle suevite is a coarse-grained suevite with shocked basement clasts and altered silicate melt fragments; the lower suevite unit is composed of shocked basement and melt fragments and large evaporite clasts. The matrix of the suevite is not clastic but recrystallized and composed mainly of feldspar and pyroxene. The composition of the upper members of the suevite is dominated by the sedimentary cover of the Yucatàn target rock. With depth in well Y6, the amount of carbonate decreases and the proportion of evaporite and silicate basement rocks increases significantly. Even at the thin section scale, melt phases of different chemistry can be identified, showing that no widespread homogenization of the melt took place. The melt compositions also reflect the heterogeneity of the deep Yucatàn basement. Calcite with characteristic feathery texture indicates the existence of formerly pure carbonate melt. The proportion of carbonate to evaporite clasts is less than 5:1, except in the lower suevite where large evaporite clasts are present. This proportion constrains the amount of CO2 and SOx released by the impact event. 2003 10.1111/j.1945-5100.2003.tb00315.x Meteoritics and Planetary Science 38 1299-1317 Department of Geology, Vrije Universiteit Brussel, Pleinlaan 2, Brussels B-1050, Belgium; ZERIN (Ctr. for Ries Crater/Impact), Vordere Gerbergasse 3, Nördlingen 86720, Germany; Institute of Geology (UNAM), Ciudad Universitaria, Apartado Postal 70-296, México, DF 04510, Mexico; Institut für Mineralogie, Museum für Naturkunde, Humboldt-Universität zu Berlin, Invalidenstrasse 43, Berlin 10099, Germany 9 https://www.scopus.com/inward/record.uri?eid=2-s2.0-0742323356&doi=10.1111%2fj.1945-5100.2003.tb00315.x&partnerID=40&md5=090badb0b9701f0eb3478875fb8fc721 cited By 59 P. Claeys S. Heuschkel E. Lounejeva-Baturina G. Sanchez-Rubio D. Stöffler article Rebolledo-Vleyra2000928 A scientific drilling program is being carried out by the National Autonomous University of Mexico (UNAM) at the southern sector of the Chicxulub impact crater in the Yucatan Peninsula, Mexico. Eight boreholes, ranging in depth from 60 m to 702 m, with a total of 2.62 km of continuos core, were recovered. A high recovery rate of up to 99% (overall average recovery rate for the eight boreholes is 87%) allows us to investigate in detail the stratigraphy of the impact lithologies and the Tertiary carbonate sequence. Three of the boreholes (UNAM-5, UNAM-6, and UNAM-7, with core recovery rates from 89 to 99%) sampled impact breccias that were classified in two units-an upper breccia sequence rich in basement clasts, impact glass, and fragments of melt (suevite-like breccia) and a lower breccia sequence rich in limestone, dolomite, and evaporite clasts (bunte-like breccia). Depths of contact between the Tertiary carbonate sequence and the impact breccias are 332.0 m in UNAM-5, 222.2 m in UNAM-7, and 282.8 m in UNAM-6, giving the depth to the K/T boundary. In UNAM-7, the contact between the upper and the lower breccias is at 348.4 m, which yields a thickness of 126.2 m for the suevite-like breccia. The rest of the boreholes sampled part of the Tertiary carbonate sequence (∼200 m thick), composed mainly of limestones, dolomitized carbonates, and calcarenite, with some fossiliferous horizons. 2000 10.1080/00206810009465118 International Geology Review 42 928-940 Laboratorio de Paleomagnetismo y Geofisica Nuclear, Instituto de Geofisica, Universidad National Autonoma de Mexico, Coyoacán, D.F., 04510, Mexico; Institute of Geophysics, University of Alaska, Fairbanks AK 903 Koyukuk Dr, United States 10 https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034477630&doi=10.1080%2f00206810009465118&partnerID=40&md5=73ea08396e74dd35779d7d9f99424809 cited By 50 M. Rebolledo-Vleyra J. Urrutia-Fucugauchi L.E. Marín A. Trejo-García V.L. Sharpton A.M. Soler-Arechalde