Microbial Signatures in Deep CO2-Saturated Miocene Sediments of the Active Hartoušov Mofette System (NW Czech Republic) - Liu, Qi; Adler, Karsten; Lipus, Daniel; K{ampf, Horst; Bussert, Robert; Plessen, Birgit; Schulz, Hans-Martin; Krauze, Patryk; Horn, Fabian; Wagner, Dirk; Mangelsdorf, Kai; Alawi, Mashal (Frontiers in Microbiology, 2020)
The Hartoušov mofette system is a natural CO2 degassing site in the central Cheb Basin (Eger Rift, Central Europe). In early 2016 a 108 m deep core was obtained from this system to investigate the impact of ascending mantle-derived CO2 on indigenous deep microbial communities and their surrounding life habitat. During drilling, a CO2 blow out occurred at a depth of 78.5 meter below surface (mbs) suggesting a CO2 reservoir associated with a deep low-permeable CO2-saturated saline aquifer at the transition from Early Miocene terrestrial to lacustrine sediments. Past microbial communities were investigated by hopanoids and glycerol dialkyl glycerol tetraethers (GDGTs) reflecting the environmental conditions during the time of deposition rather than showing a signal of the current deep biosphere. The composition and distribution of the deep microbial community potentially stimulated by the upward migration of CO2 starting during Mid Pleistocene time was investigated by intact polar lipids (IPLs), quantitative polymerase chain reaction (qPCR), and deoxyribonucleic acid (DNA) analysis. The deep biosphere is characterized by microorganisms that are linked to the distribution and migration of the ascending CO2-saturated groundwater and the availability of organic matter instead of being linked to single lithological units of the investigated rock profile. Our findings revealed high relative abundances of common soil and water bacteria, in particular the facultative, anaerobic and potential iron-oxidizing Acidovorax and other members of the family Comamonadaceae across the whole recovered core. The results also highlighted the frequent detection of the putative sulfate-oxidizing and CO2-fixating genus Sulfuricurvum at certain depths. A set of new IPLs are suggested to be indicative for microorganisms associated to CO2 accumulation in the mofette system. © Copyright © 2020 Liu, Adler, Lipus, K{ampf, Bussert, Plessen, Schulz, Krauze, Horn, Wagner, Mangelsdorf and Alawi.
Keywords: biological marker; carbon; carbon dioxide; carbon nitrogen sulfur monocycle; clario star; fluorescein sodium; ground water; organic carbon; organic nitrogen; RNA 16S; soil organic matter; urea; Acidobacteria; Actinobacteria; Alphaproteobacteria; Arabidopsis thaliana; Article; bacterial microbiome; Bacteroidetes; Betaproteobacteria; biogeography; bioinformatics; biosphere; calibration; carbon dioxide fixing bacterium; Chloroflexi; column chromatography; Comamonadaceae; community structure; Crenarchaeota; cyanobacterium; DNA extraction; DNA purification; electrospray mass spectrometry; Escherichia coli; freeze drying; Gallionella; Gammaproteobacteria; gene sequence; geochemical analysis; high performance liquid chromatography; homogenate; isotope analysis; lipid analysis; liquid chromatography; methanogenesis; Methanosaeta; Methanosarcina; microbial biomass; microbial community; microbial contamination; microbial diversity; migration; Miocene; multidimensional scaling; nonhuman; organisms by metabolism; population abundance; real time polymerase chain reaction; saponification; soil microflora; stratigraphy; sulfate oxidizing bacterium; Sulfuricurvum; thermal spring; total nitrogen content; total organic carbon; ultra performance liquid chromatography

Millennial-scale vegetation history of the north-eastern Russian Arctic during the mid-Pliocene inferred from the Lake El'gygytgyn pollen record - Andreev, A.A.; Tarasov, P.E.; Wennrich, V.; Melles, M. (Global and Planetary Change, 2020)
The 318-m long sediment record from Lake El'gygytgyn, NE Russia situated in the present-day herb tundra zone, provides a unique archive of high Arctic environmental changes since ca 3.6 million years ago (Ma). This paper focuses on pollen-derived vegetation change during the mid-Pliocene Warm Period (mPWP) and in particular during Marine Isotope Stage (MIS) M2, which is known to represent the coldest interval of the Pliocene. Building on initial pollen studies, we provide a more complete record and a more detailed discussion of climatically-driven vegetation and environmental changes in the northeastern Russian Arctic, spanning the 203-thousand-year interval between 3.383 and 3.180 Ma ago. Pine-spruce-fir-larch-Douglas fir forests dominated the area around Lake El'gygytgyn between 3.383 and 3.330 Ma (MIS MG4 - MIS MG2). Colder and drier climate caused a decrease of coniferous forests and widespread Sphagnum habitats around the lake between 3.370 and 3.357 Ma. After 3.3 Ma, the presence of spruce, fir and Douglas fir decreased again. A very pronounced cooling took place at the first half of MIS M2 (3.312 –3.283 Ma), when treeless tundra- and steppe-like habitats became common in the regional vegetation. Climate conditions were similar or only slightly warmer and wetter to those of the Holocene. Numerous coprophilous fungi spores identified in the MIS M2 pollen samples suggest the presence of grazing mammals around the lake. Larch-pine forests with some spruce started to dominate the area again after ca. 3.282 Ma, thus pointing to a significant climate amelioration during the mPWP. However, the forested area decreased, while herb- and shrub-dominated vegetation spread again during MIS KM6 (especially 3.235 –3.223 Ma), suggesting a noticeable climatic deterioration and relatively cold and dry conditions. © 2020 Elsevier B.V.
cited By 4
Keywords: Deterioration; Ecosystems; Forestry; Lakes; Mammals; Coniferous forests; Environmental change; Marine isotope stages; Mid-Pliocene; Pollen; Russian Arctic; Vegetation change; Vegetation history; Vegetation; environmental change; fungus; grazing; Pliocene; pollen; vegetation history; Chukchi; Elgygytgyn Lake; Russian Federation; Abies; Fungi; Larix; Mammalia; Picea; Pseudotsuga; Pseudotsuga menziesii; Sphagnum

Monitoring crustal CO2 flow: Methods and their applications to the mofettes in West Bohemia - Fischer, Tom'aš; Vlček, Josef; Lanzend{orfer, Martin (Solid Earth, 2020)
Monitoring of CO2 degassing in seismoactive areas allows the study of correlations of gas release and seismic activity. Reliable continuous monitoring of the gas flow rate in rough field conditions requires robust methods capable of measuring gas flow at different types of gas outlets such as wet mofettes, mineral springs, and boreholes. In this paper we focus on the methods and results of the long-term monitoring of CO2 degassing in the West Bohemia/Vogtland region in central Europe, which is typified by the occurrence of earthquake swarms and discharge of carbon dioxide of magmatic origin. Besides direct flow measurement using flowmeters, we introduce a novel indirect technique based on quantifying the gas bubble contents in a water column, which is capable of functioning in severe environmental conditions. The method calculates the mean bubble fraction in a water-gas mixture from the pressure difference along a fixed depth interval in a water column. Laboratory tests indicate the nonlinear dependence of the bubble fraction on the flow rate, which is confirmed by empirical models found in the chemical and nuclear engineering literature. Application of the method in a pilot borehole shows a high correlation between the bubble fraction and measured gas flow rate. This was specifically the case for two coseismic anomalies in 2008 and 2014, when the flow rate rose during a seismic swarm to a multitude of the preseismic level for several months and was followed by a long-term flow rate decline. However, three more seismic swarms occurring in the same fault zone were not associated with any significant CO2 flow anomaly.We surmise that this could be related to the slightly farther distance of the hypocenters of these swarms compared to the two ones which caused the coseismic CO2 flow rise. Further long-term CO2- flow monitoring is required to verify the mutual influence of CO2 degassing and seismic activity in the area. © 2020 Cambridge University Press. All rights reserved.
Keywords: Bohemia; Czech Republic; Boreholes; Carbon dioxide; Degassing; Earthquakes; Flow measurement; Flow of gases; Gases; Mineral springs; Bubble fractions; Continuous monitoring; Earthquake swarms; Environmental conditions; Field conditions; Long term monitoring; Nonlinear dependence; Pressure differences; carbon dioxide; coseismic process; crustal structure; degassing; discharge; earthquake hypocenter; earthquake swarm; flow velocity; gas flow; monitoring; Flow rate

Multi-Level Gas Monitoring: A New Approach in Earthquake Research - Woith, Heiko; Daskalopoulou, Kyriaki; Zimmer, Martin; Fischer, Tom'aš; Vlček, Josef; Trubač, Jakub; Rosberg, Jan-Erik; Vylita, Tom'aš; Dahm, Torsten (Frontiers in Earth Science, 2020)
Fluid anomalies were often considered as possible precursors before earthquakes. However, fluid properties at the surface can change for a variety of reasons, including environmental changes near the surface, the response of the superficial fluid system to loads associated with the mechanical nucleation of earthquake fractures, or as a result of transients in fluid flow from the depths. A key problem is to understand the origin of the anomaly and to distinguish between different causes. We present a new approach to monitor geochemical and geophysical fluid properties along a vertical profile in a set of drillings from a depth of a few hundred meters to the surface. This setup can provide hints on the origin of temporal variations, as the migration direction and speed of properties can be measured. In addition, potential admixtures of fluids from a deep crustal or mantle origin with meteoric fluids can be better quantified. A prototype of a multi-level gas monitoring system comprising flow and pressure probes, as well as monitoring of fluid-geochemical properties and stable isotopes is being implemented in a mofette field with massive CO2 (up to 97 tons per day) degassing. The mofette is believed a gas emission site where CO2 ascends through crustal-scale conduits from as deep as the upper mantle, and may therefore provide a natural window to ongoing magmatic processes at mantle depth. Fluids from three adjacent boreholes–30, 70, and 230 m deep–will be continuously monitored at high sampling rates. © Copyright © 2020 Woith, Daskalopoulou, Zimmer, Fischer, Vlček, Trubač, Rosberg, Vylita and Dahm.
Keywords: Carbon dioxide; Earthquakes; Gas detectors; Geochemistry; Earthquake research; Environmental change; Gas monitoring systems; Geochemical properties; High sampling rates; Magmatic process; Temporal variation; Vertical profile; carbon dioxide; crustal structure; degassing; drilling; earthquake mechanism; earthquake swarm; fluid flow; fluid pressure; geochemistry; geophysics; hydrocarbon reservoir; monitoring; radon; Flow of fluids

Multifractal characterization of the Coniacian –Santonian OAE3 in lacustrine and marine deposits based on spectral gamma ray logs - Kouamelan, K.S.; Zou, C.; Wang, C.; Assie, K.R.; Peng, C.; Mondah, O.R.; N’dri, K.A.; Brantson, E.T. (Scientific Reports, 2020)
Limited to the Atlantic and its surrounding basins, the expression of the Coniacian –Santonian oceanic anoxic event (OAE3) was discovered in the non-marine Cretaceous Songliao Basin, Eastern Asia not long ago. In this study, based on spectral gamma ray logs data recorded in three basins, the self-similarity of the OAE3 was studied through the analysis of the scaling properties of thorium –potassium and thorium –uranium distributions both in marine and terrestrial environments using the multifractal detrending fluctuation analysis. The results indicate that, in both marine and terrestrial systems, the OAE3 intervals are characterized by their multifractal nature due to long-range correlation. However, the multifractal features of the studied OAE3 intervals are different in the three basins, although some common trends were observed. By comparing the degree of multifractality of the OAE3 deposits with the clay minerals and the redox conditions, it appears that the changes of the multifractal features are controlled by local changes such as clay mineralogy and redox conditions in both milieus under different sedimentation patterns. At all sites, the left side shortened spectrum of the thorium –potassium distribution suggests the presence of local fluctuations with minor amplitudes during the OAE3. Furthermore, the shortened singularity spectrum of the thorium –uranium distribution reflects the existence of small-scale fluctuations with large amplitudes at marine sites while in the non-marine Songliao Basin, the thorium –uranium distribution suggests the presence of local fluctuations with small amplitudes during the OAE3. Therefore, a more local behavior of the event is considered although the regional character is not neglected. © 2020, The Author(s).
cited By 2

New SIMS U-Pb geochronology for the Shahezi Formation from CCSD-SK-IIe borehole in the Songliao Basin, NE China - Yu, Z.; He, H.; Deng, C.; Lu, K.; Shen, Z.; Li, Q. (Science Bulletin, 2020)
cited By 11

Permeability profiles across the crust-mantle sections in the Oman Drilling Project inferred from dry and wet resistivity data - Katayama, Ikuo; Abe, Natsue; Hatakeyama, Kohei; Akamatsu, Yuya; Okazaki, Keishi; Ulven, Ole Ivar; Hong, Gilbert; Zhu, Wenlu; Cordonnier, Benoit; Michibayashi, Katsuyoshi; et al. (Journal of Geophysical Research: Solid Earth, 2020)
Permeability profiles in the crust-mantle sequences of the Samail ophiolite were constructed based on onboard measurements of the electrical resistivity of cores recovered during the Oman Drilling Project. For each sample, we measured dry and brine-saturated resistivity during the description campaign on the drilling vessel Chikyu. Owing to the conductive brine in the pore space, wet resistivity is systematically lower than dry resistivity. The difference between dry and wet resistivity is attributed to the movement of dissolved ions in brine that occupies the pore space. We applied effective medium theory to calculate the volume fraction of pores that contribute to electrical transport. Using an empirical cubic law between transport porosity and permeability, we constructed permeability profiles for the crust-mantle transition zone and the serpentinized mantle sections in the Samail ophiolite. The results indicate that (1) the gabbro sequence has a markedly lower permeability than the underlying mantle sequence; (2) serpentinized dunites have higher permeability than serpentinized harzburgites; and (3) discrete sample permeability is correlated with ultrasonic velocity, suggesting that the permeability variations predominately reflect crack density and geometry. ©2020. American Geophysical Union. All Rights Reserved.
cited By 9
Keywords: crust-mantle boundary; dunite; electrical resistivity; gabbro; harzburgite; ophiolite; permeability; porosity; transition zone

Non-marine carbon-isotope stratigraphy of the Triassic-Jurassic transition in the Polish Basin and its relationships to organic carbon preservation, pCO2 and palaeotemperature - Pie'nkowski, Grzegorz; Hesselbo, Stephen P.; Barbacka, Maria; Leng, Melanie J. (Earth-Science Reviews, 2020)

Non-reactive and reactive experiments to determine the electrical conductivities of aqueous geothermal solutions up to supercritical conditions - Kummerow, Juliane; Raab, Siegfried; Schuessler, Jan A.; Meyer, Romain (Journal of Volcanology and Geothermal Research, 2020)

Observations on the Structure of Surtsey - Moore, James G; Jackson, Marie D (Surtsey Res, 2020)

Organic matter from the Chicxulub crater exacerbated the K-Pg impact winter - Lyons, S.L.; Karp, A.T.; Bralower, T.J.; Grice, K.; Schaefer, B.; Gulick, S.P.S.; Morgan, J.V.; Freeman, K.H. (Proceedings of the National Academy of Sciences of the United States of America, 2020)
An asteroid impact in the Yucat'an 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.
cited By 24

Origin of a global carbonate layer deposited in the aftermath of the Cretaceous-Paleogene boundary impact - Bralower, T.J.; Cosmidis, J.; Heaney, P.J.; Kump, L.R.; Morgan, J.V.; Harper, D.T.; Lyons, S.L.; Freeman, K.H.; Grice, K.; Wendler, J.E.; Zachos, J.C.; Artemieva, N.; et al. (Earth and Planetary Science Letters, 2020)
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.
cited By 20

Paleomagnetic Constraint of the Brunhes Age Sedimentary Record From Lake Jun'in, Peru - Hatfield, R.G.; Stoner, J.S.; Solada, K.E.; Morey, A.E.; Woods, A.; Chen, C.Y.; McGee, D.; Abbott, M.B.; Rodbell, D.T. (Frontiers in Earth Science, 2020)
Normalized remanence, a proxy for relative geomagnetic paleointensity, along with radiocarbon and U-Th age constraints, facilitates the generation of a well-constrained chronology for sediments recovered during International Continental Scientific Drilling Program (ICDP) coring of Lake Jun'in, Peru. The paleomagnetic record of the ∼88 m stratigraphic section from Lake Jun'in was studied, and rock magnetic variability constrained, through analysis of 109 u-channel samples and 56 discrete samples. Downcore variations in sediment lithology reflect climate and hydrological processes over glacial-interglacial time frames and these changes are strongly reflected in the bulk magnetic properties. Glacial sediments are characterized by higher detrital silt content, higher magnetic susceptibility and magnetic remanence values, and a magnetic coercivity that is characteristic of ferrimagnetic (titano)magnetite and/or maghemite. Interglacial sediments and low lake-level facies are dominated by carbonate lithologies and/or peat horizons that result in lower magnetic concentration values. Sediments with moderately high Natural Remanent Magnetization (NRM) intensity ( >1 × 10 –3 A/m) have well resolved component directions and inclination values that vary around geocentric axial dipole expectations. This remanence value can be used as a threshold to filter the lowest quality paleomagnetic data from the record. Normalized NRM intensity values are also sensitive to lithologic variability, but following NRM remanence filtering, only the highest quality ferrimagnetic dominated data are retained which then show no coherence with bulk magnetic properties. Constrained by the existing radiocarbon based chronology over the last 50 kyrs and 18 U-Th age constraints that are restricted to five interglacial sediment packages, filtered normalized remanence parameters compare well with global relative paleointensity stacks, suggesting relative variations in geomagnetic intensity are preserved. By adjusting the existing age-depth model we improve the correlation between the Jun'in normalized intensity record and a well-dated RPI stack and RPI model. We then incorporate these paleomagnetic tie points with the existing radiometric dates using a modeling approach to assess uncertainty and refine the age-depth model for Lake Jun'in. In combining relative and radiometric dating, the new age-depth model captures glacial-interglacial variations in sedimentation rate and improves the orbital-scale age model for the sediments accumulated in Lake Jun'in basin over most of the Brunhes. © Copyright © 2020 Hatfield, Stoner, Solada, Morey, Woods, Chen, McGee, Abbott and Rodbell.
cited By 7
Keywords: Binary alloys; Ferrimagnetism; Geomagnetism; Glacial geology; Lakes; Lithology; Magnetic susceptibility; Magnetite; Natural resources management; Radiometry; Remanence; Stratigraphy; Thorium alloys; Uncertainty analysis; Uranium alloys; Continental scientific drillings; Geomagnetic intensity; Hydrological process; Interglacial sediments; Magnetic coercivities; Magnetic concentration; Natural remanent magnetization; Relative paleointensity; Sediments; age determination; Brunhes chron; chronology; geomagnetism; lacustrine deposit; paleointensity; paleomagnetism; remanent magnetization; stratigraphy; Junin; Lake Junin; Peru

Passive Seismic Imaging of Near Vertical Structures Around the SAFOD Site, California, Jointly Using Scattered P and SH Waves - Chang, K.; Zhang, H. (Journal of Geophysical Research: Solid Earth, 2020)
To better illuminate structural discontinuities around the San Andreas Fault Observatory at Depth (SAFOD) site, following the previous study of Zhang et al. (2009), we have extended the Generalized Radon Transform (GRT) method to jointly use scattered P and SH waves from abundant local earthquakes recorded by a local dense seismic network. A hybrid imaging condition is applied to extract consistent structures from scattered P and SH images. In this way, more robust structure information can be determined from separate images with potential artifacts. For the transverse component waveforms, coherent S-S scattered waves after the direct SH waves can be clearly identified, and they are less interfered with by other scattered and converted waves compared to scattered P-P waves on the vertical component. Similar to Zhang, Wang, et al. (2009), near-vertical reflectors are imaged on both sides of the San Andreas Fault (SAF) with scattered SH waves, which is generally consistent with the imaging results using scattered P-P waves from local earthquakes and a wide-angle active seismic reflection profile. Compared to the P-P scattering imaging result, the imaging result using scattered SH waves has higher resolution due to shorter S wavelength and cleaner S-S scattered waveforms, and the SAF, as well as other reflectors around it, is better resolved. Although the resolution of the joint image obtained by combining separate imaging results from different scattered waves may be degraded, it is able to more robustly characterize strong structure discontinuities using passive seismic sources. © 2020. American Geophysical Union. All Rights Reserved.
cited By 0
Keywords: P-wave; Radon transform; San Andreas Fault; seismic source; seismic tomography; SH-wave; structural geology; wave scattering; California; Parkfield; United States

Report on ICDP Deep Dust workshops: Probing continental climate of the late Paleozoic icehouse-greenhouse transition and beyond - Soreghan, G.S.; Beccaletto, L.; Benison, K.C.; Bourquin, S.; Feulner, G.; Hamamura, N.; Hamilton, M.; Heavens, N.G.; Hinnov, L.; Huttenlocker, A.; Looy, C.; Pfeifer, L.S.; et al. (Scientific Drilling, 2020)
Chamberlin and Salisbury's assessment of the Permian a century ago captured the essence of the period: it is an interval of extremes yet one sufficiently recent to have affected a biosphere with near-modern complexity. The events of the Permian - the orogenic episodes, massive biospheric turnovers, both icehouse and greenhouse antitheses, and Mars-analog lithofacies - boggle the imagination and present us with great opportunities to explore Earth system behavior. The ICDP-funded workshops dubbed Deep Dust, held in Oklahoma (USA) in March 2019 (67 participants from nine countries) and Paris (France) in January 2020 (33 participants from eight countries), focused on clarifying the scientific drivers and key sites for coring continuous sections of Permian continental (loess, lacustrine, and associated) strata that preserve high-resolution records. Combined, the two workshops hosted a total of 91 participants representing 14 countries, with broad expertise. Discussions at Deep Dust 1.0 (USA) focused on the primary research questions of paleoclimate, paleoenvironments, and paleoecology of icehouse collapse and the run-up to the Great Dying and both the modern and Permian deep microbial biosphere. Auxiliary science topics included tectonics, induced seismicity, geothermal energy, and planetary science. Deep Dust 1.0 also addressed site selection as well as scientific approaches, logistical challenges, and broader impacts and included a mid-workshop field trip to view the Permian of Oklahoma. Deep Dust 2.0 focused specifically on honing the European target. The Anadarko Basin (Oklahoma) and Paris Basin (France) represent the most promising initial targets to capture complete or near-complete stratigraphic coverage through continental successions that serve as reference points for western and eastern equatorial Pangaea. © 2020 Copernicus GmbH. All rights reserved.
cited By 1
Keywords: Biospherics; Geothermal energy; Greenhouses; Induced Seismicity; Site selection; Stratigraphy; Warehouses; Broader impacts; Continental climate; High resolution; Late Paleozoic; Paleoenvironments; Planetary science; Reference points; Research questions; Dust

The formation of dunite channels within harzburgite in the Wadi Tayin Massif, Oman Ophiolite: insights from compositional variability of Cr-Spinel and olivine in Holes BA1B and BA3A, Oman Drilling Project - Cocomazzi, Giuseppe; Grieco, Giovanni; Tartarotti, Paola; Bussolesi, Micol; Zaccarini, Federica; Crispini, Laura; Science Team, Oman Drilling Project (Minerals, 2020)

Scientific drilling workshop on the Weihe Basin Drilling Project (WBDP): Cenozoic tectonic-monsoon interactions - An, Z.; Zhang, P.; Vogel, H.; Song, Y.; Dodson, J.; Wiersberg, T.; Feng, X.; Lu, H.; Ai, L.; Sun, Y. (Scientific Drilling, 2020)
The Weihe Basin, enclosed by the Chinese Loess Plateau to the north and the Qinling Mountains to the south, is an outstanding, world-class continental site for obtaining high-resolution multi-proxy records that reflect environmental changes spanning most of the Cenozoic. Previous geophysical and sedimentary studies indicate that the basin hosts 6000-8000 m thick fluvial-lacustrine sedimentary successions spanning the Eocene to Holocene. This sedimentary record provides an excellent and unique archive to decipher long-term tectonic-climate interactions related to the uplift of the Tibetan Plateau, the onset/evolution of the Asian monsoon, and the development of the biogeography of East Asia. Owing to its location at the interface of the opposing westerly and Asian monsoon circulation systems, the Weihe Basin also holds enormous promise for providing a record of changes in these circulation systems in response to very different boundary conditions since the Eocene. To develop an international scientific drilling programme in the Weihe Basin, the Institute of Earth Environment, Chinese Academy of Sciences, organized a dedicated workshop with 55 participants from eight countries. The workshop was held in Xi'an, China, from 15 to 18 October 2019. Workshop participants conceived the key scientific objectives of the envisaged Weihe Basin Drilling Project (WBDP) and discussed technical and logistical aspects as well as the scope of the scientific collaboration in preparation for a full drilling proposal for submission to the International Continental Scientific Drilling Program (ICDP). Workshop participants mutually agreed to design a two-phase scientific drilling programme that will in a first phase target the upper 3000 m and in a second phase the entire up to 7500 m thick sedimentary infill of the basin. For the purpose of the 7500 m deep borehole, the world's only drill rig for ultra-deep scientific drilling on land, Crust 1, which previously recovered the entire continental Cretaceous sediments in the Songliao Basin, will be deployed in the WBDP. © 2020 Copernicus GmbH. All rights reserved.
cited By 4
Keywords: Atmospheric thermodynamics; Sedimentology; Tectonics; Chinese Academy of Sciences; Chinese Loess Plateau; Continental scientific drillings; Different boundary condition; Environmental change; Scientific collaboration; Scientific objectives; Workshop participants; Infill drilling

Tracing shock-wave propagation in the Chicxulub crater: Implications for the formation of peak rings - Ebert, M.; Poelchau, M.H.; Kenkmann, T.; Schuster, B. (Geology, 2020)
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.
cited By 5

The mesoproterozoic stac fada member, nw scotland: An impact origin confirmed but refined - Osinski, G.R.; Ferrière, L.; Hill, P.J.A.; Prave, A.R.; Preston, L.J.; Singleton, A.; Pickersgill, A.E. (Journal of the Geological Society, 2020)
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.
cited By 1

The onset of oxidative weathering traced by uranium isotopes - Br{uske, A.; Martin, A.N.; Rammensee, P.; Eroglu, S.; Lazarov, M.; Albut, G.; Schuth, S.; Aulbach, S.; Schoenberg, R.; Beukes, N.; Hofmann, A.; N{agler, T.; et al. (Precambrian Research, 2020)

The Role of Meteorite Impacts in the Origin of Life - Osinski, G.R.; Cockell, C.S.; Pontefract, A.; Sapers, H.M. (Astrobiology, 2020)
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.
cited By 34

The Surtsey volcano geothermal system: An analogue for seawater-oceanic crust interaction with implications for the elemental budget of the oceanic crust - Kleine, B.I.; Stef'ansson, A.; Kjartansd'ottir, R.; Prause, S.; Weisenberger, T.B.; Reynolds, H.I.; Sveinbj{ornsd'ottir, 'A.E.; Jackson, M.D.; Gudmundsson, M.T. (Chemical Geology, 2020)
Surtsey is a young volcanic island in the offshore extension of Iceland's southeast rift zone that grew from the seafloor during explosive and effusive eruptions in 1963 –1967. In 1979, a cored borehole (SE-1) was drilled to 181 m depth and in 2017 three cored boreholes (SE-2a, SE-2b and SE-3) were drilled to successively greater depths. The basaltic deposits host a low-temperature (40 –141 °C) seawater-dominated geothermal system. Surtsey provides an ideal environment to study water-rock interaction processes in a young seawater geothermal system. Elemental concentrations (SiO2, B, Na, Ca, Mg, F, dissolved inorganic carbon, SO4, Cl) and isotope contents (δD, δ18O) in borehole fluids indicate that associated geothermal waters in submarine deposits originated from seawater modified by reactions with the surrounding basalt. These processes produce authigenic minerals in the basaltic lapilli tuff and a corresponding depletion of certain elements in the residual waters. Coupling of measured and modelled concentrations investigates the effect of temperature and associated abundance of authigenic minerals on chemical fluxes from and to the igneous oceanic crust during low-temperature alteration. The annual chemical fluxes calculated at 50 –150 °C range from −0.01 to +0.1 × 1012 mol yr−1 for SiO2, +0.2 to +129 × 1012 mol yr−1 for Ca, −129 to −0.8 × 1012 mol yr−1 for Mg and −21 to +0.4 × 1012 mol yr−1 for SO4 where negative values indicate chemical fluxes from the ocean into the oceanic crust and positive values indicate fluxes from the oceanic crust to the oceans. These flux calculations reveal that water-rock interaction at varying water-rock ratios and temperatures produces authigenic minerals that serve as important sinks of seawater-derived SiO2, Mg and SO4. In contrast, water-rock interaction accompanied by dissolution of basaltic glass and primary crystal fragments provides a significant source of Ca. Such low-temperature alteration could effectively influence the elemental budget of the oceanic igneous crust and ocean waters. The modeling provides insights into water chemistries and chemical fluxes in low-temperature MOR recharge zones. Surtsey also provides a valuable young analogue for assessing the chemical evolution of fluid discharge over the life cycles of seamounts in ridge flank systems. © 2020 Elsevier B.V.
cited By 9
Keywords: Basalt; Boreholes; Budget control; Deposits; Geothermal fields; Geothermal wells; Infill drilling; Life cycle; Minerals; Offshore oil well production; Seawater; Silica; Silicon; Volcanoes; Authigenic minerals; Dissolved inorganic carbon; Effect of temperature; Effusive eruptions; Elemental concentrations; Low temperature alteration; Water rock interaction process; Water rock interactions; Temperature; analog model; authigenic mineral; chemical alteration; concentration (composition); dissolution; geothermal system; oceanic crust; rift zone; seamount; seawater; volcanic eruption; water-rock interaction; Iceland; Surtsey

Thermal imprints of Cenozoic tectonic evolution in the Songliao Basin, NE China: Evidence from apatite fission-track (AFT) of CCSD-SK1 borehole - Wang, S.; Cheng, Y.; Zeng, L.; Miao, P.; Jin, R.; Zhang, T.; Li, C.; Zhang, X. (Journal of Asian Earth Sciences, 2020)
We conduct apatite fission-track analysis in the Songliao Basin to reveal the Cenozoic tectonic uplifts and determine how basin development was associated with the transformation from the Paleo-Pacific plate to the Pacific plate and the change of the Pacific plate velocity. Our results from the CCSD-SK1 boreholes in the northern Songliao Basin reveal three Cenozoic cooling (uplift) events:Paleocene (65 –50 Ma), Oligocene (33 –22 Ma), late Miocene –Pliocene (14 –6 Ma) with the apparent mean exhumation rates of 0.08 –0.09 mm/yr, 0.08 –0.09 mm/yr and 0.11 –0.24 mm/yr, respectively. The total removal of the sedimentary cover resulted from 3 cooling (uplift) events is about 1500 m, the removal by the extreme cooling (uplift) event (14 –6 Ma) is about 900 m. In this paper, we infer that the transformation of the Paleo-Pacific plate (Izanagi plate) to the Pacific plate plays the first-order control on the first cooling event (65 –50 Ma). The second (33 –22 Ma) and third (14 –6 Ma) cooling events are closely related to the steady and relatively high motion velocity of the Pacific plate. Since Oligocene, a large scale of tectonic uplifts widely happened not only in basins but also in the ranges around them in northeastern China. © 2020 Elsevier Ltd
cited By 8
Keywords: apatite; borehole; Cenozoic; exhumation; fission track dating; historical perspective; plate tectonics; subduction; tectonic evolution; China; Songliao Basin

Toarcian climate and carbon cycle perturbations – its impact on sea-level changes, enhanced mobilization and oxidation of fossil organic matter - Ruebsam, Wolfgang; Pie'nkowski, Grzegorz; Schwark, Lorenz (Earth and Planetary Science Letters, 2020)

Two multi-stigmate gomphonema species of Africa: Gomphonema kalahariense (nom. nov., stat. nov.) and gomphonema chemeron (sp. nov.) - Stone, Jeffery R.; Kociolek, J. Patrick; Westover, Karlyn S. (Phytotaxa, 2020)

The Lake Chad hydrology under current climate change - Pham-Duc, Binh; Sylvestre, Florence; Papa, Fabrice; Frappart, Fr'ed'eric; Bouchez, Camille; Cr'etaux, Jean-Francois (Scientific Reports, 2020)
Lake Chad, in the Sahelian zone of west-central Africa, provides food and water to 50 million people and supports unique ecosystems and biodiversity. In the past decades, it became a symbol of current climate change, held up by its dramatic shrinkage in the 1980s. Despites a partial recovery in response to increased Sahelian precipitation in the 1990s, Lake Chad is still facing major threats and its contemporary variability under climate change remains highly uncertain. Here, using a new multi-satellite approach, we show that Lake Chad extent has remained stable during the last two decades, despite a slight decrease of its northern pool. Moreover, since the 2000s, groundwater, which contributes to 70% of Lake Chad’s annual water storage change, is increasing due to water supply provided by its two main tributaries. Our results indicate that in tandem with groundwater and tropical origin of water supply, over the last two decades, Lake Chad is not shrinking and recovers seasonally its surface water extent and volume. This study provides a robust regional understanding of current hydrology and changes in the Lake Chad region, giving a basis for developing future climate adaptation strategies. © 2020, The Author(s).

U-Th dating of lake sediments: Lessons from the 700 ka sediment record of Lake Jun'in, Peru - Chen, C.Y.; McGee, D.; Woods, A.; P'erez, L.; Hatfield, R.G.; Edwards, R.L.; Cheng, H.; Valero-Garc'es, B.L.; Lehmann, S.B.; Stoner, J.S.; Schwalb, A.; Tal, I.; et al. (Quaternary Science Reviews, 2020)
Deep sediment cores from long-lived lake basins are fundamental records of paleoenvironmental history, but the power of these reconstructions has been often limited by poor age control. Uranium-thorium (U-Th) dating has the potential to fill a gap in current geochronological tools available for such sediment archives. We present our systematic approach to U-Th date carbonate-rich sediments from the ∼100m drill core from Lake Jun'in, Peru. The results form the foundation of an age-depth model spanning ∼700 kyrs. High uranium concentrations (0.3 –4 ppm) of these sediments allow us to date smaller amounts of material, giving us the opportunity to improve sample selection by avoiding detrital contamination, the greatest factor limiting the success of previous U-Th dating efforts in other lake basins. Despite this advantage, the dates from 174 analyses on 55 bulk carbonate samples reveal significant scatter that cannot be resolved with traditional isochrons, suggesting that at least some of the sediments have not remained closed systems. To understand the source of noise in the geochronological data, we first apply threshold criteria that screen samples by their U/Th ratio, reproducibility, and δ234Uinitial value. We then compare these results with facies types, trace element concentrations, carbonate and total organic carbon content, color reflectance, mineralogy, and ostracode shell color to investigate the causes of open system behavior. Alongside simulations of the isotopic evolution of our samples, we find that the greatest impediment to U-Th dating of these sediments is not detrital contamination, but rather post-depositional remobilization of uranium. Examining U-Th data in these contexts, we identify samples that have likely experienced the least amount of alteration, and use dates from those samples as constraints for the age-depth model. Our work has several lessons for future attempts to U-Th date lake sediments, namely that geologic context is equally as important as the accuracy and precision of analytical measurements. In addition, we caution that significant geologic scatter may remain undetected if not for labor intensive tests of reproducibility achieved through replication. As a result of this work, the deep sediment core from Lake Jun'in is the only continuous record in the tropical Andes spanning multiple glacial cycles that is constrained entirely by independent radiometric dates. © 2020 Elsevier Ltd
cited By 7
Keywords: Binary alloys; Carbonation; Core drilling; Geochronology; Lake pollution; Lakes; Minerals; Organic carbon; Sediments; Thorium compounds; Trace elements; Uranium alloys; Accuracy and precision; Color reflectance; Radiometric dates; Reproducibilities; System behaviors; Total organic carbon content; Trace element concentrations; Uranium concentration; Thorium alloys; biostratigraphy; color; core analysis; facies analysis; geochronology; lacustrine deposit; ostracod; paleoenvironment; remobilization; shell; total organic carbon; trace element; uranium series dating; Junin; Lake Junin; Peru; Ostracoda

Ultramafic rock carbonation: Constraints from listvenite core BT1B, Oman Drilling Project - Beinlich, Andreas; Pl{umper, Oliver; Boter, Esm'ee; M{uller, Inigo A; Kourim, Fatma; Ziegler, Martin; Harigane, Yumiko; Lafay, Romain; Kelemen, Peter B; Team, Oman Drilling Project Science (Journal of Geophysical Research: Solid Earth, 2020)
The occurrence of the quartz-carbonate alteration assemblage (listvenite) in ophiolites indicates that ultramafic rock represents an effective sink for dissolved CO2. However, the majority of earlier studies of ultramafic rock carbonation had to rely on the surface exposure of reaction textures and field relationships. Here we present the first observations on ultramafic rock alteration obtained from the 300 m deep BT1B drill hole, ICDP Oman Drilling Project, allowing for a continuous and high-resolution investigation. Hole BT1B recovered continuous drill core intersecting surface alluvium, 200 m of altered ultramafic rock comprising mainly listvenite and minor serpentinite bands at 90 and 180 m depth, and 100 m of the underlying metamorphic sole. Textural evidence suggests that the carbonation of fully serpentinized harzburgite commenced by non-equilibrium growth of spheroidal carbonate characterized by sectorial zoning resulting from radially oriented low-angle boundaries. In the serpentinite, carbonate spheroids are composed of alternating magnesite cores and dolomite rims, whereas texturally similar carbonate in the listvenite is composed of Fe-rich magnesite cores and Ca-Fe-rich magnesite rims. The distinct compositions and mineral inclusions indicate that the carbonation extent was controlled by fluid accessibility resulting in the simultaneous formation of limited carbonate in the serpentinite bands and complete carbonation in the listvenite parts of BT1B. The presence of euhedral magnesite overgrowing spheroidal carbonate in the listvenite suggests near-equilibrium conditions during the final stage of carbonation. The carbonate clumped isotope thermometry constrains carbonate crystallization between 50 °C and 250 °C, implying repeated infiltration of reactive fluids during ophiolite uplift and cooling. ©2020. The Authors.
cited By 24
Keywords: carbonate rock; chemical alteration; crystallization; geothermometry; ophiolite; texture; ultramafic rock; Oman

Variations in the physical and mechanical properties of rocks from different depths in the Songliao Basin under uniaxial compression conditions - Lu, Y.; Li, C.; He, Z.; Gao, M.; Zhang, R.; Xie, H. (Geomechanics and Geophysics for Geo-Energy and Geo-Resources, 2020)
With the development of deep energy resources, understanding variations in the physical and mechanical properties of rocks at different depths is significant. In this paper, core samples from ten different burial depths (1000 m, 1300 m, 1600 m, 1850 m, 2600 m, 3500 m, 4800 m, 5100 m, 5600 m, and 6400 m) were collected from the Songke No. 2 (SK-2) well and the Daqing Oilfield. To the best of our knowledge, this is the first study involving the physical property and uniaxial compression testing of rock cores from such a large range of burial depths. The experimental results show that the content of weak phase minerals decreases with increasing depth. The change in the hard phase minerals varies nonlinearly with depth. From 3500 to 5600 m, the content of hard phase minerals decreases, while the content of the middle phase minerals increases. The elastic modulus exponentially increases with increasing depth, while Poisson’s ratio decreases with increasing depth. Additionally, the uniaxial compressive strength displays a nonlinear logarithmic increase with increasing depth. Finally, the effects of petrophysical properties on the mechanical behavior of rock at different depths are discussed. The elastic modulus, Poisson’s ratio, and compressive strength all have a negative correlation with the content of weak phase minerals. These results have important value for studying the mechanics of rocks at different depths. © 2020, Springer Nature Switzerland AG.
cited By 13
Keywords: Compression testing; Elastic moduli; Energy resources; Minerals; Petrophysics; Rocks; Daqing oilfields; Important value; Mechanical behavior; Negative correlation; Petrophysical properties; Physical and mechanical properties; Uniaxial compression testing; Uniaxial compressive strength; Compressive strength

Vivianite formation in ferruginous sediments from Lake Towuti, Indonesia - Vuillemin, Aurèle; Friese, Andr'e; Wirth, Richard; A. Schuessler, Jan; M. Schleicher, Anja; Kemnitz, Helga; L{ucke, Andreas; W. Bauer, Kohen; Nomosatryo, Sulung; Von Blanckenburg, Friedhelm; Simister, Rachel; G. Ordoñez, Luis; et al. (Biogeosciences, 2020)
Ferruginous lacustrine systems, such as Lake Towuti, Indonesia, are characterized by a specific type of phosphorus cycling in which hydrous ferric iron (oxyhydr) oxides trap and precipitate phosphorus to the sediment, which reduces its bioavailability in the water column and thereby restricts primary production. The oceans were also ferruginous during the Archean, thus understanding the dynamics of phosphorus in modern-day ferruginous analogues may shed light on the marine biogeochemical cycling that dominated much of Earth’s history. Here we report the presence of large crystals ( > 5 mm) and nodules (> 5 cm) of vivianite – a ferrous iron phosphate – in sediment cores from Lake Towuti and address the processes of vivianite formation, phosphorus retention by iron and the related mineral transformations during early diagenesis in ferruginous sediments. Core scan imaging, together with analyses of bulk sediment and pore water geochemistry, document a 30m long interval consisting of sideritic and non-sideritic clayey beds and diatomaceous oozes containing vivianites. Highresolution imaging of vivianite revealed continuous growth of crystals from tabular to rosette habits that eventually form large (up to 7 cm) vivianite nodules in the sediment. Mineral inclusions like millerite and siderite reflect diagenetic mineral formation antecedent to the one of vivianite that is related to microbial reduction of iron and sulfate. Together with the pore water profiles, these data suggest that the precipitation of millerite, siderite and vivianite in soft ferruginous sediments stems from the progressive consumption of dissolved terminal electron acceptors and the typical evolution of pore water geochemistry during diagenesis. Based on solute concentrations and modeled mineral saturation indices, we inferred vivianite formation to initiate around 20m depth in the sediment. Negative 56Fe values of vivianite indicated incorporation of kinetically fractionated light Fe2C into the crystals, likely derived from active reduction and dissolution of ferric oxides and transient ferrous phases during early diagenesis. The size and growth history of the nodules indicate that, after formation, continued growth of vivianite crystals constitutes a sink for P during burial, resulting in long-term P sequestration in ferruginous sediment. © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License.
Keywords: Greater Sunda Islands; Lake Towuti; Malili Lakes; South Sulawesi; Sulawesi; Sunda Isles; diagenesis; electron; geochemistry; iron oxide; phosphate; phosphorus; porewater; saturation; sediment analysis; siderite; vivianite; water column

Magnetite biomineralization in ferruginous waters and early Earth evolution - Bauer, K.W.; Byrne, J.M.; Kenward, P.; Simister, R.L.; Michiels, C.C.; Friese, A.; Vuillemin, A.; Henny, C.; Nomosatryo, S.; Kallmeyer, J.; Kappler, A.; Smit, M.A.; et al. (Earth and Planetary Science Letters, 2020)
Burial of large quantities of magnetite (Fe(II)Fe(III)2O4) in iron formations (IFs) likely contributed to the protracted oxidation of Earth's surface during the Precambrian Eons. Magnetite can form through a diversity of biological and abiotic pathways and its preservation in IFs may thus be variably interpreted as the result of some combination of these processes. Such interpretations give rise to divergent pictures of the Precambrian Earth system and models for its evolution through time. New knowledge on the contribution of specific magnetite formation pathways is, therefore, needed to accurately tether our conceptual and numerical models to the geologic record. To constrain pathways of magnetite formation under ferruginous conditions, we conducted geochemical and multi-method microspectroscopic analyses on particles obtained from the water columns and sediments of ferruginous lakes Matano and Towuti, in Indonesia. We find that biologically reactive Fe(III) mineral phases are reduced in the anoxic waters of both lakes, causing the formation of primary authigenic magnetite, directly in the water column. This water column magnetite often takes conspicuous framboidal forms, which given the link to microbial Fe(III) reduction, may provide a biological signature on early Earth and by extension, other planetary bodies. The consumption of more biologically reactive forms of Fe(III) and the resulting delivery of primary magnetite to underlying sediments promotes the burial of oxidized equivalents and implies that primary magnetite formation could have been a principal pathway of Fe delivery to IFs. Combined, the removal of Fe from Earth's surface through biologically induced magnetite formation and subsequent burial in IFs, suggests that seawater chemistry and the microbially mediated reactions that cause magnetite formation played key roles in Earth system evolution and in setting the pace for planetary oxidation through the Precambrian Eons. © 2020
Keywords: Greater Sunda Islands; Lake Matano; Lake Towuti; Malili Lakes; South Sulawesi; Sulawesi; Sunda Isles; Biology; Biomineralization; Geologic models; Lakes; Magnetite; Ore reduction; Oxidation; Abiotic pathways; Biological signatures; Earth' s surface; Magnetite formation; Mediated reactions; Planetary bodies; Precambrian eons; Seawater chemistry; biomineralization; early Earth; evolution; lacustrine deposit; magnetite; mass spectrometry; oxidation; Precambrian; water column; Iron compounds

Well Bore Stability Technology Using Blocking Drilling Fluid System Suitable for the Deep High Temperature Cracked Strata in Well Songke-2; [松科2井深部高温龟裂岩层封堵型钻井液稳定井壁技术] - Wu, Xiaoming; Zheng, Wenlong; Zou, Yuliang (Diqiu Kexue - Zhongguo Dizhi Daxue Xuebao/Earth Science - Journal of China University of Geosciences, 2020)
To solve the problem of drilling in severely cracked hard rock in deep high temperature and high pressure (HTHP) stratum of Well Songke-2, mechanical analysis and physical simulation experiment were used to clarify the factors affecting the thickness of the plugging layer in this study. The sealing effect of high-strength skeleton particles and HT deformable soften particles was verified through HTHP filtration test, and the on-site operation pressure was calculated and controlled. The self-locking mechanical model of the three-particle bridge group skeleton was established, and the anti-destructive ability formula of the single bridge group was derived. Compared with the blank formula, emulsified asphalt, oxidized asphalt and sulfonated asphalt can reduce the HTHP water loss volume by 56%, 44% and 48%, respectively. Particle size and strength, crack width and pressure difference have important influence on the thickness of the plugging layer. A quick blocking effect can be achieved by combining the rigid plugging agent with deformable plugging particles. Based on the above analysis and tests, the drilling pressure in the operation was effectively controlled in conjunction with the on-site technology, and the compaction and anti-collapse effect under moderate positive pressure difference was realized. With the techniques mentioned above, the fifth spud of Well Songke-2 was completed successfully with the open-hole section from 5 910 to 7 018 m. © 2020, Editorial Department of Earth Science. All right reserved.
Keywords: Asphalt; Cracks; Deformation; Drilling fluids; Emulsification; Infill drilling; Musculoskeletal system; Particle size; Pressure effects; Drilling fluid systems; Emulsified asphalts; High temperature and high pressures (HTHP); Mechanical analysis; Physical simulation experiment; Positive pressure; Pressure differences; Wellbore stability; Particle size analysis

Winding down the Chicxulub impact: The transition between impact and normal marine sedimentation near ground zero - Whalen, M.T.; Gulick, S.P.S.; Lowery, C.M.; Bralower, T.J.; Morgan, J.V.; Grice, K.; Schaefer, B.; Smit, J.; Orm{o, J.; Wittmann, A.; Kring, D.A.; Lyons, S.; et al. (Marine Geology, 2020)
The Chicxulub impact led to the formation of a 200-km wide by 1-km deep crater on M'exico's Yucat'an 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
cited By 14

The late quaternary tectonic, biogeochemical, and environmental evolution of ferruginous Lake Towuti, Indonesia - Russell, James M.; Bijaksana, Satria; Deino, Alan; Hafidz, Abdul; Haffner, Doug; Hasberg, Ascelina K.M.; Morlock, Marina; Rintelen, Thomas; Sheppard, Rachel; Stelbrink, Bj{orn; Stevenson, Janelle (Palaeogeography, Palaeoclimatology, Palaeoecology, 2020)
There is a paucity of long and continuous continental records from South East Asia suitable to inform on past changes and underlying causes of the region's climate and associated diverse ecosystem evolution during the late Quaternary. In 2015, the Towuti Drilling Project (TDP) collected a series of sedimentary drill cores from the tectonic, ferruginous, and highly biodiverse Lake Towuti, Sulawesi, one of Indonesia's oldest lakes. The drill cores contain 1 Myr of uninterrupted lacustrine sedimentation to document long-term environmental and climatic change in the tropical western Pacific, the impacts of geological and environmental changes on the biological evolution of aquatic taxa, and the geomicrobiology and biogeochemistry of metal-rich, ultramafic-hosted lake sediment. Here we use lithostratigraphic, mineralogical, geochemical, and geochronological datasets to elucidate Lake Towuti's tectonic emergence and its biogeochemical responses to climatic and volcanic forcings since lake formation. Our data document that Lake Towuti emerged during a phase of accelerated tectonic subsidence from a landscape characterized by active river channels, shallow lakes and swamps into a permanent lake at 1 Ma. The lacustrine sediments feature quasi-rhythmic alternations of green organic rich and red sideritic clay beds reflecting changes in lake mixing and biogeochemistry as a response to temperature and hydrological changes driven by orbital-scale changes in insolation and continental ice volume through the mid- to late Pleistocene. Clay deposition is interrupted by two beds of diatomaceous oozes composed primarily of planktonic diatoms that reflect phases of substantially increased primary productivity. The occurrence of these diatomaceous oozes in close association with multiple tephra beds suggests a trophic state change driven by the addition of volcanically sourced P, possibly in combination with a lake mixing state that supports recycling of P. Data on lake age and ontogeny are also in agreement with molecular-clock estimates of 0.7 Ma (0.18 –1.37 Ma) for the divergence of Lake Towuti's Telmatherinid fishes from a riverine ancestor. Our data therefore are compatible with an evolutionary model in which Lake Towuti's endemic fauna is a result of geographic speciation in the Malili Lakes, a set of large lakes in Southeast Sulawesi, driven by physical or chemical dispersal limits imposed by the regional rivers and lakes. More detailed chronological constraints and refined climate and environmental proxy datasets are currently in preparation and will help to paint a more detailed history of the region's climate and environmental history in future studies. © 2020 Elsevier B.V.
Keywords: Far East; Greater Sunda Islands; Lake Towuti; Malili Lakes; Pacific Ocean; Pacific Ocean (West); South Sulawesi; Sulawesi; Sunda Isles; Bacillariophyta; Pisces; Telmatherinidae; biogeochemistry; climate variation; diatom; dispersal; lacustrine deposit; Pleistocene; Quaternary; speciation (biology); subsidence

The Iceland Deep Drilling Project at Reykjanes: Drilling into the root zone of a black smoker analog - Friðleifsson, G.Ó.; Elders, W.A.; Zierenberg, R.A.; Fowler, A.P.G.; Weisenberger, T.B.; Mesfin, K.G.; Sigurðsson, Ó.; N'ielsson, S.; Einarsson, G.; Óskarsson, F.; Guðnason, E.'A.; Tulinius, H.; et al. (Journal of Volcanology and Geothermal Research, 2020)
The aim of the Iceland Deep Drilling Project is to drill into supercritical geothermal systems and examine their economic potential. The exploratory well IDDP-2 was drilled in the Reykjanes geothermal field in SW Iceland, on the landward extension of the Mid-Atlantic Ridge. The Reykjanes geothermal field produces from a <300 °C reservoir at 1 to 2.5 km depth and is unusual because it is recharged by seawater. The well was cased to 3000 m depth, and then angled towards the main up-flow zone of the system, to a total slant depth of 4659 m ( 4500 m vertical depth). Based on alteration mineral assemblages, joint inversion of wireline logging, and rate of heating measurements, the bottom hole temperature is estimated to be about 535 °C. The major problem encountered during drilling was the total loss of circulation below 3 km depth and continuing to the final depth. Drilling continued without recovering drill cuttings, consequently spot coring provided the only deep rock samples from the well. These cores are characteristic of a basaltic sheeted dike complex, with hydrothermal alteration mineral assemblages that range from greenschist to amphibolite facies, hornblende hornfels, and pyroxene hornfels, allowing the opportunity to investigate water-rock interaction in the active roots of an analog of a submarine hydrothermal system. As they have not yet been sampled, the composition of the deep fluids at Reykjanes is unknown at present. Cold water is currently being injected with the aim of enhancing permeability at depth, before allowing the well to heat up prior to flow tests planned for early 2019. The well has at least two fluid feed zones, a dominant one at 3.4 km depth and a second smaller one at 4.5 km. Extensive geophysical surveys of the Reykjanes Peninsula completed recently allow correlation of geophysical signals with rocks properties and in-situ conditions in the subsurface. Earthquake activity monitored with a local seismic network during drilling the IDDP-2 drilling detected abundant small earthquakes (ML ≤ 2) within the depth range of 3 –5 km. A zone at 3 –5 km depth below the producing geothermal field that was generally aseismic prior to drilling, but became seismically active during the drilling. The drilling of the IDDP-2 has achieved number of scientific and engineering firsts. It is the deepest and hottest drill hole so far sited on an active mid-ocean spreading center. It penetrated an active supercritical hydrothermal environment at depths analogous to those postulated as the high temperature reaction zones feeding black smoker systems. © 2018 Elsevier B.V.
cited By 29
Keywords: Clay alteration; Drilling fluids; Earthquakes; Effluent treatment; Geothermal fields; Hydraulic structures; Mineral exploration; Rhenium compounds; Rock drills; Silicate minerals; Smoke; Supercritical fluids; Black smokers; Deep drilling; Geothermal; IDDP; Reykjanes; Infill drilling; amphibolite facies; analog model; black smoker; Deep Sea Drilling Project; drilling; exploration; flow field; geothermal system; greenschist facies; hydrothermal alteration; mineral alteration; spreading center; supercritical flow; Atlantic Ocean; Iceland; Mid-Atlantic Ridge; Reykjanes Peninsula

Stratigraphic correlation and splice generation for sediments recovered from a large-lake drilling project: an example from Lake Jun'in, Peru - Hatfield, R.G.; Woods, A.; Lehmann, S.B.; Weidhaas, N.; Chen, C.Y.; Pierdominici, S.; Stoner, J.S.; Abbott, M.B.; Rodbell, D.T. (Journal of Paleolimnology, 2020)
Sediment records from deep-drilling projects such as those carried out by the International Continental Scientific Drilling Program are often tens to hundreds of meters in length. To ensure the complete recovery of a stratigraphic section, a basin is usually cored multiple times in adjacent holes so that gaps between sequential cores, poorly recovered sections, or intervals affected by disturbance can be bridged or replaced with sediments from another hole. Stratigraphic correlation, the alignment of stratigraphically-equivalent horizons in cores from different holes in a common-depth scale, and splice generation, the integration of the most-representative core sections into a composite-stratigraphic section, are essential steps in this process to both evaluate and synthesize the recovered-sediment record and focus the scientific analyses. However, these undertakings can be complex and are inherently subjective, making the need for the development of a single robust stratigraphic section early in the project critical to its success. Despite this, the steps between core recovery and on-splice data generation are rarely published in sufficient detail to allow reconstruction, or refinement, of the composited record at a later date. To increase the transparency of how the composite record is created, and to provide a template for future projects, we detail the step-by-step approaches and decisions involved in generating the composite-depth scale and complete-stratigraphic splice following recovery of sediments from Lake Jun'in, Peru. We first explain the details and nuances of different drilling-depth scales before describing how we integrated different physical property records to generate the composite-depth scale and complete-stratigraphic splice. Here, we show that due to the complex stratigraphy in the Lake Jun'in sediments, high-resolution line-scan images of the cores offer millimeter-scale precision for construction of the primary-stratigraphic splice at a resolution not afforded by other physical property data. Finally, through comparison of the spliced record to physical-property records acquired in situ on the borehole, we demonstrate that the stratigraphic splice is an accurate representation of the sediment accumulated in the Lake Jun'in basin. © 2019, Springer Nature B.V.
cited By 9
Keywords: deep drilling; historical record; lacustrine deposit; physical property; project assessment; reconstruction; recovery; scale effect; sediment core; stratigraphic correlation; Junin; Lake Junin; Peru

Sedimentary System of Denglouku Formation in Xujiaweizi Area, Songliao Basin - Fu, X.-L.; Huo, Z.-W.; Wang, J.; Cui, K.-N.; Jin, M.-Y.; Zhu, Z.-M.; Bai, X.-J.; Liu, H.; Yue, B. (Springer Series in Geomechanics and Geoengineering, 2020)
Denglouku Formation in Xujiaweizi area is an important field needing urgent breakthroughs for deep gas exploration in northern Songliao Basin. In order to clarify the distribution characteristics of sedimentary facies of Denglouku Formation in Xujiaweizi area, the isochronal framework is established and the sedimentary facies is comprehensively analyzed, by core observation of sedimentary facies, sedimentary cycle analysis by logging data and comprehensive analysis of seismic attribute slices. The results show that: The Denglouku Formation in Xujiaweizi area mainly develops 6 sedimentary facies from bottom to top, the alluvial fan and fan delta, the lake and braided river delta, the river and lake pan-plane, 10 sedimentary subfacies and 20 sedimentary microfacies. Vertically, the development of sedimentary system in the first member of Denglouku Formation is limited, which controlled by unconformity. The sedimentary facies system of Denglouku Formation is alluvial fan-fan delta-lake sedimentary system in the first member, braided river delta-intermittent lake depositional system in the second-third member, and fluvial sedimentary system in the fourth member. The fan delta front glutenite, braided delta distributary channel coarse sandstone and braided channel thick sandstone provide favorable reservoir space for gas accumulation. Accurate identification of fine sedimentary facies of Denglouku Formation in Xujiaweizi area provides an important basis for further exploration and deployment, and has positive exploration significance. © 2020, Springer Nature Singapore Pte Ltd.
cited By 0
Keywords: Deposition; Lakes; Petroleum prospecting; Rivers; Sandstone; Braided river deltas; Comprehensive analysis; Denglouku formations; Depositional system; Distributary channels; Distribution characteristics; Sedimentary micro-facies; Sedimentary systems; Sedimentology; alluvial fan; depositional environment; facies; fan delta; gas field; hydrocarbon exploration; seismic data; spatial distribution; unconformity; well logging; China; Heilongjiang; Songliao Basin; Xujiaweizi

Seismic attribute analysis of Chicxulub impact crater - Salguero-Hern'andez, E.; P'erez-Cruz, L.; Urrutia-Fucugauchi, J. (Acta Geophysica, 2020)
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.
cited By 2

Shallow geothermal potential of the snake river plain - Batir, J.; Richards, M.; Hornbach, M.; Blackwell, D.; Kolker, A.; Waibel, A. (Transactions - Geothermal Resources Council, 2020)
The Snake River Plain (SRP) terrestrial heat flow and subsurface thermal regime are not well understood but are important for assessing the local geothermal resource potential, both for conventional and for Enhanced Geothermal Systems (EGS) development in the region. Resource evaluation for the SRP is complicated by the disparate data density, along with the known lateral advection of heat in the Eastern Snake River Plain Aquifer and vertical heat transport by fluids in the bounding faults, primarily in the southwestern section. Fortunately, recent studies, e.g., the Snake River Plain Play Fairway Analysis, the Idaho FORGE site, and site-specific investigations, which included drilling within the Camas Prairie and on the Mountain Home Air Force Base, near Twin Falls, and in the Eastern Snake River Plain as part of the HOTSPOT Project, add both additional drilling and geophysical data. The SMU Geothermal Laboratory has conducted detailed studies of SRP tectonics and heat flow since the 1970's and used this knowledge as part of the EGS geothermal potential estimation for the conterminous United States in 2006 and again in 2011, calculating geothermal potential from 3.5 km to 10 km depth. Recent temperature modeling refined the calculation methodology to estimate shallow (1 km to 4 km) resource potential using an improved thermal conductivity model and incorporation of shallow groundwater flow. By incorporating the new SRP geology, geophysics, and 206 thermal data sites into the SMU thermal modeling methodology, this project updates the resource estimate for the SRP, and generates new temperature-at-depth maps for the shallow subsurface (1 km to 4 km). The project results highlight the EGS potential resource areas (≥150°C) and areas with more exploration risks based on minimal and/or low-quality data. The newest temperature modeling results suggest EGS potential is near five times greater in the SRP than previously estimated. © 2020 Geothermal Resources Council. All rights reserved.
cited By 1
Keywords: Aquifers; Geothermal fields; Geothermal prospecting; Geothermal wells; Groundwater flow; Heat transfer; Infill drilling; Landforms; Rivers; Thermal conductivity; Additional drillings; Enhanced geothermal systems; Geothermal potential; Geothermal resources; Subsurface thermal regime; Temperature modeling; Terrestrial heat flow; Thermal conductivity model; Groundwater resources

Shallow structure of the Chalco and Xochimilco sub-basins (southern Mexico basin) based on wave propagation modelling and seismic data - Gonz'alez-Flores, E.; Campos-Enr'iquez, J.O.; Wong, R.V.; Torres-Verd'in, C.; Rivera-Recillas, D.E.; Camacho-Ram'irez, E. (Journal of South American Earth Sciences, 2020)
The shallow structures of the Chalco and Xochimilco sub-basins (southeastern Mexico Basin) are established based on a seismic line that stretches trough both depressions. Interpretation of the seismic line was constraint by the stratigraphic column cut by the approximately 3000 m deep Tulyehualco well. The seismic line was converted to depth based on a vertical transverse isotropy velocity model determined from the interval, and root mean square (rms) velocities of the geologic units as established at the Tulyehualco deep well. P-wave modelling confirmed the results. The volcano-sedimentary infill established is consistent with the stratigraphic column of the 502 m deep MexiDrill borehole. It was possible to establish 1) the base of the fine stratified lacustrine sediments, and 2) the top of the basalts along the Xochimilco and Chalco sub-basins. The Xochimilco and Chalco sub-basins are separated by a shallow structural high (interpreted as due volcanic flows) against which the lacustrine sediments abut. A conspicuous anticline shaped structural high (adjacent to Xico tuff ring) divides the Chalco sub-basin into two depressions. The top of the basaltic basement matches with the upper volcanic unit horizon. In the western trough, the basement gets deeper from east to west (from 336 m at the structural high, to 660 m to the west). Immediately east of the anticline-shaped structural high, the basement is located at 510 m. Beneath the Xochimilco trough (at 180 m approximately) the volcanic basement shallows up smoothly northwestwards. In the eastern part of the Xochimilco sub-basin, the shallow lacustrian sediments are relatively thin. Northwestwards of the Tulyehualco well, their thickness diminishes. This apparent thinning is accounted by the fact that there the seismic line occupies the northern rim of the depression. Reflections in the upper 300 m of the section are not continuous. Beneath the central part of Chalco lake the reflectors are horizontal with a slight westward dip. At both sides of this central zone, reflectors are inclined or have dome shapes. This indicates that deposition along the Chalco sub-basin has been deformed. The thickness of the reflections associated with the fine laminated to volcanoclastic material transition zone is approximately constant, but thins and finally abuts against the structural high. In the eastern trough, seismic reflections at the shallow first 300 m are not as fine as in the western trough. These low magnitude seismic reflections might be associated with coarse fluvial volcanoclastic material from nearby Popocat'eptl volcano. Seismic amplification in these two tectonic depressions by numerical modelling of seismic wave propagation can be based on the structure here established. Between 8 and 9 high amplitude reflectors in the first 300 m of the infill sequence are interpreted as due to impedance contrasts between geological units. Density and velocity logs along the MexiDrill borehole support this interpretation. Shallow strata are approximately 30 m thick. Towards the basin base, the strata are thicker (70 m approximately). These thicknesses are consistent with the nature of the volcano-sedimentary infill cut by the MexiDrill borehole. In particular, each seismic reflection would represent a sedimentation cycle of approximately 30,000 years (corresponding to a mean thickness of 30 m). If a sedimentation rate of 0.8 mm per year holds along the first 200 –300 m of the basin infill (i.e., neglecting compaction effects, etc.) then this upper sequence comprises a record of paleo-ambiental changes that affected the southern Mexico Basin during the last 250,000 to 375,000 years. © 2020 The Authors
cited By 0
Keywords: basin analysis; data interpretation; P-wave; seismic data; stratigraphy; transverse isotropy; wave modeling; wave propagation; Chalco; Federal District [Mexico]; Mexico City; Mexico [Mexico (NTN)]; Mexico [North America]; Xochimilco

Shocked titanite records Chicxulub hydrothermal alteration and impact age - Timms, N.E.; Kirkland, C.L.; Cavosie, A.J.; Rae, A.S.P.; Rickard, W.D.A.; Evans, N.J.; Erickson, T.M.; Wittmann, A.; Ferrière, L.; Collins, G.S.; Gulick, S.P.S. (Geochimica et Cosmochimica Acta, 2020)
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 > 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
cited By 16

Source/reservoir characteristics and shale gas “sweet spot” interval in Shahezi mudstone of Well SKII in Songliao Basin, NE China - Cui, Jingwei; Zhu, Rukai; Wang, Chengshan; Gao, Yuan; Li, Sen; Kang, Lei (Arabian Journal of Geosciences, 2020)

Stress Field Interactions Between Overlapping Shield Volcanoes: Borehole Breakout Evidence From the Island of Hawai'i, USA - Millett, John M.; K{uck, Jochem K. M.; Thomas, Donald; Jerram, Dougal A.; Planke, Sverre; Haskins, Eric; Lautze, Nicole; Galland, Olivier (Journal of Geophysical Research: Solid Earth, 2020)
Knowledge of the in situ stress state of the Earth's crust plays a key role in understanding geological processes including plate tectonics, earthquakes, slope failure, and igneous emplacement. In this paper, we determine the in situ stress orientation from the PTA2 borehole on the island of Hawai'i, drilled into a lava flow dominated sequence between Mauna Kea and Mauna Loa. High-resolution acoustic images were collected from the open hole interval 886 m to 1,567 m. Based on identification of 371 borehole breakouts for a total length of 310 m, the mean orientation of the minimum horizontal principal stress is N106° and remains constant across different volcanic rock fabrics. Changes in borehole breakout shape are linked to the different strength of volcanic facies and intra-facies. The orientation of the present-day stress field at Mauna Kea deviates from the plate forces and regional tectonic stress field. We interpret the compressive stress regime at the PTA2 site as resulting from the competing gravitational fields of the large topographic highs of Mauna Kea and Mauna Loa. Our study reveals that the mass accumulation associated with shield volcano growth imparts significant local variations to the subsurface stress state on volcanic islands consisting of overlapping shield volcanoes. The results have significant implications for stress accumulation leading to brittle failure and flank collapse, along with potentially influencing magma accumulation and ascent pathways during volcanic island evolution. This study provides the first insights into the orientation of the present-day stress field between the major island forming shield volcanoes of Hawai'i. ©2020. The Authors.
Keywords: Hawaii [(ISL) Hawaiian Islands]; Hawaii [United States]; Hawaiian Islands; Mauna Kea; Mauna Loa; borehole breakout; in situ stress; lava flow; shield volcano; stress field; volcanic island

The ICDP dead sea deep drilling project – introduction - Stein, M.; Goldstein, S.L. (Quaternary Science Reviews, 2020)
cited By 2
Keywords: deep drilling; deep sea; maintenance; paleoenvironment; reconstruction

Stress-state differences between sedimentary cover and basement of the Songliao Basin, NE China: In-situ stress measurements at 6 –7 km depth of an ICDP Scientific Drilling borehole (SK-II) - Wang, B.; Sun, D.; Chen, Q.; Lin, W.; Li, A.-W.; Cao, H. (Tectonophysics, 2020)
The stress state down to the basement within sedimentary basins yet remains poorly understood. The anelastic strain recovery (ASR) method was employed to measure the stress state in the SK-II borehole in the Songliao Basin, Northeast China. The results show that the stress state differs significantly between the sedimentary cover and basement. In the sedimentary cover (6296 –6335 m), the maximum principal stress σ1 is nearly vertical, which is in the normal faulting stress regime dominated by gravitation, in accordance with the normal faults observed on seismic reflection profiles within the sedimentary cover. In contrast, the basement (6646 –6846 m) shows that σ1 is nearly horizontal, suggesting a strike-slip or reverse-faulting regime. The stress state of the basement is close to the reasonable stress condition for the Eurasian Plate far from a western Pacific plate subduction zone and consistent with the focal mechanisms of earthquakes (7 –15 km) in the vicinity of ICDP SK-II borehole. The difference of stress state may imply that the far-field stress generated by the western Pacific plate has limited effects on the sedimentary cover, an increase in thickness correlates with an increasing influence of tectonic stress with depth. © 2020 Elsevier B.V.
cited By 4
Keywords: Boreholes; Buildings; Sedimentology; Stresses; Strike-slip faults; Anelastic strain recovery; In-situ stress measurement; Insitu stress; Maximum principal stress; Scientific drilling; Seismic reflection profiles; Songliao basin; Stress state; Fault slips; anelasticity; basement rock; borehole; depth; drilling; in situ measurement; normal fault; Pacific plate; sedimentary basin; seismic reflection; strain analysis; stress field; China; Songliao Basin

Superdeep Drilling and Its Impact on the Seismic Models of the Fennoscandian Shield - Sharov, N.V. (Springer Proceedings in Earth and Environmental Sciences, 2020)
Attempts to interpret the origin of seismic boundaries in the crystalline crust in the Fennoscandian Shield from deep drilling records and available geological and geophysical data were made by a number of authors. This article contains an overview of the most essential results reported so far. Deep drilling was conducted in several regions of the Fennoscandian Shield: Kola, Russia (SG-3), to a depth of 12,262 m (1970 –1990); Gravberg (GR) and Stenberg-I, Central Sweden, to a depth of 6337 m (1986 –1987); and 6529 m (1991 –1992); Outokumpu (OU), SE Finland, to a depth of 2516 m (2004 –2005); Pogranichnaya (P-1), Sredny Peninsula, Murmansk Region, Russia, to a depth of 5200 m (2004 –2006); and Onega, Central Karelia, Russia (ON), to a depth of 3537 m (2007 –2008). The results obtained were analyzed. They show considerable discrepancies between forecast seismic-geological models and the actual structure of the upper portion of the continental crust. Deep drilling has proved that heterogeneities in the upper portion of the crystalline crust, indicated by geophysical data, are due to changes in the composition and physical conditions of deep-seated rocks. Therefore, even approximate rock composition cannot be uniquely estimated from elastic wave velocities alone. Deep drilling showed the real pattern and origin of low-velocity zones in the upper portion of the crust and did not show that layers become more homogeneous with depth. The origin of intra-crustal seismic boundaries could be associated with various factors, such as variations in mineralogical composition, structural and textural differences between the rocks, and a thermodynamic setting. © 2020, Springer Nature Switzerland AG.

Tertiarius minutulus sp. Nov. (Stephanodiscaceae, Bacillariophyta) – A new fossil diatom species from lake ohrid - Zaova, Dušica; Cvetkoska, Aleksandra; Mitic-Kopanja, Danijela; Jovanovska, Elena; Ognjanova-Rumenova, Nadja; Levkov, Zlatko (European Journal of Taxonomy, 2020)

Testing lake-level reconstructions based on rock magnetic proxies for the sediment record of Laguna Ch'altel (Patagonia, Argentina) - Irurzun, Mari'a A.; Palermo, Pedro; Gogorza, Claudia S. G.; Sinito, Ana M.; Aldana, Milagrosa; Costanzo-'Alvarez, Vincenzo; Ohlendorf, Christian; Zolitschka, Bernd (Quaternary Research (United States), 2020)

The Bushveld Complex Drilling Project: an ICDP project on the origins, emplacement and consequences of the world's largest known igneous intrusion - Webb, Susan Jane; Trumbull, Robert Bruce; Ashwal, Lewis D; Roelofse, Frederick; Khoza, David; Hayes, Ben (AGU Fall Meeting Abstracts, 2020)

The challenge of the enigmatic tricolporate tropical pollen type: A case study from Sulawesi, Indonesia - Hamilton, R.; Stevenson, J. (Review of Palaeobotany and Palynology, 2020)
Any palynologist who has worked in the tropics has undoubtedly dealt with the frustration of trying to classify small, tricolporate pollen into meaningful taxonomic groups. While this is not a significant issue where coarse-scale identifications represent similar habitat indicators or “unknown” types are rare, it poses a problem when one of these “unknowns” overwhelm the record. This is the case with unknown “type 69” – a small, tricolporate pollen grain encountered within a 60,000-year sediment sequence from Lake Towuti in Sulawesi, Indonesia. This type comprises up to 35% of the pollen count for some Last Glacial Maximum (LGM) samples (highlighting its climatic sensitivity) but could not be identified by experts in the field. This study thus aimed to compare the metrics of “type 69” with reference pollen from Sulawesi to aid with its identification. In doing so, we present a pollen atlas of 63 maritime southeast Asian pollen types. Our results show that “type 69” aligns with metrics taken from Saurauia pollen. While detailed ecological data on Saurauia species in Sulawesi are lacking, they appear to favor higher elevations and riverbank settings, and are post-disturbance colonizers. Proliferation of this pollen type during the LGM is therefore linked to a combination of downslope range expansion of Saurauia species under a cooler climate and potentially, out competition of upland everwet forest taxa. This study demonstrates an approach to managing important unknown fossil pollen types in tropical records and, through the ensuing pollen atlas, provides a tool for progressing palynology in southeast Asia. © 2019 Elsevier B.V.
Keywords: Greater Sunda Islands; Indonesia; Lake Towuti; Malili Lakes; South Sulawesi; Sulawesi; Sunda Isles; Saurauia; colonization; fossil record; Last Glacial Maximum; palynology; range expansion; river bank; sedimentary sequence

The Cretaceous stratigraphy, Songliao Basin, Northeast China: Constrains from drillings and geophysics - Xu, Zhihe; Xu, Qinglin; Liu, Aitao; Wang, Naichen; Li, Guangxiang; Peng, Chong; Yan, Leilei; Su, Yongfei (Open Geosciences, 2020)
The Cretaceous nonmarine sedimentary strata are widespread in Songliao Basin, Northeast China. As the largest oil producer in China, an abundance of data has been generated by the petroleum industry, including sedimentology, seismology, geochemistry, and geochronology in the Songliao Basin. This article reviews the achievements in China Cretaceous Continental Scientific Drilling SK and presents the new results of the China Continental Geothermal Drilling SR1 in stratigraphy and geophysics. The results allow us to establish the relationships among SK-1, SK-2, and SR1, provide some constrains on the tectonic setting of Songliao Basin, and interpret the sedimentary facies and environmental evolution. After stratigraphic correlation of SK and SR boreholes, the result indicates that the geological boundary between the late Cretaceous Mingshui formation and the Paleogene Yi'an formation is at the depth of 115 m. The magnetotelluric sounding anomaly areas are corresponding with the unconformities, which are equivalent to seismic horizon T03, T1, T2, and T3, respectively. In addition, the typical steer's-headgeometry in the magnetotellurics indicates that the SLB has experienced five evolution stages. © 2020 Zhihe Xu et al., published by De Gruyter 2020.
Keywords: China; Songliao Basin; Geochronology; Infill drilling; Magnetotellurics; Petroleum industry; Sedimentology; Seismology; Stratigraphy; Continental scientific drillings; Environmental evolution; Geological boundaries; Geothermal drilling; Magnetotelluric soundings; Sedimentary facies; Sedimentary strata; Stratigraphic correlation; borehole geophysics; Cretaceous; drilling; geometry; magnetotelluric method; stratigraphic correlation; tectonic setting; Petroleum geology

Measurement of volume change and mass transfer during serpentinization: Insights from the Oman Drilling Project - Malvoisin, Benjamin; Zhang, Chang; M{untener, Othmar; Baumgartner, Lukas P; Kelemen, Peter B; Party, Oman Drilling Project Science (Journal of Geophysical Research: Solid Earth, 2020)

3D microscopic CT imaging and significance of SK-2 deep mudstone of Shahezi Group; [松科二井深层沙河子组泥岩三维显微CT成像及对深部油气预测的启示] - Yang, Jin; Hou, Hesheng; Fu, Wei; Guo, Rui; Pan, Zongdong; Zhang, Jiaodong; Zhang, Huitao (Geological Bulletin of China, 2020)
In order to deepen the understanding of the vertical change rule of the deep shale gas in the Songke 2 Well, the authors selected the 3500 5700 m section of the Shahezi Formation to carry out the X-ray 3D Computed Tomography (CT) imaging experiment. X-ray CT scan was performed on 19 pieces of 2 cm-diameter columnar cores to obtain non-destructive core scan data, and a three-dimensional image spatial structure with a core resolution of up to 15 μm was established. The pore morphology structure and space of the reconstructed core pore model were analyzed by comparative study of spatial distribution and coordination number, statistics of the vertical distribution of sample porosity and connectivity. This experiment proves that the digital core data have high resolution and rich information. The gray value information reflects different components in the sample. The skeleton and minerals are high gray values, and the pores and cracks are low gray values. Studies have shown that areas with large equivalent pore diameters have high porosity, and areas with large coordination numbers have good connectivity. The vertical distribution of porosity and connectivity is consistent with traditional knowledge and can be verified with logging information. It is believed that the digital core can be used as an important auxiliary method for deep core research in the future. © 2020, Science Press. All right reserved.
Keywords: mudstone; paleoenvironment; porosity; rock mechanics; shale gas; source rock; three-dimensional modeling

Magmatic Processes at the Oman Ophiolite Paleoridge – Perspectives on the Role of Water - Koepke, J.; Feig, S.T. (Acta Geologica Sinica (English Edition), 2020)
The Oman ophiolite is regarded as best proxy for accreted oceanic crust from typical fast-spreading ridge systems on land. However, the Oman ophiolite is influenced by initial subduction zone initiation, and the nature of the details of the subduction zone setting is still under controversial debate. While a first magmatic phase shows features of magmatic accretion very similar to those known from the East Pacific Rise, except that the primary melts were slightly water-enriched, a second type of magmatism is characterized by an apparent subduction-zone related imprint, producing rocks like FAB basalts and boninites in the upper crust, as well as cross-cutting gabbronorites and wehrlites in the deeper crust. In this paper, we apply diverse experimental studies in wet tholeiitic and peridotitic systems performed at lower pressures (100 to 500 MPa) in the experimental lab of the University Hannover, in order to constrain the details of the magmatic processes proceeded at the Oman ophiolite paleoridge during the Cretaceous, with special focus on the influence of water on the phase stabilities and phase relations. The experiments were performed in vertically oriented internally heated pressure vessels (IHPV) (see Berndt et al., 2002; Fig. 1). This facility uses as pressure medium mixtures of Ar and H2 in order to adjust the required fH2 in the vessel, enabling us to control the redox conditions. The fH2 prevailing in the IHPV at high P and T was measured with a Shaw-membrane made of platinum. The overall variation in fO2 in all experimental series was in the range between ∼FMQ-1 and ∼FMQ+3.2, thus covering the range of oxygen fugacities prevailing in natural MORB magmas (Bezos and Humler, 2005). For understanding the magmatic processes during the Oman ophiolite paleoridge accretion, transects through the lower (GT1) and middle (GT2) crust have been drilled in the frame of ICDP (International Continental Scientific Drilling Program). Drill sites have been selected in the Wadi Tayin massif, which is known that the influence of magmatic phase 2 characterized by subduction-related primary melts is minimal. Details and progress obtained in the Oman Drilling Project (OmanDP) can be found here: (https://www.omandrilling.ac.uk/). Regarding the first magmatic phase of the processes at the Oman ophiolite paleoridge, a characteristic observation made during the description of the drilled cores GT1 (lower crust) and GT2 (mid-curst) was that quite often layers in the layered gabbro series occur which show the presence of clinopyroxene joining olivine instead of plagioclase (under near liquidus conditions). In terms of lithologies this could be interpreted as presence of wehrlitic crystal mushes as early cumulates instead of troctolitic, which are the typical ones for primary magmatism at typical fast-spreading ridges. This situation could be experimentally simulated by adding a moderate to high water activity to primitive MORB at pressures ≥ 200 MPa, resulting in a shift of the clinopyroxene-in curve to higher temperatures above the plagioclase-in curve (Feig et al. 2006; see Fig. 2). Regarding the second, late-stage magmatic phase, the formation of typical Oman high-Ca-boninites could be experimentally simulated by water-saturated partial melting of Oman harzburgite at 200 MPa and relatively low temperatures between 1100 and 1200°C. Depleted gabbronorites crosscutting layered gabbros of phase 1 magmatism can be regarded as cumulates formed in these boninitic melts. Late wehrlites crosscutting layered gabbro could be produced by accumulation of olivine and clinopyroxene at temperatures between 1040 and 1080°C in a hydrous gabbroic system at pressures > 100 MPa with bulk water content of 2 –3 wt%. © 2020 Geological Society of China
cited By 0
Keywords: accretion; clinopyroxene; gabbro; geoaccumulation; harzburgite; magmatism; mid-ocean ridge basalt; olivine; ophiolite; partial melting; plagioclase; subduction zone; water content; Arabian Sea; East Pacific Rise; Germany; Gulf of Oman; Hannover; Indian Ocean; Lower Saxony; Pacific Ocean

Characterizing subseismic faults from SK-2 drilling core (2900-4200 m): Implication for reservoir transmissibility and regional tectonic evolution - Liang, Shujun; Gan, Wei; Wang, Chengshan (Interpretation, 2020)
Undiscernible faults on seismic reflection profiles are referred to as subseismic faults. Although most subseismic faults are undetected, they play a significant role in understanding regional tectonic evolution and can influence the flow of oil and gas. The Songliao Basin in NE China is a typical Meso-Cenozoic continental petroliferous basin characterized by stable sedimentation, rift-depression dual structure, and large-scale oil and gas production. However, the characteristics of subseismic faults and their effect on petroleum resources remain not well understood. Here we reported findings from the SK-2 east borehole located in the Songliao Basin, which is the deepest (7018 m deep below ground surface) continental scientific drilling borehole in East Asia. We identified 46 subseismic faults at 2900-4200 m depth based on observations of core- scanning images, macro- and micro-structures, and well-logging data. Macro- and micro-structural analyses indicate that most of the subseismic faults in the borehole show normal slip. These observations suggest these subseismic faults may form in response to regional extension in the Shahezi (K1sh) period. The cross-cutting relationships among several groups of sheared fault planes or elongated veins filled in the fractures likely reflect multi-stage faulting. The subseismic faults are considered to be related to the nearby larger-scale faulting as interpreted on the seismic profile. Spatial correlation between the observed subseismic faults and elevated hydrocarbon concentrations documented by borehole mud gas logging suggests that the subseismic faults might have controlled gas migration in the study area. © 2020 Society of Exploration Geophysicists and American Association of Petroleum Geologists.
Keywords: China; Songliao Basin; borehole; fault zone; gas flow; gas well; hydrocarbon migration; hydrocarbon resource; oil well; petroleum hydrocarbon; reservoir characterization; seismic reflection; tectonic evolution; tectonic setting; well logging

Astronomically forced variations in multiresolution resistivity logs of lower Upper Cretaceous (Cenomanian-Coniacian) terrestrial formations from the Songliao Basin, northeastern China - Peng, C.; Zou, C.; Zhang, S.; Wu, H.; L{u, Q.; Hou, H.; Wang, C. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2020)
Continuous and high-resolution well logs from the SK-2 east (SK-2e) borehole in the Songliao Basin provide an opportunity to understand the relationship between astronomically forced climate and electrical responses in terrestrial Cretaceous strata. Here, we present well logs, mud logs, and core measurement data of lacustrine deposits in the Upper Cretaceous Qingshankou Fm and of fluvial/deltaic deposits in the Quantou Fm. The multiresolution resistivity logs used for the cyclostratigraphic analysis include deep laterolog resistivity logs, resistivity image logs, and array induction logs. The results show that the resistivity of strata in Quantou Fm mainly reflects changes in clay content, and that resistivity logs can be used as paleoenvironmental and paleoclimate proxies in cyclostratigraphic studies of the Quantou Fm. For the Qingshankou Fm, formation resistivity is mainly affected by clay minerals, which contribute to the overall electrical conductivity, as well as nonconductive organic carbon. Increasing clay and organic carbon contents usually correspond to wetter and warmer climatic conditions. The phase relationship between resistivity logs and astronomical cyclicity depends on factors that control resistivity. Spectral analyses of lithological changes and resistivity logs indicate the presence of eccentricity, obliquity, and precession cycles throughout the Quantou Fm. This provides strong evidence that climate was the dominant control on cyclic sedimentation in the Quantou Fm. The floating astronomical timescale, which was established by calibrating extracted 405-kyr cycles from resistivity logs, reveals that the duration of Quantou Fm was approximately 5.5 Myr. Comparative analysis of power spectra reveals that the sensitivity of resistivity logs with specific resolutions to Milankovitch cycles with different frequencies is variable. Comprehensive analysis of multiresolution resistivity logs is a new method in cyclostratigraphy analysis that has the potential to be effective in detecting signals of Milankovitch cycles in terrestrial deposits. © 2020 Elsevier B.V.
cited By 7
Keywords: borehole; Cretaceous; cyclic sedimentation; cyclostratigraphy; organic carbon; paleoclimate; China; Songliao Basin

Between plate and salt tectonics–New stratigraphic constraints on the architecture and timing of the Dead Sea basin during the Late Quaternary - Coianiz, L.; Schattner, U.; Lang, G.; Ben-Avraham, Z.; Lazar, M. (Basin Research, 2020)
The Dead Sea is an extensional basin developing along a transform fault plate boundary. It is also a terminal salt basin. Without knowledge of precise stratigraphy, it is difficult to differentiate between the role of plate and salt tectonics on sedimentary accumulation and deformation patterns. While the environmental conditions responsible for sediment supply are reasonably constrained by previous studies on the lake margins, the current study focuses on deciphering the detailed stratigraphy across the entire northern Dead Sea basin as well as syn and post-depositional processes. The sedimentary architecture of the late Quaternary lacustrine succession was examined by integrating 851 km of seismic reflection data from three surveys with gamma ray and velocity logs and the stratigraphic division from an ICDP borehole cored in 2010. This allowed seismic interpretation to be anchored in time across the entire basin. Key surfaces were mapped based on borehole lithology and a newly constructed synthetic seismogram. Average interval velocities were used to calculate isopach maps and spatial and temporal sedimentation rates. Results show that the Amora Formation was deposited in a pre-existing graben bounded by two N-S trending longitudinal faults. Both faults remained active during deposition of the late Pleistocene Samra and Lisan Formations–the eastern fault continued to bound the basin while the western fault remained blind. On-going plate motion introduced a third longitudinal fault, increasing accommodation space westwards from the onset of deposition of the Samra Formation. During accumulation of these two formations, sedimentation rates were uniform over the lake and similar. High lake levels caused an increase in hydrostatic pressure. This led to salt withdrawal, which flowed to the south and southwest causing increased uplift of the Lisan and En Gedi diapirs and the formation of localized salt rim synclines. This induced local seismicity and slumping, resulting in an increased thickness of the Lisan succession within the lake relative to its margins. Sedimentation rates of the Holocene Ze'elim Fm were 4 –5 times higher than before. The analysis presented here resolves central questions of spatial extent and timing of lithology, deposition rates and their variability across the basin, timing of faulting at and below the lake floor, and timing and extent of salt and plate tectonic phases and their effect on syn and post-depositional processes. Plate tectonics dictated the structure of the basin, while salt tectonics and sediment accumulation were primarily responsible for its fill architecture during the timeframe examined here. © 2019 The Authors. Basin Research © 2019 John Wiley & Sons Ltd, European Association of Geoscientists & Engineers and International Association of Sedimentologists
cited By 2
Keywords: deformation mechanism; neotectonics; plate boundary; plate motion; plate tectonics; Quaternary; salt tectonics; sedimentation rate; seismic reflection; stratigraphy; structural control; structural geology; Dead Sea

Borehole research in New York State can advance utilization of low-enthalpy geothermal energy, management of potential risks, and understanding of deep sedimentary and crystalline geologic systems - Jordan, T.; Fulton, P.; Tester, J.; Bruhn, D.; Asanuma, H.; Harms, U.; Wang, C.; Schmitt, D.; Vardon, P.J.; Hofmann, H.; Pasquini, T.; Smith, J.; et al. (Scientific Drilling, 2020)
In January 2020, a scientific borehole planning workshop sponsored by the International Continental Scientific Drilling Program was convened at Cornell University in the northeastern United States. Cornell is planning to drill test wells to evaluate the potential to use geothermal heat from depths in the range of 2700-4500 m and rock temperatures of about 60 to 120 °C to heat its campus buildings. Cornell encourages the Earth sciences community to envision how these boreholes can also be used to advance high-priority subsurface research questions. Because nearly all scientific boreholes on the continents are targeted to examine iconic situations, there are large gaps in understanding of the average intraplate continental crust. Hence, there is uncommon and widely applicable value to boring and investigating a boring location. The workshop focused on designing projects to investigate the coupled thermal-chemical-hydrological-mechanical workings of continental crust. Connecting the practical and scientific goals of the boreholes are a set of currently unanswered questions that have a common root: the complex relationships among pore pressure, stress, and strain in a heterogeneous and discontinuous rock mass across conditions spanning from natural to human perturbations and short to long timescales. The need for data and subsurface characterization vital for decision-making around the prospective Cornell geothermal system provides opportunities for experimentation, measurement, and sampling that might lead to major advances in the understanding of hydrogeology, intraplate seismicity, and fluid/chemical cycling. Subsurface samples could also enable regional geological studies and geobiology research. Following the workshop, the U.S. Department of Energy awarded funds for a first exploratory borehole, whose proposed design and research plan rely extensively on the ICDP workshop recommendations. © 2020 Copernicus GmbH. All rights reserved.
cited By 1
Keywords: Boring; Decision making; Geothermal fields; Groundwater; Hydrogeology; Infill drilling; Complex relationships; Continental scientific drillings; Discontinuous rock mass; Intraplate seismicity; Mechanical working; Subsurface characterizations; Subsurface research; U.S. Department of Energy; Exploratory boreholes

Brittle deformation of carbonated peridotite–Insights from listvenites of the Samail ophiolite (Oman Drilling Project Hole BT1B) - Menzel, Manuel D; Urai, Janos L; Obeso, Juan Carlos; Kotowski, Alissa; Manning, Craig E; Kelemen, Peter B; Kettermann, Michael; Jesus, Ana P; Harigane, Yumiko; Team, Oman Drilling Project Phase 1 Science (Journal of Geophysical Research: Solid Earth, 2020)

Central uplift collapse in acoustically fluidized granular targets: Insights from analog modeling - D{orfler, M.A.; Kenkmann, T. (Meteoritics and Planetary Science, 2020)
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)
cited By 2

Characterization of shocked quartz grains from Chicxulub peak ring granites and shock pressure estimates - Feignon, J.-G.; Ferrière, L.; Leroux, H.; Koeberl, C. (Meteoritics and Planetary Science, 2020)
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)
cited By 11

Climatic control on magnetic mineralogy during the late MIS 6 - Early MIS 3 in Lake Chalco, central Mexico - Ortega-Guerrero, B.; Avendaño, D.; Caballero, M.; Lozano-Garc'ia, S.; Brown, E.T.; Rodr'iguez, A.; Garc'ia, B.; Barceinas, H.; Soler, A.M.; Albarr'an, A. (Quaternary Science Reviews, 2020)
Sediments from Lake Chalco in central Mexico spanning from ca. 150 to 35 ka ago provide evidence of paleoclimatic variability in the North American tropics associated with the end of Marine Isotopic Stage (MIS) 6, the transition to the last interglacial (MIS 5.5, ca. 130-115 ka ago), and part of the last glacial (MIS 5.4 to early MIS 3, 115 to 35 ka ago). We applied a multiproxy approach based on the analysis of mineral magnetism, diatom assemblages and major elements geochemistry. The reconstructed paleoenvironmental history identify the end of the globally cool MIS 6 as wetter than present, with high lake level, and a subsequent change to drier climates at the onset of the last interglacial (ca. 130 ka). Large amplitude changes in most of the analyzed parameters from ca. 130 to 74 ka are approximately coincident with MIS 5 (130-71 ka). The amplitude of these changes decreases in MIS 4 (71-57 ka) and the early part of MIS 3 (57-35 ka). We proposed that the inferred climatic oscillations follow insolation variations during MIS 6 and part of MIS 5 (150-88 ka). Low summer and spring insolation and lower seasonality inhibited evaporation and favored high lake levels. Conversely, maxima in spring and summer insolation promoted dry conditions and low lake levels. The major wet-cold glacial and dry-warm interglacial relationship found in Lake Titicaca (Bolivia) and Lake Chalco records shows the sensitivity of high altitude tropical sites to climatic variability. © 2020 Elsevier Ltd
cited By 12
Keywords: Glacial geology; Incident solar radiation; Magnetic properties; Magnetism; Minerals; Paleolimnology; Tropics; Climatic oscillations; Climatic variability; Interglacial(s); Magnetic mineralogy; Marine isotopic stages; Multiproxy approach; North America; Pleistocene; Lakes; interglacial; Last Glacial Maximum; Last Interglacial; magnetic property; marine isotope stage; mineralogy; paleoclimate; paleolimnology; Pleistocene; reconstruction; seasonal variation; seasonality; Bolivia; Lake Chalco; Lake Titicaca; Mexico [North America]; Bacillariophyta

Assessment of rock damage using seismic methods: Wave speeds and attenuation from borehole measurements in the Chicxulub Impact structure. - Nixon, C.G.; Kofman, R.; Gulick, S.P.S.; Christeson, G.L.; Saustrup, S.; Lofi, J.; Morgan, J.V. (54th U.S. Rock Mechanics/Geomechanics Symposium, 2020)
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
cited By 0

Composition, Stratigraphy, and Geological History of the Noachian Basement Surrounding the Isidis Impact Basin - Scheller, E.L.; Ehlmann, B.L. (Journal of Geophysical Research: Planets, 2020)
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.
cited By 16

Control of planar fabrics on the development of tensile damage zones under high-speed deformation: An experimental study with granite and gneiss - Jacob, B.J.; Misra, S.; Parameswaran, V.; Mandal, N. (Journal of Structural Geology, 2020)
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
cited By 1

Cooling rates of pyroclastic deposits inferred from mineral magnetic investigations: a case study from the Pleistocene M'ytina Maar (Czech Republic) - Lied, Philipp; Kontny, Agnes; Nowaczyk, Norbert; Mrlina, Jan; K{ampf, Horst (International Journal of Earth Sciences, 2020)
Tephra layers of the M'ytina Maar, Czech Republic, contain ferrimagnetic Mg –Al-rich titanomagnetite, which is suggested to originate from a fractionated alkaline CO2-rich lithospheric mantle melt. We investigated the magnetic mineralogy and Curie temperature (TC) from tephra deposits of two drill cores (< 9 m depth). TC calculated (208 ± 14 °C) from chemical composition (Fe2+0.8Mg0.5Fe3+1.1Al0.3Ti0.3O4) is in accordance with TC retrieved from cooling curves of temperature-dependent magnetic susceptibility measurements (195 –232 °C). However, thermomagnetic curves are irreversible either with lower (type I) or higher (type II) TC in the heating curve. All curves show transition temperatures above ca. 390 °C, indicating maghemitization. We interpret the irreversibility of TC (∆TC) in terms of different degrees of cation ordering, overprinted or masked by different degrees of maghemitization, which is a low-temperature phenomenon. Negative ∆TC indicates that original deposited titanomagnetite has cooled faster and, therefore, has stored a lower degree of cation ordering compared to heating/cooling rate of 11 °C/min in the Kappabridge. Type II with positive ∆TC indicates higher degree of cation ordering, and, therefore, slower cooling rate. The central part of this deposit shows most severe maghemitization, indicating rather wet emplacement. We, therefore, suggest different eruption styles for deposition of type I pyroclastics with more phreatomagmatic and type II pyroclastics with more phreato-Strombolian eruption styles. Our study is a new approach to discriminate different cooling histories in maar deposits using the Curie temperature of titanomagnetite. We suggest that this method has the potential to discriminate different emplacement modes resulting from different eruption styles. © 2020, The Author(s).
Keywords: Czech Republic; cooling; emplacement; mineral alteration; Pleistocene; pyroclastic deposit; tephra; volcanic eruption

Correlation of core and downhole seismic velocities in high-pressure metamorphic rocks: a case study for the COSC-1 borehole, Sweden - K{astner, Felix; Pierdominici, Simona; Elger, Judith; Zappone, Alba; K{uck, Jochem; Berndt, Christian (Solid Earth, 2020)
Abstract. Deeply rooted thrust zones are key features of tectonic processes and the evolution of mountain belts. Exhumed and deeply eroded orogens like the Scandinavian Caledonides allow us to study such systems from the surface. Previous seismic investigations of the Seve Nappe Complex have shown indications of a strong but discontinuous reflectivity of this thrust zone, which is only poorly understood. The correlation of seismic properties measured on borehole cores with surface seismic data can constrain the origin of this reflectivity. To this end, we compare seismic velocities measured on cores to in situ velocities measured in the borehole. For some intervals of the COSC-1 borehole, the core and downhole velocities deviate by up to 2 km s^−1. These differences in the core and downhole velocities are most likely the result of microcracks mainly due to depressurization. However, the core and downhole velocities of the intervals with mafic rocks are generally in close agreement. Seismic anisotropy measured in laboratory samples increases from about 5 % to 26 % at depth, correlating with a transition from gneissic to schistose foliation. Thus, metamorphic foliation has a clear expression in seismic anisotropy. These results will aid in the evaluation of core-derived seismic properties of high-grade metamorphic rocks at the COSC-1 borehole and elsewhere.
Publisher: Copernicus GmbH

Crystalline Disposal R &D at LBNL: FY20 Progress Report - Guglielmi, Yves; Chang, Chun; Cook, Paul; Dobson, Patrick; Soom, Florian; Nakagawa, Seiji; Niemi, Auli; Juhlin, Chris; Lorenz, Henning; Rosberg, Jan-Erik; Dessirier, Benoît; Tsang, Chinfu; et al. (Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States), 2020)
Within the Spent Fuel & Waste Science and Technology (SFWST) Program, research work continues further with the goal to better understand long-term performance of disposal systems in three main geologic rock types: clay/shale, salt, and crystalline rock. This report documents LBNL’s research activities related to investigations of crystalline host rock according to the scope of two work packages: SF-20LB01030207 “Crystalline International Collaborations – LBNL,” and SF-20LB01030203 “Crystalline Disposal R &D – LBNL.” These research activities correspond are related to key Features, Events, and Processes (FEPs), ranked in importance from medium to high, as listed in Table 7 of the Used Fuel Disposition Campaign Disposal Research and Development Roadmap (FCR &D-USED-2011-000065 REV0) (Nutt, 2011). Specifically, these research activities address FEP 2.2.01, Excavation Disturbed Zone (EZD). The results of these research activities provide important insights into understanding and predicting flow and transport processes that could occur in low-permeability crystalline rocks, in which fractures might serve as main conduits for fluid flow and radionuclide transport. The evolution of the EDZ during the excavation of the tunnel as well as the evolution of microcrack growth within the EDZ after the emplacement of backfill are critical for predicting the long- term behavior of the EDZ. A number of factors including stress, temperature, water activity, capillary pressure, chemistry, and mineralogy can affect the rock evolution, which require advanced experimental tools to study it.

Deep drilling reveals massive shifts in evolutionary dynamics after formation of ancient ecosystem - Wilke, Thomas; Hauffe, Torsten; Jovanovska, Elena; Cvetkoska, Aleksandra; Donders, Timme; Ekschmitt, Klemens; Francke, Alexander; Lacey, Jack H.; Levkov, Zlatko; Marshall, Charles R.; Neubauer, Thomas A.; Silvestro, Daniele; et al. (Science Advances, 2020)
The scarcity of high-resolution empirical data directly tracking diversity over time limits our understanding of speciation and extinction dynamics and the drivers of rate changes. Here, we analyze a continuous species-level fossil record of endemic diatoms from ancient Lake Ohrid, along with environmental and climate indicator time series since lake formation 1.36 million years (Ma) ago. We show that speciation and extinction rates nearly simultaneously decreased in the environmentally dynamic phase after ecosystem formation and stabilized after deep-water conditions established in Lake Ohrid. As the lake deepens, we also see a switch in the macroevolutionary trade-off, resulting in a transition from a volatile assemblage of short-lived endemic species to a stable community of long-lived species. Our results emphasize the importance of the interplay between environmental/climate change, ecosystem stability, and environmental limits to diversity for diversification processes. The study also provides a new understanding of evolutionary dynamics in long-lived ecosystems. © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).
Keywords: Biodiversity; Biological Evolution; Climate Change; Ecosystem; Fossils; Lakes; Dynamics; Economic and social effects; Lakes; Climate indicators; Ecosystem stability; Empirical data; Endemic species; Evolutionary dynamics; Extinction rates; High resolution; Lake formation; biodiversity; climate change; ecosystem; evolution; fossil; lake; Ecosystems

Deep Scientific Drilling - Harms, U.; Tobin, H. (Encyclopedia of Earth Sciences Series, 2020)
cited By 0

Assessment of the controls on (234U/238U) activity ratios recorded in detrital lacustrine sediments - Francke, Alexander; Dosseto, Anthony; Just, Janna; Wagner, Bernd; Jones, Brian G. (Chemical Geology, 2020)

Artificial Water Reservoir-Triggered Earthquakes, with Special Emphasis on Koyna, India - Gupta, H. (Encyclopedia of Earth Sciences Series, 2020)
cited By 0

Distribution and transport of thermal energy within magma –hydrothermal systems - Eichelberger, John (Geosciences (Switzerland), 2020)

A modified Herschel –Bulkley model for rheological properties with temperature response characteristics of poly-sulfonated drilling fluid - Huang, Y.; Zheng, W.; Zhang, D.; Xi, Y. (Energy Sources, Part A: Recovery, Utilization and Environmental Effects, 2020)
In the deep oil and gas drilling operations, estimation and prediction of the rheological properties for a drilling fluid are of crucial importance for precisely hydraulic calculating, cuttings carrying and wellbore stability controlling. Unfortunately, the existing well-known rheological models, such as Bingham Plastic, Power Law, Casson, and Herschel –Bulkley models neglect the effect of temperature on the apparent viscosity of water-based drilling fluid. In this paper, the rheological behavior of the poly-sulfonated drilling fluid applied to the Well SK-2 in Songliao basin, China, within a temperature range of 60 –240°C, were experimentally determined using a FANN 50SL rheometer. Results showed that the apparent viscosity decreases with the increase of temperature, especially at the low shear rates. In the whole shear rate range, the rheology curve was divided into two parts. At low shear rates ( <170.3 s−1), the Herschel Bulkley model fitted well with the measured data, while at higher shear rates ( >170.3 s−1), the Bingham Plastic model got higher precision. Based on the viscosity equation recommended by the American Petroleum Institute, the temperature factor was introduced to modify the Herschel-Bulkley equation, and the apparent viscosity can be successfully predicted compared with the other commonly used rheological models. © 2019, © 2019 Taylor & Francis Group, LLC.
cited By 15
Keywords: Drilling fluids; Infill drilling; Oil wells; Rheology; Viscosity; American Petroleum Institute; Estimation and predictions; Herschel-Bulkley equations; High temperature; Modifying factors; Prediction model; Rheological property; Water based drilling fluids; Shear deformation

Microbial life in the nascent Chicxulub crater - Schaefer, Bettina; Grice, Kliti; Coolen, Marco J.L.; Summons, Roger E.; Cui, Xingqian; Bauersachs, Thorsten; Schwark, Lorenz; B{ottcher, Michael E.; Bralower, Timothy J.; Lyons, Shelby L.; Freeman, Katherine H.; Cockell, Charles S.; et al. (Geology, 2020)
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.

Lithofacies from the 1963-1967 Surtsey eruption in SUSTAIN drill cores SE-2a, SE-2b and SE-03 - McPhie, Jocelyn; White, James D. L.; Gorny, Carolyn F.; Jackson, Marie D.; Gudmundsson, Magn'us Tumi; COUPER, SAMANTHA (2020)

A 45 kyr laminae record from the Dead Sea: Implications for basin erosion and floods recurrence - Lu, Y.; Bookman, R.; Waldmann, N.; Marco, S. (Quaternary Science Reviews, 2020)
Recording and analyzing how climate change impacts flood recurrence, basin erosion, and sedimentation can improve our understanding of these systems. The aragonite-detritus laminae couplets comprising the lacustrine formations that were deposited in the Dead Sea are considered as faithful monitors of the freshwater supply to the lakes. We count a total of ∼5600 laminae couplets deposited in the last 45 kyr (MIS3-MIS1) at the Dead Sea center, which encompass the upper 142 m of the ICDP Core 5017-1. The present study shows that aragonite and detritus laminae are thinner and occur at high frequency during MIS 3-2, while they are much thicker and less frequent during MIS 1. By analyzing multiple climate-connected factors, we propose that significant lake-level drops, enhanced dust input, and low vegetative cover in the drainage basin during the last deglaciation (22-11.6 ka) have considerably increased erodible materials in the Dead Sea watershed. We find a decoupling existed between the significant lake-level drop/lake size reduction and lamina thickness change during the last deglaciation. We argue that during the Last Glacial and the Holocene, the variation of lamina thickness at the multiple-millennium scale was not controlled directly by the lake-level/size change. We interpret this decoupling implying the transport capacity of flash-floods is low and might be saturated by the oversupply of erodible materials, and indicating a transport-limited regime during the time period. We suggest the observed thickness and frequency distribution of aragonite-detritus laminae points to the high frequency of small-magnitude floods during the Last Glacial, in contrast to low frequency, but large-magnitude floods during the Holocene. © 2019 Elsevier Ltd
cited By 13
Keywords: Carbonate minerals; Catchments; Drops; Erosion; Floods; Glacial geology; Lakes; Paleolimnology; Seawater; Aragonite-detritus laminae; Dead sea; Flash flood; Magnitude-frequency; Transport-limited regime; Climate change; basin analysis; climate change; climate effect; erosion; flash flood; flood; flood frequency; historical record; Holocene; Last Glacial; magnitude; marine isotope stage; paleolimnology; sedimentation; Dead Sea

A contribution towards the palynostratigraphical classification of the Middle Pleistocene in Central Europe: The pollen record of the Neualbenreuth Maar, northeastern Bavaria (Germany) - Stebich, Martina; H{ofer, Dana; Mingram, Jens; Nowaczyk, Norbert; Rohrm{uller, Johann; Mrlina, Jan; K{ampf, Horst (Quaternary Science Reviews, 2020)
Palaeoecological evidence of intra-Saalian warm stages in Central Europe, which was strongly affected by glacial and periglacial processes during the major Middle and Late Pleistocene cold periods, is ambiguous so far. Recently, the first continuous sedimentary sequence of Central Europe containing the Saalian complex (MIS 8 –6) with the Eemian interglacial in stratigraphic superposition was recovered from the newly discovered Neualbenreuth Maar (NE-Bavaria). Here we present palynological results from this record allowing us to critically discuss the available biostratigraphical evidence of alternating intra-Saalian warm-cold intervals from Central Europe. The new pollen record from the Neualbenreuth Maar comprises a continuous record of vegetation and climate changes encompassing four warm stages and five cold periods. The dominance of cold and dry tolerant herbs and the sparse representation of pioneer trees and shrubs during most parts of the sequence indicate open landscapes of steppe to woody-steppe character typical of late Middle and Late Pleistocene glacial periods in Central Europe. The pollen assemblages of the warm stage in the upper part of the core clearly support its correlation with the Eemian interglacial. The three pre-Eemian warm stages represent terrestrial analogues of the marine isotope stages (MIS) 7e, 7c, and 7a. During each of these intervals forests were established, but the reduced abundances and lower diversity of thermophilous and sub-oceanic elements in comparison to the Eemian attest to a weak interglacial character. Each of these interglacials shows a similar vegetation succession and only minor differences in the vegetation composition. The intervening stadial periods represent a strong (MIS 7d) and a moderate (MIS 7b) climate deterioration, respectively. The vegetation and climate succession during the Saalian glacial-interglacial complex of Neualbenreuth is broadly in line with the respective palynological signature from the Velay record (French Massif Central) and the Hoogeveen interstadial (The Netherlands). In contrast, there is only limited correspondence with most pollen records from northern and southern Central Europe, which were hitherto classified as MIS 7. © 2020 Elsevier Ltd
Keywords: Europe; Climate change; Deterioration; Stratigraphy; Vegetation; Climate deterioration; Marine isotope stages; Middle Pleistocene; Periglacial process; Sedimentary sequence; Sparse representation; Vegetation composition; Vegetation successions; allostratigraphy; Eemian; interglacial; interstadial; paleoecology; palynology; Pleistocene; Pliocene-Pleistocene boundary; Saalian; stratigraphy; Glacial geology

A discussion on the organic matter enrichment model of the Nenjiang Formation, Songliao Basin: A case study of oil shale in the 1st and 2nd members of the Nenjiang Formation; [松辽盆地嫩江组泥页岩有机质富集模式探讨––以嫩江组一、二段油页岩为例] - Shang, Fei; Zhou, Haiyan; Liu, Yong; Zhou, Xuexian; Wang, Lan; Bi, He; Wang, Guochang; Song, Li; Chen, Ruiqian (Geology in China, 2020)
The formation mechanism of the oil shale developed in the 1st and 2nd members of Nenjiang Formation in Songliao Basin was studied by combining theoretical model with geological data such as total carbon content, sulfur isotope of pyrite, and whole rock element from the Songke-1 Well (south hole). Some conclusions have been reached: (1) It may not be fully correct to attribute the formation of oil shale to seawater intrusion into the lake basin. Although seawater invasion can lead to salinization of the lake and subsequent algae blooming, the change of bottom water redox condition caused by the invasion of oxygen-rich seawater into the bottom lake can inhibit the accumulation and preservation of organic matter in sediments; (2) The impact of seawater transgression on oil shale formation was mainly related to algae blooming caused by the continuous salinization of the lake water after transgression; (3) Volcanic tuff deposits are widely distributed in the Songliao basin and usually associated with oil shale deposits. The increase of productivity in ancient Songliao lake basin was directly related to nutrients such as phosphorus and iron brought by volcanic ash input; (4) The formation of oil shale in the Nenjiang Formation was controlled by a combination of mechanisms such as water eutrophication events induced by instantaneous mass input of volcanic ash and seawater invasion. It is concluded that organic matter enrichment in the oil shale is controlled by both water depth and the influence of sediment input from rivers. © 2020 Editorial Board of Geology in China. All rights reserved.
Keywords: China; Songliao Basin; enrichment; eutrophication; hydrocarbon exploration; model; oil shale; organic matter; volcanic ash

A Floating Astronomical Time Scale for the Early Late Cretaceous Continental Strata in the Songliao Basin, Northeastern China - Xiaojuan, M.A.; Huaichun, W.U.; Fang, Q.; Shi, M.; Zhang, S.; Yang, T.; Haiyan, L.I.; Wang, C. (Acta Geologica Sinica (English Edition), 2020)
A continuous terrestrial succession was recovered from the Songke-2 (SK-2) borehole in the Songliao Basin, Northeastern China. This borehole provides a unique material for further research on the continental paleoclimate during Cretaceous greenhouse period, following a series of achievements of the Songke-1 (SK-1) core. In this study, thorium (Th) logging data were chosen as a paleoclimate proxy to conduct a detailed cyclostratigraphic analysis. The Th series varies quasi-periodically; power spectra and evolutionary fast Fourier transformation (FFT) analysis reveal significant cycles in the Quantou (K2q), Qingshankou (K2qn), Yaojia (Ky and Nenjiang (K2n) formations. The ratio of cycle wavelengths in these stratigraphic units is approximately 20:5:2:1, corresponding to long orbital eccentricity (405 kyr), short orbital eccentricity (100 kyr), obliquity (37 kyr), and precession cycles (22.5 kyr and 18.4 kyr). The durations of the K2n, K2y, K2qn and K2q are estimated as 6.97, 1.83, 5.30 and 4.52 Myr, respectively, based on the constructed ∼18.62 Myr “floating” astronomical time scale (ATS). Comparison of the durations between the SK-1 s and SK-2 boreholes exhibits a slight difference of 0.06 Myr and 0.459 Myr for K2qn and K2y. Nevertheless, our ATS of K2n supports the chronostratigraphic frame constructed by the CA-ID-TIMS data of the SK-1s borehole. This new “floating” ATS provides precise numerical ages for stratigraphic boundaries, biozones and geological events in the Songliao Basin, and can serve as a basis for correlation of strata and events between marine and terrestrial systems. © 2020 Geological Society of China
cited By 3
Keywords: borehole; Cretaceous; detection method; eccentricity; marine environment; paleoclimate; proxy climate record; terrestrial environment; thorium; China; Songliao Basin

A steeply-inclined trajectory for the Chicxulub impact - Collins, G.S.; Patel, N.; Davison, T.M.; Rae, A.S.P.; Morgan, J.V.; Gulick, S.P.S.; Christeson, G.L.; Chenot, E.; Claeys, P.; Cockell, C.S.; Coolen, M.J.L.; Ferrière, L.; et al. (Nature Communications, 2020)
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).
cited By 40

Andean drought and glacial retreat tied to Greenland warming during the last glacial period - Woods, Arielle; Rodbell, Donald T.; Abbott, Mark B.; Hatfield, Robert G.; Chen, Christine Y.; Lehmann, Sophie B.; McGee, David; Weidhaas, Nicholas C.; Tapia, Pedro M.; Valero-Garc'es, Blas L.; Bush, Mark B.; Stoner, Joseph S. (Nature Communications, 2020)
Abrupt warming events recorded in Greenland ice cores known as Dansgaard-Oeschger (DO) interstadials are linked to changes in tropical circulation during the last glacial cycle. Corresponding variations in South American summer monsoon (SASM) strength are documented, most commonly, in isotopic records from speleothems, but less is known about how these changes affected precipitation and Andean glacier mass balance. Here we present a sediment record spanning the last 50 ka from Lake Jun'in (Peru) in the tropical Andes that has sufficient chronologic precision to document abrupt climatic events on a centennial-millennial time scale. DO events involved the near-complete disappearance of glaciers below 4700 masl in the eastern Andean cordillera and major reductions in the level of Peru’s second largest lake. Our results reveal the magnitude of the hydroclimatic disruptions in the highest reaches of the Amazon Basin that were caused by a weakening of the SASM during abrupt arctic warming. Accentuated warming in the Arctic could lead to significant reductions in the precipitation-evaporation balance of the southern tropical Andes with deleterious effects on this densely populated region of South America. © 2020, The Author(s).
Keywords: Amazon Basin; Andes; Arctic; Greenland; Peru; cordillera; Dansgaard-Oeschger cycle; drought stress; glacier retreat; hydrometeorology; Last Glacial; monsoon; precipitation assessment; seasonality; Arctic; article; deglaciation; drought; evaporation; glacial period; Greenland; Peru; precipitation; sediment; summer; warming

A Strainmeter Array Along the Alto Tiberina Fault System, Central Italy - Chiaraluce, Lauro; Bennett, Rick; Mencin, David; Barchi, Massimiliano; Bohnhoff, Marco (EGU General Assembly Conference Abstracts, 2020)

A unified contactcementation theory for gas hydrate morphology detection and saturation estimation from elastic-wave velocities - Pan, H.; Li, H.; Chen, J.; Zhang, Y.; Cai, S.; Huang, Y.; Zheng, Y.; Zhao, Y.; Deng, J. (Marine and Petroleum Geology, 2020)
Good knowledge of hydrate morphology and accurate quantification of hydrate saturation are significant for reservoir characterization, resource exploitation and geohazards assessment. Although many of empirical or theoretical models have been developed to detect hydrate morphology and predict hydrate saturation from elastic-wave velocities, they either fail to hold true for complex morphologies or cannot provide accurate hydrate saturation estimate. In this study, we propose a unified contact cementation theory by applying the modified Hashin-Shtrikman upper and lower bounds to an extended cementation theory. By merging the cementation theory and effective medium theory, it can be used to account for four types of hydrate morphologies. Numerical modeling results provide some new insights into effects of normalized thickness of hydrate layer, friction coefficient and effective pressure on elastic-wave velocities for different morphologies, which will be helpful for analyzing the borehole stability and determining optimum production-related strategies. In addition, we propose a hydrate morphology-based inversion method by introducing the ratio of multiple hydrate morphologies from statistical analyses and apply it to the acoustic logs from the Mallik 5L-38 permafrost-related gas hydrate research well in Mackenzie Delta and other three marine wells in Nankai Trough and Hikurangi margin. The velocity-based gas hydrate saturation estimations are in good agreement with those predicted from resistivity log and Nuclear Magnetic Resonance measurement, as well as core data, confirming feasibility and applicability of our theory and inversion method, and indicating its potential in seismic characterization of gas hydrate reservoirs. © 2019 Elsevier Ltd
cited By 12
Keywords: Acoustic logging; Acoustics; Boreholes; Cementing (shafts); Elastic waves; Electric logging; Friction; Gases; Hydration; Morphology; Nuclear magnetic logging; Velocity; Accurate quantifications; Effective medium theories; Elastic wave velocity; Gas hydrate saturations; Hikurangi margin; Hydrate saturation; Reservoir characterization; Unified contact cementation theory; Gas hydrates; detection method; elastic wave; estimation method; gas hydrate; hydrocarbon exploration; hydrocarbon reservoir; morphology; wave velocity

Abrupt climate change and its influences on hominin evolution during the early Pleistocene in the Turkana Basin, Kenya - Lupien, Rachel L.; Russell, James M.; Grove, Matt; Beck, Catherine C.; Feibel, Craig S.; Cohen, Andrew S. (Quaternary Science Reviews, 2020)

Acoustic evidence for a broad, hydraulically active damage zone surrounding the Alpine Fault, New Zealand - Jeppson, Tamara N.; Tobin, Harold (Tectonophysics, 2020)

Alteration progress within the Surtsey hydrothermal system, SW Iceland–A time-lapse petrographic study of cores drilled in 1979 and 2017 - Prause, Simon; Weisenberger, Tobias Bj{orn; Cappelletti, Piergiulio; Grimaldi, Carla; Rispoli, Concetta; J'onasson, Kristj'an; Jackson, Marie D; Gudmundsson, Magn'us Tumi (Journal of Volcanology and Geothermal Research, 2020)

An 11 million-year-long record of astronomically forced fluvial-alluvial deposition and paleoclimate change in the Early Cretaceous Songliao synrift basin, China - Liu, Wei; Wu, Huaichun; Hinnov, Linda A.; Baddouh, M'bark; Wang, Pujun; Gao, Youfeng; Zhang, Shihong; Yang, Tianshui; Li, Haiyan; Wang, Chengshan (Palaeogeography, Palaeoclimatology, Palaeoecology, 2020)

Analysis of bit balling and application of the balling-preventing drilling fluid in well Songke-2; [钻头泥包原因分析及松科二井防泥包钻井液的应用] - Hu, Yule; Hu, Chen; Zhang, Hengchun; Zheng, Wenlong (Meitiandizhi Yu Kantan/Coal Geology and Exploration, 2020)
In order to solve the problem of the high mud content and easy hydration and dispersion of the Cretaceous sedimentary strata in well Songke-2, the bit balling is prone to occur in the water-based drilling fluid environment, which affects the drill bit ROP and induces downhole adhesion stuck, the paper combined the core drilling technology of well Songke-2, systematically analyzed of the causes of bit balling generated by the drill bit in the mudstone and water-based drilling fluid environment, provided a basis for the design of the anti-balling of the drill bit and the formulation of the anti-ball in drilling fluid, and proposed a drilling fluid formulation with excellent anti-balling performance. The results show that the mudstone drilled in well Songke-2 had the characteristics of high shale content and easy hydration and viscosity, it is very easy to induce the bit balling caused by the adhesion of cuttings and the mechanical “inlaying” of cuttings. Mechanical adhesion of drill bit and drill structure size, bottom hole hydraulic condition, bit material and surface condition, drilling procedure parameters and drilling fluid performance indicators are closely related. Adjusting the performance of the drilling fluid is an effective way to solve the bit balling problem at the drilling site. According to the technical characteristics of the high-temperature and high-pressure sections in the fourth opening of the well Songke-2,after repeated matching, the drilling fluid composition with excellent high temperature resistance and anti-adhesion performance was obtained. The test results of high temperature inhibition, water loss wall-building and the lubricity show that this drilling fluid has strong inhibition at high temperature(230℃), little water loss and good lubricity, it can solve the bit balling problem of the well Songke-2, effectively avoid the instability of the ROP and the occurrence of sticking stuck, the field application effect is ideal. © Meitiandizhi Yu Kantan/Coal Geology and Exploration 2020.

Design and applications of drilling trajectory measurement instrumentation in an ultra-deep borehole based on a fiber-optic gyro - Liu, Y.; Wang, C.; Luo, G.; Ji, W. (Geoscientific Instrumentation, Methods and Data Systems, 2020)
The working environment in hot dry rock boreholes, encountered in deep geothermal investigation drilling and ultra-deep geological drilling (up to 5000 m), is very difficult at the present stage. We have developed a drilling trajectory measuring instrumentation (DTMI), which is based on the interference fiber-optic gyro (FOG). This can work continuously, for 4 h, in an environment where the ambient temperature does not exceed 270 °C and the pressure does not exceed 120MPa. The DTMI is mainly divided into three parts: an external confining tube, a metal vacuum flask, and a FOG measurement probe. Here, we focus on the mechanical design, strength, and pressure field simulation analysis for the external tube, the structural design and temperature field simulation analysis for the vacuum flask, and the FOG Shupe error analysis and compensation in the temperature field. Finally, through the engineering applications of the SK-2 east borehole of the China Continental Scientific Drilling (CCSD) project and the geothermal well of Xingreguan-2, the data measurements of the drilling trajectory were used to analyze the stability of the DTMI. The instrument realizes long-duration, high-stability work in the process of making trajectory measurements in an ultra-deep hole. The instrument has the characteristic of anti-electromagnetic interference and enables work to be carried out in the blind zone of existing technologies and instrumentation. Therefore, DTMI has great potential in the promotion and development of geological drilling technology. © Author(s) 2020.
cited By 1
Keywords: Boreholes; Bottles; Electromagnetic pulse; Error compensation; Geology; Geothermal wells; Gyroscopes; Hot working; Infill drilling; Structural design; Temperature; Trajectories; Continental scientific drillings; Data measurements; Design and application; Engineering applications; Geological drilling; Temperature field simulation; Trajectory measurements; Working environment; Fiber optics; borehole geophysics; design method; drilling; fiber optics; geological survey; geothermal system; hot dry rock; instrumentation; measurement method; trajectory; well logging

3-D seismic attenuation structure of Long Valley caldera: Looking for melt bodies in the shallow crust - Prudencio, J.; Manga, M. (Geophysical Journal International, 2020)
Unrest at Long Valley caldera (California) during the past few decades has been attributed to the ascent of hydrothermal fluids or magma recharge. The difference is critical for assessing volcanic hazard. To better constrain subsurface structures in the upper crust and to help distinguish between these two competing hypotheses for the origin of unrest, we model the 3-D seismic attenuation structure because attenuation is particularly sensitive to the presence of melt. We analyse more than 47 000 vertical component waveforms recorded from January 2000 through November 2016 obtained from the Northern California Earthquake Data Center. We then inverted the S-to-coda energy ratios using the coda normalization method and obtained an average Q of 250. Low attenuation anomalies are imaged in the fluid-rich western and eastern areas of the caldera, one of which corresponds to the location of an earthquake swarm that occurred in 2014. From a comparison with other geophysical images (magnetotellurics, seismic tomography) we attribute the high attenuation anomalies to hydrothermal systems. Average to high attenuation values are also observed at Mammoth Mountain (southwest of the caldera), and may also have a hydrothermal origin. A large high attenuation anomaly within the caldera extends from the surface to the depths we can resolve at 9 km. Shallow rocks here are cold and this is where earthquakes occur. Together, these observations imply that the high attenuation region is not imaging a large magma body at shallow depths nor do we image any isolated high attenuation bodies in the upper ≈8 km that would be clear-cut evidence for partially molten bodies such as sills or other magma bodies. © 2019 The Author(s). Published by Oxford University Press on behalf of The Royal Astronomical Society.
cited By 8
Keywords: Landforms; Coda normalization method; Hydrothermal fluids; Hydrothermal system; Long valley caldera; Seismic attenuation; Seismic tomography; Subsurface structures; Vertical component; Earthquakes; caldera; crustal structure; earthquake event; earthquake magnitude; magma; seismic attenuation; seismic data; seismic source; seismicity; seismology; three-dimensional modeling; waveform analysis; California; Long Valley Caldera; United States

Downward remagnetization of a ∼74-m-thick zone in lake sediments from palaeo-Lake Idaho (NW United States) - Locating the Gauss/Matuyama geomagnetic boundary within a dual-polarity zone - Allst{adt, F.J.; Appel, E.; R{osler, W.; Prokopenko, A.A.; Neumann, U.; Wenzel, T.; Pross, J. (Geophysical Journal International, 2020)
Remagnetization is an important issue in palaeomagnetism. Here, we discuss an extraordinarily thick (∼74 m) dual-polarity transition zone between the Gauss and Matuyama Chrons. The studied succession is from a drill core through lacustrine sediments of palaeo-Lake Idaho (Snake River Plain, NW United States of America) that are intercalated with basalt units. We identified detrital Ti-rich titanomagnetite and magnetite in lamellar exsolutions as the main carriers of a primary remanence, likely derived from the basalts that erupted in the Snake River Plain. Stepwise thermal demagnetization revealed a single-component remanent magnetization with reversed and normal polarities above and below the transition zone, respectively. Based on rock-magnetic results, microscopic observations, and previously known events in the evolution of palaeo-Lake Idaho, the reversed-polarity component in the transition zone represents a secondary chemical remanent magnetization caused by magnetic mineral alteration or partial neo-formation of magnetite, in association with strong depletion of the primary detrital magnetic minerals that affected a wide depth range below the level where the remagnetization event occurred. This remagnetization event was most likely related to lake-level lowering and partial desiccation of palaeo-Lake Idaho. Understanding the nature and origin of the remagnetization allows to identify the polarity boundary in the unusual case of a secondary magnetization with reversed polarity produced downward in a sequence to an extraordinary large depth. Based on available age information, the observed reversal represents the Gauss/Matuyama boundary, which provides an important age constraint for palaeoclimatic interpretation of the succession. © 2020 The Author(s) 2020. Published by Oxford University Press on behalf of The Royal Astronomical Society.
cited By 1
Keywords: Basalt; Core drilling; Demagnetization; Gaussian distribution; Geomagnetism; Lakes; Lithology; Magnetite; Magnetization; Minerals; Chemical remanent magnetization; Lacustrine sediments; Microscopic observations; Remanent magnetization; Single components; Snake river plains; Stepwise thermal demagnetization; United States of America; Magnetic polarity; basalt; geomagnetism; lacustrine deposit; magnetic mineral; paleomagnetism; remagnetization; remanent magnetization; titanomagnetite; Idaho; Snake River Plain; United States

Hydrothermal circulation and oil migration at the root of the heterogeneous micro-structure of carbonaceous material in the 2.0 Ga Zaonega Formation, Onega Basin, Russia - Qu, Yuangao; Zuilen, Mark A; Lepland, Aivo (Precambrian Research, 2020)

Groundwater flow characterization of an ophiolitic hard-rock aquifer from cross-borehole multi-level hydraulic experiments - Lods, G'erard; Roubinet, Delphine; Matter, J{urg M; Leprovost, Richard; Gouze, Philippe; Team, Oman Drilling Project Science; et al. (Journal of Hydrology, 2020)

High resolution X–ray computed tomography and scanning electron microscopy studies of multiphase solid inclusions in Oman podiform chromitite: implications for post–entrapment modification - Yao, Yuan; Takazawa, Eiichi; Chatterjee, Sayantani; Richard, Antonin; Morlot, Christophe; Creon, Laura; Al–Busaidi, Salim; Michibayashi, Katsuyoshi; Team, Oman Drilling Project Science; et al. (Journal of Mineralogical and Petrological Sciences, 2020)

High-resolution microstructural and compositional analyses of shock deformed apatite from the peak ring of the Chicxulub impact crater - Cox, M.A.; Erickson, T.M.; Schmieder, M.; Christoffersen, R.; Ross, D.K.; Cavosie, A.J.; Bland, P.A.; Kring, D.A.; Gulick, S.; Morgan, J.V.; Carter, G.; Chenot, E.; et al. (Meteoritics and Planetary Science, 2020)
cited By 12

History of scoria-cone eruptions on the eastern shoulder of the Kenya –Tanzania Rift revealed in the 250-ka sediment record of Lake Chala near Mount Kilimanjaro - Martin-Jones, C.; Lane, C.; Van Daele, M.; Meeren, T.V.D.; Wolff, C.; Moorhouse, H.; Tomlinson, E.; Verschuren, D. (Journal of Quaternary Science, 2020)
Reconstructions of the timing and frequency of past eruptions are important to assess the propensity for future volcanic activity, yet in volcanic areas such as the East African Rift only piecemeal eruption histories exist. Understanding the volcanic history of scoria-cone fields, where eruptions are often infrequent and deposits strongly weathered, is particularly challenging. Here we reconstruct a history of volcanism from scoria cones situated along the eastern shoulders of the Kenya –Tanzania Rift, using a sequence of tephra (volcanic ash) layers preserved in the 250-ka sediment record of Lake Chala near Mount Kilimanjaro. Seven visible and two non-visible (crypto-) tephra layers in the Lake Chala sequence are attributed to activity from the Mt Kilimanjaro (northern Tanzania) and the Chyulu Hills (southern Kenya) volcanic fields, on the basis of their glass chemistry, textural characteristics and known eruption chronology. The Lake Chala record of eruptions from scoria cones in the Chyulu Hills volcanic field confirms geological and historical evidence of its recent activity, and provides first-order age estimates for seven previously unknown eruptions. Long and well-resolved sedimentary records such as that of Lake Chala have significant potential for resolving regional eruption chronologies spanning hundreds of thousands of years. © 2019 The Authors. Journal of Quaternary Science Published by John Wiley & Sons Ltd
cited By 6
Keywords: geochemistry; historical perspective; lacustrine deposit; tephra; tephrochronology; volcanic eruption; volcanic glass; volcanism; East African Rift; East African Rift; Kenya; Kenya Rift; Kilimanjaro [Tanzania]; Lake Challa; Tanzania

Hydrological modelling in desert areas of the eastern Mediterranean - Zoccatelli, D.; Marra, F.; Smith, J.; Goodrich, D.; Unkrich, C.; Rosensaft, M.; Morin, E. (Journal of Hydrology, 2020)

Hydrothermal alteration associated with the Chicxulub impact crater upper peak-ring breccias - Simpson, S.L.; Osinski, G.R.; Longstaffe, F.J.; Schmieder, M.; Kring, D.A. (Earth and Planetary Science Letters, 2020)
The 66 Ma, ∼180 km Chicxulub impact structure in the northern Yucat'an 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.
cited By 16

ICDP workshop on the Lake Tanganyika Scientific Drilling Project: A late Miocene-present record of climate, rifting, and ecosystem evolution from the world's oldest tropical lake - Russell, J.M.; Barker, P.; Cohen, A.; Ivory, S.; Kimirei, I.; Lane, C.; Leng, M.; Maganza, N.; McGlue, M.; Msaky, E.; Noren, A.; Boush, L.P.; et al. (Scientific Drilling, 2020)
The Neogene and Quaternary are characterized by enormous changes in global climate and environments, including global cooling and the establishment of northern high-latitude glaciers. These changes reshaped global ecosystems, including the emergence of tropical dry forests and savannahs that are found in Africa today, which in turn may have influenced the evolution of humans and their ancestors. However, despite decades of research we lack long, continuous, well-resolved records of tropical climate, ecosystem changes, and surface processes necessary to understand their interactions and influences on evolutionary processes. Lake Tanganyika, Africa, contains the most continuous, long continental climate record from the mid-Miocene (∼ 10 Ma) to the present anywhere in the tropics and has long been recognized as a top-priority site for scientific drilling. The lake is surrounded by the Miombo woodlands, part of the largest dry tropical biome on Earth. Lake Tanganyika also harbors incredibly diverse endemic biota and an entirely unexplored deep microbial biosphere, and it provides textbook examples of rift segmentation, fault behavior, and associated surface processes. To evaluate the interdisciplinary scientific opportunities that an ICDP drilling program at Lake Tanganyika could offer, more than 70 scientists representing 12 countries and a variety of scientific disciplines met in Dar es Salaam, Tanzania, in June 2019. The team developed key research objectives in basin evolution, source-to-sink sedimentology, organismal evolution, geomicrobiology, paleoclimatology, paleolimnology, terrestrial paleoecology, paleoanthropology, and geochronology to be addressed through scientific drilling on Lake Tanganyika. They also identified drilling targets and strategies, logistical challenges, and education and capacity building programs to be carried out through the project. Participants concluded that a drilling program at Lake Tanganyika would produce the first continuous Miocene-present record from the tropics, transforming our understanding of global environmental change, the environmental context of human origins in Africa, and providing a detailed window into the dynamics, tempo and mode of biological diversification and adaptive radiations. © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License.
cited By 6
Keywords: Biology; Climate change; Ecosystems; Forestry; Geochronology; Infill drilling; Tropics; Continental climate; Environmental contexts; Evolutionary process; Global environmental change; Research objectives; Scientific discipline; Scientific drilling; Tropical dry forest; Lakes

Geothermal energy and ore-forming potential of 600 °C mid-ocean-ridge hydrothermal fluids - Bali, Enikő; Guðfinnsson, Guðmundur H.; Aradi, L'aszl'o E.; Szab'o, 'Abel; Szab'o, Csaba; Zierenberg, Robert; Diamond, Larryn W.; Pettke, Thomas; Friðleifsson, Guðmundur Ó (Geology, 2020)

Identification of gas inflow zones in the COSC-1 borehole (J{amtland, central Sweden) by drilling mud gas monitoring, downhole geophysical logging and drill core analysis - Pierdominici, Simona; Lorenz, Henning; Almqvist, Bjarne; Klonowska, Iwona (Applied Geochemistry, 2020)
On-line monitoring of drilling mud gas was for the first time applied during continuous wireline coring of the COSC-1 borehole (J{amtland, central Sweden) to analyse formation gases and to identify inflow gas zones. Nearly complete gas records were obtained with 3 m depth resolution from 662 m (installation of the separator for gas extraction) to 1709 m and 6 m resolution from 1709 m to 2490 m depth (COSC-1 final depth: 2496 m) for H2, CH4, CO2, and He. Between 662 m and 1400 m, both He and CH4 form broad peaks superimposed by several spike-like features. Zones with gas spikes coincide with high resistivity intervals from dual laterolog (DLL) geophysical borehole logging and show fractures in borehole televiewer (BHTV) images, drill core scans, and visual core inspection. Therefore, we assume gas inflow through open fractures where DLLd/DLLs ratios >1.5 imply the presence of free gas. The correlation between helium and DLLd/DLLs ratios no longer appears at depths greater than ~1550 m, probably because the formation gases are dissolved in formation fluids at higher pressure. Below 1550 m depth, the He concentration drops significantly, whereas the CH4 concentration remains relatively high and H2 and CO2 reach maximum values. The high amount of H2 and CH4 at depths below 1616 m, from where friction between the casing and the drill string was reported, imply that these gases are most certainly artificially generated at depths below 1616 m and at least partly of artificial origin at shallower depths.
Keywords: COSC; Downhole logging; Drilling mud gas analysis; Formation fluids; Natural fractures

Impact of fluid-rock interaction on water uptake of the Icelandic crust: Implications for the hydration of the oceanic crust and the subducted water flux - Kleine, B.I.; Stef'ansson, A.; Halld'orsson, S.A.; Barnes, J.D. (Earth and Planetary Science Letters, 2020)

In Situ Stress Orientation From 3 km Borehole Image Logs in the Koyna Seismogenic Zone, Western India: Implications for Transitional Faulting Environment - Goswami, D.; Hazarika, P.; Roy, S. (Tectonics, 2020)
Knowledge of the in situ stress regime is critical to investigate the genesis of recurrent triggered seismicity over the past five decades in the Koyna seismogenic zone. Orientations of in situ horizontal stresses are determined for the first time from analyses of image logs in a 3 km deep scientific borehole KFD1 in the area. KFD1 passed through 1,247 m thick Deccan Traps and continued 1,767 m in the granitic basement. Stress-induced wellbore failures, breakouts and drilling-induced tensile fractures, are identified in the acoustic and microresistivity images of the granitic basement. Additionally, tightly constrained focal mechanisms of 50 earthquakes of M ≥ 3.6, reported in literature, are inverted to constrain the stress regime. Salient results are as follows: (i) wellbore breakouts and drilling-induced tensile fractures constrain N9°W ± 17° orientation for maximum horizontal principal stress (SHmax); (ii) consistency with the regional NNW-SSE orientation of SHmax from inversion of earthquake focal mechanisms shows that the borehole data are representative for the Koyna region; (iii) breakout rotations at multiple depths below 2,100 m indicate that the borehole may have passed through localized fault damage zones; (iv) consistent strike azimuths of steeply dipping fractures with SHmax orientation indicate favorable conditions for strike-slip to normal transitional faulting environment; and (v) stress inversion of 50 well-determined earthquake focal mechanisms supports transitional faulting environment in the Koyna seismogenic zone. Thus, stress orientation and fracture information from borehole data, together with stress regime constrained from inversion of earthquake focal mechanisms, shed new light on the faulting environment in the region. ©2020. American Geophysical Union. All Rights Reserved.
cited By 12
Keywords: Boreholes; Buildings; Earthquakes; Fracture; Horizontal wells; Infill drilling; Oil field equipment; Seismographs; Stresses; Strike-slip faults; Well logging; Borehole breakouts; Drilling-induced tensile fractures; Principal stress; Seismogenic zones; Stress orientations; Stress rotation; Fault slips; borehole breakout; borehole logging; Deccan Traps; drilling; faulting; focal mechanism; fracture; in situ stress; induced response; seismicity; India

Insights into the evolution of the young Lake Ohrid ecosystem and vegetation succession from a southern European refugium during the Early Pleistocene - Panagiotopoulos, Konstantinos; Holtvoeth, Jens; Kouli, Katerina; Marinova, Elena; Francke, Alexander; Cvetkoska, Aleksandra; Jovanovska, Elena; Lacey, Jack H.; Lyons, Emma T.; Buckel, Connie; Bertini, Adele; Donders, Timme; et al. (Quaternary Science Reviews, 2020)

Koyna earthquakes: a review of the mechanisms of reservoir-triggered seismicity and slip tendency analysis of subsurface faults - Das, D.; Mallik, J. (Acta Geophysica, 2020)
Koyna region in western India experienced more than 1,00,000 earthquakes of different magnitudes (M 1.0 –6.3) in the past five decades. Earthquakes in this region are believed to be triggered by a change in fluid pressure due to the percolation of the reservoir (Koyna and Warna reservoir) water into the subsurface. A drilling program was set up by the Ministry of Earth Sciences, India and International Continental Scientific Drilling Program (ICDP) to study the deep subsurface lithology, structure, thermal attributes, etc. as the area is covered by 950 m of thick Deccan basalts. This paper reviews all the hypotheses proposed by earlier workers to explain the mechanism of reservoir trigger causing earthquakes and summarizes such theories to a simple generic model. Slip tendency analysis was further carried out based on the proposed model to explain the dependence of fault slip on fault geometry, rock mechanical properties, stress and fluid gradients. Finally, faults at various depths were characterized (favourably oriented, unfavourably oriented and severely misoriented) based on their potential to go into failure. © 2020, Institute of Geophysics, Polish Academy of Sciences & Polish Academy of Sciences.
cited By 5
Keywords: Earthquakes; Infill drilling; Lithology; Reservoirs (water); Solvents; Continental scientific drillings; Fault geometry; Fluid pressures; Generic modeling; Subsurface lithology; Tendency analysis; Fault slips; decadal variation; earthquake event; earthquake magnitude; fault geometry; fault slip; literature review; rock mechanics; seismicity; India; Koyna; Maharashtra

LA-ICPMS U-Pb geochronology of detrital zircon grains from the Coconino, Moenkopi, and Chinle formations in the Petrified Forest National Park (Arizona) - Gehrels, G.; Giesler, D.; Olsen, P.; Kent, D.; Marsh, A.; Parker, W.; Rasmussen, C.; Mundil, R.; Irmis, R.; Geissman, J.; Lepre, C. (Geochronology, 2020)
Uranium-lead (U-Pb) geochronology was conducted by laser ablation - inductively coupled plasma mass spectrometry (LA-ICPMS) on 7175 detrital zircon grains from 29 samples from the Coconino Sandstone, Moenkopi Formation, and Chinle Formation. These samples were recovered from ∼520 m of drill core that was acquired during the Colorado Plateau Coring Project (CPCP), located in Petrified Forest National Park (Arizona). A sample from the lower Permian Coconino Sandstone yields a broad distribution of Proterozoic and Paleozoic ages that are consistent with derivation from the Appalachian and Ouachita orogens, with little input from local basement or Ancestral Rocky Mountain sources. Four samples from the Holbrook Member of the Moenkopi Formation yield a different set of Precambrian and Paleozoic age groups, indicating derivation from the Ouachita orogen, the East Mexico arc, and the Permo-Triassic arc built along the Cordilleran margin. A total of 23 samples from the Chinle Formation contain variable proportions of Proterozoic and Paleozoic zircon grains but are dominated by Late Triassic grains. LA-ICPMS ages of these grains belong to five main groups that correspond to the Mesa Redondo Member, Blue Mesa Member and lower part of the Sonsela Member, upper part of the Sonsela Member, middle part of the Petrified Forest Member, and upper part of the Petrified Forest Member. The ages of pre-Triassic grains also correspond to these chronostratigraphic units and are interpreted to reflect varying contributions from the Appalachian orogen to the east, Ouachita orogen to the southeast, Precambrian basement exposed in the ancestral Mogollon Highlands to the south, East Mexico arc, and Permian-Triassic arc built along the southern Cordilleran margin. Triassic grains in each chronostratigraphic unit also have distinct U and thorium (Th) concentrations, which are interpreted to reflect temporal changes in the chemistry of arc magmatism. Comparison of our LA-ICPMS ages with available chemical abrasion thermal ionization mass spectrometry (CA-TIMS) ages and new magnetostratigraphic data provides new insights into the depositional history of the Chinle Formation, as well as methods utilized to determine depositional ages of fluvial strata. For parts of the Chinle Formation that are dominated by fine-grained clastic strata (e.g., mudstone and siltstone), such as the Blue Mesa Member and Petrified Forest Member, all three chronometers agree (to within ∼ 1 Myr), and robust depositional chronologies have been determined. In contrast, for stratigraphic intervals dominated by coarse-grained clastic strata (e.g., sandstone), such as most of the Sonsela Member, the three chronologic records disagree due to recycling of older zircon grains and variable dilution of syn-depositional-age grains. This results in LA-ICPMS ages that significantly predate deposition and CA-TIMS ages that range between the other two chronometers. These complications challenge attempts to establish a well-defined chronostratigraphic age model for the Chinle Formation. © 2020 George Gehrels et al.
cited By 9

Ecological opportunity enabled invertebrate radiations in ancient Lake Ohrid - Stelbrink, Bj{orn; Wilke, Thomas; Albrecht, Christian (Journal of Great Lakes Research, 2020)
Ancient Lake Ohrid is the oldest and biologically most diverse freshwater lake in Europe. The recent deep-drilling campaign SCOPSCO provided detailed insights into the lake's limnological history over the past 1.36 my. However, it remains unclear what factors triggered the onset of radiations and whether diversification rates remained constant throughout their evolution. We therefore inferred time-calibrated molecular phylogenies for eight invertebrate groups endemic to Lake Ohrid and performed diversification-rate analyses for the four most species-rich groups. The molecular-clock analyses indicate that few groups possibly originated in springs or rivers in the proto-Balkans’ during the pre-lake phase. The onset of all other radiations, however, can be correlated to one of the three limnological phases in the Ohrid Graben and in Lake Ohrid since 1.9 mya. We therefore assume that the onset of radiations was triggered by an increased ecological opportunity arising from massive environmental changes in the course of the lake deepening. The diversification-rate analyses further indicate that the groups examined diversified with a constant rate. Although the reconstruction of the early evolutionary history of these groups remains challenging, our data suggest that the relatively stable conditions in Lake Ohrid together with its high buffer capacity likely prevented significant changes in diversification rates over time. © 2020 International Association for Great Lakes Research
Keywords: Balkans; Lake Ohrid; Invertebrata; Mya; Ecology; Ancient lakes; Buffer capacity; Deep drilling; Environmental change; Evolutionary history; Fresh water lakes; Molecular clock; Molecular phylogeny; adaptive radiation; evolution; invertebrate; lacustrine environment; phylogenetics; phylogeny; Lakes

Glacial-interglacial cycles largely controlled mass movements during the late Quaternary in Lake El'gygytgyn, Siberia - Warnke, F.; Gebhardt, C.; Niessen, F. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2020)
Density-driven mass movement deposits (MMDs) were mapped throughout the Quaternary sedimentary record of Lake El'gygytgyn (NE Siberia) using high-resolution acoustic data. Three different acoustic facies types were identified in the lake: (1) pelagic sediment, (2) plastic flow deposits and (3) turbidites. Deposits from plastic flows are dominantly present proximal to the lakes' slopes, whereas deposits from turbidity currents occur more spatially distributed. During glacial times, the distribution of MMDs was more uniform, while during interglacial periods, MMDs were deposited predominantly close to the slope of the northwestern area. Furthermore, the overall number of MMDs and accumulated sediment volume significantly varies between glacial/interglacial periods. About 1.6 times more MMDs were mapped during interglacials, contributing to a 3.5 times higher sediment volume. The main reason for this large difference is that a significant increase in plastic flows were formed during interglacials, which account for a much larger volume of sediments when compared with the glacial intervals characterized by increased amount of turbidites. It appears that the most important source areas for MMDs are located at the northern and western shores. Cycles of lake level changes caused by variations in climate conditions between glacials and interglacials are likely the main trigger mechanism for the generation of these MMDs. The climate-dependent genesis and partly erosive potential influencing the sedimentary record contain implications to consider for future paleo-environmental reconstructions in lacustrine settings. © 2019 Elsevier B.V.
cited By 0
Keywords: glacial-interglacial cycle; lacustrine deposit; lake level; mass movement; paleoclimate; paleoenvironment; Quaternary; reconstruction; slope failure; turbidity current; Chukchi; Elgygytgyn Lake; Russian Federation; Siberia

Lacustrine high resolution sequence records from Upper Cretaceous Nenjiang Formation in Songliao Basin - Gao, Y.; Jiao, Y.; Wang, P.; Cheng, R.; Wang, G. (Global Geology, 2020)

Geophysical Borehole Observatory at the North Anatolian Fault in the Eastern Sea of Marmara (GONAF): initial results - Kılıç, Tuğbay; Kartal, Recai F.; Kadirioğlu, Filiz T.; Bohnhoff, Marco; Nurlu, Murat; Acarel, Diğdem; Garzon, Patricia Mart'inez; {Ozsarac, Vedat (Journal of Seismology, 2020)
Given its intense seismic activity and damaging earthquake generation potential, the western part of the North Anatolian Fault constitutes a serious natural hazard. As a result, the fault is monitored with a broad range of seismological and geodetic instrumentation making it a natural laboratory environment for scientific studies. One of the long-term projects in this region is GONAF (Geophysical Borehole Observatory at the North Anatolian Fault) which is the first borehole seismometer network project in Turkey. GONAF is a joint research project that started in 2011 as joint initiative of the Turkish Ministry of Interior, Disaster and Emergency Management Presidency AFAD and GFZ and the German Research Center for Geoscience Helmholtz Center Potsdam. The aim of GONAF is to detect, examine, and monitor the microseismic activity in the region and to observe the physical processes before, during and after a large Marmara earthquake (M > 7.0) that is expected to rupture the western part of the North Anatolian Fault, below the Marmara Sea along the Princes Islands segment or even further to the west. For this purpose, the permanent GONAF observatory was established consisting of 7 borehole seismometer arrays installed down to a depth of 300 m. In this paper, we report on regional stress changes in the western part of the North Anatolian Fault Zone (NAFZ) using instrumental data and the Coulomb stress method. We also present preliminary results of the observation and evaluation of microseismic activity obtained from the GONAF observatory. For the automatic evaluation of real-time data, Seiscomp3, RTQUAKE, and Earthworm Softwares were used. Within the scope of automatic earthquake detection studies, between March, 2016 and November, 2017, a total of 2568 earthquakes were detected using the RTQUAKE software. Of these, 1459 could be analyzed. While the magnitude of the analyzed earthquakes varies between 0.8 and 4.2, the depth of these events ranges from 2 to 30 km. © 2020, Springer Nature B.V.
Keywords: Sea of Marmara; Turkey; borehole geophysics; Coulomb criterion; earthquake damage; earthquake magnitude; geophysical method; seismograph; seismology

ExoMars raman laser spectrometer: A tool for the potential recognition of wet-target craters on mars - Veneranda, M.; Lopez-Reyes, G.; Manrique, J.A.; Medina, J.; Ruiz-Galende, P.; Torre-Fdez, I.; Castro, K.; Lantz, C.; Poulet, F.; Dypvik, H.; Werner, S.C.; Rull, F. (Astrobiology, 2020)
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.
cited By 14

Electric discharge evidence found in a new class of material in the Chicxulub ejecta - Kletetschka, G.; Ocampo Uria, A.; Zila, V.; Elbra, T. (Scientific Reports, 2020)
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).
cited By 6

Electrical conductivity of Icelandic deep geothermal reservoirs up to supercritical conditions: Insight from laboratory experiments - Nono, Franck; Gibert, Benoit; Parat, Fleurice; Loggia, Didier; Cichy, Sarah B.; Violay, Marie (Journal of Volcanology and Geothermal Research, 2020)

Emission spectra of a simulated Chicxulub impact-vapor plume at the Cretaceous –Paleogene boundary - Navarro, K.F.; Urrutia-Fucugauchi, J.; Villagran-Muniz, M.; S'anchez-Ak'e, C.; Pi-Puig, T.; P'erez-Cruz, L.; Navarro-Gonz'alez, R. (Icarus, 2020)
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.
cited By 2

Engineered carbon mineralization in ultramafic rocks for CO2 removal from air: Review and new insights - Kelemen, Peter B.; McQueen, Noah; Wilcox, Jennifer; Renforth, Phil; Dipple, Greg; Vankeuren, Amelia Paukert (Chemical Geology, 2020)

Environmental changes in Arctic Chukotka during Marine Isotope Stages 38-31: implications for the Early to Middle Pleistocene transition - Lozhkin, Anatoly V.; Anderson, Patricia M.; Minyuk, Pavel S.; Korzun, Julia A.; Nedorubova, Ekaterina Y.; Kirillova, Mariana A. (Boreas, 2020)

Environmental changes in the eastern Arctic 1.6975-1.965 Ma, palynological investigations from El'gygytgyn Lake, northeastern Russia - Lozhkin, Anatoly V.; Anderson, Patricia M. (Review of Palaeobotany and Palynology, 2020)

Exploring by boring: Geothermal wells as research tools - Jordan, T.; Fulton, P.; Tester, J.; Asanuma, H.; Bruhn, D. (Eos, 2020)

Effect of Perforation Interval Design on Gas Production from the Validated Hydrate-Bearing Deposits with Layered Heterogeneity by Depressurization - Xia, Y.; Xu, T.; Yuan, Y.; Xin, X. (Geofluids, 2020)
Natural gas hydrate is considered as one of the best potential alternative resource to address the world's energy demand. The available geological data at the Mallik site of Canada indicates the vertical heterogeneities of hydrate reservoir petrophysical properties. According to the logging data and sample analysis results at the Mallik 2L-38 well, a 2D model of geologically descriptive hydrate-bearing sediments was established to investigate the multiphase flow behaviors in hydrate reservoir induced by gas recovery and the effects of perforation interval on gas production performance. Firstly, the constructed model with vertical heterogeneous structures of permeability, porosity, and hydrate saturation was validated by matching the measured data in the Mallik 2007 test. The excessive residual methane in the hydrate reservoir observed in simulated results indicates insufficient gas production efficiency. For more effective methane recovery from a hydrate reservoir, the effect of perforation interval on long-term gas production performance was investigated based on the validated reservoir model. The simulation results suggest that both the location and length of the perforation interval have significant impact on hydrate dissociation behavior, while the gas production performance is mainly affected by the length of the perforation interval. To be specific, an excellent gas release performance is found in situations where the perforation interval is set at the interface between a hydrate reservoir and an underlying water-saturated zone. By increasing the perforation interval lengths of 5 m, 8 m, and 10 m, the gas release volumes from hydrate dissociation and gas production volumes from production wells are increased by 34%, 52%, and 57% and 37%, 58%, and 62%, respectively. © 2020 Yingli Xia et al.
cited By 6
Keywords: bearing capacity; gas hydrate; gas production; gas supply; hydrocarbon reservoir; natural gas; permeability; porosity; reservoir characterization; two-dimensional modeling; Canada

Explosive interaction of impact melt and seawater following the Chicxulub impact event - Osinski, G.R.; Grieve, R.A.F.; Hill, P.J.A.; Simpson, S.L.; Cockell, C.; Christeson, G.L.; Ebert, M.; Gulick, S.; Melosh, H.J.; Riller, U.; Tikoo, S.M.; Wittmann, A. (Geology, 2020)
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.
cited By 21

Filling a gap in the evolution of charophytes during the Turonian to Santonian: Implications for modern physiognomy - Li, S.; Wang, Q.; Zhang, Y.; Wan, X.; Mart'in-Closas, C. (Review of Palaeobotany and Palynology, 2020)
The fossil record of Turonian to Santonian charophytes is very poor worldwide, probably due to the limited non-marine records from this age, when there was a global high stand in the relative sea level and, thus, a reduction in non-marine habitats. After this gap, the charophyte floras changed to their modern physiognomy, with dominance of the Characeae. Charophytes from the Turonian to Santonian in the Songliao Basin help to fill this significant gap in the evolution of charophytes. The recorded flora is formed by one member of the Clavatoraceae, Atopochara trivolvis var. restricta, and a greater diversity of Characeae, including Nodosochara (Turbochara) heilongjiangensis comb. nov., Lamprothamnium ellipticum, Lychnothamnus barbosai and Lychnothamnus quantouensis comb. nov. These findings showed that the Characeae began to dominate charophyte floras during the global sea level high stand, up to 8 Ma earlier than previously reported. The occurrence of the genus Lychnothamnus in the Turonian in the Songliao Basin represents the oldest record in Eurasia of this still-living genus. The occurrence of A. trivolvis var. restricta in the Turonian to Santonian in China in comparison with its previous records in the Albian? –Cenomanian in Europe indicates that this variety survived as a relict in North China, while the more-derived variety Atopochara trivolvis var. multivolvis had evolved elsewhere. The charophyte flora thrived in large, shallow, permanent freshwater lakes and sometimes in palustrine settings of the Quantou, Qingshankou and Yaojia formations, which explains its higher biodiversity in contrast with the other records that belong mainly to brackish settings. © 2019 Elsevier B.V.
cited By 1
Keywords: biodiversity; biogeography; charophyte; dominance; flora; fossil record; lacustrine environment; paleoecology; Santonian; sea level; sedimentology; species diversity; species occurrence; taphonomy; Turonian; China; Europe; Songliao Basin; Characeae; Charales; Clavatoraceae; Lamprothamnium; Lychnothamnus

Flood frequency estimation and uncertainty in arid/semi-arid regions - Metzger, Asher; Marra, Francesco; Smith, James A.; Morin, Efrat (Journal of Hydrology, 2020)

Fluid Infiltration Through Oceanic Lower Crust in Response to Reaction-Induced Fracturing: Insights From Serpentinized Troctolite and Numerical Models - Yoshida, Kazuki; Okamoto, Atsushi; Shimizu, Hiroyuki; Oyanagi, Ryosuke; Tsuchiya, Noriyoshi; Party, Oman Drilling Project Phase 2 Science (Journal of Geophysical Research: Solid Earth, 2020)

Generation of sintered fault rock and its implications for earthquake energetics and fault healing - Hirono, Tetsuro; Kaneki, Shunya; Ishikawa, Tsuyoshi; Kameda, Jun; Tonoike, Naoya; Ito, Akihiro; Miyazaki, Yuji (Communications Earth and Environment, 2020)

Geochemistry, geochronology and petrogenesis of Maya Block granitoids and dykes from the Chicxulub Impact Crater, Gulf of M'exico: Implications for the assembly of Pangea - Zhao, J.; Xiao, L.; Gulick, S.P.S.; Morgan, J.V.; Kring, D.; Fucugauchi, J.U.; Schmieder, M.; Graaff, S.J.; Wittmann, A.; Ross, C.H.; Claeys, P.; Pickersgill, A.; et al. (Gondwana Research, 2020)
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 Yucat'an peninsula in the Gulf of M'exico, 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
cited By 23

Geochronology and Stable Isotope Analysis of Fracture Fill and Karst Mineralization Reveal Sub-Surface Paleo-Fluid Flow and Microbial Activity of the COSC-1 Borehole, Scandinavian Caledonides - Drake, Henrik; Roberts, Nick M. W.; Whitehouse, Martin J. (Geosciences, 2020)
The deep biosphere hosted in fractured rocks within the upper continental crust is one of the least understood and studied ecological realms on Earth. Scarce knowledge of ancient life and paleo-fluid flow within this realm is owing to the lack of deep drilling into the crust. Here we apply microscale high spatial-resolution analytical techniques to fine-grained secondary minerals in a deep borehole (COSC-1) drilled into the Silurian-Devonian Scandinavian Caledonide mountain range in central Sweden. The aim is to detect and date signs of ancient microbial activity and low-temperature fluid circulation in micro-karsts (foliation-parallel dissolution cavities in the rock) and fractures at depth in the nappe system. Vein carbonates sampled at 684 to 2210 m show a decreased C isotope variability at depths below 1050 m; likely due to decreased influence of organic-C at great depth. Micro-karsts at 122{ –178 m depth feature at least two generations of secondary calcite and pyrite growth in the voids as shown by secondary ion mass spectrometry analytical transects within individual grains. The younger of these two precipitation phases shows 34S-depleted δ34Spyrite values ( −19.8 ± 1.6 ‰ vs. Vienna-Canyon Diablo Troilite (V-CDT)) suggesting microbial sulfate reduction in situ. The calcite of this late phase can be distinguished from the older calcite by higher δ18Ocalcite values that correspond to precipitation from ambient meteoric water. The late stage calcite gave two separate laser ablation inductively coupled mass spectrometry-derived U-Pb ages (9.6 ± 1.3 Ma and 2.5 ± 0.2 Ma), marking a minimum age for widespread micro-karst formation within the nappe. Several stages of fluid flow and mineral precipitation followed karst formation; with related bacterial activity as late as the Neogene-Quaternary; in structures presently water conducting. The results show that our combined high spatial-resolution stable isotope and geochronology approach is suitable for characterizing paleo-fluid flow in micro-karst; in this case, of the crystalline crust comprising orogenic nappe units.
Keywords: stable isotopes; Caledonides; deep drilling (COSC-1); in situ U-Pb geochronology; secondary minerals

Explosive interaction of impact melt and seawater following the Chicxulub impact event - Osinski, Gordon R.; Grieve, Richard A.F.; Hill, Patrick J.A.; Simpson, Sarah L.; Cockell, Charles; Christeson, Gail L.; Ebert, Matthias; Gulick, Sean; Melosh, H. Jay; Riller, Ulrich; Tikoo, Sonia M.; Wittmann, Axel (Geology, 2019)
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.

Raw IRM measurements of composite sediment core ICDP5045-1 from Lake Ohrid, Balkans - Just, Janna; Sagnotti, Leonardo; Nowaczyk, Norbert R; Francke, Alexander; Wagner, Bernd (PANGAEA, 2019)

Quaternary history of the Lake Magadi Basin, southern Kenya Rift: Tectonic and climatic controls - Bernhart Owen, R.; Renaut, Robin W.; Muiruri, Veronica M.; Rabideaux, Nathan M.; Lowenstein, Tim K.; McNulty, Emma P.; Leet, Kennie; Deocampo, Daniel; Luo, Shangde; Deino, Alan L.; Cohen, Andrew; Sier, Mark J.; et al. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2019)

Quantitative estimates of orbital and millennial scale climatic variability in central Mexico during the last ∼40,000 years - Caballero, M.; Lozano-Garc'ia, S.; Ortega-Guerrero, B.; Correa-Metrio, A. (Quaternary Science Reviews, 2019)
Diatom-based transfer functions for salinity, precipitation and temperature were developed using a training set that included data from 40 sites along central Mexico. These transfer functions showed good performance parameters and were subsequently applied to the previously published diatom record from lake Chalco, southern Basin of Mexico. Heinrich stadials (HS-3 to HS-0) were reconstructed as cold and dry events, with HS-2 representing the coldest and driest conditions, while HS-1 shows a complex bimodal cooling pattern. Orbital scale variability is also recorded. High and variable lake salinities from ∼34 to 29 ka BP (marine isotope stage 3, MIS-3) corresponded with times of maximum summer insolation and evidences of frequent fires. MIS-2 was identified as a cold period, with low lake salinity associated with low evaporation, with two cold intervals during the minima in spring (∼25.5 ka BP) and summer (∼20 ka BP) insolation. The ∼20 ka BP cold event together with HS-2 (24-23 ka BP), defined a bimodal maximum cooling during the last glacial maximum (LGM: 24.5 –19.5 ka BP) within the range of pollen-based estimates, further supporting a maximum tropical cooling of 4 –5 °C for the LGM. The deglacial (19.5 –11.5 ka BP) showed the highest precipitation anomalies with three peaks that closely correlated with glacier advances in the nearby mountains (Iztaccihuatl). The early Holocene marked a change towards high lake salinities and the highest positive temperature anomalies (+3.5 °C) during a peak in summer insolation. Even though at orbital scale Chalco showed a nearly opposite trend to the record from the more southerly lake Peten-Itza (Guatemala), at millennial scale it showed a common pattern of cold and dry conditions during HSs, comparable to other tropical latitude sites in the northern hemisphere and further supporting the idea that there is a strong coupling between tropical and higher latitudes climates, in particular with the North Atlantic. © 2018 Elsevier Ltd
cited By 28
Keywords: Glacial geology; Incident solar radiation; Lakes; Paleolimnology; Tropics; Diatoms; Late Pleistocene; Micropaleontology; Monsoon; North America; Paleoclimatology; Transfer functions; climate variation; diatom; micropaleontology; monsoon; paleoclimate; paleolimnology; paleotemperature; Pleistocene; precipitation (climatology); quantitative analysis; salinity; transfer function; Atlantic Ocean; Atlantic Ocean (North); Guatemala [Central America]; Lake Peten Itza; Mexico [North America]; Peten; Valley of Mexico; Bacillariophyta

Q value analysis of deep seismic reflection data of Well SK-2 and its determination of gas-bearing stratum; [松科二井深地震反射数据 Q值分析及其对含气层位的确定] - Guo, Rui; Hou, Hesheng; Fu, Wei; Yang, Jin; Feng, Xuan; Lu, Zhanwu; Zhou, Huailai (Geology in China, 2019)
When the seismic wave propagates in the underground media, the seismic wave energy will show a certain degree of attenuation. The quality factor Q is an important parameter for measuring the absorption and attenuation properties of the underground rock, and is of great significance for describing the lithological characteristics and predicting the oil and gas distribution. In this paper, the Q value analysis technique based on S transformation ratio method for deep seismic reflection data was developed, and the more accurate Q value was obtained. Taking the Shahezi Formation in the Songliao Basin as the main target layer, the authors calculated the Q value of the post-stack deep seismic reflection profile across Well SK-2, and then generated the Q value profile to summarize Q value distribution characteristics of the Shahezi Formation. The Q value distribution characteristics, combined with the logging, stratification and gas anomaly data of Well SK-2, suggest that the Shahezi Formation is a gas reservoir, and this discovery provides a way for the next deep reservoir prediction. This conclusion provides an idea for the further deep reservoir prediction and can serve the deep geological survey project in Northeast China. © 2019 Editorial Board of Geology in China. All rights reserved.

Provenance and tectonic implications of the 3.28 –3.23 Ga Fig Tree Group, central Barberton greenstone belt, South Africa - Drabon, Nadja; Gali, Aleksandra; Mason, Paul R.D.; Lowe, Donald R. (Precambrian Research, 2019)

Project Report: Grinding Through the Ediacaran-Cambrian Transition - Rose, C. V.; Prave, A.R.; Bergmann, K. D.; Condon, D. J.; Kasemann, S. A.; MacDonald, F. A.; Hoffmann, K.-H.; Trindade, R. I. F.; Zhu, M. (Communications of the Geological Survey of Namibia, 2019)

Progress on Continental Scientific Drilling Project of Cretaceous Songliao Basin (SK-1 and SK-2) - Gao, Y.; Wang, C.; Wang, P.; Huang, Y.; Zou, C. (Science Bulletin, 2019)
cited By 21

Practice of turbodrill core drilling in well SK-2 (in Chinese with English abstract);[松科2井带涡轮钻具取心钻进探索] - Yan, J.; Wang, W.; Zhang, H.; Xu, J.; Cao, L. (Drilling & Production Technology, 2019)

Re-evaluating the age of deep biosphere fossils in the lockne impact structure - Tillberg, M.; Ivarsson, M.; Drake, H.; Whitehouse, M.J.; Kooijman, E.; Schmitt, M. (Geosciences (Switzerland), 2019)
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.
cited By 6

Practice of Turbo-drill core drilling in Well SK-2 - Jia, Yan; Wenshi, Wang; Hengchun, Zhang; Jie, Xu; Longlong, Cao (Drilling & Production Technology, 2019)

Pollen-based temperature and precipitation changes in the Ohrid Basin (western Balkans) between 160 and 70 ka - Sinopoli, G.; Peyron, O.; Masi, A.; Holtvoeth, J.; Francke, A.; Wagner, B.; Sadori, L. (Climate of the Past, 2019)
Our study aims to reconstruct climate changes that occurred at Lake Ohrid (south-western Balkan Peninsula), the oldest extant lake in Europe, between 160 and 70 ka (covering part of marine isotope stage 6, MIS 6; all of MIS 5; and the beginning of MIS 4). A multi-method approach, including the Modern Analog Technique and the Weighted Averaging Partial Least-Squares Regression, is applied to the high-resolution pollen sequence of the DEEP site, collected from the central part of Lake Ohrid, to provide quantitative estimates of climate and bioclimate parameters. This allows us to document climatic change during the key periods of MIS 6 and MIS 5 in southern Europe, a region where accurate climate reconstructions are still lacking for this time interval. Our results for the penultimate glacial show cold and dry conditions, while the onset of the last interglacial is characterized by wet and warm conditions, with temperatures higher than today (by ca. 2 <span classCombining double low lineinline-formula>ĝC). The Eemian also shows the well-known climatic tri-partition in the Balkans, with an initial pre-temperate phase of abrupt warming (128-121 ka), a central temperate phase with decreasing temperatures associated with wet conditions (121-118 ka), followed by a post-temperate phase of progressive change towards cold and dry conditions (118-112 ka). After the Eemian, an alternation of four warm/wet periods with cold/dry ones, likely related to the succession of Greenland stadials and cold events known from the North Atlantic, occurred. The observed pattern is also consistent with hydrological and isotopic data from the central Mediterranean. The Lake Ohrid climate reconstruction shows greater similarity with climate patterns inferred from northern European pollen records than with southern European ones, which is probably due to its intermediate position and the mountainous setting. However, this hypothesis needs further testing as very few climate reconstructions are available for southern Europe for this key time period. . © Author(s) 2019.
cited By 12
Keywords: climate variation; Eemian; marine isotope stage; paleoclimate; pollen; precipitation (climatology); temperature; Atlantic Ocean; Atlantic Ocean (North); Balkans; Lake Ohrid; Southern Europe

Planning an International Magma Observatory - Eichelberger, J. (Eos, 2019)

Petrophysical characteristics of Huoshiling Formation from CCSD SK- 2 in the Songliao Basin of Northeast China; [松科二井火石岭组地层岩石物理学特征研究] - Hu, Dingyu; Zou, Changchun; Peng, Cheng; Wang, Wenshi; L{u, Qingtian; Hou, Hesheng; Zhu, Yongyi; Zhang, Jinchang; Zhang, Hengchun; Ding, Yujiao; Lin, Feng; Cui, Liwei; et al. (Geology in China, 2019)
The Continental Scientific Drilling Project in the Songliao Basin was aimed at solving a series of scientific problems involved in Cretaceous paleoclimate and paleoenvironmental research, the development of deep exploration techniques, and the earth's deep resource survey. As the main borehole of the scientific drilling project of Songliao Basin, SK- 2 has collected continuous and in- situ geophysical log data. In this paper, geophysical log data were used to reveal the range of petrophysical parameters of rocks in Huoshiling Formation. Combined with laboratory core NMR test analysis, the authors studied the pore structure characteristics of different igneous reservoirs. The results show that the Huoshiling Formation mainly consists of andesite, tuff, complex conglomerate and tuff mudstone. The igneous facies are dominated by the explosive facies and the effusion facies. The andesite and complex conglomerate are characterized by high resistivity and low acoustic wave time difference. The characteristics of the tuff are low resistivity and high acoustic time difference, and the tuff mudstone has the lowest resistivity. The reservoir has the characteristics of low porosity and low permeability, but the tuff reservoir has developed small and medium pores and has relatively good physical properties, and hence it is a favorable reservoir. The research results provide strong support for further evaluation of deep oil and gas resources and stratigraphic structure in the Songliao Basin. © 2019 Editorial Board of Geology in China. All rights reserved.

Petrophysical characteristics of Huoshiling Formation from CCSD SK- 2 in the Songliao Basin of Northeast China [松科二井火石岭组地层岩石物理学特征研究] - Hu, D.; Zou, C.; Peng, C.; Wang, W.; L{u, Q.; Hou, H.; Zhu, Y.; Zhang, J.; Ding, Y.; Lin, F.; Cui, L.; Dou, R.; et al. (Geology in China, 2019)
The Continental Scientific Drilling Project in the Songliao Basin was aimed at solving a series of scientific problems involved in Cretaceous paleoclimate and paleoenvironmental research, the development of deep exploration techniques, and the earth's deep resource survey. As the main borehole of the scientific drilling project of Songliao Basin, SK- 2 has collected continuous and in- situ geophysical log data. In this paper, geophysical log data were used to reveal the range of petrophysical parameters of rocks in Huoshiling Formation. Combined with laboratory core NMR test analysis, the authors studied the pore structure characteristics of different igneous reservoirs. The results show that the Huoshiling Formation mainly consists of andesite, tuff, complex conglomerate and tuff mudstone. The igneous facies are dominated by the explosive facies and the effusion facies. The andesite and complex conglomerate are characterized by high resistivity and low acoustic wave time difference. The characteristics of the tuff are low resistivity and high acoustic time difference, and the tuff mudstone has the lowest resistivity. The reservoir has the characteristics of low porosity and low permeability, but the tuff reservoir has developed small and medium pores and has relatively good physical properties, and hence it is a favorable reservoir. The research results provide strong support for further evaluation of deep oil and gas resources and stratigraphic structure in the Songliao Basin. © 2019 Editorial Board of Geology in China. All rights reserved.
cited By 3

Petrography and geochemistry of the impact to postimpact transition layer at the El'gygytgyn impact structure in Chukotka, Arctic Russia - Maierhofer, K.; Koeberl, C.; Brigham-Grette, J. (Meteoritics and Planetary Science, 2019)
The 3.6 Ma El'gygytgyn impact structure, located in northeast Chukotka in Arctic Russia, was largely formed in acidic volcanic rocks. The 18 km diameter circular depression is today filled with Lake El'gygytgyn (diameter of 12 km) that contains a continuous record of lacustrine sediments of the Arctic from the past 3.6 Myr. In 2009, El'gygytgyn became the focus of the International Continental Scientific Drilling Program (ICDP) in which a total of 642.4 m of drill core was recovered. Lithostratigraphically, the drill cores comprise lacustrine sediment sequences, impact breccias, and deformed target rocks. The impactite core was recovered from 316.08 to 517.30 meters below lake floor (mblf). Because of the rare, outstanding recovery, the transition zone, ranging from 311.47 to 317.38 m, between the postimpact lacustrine sediments and the impactite sequences, was studied petrographically and geochemically. The transition layer comprises a mixture of about 6 m of loose sedimentary and volcanic material containing isolated clasts of minerals and melt. Shock metamorphic effects, such as planar fractures (PFs) and planar deformation features (PDFs), were observed in a few quartz grains. The discoveries of silica diaplectic glass hosting coesite, kinked micas and amphibole, lechatelierite, numerous impact melt shards and clasts, and spherules are associated with the impact event. The occurrence of spherules, impact melt clasts, silica diaplectic glass, and lechatelierite, about 1 m below the onset of the transition, marks the beginning of the more coherent impact ejecta layer. The results of siderophile interelement ratios of the transition layer spherules give indications of the relative contribution of the meteoritical component. © 2019 The Authors. Meteoritics & Planetary Science published by Wiley Periodicals, Inc. on behalf of The Meteoritical Society (MET).
cited By 1

Peering inside the peak ring of the Chicxulub Impact Crater–its nature and formation mechanism - Urrutia-Fucugauchi, J.; P'erez-Cruz, L.; Morgan, J.; Gulick, S.; Wittmann, A.; Lofi, J.; Morgan, J.V.; Gulick, S.P.S.; Chenot, E.; Christeson, G.; Claeys, P.; Cockell, C.; et al. (Geology Today, 2019)
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
cited By 0

On the mophology, measurement and description of Triprojectacites (in Chinese with English abstract);[三突起类花粉形态学及其度量和描述] - Wu, Y.; Li, J.; Zhu, H. (Acta Palaeontologica Sinica, 2019)

Pattern of cell division in ∼3.4 Ga-old microbes from South Africa - Kaźmierczak, J'ozef; Kremer, Barbara (Precambrian Research, 2019)

Northeast Atlantic breakup volcanism and consequences for Paleogene climate change-MagellanPlus Workshop report - Berndt, C.; Planke, S.; Teagle, D.; Huismans, R.; Torsvik, T.; Frieling, J.; Jones, M.T.; Jerram, D.A.; Tegner, C.; Inge Faleide, J.; Coxall, H.; Hong, W.-L. (Scientific Drilling, 2019)
The northeast Atlantic encompasses archetypal examples of volcanic rifted margins. Twenty-five years after the last ODP (Ocean Drilling Program) leg on these volcanic margins, the reasons for excess melting are still disputed with at least three competing hypotheses being discussed. We are proposing a new drilling campaign that will constrain the timing, rates of volcanism, and vertical movements of rifted margins. This will allow us to parameterise geodynamic models that can distinguish between the hypotheses. Furthermore, the drilling-derived data will help us to understand the role of breakup magmatism as a potential driver for the Palaeocene-Eocene thermal maximum (PETM) and its influence on the oceanographic circulation in the earliest phase of the northeast Atlantic Ocean formation. Tackling these questions with a new drilling campaign in the northeast Atlantic region will advance our understanding of the long-term interactions between tectonics, volcanism, oceanography, and climate and the functioning of subpolar northern ecosystems and climate during intervals of extreme warmth. © Author(s) 2019.
cited By 3
Keywords: Geodynamics; Infill drilling; Volcanoes; Geodynamic models; Long-term interaction; North East Atlantic; Northeast Atlantic Ocean; Ocean drilling programs; Oceanographic circulation; Paleogene climate; Vertical movement; Climate change

Recycling of archaeal biomass as a new strategy for extreme life in Dead Sea deep sediments - Thomas, Camille; Grossi, Vincent; Antheaume, Ingrid; Ariztegui, Daniel (Geology, 2019)

Modern sedimentation processes in Lake Towuti, Indonesia, revealed by the composition of surface sediments - Hasberg, Ascelina K. M.; Bijaksana, Satria; Held, Peter; Just, Janna; Morlock, Marina A.; Opitz, Stephan; Russell, James M. (Sedimentology, 2019)
Lake Towuti on Sulawesi Island, Indonesia, is located within the heart of the Indo-Pacific Warm Pool. This tropical lake is surrounded by ultramafic (ophiolitic) rocks and lateritic soils that create a unique ferruginous depositional setting. In order to understand modern sediment deposition in Lake Towuti, a set of 84 lake surface sediment samples was collected from across the entirety of the lake and samples were analyzed for their physical, chemical, mineralogical and biological constituents. End-member analyses were carried out to elucidate modern sediment origin, transport and depositional processes. This study found that allochthonous sediment, characterized by the concentrations of the elements Mg, Fe, Si and Al, as well as the clay and serpentine minerals, is dominated by fluvial supply from five distinct source areas. Granulometric data and the occurrence of organic matter of a terrestrial origin suggest that, in the southern and north-eastern parts of the lake the near-shore sediments may additionally be influenced by mass wasting. This is due at least partly to the particularly steep slopes in these areas. Furthermore, sediment composition suggests that sediment transport into deeper parts of the lake, particularly in the northern basin, is partly controlled by gravitational and density-driven processes such as turbidity currents. Directional sediment transport by persistent lake currents, in contrast, appears to be less important. Organic matter deposition in the ultra-oligotrophic lake, albeit limited, is dominated by autochthonous production, but with some contribution of fluvial and gravitational supply. Biogenic silica deposition, primarily from diatom frustules and sponge spicules, is very limited and is concentrated in only a few areas close to the shoreline that are characterized by shallow waters, but away from the areas of high suspension loads at the mouths of the major inlets. The results of this study build upon current and published work on short piston cores from Lake Towuti. Conversely, the results will support the interpretation of the depositional history and past climatic and environmental conditions derived from the composition of much longer records, which were obtained by the Towuti Drilling Project in May 2015 and are currently under investigation. © 2018 The Authors. Sedimentology © 2018 International Association of Sedimentologists
Keywords: Greater Sunda Islands; Lake Towuti; Malili Lakes; South Sulawesi; Sulawesi; Sunda Isles; Bacillariophyta; Biogeochemistry; Biological materials; Chemical analysis; Gravitation; Ocean currents; Organic compounds; Sediment transport; Sedimentation; Serpentine; Silica; Silicate minerals; Surficial sediments; Suspensions (fluids); Depositional process; Environmental conditions; Pacific warm pool; Provenance analysis; Redox condition; Sediment composition; Sedimentation process; Tropical lakes; depositional environment; lacustrine deposit; provenance; redox conditions; sediment transport; sedimentation; shallow water; Lakes

Mount Sedom salt diapir - Source for sulfate replenishment and gypsum supersaturation in the last glacial Dead Sea (Lake Lisan) - Levy, E.J.; Sivan, O.; Antler, G.; Lazar, B.; Stein, M.; Yechieli, Y.; Gavrieli, I. (Quaternary Science Reviews, 2019)
During the late Quaternary several hypersaline lakes occupied the tectonic depression of the Dead Sea Basin, depositing sequences of primary-evaporitic mineral phases: aragonite (CaCO3), gypsum (CaSO4·2H2O) and halite (NaCl). Aragonite and gypsum were the dominant primary mineral phases during the glacial periods and their formation required significant import of bicarbonate (HCO3 −) and sulfate (SO4 2−) ions to the lake. While bicarbonate was likely derived from dissolution of calcite in the watershed, the sources of sulfate remained elusive. Here we investigate and quantify the long-term sulfate reservoir changes in the deep waters (hypolimnion) of Lake Lisan (the last glacial Dead Sea) using concentrations and stable isotopes of sulfur in pore-fluids from the cores that were drilled at the lake floor (2010 –11) by ICDP (International Continental Drilling Program). From ca. 117ka, pore-fluid sulfate concentrations increased and the brine attained supersaturation with respect to gypsum, peaking during the last glacial maximum (LGM; ca. 20ka). Stable isotopes of pore-fluid sulfate (δ34S and δ18O) are similar to the values found in bulk sulfate minerals from the nearby Mount Sedom salt diapir. We suggest that relatively diluted and cool paleo-epilimnion water facilitated dissolution of halite and anhydrite (CaSO4) of the Mt. Sedom salt diapir, resulting in a localized increase in solution density. Subsequently, this solution sank and mixed with saline hypolimnion water, simultaneously replenishing chloride, sodium and sulfate reservoirs, while diluting it with respect to other solutes. The mixing of the calcium-rich gypsum saturated hypolimnion and the sulfate-rich sinking brine from above resulted in gypsum supersaturation. © 2019 Elsevier Ltd
cited By 10
Keywords: Calcite; Calcium carbonate; Carbonate minerals; Chloride minerals; Dissolution; Drilling fluids; Glacial geology; Gypsum; Infill drilling; Isotopes; Lakes; Reservoirs (water); Saline water; Salt tectonics; Sodium chloride; Supersaturation; Dead sea; Hypersaline lakes; Last glacial; Last Glacial Maximum; Mt. Sedom diapir; Pore fluids; Solution density; Sulfate concentrations; Sulfur compounds; diapir; gypsum; isotopic analysis; Last Glacial; porewater; sulfate; supersaturation; Dead Sea; Israel; Mount Sedom; Southern District

New geochronological constraints for the Upper Cretaceous Nenjiang Formation in the Songliao Basin, NE China - Yu, Z.; He, H.; Deng, C.; Xi, D.; Qin, Z.; Wan, X.; Wang, C.; Zhu, R. (Cretaceous Research, 2019)
The Nenjiang Formation in the Songliao Basin, northeastern China, is of great significance because it records a series of geological, geodynamical and paleoenvironmental events, such as lake transgression events, lake anoxic events, sea water incursion events, Cretaceous Normal Superchron, and important stratigraphic boundaries. Here we report a chronology for the non-marine Upper Cretaceous Nenjiang Formation based on secondary ion mass spectrometry (SIMS) U –Pb zircon analyses from the east borehole of the Cretaceous Continental Scientific Drilling and two outcrop sections, which are located in different structural provinces of the Songliao Basin. Stratigraphic correlation between the borehole sequence and the exposed outcrop sections is achieved by combining lithostratigraphy, biostratigraphy, and SIMS U –Pb zircon geochronology. Two bentonite layers are recognized in the Nenjiang Formation: the older occurs at the formational contact between the Yaojia and Nenjiang Formations; the younger occurs between Members 1 and 2 of the Nenjiang Formation. SIMS U –Pb zircon dating yields ages of 85.1 –85.2 Ma and 83.0 –83.3 Ma, respectively, representing ages of the boundaries of the Yaojia/Nenjiang Formations and Members 1/2 of the Nenjiang Formation, as well as ages of lake transgression events and associated lake anoxic events, and two of the sea water incursion events. Furthermore, the age of Cretaceous Normal Superchron termination can be estimated at 82.5 –82.8 Ma. © 2019 Elsevier Ltd
cited By 17
Keywords: Cretaceous; geochronology; mass spectrometry; paleoenvironment; uranium-lead dating; zircon; China; Songliao Basin

New shock microstructures in titanite (CaTiSiO5) from the peak ring of the Chicxulub impact structure, Mexico - Timms, N.E.; Pearce, M.A.; Erickson, T.M.; Cavosie, A.J.; Rae, A.S.P.; Wheeler, J.; Wittmann, A.; Ferrière, L.; Poelchau, M.H.; Tomioka, N.; Collins, G.S.; Gulick, S.P.S.; et al. (Contributions to Mineralogy and Petrology, 2019)
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) = < 110 > , and less commonly with the mode K1 = 130, η1 = <522 >. In some grains, 130 deformation bands have formed concurrently with the deformation twins, indicating dislocation slip with Burgers vector b = < 341 > 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 ( < 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 ( < 20 GPa) shock pressure. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.
cited By 18

Nonvolcanic Carbon Dioxide Emission at Continental Rifts: The Bublak Mofette Area, Western Eger Rift, Czech Republic - K{ampf, Horst; Broge, Alena Sophie; Marzban, Pouria; Allahbakhshi, Masoud; Nickschick, Tobias (Geofluids, 2019)
This study presents the results of gas flux measurements of cold, mantle-derived CO2 release at the Bubl'ak mofette field (BMF), located inside of the N-S directed Poč'atky Plesn'a fault zone (PPFZ). The PPFZ is presently seismically active, located in the eastern part of the Cheb Basin, western Eger Rift, Central Europe. The goal of the work was to identify the linkage between tectonics and gas flux. The investigated area has a size of 0,43 km2 in which 1.115 locations have been measured. Besides classical soil CO2 gas flux measurements using the closed chamber method (West Systems), drone-based orthophotos were used in combination with knowledge of plant zonation to find zones of high degassing in the agriculturally unused part of the BMF. The highest observed soil CO2 gas flux is 177.926,17 g m-2 d-1, and the lowest is 0,28 g m-2 d-1. Three statistical methods were used for the calculation of the gas flux: arithmetic mean, kriging, and trans-Gaussian kriging. The average CO2 soil degassing of the BMF is 30 t d-1 for an area of 0,43 km2. Since the CO2 soil degassing of the Hartoušov mofette field (HMF) amounts to 23 t d-1 for an area of 0,35 km2, the average dry degassing values of the BMF and HMF are in the same magnitude of order. The amount of CO2 flux from wet mofettes is 3 t d-1 for the BMF and 0,6 t d-1 for the HMF. It was found that the degassing in the BMF and HMF is not in accordance with the pull-apart basin interpretation, based on the direction of degassing as well as topography and sediment fill of the suggested basins. En-echelon faults inside of the PPFZ act as fluid channels to depth (CO2 conduits). These structures inside the PPFZ show beginning faulting and act as tectonic control of CO2 degassing. © 2019 Horst K{ampf et al.
Keywords: Cheb Basin; Czech Republic; Karlovarsky; carbon dioxide; carbon emission; degassing; flux measurement; rift zone; tectonics

Occurrence of clastic injectites in the oligocene strata of the carpathians and their significance in unravelling the paleogene and neogene evolution of the Carpathian orogeny (Poland, Ukraine and Romania) - Jankowski, L.; Wysocka, A. (Geological Quarterly, 2019)
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.
cited By 8

Paleoenvironmental Significance of Clay-sized Detrital Minerals of Late Cenozoic Sediments from the Lake Qinghai, China - Zeng, M.; Song, Y.; Sheng, Y. (Acta Geologica Sinica (English Edition), 2019)
cited By 0
Keywords: Cenozoic; clay mineral; detritus; lacustrine deposit; paleoclimate; paleoenvironment; sediment chemistry; China; Qinghai; Qinghai Lake

Ocean drilling perspectives on meteorite impacts - Lowery, C.M.; Morgan, J.V.; Gulick, S.P.S.; Bralower, T.J.; Christeson, G.L.; Chenot, E.; Claeys, P.; Cockell, C.; Coolen, M.J.L.; Ferrière, L.; Gebhardt, C.; Goto, K.; et al. (Oceanography, 2019)
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 Yucat'an 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 Yucat'an 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.
cited By 4

Operational report for the 2017 Surtsey underwater volcanic system for thermophiles, alteration processes and INnovative concretes (SUSTAIN) drilling project at Surtsey volcano, Iceland - Weisenberger, Tobias Bj{orn; Gudmundsson, Magn'us Tumi; Jackson, Marie Dolores; Gorny, Carolyn F; T{urke, Andreas; Kleine, Barbara Irene; Marshall, Beau; Jørgensen, Steffen Leth; Marteinsson, Vigg'o Th'or; Stef'ansson, Andri; et al. (GFZ German Research Centre for Geosciences, 2019)

Organic-rich source rock characterization and evaluation of the Cretaceous Qingshankou Formation: results from geophysical logs of the second scientific drilling borehole in the Songliao Basin, NE China - Zhang, X.; Zou, C.; Zhao, J.; Li, N.; Zhang, S.; Kouamelan, K.S.; Xiao, L.; Ma, H.; Niu, Y. (Geosciences Journal, 2019)
The second continental scientific drilling (SKII east) borehole in the Songliao Basin has been planned to be the deepest borehole to drill through the Cretaceous continental strata under the framework of the International Continental Scientific Drilling Program (ICDP) up to date. This borehole was designed not only to explore the potential relationships between dinosaur extinction and climate environment during the Cretaceous but also to achieve new breakthroughs in oil and gas exploration. The high hydrocarbon (oil and gas) potential of a source rock is highly dependent on its organic content. We used geophysical log data of Borehole SKII east to evaluate the organic content of organic-rich source rock. In the period of the first member in the Qingshankou Formation (K2qn1) from the study area, high accommodation space and anoxic environment could promote organic matter deposition. Firstly, based on geological information and abundant geophysical log data, the basic geophysical characteristics (including petrophysical, lithological, mineralogical, and sedimentary properties) of the Qingshankou Formation in Borehole SKII east were studied. Secondly, geophysical log response characteristics (including resistivity, porosity, radioactivity, mineral and element) of organic-rich source rocks were analyzed. Thirdly, we tried to obtain suitable methods to predict total organic carbon (TOC) content of the target formation with geophysical log data. The laboratorymeasured TOC values of core samples from Borehole SKI south were used to make calibrations with calculated TOC values from geophysical logs. Results from improved ΔlogR technique and Dual_Vsh method are consistent, and indicate that these two methods are effective in this formation. The calculated TOC values from these two methods are relatively desirable, and show that the organic-rich source rocks with high TOC content occurred in the K2qn1 (1646.00 1669.00 m). The highest TOC content can reach 9.15%. The bed thicknesses of organic-rich source rocks are totally up to 7.88 m. These organic-rich source rocks can be considered as excellent. This study demonstrated that improve ΔlogR technique can be applied to evaluate source rocks in the formations without maturity data, and the new method Dual_Vsh is also valid in the Qingshankou Formation. The organic-rich source rock evaluation results could promote further exploration and development of oil and gas resources in the upper Cretaceous formations, Songliao Basin. © 2019, The Association of Korean Geoscience Societies and Springer-Verlag GmbH Germany, part of Springer Nature.
cited By 4

Overview of modern atmospheric patterns controlling rainfall and floods into the Dead Sea: Implications for the lake's sedimentology and paleohydrology - Armon, Moshe; Morin, Efrat; Enzel, Yehouda (Quaternary Science Reviews, 2019)

Oxide gabbro intrusions of the dike-gabbro transition, Hole GT3A, Oman Drilling Project. - Jesus, Ana P; Koepke, Juergen; Mata, João; et al. (Geophysical Research Abstracts, 2019)

Paleoenvironmental and paleoclimatic variations around Lake Van (Eastern Turkey) recorded by sedimentary source specific biomarkers 250 –130 ka (MIS7 and MIS6) - Guillemot, T.; Stockhecke, M.; Bechtel, A.; Ladd, S.N.; Nelson, D.B.; Schubert, C.J. (Quaternary Science Reviews, 2019)

Recordings of Fast Paleomagnetic Reversals in a 1.2 Ma Greigite-Rich Sediment Archive From Lake Ohrid, Balkans - Just, J.; Sagnotti, L.; Nowaczyk, N.R.; Francke, A.; Wagner, B. (Journal of Geophysical Research: Solid Earth, 2019)

Tethyan anhydrite preserved in the lower crust of the Samail ophiolite: Evidence from Oman Drilling Project Holes GT1A and 2A. - Teagle, Damon; Cooper, Matthew; Harris, Michelle; Crispini, Laura; Kelemen, Peter; et al. (Geophysical Research Abstracts, 2019)

Refining the interpretation of lacustrine carbonate isotope records: Implications of a mineralogy-specific Lake Van case study - McCormack, J.; Nehrke, G.; J{ons, N.; Immenhauser, A.; Kwiecien, O. (Chemical Geology, 2019)
Oxygen and carbon isotope (δ 18 O and δ 13 C) data from bulk carbonates are widely applied proxies for temperature, the precipitation/evaporation ratio and productivity in lacustrine palaeohydrology and palaeoclimatology. In case of the terminal and alkaline Lake Van, however, previous studies have shown that bulk oxygen isotope compositions are in disagreement with other proxies when interpreted in a conventional manner. Similarly, the reports on the nature and the timing and site of carbonate precipitation in Lake Van are inconsistent. This study provides evidence on the mineralogy (X-ray powder diffraction analysis, scanning electron microscope imaging, confocal Raman microscopy, electron microprobe analysis) and isotope composition (δ 18 O and δ 13 C) of non-skeletal carbonate minerals in a Lake Van sedimentary profile spanning the last ca. 150 kyr. Carbonate phases present in the sediment include aragonite, low-Mg calcite, and calcian dolomite. Dolomite forms as an early diagenetic phase and occurs episodically in high concentrations driving the bulk isotope record towards the higher dolomite δ 18 O and varying δ 13 C values. Aragonite and low-Mg calcite precipitate in the surface water and are present in the sediments in varying amounts (relative aragonite to calcite content for dolomite-poor samples Ar/(Ar + Cc) of 93 to 41 wt%). In an attempt to explain this variation, we revised a precipitation model based on annually laminated sediments containing both aragonite and calcite spatially separated in light and dark coloured laminae, respectively. According to our model, spring calcite precipitation, under close-to-freshwater conditions, is followed by evapoconcentration-driven aragonite precipitation in late summer. The precipitation of these carbonate polymorphs from chemically differing surface waters (i.e. freshwater-influenced and evapoconcentrated) leads to distinctly different oxygen and carbon isotope signatures between sedimentary penecontemporaneous aragonite and calcite. The δ 18 O and δ 13 C values of aragonite relative to calcite are significantly higher by several per mille than inferred from aragonite-calcite fractionation factors alone, suggesting that the generalised assumption of sedimentary coeval calcite and aragonite precipitating from water with the same isotopic composition is flawed. The here proposed revised hydrologically-separated carbonate precipitation model is not only taking (i) differences in the isotopic fractionation between carbonate minerals into account, but also (ii) considering the hydrological conditions and the processes favouring the precipitation of a given mineral and ultimately controlling its isotopic composition. If mixed mineralogies are present, this mineralogy-specific approach has the potential of refining environmental reconstructions and reconciling apparently equivocal interpretations of different proxy records. © 2019 The Authors
cited By 18
Keywords: Calcite; Carbon; Carbonation; Electron probe microanalysis; Isotopes; Lakes; Oxygen; Refining; Repair; Scanning electron microscopy; Sedimentology; Sediments; Water; X ray powder diffraction; Carbonate precipitation; Confocal Raman microscopy; Diagenetics; Environmental reconstruction; Isotopic fractionations; Lake vans; Oxygen isotope composition; Palaeoenvironmental reconstruction; Carbonate minerals; aragonite; calcite; carbon isotope; carbonate; diagenesis; dolomite; isotopic composition; lacustrine deposit; mineralogy; oxygen isotope; paleoenvironment; reconstruction; sediment chemistry; Lake Van; Turkey

U-Pb memory behavior in Chicxulub's peak ring – Applying U-Pb depth profiling to shocked zircon - Rasmussen, C.; Stockli, D.F.; Ross, C.H.; Pickersgill, A.; Gulick, S.P.; Schmieder, M.; Christeson, G.L.; Wittmann, A.; Kring, D.A.; Morgan, J.V.; Party, IODP-ICDP Expedition 364 Science (Chemical Geology, 2019)
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.
cited By 13

The gulf of Mexico sedimentary basin: Depositional evolution and petroleum applications - Snedden, J.W.; Galloway, W.E. (The Gulf of Mexico Sedimentary Basin: Depositional Evolution and Petroleum Applications, 2019)
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.
cited By 47

The Marine Isotope Stage 12 pollen record from Lake Ohrid (SE Europe): Investigating short-term climate change under extreme glacial conditions - Koutsodendris, Andreas; Kousis, Ilias; Peyron, Odile; Wagner, Bernd; Pross, J{org (Quaternary Science Reviews, 2019)
Characterised by a maximum expansion of continental ice sheets in the Northern Hemisphere, Marine Isotope Stage (MIS) 12 (∼478 –424 ka before present) was one of the strongest glacials of the Quaternary. Because the information currently available on MIS 12 is predominantly derived from marine records, the imprint of this extreme glaciation on the terrestrial realm – and notably on terrestrial ecosystems – has remained poorly constrained. Here we present a new, centennial-scale-resolution pollen record from Lake Ohrid (Balkan Peninsula, SE Europe) augmented by pollen-based quantitative temperature and precipitation estimates. Our dataset, which spans the period from 488 to 420 ka, shows that the forest cover around Lake Ohrid decreased substantially over the course of MIS 12; this decrease was associated with a gradual lowering of winter and mean annual temperatures (and to a lesser extent of summer temperatures) as well as mean annual precipitation. Superimposed on this long-term development, abrupt changes in regional forest cover indicate a pronounced millennial-scale climate variability that bears strong resemblance to the interstadial and stadial events of the Last Glacial. This variability is expressed by repeated high-amplitude forest expansions and contractions around Lake Ohrid during MIS 12c and the oldest part of 12b substage (i.e., from ∼477 to 448 ka). The forest oscillations can be correlated to previously documented episodes of surface-water variability and ice-rafted debris deposition in the North Atlantic. This pattern suggests a coupling between the climatically forced tree-population changes in SE Europe and the variability of the Atlantic Meridional Ocean Circulation during MIS 12c and partially 12b on millennial timescales. In contrast, the youngest part of MIS 12b and MIS 12a (i.e., from ∼448 to 424 ka) lack high-amplitude forest expansions and contractions around Lake Ohrid. Comparison with sea-level reconstructions for MIS 12 suggests that millennial-scale vegetation variability in Lake Ohrid was strongest when sea level was between 30 and 100 m lower than today, whereas it was absent when sea level was lower than 100 m relative to the present. © 2019 Elsevier Ltd
Keywords: Balkans; Lake Ohrid; Mediterranean Sea; Mediterranean Sea (East); Expansion; Forestry; Glacial geology; Isotopes; Lakes; Sea level; Vegetation; Climate variability; Eastern Mediterranean; Lake Ohrid; Middle Pleistocene; Quantitative climate estimates; Vegetation dynamics; climate change; climate variation; forest cover; glaciation; ice sheet; ice-rafted debris; interstadial; Last Glacial; marine isotope stage; meridional circulation; Pleistocene; sea level; terrestrial ecosystem; vegetation dynamics; Climate change

The Oman Drilling Project–Overview and Initial Results. - Matter, Juerg; Kelemen, Peter; Teagle, Damon; Coggon, Jude (Geophysical Research Abstracts, 2019)

The sedimentary origin of black and white banded cherts of the Buck Reef, Barberton, South Africa - Ledevin, Morgane; Arndt, Nicholas; Chauvel, Catherine; Jaillard, Etienne; Simionovici, Alexandre (Geosciences (Switzerland), 2019)
The Buck Reef is a 250 –400 m thick sequence of banded black and white (B &W) cherts deposited ca. 3416 Ma ago in a shallow basin. We provide field, petrological and geochemical constraints on the chert-forming process and the origin of the banding. White layers consist of nearly pure microquartz, while black layers are mixed with detrital carbonaceous matter, quartz grains and carbonaceous microlaminae, interpreted as remnants of microbial mats. The circulation of Si-rich fluid is recorded by abundant chert veins and pervasive silicification. However, the high purity of the white layers, their lack of internal structures and extremely low Al, Ti and high-field-strength elements preclude an origin by silicification of sedimentary or volcanic precursors. Moreover, their reworking at the surface into slab conglomerates, and sediment-like contacts with black layers rule out a diagenetic origin. We propose a new model whereby the white layers were periodically deposited as precipitates of pure silica; and the micro-layering within the black layers formed by annual temperature fluctuations, favouring microbial activity in summer and inorganic silica precipitation in winter. Outcrop-scale alternation of B &W layers was associated with major, thousand-year-long climate events: white cherts represent massive silica precipitation resulting from changes in ocean circulation and temperature during cold intervals. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.

The status of exploitation techniques of natural gas hydrate - Yang, L.; Liu, Y.; Zhang, H.; Xiao, B.; Guo, X.; Wei, R.; Xu, L.; Sun, L.; Yu, B.; Leng, S.; Li, Y. (Chinese Journal of Chemical Engineering, 2019)
Natural gas hydrate (NGH) has been widely considered as an alternative form of energy with huge potential, due to its tremendous reserves, cleanness and high energy density. Several countries involving Japan, Canada, India and China have launched national projects on the exploration and exploitation of gas hydrate resources. At the beginning of this century, an early trial production of hydrate resources was carried out in Mallik permafrost region, Canada. Japan has conducted the first field test from marine hydrates in 2013, followed by another trial in 2017. China also made its first trial production from marine hydrate sediments in 2017. Yet the low production efficiency, ice/hydrate regeneration, and sand problems are still commonly encountered; the worldwide progress is far before commercialization. Up to now, many gas production techniques have been proposed, and a few of them have been adopted in the field production tests. Nevertheless, hardly any method appears really promising; each of them shows limitations at certain conditions. Therefore, further efforts should be made on the economic efficiency as well as sustainability and environmental impacts. In this paper, the investigations on NGH exploitation techniques are comprehensively reviewed, involving depressurization, thermal stimulation, chemical inhibitor injection, CO2 –CH4 exchange, their combinations, and some novel techniques. The behavior of each method and its further potential in the field test are discussed. The advantages and limitations of laboratory studies are also analyzed. The work could give some guidance in the future formulation of exploitation scheme and evaluation of gas production behavior from hydrate reservoirs. © 2019 Elsevier B.V.
cited By 72
Keywords: Carbon dioxide; Environmental impact; Gas industry; Gases; Hydration; Ice problems; Natural gas; Petroleum reservoir evaluation; Production; Proven reserves; Sustainable development; CO2 exchange; Depressurizations; Exploitation techniques; Exploration and exploitation; Gas production technique; Production efficiency; Production techniques; Thermal stimulation; Gas hydrates

The utilization of integrated geophysical profiles to reveal the basement geology and geophysical characteristics of the Songliao Basin: A case study of the profile of Well SK-2; [综合物探剖面揭示松辽盆地基底地质与地球物理特征-以过松科二井剖面为例] - Wang, Tianqi; Han, Jiangtao; Hou, Hesheng; Liu, Wenyu; Guan, Yanwu; Ma, Guoqing; Zhou, Zikun (Geology in China, 2019)
收稿日期：2019-04-03；改回日期：2019-09-16 基金项目：中国地质调查局地质调查项目（DD20160207）；国家重点研发专项（2017YFC0601305）及国家自然科学基金青年科学基金项目(41504076)联合资助。作者简介：王天琪，女，1994年生，硕士生，主要从事综合地球物理调查研究工作；E-mail：641149482 @qq.com。通讯作者：韩江涛，男，1982年生，副教授，主要从事深部地球物理勘查工作；E-mail：hanjt@jlu.edu.cn。Abstract: Songliao Basin is a Meso-Cenozoic continental sedimentary basin in Northeast China. Based on a detailed analysis of the Paleozoic stratigraphic characteristics, sedimentary environment and tectonic evolution in Northeast China, the authors conducted the interpretation of the comprehensive geophysical data across Well SK- 2 to investigate the properties and geophysical characteristics of the basement in this paper. On the SN profile, the authors have found some phenomena: the Bouguer gravity anomaly in Well SK-2 is high in the middle and low on both sides; the magnetic anomaly shows a negative correlation with gravity anomaly; magnetotelluric properties are characterized by partial layers and high-low resistance crossover in the shallow part and partial regions in the deep part. On the EW profile, the gravity anomaly curve has the trend high in the west and low in the east; the magnetic anomaly curve is“bowl-shaped”; there exists a high resistance structure compared with features of the SN-trending profile. Combining geophysical characteristics with lithofacies palaeogeography, the authors have reached the following conclusions: 1. From the Late Carboniferous to Late Permian in the Upper Paleozoic, there were many sedimentary environments such as shallow marine facies, continental facies, rivers and lakes. The corresponding lithologic combinations had different physical characteristics; 2. The geomagnetic characteristics of the gravity, magnetic method and magnetotelluric sounding's results reveal that the basement of the study area is mainly composed of mudstone, marble and intrusive rocks, and the burial depth of the roof of the basement is about 7km. The base of the study area is formed by the Upper Paleozoic and intrusive rocks. 3. The location and orientation of the Binzhou fault zone, the Sunwu-Shuangliao fault zone, the Helen-Renmin fault zone and the deep fault system are identified. The fault structures are mainly dominated by SN and EW trending structures. They are important components of the Paleozoic structural skeleton and control the migration and storage of deep oil and gas. © 2019 Editorial Board of Geology in China. All rights reserved.

Understanding volcanic facies in the subsurface: A combined core, wireline logging and image log data set from the PTA2 and KMA1 boreholes, Big Island, Hawaii - Jerram, D.A.; Millett, J.M.; Thomas, D.; Planke, S.; Haskins, E.; Lautze, N.; Pierdominici, S. (Scientific Drilling, 2019)
To help understand volcanic facies in the subsurface, data sets that enable detailed comparisons between down-hole geophysical data and cored volcanic intervals are critical. However, in many cases, the collection of extended core intervals within volcanic sequences is rare and often incomplete due to challenging coring conditions. In this contribution we outline and provide initial results from borehole logging operations within two fully cored lava-dominated borehole sequences, PTA2 and KMA1, on the Big Island of Hawai`i. Data for spectral gamma, magnetic susceptibility, dipmeter resistivity, sonic, total magnetic field, temperature and televiewer wireline logs were successfully acquired for the open hole interval ca. 889 m to 1567 m within the PTA2 borehole. Spectral gamma was also collected from inside the casing of both wells, extending the coverage for PTA2 to the surface and covering the interval from ca. 300 to 1200 m for KMA1. High-quality core material was available for both boreholes with almost complete recovery which enabled high-resolution core-to-log integration. Gamma data are generally low commonly in the range ca. 7-20 gAPI but are shown to increase up to API of ca. 60 with some intrusions and with increases in hawaiite compositions in the upper part of PTA2. Velocity data are more variable due to alteration within porous volcanic facies than with burial depth, with a general degrease down-hole. The high-resolution televiewer data have been compared directly to the core, enabling a comprehensive analysis of the variations in the televiewer responses. This has enabled the identification of key features including individual vesicles, vesicle segregations, strained vesicles, chilled margins, rubble zones, intrusive contacts and pāhoehoe lobe morphologies, which can be confidently matched between the televiewer data and the full diameter core. The data set and results of this study include findings which should enable improved borehole facies analysis through volcanic sequences in the future, especially where down-borehole data and images but no core are available. © Author(s) 2019.
cited By 17
Keywords: Coremaking; Image enhancement; Magnetic susceptibility; Thermal logging; Volcanoes; Borehole logging; Comprehensive analysis; Facies analysis; Full diameter core; Geophysical data; High resolution; Volcanic facies; Wireline logging; Boreholes

The evolution of latitudinal temperature gradients from the latest Cretaceous through the Present - Zhang, L.; Hay, W.W.; Wang, C.; Gu, X. (Earth-Science Reviews, 2019)
Latitudinal temperature gradients are a defining characteristic of the climate system. Using thermometric indicators, including δ18O, plant and animal fossils, glycerol dialkyl glycerol tetraether (GDGT) proxies, and clumped isotope estimates, we document marine and terrestrial temperature gradients for the latest Cretaceous, Late Paleocene-Early Eocene, Early Oligocene, Pliocene, and Recent. The changes in gradients reflect the transition greenhouse to icehouse conditions. The evolution of latitudinal temperature gradients in marine and terrestrial realms are similar but has some distinctive differences. Marine temperatures are generally warmer than those on land. Except for the Late Paleocene-Early Eocene, the marine records show distinct inflection points at 30° and 50° latitude indicating the existence of frontal systems in the ocean. Except for the Late Paleocene-Early Eocene, the marine records show an increasingly steeper trend, from latest Cretaceous through Recent, being most pronounced after the Early Oligocene greenhouse-icehouse transition. This trend reflects the increasing intensity of high-latitude and polar cooling as the icehouse state developed. During the Late Paleocene-Early Eocene the oceans were characterized by slightly warmer tropics and much warmer higher latitudes than at present. The continents have generally had tropical temperatures like those of today, varying by <5 °C. Higher latitude temperatures cooled during the latest Cretaceous, became much warmer during the Late Paleocene-Early Eocene, then cooled during the Early Oligocene and have become increasingly colder since then. The results suggest that there is a climate thermostat mechanism, probably related to greenhouse gas concentrations, that ameliorates tropical warming by redistributing warmth to the poles in the greenhouse world. That mechanism broke down as greenhouse gas concentrations declined resulting in the conversion from greenhouse to icehouse conditions. © 2019 Elsevier B.V.
cited By 28
Keywords: climate variation; Cretaceous; glacial-interglacial cycle; greenhouse gas; Oligocene; paleoceanography; Paleocene-Eocene boundary; paleoclimate; Pliocene; temperature gradient; thermometry; Animalia

Varves of the Dead Sea sedimentary record - Ben Dor, Y.; Neugebauer, I.; Enzel, Y.; Schwab, M.J.; Tjallingii, R.; Erel, Y.; Brauer, A. (Quaternary Science Reviews, 2019)
The sedimentary record of the Dead Sea provides an exceptional high-resolution archive of past climate changes in the drought-sensitive eastern Mediterranean-Levant, a key region for the development of humankind at the boundary of global climate belts. Moreover, it is the only deep hypersaline lake known to have deposited long sequences of finely laminated, annually deposited sediments (i.e. varves) of varied compositions, including aragonite, gypsum, halite and clastic sediments. Vast efforts have been made over the years to decipher the environmental information stored in these evaporitic-clastic sequences spanning from the Pleistocene Lake Amora to the Holocene Dead Sea. A general characterisation of sediment facies has been derived from exposed sediment sections, as well as from shallow- and deep-water sediment cores. During high lake stands and episodes of positive water budget, mostly during glacial times, alternating aragonite and detritus laminae (aad’ facies) were accumulated, whereas during low lake stands and droughts, prevailing during interglacials, laminated detritus (ld’ facies) and laminated halite (lh’ facies) dominate the sequence. In this paper, we (i) review the three types of laminated sediments of the Dead Sea sedimentary record (aad’, ld’ and lh’ facies), (ii) discuss their modes of formation, deposition and accumulation, and their interpretation as varves, and (iii) illustrate how Dead Sea varves are utilized for palaeoclimate reconstructions and for establishing floating chronologies. © 2019 Elsevier Ltd
cited By 26
Keywords: Budget control; Carbonate minerals; Chloride minerals; Climate change; Deposition; Drought; Lakes; Sedimentology; Sodium chloride; Deep drilling; Evaporitic varves; Hypersaline lakes; Lacustrine sediments; Palaeoclimate reconstruction; Varve chronologies; Sediments; chronology; deep drilling; drought; global climate; historical record; hypersaline environment; lacustrine deposit; marine sediment; paleoclimate; Pleistocene; reconstruction; sediment core; varve; water budget; Dead Sea; Levant; Mediterranean Region

Vertical distribution characteristics of light hydrocarbon components in Well SK-2 and its implications for deep oil and gas [松科二井轻烃组分垂向分布特征及其对深部油气的指示] - Hou, H.; Zhang, J.; Wang, W.; Yang, L.; Xiao, G.; Fu, W.; Miao, H.; Xu, S.; Zeng, Q.; Liu, X.; Wang, D.; Zhang, W. (Geology in China, 2019)
With the maturation of oil and gas exploration and development in Songliao basin, it is urgent to expand strategic replacement areas for oil and gas storage and production. In this task，deep oil and gas seem to be an important direction. Roof gas logging with continuous sampling in the whole well section of Well SK-2 obtained 6042 groups of light hydrocarbon composition data containing 103 monomers，and fully demonstrated vertical variation characteristics of light hydrocarbon components in the deep part of Well SK-2，which shows obvious segmentation. As a whole, it can be divided into 6 sections: section I (470-1000 m in well section), which has a small peak area, a small number of peak outfalls, and a low heavy hydrocarbon content, showing the characteristics of shallow and low-mature oil and gas; Section II (well section 1000-2800 m) has a large peak area, a large number of peaks and a high heavy hydrocarbon content. It is a mature type I source rock and a conventional oil and gas section dominated by oil generation; Section III (2800-3320 m in well section) has fewer and scattered peaks, low content of heavy hydrocarbon and no hydrocarbon source rocks, which are characteristic of reservoirs; Section IV (3320- 5940 m in well section) is the upper unconventional gas section of Shahezi Formation, with a large peak area and a large number of peak outputs, high content of heavy hydrocarbon, being Type III source rocks with large thickness in the maturation - over-maturation stage, and sandstone interbeds can form various types of unconventional natural gas, suggesting an important section for future exploration; Section V (5940-6200 m in well section) is the lower part of Shahezi Formation and Huoshiling Formation, and the peak area and peak number of roof gas are scattered within the section which is considered to be in the stage of over-maturation; Section VI (6200-7108 m in well section) is volcanic rock and basement segment, and the peak area and number of peaks are generally low. However, the peak area of top gas in 7000-7100 m well segment shows that the light hydrocarbon parameters are different from those of section V, and it is inferred that there may be gas sources of type II-III organic matter in the deep part. These characteristics show that the vertical distribution of light hydrocarbon components reflects the different characteristics among Jurassic, Cretaceous and the basal formations in oil and gas formation, maturation, gas content and oil and gas sources. The results obtained by the authors reveal the potential of deep unconventional gas resource, and provide an important foundation for Songliao Basin's exploration shift from conventional oil and gas exploration and tight conglomerate gas exploration at the edge of fault depression to deep trough zone for the exploration and expansion of unconventional natural gas. © 2019 Editorial Board of Geology in China. All rights reserved.
cited By 1

Volcanic stratigraphy and age model of the Kimama deep borehole (Project Hotspot): Evidence for 5.8 million years of continuous basalt volcanism, central Snake River Plain, Idaho - Potter, Katherine E.; Champion, Duane E.; Duncan, Robert A.; Shervais, John W. (Geosphere, 2019)
The Snake River Plain of central Idaho represents the world's best example of a mantle hotspot track impinging upon continental crust and provides a record of bimodal volcanism extending over 12 Ma to the present. Project Hotspot recovered almost 2 km of continuous drill core from the Kimama borehole, located in central Idaho on the axial volcanic zone. The Kimama drill core represents the most complete record of mafic volcanism along the Yellowstone-Snake River Plain hotspot track. A total of 432 basalt flow units, representing 183 basalt flows, 78 basalt flow groups, and 34 super groups, along with 42 sediment interbeds are recognized using volcanic facies observations, stratigraphic relationships, borehole geophysical logs, and paleosecular variation in magnetostratigraphy. Rhyolite and other non-basaltic volcanic materials were not encountered in the drill core. Ages for six basalt lava flows were determined by 40Ar/39 using incremental heating experiments. Paleomagnetic inclination was measured on over 1200 samples collected at roughly 2-m-depth intervals, yielding mean values of paleosecular variation between ±50° to ±70° in Kimama flow groups, close to the expected 61° axial dipole average for the Kimama borehole location. Twenty-three magnetic reversals were identified and correlated to dated geomagnetic chrons and subchrons and compared with the 40Ar/39 radiometric ages. A linear fit to 40Ar/39Ar dates, geomagnetic chron and subchron boundaries, and volcanogenic zircon U-Pb ages defines a mean accumulation rate of 320 m/m.y. and extrapolates to a bottom hole age of 6.3 Ma. Average thicknesses of lithologic units increase from 2.7 m (sediment), 4 m (flow units), 10 m (flows), 23 m (flow groups), to 53 m (super groups). On average, one lava flow inundated the Kimama borehole location every 33 k.y. Intercalated sediments, ranging from 0.06 to 24.5 m thick, make up roughly 6% of the drill core and indicate lulls in local volcanic activity that may have lasted up to 77 k.y. Neutron and gamma-ray logs supplement observations from the drill cores: neutron logs document individual flow units through the contrast between massive flow interiors and more porous flow surfaces, and gamma-ray logs document the depth and thickness of sedimentary interbeds and high-K-Fe basalts. The 5.8 m.y. duration of basaltic volcanism in the Kimama drill core implies a steady rate of volcanism, indicating a relatively stable rate of mantle upflow along the lithosphere-mantle boundary in the wake of Yellowstone-Snake River Plain plume volcanism. © 2019 The Authors.
Keywords: Idaho; Snake River Plain; United States; Basalt; Binary alloys; Boreholes; Boring; Drills; Gamma rays; Geomagnetism; Infill drilling; Lead alloys; Neutron logging; Plastic flow; Rivers; Sediments; Silicate minerals; Stratigraphy; Uranium alloys; Volcanoes; Zircon; Accumulation rates; Basaltic volcanism; Heating experiment; Lithosphere mantle; Magnetostratigraphy; Paleosecular variations; Snake river plains; Volcanic activities; basalt; borehole; continental crust; facies; lava flow; lithology; magnetic reversal; magnetostratigraphy; paleomagnetism; volcanism; Core drilling

δ13C records from fish fossils as paleo-indicators of ecosystem response to lake levels in the Plio-Pleistocene lakes of Tugen Hills, Kenya - Billingsley, Anne L.; Reinthal, Peter; Dettman, David L.; Kingston, John D.; Deino, Alan L.; Ortiz, Kevin; Mohler, Benjamin; Cohen, Andrew S. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2019)
The carbon isotopic ratios of organic matter in fish fossils from diatomites and other lake beds in the HSPDP drill core from Tugen Hills, Kenya (2.56 –3.29 Ma) reflect trophic resource uses, and can indicate the dietary habitats of fish in the paleolake. This information offers insight into how fish communities responded to lake-level fluctuations during the Plio-Pleistocene in the East African Rift Valley. We have compared this record with fish fossil isotopes from both a previously published study of a Lake Malawi drill core (139 ka –present) and core top (modern ca 1978) samples collected at the water/sediment boundary from Lake Turkana (Kenya) of known environmental provenance. Both the Lake Malawi drill core fossils (−7.2‰ to −27.5‰ VPDB) and modern Lake Turkana samples (−16‰ to −24.6‰ VPDB) have δ13C values indicating a mix of near-shore and deep-water pelagic species. In contrast, the δ13C values for the Tugen Hills core fossils vary only between −20‰ and −27‰ VPDB. The absence of δ13C values greater than −19‰, suggests none of these fossils are derived from near-shore benthic habitats. The lack of shallow water, benthic lacustrine fish fossils through the Tugen Hills lake cycles may indicate that the rate of change from low-lake stands to deeper lake phases was very rapid, and shallow water communities were not established for long enough to leave a fish fossil record at the core site. These results strongly suggest that lake level responses to climate variability in the Baringo basin of the East African Rift were very abrupt during the Plio-Pleistocene transition. © 2019 Elsevier B.V.
Keywords: Baringo; East African Lakes; East African Lakes; East African Rift; Kenya; Lake Malawi; Lake Turkana; Tugen Hills; carbon isotope; climate variation; ecosystem response; fish; fossil record; habitat type; lake level; organic matter; paleoclimate; paleoecology; paleoenvironment; Pliocene-Pleistocene boundary; shallow water

深井复合钻柱技术在特深科学钻探中的应用探讨 - 李立鑫; 张丰琰; 张恒春; 汪伟; 张毅; 胡郁乐 (中国地质, 2019)

Middle to Late Pleistocene lake-level fluctuations of Lake El'gygytgyn, far-east Russian Arctic - Fedorov, Grigory; Andreev, Andrei A.; Raschke, Elena; Wennrich, Volker; Schwamborn, Georg; Glushkova, Olga Y.; Juschus, Olaf; Zander, Anja; Melles, Martin (Boreas, 2019)

The first day of the Cenozoic - Gulick, S.P.S.; Bralower, T.J.; Orm{o, J.; Grice, K.; Schaefer, B.; Lyons, S.; Freeman, K.H.; Morgan, J.V.; Artemieva, N.; Kaskes, P.; De Graaff, S.J.; Whalen, M.T.; et al. (Proceedings of the National Academy of Sciences of the United States of America, 2019)
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.
cited By 79

Tephra geochemistry from Lake Ohrid (Macedonia/Albania) sediment core ICDP5045-1 - Francke, Alexander; Dosseto, Anthony; Panagiotopoulos, Konstantinos; Leicher, Niklas; Lacey, Jack H; Kyrikou, Styliani; Wagner, Bernd; Zanchetta, Giovanni; Kouli, Katerina; Leng, Melanie J (PANGAEA, 2019)
Geochemical finger print data (in wt. %) of individual glass shards from 3 three previously described cryptotephra layer in the Late Glacial to Holocene sediments of the DEEP site sequence. FeO? is reported for both Fe^2? and Fe^3? (University of Cologne, Germany , University of Pisa, Italy).
In supplement to: Francke, A et al. (2019): Sediment residence time reveals Holocene shift from climatic to vegetation control on catchment erosion in the Balkans. Global and Planetary Change, 177, 186-200, https://doi.org/10.1016/j.gloplacha.2019.04.005

Refining the Late Quaternary tephrochronology for southern South America using the Laguna Potrok Aike sedimentary record - Smith, Rebecca E.; Smith, Victoria C.; Fontijn, Karen; Wastegård, Stefan; Zolitschka, Bernd; Ohlendorf, Christian; Stern, Charles; Mayr, Christoph (Quaternary Science Reviews, 2019)
This paper presents a detailed record of volcanism extending back to ∼80 kyr BP for southern South America using the sediments of Laguna Potrok Aike (ICDP expedition 5022; Potrok Aike Maar Lake Sediment Archive Drilling Project - PASADO). Our analysis of tephra includes the morphology of glass, the mineral componentry, the abundance of glass-shards, lithics and minerals, and the composition of glass-shards in relation to the stratigraphy. Firstly, a reference database of glass compositions of known eruptions in the region was created to enable robust tephra correlations. This includes data published elsewhere, in addition to new glass-shard analyses of proximal tephra deposits from Hudson (eruption units H1 and H2), Aguilera (A1), Reclus (R1, R2-3), Mt Burney (MB1, MB2, MBx, MB1910) and historical Lautaro/Viedma deposits. The analysis of the ninety-four tephra layers observed in the Laguna Potrok Aike sedimentary sequence reveals that twenty-five tephra deposits in the record are the result of primary fallout and are sourced from at least three different volcanoes in the Austral Andean Volcanic Zone (Mt Burney, Reclus, Lautaro/Viedma) and one in the southernmost Southern Volcanic Zone (Hudson). One new correlation to the widespread H1 eruption from Hudson volcano at 8.7 (8.6 –9.0) cal ka BP during the Quaternary is identified. The identification of sixty-five discrete deposits that were predominantly volcanic ashes (glass and minerals) with subtle characteristics of reworking (in addition to three likely reworked tephra, and one unknown layer) indicates that care must be taken in the analysis of both visible and invisible tephra layers to decipher their emplacement mechanisms. © 2019 The Authors
Keywords: Argentina; Laguna Potrok Aike; Patagonia; Santa Cruz [Argentina]; Southern Volcanic Zone; Deposits; Geochemistry; Glass; Minerals; Sedimentology; Stratigraphy; Lacustrine; PASADO; Patagonia; Quaternary; South America; Tephrochronology; Volcanic ash; emplacement; geochemistry; lacustrine environment; Quaternary; reworking; sediment chemistry; sedimentary sequence; stratigraphy; tephrochronology; volcanic ash; volcanic eruption; volcanism; volcano; Volcanoes

Seismic clustering in the Sea of Marmara: Implications for monitoring earthquake processes - Mart'inez-Garz'on, P.; Ben-Zion, Y.; Zaliapin, I.; Bohnhoff, M. (Tectonophysics, 2019)
Quantifying regional earthquake cluster style is essential for providing a context for studies of seismicity patterns and earthquake interactions. Here, we identify clusters of seismicity in the Sea of Marmara region of the North Anatolian Fault, NW Turkey, using a recently derived high-resolution seismicity catalog and the nearest-neighbor earthquake cluster approach. The detected earthquake clusters are utilized for (1) determining spatial distribution of mainshock and aftershock rates and estimating the proximity to failure on different fault segments, (2) identifying fault sections having earthquake repeaters, and (3) finding areas with enhanced foreshock activity. About 6%, 70% and 24% of the events are identified as foreshocks, mainshocks and aftershocks, respectively, with the largest concentration of aftershocks and foreshocks located along the Western High and the Cinarcik Fault, respectively. The method successfully identifies regions where previous studies reported earthquake repeaters as indicator for fault creep and suggests additional repeater areas in the Gulf of Gemlik. The largest proportion of mainshocks with associated foreshocks and aftershocks are along the Western High and Cinarcik Fault segments, potentially indicating that these segments are closer to failure and have increased susceptibility to seismic triggering. Continuing studies can contribute to monitoring possible preparation phase of a large (M > 7) earthquake in the Marmara region near the Istanbul Metropolitan region. © 2019 Elsevier B.V.
cited By 10
Keywords: Faulting; Earthquake dynamics; Earthquake process; Fault segmentation; Metropolitan regions; North Anatolian Fault; Regional earthquakes; Seismicity clusters; Seismicity pattern; Earthquakes; aftershock; cluster analysis; earthquake catalogue; earthquake event; earthquake mechanism; earthquake trigger; fault; foreshock; North Anatolian Fault; seismicity; Gulf of Gemlik; Istanbul [Istanbul (PRV)]; Istanbul [Turkey]; Sea of Marmara; Turkey

Remnants of paleoflora in impact melt rocks of the El'gygytgyn crater (Chukotka, Russia) - Gurov, E.P.; Permiakov, V.V.; Koeberl, C. (Meteoritics and Planetary Science, 2019)
Remnants of paleoflora were discovered in impact melt rocks from the El'gygytgyn crater, Chukotka, Russia. El'gygytgyn is a 3.58 Ma, 18 km diameter impact structure in Chukotka, northeastern Russia. A circular crater basin is surrounded by an uplifted rim. The crater floor is occupied by the El'gygytgyn Lake, 12 km in diameter, surrounded by lacustrine terraces up to 80 m in height. Impactites found at the El'gygytgyn crater include impact melt rocks, glass bombs, and shock metamorphosed volcanic rocks. Most impact melt rocks occur only in redeposited state in the terrace lake deposits. Floral remnants were discovered in impact melt rocks from various locations in the terrace deposits. The floral remnants include fragments of leaves, cell tissue, and undetermined organic matter that occur in vesicles within glassy melt rocks and impact melt breccias. After the discovery of floral remnants in impact melt breccias from upper Miocene strata in Argentina, and the description of floral imprints in the Dakhleh Glass of proposed impact origin in Egypt, the detection of paleoflora remnants in impact melt rocks of the El'gygytgyn structure is the first such occurrence in a confirmed impact crater on Earth. © 2019 The Authors. Meteoritics & Planetary Science published by Wiley Periodicals, Inc. on behalf of The Meteoritical Society (MET).
cited By 3

Research and application of while drilling temperature measurement technology under high temperature and high pressure in Well Songke-2; [松科二井高温高压随钻测温技术的应用研究] - Hu, Yule; Liu, Naipeng; Wang, Wei; Zhang, Hengchun (Geology in China, 2019)
Well Songke-2 is the deepest continental scientific drilling carried out by Asian countries. The logging temperature of Well Songke-2 Songke-2 was 241 °C after drilling for 38 hours, which created the highest well temperature application record of drilling engineering in China. The parameters of Well Songke-2 are mainly tested in two ways: one is integrated logging before casing, whereas the other is downhole parameter measurement while drilling which does not affect normal drilling work. Timely grasping the information such as the temperature while drilling plays a key supporting role in the adjustment of high temperature mud performance and the application of power tools. The authors carried out a series of researches on the problem of high temperature in Well Songke-2, and developed a storage type measurement while drilling instrument. The instrument was improved and designed through multiple rounds of research and finally it has been successfully applied to Well Songke-2. © 2019 Editorial Board of Geology in China. All rights reserved.

Rock-magnetic and paleomagnetic studies on late-Holocene sediments from Laguna Ch'altel (Patagonia, Argentina) - Palermo, Pedro; Irurzun, Mari'a A.; Gogorza, Claudia S.G.; Sinito, Ana M.; Ohlendorf, Christian; Zolitschka, Bernd (Journal of South American Earth Sciences, 2019)

Scientific drilling across the shoreline - Gulick, S.P.S.; Miller, K.; Kelemen, P.; Morgan, J.; Proust, J.-N.; Takazawa, E. (Oceanography, 2019)
Shorelines are ephemeral features, yet many science problems cross this ever-moving boundary and require sampling on both its dry and wet sides. The logistics of working on land and at sea are distinct, such that funding agencies in many countries divide their research programs at the shoreline. Similarly, scientific drilling is split between the International Ocean Discovery Program (IODP) in the ocean and the International Continental Scientific Drilling Program (ICDP) on land. Here, we discuss three examples of drilling projects that effectively coordinated activities between IODP and ICDP and highlight the need for increasing cooperation and coordination across the shoreline. We end by casting an eye toward the future of scientific drilling, where truly amphibious projects are now possible. © 2019 The Oceanography Society, Inc.
cited By 1

Scientific drilling of Lake Chalco, Basin of Mexico (MexiDrill) - Brown, E.T.; Caballero, M.; Cabral Cano, E.; Fawcett, P.J.; Lozano-Garc'ia, S.; Ortega, B.; P'erez, L.; Schwalb, A.; Smith, V.; Steinman, B.A.; Stockhecke, M.; Valero-Garc'es, B.; et al. (Scientific Drilling, 2019)
The primary scientific objective of MexiDrill, the Basin of Mexico Drilling Program, is development of a continuous, high-resolution <span classCombining double low lineinline-formula ∼4400kyr lacustrine record of tropical North American environmental change. The field location, in the densely populated, water-stressed Mexico City region gives this record particular societal relevance. A detailed paleoclimate reconstruction from central Mexico will enhance our understanding of long-term natural climate variability in the North American tropics and its relationship with changes at higher latitudes. The site lies at the northern margin of the Intertropical Convergence Zone (ITCZ), where modern precipitation amounts are influenced by sea surface temperatures in the Pacific and Atlantic basins. During the Last Glacial Maximum (LGM), more winter precipitation at the site is hypothesized to have been a consequence of a southward displacement of the mid-latitude westerlies. It thus represents a key spatial node for understanding large-scale hydrological variability of tropical and subtropical North America and is at an altitude (2240 a.s.l.), typical of much of western North America. In addition, its sediments contain a rich record of pre-Holocene volcanic history; knowledge of the magnitude and frequency relationships of the area's explosive volcanic eruptions will improve capacity for risk assessment of future activity. Explosive eruption deposits will also be used to provide the backbone of a robust chronology necessary for full exploitation of the paleoclimate record. Here we report initial results from, and outreach activities of, the 2016 coring campaign. © Author(s) 2019.
cited By 11
Keywords: Explosives; Infill drilling; Oceanography; Risk assessment; Surface waters; Volcanoes; Environmental change; Hydrological variability; Intertropical convergence zone; Natural climate variabilities; Paleoclimate reconstruction; Paleoclimate records; Scientific objectives; Sea surface temperature (SST); Tropics

Sediment residence time reveals Holocene shift from climatic to vegetation control on catchment erosion in the Balkans - Francke, A.; Dosseto, A.; Panagiotopoulos, K.; Leicher, N.; Lacey, J.H.; Kyrikou, S.; Wagner, B.; Zanchetta, G.; Kouli, K.; Leng, M.J. (Global and Planetary Change, 2019)
Understanding the evolution of soil systems on geological time scales has become fundamentally important to predict future landscape development in light of rapid global warming and intensifying anthropogenic impact. Here, we use an innovative uranium isotope-based technique combined with organic carbon isotopes and elemental ratios of sediments from Lake Ohrid (North Macedonia/Albania) to reconstruct soil system evolution in the lake's catchment during the last 16,000 cal yr BP. Uranium isotopes are used to estimated the paleo-sediment residence time, defined as the time elapsed between formation of silt and clay sized detrital matter and final deposition. The chronology is based on new cryptotephra layers identified in the sediment sequence. The isotope and elemental data are compared to sedimentary properties and pollen from the same sample material to provide a better understanding of past catchment erosion and landscape evolution in the light of climate forcing, vegetation development, and anthropogenic land use. During the Late Glacial and the Early Holocene, when wide parts of the catchment were covered by open vegetation, wetter climates promoted the mobilisation of detrital matter with a short paleo-sediment residence time. This is explained by erosion of deeper parts of the weathering horizon from thin soils. Detrital matter with a longer paleo-sediment residence time, illustrating shallow erosion of thicker soils is deposited in drier climates. The coupling between climatic variations and soil erosion terminates at the Early to Mid-Holocene transition as evidenced by a pronounced shift in uranium isotope ratios indicating that catchment erosion is dominated by shallow erosion of thick soils only. This shift suggests a threshold is crossed in hillslope erosion, possibly as a result of a major change in vegetation cover preventing deep erosion of thin soils at higher elevation. The threshold in catchment erosion is not mirrored by soil development over time, which gradually increases in response to Late Glacial to Holocene warming until human land use during the Late Holocene promotes reduced soil development and soil degradation. Overall, we observe that soil system evolution is progressively controlled by climatic, vegetation, and eventually by human land use over the last 16,000 years. © 2019 Elsevier B.V.
cited By 21
Keywords: Catchments; Erosion; Geomorphology; Glacial geology; Global warming; Isotopes; Lakes; Land use; Nuclear fuels; Organic carbon; Runoff; Sediments; Uranium; Vegetation; Balkan peninsulas; Human impact; Lake Ohrid; Landscape evolutions; Paleoclimates; Residence time; Soil systems; Tephrochronology; Uranium isotopes; Soils; catchment; detrital deposit; geomorphology; global warming; Holocene; landscape evolution; organic carbon; residence time; sediment analysis; soil erosion; tephrochronology; uranium isotope; vegetation cover; weathering rate; Albania; Balkans; Greece; Lake Ohrid; Macedonia [Greece]

Seismic depth imaging of sequence boundaries beneath the New Jersey shelf - Riedel, M.; Reiche, S.; A{shoff, K.; Buske, S. (Marine Geophysical Research, 2019)
Numerical modelling of fluid flow and transport processes relies on a well-constrained geological model, which is usually provided by seismic reflection surveys. In the New Jersey shelf area a large number of 2D seismic profiles provide an extensive database for constructing a reliable geological model. However, for the purpose of modelling groundwater flow, the seismic data need to be depth-converted which is usually accomplished using complementary data from borehole logs. Due to the limited availability of such data in the New Jersey shelf, we propose a two-stage processing strategy with particular emphasis on reflection tomography and pre-stack depth imaging. We apply this workflow to a seismic section crossing the entire New Jersey shelf. Due to the tomography-based velocity modelling, the processing flow does not depend on the availability of borehole logging data. Nonetheless, we validate our results by comparing the migrated depths of selected geological horizons to borehole core data from the IODP expedition 313 drill sites, located at three positions along our seismic line. The comparison yields that in the top 450 m of the migrated section, most of the selected reflectors were positioned with an accuracy close to the seismic resolution limit (≈ 4 m) for that data. For deeper layers the accuracy still remains within one seismic wavelength for the majority of the tested horizons. These results demonstrate that the processed seismic data provide a reliable basis for constructing a hydrogeological model. Furthermore, the proposed workflow can be applied to other seismic profiles in the New Jersey shelf, which will lead to an even better constrained model. © 2018, Springer Science+Business Media B.V., part of Springer Nature.
cited By 4
Keywords: Geologic models; Geophysical prospecting; Groundwater; Groundwater flow; Seismic response; Tomography; Well logging; Complementary data; Geological modeling; Groundwater modelling; Hydrogeological models; Seismic imaging; Seismic reflection survey; Seismic resolution; Two-stage processing; Seismic waves; borehole logging; groundwater flow; imaging method; numerical model; Ocean Drilling Program; seismic data; seismic tomography; seismic velocity; Atlantic Ocean; New Jersey Shelf

SUSTAIN drilling at Surtsey volcano, Iceland, tracks hydrothermal and microbiological interactions in basalt 50 years after eruption - Jackson, M.D.; Gudmundsson, M.T.; Weisenberger, T.B.; Michael Rhodes, J.; Stef'ansson, A.; Kleine, B.I.; Lippert, P.C.; Marquardt, J.M.; Reynolds, H.I.; Marteinsson, V.T.; Vannier, P.; Bach, W.; et al. (Scientific Drilling, 2019)
The 2017 Surtsey Underwater volcanic System for Thermophiles, Alteration processes and INnovative concretes (SUSTAIN) drilling project at Surtsey volcano, sponsored in part by the International Continental Scientific Drilling Program (ICDP), provides precise observations of the hydrothermal, geochemical, geomagnetic, and microbiological changes that have occurred in basaltic tephra and minor intrusions since explosive and effusive eruptions produced the oceanic island in 1963-1967. Two vertically cored boreholes, to 152 and 192m below the surface, were drilled using filtered, UV-sterilized seawater circulating fluid to minimize microbial contamination. These cores parallel a 181m core drilled in 1979. Introductory investigations indicate changes in material properties and whole-rock compositions over the past 38 years. A Surtsey subsurface observatory installed to 181m in one vertical borehole holds incubation experiments that monitor in situ mineralogical and microbial alteration processes at 25-124 °C. A third cored borehole, inclined 55° in a 264° azimuthal direction to 354m measured depth, provides further insights into eruption processes, including the presence of a diatreme that extends at least 100m into the seafloor beneath the Surtur crater. The SUSTAIN project provides the first time-lapse drilling record into a very young oceanic basaltic volcano over a range of temperatures, 25-141 °C from 1979 to 2017, and subaerial and submarine hydrothermal fluid compositions. Rigorous procedures undertaken during the drilling operation protected the sensitive environment of the Surtsey Natural Preserve. © Author(s) 2019.
cited By 13
Keywords: Boreholes; Boring; Geomagnetism; Infill drilling; Volcanoes; Azimuthal direction; Circulating fluids; Continental scientific drillings; Drilling operation; Effusive eruptions; Hydrothermal fluids; Microbial contamination; Vertical borehole; Core drilling

Seismic Velocity Estimation Using Passive Downhole Distributed Acoustic Sensing Records: Examples From the San Andreas Fault Observatory at Depth - Lellouch, A.; Yuan, S.; Spica, Z.; Biondi, B.; Ellsworth, W.L. (Journal of Geophysical Research: Solid Earth, 2019)
Structural imaging and event location require an accurate estimation of the seismic velocity. However, active seismic surveys used to estimate it are expensive and time-consuming. During the last decade, fiber-optic-based distributed acoustic sensing has emerged as a reliable, enduring, and high-resolution seismic sensing technology. We show how downhole distributed acoustic sensing passive records from the San Andreas Fault Observatory at Depth can be used for seismic velocity estimation. Using data recorded from earthquakes propagating near-vertically, we compute seismic velocities using first-break picking as well as slant stack decomposition. This methodology allows for the estimation of both P and S wave velocity models. We also use records of the ambient seismic field for interferometry and P wave velocity model extraction. Results are compared to a regional model obtained from surface seismic as well as a conventional downhole geophone survey. We find that using recorded earthquakes, we obtain the highest P wave model resolution. In addition, it is the only method that allows for S wave velocity estimation. Computed P and S models unravel three distinct areas at the depth range of 50-750 m, which were not present in the regional model. In addition, we find high VP/VS values near the surface and a possible VP/VS anomaly about 500 m deep. We confirm its existence by observing a strong S-P mode conversion at that depth. ©2019. American Geophysical Union. All Rights Reserved.
cited By 40
Keywords: acoustic survey; borehole geophysics; estimation method; geophone; P-wave; S-wave; San Andreas Fault; seismic velocity; California; San Andreas; United States

Slow strain release along the eastern Marmara region offshore Istanbul in conjunction with enhanced local seismic moment release - Mart'inez-Garz'on, Patricia; Bohnhoff, Marco; Mencin, David; Kwiatek, Grzegorz; Hodgkinson, Kathleen; Nurlu, Murat; Kadirioglu, Filiz Tuba; Kartal, Recai Feyiz (Earth and Planetary Science Letters, 2019)
We analyze a large transient strainmeter signal recorded at 62.5 m depth along the southern shore of the eastern Sea of Marmara region in northwestern Turkey. This region represents a passage of stress transfer from the Izmit rupture to the Marmara seismic gap. The strain signal was recorded at the Esenkoy site by one of the ICDP-GONAF (International Continental Drilling Programme – Geophysical Observatory at the North Anatolian Fault) strainmeters on the Armutlu peninsula with a maximum amplitude of 5 microstrain and lasting about 50 days. The onset of the strain signal coincided with the origin time of a M W 4.4 earthquake offshore Yalova, which occurred as part of a seismic sequence including eight M W ≥3.5 earthquakes. The M W 4.4 event occurred at a distance of about 30 km from Esenkoy on June 25th 2016 representing the largest earthquake in this region since 2008. Before the event, the maximum horizontal strain was subparallel to the regional maximum horizontal stress derived from stress inversion of local seismicity. During the strain transient, we observe a clockwise rotation in the local horizontal strain field of about 20°. The strain signal does not correlate with known environmental parameters such as annual changes of sea level, rainfall or temperature. The strain signal could indicate local slow slip on the Cinarcik fault and thus a transfer of stress to the eastern Marmara seismic gap. © 2019 Elsevier B.V.
Keywords: Armutlu Peninsula; Istanbul [Istanbul (PRV)]; Istanbul [Turkey]; Sea of Marmara; Turkey; Earthquakes; Offshore oil well production; Sea level; Strain measurement; Transform faults; Sea of Marmara; Seismic hazards; slow slip; Strain transients; Strain-meter; amplitude; earthquake event; earthquake rupture; fault slip; seismic hazard; strain; stress; transform fault; Fault slips

Spatial and temporal reconstruction of the late Quaternary Dead Sea sedimentary facies from geophysical properties - Coianiz, L.; Ben-Avraham, Z.; Stein, M.; Lazar, M. (Journal of Applied Geophysics, 2019)
The sedimentary sequences that accumulated within various lakes that occupied the Dead Sea Basin since the Pliocene, contain a detailed record of the climate and tectonic history of the area. Until recently, most of the information about these paleo-lakes was derived from exposures along the marginal terraces of the current Dead Sea (lake), focusing mainly on the last Glacial Lake Lisan and the Holocene-modern Dead Sea. The International Continental Drilling Program (ICDP) recovered a series of cores in the northern Dead Sea Basin, both in the deep depocenter (300 m water depth) and in shallower waters near the current shore. Here, we present downhole logging measurements that were used to provide continuous records of petrophysical properties at depth and to reconstruct lithological profiles. The study highlights how logging data can overcome gaps in drilled-core recovery and be used to examine subsurface geology on a regional scale. Gamma ray, resistivity and velocity wire logs were examined to infer a log-derived lithofacies. The reconstructed profiles presented in this study constitute a first attempt to link deep central settings of the basin with marginal sedimentary sequences. Three main facies were identified in the boreholes including: (Bartov et al., 2002) Finely laminated sequences of mudstones interbedded with siltstones to sandstones; (Bartov et al., 2003) Medium to thick bedded mudstone to sandstone: and (Bartov et al., 2007) Evaporites (e.g. halite and gypsum with some intervals of detrital sediments). The formations that were previously defined along the marginal terraces of the Dead Sea: the Holocene Ze'elim Formation, the last Glacial Lisan Formation, the last interglacial Samra Formation and the early to mid-Pleistocene Amora Formation are identified in the boreholes. A spatial correlation is established providing the stratigraphic architecture of the sedimentary structure beneath the Dead Sea during the late Quaternary. This paper combines geophysical and lithological data and provides the base for subsequent studies on facies interpretation. © 2018 Elsevier B.V.
cited By 10
Keywords: Boreholes; Boring; Gamma rays; Geophysics; Glacial geology; Infill drilling; Lakes; Lithology; Sandstone; Sodium chloride; Stratigraphy; Well logging; Dead sea basins; Downholes; Geophysical properties; ICDP; Petrophysical properties; Sedimentary structure; Stratigraphic architecture; Well logs; Sedimentology; facies analysis; lacustrine deposit; lithofacies; lithology; mudstone; Quaternary; reconstruction; sediment core; sedimentary sequence; sedimentary structure; siltstone; spatial analysis; temporal analysis; well logging; Dead Sea

Spatial variation in stress in seismogenic zones in south african gold mines - Ogasawara, H.; Ishida, A.; Sugimura, K.; Yabe, Y.; Abe, S.; Ito, T.; Funato, A.; Kato, H.; Liebenberg, B.; Hofmann, G.; Scheepers, L.; Durrheim, R.J. (Rock Dynamics Summit - Proceedings of the 2019 Rock Dynamics Summit, RDS 2019, 2019)

Stress-Strain Evolution During Peak-Ring Formation: A Case Study of the Chicxulub Impact Structure - Rae, A.S.P.; Collins, G.S.; Poelchau, M.; Riller, U.; Davison, T.M.; Grieve, R.A.F.; Osinski, G.R.; Morgan, J.V.; Iodp-Icdp, E. (Journal of Geophysical Research: Planets, 2019)
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.
cited By 25

Structural characteristics of Shahezi Formation beneath the Well SK-2 and its periphery: An analysis of logging and seismic data; [松科二井邻域沙河子组含油气地层结构特征-基于测井和地震数据的分析] - Fu, Wei; Hou, Hesheng; Zhang, Jiaodong; Liu, Cai; Feng, Xuan; Lu, Zhanwu (Geology in China, 2019)
During implementation of the Deep Continental Scientific Drilling Engineering Project Well SK-2 in Songliao Basin, the most integrated core data of Shahezi Formation was obtained. And 43 abnormal strata of deep shale gas were preliminarily identified, with a cumulative thickness of 102 meters, indicating that Shahezi Formation has good deep energy prospect. For further analysis of oil and gas resources potential of Shahezi Formation in Songliao basin, in this paper, on the basis of previous studies and in combination with well logging, core data of Well SK-2 and the newly acquired 2-d seismic data in the north-south direction crossing Well SK-2, the spatial distribution and sequence characteristics of Shahezi formation in the vicinity of Well SK-2 well were analyzed. At the same time, based on gas abnormal data acquired form logging during drilling, the authors studied logging and seismic responses of oil and gas perspective reservoirs in Shahezi Formation. It is shown that the Shahezi Formation adjacent to Well SK-2 has large thickness but small lateral extension, and hence the authors divided it into 4 stratigraphic sequences based on well logging as well as seismic and core data, i.e., SQ1, SQ2, SQ3 and SQ4. Among the 4 stratigraphic sequences, SQ4 has a better energy prospect. Its lithology is dominated by mudstone and has the characteristics of high porosity and low wave impedance on logging curves, with continuous strong amplitude on seismic section. Impedance inversion section shows the characteristics of large wave impedance alternated with many smaller wave impedances. Thus, the occurrence conditions of deep natural gas resources of Shahezi Formation in this area are revealed. © 2019 Editorial Board of Geology in China. All rights reserved.

Mobilization of fine detritus to the Dead Sea Basin during the late glacial and early Holocene - Palchan, D.; Erel, Y.; Stein, M. (Quaternary Science Reviews, 2019)
The mineralogical, grain size and geochemical properties (e.g., Nd and Sr isotopes, Mg/Al ratios) of fine detritus that accumulated in the Dead Sea during the late Glacial to early Holocene time (∼22 –7 ka) are used to identify its sources and modes of transport and to reconstruct the hydroclimate conditions in the Dead Sea watershed. Samples were retrieved from the DSDDP -5017-1A core that was drilled in the deep floor of the lake, and from various exposures of surface cover in the lake's watershed. The data show that during most of the late glacial, detrital particles were either directly blown mostly from the north Sahara Desert or were washed from the surface cover (loessial soils) of the north Negev Desert and Judea Desert. This picture changed during the end of the last glacial to the early Holocene (∼14 - 7 ka) when the fine detritus showed evidence for contribution from surface cover that contained basaltic soils. The contribution of basaltic soils to the fine detritus inventory of the Dead Sea and to terraces in the Jordan Valley, indicates a period of intense erosion in the northern highlands of the Dead Sea watershed, at an interval that partly coincides with Sapropel S1. In contrast, during the last interglacial Sapropel S5, fine detritus was mostly mobilized to the lake from southern and eastern region of the watershed. The formation and accumulation of terraces from this basaltic-derived material could be an important factor in the establishment of early agriculture settlements in the Jordan Valley. © 2019 Elsevier Ltd
cited By 12
Keywords: Basalt; Glacial geology; Lakes; Seawater; Soils; Watersheds; Basaltic soils; Dead sea basins; Derived materials; Early Holocene; Eastern regions; Geochemical properties; Jordan valley; Last interglacial; Landforms; basalt; detritus; fine grained sediment; grain size; Holocene; late glacial; mobilization; sapropel; seafloor; submarine terrace; Dead Sea; Israel; Jordan Valley; Negev; Sahara; Southern District

A discussion on deep-well combined drill string technology for ultra-deep drilling engineering [深井复合钻柱技术在特深科学钻探中的应用探讨] - Li, L.; Zhang, F.; Wang, W.; Zhang, Y.; Hu, Y. (Geology in China, 2019)
Deep-well combined drill string technology has become one of the most important scheme to solve the super-long drill string used for ultra-deep drilling project, which is related to equipment capacity, material property, drilling conditions and string mechanics. In this paper, the application and development of combined drill string technology in geological drilling are summarized systematically, the design scheme and its limitation length are discussed in detail on the basis of strength theory. The results show that the drilling mission with the depth of 13000m could not be finished by simply using pure steel combined drill string with the final borehole diameter being 216mm. By using drill string consisting of V150 steel drill pipe & titanium alloy drill pipe and S135 steel drill pipe & aluminum alloy drill pipe, the limitation depth and the weight of each combined drill string are respectively 13484m, 18783m and 360.5, 324.3t; in this way both of them own application reliability and advantage. These results have reference significance to the design and selection of deep-well combined drill string used for ultra-deep drilling project. © 2019 Editorial Board of Geology in China. All rights reserved.
cited By 1