An ostracod-based record of paleoecological conditions during MIS6 and MIS5, from Lake Chalco, Basin of Mexico - Ch'avez-Lara, C.M.; Lozano-Garc'ia, S.; Ortega-Guerrero, B.; Caballero-Miranda, M.; Avendaño, D.; Brown, E.T. (Journal of Paleolimnology, 2022)
A sediment record from Lake Chalco, Basin of Mexico, revealed the presence of two endemic ostracod species during the latter part of Marine Isotope Stages (MIS) 6 (146 –130 ka) and MIS5 (130 –72 ka), namely Candona alchichica and Limnocytherina axalapasco. Higher abundance of C. alchichica was found during MIS6, when prevailing conditions were cold, lake waters were fresh, and relatively deep bottom waters were anoxic. The species is typically associated with saline environments today, consistent with its presence in MIS5 sediments. The Chalco record, however, reveals that it coexisted with freshwater diatom species during MIS6. Thus, we suggest that C. alchichica had a wider salinity tolerance, ranging from freshwater to more saline environments. Examination of MIS5 substages provides further insights into ostracod species responses to changing lake conditions. During MIS5e, the lake water level declined and salinity and dissolved oxygen in the water column increased, thereby favouring L. axalapasco productivity, whereas C. alchichica productivity decreased. Enhanced runoff and lower than average evaporation during MIS5d coincided with the increasing abundance of C. alchichica, suggesting a period of relatively high lake level and more dilute waters. These environmental conditions, however, changed during MIS5c when lake stage dropped once again and L. axalapasco abundance increased. Shallow conditions during this substage were optimal for L. axalapasco. Subsequently, as the lake level continued to decline during MIS5b, both ostracod species disappeared from the sediment record. Finally, during MIS5a, runoff increased and both ostracod species reappeared in the record, with L. axalapasco dominating, suggesting another period of lake level recovery. Increased evaporation rates during the last part of this substage (75 –72 cal ka BP) may have led to disappearance of ostracods from the sediment record. Overall, during MIS5, we detected higher L. axalapasco, which represent relatively shallow lake conditions. © 2022, The Author(s), under exclusive licence to Springer Nature B.V.
cited By 4
Keywords: dissolved oxygen; environmental conditions; lake level; lake water; marine isotope stage; ostracod; paleoecology; runoff; seawater; Lake Chalco; Mexico [North America]; Valley of Mexico

Anisotropic velocity models for (3-D) seismic imaging of the Lower Seve Nappe in J{amtland, Sweden - K{astner, Felix; Klaeschen, Dirk; Berndt, Christian; Pierdominici, Simona; Hedin, Peter (Geophysical Journal International, 2022)
Strong anisotropy of seismic velocity in the Earth's crust poses serious challenges for seismic imaging. Where in situ seismic properties are not available, the anisotropy can be determined from velocity analysis of surface and borehole seismic profiles. This is well established for dense, long-offset reflection seismic data. However, it is unknown how applicable this approach is for sparse seismic reflection data with low fold and short offsets in anisotropic metamorphic rocks. Here, we show that anisotropy parameters can be determined from a sparse 3-D data set at the COSC-1 borehole site in the Swedish Caledonides and that the results agree well with the seismic anisotropy parameters determined from seismic laboratory measurements on core samples. Applying these anisotropy parameters during 3-D seismic imaging improves the seismic image of the high-amplitude reflections especially in the vicinity of the lower part of the borehole. Strong reflections in the resulting seismic data show good correlation with the borehole-derived lithology. Our results aid the interpretation and extrapolation of the seismic stratigraphy of the Lower Seve Nappe in J{amtland and other parts in the Caledonides.

COSC-2 - drilling the basal d'ecollement and underlying margin of palaeocontinent Baltica in the Paleozoic Caledonide Orogen of Scandinavia - Lorenz, Henning; Rosberg, Jan-Erik; Juhlin, Christopher; Klonowska, Iwona; Lescoutre, Rodolphe; Westmeijer, George; Almqvist, Bjarne S. G.; Anderson, Mark; Bertilsson, Stefan; Dopson, Mark; Kallmeyer, Jens; K{uck, Jochem; et al. (Scientific Drilling, 2022)
Abstract. The Collisional Orogeny in the Scandinavian Caledonides (COSC) scientific drilling project aims to characterise the structure and orogenic processes involved in a major collisional mountain belt by multidisciplinary geoscientific research. Located in western central Sweden, the project has drilled two fully cored deep boreholes into the bedrock of the deeply eroded Early Paleozoic Caledonide Orogen. COSC-1 (2014) drilled a subduction-related allochthon and the associated thrust zone. COSC-2 (2020, this paper) extends this section deeper through the underlying nappes (Lower Allochthon), the main Caledonian d'ecollement, and the upper kilometre of basement rocks. COSC-2 targets include the characterisation of orogen-scale detachments, the impact of orogenesis on the basement below the detachment, and the Early Paleozoic palaeoenvironment on the outer margin of palaeocontinent Baltica. This is complemented by research on heat flow, groundwater flow, and the characterisation of the microbial community in the present hard rock environment of the relict mountain belt. COSC-2 successfully, and within budget, recovered a continuous drill core to 2276 m depth. The retrieved geological section is partially different from the expected geological section with respect to the depth to the main d'ecollement and the expected rock types. Although the intensity of synsedimentary deformation in the rocks in the upper part of the drill core might impede the analysis of the Early Paleozoic palaeoenvironment, the superb quality of the drill core and the borehole will facilitate research on the remaining targets and beyond. Protocols for sampling in the hard rock environment and subsequent sample preservation were established for geomicrobiological research and rock mechanical testing. For the former, a sparse sample series along the entire drill core was taken, while the target of the latter was the d'ecollement. COSC-2 was surveyed by a comprehensive post-drilling downhole logging campaign and a combined borehole/land seismic survey in autumn 2021. This paper provides an overview of the COSC-2 (International Continental Scientific Drilling Project – ICDP 5054_2_A and 5054_2_B boreholes) operations and preliminary results. It will be complemented by a detailed operational report and data publication.
Publisher: Copernicus GmbH

A Four-Phase Model for Methane Production from an Unconsolidated Hydrate Reservoir. Part 1. Model Development - Hinz, D.; Arastoopour, H.; Abbasian, J. (Industrial and Engineering Chemistry Research, 2022)
A four-phase flow model is developed to capture the unconsolidated flow of gas, water, hydrate, and sand. The solid phase models are an extension of granular flow theory to unconsolidated hydrate-bearing sediment. A solid viscosity constitutive model is developed to model the frictional and cohesive contributions to the solid shear stress. In part 2 of this paper series, the model is validated against the Mallik 2007/2008 production tests. © 2022 American Chemical Society. All rights reserved.
cited By 0
Keywords: Confined flow; Gas hydrates; Granular materials; Shear stress; Flow modelling; Four-phase; Gas sands; Gas-water; Granular flows; Methane production; Model development; Phase flow; Phase model; Solid phase models; Hydration

Cuspate-lobate folding in glacial sediments revealed by a small-scale 3-D seismic survey - Buness, Hermann; Tanner, David Colin; Burschil, Thomas; Gabriel, Gerald; Wielandt-Schuster, Ulrike (Journal of Applied Geophysics, 2022)

Geomechanical Response Induced by Multiphase (Gas/Water) Flow in the Mallik Hydrate Reservoir of Canada - Xia, Y.; Xu, T.; Yuan, Y.; Xin, X. (SPE Journal, 2022)
Natural gas hydrate (NGH) is regarded as an important alternative future energy resource. In recent years, a few short-term production tests have been successfully conducted with both permafrost and marine sediments. However, long-term hydrate production performance and the potential geomechanical problems are not very clear. According to the available geological data at the Mallik site, a more realistic hydrate reservoir model that considers the heterogeneity of porosity, permeability, and hydrate saturation was developed and validated by reproducing the field depressurization test. The coupled multiphase and heat flow and geomechanical response induced by depressurization were fully investigated for long-term gas production from the validated hydrate reservoir model. The results indicate that long-term gas production through depressurization from a vertically heterogeneous hydrate reservoir is technically feasible, but the production efficiency is generally modest, with the low average gas production rate of 4.93 × 103 ST m3/d (ST represents the standard conditions) over a 1-year period. The hydrate dissociation region is significantly affected by the reservoir heterogeneity and reveals a heterogeneous dissociation front in the reservoir. The depressurization production results in significant increase of shear stress and vertical compaction in the hydrate reservoir. The response of shear stress indicates that the potential region of sand migration is mainly in the sand-dominant layer during gas production from the hydraulically heterogeneous hydrate reservoir (e.g., sand layers interbedded with clay layers). The maximum subsidence is approximately 78 mm and occurred at the 72nd day, whereas the final subsidence is slowly dropped to 63 mm after 1-year of depressurization production. The vertical subsidence is greatly dependent on the elastic properties and the permeability anisotropy. In particular, the maximum subsidence increased by approximately 81% when the ratio of permeability anisotropy was set at 5:1. Furthermore, the potential shear failure in the hydrate reservoir is strongly correlated to the in-situ stress state. For the normal fault stress regime, the greater the initial horizontal stress is, the less likely the hydrate reservoir is to undergo shear failure during depressurization production. Copyright © 2022 Society of Petroleum Engineers
cited By 3
Keywords: Anisotropy; Dissociation; Energy resources; Gas hydrates; Gases; Hydration; Petroleum deposits; Petroleum reservoir engineering; Shear stress; Submarine geology; Subsidence; Depressurizations; Gas productions; Gas-water; Multiphase gas; Natural gas hydrates; Natural gas-hydrates; Permeability anisotropy; Reservoir models; Shear failure; Water flows; Geomechanics

Fault systems in the offshore sector of the Campi Flegrei caldera (southern Italy): Implications for nested caldera structure, resurgent dome, and volcano-tectonic evolution - Natale, Jacopo; Camanni, Giovanni; Ferranti, Luigi; Isaia, Roberto; Sacchi, Marco; Spiess, Volkhard; Steinmann, Lena; Vitale, Stefano (JOURNAL OF STRUCTURAL GEOLOGY, 2022)
The structure of a caldera may influence its activity, making its understanding crucial for hazard assessment. Here, we analysed high-resolution seismic profiles in the Campi Flegrei (southern Italy) offshore sector. We recognised two main fault systems, including those associated with the formation of the caldera and those affecting the resurgent dome. The former system comprises three broadly concentric fault zones (inner, medial and outer ring fault zones) depicting a nested caldera geometry. Considering the relations between faults and seismic units that represent the marine and volcaniclastic successions filling the caldera, all ring faults were formed during the Campanian Ignimbrite eruption (40 ka) and subsequently reactivated during the Neapolitan Yellow Tuff eruption (15 ka). In this last caldera-forming event, the inner and medial fault zones accommodated most of the collapse and were episodically reactivated during the younger volcano-tectonic activity. The second fault system occurs in the apical zone of the resurgent dome and comprises dominantly high-angle normal faults that are mainly related to the volcano -tectonic collapse that followed the Agnano-Monte Spina Plinian eruption (4.55 ka). Finally, we provide a volcano-tectonic evolutionary model of the last 40 kyr, considering the interplay among ring and dome faults activity, volcaniclastic sedimentation, ground deformation and sea-level changes.

Formation of the crater suevite sequence from the Chicxulub peak ring: A petrographic, geochemical, and sedimentological characterization - Kaskes, P.; Graaff, S.J.; Feignon, J.-G.; D'ehais, T.; Goderis, S.; Ferrière, L.; Koeberl, C.; Smit, J.; Wittmann, A.; Gulick, S.P.S.; Debaille, V.; Mattielli, N.; et al. (Bulletin of the Geological Society of America, 2022)
This study presents a new classification of a 100-m-thick crater suevite sequence in the recent International Ocean Discovery Program (IODP)-International Continental Scientific Drilling Program (ICDP) Expedition 364 Hole M0077A drill core to better understand the formation of suevite on top of the Chicxulub peak ring. We provide an extensive data set for this succession that consists of whole-rock major and trace element compositional data (n = 212) and petrographic data supported by digital image analysis. The suevite sequence is subdivided into three units that are distinct in their petrography, geochemistry, and sedimentology, from base to top: the 5.6-m-thick non-graded suevite unit, the 89-m-thick graded suevite unit, and the 3.5-m-thick bedded suevite unit. All of these suevite units have isolated Cretaceous planktic foraminifera within their clastic groundmass, which suggests that marine processes were responsible for the deposition of the entire M0077A suevite sequence. The most likely scenario describes that the first ocean water that reached the northern peak ring region entered through a N-NE gap in the Chicxulub outer rim. We estimate that this ocean water arrived at Site M0077 within 30 minutes after the impact and was relatively poor in rock debris. This water caused intense quench fragmentation when it interacted with the underlying hot impact melt rock, and this resulted in the emplacement of the 5.6-m-thick hyaloclastite-like, non-graded suevite unit. In the following hours, the impact structure was flooded by an ocean resurge rich in rock debris, which caused the phreatomagmatic processes to stop and the 89-m-thick graded suevite unit to be deposited. We interpret that after the energy of the resurge slowly dissipated, oscillating seiche waves took over the sedimentary regime and formed the 3.5-m-thick bedded suevite unit. The final stages of the formation of the impactite sequence (estimated to be <20 years after impact) were dominated by resuspension and slow atmospheric settling, including the final deposition of Chicxulub impactor debris. Cumulatively, the Site M0077 suevite sequence from the Chicxulub impact site preserved a high-resolution record that provides an unprecedented window for unravelling the dynamics and timing of proximal marine cratering processes in the direct aftermath of a large impact event. © 2021 The Authors. Gold Open Access
cited By 11

Frictional stability and hydromechanical coupling of serpentinite-bearing fault gouge - Scuderi, M.M.; Carpenter, B.M. (Geophysical Journal International, 2022)
Observations of slow earthquakes and tremor have raised fundamental questions about the physics of quasi-dynamic rupture and the underlying fault zone processes. The presence of serpentinite at P-T conditions characteristic of deep tremor and slow earthquakes suggests that it plays an important role in controlling complex fault slip behaviour. Here, we report on experiments designed to investigate the frictional behaviour of serpentinite sampled from outcrop exposures (SO1 and SO2) of altered ultramafic rocks present at depth, and recovered from the SAFOD borehole (G27). XRD analyses reveal the presence of chrisotyle, lizardite, kaolinite, talc in SO1; lizardite, clinochlore and magnetite in SO2; and lizardite, quartz and calcite in G27. We sheared fault gouge in a double-direct shear configuration using a true triaxial deformation apparatus. The effective normal stress was varied from 2 to 40 MPa. We conducted velocity stepping tests and slide-hold-slide (SHS) tests in each experiment to characterize frictional stability and healing. At the end of each experiment, post-shear permeability was measured and the samples were recovered for microstructural analysis. The steady-state friction coefficient was μ = 0.17 for SO1, μ = 0.33 for SO2 and μ = 0.53 for G27. Overall, the gouges exhibit velocity strengthening behaviour, and become nearly velocity neutral at 40 MPa effective normal stress. SHS tests show positive healing rates for SO2 and G27, whereas SO1 exhibits zero or negative healing rates. Permeability decreases with increasing σn', with SO1 (k = 10-20 m2) showing the lowest values. Microstructural observations reveal a well-developed R-Y-P fabric in SO1, which is not observed in SO2 and G27. We posit that the development of shear fabric controlled by mineralogy governs frictional and hydrological properties. In this context, when serpentinite is associated with other weak phyllosilicate minerals, frictional stability and hydrological properties can vary greatly, with a potential control on the mode of fault failure. © 2022 The Author(s) 2022. Published by Oxford University Press on behalf of The Royal Astronomical Society.
cited By 1
Keywords: Calcite; Earthquakes; Elasticity; Fault slips; Kaolinite; Magnesite; Magnetite; Shear flow; Effective normal stress; Fault gouge; Fault zone; Fault zone rheology; Frictional stability; Hydrological properties; Lizardite; Permeability and porosities; Rheology and friction of fault zones; Serpentinite; Friction; deformation mechanism; earthquake rupture; experimental study; fault gouge; fault slip; fault zone; friction; hydromechanics; microstructure; mineralogy; P-T conditions; permeability; phyllosilicate; porosity; rheology; serpentinite; structural control; triaxial test

Gas Migration Episodes Observed During Peridotite Alteration in the Samail Ophiolite, Oman - Aiken, J.M.; Sohn, R.A.; Renard, F.; Matter, J.; Kelemen, P.; Jamtveit, B. (Geophysical Research Letters, 2022)
Serpentinization and carbonation of mantle rocks (peridotite alteration) are fundamentally important processes for a spectrum of geoscience topics, including arc volcanism, earthquake processes, chemosynthetic biological communities, and carbon sequestration. Data from a hydrophone array deployed in the Multi-Borehole Observatory (MBO) of the Oman Drilling Project demonstrates that free gas generated by peridotite alteration and/or microbial activity migrates through the formation in discrete bursts of activity. We detected several, minutes-long, swarms of gas discharge into Hole BA1B of the MBO over the course of a 9 month observation interval. The episodic nature of the migration events indicates that free gas accumulates in the permeable flow network, is pressurized, and discharges rapidly into the borehole when a critical pressure, likely associated with a capillary barrier at a flow constriction, is reached. Our observations reveal a dynamic mode of fluid migration during serpentinization, and highlight the important role that free gas can play in modulating pore pressure, fluid flow, and alteration kinetics during peridotite weathering. © 2022. The Authors.
cited By 0
Keywords: Acoustics; Boreholes; Flow of fluids; Gases; Groundwater; Rocks; Weathering; Arc volcanism; Earthquake process; Free gas; Gas migration; Geosciences; Mantle rocks; Peridotite alterations; Reaction-driven crackings; Serpentinization; Spectra' s; Hydrogeology; borehole; earthquake; hydrogeology; hydrophone; migration; serpentinization; Oman

Geochemical Characterization of the Oman Crust-Mantle Transition Zone, OmanDP Holes CM1A and CM2B - Kourim, F.; Rospab'e, M.; Dygert, N.; Chatterjee, S.; Takazawa, E.; Wang, K.-L.; Godard, M.; Benoit, M.; Giampouras, M.; Ishii, K.; Teagle, D.A.H.; Cooper, M.-J.; et al. (Journal of Geophysical Research: Solid Earth, 2022)
The transition from the gabbroic oceanic crust to the residual mantle harzburgites of the Oman ophiolite has been drilled at Holes CM1A and CM2B (Wadi Tayin massif) during Phase 2 of the International Continental Scientific Drilling Program Oman Drilling Project (November 2017 –January 2018). In order to unravel the formation processes of ultramafic rocks in the Wadi Tayin massif crust-mantle transition zone and deeper in the mantle sections beneath oceanic spreading centers, our study focuses on the whole rock major and trace element compositions (together with CO2 and H2O concentrations) of these ultramafic rocks (56 dunites and 49 harzburgites). Despite extensive serpentinization and some carbonation, most of the trace element contents (REE, HFSE, Ti, Th, U) record high temperature, magmatic process-related signatures. Two major trends are observed, with good correlations between (a) Th and U, Nb and LREE on one hand, and between (b) heavy REE, Ti and Hf on the other hand. We interpret the first trend as the signature of late melt/peridotite interactions as LREE are known to be mobilized by such processes (lithospheric process’’) and the second trend as the signature of the initial mantle partial melting (asthenospheric process’’), with little or no overprint from melt/rock reaction events. © 2022. American Geophysical Union. All Rights Reserved.
cited By 0
Keywords: crust-mantle boundary; drilling; dunite; geochemistry; harzburgite; partial melting; serpentinization; transition zone; Oman

Geochemistry of macrofossil, bulk rock and secondary calcite in the Early Jurassic strata of the Llanbedr (Mochras Farm) drill core, Cardigan Bay Basin, Wales, UK - Ullmann, Clemens V.; Szűcs, Dominika; Jiang, Mengjie; Hudson, Alexander J.L.; Hesselbo, Stephen P. (Journal of the Geological Society, 2022)
The Llanbedr (Mochras Farm) core (Wales, UK) yielded a >1300 m long mudrock sequence that has excellent potential for establishing an integrated stratigraphic scheme for the entire Early Jurassic Epoch. Lithological variations in the core are predominantly driven by hierarchical changes in the carbonate content. These changes also dominate – or may impact upon – many geochemical and physical properties of the core. The bulk carbonate C isotope record displays systematic fluctuations, the largest of which correspond to previously identified phases of environmental perturbation. The magnitudes of negative C isotope excursions in carbonate are inflated compared with equivalents previously described elsewhere as a result of diagenesis and the concomitant loss of primary carbonate. The marine macrofossil record of Mochras reveals biological and isotopic patterns that are generally comparable with other UK basins. Potentially significant differences between the Cleveland and Cardigan Bay basins are observed in the Pliensbachian and Toarcian fossils. This different expression may be related to different habitat structures or palaeoceanographic and water depth differences between these basins. Minima in macrofossil δ18 O values generally coincide with peaks in macrofossil wood abundance and sea-level lowstands inferred from sequence stratigraphic interpretation of other UK sections. This relationship suggests a possible relative sea-level control on the observed O isotope records and sediment provenance. © 2021 The Author(s).
Keywords: Cardigan Bay; United Kingdom; Wales; Binary alloys; Calcite; Geochemistry; Infill drilling; Isotopes; Lithology; Sea level; Stratigraphy; Bulk carbonates; Bulk rocks; Carbonate content; Drill core; Early Jurassic; Early Jurassic Epoch; Geochemicals; Isotope record; Macrofossils; Mudrocks; calcite; depositional environment; fossil; geochemistry; Jurassic; mudstone; sequence stratigraphy; Carbonation

Half-precession signals in Lake Ohrid (Balkan) and their spatio-temporal relations to climate records from the European realm - Ulfers, Arne; Zeeden, Christian; Voigt, Silke; Sardar Abadi, Mehrdad; Wonik, Thomas (Quaternary Science Reviews, 2022)

Extended-Range Luminescence Dating of Central and Eastern Amazonia Sandy Terrains - Rodrigues, Fernanda Costa G.; Porat, Naomi; Mineli, Thays Desiree; Del R'io, Ian; Niyonzima, Pontien; Nogueira, Luciana; Pupim, Fabiano do Nascimento; Silva, Cleverson Guizan; Baker, Paul; Fritz, Sherilyn; Wahnfried, Ingo; Kiefer, Gustavo; et al. (Frontiers in Earth Science, 2022)

High resolution environmental conditions of the last interglacial (MIS5e) in the Levant from Sr, C and O isotopes from a Jerusalem stalagmite - Frumkin, A.; Stein, M.; Goldstein, S.L. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2022)
The southern Levant region at the fringe of the Saharan-Arabian deserts is particularly vulnerable to warming and desertification, therefore reconstruction of the hydroclimate conditions of this region during periods of past climate change provide important insight on what may occur in the future. Here we report on high temporal resolution 87Sr/86Sr, δ13C and δ18O isotope data of a stalagmite from the Har Nof cave in Jerusalem, demonstrating major climate changes during the last interglacial MIS5e between 131 –116 ka. We combine also data from other caves in Israel and the ICDP Dead Sea deep drill core. The following palaeoenvironmental history is observed: • At 131 –127.5 ka, Jerusalem experienced moderate Mediterranean climate conditions. Desert dust accumulated above the cave, while salt deposition occurred in the Dead Sea. • At 127.5 –122 ka, across the MIS5e insolation peak and Sapropel S5 interval in the Mediterranean, highly negative speleothem δ18O indicate both Mediterranean and southern (tropical) derived rains. Surface cover diminished, and by 122 ka the 87Sr/86Sr and δ13C values indicate complete soil removal above the cave. Very high temperatures and intensive fires caused the removal of C3 vegetation. The rainfall season shifted from winter to summer with tropical-sourced precipitation. • At 122 –120.5 ka, the 87Sr/86Sr ratios indicate contributions of sea salts. Extremely high speleothem δ13C values indicate no vegetation. • At 120.5 –118 ka there was higher rainfall and lower temperatures, associated with re-establishment of vegetation, including savannah-like C4 pioneer grasses that appeared on soil patches. • At 118 –116 ka, the sedimentation rate of Har Nof AF12 stalagmite is extremely low, indicating regional aridity, coinciding with massive salt deposition in the Dead Sea. © 2021 Elsevier B.V.
cited By 1
Keywords: climate change; environmental conditions; interglacial; isotopic ratio; Last Interglacial; precipitation (climatology); rainfall; reconstruction; sedimentation; sedimentation rate; speleothem; stalagmite; Dead Sea; Israel; Jerusalem [Israel]; Levant; Mediterranean Region; Poaceae

High-precision geochronology of the Early Cretaceous Yingcheng Formation and its stratigraphic implications for Songliao Basin, China - Wang, T.; Wang, C.; Ramezani, J.; Wan, X.; Yu, Z.; Gao, Y.; He, H.; Wu, H. (Geoscience Frontiers, 2022)
The Songliao Basin in Northeast Asia is the largest and longest-lived rift basin and preserves a near-continuous continental succession of the most of the Cretaceous period, providing great material to investigate the adaption of the terrestrial systems to the Cretaceous greenhouse climate and tectonic events. However, the paucity of precise and accurate radioisotopic ages from the Early Cretaceous strata of the Songliao Basin has greatly held back the temporal and causal correlation of the continental records to the global Early Cretaceous records. Three tuff layers intercalated in the Yingcheng Formation have been intercepted by the SK-2 borehole, which offer excellent materials for radioisotopic dating and calibration of the chronostratigraphy of the Lower Cretaceous sequence of Songliao Basin. Moreover, the Yingcheng Formation recorded the largest and the last of the two major volcanic events in Songliao Basin, which also represents a turning point in the basin evolution history of Songliao from syn-rift stage to post-rift stage. Here we report high-precision U –Pb zircon geochronology by the CA-ID-TIMS technique on three tuff samples from the Yingcheng Formation of the SK-2 borehole in the Songliao Basin to construct a greatly improved, absolute age framework for the Yingcheng Formation and provide crucial age constraints for the Songliao Lower Cretaceous Strata. The new CA-ID-TIMS geochronology constrained the Yingcheng Formation at 102.571 + 0.320/−2.346 Ma to ca. 113 Ma, correlating to the Albian Stage. Combined with the previous published Songliao geochronology, the Quantou Formation is constrained to between 96.442 + 0.475/−0.086 Ma and 91.923 + 0.475/−0.086 Ma; the Denglouku Formation is constrained to between 102.571 + 0.320/−2.346 Ma and 96.442 + 0.475/−0.086 Ma; the age of the Shahezi Formation is estimated at ca. 113 Ma to ca. 118 Ma, which could extend to ca. 125 Ma in some locations in Songliao Basin. The major unconformity between the Yingcheng Formation and the Denglouku Formation, which represents the transition of the basin from syn-rift to post-rift is thus confined to between 102.571 + 0.320/−2.346 Ma and 96.442 + 0.475/−0.086 Ma. This is roughly contemporaneous with the change in the direction of the paleo-Pacific plate motion from west-southwest to north or northwest in mid-Cretaceous, suggesting their possible connections. © 2022 China University of Geosciences (Beijing) and Peking University
cited By 3
Keywords: chronostratigraphy; correlation; Cretaceous; geochronology; precision; uranium-lead dating; China; Songliao Basin

High-resolution crustal structure in the Songliao basin [松辽盆地地壳精细结构研究] - Chunli, K.; Ruiqing, Z.; Chengfeng, C.; Jiadong, L. (Acta Seismologica Sinica, 2022)
High-resolution shallow crustal structure beneath the Songliao basin of Northeast （NE） China has obvious economic and scientific significance. To constrain the sediment and crustal structure of the Songliao basin，H-β grid search method based on wavefield downward continuation and decomposition is used with teleseismic data recorded from portable broadband seismic arrays in the NE China. The results show that the estimated sediment thickness is 0.2−2.5 km，and becomes thinner from the central depression toward the margin of the basin，with the thinnest sediment in the southwestern region. The crustal thickness varies from 24 km to 34 km，and its lateral variation correlates with the distribution of sedimentary thicknesses to a certain extent. The crustal stretching factor is calculated from the sedimentary and crustal thicknesses，with an average close to the lithospheric stretching estimation from previous receiver function studies. Thus，we infer that the thinning of the crust and lithosphere is dominated by pure shear mode during the extensional process of the Songliao basin. Moreover，the Songliao basin has a high crustal vP/vS ratio，indicating possible magmatic underplating during the lithospheric extension beneath the Songliao basin. © 2022 Acta Seismologica Sinica Press. All rights reserved.
cited By 0
Keywords: broadband data; crustal structure; crustal thickness; crustal thinning; decomposition analysis; extensional tectonics; lithospheric structure; P-wave; S-wave; sediment thickness; seismic survey; teleseismic wave; wave field; China; Songliao Basin

How was the Bushveld Complex assembled? A search for cryptic layering in ICDP drillcores from the Main Zone - Trumbull, Robert B; Veksler, Ilya V; Nikonov, Wilhelm; Rammlmair, Dieter (EGU General Assembly Conference Abstracts, 2022)

Hydrothermal regeneration of ammonium as a basin-scale driver of primary productivity - St{ueken, Eva E; Kirsim{ae, Kalle; Lepland, Aivo; Prave, Anthony R (Astrobiology, 2022)

Hyperthermal events recorded in the Palaeogene carbonate sequence of southern Gulf of Mexico–Santa Elena borehole, Yucatan Peninsula - Garc'ia-Garnica, E.M.; P'erez-Cruz, L. (Geological Journal, 2022)
Based on geochemical and magnetic susceptibility analyses, maximum warming events (hyperthermal) in the Palaeogene are recognized in the carbonate rocks of the Santa Elena borehole (SEB) in the Yucatan Peninsula, the Palaeocene-Eocene Thermal Maximum (PETM) and the Eocene Thermal Maximum 2 (ETM-2). The site records the continental shelf marine response during these global events. Major and trace element records (Al, Ba, Ca, Fe, K, Si, and Ti), Ca/Fe, Si/Al ratios, and magnetic susceptibility are used as proxies of terrigenous input, and Ba/Al ratio as a proxy of palaeoproductivity. The hyperthermal events are characterized by the dilution and/or dissolution of biogenic carbonates. The high input of terrigenous materials is linked to extreme precipitation, common during these warming events. Our records suggest a decrease in palaeoproductivity associated with a nutrients gradient in a shallow ecosystem, with deeper thermocline and stratified column water. The PETM is characterized by high eustatic sea-level conditions, with a high contribution of detrital material, indicating sedimentary condensation and marked increase in precipitation, calcite dilution and/or dissolution, and low productivity. The ETM-2 event is less extreme than the PETM, with high precipitation, although evaporation could also play an important role, as evidenced by the presence of evaporites in this interval. These changes might affect the higher trophic levels of the shelf sea ecosystem, declining productivity. The study contributes to our understanding of the global and regional effects of these past warming events and the future climate change. © 2021 John Wiley & Sons Ltd.
cited By 0

De-noising distributed acoustic sensing data using an adaptive frequency-wavenumber filter - Isken, Marius Paul; Vasyura-Bathke, Hannes; Dahm, Torsten; Heimann, Sebastian (Geophysical Journal International, 2022)

Fault associated with the 1967 M 6.3 Koyna earthquake, India: A review of recent studies and perspectives for further probing - Modak, Kunal; Rohilla, Sunil; Podugu, Nagaraju; Goswami, Deepjyoti; Roy, Sukanta (Journal of Asian Earth Sciences: X, 2022)

Hydrogen-rich gas discovery in continental scientific drilling project of Songliao Basin, Northeast China: new insights into deep Earth exploration - Han, S.; Tang, Z.; Wang, C.; Horsfield, B.; Wang, T.; Mahlstedt, N. (Science Bulletin, 2022)
cited By 4

Experimental Study on Physical Characteristics of Deep Rocks at Different Depths in Songliao Basin - Yang, Mingqing; He, Zhiqiang; Li, Cong; Yang, Bengao; Liu, Guikang; Fu, Chenghang; Wang, Tianyu; Wei, Zijie (Geofluids, 2022)
Deep earth science is the basic of deep resource exploitation, and the research on the physical and mechanical characteristics of deep rock is a research hotspot at present. In order to study the physical characteristics of deep rock at different depths, based on the cores at different depths of 4900-6830 m in Songke Well 2 (SK-2), Songliao Basin, this paper carried out the study including the rock characteristics of mineral, wave velocity, density, and pore, the variation law of physical characteristics of deep rock with depth is studied, and the relationship between different physical parameters of deep rocks is explored. It is found that the core composition minerals of SK-2 at the depth of 4900-6830 m vary greatly with the depth, in which the quality of hard phase minerals accounts for a large proportion. After entering the basement stratum, the mineral content of different phases tends to be close. With the increase of depth, the wave velocity, density, and dynamic elastic modulus of rocks show a linear increase trend, and there is a positive correlation between density and wave velocity. In the range of 4900-6830 m depth, the porosity generally shows a downward trend with the increase of depth. In the range of 6000-6830 m, the porosity tends to be close to 7% with the increase of depth, indicating that formation compaction has little impact on the development of igneous pores in this formation. There is a negative correlation between wave velocity and porosity, and the empirical formula is fitted. This study can provide a reference for the exploration of deep geoscience and deep engineering practice. © 2022 Mingqing Yang et al.
Keywords: China; Songliao Basin; density; depth; experimental study; mineral; physical property; porosity; rock property; wave velocity

Discovery and geological implications of the Early Cretaceous basaltic andesites in SK2 borehole; [? 科二井早白垩世早期玄武安山岩的 ? 现 ? 地质 ?] - Zhang, Zhao; Huang, Feng; Xu, Jifeng; Zeng, Yunchuan; Zhang, Liying; Yang, Xuli; Zhang, Man (Yanshi Xuebao/Acta Petrologica Sinica, 2022)
A continuous sedimentary-volcanic core of Songliao Basin has been obtained through ultra-deep drilling of the SK2 borehole, which provides excellent materials for systematically investigating the formation of the Songliao Basin and the tectonic evolution history of Northeast China. In this study, we conducted a combined study of zircon U-Pb dating, whole-rock geochemical and Sr-Nd isotopic analysis on basaltic andesite samples from SK2 borehole with depths ranging from -6035m to -6084m. These SK2 basaltic andesite samples belong to Huoshiling Formation and they were formed at Early Cretaceous (141.6±1.4Ma) according to the zircon U-Pb dating results. The SK2 basaltic andesites are enriched in large ion lithophile elements, depleted in high field strength elements, and their geochemical signatures are consistent with arc magmas. These rocks show depleted Sr-Nd isotope characteristics ((87Sr/86Sr)i=0.70496 0.70478, ϵNd(t)=1.05 1.61), suggesting a depleted mantle source. In the Early Cretaceous, the evolution of Northeast China was mainly controlled by the southward subduction of the Mongol-Okhotsk oceanic plate and the western subduction of the Paleo-Pacific Plate. Previous study has shown that the subduction of Mongolia-Okhotsk Ocean induced coeval magmatism in the Great Xing'an Range, however, it is not clear whether its influence extends into the Songliao Basin. The initial subduction of Paleo-Pacific lithosphere may induce Late Mesozoic magmatism in the west of Songliao Basin. The Early Cretaceous formation and evolution of Songliao Basin were mainly affected by the activities of Mongolia Okhotsk Ocean or Paleo-Pacific lithosphere remains controversial. The Th/Hf (1.10 2.87) and Zr/Y ratios (10.1 18.7) of the SK2 basaltic andesites are similar to the within-plate basaltic magmas, we therefore suggest that SK2 samples belong to intraplate magmatism. The samples also show higher Zr, Hf and Ti contents, higher Nb/Ta ratios and more depleted Nd isotope compositions than the coeval mafic rocks in the Great Xing'an Range, indicating the SK2 samples formed in a different tectonic background. Accordingly, the Early Cretaceous volcanic rocks in Songliao Basin are most likely occurred by rollback of the subducting Paleo-Pacific Plate, while incidental lithospheric extension may promote the formation of Songliao Basin. © 2022 Science Press. All rights reserved.
Keywords: Basalt; Binary alloys; Boreholes; Geochemistry; Geochronology; Lead alloys; Neodymium alloys; Strontium alloys; Tectonics; Uranium alloys; Zircon; Basaltic andesite; Early Cretaceous; Magmatisms; Northeast China; Okhotsk; Pacific plates; Rollback of the paleo-pacific plate; SK2 borehole; Songliao basin; Zircon U-Pb dating; Isotopes

Deep sourced fluids for peridotite carbonation in the shallow mantle wedge of a fossil subduction zone: Sr and C isotope profiles of OmanDP Hole BT1B - Obeso, Juan Carlos; Kelemen, Peter B; Leong, James M; Menzel, Manuel D; Manning, Craig E; Godard, Marguerite; Cai, Yue; Bolge, Louise; Party, Oman Drilling Project Phase 1 Science (Journal of Geophysical Research: Solid Earth, 2022)

Depositional history of Lake Chala (Mt. Kilimanjaro, equatorial East Africa) from high-resolution seismic stratigraphy - Maitituerdi, A.; Van Daele, M.; Verschuren, D.; De Batist, M.; Waldmann, N. (Journal of African Earth Sciences, 2022)
Sediments deposited in Lake Chala (Kenya/Tanzania) constitute a high-resolution archive of past climate and environmental change in equatorial East Africa spanning two glacial-interglacial cycles. To correctly interpret the proxy records it contains, it is crucial to understand the evolution of lacustrine sedimentation in this volcanic crater basin. Building on previous seismic stratigraphic analysis by Moernaut et al. (2010) of a dense grid of 37 km high-resolution seismic reflection profiles with up to 270 ms two-way travel time (ca. 210 m depth) of sub-bottom penetration, this study presents a seismic-based reconstruction of the complete depositional history of Lake Chala as well as a first-order age model for the major documented stages in lake evolution. The seismic stratigraphic sequence comprises 16 distinct and finely-stratified units (U1-U16, youngest to oldest), grouped into five major depositional stages. Stage I (U16, ca. 249-212 ka) marks the initiation of sedimentation in an originally ring-shaped depositional area surrounding two central tuff cones emerging from the basin floor. Stage II (U15-U12, ca. 212-114 ka) represents the onset of basinwide sedimentation above the tuff cones, implying a gradual rise in lake depth and shift to more strictly hemipelagic sedimentation. Stage III (U11-U8, ca. 114-97 ka) represents the development of a relatively flat lake floor during a period of significantly reduced lake depth. Stage IV (U7-U4, ca. 97 –20.5 ka) is again characterized by largely undisturbed hemipelagic sedimentation under mostly high lake-depth conditions. Stage V (U3-U1, 20.5 ka BP to Present) represents the establishment of the present-day, very broad and flat basin floor under fluctuating lake level. Reassessing the Moernaut et al. (2010) suggestion of a minor disconformity at ca. 100 m sub-bottom depth, we here interpret this seismic feature as a thick turbidite related to a mass wasting event. Consequently we can affirm continuity of lacustrine sedimentation in the depocenter of Lake Chala throughout the past ca. 250,000 years. © 2022 Elsevier Ltd
cited By 3
Keywords: deposition; environmental change; glacial-interglacial cycle; lacustrine deposit; lake; mass wasting; reconstruction; sediment; seismic stratigraphy; Kilimanjaro [Kilimanjaro (RGA)]; Kilimanjaro [Tanzania]; Tanzania

Deccan volcanic activity and its links to the end-Cretaceous extinction in northern China - Gu, X.; Zhang, L.; Yin, R.; Grasby, S.E.; Yao, H.; Tan, J.; Wang, C. (Global and Planetary Change, 2022)
The Cretaceous-Paleogene (K-Pg) boundary mass extinction is commonly attributed to the Chicxulub impact and/or the Deccan Traps (DT) volcanism, but the underlying trigger remains uncertain. The lack of detailed identification of the DT eruptive pluses impedes the full assessment of their relationship to the K-Pg boundary mass extinction. Here we present the first mercury (Hg) chemostratigraphy records on the paleo Asian plate, coupled with climatic and biotic data, to constrain the effects of the DT on the Late Cretaceous climate change and mass extinction. In northern China, a total Hg (THg) spike follows warming caused by the DT volcanism and corresponds to the significant species losses. Our study suggests that this most intense pulse of the DT ( 50 kyr duration) occurred just before the K-Pg boundary and suggests that it contributed to the end-Cretaceous mass extinction in northern China. © 2022 Elsevier B.V.
cited By 2
Keywords: Boundary mass; Chemostratigraphy; Deccan trap volcanism; End-cretaceous mass extinction; Hg chemostratigraphy; Hg isotope; K-pg boundaries; Mass extinction; Northern China; Volcanic activities; Climate change; chemostratigraphy; climate change; Cretaceous; Cretaceous-Paleogene boundary; Deccan Traps; mass extinction; volcanism; China

3D imaging of the subsurface electrical resistivity structure in West Bohemia/Upper Palatinate covering mofettes and Quaternary volcanic structures by using Magnetotellurics - Platz, Anna; Weckmann, Ute; Pek, Josef; Kov'ačikov'a, Světlana; Klanica, Radek; Mair, Johannes; Aleid, Basel (Tectonophysics, 2022)
The region of West Bohemia and Upper Palatinate belongs to the West Bohemian Massif. The study area is situated at the junction of three different Variscan tectonic units and hosts the ENE-WSW trending Ohře Rift as well as many different fault systems. The entire region is characterized by ongoing magmatic processes in the intra-continental lithospheric mantle expressed by a series of phenomena, including e.g. the occurrence of repeated earthquake swarms and massive degassing of mantle derived CO2 in form of mineral springs and mofettes. Ongoing active tectonics is mainly manifested by Cenozoic volcanism represented by different Quaternary volcanic structures. All these phenomena make the Ohře Rift a unique target area for European intra-continental geo-scientific research. With magnetotelluric (MT) measurements we image the subsurface distribution of the electrical resistivity and map possible fluid pathways. Two-dimensional (2D) inversion results by Muñoz et al. (2018) reveal a conductive channel in the vicinity of the earthquake swarm region that extends from the lower crust to the surface forming a pathway for fluids into the region of the mofettes. A second conductive channel is present in the south of their model; however, their 2D inversions allow ambiguous interpretations of this feature. Therefore, we conducted a large 3D MT field experiment extending the study area towards the south. The 3D inversion result matches well with the known geology imaging different fluid/magma reservoirs at crust-mantle depth and mapping possible fluid pathways from the reservoirs to the surface feeding known mofettes and spas. A comparison of 3D and 2D inversion results suggests that the 2D inversion results are considerably characterized by 3D and off-profile structures. In this context, the new results advocate for the swarm earthquakes being located in the resistive host rock surrounding the conductive channels; a finding in line with observations e.g. at the San Andreas Fault, California. © 2022 The Authors
Keywords: Bohemian Massif; Electric conductivity; Magnetotellurics; Strike-slip faults; Structural geology; Volcanoes; 2-d inversions; Conductive channels; Earthquake swarms; Fluid pathways; Fluid/magma reservoir; Inversion results; Magma reservoirs; Ohře rift; Study areas; Volcanic structures; earthquake swarm; electrical resistivity; magnetotelluric method; Quaternary; rift zone; three-dimensional modeling; volcanism; volcanology; Earthquakes

Depth wide distribution and metabolic potential of chemolithoautotrophic microorganisms reactivated from deep continental granitic crust underneath the Deccan Traps at Koyna, India - Mandal, Sunanda; Bose, Himadri; Ramesh, Kheerthana; Sahu, Rajendra Prasad; Saha, Anumeha; Sar, Pinaki; Kazy, Sufia Khannam (Frontiers in Microbiology, 2022)

Evidence of Carboniferous arc magmatism preserved in the Chicxulub impact structure - Ross, C.H.; Stockli, D.F.; Rasmussen, C.; Gulick, S.P.S.; Graaff, S.J.; Claeys, P.; Zhao, J.; Xiao, L.; Pickersgill, A.E.; Schmieder, M.; Kring, D.A.; Wittmann, A.; et al. (Bulletin of the Geological Society of America, 2022)
Determining the nature and age of the 200-km-wide Chicxulub impact target rock is an essential step in advancing our understanding of the Maya Block basement. Few age constraints exist for the northern Maya Block crust, specifically the basement underlying the 66 Ma, 200 km-wide Chicxulub impact structure. The International Ocean Discovery Program-International Continental Scientific Drilling Program Expedition 364 core recovered a continuous section of basement rocks from the Chicxulub target rocks, which provides a unique opportunity to illuminate the pre-impact tectonic evolution of a terrane key to the development of the Gulf of Mexico. Sparse published ages for the Maya Block point to Mesoproterozoic, Ediacaran, Ordovician to Devonian crust are consistent with plate reconstruction models. In con- trast, granitic basement recovered from the Chicxulub peak ring during Expedition 364 yielded new zircon U-Pb laser ablation-in-ductively coupled plasma-mass spectrometry (LA-ICP-MS) concordant dates clustering around 334 ± 2.3 Ma. Zircon rare earth element (REE) chemistry is consistent with the granitoids having formed in a continental arc setting. Inherited zircon grains fall into three groups: 400-435 Ma, 500-635 Ma, and 940-1400 Ma, which are consistent with the incorporation of Peri-Gondwanan, PanAfrican, and Grenvillian crust, respectively. Carboniferous U-Pb ages, trace element compositions, and inherited zircon grains indicate a pre-collisional continental volcanic arc located along the Maya Block’s northern margin before NW Gondwana collided with Laurentia. The existence of a continental arc along NW Gondwana suggests southward-directed subduction of Rheic oceanic crust beneath the Maya Block and is similar to evidence for a continental arc along the northern margin of Gondwana that is documented in the Suwannee terrane, Florida, USA, and Coahuila Block of NE M'exico. © 2022 Geological Society of America. All Rights Reserved.
cited By 9

Discing behavior and mechanism of cores extracted from Songke-2 well at depths below 4,500 m - Mingzhong, G.; Haichun, H.; Shouning, X.; Tong, L.; Pengfei, C.; Yanan, G.; Jing, X.; Bengao, Y.; Heping, X. (International Journal of Rock Mechanics and Mining Sciences, 2022)
Understanding in-situ stresses is the foundation for investigating deep rock mechanics. In practice, the fracture morphology of a disced core can often reflect its in-situ environment and disturbance-induced fracture process to some extent. In this study, three-dimensional dynamic scanning technology is used to reconstruct the fracture morphology of the disced cores extracted from Songke-2 as well as part of the Chinese Continental Scientific Drilling Project. The roughness of various regions of the fracture surfaces of the cores is investigated. Additionally, a parametric system is developed for the quantitative study of the integrity coefficient of the disced rock samples. Furthermore, the mechanisms and characteristics of the fractures along the stress paths are investigated. According to the findings, when shallow cores undergo discing, they have notable saddle-shaped coarse fractures, which may be related to the properties of the cores at these depths. Deep cores demonstrate discing behavior, but the generated discs are relatively thick. Deep core fracture surfaces are mostly smooth and straight, possibly propagating from the outside to the inside. Under excavation disturbance in the hydrostatic state, the extreme values of the maximum tensile stress at the core stubs show a saddle-shaped distribution. In general, the results of this study can serve as a theoretical foundation for the quantitative assessment of the intactness of disced cores. Furthermore, because disc patterns and characteristics are associated with stress states, this approach can be used to evaluate in-situ stress environments. © 2021 Elsevier Ltd
cited By 53
Keywords: Fracture; Morphology; Rock mechanics; Rocks; Stresses; Deep rocks; Discing; Fracture morphology; Fracture process; Fracture surfaces; Insitu stress; Integrity coefficient of disced rock sample; Integrity coefficients; Rock sample; Songke-2 well; Fractal dimension; fracture; in situ stress; rock mechanics; surface roughness; tensile stress

Diatom community responses to environmental change in Lake Ohrid (Balkan Peninsula) during the mid-Pleistocene Transition - Zaova, Dušica; Cvetkoska, Aleksandra; Wagner, Bernd; Francke, Alexander; Vogel, Hendrik; Levkov, Zlatko; Jovanovska, Elena (Quaternary International, 2022)

Drilling Overdeepened Alpine Valleys (ICDP-DOVE): Age, extent and environmental impact of Alpine glaciations - Anselmetti, Flavio; Buechi, Marius (EGU General Assembly Conference Abstracts, 2022)

Drilling Overdeepened Alpine Valleys (ICDP-DOVE): Quantifying the age, extent, and environmental impact of Alpine glaciations - Anselmetti, F.S.; Bavec, M.; Crouzet, C.; Fiebig, M.; Gabriel, G.; Preusser, F.; Ravazzi, C.; Ariztegui, D.; Beraus, S.; Brandt, A.-C.; Buechi, M.; Buness, H.; et al. (Scientific Drilling, 2022)
The sedimentary infill of glacially overdeepened valleys (i.e., structures eroded below the fluvial base level) is an excellent but yet underexplored archive with regard to the age, extent, and nature of past glaciations. The ICDP project DOVE (Drilling Overdeepened Alpine Valleys) Phase 1 investigates a series of drill cores from glacially overdeepened troughs at several locations along the northern front of the Alps. All sites will be investigated with regard to several aspects of environmental dynamics during the Quaternary, with focus on the glaciation, vegetation, and landscape history. Geophysical methods (e.g., seismic surveys), for example, will explore the geometry of overdeepened structures to better understand the process of overdeepening. Sedimentological analyses combined with downhole logging, analysis of biological remains, and state-of-the-art geochronological methods, will enable us to reconstruct the erosion and sedimentation history of the overdeepened troughs. This approach is expected to yield significant novel data quantifying the extent and timing of Middle and Late Pleistocene glaciations of the Alps. In a first phase, two sites were drilled in late 2021 into filled overdeepenings below the paleolobe of the Rhine Glacier, and both recovered a trough filling composed of multiphase glacial sequences. Fully cored Hole 5068_1_C reached a depth of 165m and recovered 10m molasse bedrock at the base. This hole will be used together with two flush holes (5068_1_A, 5068_1_B) for further geophysical cross-well experiments. Site 5068_2 reached a depth of 255m and bottomed out near the soft rock-bedrock contact. These two sites are complemented by three legacy drill sites that previously recovered filled overdeepenings below the more eastern Alpine Isar-Loisach, Salzach, and Traun paleoglacier lobes (5068_3, 5068_4, 5068_5). All analysis and interpretations of this DOVE Phase 1 will eventually lay the ground for an upcoming Phase 2 that will complete the pan-Alpine approach. This follow-up phase will investigate overdeepenings formerly occupied by paleoglacier lobes from the western and southern Alpine margins through drilling sites in France, Italy, and Slovenia. Available geological information and infrastructure make the Alps an ideal area to study overdeepened structures; however, the expected results of this study will not be restricted to the Alps. Such features are also known from other formerly glaciated mountain ranges, which are less studied than the Alps and more problematic with regards to drilling logistics. The results of this study will serve as textbook concepts to understand a full range of geological processes relevant to formerly glaciated areas all over our planet. © Copyright:
cited By 0
Keywords: Core drilling; Drills; Environmental impact; Geochronology; Glacial geology; Infill drilling; Landforms; Alpine valleys; Downholes; Drill core; Environmental dynamics; Fluvials; Geophysical methods; Phase 1; Sedimentary infill; Sedimentological analysis; Seismic surveys; Recovery

Ductile deformation during carbonation of serpentinized peridotite - Menzel, Manuel D.; Urai, Janos L.; Ukar, Estibalitz; Hirth, Greg; Schwedt, Alexander; Kovacs, Andras; Kibkalo, Lidia; Kelemen, Peter B. (NATURE COMMUNICATIONS, 2022)

Early Jurassic coprolites: insights into palaeobotany and the feeding behaviour of dinosaurs - Barbacka, Maria; G'orecki, Artur; Pacyna, Grzegorz; Pie'nkowski, Grzegorz; Philippe, Marc; B'oka, K'aroly; Ziaja, Jadwiga; Jarzynka, Agata; Qvarnstr{om, Martin; Niedźwiedzki, Grzegorz (Papers in Palaeontology, 2022)

Early Jurassic dinosaur-dominated track assemblages, floristic and environmental changes in the Holy Cross Mountains region, Poland - Pacyna, Grzegorz; Ziaja, Jadwiga; Barbacka, Maria; Pie'nkowski, Grzegorz; Jarzynka, Agata; Niedźwiedzki, Grzegorz (Geological Quarterly, 2022)

Earth’s oldest land ecosystem spotted in drilled cores - Voosen, P. (Science Advances, 2022)

Ecological resilience in tropical Andean lakes: A paleolimnological perspective - Benito, Xavier; Luethje, Melina; Schneider, Tobias; Fritz, Sherilyn C.; Baker, Paul A.; Pedersen, Eric J.; Ga{uzère, Pierre; Novaes Nascimento, Majoi; Bush, Mark; Ruhi, Albert (Limnology and Oceanography, 2022)
Little is known about whether changes in lake ecosystem structure over the past 150 years are unprecedented when considering longer timescales. Similarly, research linking environmental stressors to lake ecological resilience has traditionally focused on a few sentinel sites, hindering the study of spatially synchronous changes across large areas. Here, we studied signatures of paleolimnological resilience by tracking change in diatom community composition over the last 2000 years in four Ecuadorian Andean lakes with contrasting ecoregions. We focused on climate and anthropogenic change, and the type of biological responses that these changes induced: gradual, elastic, or threshold. We combined multivariate ordination techniques with nonlinear time-series methods (hierarchical generalized additive models) to characterize trajectories of community responses in each lake, and coherence in such trajectories across lakes. We hypothesized that remote, high-elevation lakes would exhibit synchronous trends due to their shared climatic constraints, whereas lower elevation lakes would show less synchronous trends as a consequence of human density and land-cover alteration. We found that gradual and elastic responses dominated. Threshold-type responses, or regime shifts, were only detected in the less remote lake, after a long period of gradual and elastic changes. Unexpected synchrony was observed in diatom assemblages from geographically distant and human-impacted lakes, whereas lakes under similar broad-scale environmental factors (climate and ecoregion) showed asynchronous community trajectories over time. Our results reveal a complex ecological history and indicate that Andean lakes in Ecuador can gradually adapt and recover from a myriad of disturbances, exhibiting resilience over century to millennial timescales. © 2021 Association for the Sciences of Limnology and Oceanography.
Keywords: Ecuador; anthropogenic effect; community composition; community response; diatom; ecosystem structure; lacustrine deposit; lacustrine environment; lake ecosystem; paleolimnology; tracking; tropical environment

Evidence from the Vredefort Granophyre Dikes points to crustal relaxation following basin-size impact cratering - Huber, M.S.; Kovaleva, E.; Clark, M.D.; Riller, U.; Fourie, F.D. (Icarus, 2022)
The timescale of the modification stage of basin-sized impact structures is not well understood. Owing to ca. 10 km of erosion since its formation, the Vredefort impact structure, South Africa, is an ideal testing ground for deciphering post-impact modification. Here, we present geophysical and geochemical evidence from the Vredefort Granophyre Dikes, which were derived from the - now eroded - Vredefort impact melt sheet. The dikes have been studied mostly in terms of their composition, while the timing and duration of their emplacement remain controversial. We examined the modern depth extent of five dikes, with three from the inner crystalline core of the central uplift, and two from the boundary between the core and the supracrustal collar of the central uplift, using two-dimensional electrical resistivity tomography. We found that the core dikes terminate near the present erosion surface (i.e., <5 m depth). In contrast, the dikes at the core-collar boundary extend to a depth ≥ 9 m. These observations suggest that the core dikes are exposed near their lowermost terminus. In addition, we obtained bulk geochemical composition of the dikes, finding that the andesitic composition phase is present in the core-collar dikes that is not found in the core dikes. The presence of this phase indicates the episodic emplacement of impact melt into subvertical crater floor fractures. We conclude that the dike formation was protracted and occurred over a time span of at least 104 years. The sequential formation of the Vredefort Granophyre Dikes points to horizontal extension of crust below the impact melt sheet above a kinematic velocity discontinuity, a crustal instability resulting from the dynamic collapse of the transient cavity. © 2021 Elsevier Inc.
cited By 1

Orthopyroxene-magnetite symplectite in olivine gabbros from the lower crustal Oman Ophiolite: Oman Drilling Project, Hole GT2A - Chatterjee, S.; Bandyopadhyay, D.; Takazawa, E.; Michibayashi, K. (Journal of Mineralogical and Petrological Sciences, 2021)
Oxidation states within the planetary interior are intrinsically linked with the broad scale tectonism; however, it is difficult to estimate the actual oxidation conditions. Orthopyroxene-magnetite symplectite formed by olivine oxidation may provide a significant clue into such oxidation events. Here we report detailed mineralogical and petrological synthesis of such orthopyroxene-magnetite symplectites from olivine gabbros of Oman Ophiolite (Hole GT2A, ICDP Oman Drilling Project). In order to understand how oxidation affects different olivine compositions, we employed a phase equilibria approach and computed several temperature-composition diagrams at a fixed pressure (1 kbar). Our experiments predict the coexistence of olivine with Fo75-76 and Fo71 with the orthopyroxene (En79 and En76), respectively, which is remarkably similar to the mineral chemistry obtained from the Oman lower crustal gabbros. From the magnetite content, we also infer that the symplectite formation may have taken place over a range of temperatures (600-1000 °C) via subsolidus olivine oxidation and/or melt (oxidizing)-olivine interaction. The latter is more probable, considering the partial occurrence of orthopyroxene and clinopyroxene rim adjacent to the symplectites. © 2021. All Rights Reserved.
cited By 0

Palynology from ground zero of the Chicxulub impact, southern Gulf of Mexico - Smith, V.; Warny, S.; Vellekoop, J.; Vajda, V.; Escarguel, G.; Jarzen, D.M. (Palynology, 2021)
Palynological analysis of Site M0077A in the Chicxulub impact crater has yielded a record of the immediate Cretaceous/Paleogene (K/Pg) recovery from ground zero of the end-Cretaceous mass extinction, followed by a record of the Paleocene –Eocene Thermal Maximum (PETM) and later Ypresian (Eocene), including the Early Eocene Climatic Optimum (EECO). Eight specimens of the dinoflagellate cyst Trithyrodinium evittii have been observed near the base of the K/Pg transitional unit; these likely represent a post-impact dinoflagellate disaster recovery assemblage deposited within several days following the impact, although the possibility that some or all of the T. evittii specimens are reworked Maastrichtian cysts cannot be fully excluded. Despite high-resolution sampling of the lowermost Paleocene successions, the oldest identifiable terrestrial palynomorphs observed in the Site M0077A core, two specimens of Deltoidospora fern spores, occur at least ∼200,000 years after the impact. Other than these occurrences, the Paleocene section is nearly barren in terms of palynomorphs, likely a result of poor preservation of organic material combined with a long recovery time for vegetation in the vicinity of the crater. Pollen and fungal spore concentrations spike in an anoxic dark shale deposited during the PETM around 56 Ma, with a diverse pollen assemblage indicating the presence of a coastal shrubby tropical forest in the geographic vicinity, likely in the Yucat'an Peninsula to the south. In the marine realm, this interval is characterized by thermophilic assemblages of dinoflagellate cysts. Stratigraphically constrained cluster analysis identified four statistically robust sample clusters in the lower Eocene successions, with Malvacipollis spp. and Milfordia spp. abundances driving the highest average dissimilarity between clusters. A second notable spike in palynological concentrations above the PETM section may represent another early Eocene hyperthermal event. Pollen and plant spore concentrations generally increased during the EECO, associated with increases in terrestrial input during basin infilling. © 2020 AASP –The Palynological Society.
cited By 3

Persistent orbital influence on millennial climate variability through the Pleistocene - Sun, Youbin; McManus, Jerry F.; Clemens, Steven C.; Zhang, Xu; Vogel, Hendrik; Hodell, David A.; Guo, Fei; Wang, Ting; Liu, Xingxing; An, ZhiSheng (Nature Geoscience, 2021)
Abundant evidence from marine, ice-core and terrestrial records demonstrates that Earth’s climate has experienced co-evolution of orbital- and millennial-scale variability through the Pleistocene. The varying magnitude of millennial climate variability (MCV) was linked to orbitally paced glacial cycles over the past 800 kyr. Before this interval, global glaciations were less pronounced but more frequent, yet scarcity of a long-term integration of high-resolution continental and marine records hampers our understanding of the evolution and dynamics of MCV before the mid-Pleistocene transition. Here we present a synthesis of four centennial-resolved elemental time series, which we interpret as proxies for MCV, from North Atlantic, Iberian margin, Balkan Peninsula (Lake Ohrid) and Chinese Loess Plateau. The proxy records reveal that MCV was pervasive and persistent over the mid-latitude Northern Hemisphere during the past 1.5 Myr. Our results suggest that the magnitude of MCV is not only strongly modulated by glacial boundary conditions on Earth after the mid-Pleistocene transition, but also persistently influenced by variations in precession and obliquity through the Pleistocene. The combination of these four proxies into a new MCV stack offers a credible reference for further assessing the dynamical interactions between orbital and millennial climate variability. © 2021, The Author(s), under exclusive licence to Springer Nature Limited.
Keywords: Atlantic Ocean; Atlantic Ocean (North); Balkans; China; Lake Ohrid; Loess Plateau; boundary condition; climate variation; glaciation; ice core; Northern Hemisphere; obliquity; Pleistocene

Petrographic and chemical studies of the Cretaceous-Paleogene boundary sequence at El Guayal, Tabasco, Mexico: Implications for ejecta plume evolution from the Chicxulub impact crater - Salge, T.; Tagle, R.; Schmitt, R.-T.; Hecht, L. (Special Paper of the Geological Society of America, 2021)
A combined petrographic and chemical study of ejecta particles from the Cretaceous- Paleogene boundary sequence of El Guayal, Tabasco, Mexico (520 km SW of Chicxulub crater), was carried out to assess their formation conditions and genetic relation during the impact process. The reaction of silicate ejecta particles with hot volatiles during atmospheric transport may have induced alteration processes, e.g., silicification and cementation, observed in the ejecta deposits. The various microstructures of calcite ejecta particles are interpreted to reflect different thermal histories at postshock conditions. Spherulitic calcite particles may represent carbonate melts that were quenched during ejection. A recrystallized microstructure may indicate short, intense thermal stress. Various aggregates document particleparticle interactions and intermixing of components from lower silicate and upper sedimentary target lithologies. Aggregates of recrystallized calcite with silicate melt indicate the consolidation of a hot suevitic component with sediments at > 750°C. Accretionary lapilli formed in a turbulent, steam-condensing environment at ∼100°C by aggregation of solid, ash-sized particles. Concentric zones with smaller grain sizes of accreted particles indicate a recurring exchange with a hotter environment. Our results suggest that during partial ejecta plume collapse, hot silicate components were mixed with the fine fraction of local surface-derived sediments, the latter of which were displaced by the preceding ejecta curtain. These processes sustained a hot, gas-driven, lateral basal transport that was accompanied by a turbulent plume at a higher level. The exothermic back-reaction of CaO from decomposed carbonates and sulfates with CO2 to form CaCO3 may have been responsible for a prolonged release of thermal energy at a late stage of plume evolution. © 2021, The Trustees of the Natural History Museum, London.
cited By 1

Phytoliths, pollen, and microcharcoal from the Baringo Basin, Kenya reveal savanna dynamics during the Plio-Pleistocene transition - Yost, Chad L.; Ivory, Sarah J.; Deino, Alan L.; Rabideaux, Nathan M.; Kingston, John D.; Cohen, Andrew S. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2021)
As part of the Hominin Sites and Paleolakes Drilling Project (HSPDP), phytoliths, pollen, and microcharcoal were examined from the 228 m (3.29 to 2.56 Ma) Baringo-Tugen Hills-Barsemoi drill core (BTB13). A total of 652 samples were collected at 10 to 32 cm intervals, corresponding to sub-millennial to millennial scale temporal resolution. Microcharcoal was well-preserved throughout the core and often peaked in abundance 5 kyr before and after insolation peaks. Phytolith preservation varied between excellent to total dissolution in alternating intervals throughout the core. Pollen was rarely preserved. These combined datasets indicate that prior to 3.1 Ma, woody cover fluctuated between open savanna (< 40% cover), woodland (40 –80% cover), and forest (> 80% cover) at typically precessional (19 –23 kyr) periodicities. During the mid-Piacenzian Warm Period (MPWP; 3.26 –3.01 Ma), intervals with exceptionally high microcharcoal abundance suggest that regional turnover from wooded to open habitats was driven in part by fire. After 3.1 Ma, low-elevation woody cover likely never exceeded 40%, with oscillations between mesic tall-grass vs. xeric short-grass savanna at precessional periodicities. Mesic C4 tall-grass (Panicoideae) peaked in abundance during insolation maxima, whereas xeric C4 short-grass (Chloridoideae) peaked during insolation minima. The onset of Northern Hemisphere glaciation (NHG) at 2.75 Ma coincided with the appearance of deep lake phases and increases in grass density and fire frequency. Spectral analysis and intervals with well-preserved phytoliths indicate that precession and interhemispheric insolation gradients influenced vegetation via their effects on equatorial precipitation and fire. This study fills a crucial gap in Pliocene vegetation reconstructions from the East African Rift Valley and its associated hominin localities. It also provides orbitally resolved regional vegetation data useful in paleodata –model comparisons for the onset of the MPWP (which is often used as an analog for future warming) and NHG. © 2020 Elsevier B.V.
Keywords: Baringo; East African Rift; Kenya; Tugen Hills; Chloridoideae; Panicoideae; abundance; glaciation; Northern Hemisphere; phytolith; Pliocene; Pliocene-Pleistocene boundary; pollen; precipitation (climatology); savanna; woodland

Planktonic diatom counts from Lake Ohrid core ICDP5045-1 (DEEP) - Cvetkoska, Aleksandra; Jovanovska, Elena (PANGAEA, 2021)
In 2013 a coring campaign was carried out as part of the project Scientific Collaboration on Past Speciation Conditions in Lake Ohrid (SCOPSCO) and under the umbrella of the International Continental Scientific Drilling Program (ICDP). A 584 m sediment succession was retrieved from the central part (DEEP site) of ancient Lake Ohrid at a water depth of 243 m. The upper 446.65 mcd that represent the entire lacustrine history back to ca. 1.363 Ma contain a remarkably well-preserved record, especially of planktonic diatoms. We here present the count data of planktonic diatoms from core ICDP5045-1 spanning the period from 1.363 Ma until present. Diatom count data were generated from 350 sediment samples taken at a temporal resolution of 2.0–4.0 ka and each slide was analysed across random transects to count 200–400 diatom valves.

Reconstructing two millennia of copper and silver metallurgy in the Lake Titicaca region (Bolivia/Peru) using trace metals and lead isotopic composition - Gu'edron, S.; Tolu, J.; Delaere, C.; Sabatier, P.; Barre, J.; Heredia, C.; Brisset, E.; Campillo, S.; Bindler, R.; Fritz, S.C.; Baker, P.A.; Amouroux, D. (Anthropocene, 2021)
Copper, silver, and gold exploitation has been a foundation of economic and socio-cultural development of Andean societies, at least for the last three millennia. The main centers of pre-colonial metallurgy are well-known from archeological artifacts, but temporal gaps inherent in this record handicap a finer understanding of the modalities of ore exploitation by succeeding civilizations. A continuous record over time of trace metals emitted during ore smelting operations make lake sediments excellent candidates to fill those gaps. Two millennia of metallurgy were reconstructed from atmospherically derived metals together with lead (Pb) isotope ratios in two dated sediment cores from Lake Titicaca. The first evidence for metallurgy is found during the apogee of the Tiwanaku state (AD 800 –1150), with a higher copper (Cu) accumulation that can be attributed to the smelting of local Cu ores, based on Pb isotopic fingerprinting. During the Late Intermediate Period (AD 1150 –1450), recorded peaks in metal deposition that persisted for ∼ twenty years show that mining activities were intensive but discontinuous. Pb isotope ratios suggest diversified extractive activities, mainly located in the southern part of the central Altiplano. Finally, the most intense mining epoch began during the Inca Empire (ca. AD 1500) and lasted until the end of the Colonial Period (AD 1830), with unprecedented metal deposition over this interval. Pb isotope fingerprinting shows that mining operations occurred mainly in the Lake Titicaca and Potosi areas and were responsible for metal emissions recorded in the entire Altiplano, as evidenced by other studies. © 2021 Elsevier Ltd
Keywords: South America; copper; extraction method; isotopic composition; lacustrine deposit; lead isotope; silver; trace metal

Pressure, temperature and lithological dependence of seismic and magnetic susceptibility anisotropy in amphibolites and gneisses from the central Scandinavian Caledonides - Bazargan, Mohsen; Motra, Hem Bahadur; Almqvist, Bjarne; Piazolo, Sandra; Hieronymus, Christoph (Tectonophysics, 2021)
As a petrofabric indicator, anisotropy of magnetic susceptibility (AMS) can potentially be used to infer seismic properties of rocks, and in particular seismic anisotropy. To evaluate the link between AMS and seismic anisotropy we present laboratory measurements of elastic wave velocities and anisotropy of magnetic susceptibility (AMS) for eight samples from the deep drilling investigation forming a part of the Collisional Orogeny in the Scandinavian Caledonides (COSC) project. The samples consist of a representative suite of mid crustal, deformed rock types, namely felsic and biotite-rich gneisses, and amphibolites (mafic gneisses). Compressional (P) and shear (S) waves were measured at confining pressures from room pressure to 600 MPa and temperature from room condition to 600 °C. Seismic anisotropy changes with increasing temperature and pressure, where the effect of pressure is more significant than temperature. Increasing pressure, considering the range of samples, results in an increase in mean wave speed values from 4.52 to 7.86 km/s for P waves and from 2.75 to 4.09 km/s for S waves. Biotite gneiss and amphibolite exhibit the highest anisotropy with P wave anisotropy (AVp) in the ranges of ~9% to ~20%, and maximum S- wave anisotropy exceeds 10%. In contrast, Felsic gneisses are significantly less anisotropic, with AVp of <7% and AVs of <6%. Up to 20% anisotropy may be generated by microcracks at 600 MPa and 600 °C, which is likely originating from thermal expansion of anisotropic minerals. An agreement is found between AMS and seismic anisotropy, although this is only a case if mean magnetic susceptibility (kmean) ranges between ~1 × 10−5 to ~1 × 10−3 [SI]. Such kmean values are common in rocks dominated by paramagnetic matrix minerals. Based on our results we propose that such samples are the most likely to be useful for the prediction of seismic anisotropy based on their AMS.
Keywords: Amphibolite; Anisotropy of magnetic susceptibility; Gneiss; Petrophysics; Scandinavian Caledonites; Seismic anisotropy

Proposed Drilling into Postglacial Faults: The P{arvie Fault System - Ask, Maria; Kukkonen, Ilmo; Olesen, Odleiv; Lund, Bj{orn; Fagereng, Åke; Rutqvist, Jonny; Rosberg, Jan-Erik; Lorenz, Henning (Cambridge University Press, 2021)

Provenance and paleogeography of Archean Fig Tree siliciclastic rocks in the East-Central Barberton Greenstone Belt, South Africa - Stoll, Emily; Drabon, Nadja; Lowe, Donald R. (Precambrian Research, 2021)

Quantifying the axial magma lens dynamics at the roof of oceanic magma reservoirs (dike/gabbro transition): Oman Drilling Project GT3 site survey - France, Lyderic; Lombard, Ma'eva; Nicollet, Christian; Berthod, Carole; Debret, Baptiste; Koepke, Juergen; Ildefonse, Benoit; Toussaint, Aurore (Journal of Geophysical Research: Solid Earth, 2021)
At oceanic spreading centers, the interactions between the igneous system that builds the crust, and the hydrothermal system that cools it govern the plumbing system architecture and its thermokinetic evolution. At fast-spreading centers, most of those interactions occur around the axial magma lens (AML) that feeds the upper crust, and possibly part of the underlying mushy igneous reservoir. Heat extracted from crystallizing AML is transferred through a conductive boundary layer to the overlying hydrothermal system. Quantifying the AML physical and thermal evolutions and its interactions with hydrothermal system is therefore essential to understand oceanic accretion. Those general issues were the rationale of drilling ICDP OmanDP Hole GT3A, and we present herein the geological, structural, and petrological data that were used as a site survey to select its location. GT3 area enables observations in three dimensions of fossilized AMLs and overlying dikes. The new field data and corresponding mineral compositions are used together with thermokinetic and thermodynamic models to deliver an integrated dynamic model for the AML/hydrothermal system interactions. Results attest that the isotropic gabbro interval is composite, with gabbro bodies intruding and reheating both gabbros and dikes (up to 1,040°C). We show that AMLs should be considered as transient igneous bodies that likely crystallize from primitive MORBs in decades, releasing heat to the intruded hosts, and feeding high temperature vents on the seafloor. We show for the first time that the thermal gradient recorded in AML roof is consistent with the heat fluxes reported at active hydrothermal vents. © 2021. The Authors.
cited By 5
Keywords: dike; drilling; gabbro; heat flux; hydrothermal system; hydrothermal vent; magma chamber; seafloor; spreading center; thermal evolution

Quaternary environmental changes in tropical Lake Towuti, Indonesia, inferred from end-member modelling of X-ray fluorescence core-scanning data - Morlock, Marina A.; Russell, James M.; Bijaksana, Satria (Journal of Quaternary Science, 2021)
Continental and marine sediments are composed of a mixture from different sources and are influenced by a variety of environmental factors and transport processes prior to deposition. For analysis and interpretation, these sources and processes are often challenging to disentangle. We show that end-member modelling of X-ray fluorescence (XRF) core-scanning data helps to overcome these challenges by unmixing different environmental signals from high-resolution sediment geochemical records. We apply this approach to a 100 m long lacustrine succession from Lake Towuti, Indonesia, to separate the regional climate and tectonic history from local ecological and diagenetic processes. The resulting six end-members (EMs) are interpreted to represent changes in ecological (EM1), climatic (EMs 2 –4), tectonic (EM 5) and geomorphic (EM6) processes determining changes in sediment composition. Because end-member analysis allows for the tracking of transient and overlapping processes, climatic changes can be followed throughout the 100 m-long succession, suggesting alternating wet and dry periods in Central Sulawesi over long (several 100 000 years) time scales. We show that end-member analysis on elemental data sets offers a detailed and objective means to disentangle depositional processes in sedimentary successions resulting from varying tectonic and environmental factors involved in sediment formation and deposition. © 2021 John Wiley & Sons, Ltd.
Keywords: Greater Sunda Islands; Lake Towuti; Malili Lakes; South Sulawesi; Sulawesi; Sunda Isles; data set; depositional environment; environmental change; geochemistry; marine sediment; Quaternary; sediment analysis; sediment transport; X-ray fluorescence

Rapid alteration of fractured volcanic conduits beneath Mt Unzen - Yilmaz, T.I.; Wadsworth, F.B.; Gilg, H.A.; Hess, K.-U.; Kendrick, J.E.; Wallace, P.A.; Lavall'ee, Y.; Utley, J.; Vasseur, J.; Nakada, S.; Dingwell, D.B. (Bulletin of Volcanology, 2021)
The nature of sub-volcanic alteration is usually only observable after erosion and exhumation at old inactive volcanoes, via geochemical changes in hydrothermal fluids sampled at the surface, via relatively low-resolution geophysical methods or can be inferred from erupted products. These methods are spatially or temporally removed from the real subsurface and thus provide only indirect information. In contrast, the ICDP deep drilling of the Mt Unzen volcano subsurface affords a snapshot into the in situ interaction between the dacitic dykes that fed dome-forming eruptions and the sub-volcanic hydrothermal system, where the most recent lava dome eruption occurred between 1990 and 1995. Here, we analyse drill core samples from hole USDP-4, constraining their degree and type of alteration. We identify and characterize two clay alteration stages: (1) an unusual argillic alteration infill of fractured or partially dissolved plagioclase and hornblende phenocryst domains with kaolinite and Reichweite 1 illite (70)-smectite and (2) propylitic alteration of amphibole and biotite phenocrysts with the fracture-hosted precipitation of chlorite, sulfide and carbonate minerals. These observations imply that the early clay-forming fluid was acidic and probably had a magmatic component, which is indicated for the fluids related to the second chlorite-carbonate stage by our stable carbon and oxygen isotope data. The porosity in the dyke samples is dominantly fracture-hosted, and fracture-filling mineralization is common, suggesting that the dykes were fractured during magma transport, emplacement and cooling, and that subsequent permeable circulation of hydrothermal fluids led to pore clogging and potential partial sealing of the pore network on a timescale of 9 years from cessation of the last eruption. These observations, in concert with evidence that intermediate, crystal-bearing magmas are susceptible to fracturing during ascent and emplacement, lead us to suggest that arc volcanoes enclosed in highly fractured country rock are susceptible to rapid hydrothermal circulation and alteration, with implications for the development of fluid flow, mineralization, stress regime and volcanic edifice structural stability. We explore these possibilities in the context of alteration at other similar volcanoes. © 2021, The Author(s).
cited By 5
Keywords: clay mineral; dike; emplacement; hydrothermal alteration; lava dome; permeability; porosity; volcanic arc; volcanic eruption; Japan; Kyushu; Nagasaki [Kyushu]; Unzen Volcano

Recurring types of variability and transitions in the ∼620 kyr record of climate change from the Chew Bahir basin, southern Ethiopia - Trauth, Martin H.; Asrat, Asfawossen; Cohen, Andrew S.; Duesing, Walter; Foerster, Verena; Kaboth-Bahr, Stefanie; Kraemer, K. Hauke; Lamb, Henry F.; Marwan, Norbert; Maslin, Mark A.; Sch{abitz, Frank (Quaternary Science Reviews, 2021)

Orientations of planar cataclasite zones in the Chicxulub peak ring as a ground truth for peak ring formation models - McCall, N.; Gulick, S.P.S.; Rae, A.S.P.; Poelchau, M.H.; Riller, U.; Lofi, J.; Morgan, J.V. (Earth and Planetary Science Letters, 2021)
Hypervelocity impact cratering is an important geologic process but the rarity of large terrestrial impact craters on Earth and the limited technical options to study cratering processes in the laboratory hinders our understanding of large-scale impact processes. Drill core recovered from the peak ring of the Chicxulub impact crater during International Ocean Discovery Program (IODP)/International Continental scientific Drilling Program (ICDP) Expedition 364 provides an opportunity to examine target rock deformation and thus, to assess cratering models in this regard. Using oriented computer tomography (CT) scans and line scan images of the core, we present the orientations of mm-to-cm-scale planar cataclasite and ultracataclasite zones in the deformed granitoid target rock of the peak ring. In the upper 470 m of the target rock, the cataclasite zones dip towards the crater center, whereas the dip directions for the ultracataclasite zones are approximately tangential to the peak ring. These two orientations are consistent with deformation expected from hydrocode-modeled principal stress directions for the outward movement of rocks as the transient crater develops, and the inward movement of rocks associated with collapse of the transient crater. Near the base of the core is a 96 m-thick interval of highly-deformed target rock with impact melt rock and rock fragments not observed elsewhere in the core; this interval has previously been interpreted as an imbricate thrust zone within the peak ring. The cataclasite zones below this thrust zone have different orientations than those in the 470 m-thick block above. This observation implies a differential rotation from the overlying block during the final stages of peak-ring formation. Our results support an acoustic fluidization process, wherein blocks that vibrate or slide relative to each other allow the target rock to flow during transient crater collapse, and that the size of coherent rock blocks increases over the course of crater modification as the target rock regains its cohesive strength and acoustic fluidization decreases. © 2021
cited By 1

Mineralogical evolution of the cretaceous strata in the songliao basin, northeastern china: Implications for thermal history and paleoenvironmental evolution - Dong, T.; Gao, Y.; Huang, H.; Tian, X.; Yang, Q.; Li, Y.; Niu, L.; Cao, Y. (Minerals, 2021)
The Songliao Basin in northeastern China is one of the largest and longest-lived Cretaceous sedimentary basins enriched in petroleum and geothermal resources worldwide. Although the modern Songliao Basin has a high geothermal gradient, the geological thermal history of the basin has not been well constrained. The SK-2 drilling program, as the second stage of the International Continental Drilling Project of Cretaceous Songliao Basin, is for recovering extensive Early Cretaceous terrestrial strata and providing valuable materials for decoding the mineralogical evolution and the paleoenvironmental changes. Here, we present whole-rock and clay mineralogical analysis on 72 core samples covering 3346 –5705 m of the Shahezi Formation in the SK-2 borehole. The whole-rock minerals mainly include clay minerals, quartz, plagioclase, as well as some calcite, K-feldspar, siderite, and pyrite. The clay mineral assemblages include illite, chlorite, and illite – smectite interlayer minerals. Above 4500 m, clay minerals are dominated by illite and illite –smectite interlayers. Below 4500 m, more plagioclase, K-feldspar, and calcite are present, while illite –smectite interlayers are completely replaced by illite. The whole-rock and clay mineralogical evolution of the Shahezi Formation is primarily controlled by thermal diagenesis, although paleoenvironmental change may act as a minor contribution. Combined with published data from the Upper Cretaceous in SK-1 cores, we infer that Cretaceous greenhouse climatic and environmental changes left finger-prints on whole-rock and clay mineralogical assemblages and that the Songliao Basin reached a maximum burial depth and a peak of thermal evolution at the end of the Cretaceous. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
cited By 2

Organic matter mineralization in modern and ancient ferruginous sediments - Friese, Andr'e; Bauer, Kohen; Glombitza, Clemens; Ordoñez, Luis; Ariztegui, Daniel; Heuer, Verena B.; Vuillemin, Aurèle; Henny, Cynthia; Nomosatryo, Sulung; Simister, Rachel; Wagner, Dirk; Bijaksana, Satria; et al. (Nature Communications, 2021)

Mid-Norwegian continental margin magmatism and Paleogene global climate change: An overview of the upcoming International Ocean Discovery Program (IODP) Expedition 396 - Planke, Sverre; Huismans, Ritske; Gernigon, Laurent; Buenz, Stefan; Faleide, Jan Inge; Jones, Morgan T; Svensen, Henrik H; Jerram, Dougal A; Millett, John M; et al. (EGU General Assembly Conference Abstracts, 2021)

Mapping the Chicxulub Impact Stratigraphy and Peak Ring Using Drilling and Seismic Data - Christeson, G.L.; Morgan, J.V.; Gulick, S.P.S. (Journal of Geophysical Research: Planets, 2021)
We integrate high-resolution full-waveform velocity models with seismic reflection images to map the peak ring and impactite stratigraphy at the Chicxulub structure. International Ocean Discovery Program/International Continental scientific Drilling Program Site M0077 provides ground truth for our interpretations. The peak ring is narrower (∼10 km width) where it is high relief (600 –700 m below seafloor) and wider (∼15 km width) where it is lower relief (1,000 –1,200 m below seafloor). Both target asymmetry and angle of impact could have contributed to observed differences in peak ring morphology. We interpret a layer of lowered velocities as a resurge layer formed from the ocean resurge, seiche, and returning tsunami flowing into the newly formed impact basin. This graded suevite layer has an average thickness of 187 ± 58 m with only local thickness differences within the annular trough, peak ring, and central basin. These observations suggest that the returning ocean was of substantial height and energetic enough to carry debris across the entire topographic peak ring. We map impact melt rock throughout the crater, with a thick impact melt sheet in the central basin (>500 m), thin intermittent melt rock capping the peak ring, and a ∼500-m thick layer of melt rock in the annular trough near the peak ring that thins toward the crater rim. We estimate that ∼70% –75% of the melt rock volume is in the central basin. We image features above and adjacent to the central basin melt sheet that we interpret as upflow zones associated with a long-lasting hydrothermal system. © 2021. American Geophysical Union. All Rights Reserved.
cited By 5

Response of the lacustrine flora in East Asia to global climate changes across the K/Pg boundary - Li, S.; Sanjuan, J.; Wang, Q.; Wan, X. (Global and Planetary Change, 2021)
The global climate during the latest Cretaceous became variable, with several global warming and cooling trends in a context of a greenhouse Earth. The responses of marine ecosystems to these climate events are relatively well known worldwide; however, lacustrine responses are poorly known due to the less frequent and discontinuous terrestrial fossil records. The relative changes in charophyte diversity in continuous lacustrine sedimentary sequences from two basins in East Asia, i.e., Songliao and Jiaolai, are considered here for the first time to establish their correlation with global climate changes during the Late Cretaceous and K/Pg boundary, compared with the well-studied south European Ibero-Armorican Island. Lacustrine deposits correlated with the Campanian –Maastrichtian Boundary Event (CMBE), related to a long cooling period provided a relatively low diversity in East Asia. In contrast, we detected a diverse charophyte flora in lacustrine deposits correlated with the Mid-Maastrichtian Event (MME) in East Asia in a global warming trend. A higher charophyte diversity was further found in the end-Cretaceous global warming event due to speciation under the background of latest Maastrichtian warming event (LMWE). During the LMWE, Characeae species such as Microchara cristata reduced its size significantly due to environmental stress probably related to the Deccan volcanism. On the other hand, a general tendency of increasing the gyrogonite size in new Characeae taxa has been detected in populations extracted from lower Danian deposits, probably related to stable palaeoenvironmental conditions in a global cooling context. This study represents the first attempt to correlate the response of the charophyte flora to global climate changes in permanent lacustrine systems during the three main Late Cretaceous –early Danian climatic turnovers. © 2020 Elsevier B.V.
cited By 2
Keywords: Deposits; Ecosystems; Global warming; Environmental stress; Global climate changes; Global climates; Lacustrine deposits; Lacustrine systems; Late cretaceous; Sedimentary sequence; Terrestrial fossils; Earth (planet); Characeae

Mechanical behavior of brittle-ductile transition in rocks at different depths; [深部不同深度岩石脆延转化力学行为研究] - Xie, Heping; Gao, Mingzhong; Fu, Chenghang; Lu, Yiqiang; Yang, Mingqing; Hu, Jianjun; Yang, Bengao (Meitan Xuebao/Journal of the China Coal Society, 2021)
The mechanical behavior of brittle-ductile transition in rocks is one of the essential components of deep rock mechanics, as well as a key factor that impacts the safe and efficient implementation of deep rock engineering projects.To study the differences in the mechanical behaviors of brittle-ductile transition in deep rocks, the sandstones, conglomerates and andesites at different occurrence depths (1 000-6 400 m) from the Songliao Basin are taken as research objects, and a number of conventional triaxial tests are carried out on rocks at an identical depth but under different stress levels, rocks at different depths but under an identical stress level, and rocks under different stress levels and at different depths.The brittleness characteristics of rocks are analyzed by using the pre-peak and the post-peak brittleness index.A preliminary understanding of the key influencing factors and differences in the mechanical behaviors of brittle-ductile transition in deep rocks at different depths has been achieved.The research results show that rather than an instantaneous brittle-ductile transition in rocks at different depths, a stress zone exists in progressive transition from brittleness to ductility.The brittleness of rocks at an identical depth but under different stress levels are mainly affected by the confining pressure.For sandstones at a depth of 1 600 m, its brittleness generally decreases with the increase of confining pressure, and there is a transition from its brittleness, ductility to strain hardening, its post-peak plasticity gradually increases until it shows a complete plasticity after the peak.The stress level range of 50 MPa to 70 MPa is the brittle-ductile transition zone of sandstones at the depth of 1 600 m.The brittle ductility characteristics of rocks at different depths under the same confining pressure are mainly affected by their own mineral components.For the rock samples from the Songliao Basin, their content of hard phase minerals and middle phase minerals generally increase with the increase of depths, which causes their brittleness to go up with depth increases, exhibiting a shallow to deep characteristic of transition from brittleness to ductility to brittleness.The post-peak characteristics of in-situ rock stress levels at different depths show different characteristics as the depth increases: the sandstones at depths from 1 000 m to 3 500 m depth show post-peak straining softening, post peak brittleness is found in sandstones at the depth of 4 800 m and conglomerates from depths at 5 100 m to 5 600 m, while the andesites at the depth of 6 400 m manifest the characteristic of post-peak plastic flow.Many factors affect the brittleness and ductility of rocks.Among them, game phenomenon exists in the impact on the brittleness and ductility of rocks between the mineral composition and stress environment.As the depth increases, the increase of hard phase minerals and middle phase minerals will cause the brittleness to increase, and the increase in the loading stress level will inhibit the brittleness of the rocks.The research results are expected to guide the scientific explorations and efficient implementation of the deep rock engineering. © 2021, Editorial Office of Journal of China Coal Society. All right reserved.
Keywords: Brittleness; Ductility; Fracture mechanics; Mineral exploration; Plasticity; Plastics industry; Rock mechanics; Rock pressure; Sandstone; Strain; Strain hardening; Stress analysis; Brittle ductile transitions; Brittle-ductile transition zone; Brittleness and ductility; Conventional triaxial test; Ductility characteristics; Efficient implementation; Key influencing factors; Scientific exploration; Minerals

Mesozoic –Cenozoic tectonic evolution and dynamics of the Songliao Basin, NE Asia: Implications for the closure of the Paleo-Asian Ocean and Mongol-Okhotsk Ocean and subduction of the Paleo-Pacific Ocean - Li, Zhong-Quan; Chen, Jun-Liang; Zou, Hao; Wang, Cheng-Shan; Meng, Qi-An; Liu, Heng-Lin; Wang, Shi-Ze (Earth-Science Reviews, 2021)

Micro-X-ray fluorescence (µXRF) analysis of proximal impactites: High-resolution element mapping, digital image analysis, and quantifications - Kaskes, P.; D'ehais, T.; Graaff, S.J.; Goderis, S.; Claeys, P. (Special Paper of the Geological Society of America, 2021)
Quantitative insights into the geochemistry and petrology of proximal impactites are fundamental to understand the complex processes that affected target lithologies during and after hypervelocity impact events. Traditional analytical techniques used to obtain major- and trace-element data sets focus predominantly on either destructive whole-rock analysis or laboratory-intensive phase-specific micro-analysis. Here, we present micro –X-ray fluorescence (µXRF) as a state-of-the-art, time-efficient, and nondestructive alternative for major- and trace-element analysis for both small and large samples (up to 20 cm wide) of proximal impactites. We applied µXRF element mapping on 44 samples from the Chicxulub, Popigai, and Ries impact structures, including impact breccias, impact melt rocks, and shocked target lithologies. The µXRF mapping required limited to no sample preparation and rapidly generated high-resolution major- and trace-element maps ( 1 h for 8 cm2, with a spatial resolution of 25 µm). These chemical distribution maps can be used as qualitative multi-element maps, as semiquantitative single-element heat maps, and as a basis for a novel image analysis workflow quantifying the modal abundance, size, shape, and degree of sorting of segmented components. The standardless fundamental parameters method was used to quantify the µXRF maps, and the results were compared with bulk powder techniques. Concentrations of most major elements (Na2O-CaO) were found to be accurate within 10% for thick sections. Overall, we demonstrate that μXRF is more than only a screening tool for heterogeneous impactites, because it rapidly produces bulk and phase-specific geochemical data sets that are suitable for various applications within the earth sciences. © 2021 The Authors.
cited By 10

Microbial Sulfur Isotope Fractionation in the Chicxulub Hydrothermal System - Kring, D.A.; Whitehouse, M.J.; Schmieder, M. (Astrobiology, 2021)
Target lithologies and post-impact hydrothermal mineral assemblages in a new 1.3 km deep core from the peak ring of the Chicxulub impact crater indicate sulfate reduction was a potential energy source for a microbial ecosystem (Kring et al., 2020). That sulfate was metabolized is confirmed here by microscopic pyrite framboids with δ34S values of -5 to -35 ‰ and ΔSsulfate-sulfide values between pyrite and source sulfate of 25 to 54 ‰, which are indicative of biologic fractionation rather than inorganic fractionation processes. These data indicate the Chicxulub impact crater and its hydrothermal system hosted a subsurface microbial community in porous permeable niches within the crater's peak ring. © David A. Kring et al., 2021; Published by Mary Ann Liebert, Inc. 2021.
cited By 10

Middle Pleistocene to recent diatoms and stratigraphy of the Magadi Basin, south Kenya Rift - Muiruri, Veronica M.; Owen, Richard Bernhart; Cort, Gijs; Renaut, Robin W.; Rabideaux, Nathan M.; Lowenstein, Tim K.; Leet, Kennie; Sier, Mark; Cohen, Andrew; Deocampo, Dan; Campisano, Christopher J.; Billingsley, Anne; et al. (Journal of Paleolimnology, 2021)

Organic carbon burial is paced by a ∼173-ka obliquity cycle in the middle to high latitudes - Huang, H.; Gao, Y.; Ma, C.; Jones, M.M.; Zeeden, C.; Ibarra, D.E.; Wu, H.; Wang, C. (Science Advances, 2021)
Earth's climate system is complex and inherently nonlinear, which can induce some extraneous cycles in paleoclimatic proxies at orbital time scales. The paleoenvironmental consequences of these extraneous cycles are debated owing to their complex origin. Here, we compile high-resolution datasets of total organic carbon (TOC) and stable carbon isotope (δ13Corg) datasets to investigate organic carbon burial processes in middle to high latitudes. Our results document a robust cyclicity of ∼173 thousand years (ka) in both TOC and δ13Corg. The ∼173-ka obliquity-related forcing signal was amplified by internal climate feedbacks of the carbon cycle under different geographic and climate conditions, which control a series of sensitive climatic processes. In addition, our new and compiled records from multiple proxies confirm the presence of the obliquity amplitude modulation (AM) cycle during the Mesozoic and Cenozoic and indicate the usefulness of the ∼173-ka cycle as geochronometer and for paleoclimatic interpretation. Copyright © 2021 The Authors, some rights reserved.
cited By 18
Keywords: Earth (planet); Orbits; Climate condition; Climatic process; High-resolution datasets; Internal climate; Multiple proxies; Organic carbon burial; Stable carbon isotopes; Total Organic Carbon; Organic carbon

Modeling the Magnetic Anomaly of the Bosumtwi (Ghana) Complex Meteorite Crater by Taking Into Account the Impact Demagnetization and Morphological Features - Kuzmicheva, M. Yu.; Ivanov, B.A. (Izvestiya, Physics of the Solid Earth, 2021)
Abstract–The formation of impact craters on the Earth’s surface is accompanied by the effect of shock waves on rocks. The shock wave compression results in rocks heating up to the point of melting and evaporation during unloading. The direct mechanical action of shock compression and residual heating change the magnetic properties of rocks. Geophysical modeling is used to determine the sources of the magnetic anomaly by interpreting the fields measured on the surface, but such modeling does not take into account the impact demagnetization of rocks. This work gives an example of analysis of the magnetic anomaly over the well-studied Bosumtwi crater (Ghana, 10.5 km diameter, 1 million years old), including the numerical modeling of the crater formation process and the construction of a magnetic anomaly model based on the simulated shock compression parameters and crater drilling data. It is shown that the morphological features of the crater– the crater rim and the central uplift–form positive magnetic anomalies around and inside the crater. © 2021, Pleiades Publishing, Ltd.

Multiband Wavelet Age Modeling for a ∼293 m (∼600 kyr) Sediment Core From Chew Bahir Basin, Southern Ethiopian Rift - Duesing, Walter; Berner, Nadine; Deino, Alan L.; Foerster, Verena; Kraemer, K. Hauke; Marwan, Norbert; Trauth, Martin H. (Frontiers in Earth Science, 2021)

New data from ICDP borehole SK2 and its constraint on the beginning of the Lower Cretaceous Shahezi Formation in the Songliao Basin, NE China - Liu, H.; Wang, P.; Gao, Y.; Hou, H.; Yin, Y.; Li, H.; Feng, Y. (Science Bulletin, 2021)
cited By 8

Northern Hemisphere Glaciation, African climate and human evolution - Trauth, Martin H.; Asrat, Asfawossen; Berner, Nadine; Bibi, Faysal; Foerster, Verena; Grove, Matt; Kaboth-Bahr, Stefanie; Maslin, Mark A.; Mudelsee, Manfred; Sch{abitz, Frank (Quaternary Science Reviews, 2021)

Ocean resurge-induced impact melt dynamics on the peak-ring of the Chicxulub impact structure, Mexico - Schulte, F.M.; Wittmann, A.; Jung, S.; Morgan, J.V.; Gulick, S.P.S.; Kring, D.A.; Grieve, R.A.F.; Osinski, G.R.; Riller, U.; Bralower, T.J.; Chenot, E.; Christeson, G.L.; et al. (International Journal of Earth Sciences, 2021)
Core from Hole M0077 from IODP/ICDP Expedition 364 provides unprecedented evidence for the physical processes in effect during the interaction of impact melt with rock-debris-laden seawater, following a large meteorite impact into waters of the Yucat'an shelf. Evidence for this interaction is based on petrographic, microstructural and chemical examination of the 46.37-m-thick impact melt rock sequence, which overlies shocked granitoid target rock of the peak ring of the Chicxulub impact structure. The melt rock sequence consists of two visually distinct phases, one is black and the other is green in colour. The black phase is aphanitic and trachyandesitic in composition and similar to melt rock from other sites within the impact structure. The green phase consists chiefly of clay minerals and sparitic calcite, which likely formed from a solidified water –rock debris mixture under hydrothermal conditions. We suggest that the layering and internal structure of the melt rock sequence resulted from a single process, i.e., violent contact of initially superheated silicate impact melt with the ocean resurge-induced water –rock mixture overriding the impact melt. Differences in density, temperature, viscosity, and velocity of this mixture and impact melt triggered Kelvin –Helmholtz and Rayleigh –Taylor instabilities at their phase boundary. As a consequence, shearing at the boundary perturbed and, thus, mingled both immiscible phases, and was accompanied by phreatomagmatic processes. These processes led to the brecciation at the top of the impact melt rock sequence. Quenching of this breccia by the seawater prevented reworking of the solidified breccia layers upon subsequent deposition of suevite. Solid-state deformation, notably in the uppermost brecciated impact melt rock layers, attests to long-term gravitational settling of the peak ring. © 2021, The Author(s).
cited By 4

Orbital- and Millennial-Scale Changes in Lake-Levels Facilitate Earthquake-Triggered Mass Failures in the Dead Sea Basin - Lu, Yin; Moernaut, Jasper; Waldmann, Nicolas; Bookman, Revital; Ian Alsop, G.; Hubert-Ferrari, Aur'elia; Strasser, Michael; Agnon, Amotz; Marco, Shmuel (Geophysical Research Letters, 2021)

Residual liquid from deep magma ocean crystallization in the source of komatiites from the ICDP drill core in the Barberton Greenstone Belt - Boyet, M.; Garçon, M.; Arndt, N.; Carlson, R.W.; Konc, Z. (Geochimica et Cosmochimica Acta, 2021)
Komatiites and sedimentary rocks sampled during the International Continental Drilling Program (BARB1-2 –3-4 –5) in the Barberton greenstone belt, South Africa, were analyzed for 146Sm-142Nd systematics. Resolved negative μ142Nd values (down to −7.7 ± 2.8) were identified in komatiites from the 3.48 Ga Komati Formation and this signature correlates with low Hf/Sm ratios measured in these samples. The negative μ142Nd point to a source with subchondritic Sm/Nd ratio which formed during the Hadean. No analytically resolvable 142Nd anomalies were measured in crustal detritus-rich, Si-rich, Ca-Fe-rich sediments and cherts from the Buck Reef (3.42 Ga) and the Fig Tree Group (3.23 –3.28 Ga). Our new measurements are incorporated into a larger set of 147Sm-143Nd and 176Lu-176Hf data to better understand the 142,143Nd-176Hf isotope signatures in the mantle source at the time of komatiite crystallization. Our calculations show that the 142,143Nd-176Hf isotope signatures and Hf/Sm ratios cannot be produced by recycling into the komatiite source of detrital sediments like those sampled in the Barberton area. Only cherts have the required trace element characteristics – low Hf/Sm, radiogenic ε176Hf –but the trace element concentrations in the cherts are so low that unrealistic amounts of chert would need to be added. We propose a four-stage model for the formation of these rocks. Negative μ142Nd and low Hf/Sm ratios developed during the crystallization of a deep magma ocean soon after Earth accretion. The material that ultimately became the source of komatiites was a residual liquid produced by 50% crystallization leaving a bridgmanite/ferropericlase/Ca-perovskite cumulate. The Lu-Hf and Sm-Nd isotope systems were decoupled at this stage. After extinction of 146Sm around 4 Ga, parent/daughter ratios fractionated during a melt extraction event. With this model we explain the positive ε176Hf and slightly negative ε143Nd in these samples. The 3.55 Ga Schapenburg komatiites in another part of the Barberton belt share similar chemical signatures, supporting our model of fractionation in a deep magma ocean early in Earth's history. © 2021 Elsevier Ltd
Keywords: Barberton Greenstone Belt; crystallization; detrital deposit; drilling; Hadean; isotopic ratio; komatiite; magma; mantle source; neodymium isotope; samarium

Textural and geochemical window into the IDDP-1 rhyolitic melt, Krafla, Iceland, and its reaction to drilling - Saubin, E.; Kennedy, B.; Tuffen, H.; Nichols, A.R.L.; Bindeman, I.; Mortensen, A.; Schipper, C.I.; Wadsworth, F.B.; Watson, T.; Zierenberg, R. (Bulletin of the Geological Society of America, 2021)
The unexpected intersection of rhyolitic magma and retrieval of quenched glass particles at the Iceland Deep Drilling Project-1 geothermal well in 2009 at Krafla, Iceland, provide unprecedented opportunities to characterize the genesis, storage, and behavior of subsurface silicic magma. In this study, we analyzed the complete time series of glass particles retrieved after magma was intersected, in terms of distribution, chemistry, and vesicle textures. Detailed analysis of the particles revealed them to represent bimodal rhyolitic magma compositions and textures. Early-retrieved clear vesicular glass has higher SiO2, crystal, and vesicle contents than later-retrieved dense brown glass. The vesicle size and distribution of the brown glass also reveal several vesicle populations. The glass particles vary in δD from −120‰ to −80‰ and have dissolved water contents spanning 1.3−2 wt%, although the majority of glass particles exhibit a narrower range. Vesicular textures indicate that volatile overpressure release predominantly occurred prior to late-stage magma ascent, and we infer that vesiculation occurred in response to drilling-induced decompression. The textures and chemistry of the rhyolitic glasses are consistent with variable partial melting of host felsite. The drilling recovery sequence indicates that the clear magma (lower degree partial melt) overlays the brown magma (higher degree partial melt). The isotopes and water species support high temperature hydration of these partial melts by a mixed meteoric and magmatic composition fluid. The textural evidence for partial melting and lack of crystallization imply that magma production is ongoing, and the growing magma body thus has a high potential for geothermal energy extraction. In summary, transfer of heat and fluids into felsite triggered variable degrees of felsite partial melting and produced a hydrated rhyolite magma with chemical and textural heterogeneities that were then enhanced by drilling perturbations. Such partial melting could occur extensively in the crust above magma chambers, where complex intrusive systems can form and supply the heat and fluids required to re-melt the host rock. Our findings emphasize the need for higher resolution geophysical monitoring of restless calderas both for hazard assessment and geothermal prospecting. We also provide insight into how shallow silicic magma reacts to drilling, which could be key to future exploration of the use of magma bodies in geothermal energy. © 2021 Geological Society of America
cited By 2
Keywords: Chemical analysis; Geothermal power plants; Geothermal prospecting; Geothermal wells; Glass; Hydration; Infill drilling; Melting; Particle size analysis; Silica; Textures; Geophysical monitoring; Glass particles; Hazard Assessment; High temperature; Higher resolution; Iceland deep drilling projects; Rhyolitic melts; Textural heterogeneities; Geothermal energy; drilling; geochemistry; glass; magma; melt; rhyolite; texture; time series analysis; Iceland; Krafla

Review of recent drilling projects in unconventional geothermal resources at campi flegrei caldera, cornubian batholith and williston sedimentary basin - Somma, Renato; Blessent, Daniela; Raymond, Jasmin; Constance, Madeline; Cotton, Lucy; De Natale, Giuseppe; Fedele, Alessandro; Jurado, Maria Jose; Marcia, Kirsten; Miranda, Mafalda; Troise, Claudia; Wiersberg, Thomas (Energies, 2021)
Unconventional geothermal resource development can contribute to increase power generation from renewable energy sources in countries without conventional hydrothermal reservoirs, which are usually associated with magmatic activity and extensional faulting, as well as to expand the generation in those regions where conventional resources are already used. Three recent drilling experiences focused on the characterization of unconventional resources are described and compared: the Campi Flegrei Deep Drilling Project (CFDDP) in Italy, the United Downs Deep Geothermal Power (UDDGP) project in the United Kingdom, and the DEEP Earth Energy Production in Canada. The main aspects of each project are described (geology, drilling, data collection, communication strategies) and compared to discuss challenges encountered at the tree sites considered, including a scientific drilling project (CFDDP) and two industrial ones (UDDGP and DEEP). The first project, at the first stage of pilot hole, although not reaching deep supercritical targets, showed extremely high, very rare thermal gradients even at shallow depths. Although each project has its own history, as well as social and economic context, the lessons learned at each drilling site can be used to further facilitate geothermal energy development. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
Keywords: Geothermal fields; Geothermal power plants; Renewable energy resources; Resource valuation; Trees (mathematics); Communication strategy; Energy development; Energy productions; Extensional faulting; Geothermal resources; Power generation from renewable; Scientific drilling; Unconventional resources; Infill drilling

Update on the Bushveld ICDP (BVDP) project - Ashwal, L; Roelofse, F; Trumbull, R; Webb, S; Khoza, D (Geobulletin, 2021)

The paleohydrological implications of aragonite precipitation under contrasting climates in the endorheic Dead Sea and its precursors revealed by experimental investigations - Ben Dor, Yoav; Flax, Tomer; Levitan, Itamar; Enzel, Yehouda; Brauer, Achim; Erel, Yigal (Chemical Geology, 2021)

The Rise and Fall of Wiñaymarka: Rethinking Cultural and Environmental Interactions in the Southern Basin of Lake Titicaca - Bruno, Maria C.; Capriles, Jos'e M.; Hastorf, Christine A.; Fritz, Sherilyn C.; Weide, D. Marie; Domic, Alejandra I.; Baker, Paul A. (Human Ecology, 2021)
Investigations of how past human societies managed during times of major climate change can inform our understanding of potential human responses to ongoing environmental change. In this study, we evaluate the impact of environmental variation on human communities over the last four millennia in the southern Lake Titicaca basin of the Andes, known as Lake Wiñaymarka. Refined paleoenvironmental reconstructions from new diatom-based reconstructions of lake level together with archaeological evidence of animal and plant resource use from sites on the Taraco Peninsula, Bolivia, reveal frequent climate and lake-level changes within major cultural phases. We posit that climate fluctuations alone do not explain major past social and political transformations but instead that a highly dynamic environment contributed to the development of flexible and diverse subsistence practices by the communities in the Titicaca Basin. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
Keywords: Lake Titicaca; Peru; Bacillariophyta; archaeological evidence; climate variation; economic diversification; environmental change; Holocene; human settlement; hydrological change; lake water; nature-society relations; paleoclimate; paleoenvironment; subsistence; water level

The shape and infill of the Basadingen overdeepened glacial valley from P-wave seismic reflections - Brandt, Anna-Catharina; Tanner, David C; Buness, Hermann; Burschil, Thomas; Gabriel, Gerald (EGU General Assembly Conference Abstracts, 2021)

The use of VSP techniques for fault zone characterization: An example from the San Andreas Fault - Chavarria, A.J.; Goertz, A.; Karrenbach, M.; Paulsson, B.; Milligan, P.; Soutyrine, V.; Hardin, A.; Dushman, D.; LaFlame, L. (The Leading Edge, 2021)
Vertical seismic profiling (VSP) technology is increasingly being used in the fields of earthquake seismology and tectonics. This is motivated in part by the growing number of oil field microseismic monitoring surveys, but more so by projects that involve drilling deep wells for monitoring crustal activity at depth. Examples of these projects are the San Andreas Fault Observatory at Depth (SAFOD), the Nankai Trough Seismogenic Zone Experiment, the Gulf of Corinth Rift Laboratory, and the Taiwan Chelungpu Fault Drilling Project, and other projects by the International Continental and Ocean Drilling Programs (ICDP and IODP). These projects require instrumentation and surveying in deep and possibly hot borehole environments. With higher resolution than surface seismic data, images from 2D and 3D VSP data contribute to better characterization and interpretation of complex reservoirs at smaller scales. The location of receivers in the low-noise borehole environment yields higher signal-to-noise ratios, higher frequency content due to less detrimental propagation effects from the overburden, and direct correlation of data at seismic frequencies with well logs. © 2007 Society of Exploration Geophysicists.
cited By 13
Keywords: Boreholes; Earthquakes; Monitoring; Oil fields; Oil well drilling; Tectonics; Earthquake seismology; Fault zone; Oil field microseismic monitoring surveys; Vertical seismic profiling (VSP); Seismology; borehole; fault zone; Ocean Drilling Program; oil field; San Andreas Fault; seismic data; seismology; vertical seismic profile; Gulf of Corinth; Ionian Sea; Mediterranean Sea; Nankai Trough; Pacific Ocean

Timing of deformation, metamorphism and leucogranite intrusion in the lower part of the Seve Nappe Complex in central J{amtland, Swedish Caledonides - Li, Yuan; Gee, David G.; Ladenberger, Anna; Sj{ostr{om, Håkan (GFF, 2021)
Recent studies in the context of the International Continental Scientific Drilling Project “Collisional Orogeny in the Scandinavian Caledonides” have focused on the importance of the Seve Nappe Complex (SNC) for understanding the subduction history of the Baltoscandian margin during closure of the Iapetus Ocean. In the classical Åre area of western central J{amtland, granulite facies migmatites and leucogranites of the Åreskutan Nappe provide evidence of Early Silurian (c. 440 Ma) high temperature metamorphism and a previous prograde, ultra-high pressure history, with microdiamonds. New LA-ICPMS zircon isotope age investigations of the underlying amphibolite facies Lower Seve Nappes, reported here, have also identified an Early Silurian tectonothermal history with pegmatitic leucogranite (c. 443 Ma) and, at lower structural levels, another felsic intrusion of earliest Middle Ordovician age (c. 469 Ma). The latter intrudes isoclinally folded host rock amphibolites and calcareous psammitic paragneisses and is itself tightly folded. Zircons in an amphibolite proved to be highly discordant but indicate Early Silurian metamorphism during isoclinal folding. Detrital zircons in a paragneiss are dominated by Sveconorwegian populations, but also include a range of younger Neoproterozoic grains down to the Early Ediacaran (c. 600 Ma). This new evidence of early Caledonian deformation and metamorphism indicates that, as farther north in the orogen, the Seve tectonothermal history in central J{amtland probably started early in the Ordovician, or before. Subduction and accretion along the Baltoscandian outer margin occurred prior to Scandian continent-continent collision, with Siluro-Devonian emplacement of the SNC across the foreland basins onto the Baltoscandian platform.
Publisher: Taylor & Francis _eprint: https://doi.org/10.1080/11035897.2020.1858341
Keywords: Scandinavian Caledonides; amphibolite; hf isotopes; leucogranite; lower Seve; paragneiss; u-Pb geochronology

U-Pb zircon geochronology and depositional age models for the Upper Triassic Chinle Formation (Petrified Forest National Park, Arizona, USA): Implications for Late Triassic paleoecological and paleoenvironmental change - Rasmussen, C.; Mundil, R.; Irmis, R.B.; Geisler, D.; Gehrels, G.E.; Olsen, P.E.; Kent, D.V.; Lepre, C.; Kinney, S.T.; Geissman, J.W.; Parker, W.G. (Bulletin of the Geological Society of America, 2021)
The Upper Triassic Chinle Formation is a critical non-marine archive of lowpaleolatitude biotic and environmental change in southwestern North America. The well-studied and highly fossiliferous Chinle strata at Petrified Forest National Park (PFNP), Arizona, preserve a biotic turnover event recorded by vertebrate and palynomorph fossils, which has been alternatively hypothesized to coincide with tectonically driven climate change or with the Manicouagan impact event at ca. 215.5 Ma. Previous outcrop-based geochronologic age constraints are difficult to put in an accurate stratigraphic framework because lateral facies changes and discontinuous outcrops allow for multiple interpretations. A major goal of the Colorado Plateau Coring Project (CPCP) was to retrieve a continuous record in unambiguous superposition designed to remedy this situation. We sampled the 520-m-long core 1A of the CPCP to develop an accurate age model in unquestionable superposition by combining U-Pb zircon ages and magnetostratigraphy. From 13 horizons of volcanic detritus-rich siltstone and sandstone, we screened up to 300 zircon crystals per sample using laser ablation –inductively coupled plasma –mass spectrometry and subsequently analyzed up to 19 crystals of the youngest age population using the chemical abrasion –isotope dilution –thermal ionization mass (CA-IDTIMS) spectrometry method. These data provide new maximum depositional ages for the top of the Moenkopi Formation (ca. 241 Ma), the lower Blue Mesa Member (ca. 222 Ma), and the lower (ca. 218 to 217 Ma) and upper (ca. 213.5 Ma) Sonsela Member. The maximum depositional ages obtained for the upper Chinle Formation fall well within previously proposed age constraints, whereas the maximum depositional ages for the lower Chinle Formation are relatively younger than previously proposed ages from outcrop; however, core to outcrop stratigraphic correlations remain uncertain. By correlating our new ages with the magnetostratigraphy of the core, two feasible age model solutions can be proposed. Model 1 assumes that the youngest, coherent U-Pb age clusters of each sample are representative of the maximum depositional ages and are close to (<1 Ma difference) the true time of deposition throughout the Sonsela Member. This model suggests a significant decrease in average sediment accumulation rate in the mid-Sonsela Member. Hence, the biotic turnover preserved in the mid-Sonsela Member at PFNP is also middle Norian in age, but may, at least partially, be an artifact of a condensed section. Model 2 following the magnetostratigraphic-based age model for the CPCP core 1A suggests instead that the ages from the lower and middle Sonsela Member are inherited populations of zircon crystals that are 1 –3 Ma older than the true depositional age of the strata. This results in a model in which no sudden decrease in sediment accumulation rate is necessary and implies that the base of the Sonsela Member is no older than ca. 216 Ma. Independent of these alternatives, both age models agree that none of the preserved Chinle Formation in PFNP is Carnian (>227 Ma) in age, and hence the biotic turnover event cannot be correlated to the Carnian –Norian boundary but is rather a mid-Norian event. Our age models demonstrate the powers, but also the challenges, of integrating detrital CA-ID-TIMS ages with magnetostratigraphic data to properly interpret complex sedimentary sequences. © 2020 Geological Society of America
cited By 25
Keywords: Binary alloys; Chemical analysis; Climate change; Crystals; Deposition; Forestry; Geochronology; Inductively coupled plasma; Laser ablation; Mass spectrometers; Mass spectrometry; Silicate minerals; Stratigraphy; Zircon; Environmental change; Multiple interpretations; Paleoenvironmental change; Sediment accumulation; Sedimentary sequence; Stratigraphic correlation; Stratigraphic framework; U-pb zircon geochronologies; Lead alloys; accumulation rate; depositional environment; environmental change; geochronology; inductively coupled plasma method; magnetostratigraphy; paleoecology; paleoenvironment; stratigraphic correlation; Triassic; uranium-lead dating; zircon; Arizona; Petrified Forest National Park; United States; Vertebrata

Upper Cretaceous paleoenvironmental changes and petrophysical responses in lacustrine record (Songliao Basin, NE China) and marine sedimentary deposit (Goban Spur Basin, NW Europe) - Kouamelan, K.S.; Zou, C.; Assie, K.R.; Peng, C.; N'Dri, K.A.; Mondah, O.R. (Journal of Geophysics and Engineering, 2021)
The Cretaceous interval is marked by several important geological changes whose prints are buried in both continental and marine sytems. Although significant paleoenvironmental details of this period have been inferred from biological and geochemical indicators, little is known about the physical proxies. Through scientific borehole data, petrophysical properties of Upper Cretaceous Songliao Basin (SB) in NE China and Goban Spur Basin (GSB) in NW Europe were intercorrelated to investigate the critical geological paleoenvironmental shifts and their petrophysical responses, through statistical, wavelet and spectral approaches. The results demonstrated that petrophysical features, particularly gamma-ray and resistivity reactivities, were responsive to past environmental changes in both terrestrial and marine systems. Shifts in organic-rich shale deposition and brine bearing shale showed a correlation to a probable period of seawater incursion in SB, while the gamma log, resistivity and density reactivities were interrelated to the basin paleo-structuration. At GSB, the gamma-ray and resistivity reactivities are tied-up to the Mid-Atlantic seabed motion, marine-water level shifts and paleoceanographic instabilities. In both paleo-basins, a decrease in the gamma-ray reactivity occurred from Turonian to Maastrichtian and is consistent with a regional or global increase in hydrodynamic energy. The oceanic/lacustrine anoxic events related to low sedimentation rate occurred in both basins and are associated with high gamma-ray and resistivity signals (SB); high gamma-ray and low resistivity signals (GSB). These changes correlated with geochemical evidence, suggesting that gamma-ray and resistivity can represent alternative means for marine and continental paleoenvironmental comparison. © 2021 Oxford University Press. All rights reserved.
cited By 0
Keywords: Cretaceous; environmental change; facies analysis; lacustrine deposit; marine environment; marine sediment; paleoenvironment; physicochemical property; sedimentation rate; Atlantic Ocean; China; Goban Spur; Songliao Basin

The effect of a gouge layer on rupture propagation along brittle shear fractures in deep and high-stress mines - Mngadi, S.B.; Tsutsumi, A.; Onoe, Y.; Manzi, M.S.D.; Durrheim, R.J.; Yabe, Y.; Ogasawara, H.; Kaneki, S.; Wechsler, N.; Ward, A.K.; Naoi, M.; Moriya, H.; et al. (International Journal of Rock Mechanics and Mining Sciences, 2021)
The presence of fault gouge and the generation of wear material between two sliding rock surfaces plays a critical role in slip weakening and propagation of ruptures along underground brittle shear fractures forming ahead of tabular excavations in deep and high stress gold mining. We performed two types of friction experiments: one with a fault gouge layer between two sliding surfaces, and the other without a fault gouge layer rock-on-rock’, both under room dry conditions at slip velocities ranging from 1.0 mm/s to 1200 mm/s. These friction experiments revealed a remarkable difference in the frictional weakening behaviour, e.g., rock-on-rock friction experiments show weakening behaviour at lower slip velocity ( 5 mm/s) and generally has lower frictional strength than those with the intervening fault gouge between sliding surfaces. This study shows that the existence of the fault gouge layer between sliding rock surfaces delays the onset of fault weakening (i.e., slip weakening displacement of gouge layer experiments is larger compared to rock-on-rock experiments). It is proposed that flash heating may be the main active weakening mechanism within both our gouge and rock-on-rock experiments, and provides a feasible account for the observed weakening. The observed slip weakening displacement (Dc) differences may be attributed to the presence of a gouge layer between sliding surfaces, which has many more contacts during sliding compared to rock-on-rock experiments, thus reducing the average slip velocity per contact, consequently, the potential for activation of flash heating which delays the onset of weakening. Here we suggest that we may be able to describe brittle shear fracture rupture propagation process along underground brittle shear zones by conducting low, intermediate and high slip velocity friction experiments with and without an intervening fault gouge between sliding rock surfaces. These findings should have important implications for the modelling of rupture propagation processes in underground shear zones, a phenomenon that influences the severity of rockbursts, and hence the safety of mine workers and mining operations.
Keywords: Shear zones; Brittle shear fracture; Rupture propagation; Severity of rockbursts; Slip velocity friction experiments; Fault weakening behaviour

Using multiple chronometers to establish a long, directly-dated lacustrine record: Constraining >600,000 years of environmental change at Chew Bahir, Ethiopia - Roberts, Helen M.; Ramsey, Christopher Bronk; Chapot, Melissa S.; Deino, Alan L.; Lane, Christine S.; Vidal, C'eline; Asrat, Asfawossen; Cohen, Andrew; Foerster, Verena; Lamb, Henry F.; Sch{abitz, Frank; Trauth, Martin H.; et al. (Quaternary Science Reviews, 2021)

Vegetation change in the Baringo Basin, East Africa across the onset of Northern Hemisphere glaciation 3.3 –2.6 Ma - Lupien, Rachel L.; Russell, James M.; Yost, Chad L.; Kingston, John D.; Deino, Alan L.; Logan, Jon; Schuh, Anna; Cohen, Andrew S. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2021)

Wet magmatic processes during the accretion of the deep crust of the Oman Ophiolite paleoridge: Phase diagrams and petrological records - Koepke, J; Feig, ST; Berndt, J; Neave, DA; Team, Oman Drilling Project Science; et al. (Tectonophysics, 2021)

Wildfire activity enhanced during phases of maximum orbital eccentricity and precessional forcing in the Early Jurassic - Hollaar, Teuntje P.; Baker, Sarah J.; Hesselbo, Stephen P.; Deconinck, Jean-François; Mander, Luke; Ruhl, Micha; Belcher, Claire M. (Communications Earth and Environment, 2021)

δ13C records from fish fossils as paleo-indicators of ecosystem responses 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, 2021)
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
Keywords: Baringo; East African Lakes; East African Rift; Kenya; Lake Malawi; Lake Turkana; Malawi; Tugen Hills; Turkana; carbon isotope; community structure; diatomite; environmental indicator; fossil record; organic matter; paleoenvironment; paleohydrology; sediment-water interface; trophic structure; water level

Magnetostratigraphy of the Triassic Moenkopi Formation From the Continuous Cores Recovered in Colorado Plateau Coring Project Phase 1 (CPCP-1), Petrified Forest National Park, Arizona, USA: Correlation of the Early to Middle Triassic Strata and Biota in Colorado Plateau and Its Environs - Haque, Z.; Geissman, J.W.; Irmis, R.B.; Olsen, P.E.; Lepre, C.; Buhedma, H.; Mundil, R.; Parker, W.G.; Rasmussen, C.; Gehrels, G.E. (Journal of Geophysical Research: Solid Earth, 2021)
The Colorado Plateau Coring Project Phase 1 (CPCP-1) acquired three continuous drill cores from Petrified Forest National Park (PFNP), Arizona, U.S.A., two of which (CPCP-PFNP13-1A and CPCP-PFNP13-2B) intersected the Upper Triassic Chinle Formation, Lower(?)-Middle Triassic Moenkopi Formation (MF) and Permian Coconino Sandstone. We examined both cores to construct a high-resolution magnetostratigraphy of MF strata, and progressive demagnetization data yield well-defined, interpretable paleomagnetic results. Each lithostratigraphic member of the MF (Wupatki, Moqui, and Holbrook members) contains authigenic and detrital hematite as the dominant magnetic carrier with distinguishing rock magnetic characteristics. Magnetostratigraphy of MF strata in both CPCP-1 cores consists of six normal and six reverse polarity magnetozones, from the youngest to the oldest, MF1n to MF6r. Recent single-crystal chemical abrasion –thermal ionization mass spectrometry (CA-TIMS) U-Pb data from a sample in magnetozone MF1n yield a latest Anisian/earliest Ladinian (241.38 ± 0.43 Ma) age. Correlation of the CA-TIMS-calibrated magnetostratigraphy with the astronomically tuned polarity timescale for the Middle Triassic deep-marine Guandao (GD) section of South China ties the magnetozone MF1n with GD8 and MF6r with GD2r, and implies that the MF spans, at most, the earliest Anisian (Aegean) to latest Anisian (Illyrian)/earliest Ladinian stages (ca. 246.8 to 241.5 Ma). This age estimate for the MF suggests that the timespan of the regional, pre-Norian disconformity is about 17 Ma, which demonstrates that MF vertebrate fossil assemblages in east-central Arizona are millions of years (minimally 3 –4 Ma) younger than previously suggested and are all Anisian in age, with no indications of substantial hiatuses in the MF section. © 2021. American Geophysical Union. All Rights Reserved.
cited By 5
Keywords: Anisian; biostratigraphy; demagnetization; fossil assemblage; lithostratigraphy; magnetostratigraphy; vertebrate; Arizona; China; Colorado Plateau; Petrified Forest National Park; United States; Vertebrata

The Environment at Lake El’gygytgyn Area (Northeastern Russian Arctic) Prior to and After the Meteorite Impact at 3.58 Ma - Andreev, A.; Dietze, E.; Glushkova, O.; Smirnov, V.; Wennrich, V.; Melles, M. (Frontiers in Earth Science, 2021)
Upper Pliocene sediments from a number of fluvial outcrops in central Chukotka, northeastern Russian Arctic, along the Enmyvaam, Mechekrynnetveem, and Chanuvenvaam Rivers, have been newly studied for pollen, non-pollen-palynomorphs and, for the first time for Pliocene sediments in Eurasia, charcoals. The sediments have survived the El’gygytgyn meteorite impact event at ∼3.58 Ma. The stratigraphy of the studied outcrops suggests that the lowermost sediments were accumulated shortly before the impact event, between ∼3.60 and 3.58 Ma. At that time, coniferous forests with spruces, pines, firs, birches, larches, and alders dominated in the area. Some relatively thermophilic broad-leaved taxa (Corylus, Carpinus, Ulmus, and Myrica) might also have grown in local forests. Summer temperatures were at least 10°C warmer than today. Charcoal concentrations and composition suggest the presence of high intensity fires. Periods of rather wet climate and soil conditions are marked by common shrubby and boggy habitats with ericaceous plants and Sphagnum, and are associated with less, and probably low-intensity surface fires with less charcoal. The impact event caused widespread fires reflected by up to 4 times higher charcoal concentrations in the sediments. The sediments found above the so-called “chaotic horizon” (sediments accumulated synchronously or very shortly after the impact event) contain late Pliocene pollen assemblages comparable to those in Lake El’gygytgyn, reflecting that pine-spruce forests with some firs, birches, larches, and alder dominated in the study area. Some thermophilic taxa might also still have grown in the area. However, the age control for the sediments above the so-called chaotic horizon is poor. The uppermost sediments from the studied sections can be attributed with certainty to the Late Pleistocene and Holocene according to their stratigraphic positions and pollen assemblages. The combined pollen and charcoal analysis allowed correlating hardly datable fluvial sediments and points to varying fire regimes in warmer-than-present climates, when forest extended further north compared to today. © Copyright © 2021 Andreev, Dietze, Glushkova, Smirnov, Wennrich and Melles.
cited By 0
Keywords: Charcoal; Fires; Forestry; Lakes; Meteorites; Plants (botany); Sediments; Stratigraphy; Charcoal analysis; Coniferous forests; Fluvial sediment; Meteorite impact; Pine-spruce forest; Pliocene sediments; Pollen assemblage; Summer temperature; Meteor impacts; charcoal; fluvial deposit; impact structure; meteorite; outcrop; palynology; Pliocene; sedimentary rock; Chukchi; Russian Federation

Terrestrial climate in mid-latitude East Asia from the latest Cretaceous to the earliest Paleogene: A multiproxy record from the Songliao Basin in northeastern China - Gao, Y.; Ibarra, D.E.; Caves Rugenstein, J.K.; Chen, J.; Kukla, T.; Methner, K.; Huang, H.; Lin, Z.; Zhang, L.; Xi, D.; Wu, H.; Carroll, A.R.; et al. (Earth-Science Reviews, 2021)
From the latest Cretaceous (late Campanian to Maastrichtian, 75 –66 Ma) to the earliest Paleogene, fluctuations in greenhouse climate, inferred primarily from marine sediments, have been linked to volcanism, the Chicxulub asteroid impact, and the Cretaceous-Paleogene (K-Pg) mass extinction. In this paper, we summarize terrestrial climate records in mid-latitude East Asia during the latest Cretaceous and across the K-Pg boundary, based on a multi-proxy approach from the geochronologically well-constrained Sifangtai and Mingshui formations (SMF), accessed by scientific drilling of the Songliao Basin in northeastern China. Evolution of sedimentary environments is characterized by five depositional units of fluvial-deltaic-lacustrine facies. Development of four types of paleosols, including Inceptisols, Aridisols, Vertisols and Alfisols, is interpreted to primarily reflect climatic changes. Correlations among sedimentary facies, paleosol features, illite chemistry index, chemical index of alteration, as well as stable and clumped isotopes of pedogenic carbonates and clay minerals of the SMF validate their reliability for paleoclimate reconstruction, and indicate significant fluctuations in terrestrial climate and sedimentary environment. During global warming intervals possibly triggered by volcanism (e.g. 69.5 –68.5 Ma), the Songliao Basin experienced a warmer and wetter climate with stronger terrestrial chemical weathering and more monsoon-derived moisture sourced from the Pacific. In contrast, during global cooling intervals (e.g. 70.5 –69.5 Ma and 68.5 –66.5 Ma), the SMF record a cooler and drier climate with less intensive chemical weathering and more westerlies-derived moisture. Across the K-Pg boundary, dramatic changes in land temperatures and hydroclimate correspond to the latest Maastrichtian warming episode ( 66.4 –66.1 Ma), the transient cooling preceding the K-Pg boundary ( 66.1 –66.0 Ma), and the earliest Paleogene warming interval ( 66.0 –65.7 Ma). Temporal correlation of weathering index changes with the Deccan Traps volcanism suggests that volcanism and subsequent intensified weathering played a major role for climatic changes across the K-Pg boundary. The integrated records of sedimentological and geochemical datasets from the Songliao Basin robustly demonstrate that the terrestrial climate of mid-latitude East Asia responded strongly to greenhouse climate changes and to the catastrophic geological events from the latest Cretaceous to the earliest Paleogene. © 2021 Elsevier B.V.
cited By 16
Keywords: Cretaceous; depositional environment; fluvial deposit; lacustrine deposit; midlatitude environment; Paleogene; proxy climate record; terrestrial environment; China; Songliao Basin; Asteroidea

Revisiting the Koyna-Warna seismic zone: strain budget, present-day potential and associated hazard - Sutar, Anup K.; Roy, Sukanta; Tiwari, V.M. (Journal of Seismology, 2021)

Shaping of the Present-Day Deep Biosphere at Chicxulub by the Impact Catastrophe That Ended the Cretaceous - Cockell, C.S.; Schaefer, B.; Wuchter, C.; Coolen, M.J.L.; Grice, K.; Schnieders, L.; Morgan, J.V.; Gulick, S.P.S.; Wittmann, A.; Lofi, J.; Christeson, G.L.; Kring, D.A.; et al. (Frontiers in Microbiology, 2021)
We report on the effect of the end-Cretaceous impact event on the present-day deep microbial biosphere at the impact site. IODP-ICDP Expedition 364 drilled into the peak ring of the Chicxulub crater, M'exico, allowing us to investigate the microbial communities within this structure. Increased cell biomass was found in the impact suevite, which was deposited within the first few hours of the Cenozoic, demonstrating that the impact produced a new lithological horizon that caused a long-term improvement in deep subsurface colonization potential. In the biologically impoverished granitic rocks, we observed increased cell abundances at impact-induced geological interfaces, that can be attributed to the nutritionally diverse substrates and/or elevated fluid flow. 16S rRNA gene amplicon sequencing revealed taxonomically distinct microbial communities in each crater lithology. These observations show that the impact caused geological deformation that continues to shape the deep subsurface biosphere at Chicxulub in the present day. © Copyright © 2021 Cockell, Schaefer, Wuchter, Coolen, Grice, Schnieders, Morgan, Gulick, Wittmann, Lofi, Christeson, Kring, Whalen, Bralower, Osinski, Claeys, Kaskes, de Graaff, D'ehais, Goderis, Hernandez Becerra, Nixon and IODP-ICDP Expedition 364 Scientists.
cited By 4

Rock surface fungi in deep continental biosphere–exploration of microbial community formation with subsurface in situ biofilm trap - Nuppunen-Puputti, Maija; Kiet{av{ainen, Riikka; Purkamo, Lotta; Rajala, Pauliina; It{avaara, Merja; Kukkonen, Ilmo; Bomberg, Malin (Microorganisms, 2021)
Fungi have an important role in nutrient cycling in most ecosystems on Earth, yet their ecology and functionality in deep continental subsurface remain unknown. Here, we report the first observations of active fungal colonization of mica schist in the deep continental biosphere and the ability of deep subsurface fungi to attach to rock surfaces under in situ conditions in groundwater at 500 and 967 m depth in Precambrian bedrock. We present an in situ subsurface biofilm trap, designed to reveal sessile microbial communities on rock surface in deep continental groundwater, using Outokumpu Deep Drill Hole, in eastern Finland, as a test site. The observed fungal phyla in Outokumpu subsurface were Basidiomycota, Ascomycota, and Mortierellomycota. In addition, significant proportion of the community represented unclassified Fungi. Sessile fungal communities on mica schist surfaces differed from the planktic fungal communities. The main bacterial phyla were Firmicutes, Proteobacteria, and Actinobacteriota. Biofilm formation on rock surfaces is a slow process and our results indicate that fungal and bacterial communities dominate the early surface attachment process, when pristine mineral surfaces are exposed to deep subsurface ecosystems. Various fungi showed statistically significant cross-kingdom correlation with both thiosulfate and sulfate reducing bacteria, e.g., SRB2 with fungi Debaryomyces hansenii. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.

Sedimentary stratigraphy of Lake Chalco (Central Mexico) during its formative stages - Mart'inez-Abarca, R.; Ortega-Guerrero, B.; Lozano-Garc'ia, S.; Caballero, M.; Valero-Garc'es, B.; McGee, D.; Brown, E.T.; Stockhecke, M.; Hodgetts, A.G.E. (International Journal of Earth Sciences, 2021)
Lake Chalco lies south of the Basin of Mexico and has been the subject of studies related to Late Quaternary climate variability. In 2016, the International Continental Scientific Drilling Program “MexiDrill Project” recovered a 520-m sediment record from Lake Chalco. Magnetic susceptibility measurements revealed substantial changes in sediment physical properties between 343 and 285 m depth, suggesting changes in composition associated with fluctuations in the depositional environment. We targeted sediments in the 343 –285 m interval for high-resolution facies analysis, to develop a model of Lake Chalco formation. We identified three facies associations, using sediment composition, texture, mineralogy and micro-morphological characteristics: (1) detrital facies, consisting of laminated silt, massive sand, stratified silty sand, clast-supported gravel and matrix-supported gravel; (2) biogenic facies, which include diatom ooze and bivalve coquina; and (3) volcaniclastic facies, represented by clast-supported pumice deposits. We propose that formation of Lake Chalco occurred in four stages, which we identified by changes in sediment characteristics. The first stage was an alluvial delta environment, in which debris and hyper-concentrated flows were the main sediment transport agents. The second was characterized by turbulent flows in a fluvial deltaic environment, which alternated with laminar flows associated with floodplains. The third stage was a time of fluvio-lacustrine transition in the basin, with formation of the previously identified Paleo-Chalco-I Lake, in response to wet conditions. During the fourth stage, a deep eutrophic lake formed (Paleo-Chalco-II), with an origin that appears to have been related to regional volcanism. Our working age-depth model indicates establishment of the lake at ca. 400 ± 46 ka. This paper presents the only available record of the transition from alluvial to lacustrine sedimentation of Lake Chalco. Our results allow us to establish (1) how the lake was formed and what the phases of its development were, (2) how a major volcanic event altered and transformed the lacustrine sedimentation, and (3) which climatic conditions dominated during the lake formation. The age for the onset of the lacustrine sedimentation in Chalco is for the first time constrained to around 400 ka. This enables to expand our knowledge of the climate for a time for which there is no information from terrestrial records of tropical North America. © 2021, Geologische Vereinigung e.V. (GV).
cited By 5
Keywords: climate conditions; climate variation; depositional environment; facies analysis; fluvial deposit; lacustrine deposit; Quaternary; sedimentation; stratigraphy; volcanism; Lake Chalco; Mexico [North America]; Valley of Mexico; Bacillariophyta; Bivalvia

Seismic activity associated with the 1963–1967 Surtsey eruption off the coast of South Iceland - Sayyadi, Sara; Einarsson, P'all; Gudmundsson, Magnus T (Bulletin of Volcanology, 2021)

Seismic anisotropy of mid crustal orogenic nappes and their bounding structures: An example from the Middle Allochthon (Seve Nappe) of the Central Scandinavian Caledonides - Almqvist, Bjarne S. G.; Cyprych, Daria; Piazolo, Sandra (Tectonophysics, 2021)
We report compositional, microstructural and seismic properties from 24 samples collected from the Middle Allochthon (Seve Nappe) of the central Scandinavian Caledonides, and its bounding shear zones. The samples stem both from field outcrops and the continental drilling project COSC-1 and include quartzofeldspathic gneisses, hornblende gneisses, amphibolites, marbles, calc-silicates, quartzites and mica schists, of medium to high-strain. Seismic velocities and anisotropy of P (AVp) and S (AVs) waves of these samples were calculated using microstructural and crystal preferred orientation data obtained from Electron Backscatter Diffraction analysis (EBSD). Mica-schist exhibits the highest anisotropy (AVP ~ 31%; max AVs ~34%), followed by hornblende-dominated rocks (AVp ~5 –13%; max AVs 5 –10%) and quartzites (AVp ~6.5 –10.5%; max AVs ~7.5 –12%). Lowest anisotropy is found in calc-silicate rocks (AVp ~4%; max AVs 3 –4%), where the symmetry of anisotropy is more complex due to the contribution to anisotropy from several phases. Anisotropy is attributed to: 1) modal mineral composition, in particular mica and amphibole content, 2) CPO intensity, 3) crystallization of anisotropic minerals from fluids circulating in the shear zone (calc-silicates and amphibolites), and to a lesser extent 4) compositional banding of minerals with contrasting elastic properties and density. Our results link observed anisotropy to the rock composition and strain in a representative section across the Central Scandinavian Caledonides and indicate that the entire Seve Nappe is seismically anisotropic. Strain has partitioned on the nappe scale, and likely on the microstructural scale. High- strain shear zones that develop at boundaries of the allochthon and internally within the allochthon show higher anisotropy than a more moderately strained interior of the nappe. The Seve Nappe may be considered as a template for deforming, ductile and flowing middle crust, which is in line with general observations of seismic anisotropy in mid-crustal settings.
Keywords: Strain; Seismic anisotropy; Shear zone; Scandinavian Caledonides; Orogeny

Seismic faults triggered early stage serpentinization of peridotites from the Samail Ophiolite, Oman - Aupart, Claire; Morales, Luiz; Godard, Marguerite; Jamtveit, Bjørn (Earth and Planetary Science Letters, 2021)

Seismic stratigraphic evidence of a pre-impact basin in the Yucat'an Platform: morphology of the Chicxulub crater and K/Pg boundary deposits - Guzm'an-Hidalgo, E.; Grajales-Nishimura, J.M.; Eberli, G.P.; Aguayo-Camargo, J.E.; Urrutia-Fucugauchi, J.; P'erez-Cruz, L. (Marine Geology, 2021)
Fifty-four 2D seismic profiles and 13 boreholes were used to describe pre-impact and post-impact deposits in the Yucat'an Shelf. Previous work has identified a pre-impact basin in the northwest portion of the Chicxulub structure. The geometry of seismic reflectors associated with the Mesozoic Era shows that this pre-impact depression, here named Yucat'an Trough, extends from the southern part of the Yucat'an Peninsula to the northern face of the Campeche Escarpment. Stratigraphic data from boreholes of the Yucat'an Platform suggest that the main sedimentary fills of the Yucat'an Trough are a thin series of Upper Jurassic-Lower Cretaceous red beds, followed by the evaporite-dominated Lower Cretaceous and the carbonate-dominated Upper Cretaceous sedimentary successions. Mapping of the Cretaceous-Paleogene (K/Pg) deposits allowed us to observe the morphology of the Yucat'an Shelf by the time of the Chicxulub impact event. The two-way seismic time K/Pg deposits map in conjunction with the free-air gravity anomaly map of the northern Yucat'an Block reveals that, before the impact, the carbonate platform was divided into two blocks by a 95 –205 km wide and 470-km long trough-shaped depression, probably a rift-basin with a north-south orientation, in which the central structure of Chicxulub impact crater is contained. The seismic reflectors overlying the top of the K/Pg deposits show that, during the Cenozoic Era, both the Yucat'an Trough and impact basin were filled by progradational sequences which flattened the surface completely until the current block of the Yucat'an Platform was configured. © 2021 Elsevier B.V.
cited By 0

Shock impedance amplified impact deformation of zircon in granitic rocks from the Chicxulub impact crater - Wittmann, A.; Cavosie, A.J.; Timms, N.E.; Ferrière, L.; Rae, A.; Rasmussen, C.; Ross, C.; Stockli, D.; Schmieder, M.; Kring, D.A.; Zhao, J.; Xiao, L.; et al. (Earth and Planetary Science Letters, 2021)
Zircon is a precise chronometer and prominent recorder of impact deformation. However, many impact-induced features in zircon are poorly calibrated, sometimes due to contradicting experimental data, in other instances due to the lack of systematic studies of impact-deformed zircon. To resolve issues with the shock petrographic use of zircon, we classified impact deformation features in 429 zircon grains in a continuous drill core of uplifted, granitic bedrock in the peak ring of the 200-km-diameter K-Pg Chicxulub impact structure. Following initial identification in backscattered electron (BSE) images, Raman spectroscopy and electron backscatter diffraction confirmed one reidite-bearing zircon grain. Quartz-based shock barometry indicates the host rock of this zircon-reidite grain experienced an average shock pressure of 17.5 GPa. A survey of BSE images of 429 ZrSiO4 grains found brittle deformation features are ubiquitous, with planar fractures in one to five sets occurring in 23% of all zircon grains. Our survey also reveals a statistically significant correlation of the occurrence of planar fractures in zircon with the types of host materials. Compared to zircon enclosed in mafic, higher density mineral hosts, felsic, low-density minerals show a much higher incidence of zircon with planar fractures. This finding suggests amplification of pressure due to shock impedance contrasts between zircon and its mineral hosts. Using the impedance matching method, we modeled the shock impedance pressure amplification effect for zircon inclusions in Chicxulub granitic hosts. Our modeling indicates shock impedance could have amplified the average 17.5 GPa shock pressure in a zircon inclusion in quartz or feldspar in the Chicxulub granitic rocks to 24 ± 1 GPa, suggesting that reidite in these rocks formed between 17.5 and 25 GPa. In essence, our study of impedance-induced shock pressure amplification in zircon assemblages, including the onset of reidite formation, details how shock impedance in mineral associations can be quantified to refine shock pressure estimates. © 2021 The Author(s)
cited By 5

Terrestrial and extraterrestrial chemical components of early Archean impact spherule layers from Fairview Gold Mine, northern Barberton greenstone belt, South Africa - Oliveira, Grace Juliana Gonçalves; Reimold, Wolf Uwe; Cr'osta, Alvaro Penteado; Hauser, Natalia; Koeberl, Christian; Mader, Dieter; Schmitt, Ralf-Thomas; Mohr-Westheide, Tanja (Special Paper of the Geological Society of America, 2021)
Early Archean spherule layers, widely accepted to represent distal ejecta deposits from large-scale impact events onto the early Earth, have been described from several stratigraphic levels of the Barberton greenstone belt in South Africa. Recently, exploration drilling at the Fairview Gold Mine (25°43'53'S, 31°5'59'E) in the northern domain of the belt resulted in the discovery of a new set of spherule layer intersections. The Fairview spherule layers in drill cores BH5901, BH5907, BH5911, and BH5949 were intersected just a few meters apart, at about the same stratigraphic position within the transition from the Onverwacht Group to the Fig Tree Group. The Fairview spherule layers have petrographic and chemical similarities to at least three other well-known Barberton spherule layers (S2-S4), and multiple spherule layer bed intersections in drill cores BARB5 and CT3, all from about the same stratigraphic position. They are not uniform in composition, in particular with respect to abundances of highly siderophile elements. The highest concentrations of moderately (Cr, Co, Ni) and highly siderophile (Ir) elements are within the range of concentrations for chondrites and, thus, reinforce the impact hypothesis for the generation of the Fairview spherule layers. Iridium peak concentrations and Cr/Ir interelement ratios for spherule layer samples from drill cores BH5907, BH5911, and BH5949 suggest admixtures of 50%-60% chondritic material, whereas for the BH5901 spherule layer, only an admixture of 1% chondritic material is indicated. We discuss whether these four Fairview spherule layers represent the same impact event, and whether they can be correlated to any of the S2-S4, CT3, and BARB5 intersections. © 2021 The Geological Society of America.
Keywords: Barberton Greenstone Belt; Core drilling; Economic geology; Gold deposits; Gold mines; Infill drilling; Stratigraphy; Admixture; Archaean; Barberton; Chemical component; Drill core; Greenstone belts; Impact events; Impact spherules; Large-scale impacts; South Africa; Archean; chemical composition; chondrite; concentration (composition); drilling; iridium; mine; petrography; spherule; Drills

Shock-deformed zircon from the Chicxulub impact crater and implications for cratering process - Zhao, J.; Xiao, L.; Xiao, Z.; Morgan, J.V.; Osinski, G.R.; Neal, C.R.; Gulick, S.P.S.; Riller, U.; Claeys, P.; Zhao, S.; Prieur, N.C.; Nemchin, A.; et al. (Geology, 2021)
Large impact structures with peak rings are common landforms across the solar system, and their formation has implications for both the interior structure and thermal evolution of planetary bodies. Numerical modeling and structural studies have been used to simulate and ground truth peak-ring formative mechanisms, but the shock metamorphic record of minerals within these structures remains to be ascertained. We investigated impact-related microstructures and high-pressure phases in zircon from melt-bearing breccias, impact melt rock, and granitoid basement from the Chicxulub peak ring (Yucat'an Peninsula, Mexico), sampled by the International Ocean Discovery Program (IODP)/International Continental Drilling Project (IODP-ICDP) Expedition 364 Hole M0077A. Zircon grains exhibit shock features such as reidite, zircon twins, and granular zircon including “former reidite in granular neoblastic” (FRIGN) zircon. These features record an initial high-pressure shock wave (>30 GPa), subsequent relaxation during the passage of the rarefaction wave, and a final heating and annealing stage. Our observed grain-scale deformation history agrees well with the stress fields predicted by the dynamic collapse model, as the central uplift collapsed downward-then-outward to form the peak ring. The occurrence of reidite in a large impact basin on Earth represents the first such discovery, preserved due to its separation from impact melt and rapid cooling by the resurging ocean. The coexistence of reidite and FRIGN zircon within the impact melt –bearing breccias indicates that cooling by seawater was heterogeneous. Our results provide valuablen information on when different shock microstructures form and how they are modified according to their position in the impact structure, and this study further improves on the use of shock barometry as a diagnostic tool in understanding the cratering process. © 2021 Geological Society of America. For permission to copy, contact editing@geosociety.org.
cited By 5

Spatial Dependence of Dynamic Nonlinear Rock Weakening at the Alpine Fault, New Zealand - Simpson, Jonathan; Wijk, Kasper; Adam, Ludmila (Geophysical Research Letters, 2021)

Spatial-temporal characterization of the san andreas fault by fault-zone trapped waves at seismic experiment site, parkfield, california - Li, Y.-G. (Earthquake Science, 2021)
In this article, we review our previous research for spatial and temporal characterizations of the San Andreas Fault (SAF) at Parkfield, using the fault-zone trapped wave (FZTW) since the middle 1980s. Parkfield, California has been taken as a scientific seismic experimental site in the USA since the 1970s, and the SAF is the target fault to investigate earthquake physics and forecasting. More than ten types of field experiments (including seismic, geophysical, geochemical, geodetic and so on) have been carried out at this experimental site since then. In the fall of 2003, a pair of scientific wells were drilled at the San Andreas Fault Observatory at Depth (SAFOD) site; the main-hole (MH) passed a 200-m-wide low-velocity zone (LVZ) with highly fractured rocks of the SAF at a depth of 3.2 km below the wellhead on the ground level (Hickman et al., 2005; Zoback, 2007; Lockner et al., 2011). Borehole seismographs were installed in the SAFOD MH in 2004, which were located within the LVZ of the fault at 3-km depth to probe the internal structure and physical properties of the SAF. On September 28 2004, a M6 earthquake occurred 15 km southeast of the town of Parkfield. The data recorded in the field experiments before and after the 2004 M6 earthquake provided a unique opportunity to monitor the co-mainshock damage and post-seismic heal of the SAF associated with this strong earthquake. This retrospective review of the results from a sequence of our previous experiments at the Parkfield SAF, California, will be valuable for other researchers who are carrying out seismic experiments at the active faults to develop the community seismic wave velocity models, the fault models and the earthquake forecasting models in global seismogenic regions. © The Seismological Society of China and Institute of Geophysics, China Earthquake Administration 2021.
cited By 2

Structural and thermal evolution of an infant subduction shear zone: Insights from sub-ophiolite metamorphic rocks recovered from Oman Drilling Project Site BT-1B - Kotowski, Alissa J; Cloos, Mark; Stockli, Daniel F; Bos Orent, Eytan (Journal of Geophysical Research: Solid Earth, 2021)

Studies of Artificial Water Reservoir Triggered Earthquakes at Koyna, India: A Summary - Gupta, H.K. (Journal of the Geological Society of India, 2021)
Anthropogenic seismicity has been observed due to filling of artificial water reservoirs, geothermal and natural oil/gas production, and gold/coal mining under favorable geological conditions. Among these, artificial water reservoir triggered seismicity (RTS) is most prominent, with over 200 sites globally where RTS has been observed, including 5 sites where earthquakes exceeding M 6 magnitude occurred. Koyna, located near the west coast of India in stable Deccan Volcanic Province is the most prominent site where the largest RTS event of M 6.3 occurred in 1967, and the RTS has continued till now, for near field study of earthquakes. Here we present a summary of (a) global RTS, (b) scientific work carried in the Koyna region, (c) characterizing RTS, and (d) establishing a 3 km deep Pilot Borehole laboratory as a precursor to setting up of a ∼ 7 km deep bore hole laboratory. The work being carried out is providing necessary inputs for the design of the ∼ 7 km deep borehole laboratory for the near field studies of RTS and shed light on the geneses of earthquakes in general and RTS. © 2021, GEOL. SOC. INDIA.
cited By 0
Keywords: earthquake magnitude; earthquake trigger; geothermal energy; geothermal power; hydrocarbon reservoir; seismicity; India; Koyna; Maharashtra

Temperature, precipitation, and vegetation changes in the Eastern Mediterranean over the last deglaciation and Dansgaard-Oeschger events - Stockhecke, Mona; Bechtel, Achim; Peterse, Francien; Guillemot, Typhaine; Schubert, Carsten J. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2021)

Major Mineral Fraction and Physical Properties of Carbonated Peridotite (Listvenite) From ICDP Oman Drilling Project Hole BT1B Inferred From X-Ray CT Core Images - Okazaki, Keishi; Michibayashi, Katsuyoshi; Hatakeyama, Kohei; Abe, Natsue; Johnson, Kevin TM; Kelemen, Peter B; Team, Oman Drilling Project Science (Journal of Geophysical Research: Solid Earth, 2021)
We quantified mineral proportions in listvenite (completely carbonated peridotite) in Hole BT1B drilled across the basal thrust of the Samail ophiolite by the International Continental Scientific Drilling Project Oman Drilling Project using 3D X-ray Computed Tomography (XCT). We analyzed >250,000 XCT images from a continuous ∼200 m listvenite core. Histograms of the intensity of X-ray attenuation of each XCT core-slice image were fitted assuming that the listvenites are composed of magnesite, quartz, and dolomite. The XCT mineral peaks were confirmed by comparison with chemical mapping data obtained using an X-ray fluorescence (XRF) core scanner. Listvenite matrix is composed almost entirely of magnesite and quartz, consistent with discrete XRD and XRF data. Veins are composed mostly of dolomite. The mean abundance of dolomite in listvenite from BT1B is 11 vol.%, whereas that in core sections within 15 m of the basal thrust is >50 vol.%, suggesting the basal thrust acted as a source of Ca- and CO2-rich fluids. The SiO2:MgO:CaO molar ratio in the entire core from BT1B is 42:52:6, similar to that of onboard XRF data for discrete samples (41:54:5), whereas average Oman peridotites have ratios of (39:60:1), indicating Ca addition perhaps during carbonation. P- and S-wave velocities and density of listvenite are close to those of peridotite and are higher than those of serpentinites. These results suggest that limited material transfer during carbonation and hydration of the Samail ophiolite, except for Ca, CO2, and H2O. Listvenites formed in the mantle wedge above subduction zones may be an overlooked reservoir for carbon in the Earth's interior. © 2021. American Geophysical Union. All Rights Reserved.
cited By 4
Keywords: carbon storage; mantle structure; mineral; ophiolite; peridotite; physical property; tectonic plate; X-ray tomography

Low-temperature hydrogen formation during aqueous alteration of serpentinized peridotite in the Samail ophiolite - Ellison, Eric T; Templeton, Alexis S; Zeigler, Spencer D; Mayhew, Lisa E; Kelemen, Peter B; Matter, Juerg M; Party, Oman Drilling Project Science (Journal of Geophysical Research: Solid Earth, 2021)

Magnetostratigraphy of the Hominin Sites and Paleolakes Drilling Project (HSPDP) Baringo-Tugen Hills-Barsemoi core (Kenya) - Sier, Mark J.; Dupont-Nivet, Guillaume; Langereis, Cor; Deino, Alan L.; Kingston, John D.; Cohen, Andrew S. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2021)
The principal objective of the Hominin Sites and Paleolakes Drilling project (HSPDP) is to study the relationship between climate and environmental change and the implications on human evolution in eastern Africa. For this purpose, HSPDP has recovered a 228 m core in the Chemeron Formation of the Baringo Basin (Kenya). The Chemeron Formation spans approximately 3.7 Myr, from around 1.6 to 5.3 Ma, and has yielded many vertebrate fossils, including fossil hominins. The magnetostratigraphy of the Baringo core contributes to the chronological framework. A total of 567 individual paleomagnetic samples were collected from 543 levels at regular intervals throughout the core and 264 were processed using thermal and alternative field stepwise demagnetizations. In most samples, distinct Low-Temperature (LT; 20 –150 °C) and High-Temperature (HT; 150 –550 °C) Characteristic Remanent Magnetization (ChRM) could be determined. Typical demagnetization behaviors and some rock magnetic experiments suggest titanomagnetite acts as the main carrier of the HT ChRM with pervasive secondary overprints in normal polarity expressed by the LT component. Normal and reversed polarities were identified based on the secondary overprints LT ChRM directions, either parallel or antiparallel to the HT ChRM directions respectively. Our study identified four paleomagnetic reversals interpreted as the Matuyama-Gauss, Gauss-Kaena, Kaena-Gauss and the Gauss-Mammoth transitions. These boundaries provide chronostratigraphic tie-points that can be combined with those derived from 40Ar/39Ar dating of tuffs (Deino et al., 2020) and together indicate that the HSPDP Baringo core has an age range of 3.3 Ma to 2.6 Ma. The consistent paleomagnetic and radioisotopic age constraints are incorporated into a Bayesian age model of the core (Deino et al., 2020). © 2021 Elsevier B.V.
Keywords: Baringo; Kenya; Tugen Hills; Vertebrata; chronostratigraphy; demagnetization; environmental change; fossil record; hominid; human evolution; magnetostratigraphy; paleohydrology; paleomagnetism; titanomagnetite

Changes in the cyclicity and variability of the eastern African paleoclimate over the last 620 kyrs - Duesing, Walter; Kaboth-Bahr, Stefanie; Asrat, Asfawossen; Cohen, Andrew S.; Foerster, Verena; Lamb, Henry F.; Schaebitz, Frank; Trauth, Martin H.; Viehberg, Finn (Quaternary Science Reviews, 2021)

Cross-Scale Seismic Anisotropy Analysis in Metamorphic Rocks From the COSC-1 Borehole in the Scandinavian Caledonides - K{astner, Felix; Pierdominici, Simona; Zappone, Alba; Morales, Luiz F. G.; Wilke, Franziska D. H.; Berndt, Christian (Journal of Geophysical Research: Solid Earth, 2021)
Metamorphic and deformed rocks in thrust zones show particularly high seismic anisotropy causing challenges for seismic imaging and interpretation. A good example is the Seve Nappe Complex in central Sweden, an old exhumed orogenic thrust zone that is characterized by a strong but incoherent seismic reflectivity and considerable seismic anisotropy. However, only little is known about their origin in relation to composition and structural influences on measurements at different seismic scales. Here, we present a new integrative study of cross-scale seismic anisotropy analyses combining mineralogical composition, microstructural analyses, and seismic laboratory experiments from the COSC-1 borehole, which sampled a 2.5-km-deep section of metamorphic rocks deformed in an orogenic root now preserved in the Lower Seve Nappe. While there is strong crystallographic preferred orientation in most samples in general, variations in anisotropy depend mostly on bulk mineral composition and dominant core lithology as shown by a strong correlation between these. This relationship enables to identify three distinct seismic anisotropy facies providing a continuous anisotropy profile along the borehole. Moreover, comparison of laboratory seismic measurements and electron-backscatter diffraction data reveals a strong scale dependence, which is more pronounced in the highly deformed, heterogeneous samples. This highlights the need for comprehensive cross-validation of microscale anisotropy analyses with additional lithological data when integrating seismic anisotropy over seismic scales.
_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2020JB021154
Keywords: COSC; core measurements; electron-backscatter diffraction; seismic anisotropy

Crack geometry of serpentinized peridotites inferred from onboard ultrasonic data from the Oman Drilling Project - Katayama, Ikuo; Abe, Natsue; Okazaki, Keishi; Hatakeyama, Kohei; Akamatsu, Yuya; Michibayashi, Katsuyoshi; Godard, Marguerite; Kelemen, Peter; Phase, The Oman Drilling Project; Party, Science (Tectonophysics, 2021)
To assess the geometry of cracks in highly altered peridotites, we analyzed the ultrasonic velocity of serpentinized dunites and harzburgites collected by the Oman Drilling Project (Holes BA1B, 3A, and 4A). First, we estimated the hydrated fraction from grain density to obtain the porosity-free matrix velocity, which indicated complete serpentinization at shallow depths and decreasing hydration at greater depths. We assume that the difference between the solid matrix and measured onboard ultrasonic velocity is attributed to cracks with a spheroidal shape in the samples. Application of the effective medium theory to onboard data, such as P-wave velocity and porosity, indicates that the average pore aspect ratio is mostly between 0.1 and 0.01, and crack density varies from 0.58 to 0.02. We found a positive relationship between aspect ratio and hydrated fraction, suggesting a change in crack shape related to dissolution –precipitation processes during hydration. The relatively high aspect ratio and hence high fluid flux at shallow depths are also consistent with the onboard resistivity data and present-day hydration processes inferred from the borehole fluid chemistry. The inversion of ultrasonic data provides a series of elastic moduli that can be used to make a rough approximation of Poisson's ratio from the onboard data, which is a key physical property for interpreting geophysical observations in the oceanic lithosphere. © 2021 The Authors
cited By 1
Keywords: Boreholes; Hydration; Infill drilling; Matrix algebra; Porosity; Seismic waves; Ultrasonic velocity; Wave propagation; Effective medium theories; Geophysical observations; High aspect ratio; Hydration process; Oceanic lithosphere; Precipitation process; Rough approximations; Serpentinized peridotites; Aspect ratio; cracking (fracture); dunite; fracture geometry; harzburgite; hydration; Poisson ratio; serpentinization; ultrasonics; wave velocity; Oman

Coupled stable chromium and iron isotopic fractionation tracing magmatic mineral crystallization in Archean komatiite-tholeiite suites - Wagner, Luise J.; Kleinhanns, Ilka C.; Weber, Nadja; Babechuk, Michael G.; Hofmann, Axel; Schoenberg, Ronny (Chemical Geology, 2021)

COSC-2 operational report - Operational data sets - Lorenz, H.; Juhlin, C.; Rosberg, J.E.; Bazargan, M.; Klonowska, I.; Lescoutre, R.; Rejkjær, S.; Westmeijer, G.; Ziemniak, G. (GFZ German Research Centre for Geosciences, 2021)

Coring of the Paleocene-Eocene Thermal Maximum (PETM) in Denmark: ICDP Project PVOLC - Jones, Morgan; Stokke, Ella; Planke, Sverre; Augland, Lars; Svensen, Henrik; Tegner, Christian; Sluijs, Appy; Frieling, Joost; Mather, Tamsin; Huismans, Ritske (EGU General Assembly Conference Abstracts, 2021)

Core-Log-Seismic Integration in Metamorphic Rocks and Its Implication for the Regional Geology: A Case Study for the ICDP Drilling Project COSC-1, Sweden - Elger, Judith; Berndt, Christian; K{astner, Felix; Pierdominici, Simona; K{uck, Jochem; Almqvist, Bjarne S. G.; Juhlin, Christopher; Lorenz, Henning (Geochemistry, Geophysics, Geosystems, 2021)
Continental collision causes deformation in the crust along shear zones. However, the physical and chemical conditions at which these zones operate and the deformation processes that enable up to hundreds of km of tectonic transport are still unclear because of the depth at which they occur and the challenges in imaging them. Ancient exhumed collision zones allow us to investigate these processes much better, for example at the COSC-1 borehole in the central Scandinavian Caledonides. This study combines data from the COSC-1 borehole with different seismic measurements to provide constraints on the spatial lithological and textural configuration of the Seve Nappe Complex. This is one of the few studies that shows that core-log-seismic integration in metamorphic rocks allows to identify the spatial distribution of major lithological units. Especially gamma ray logs in combination with density data are powerful tools to distinguish between mafic and felsic lithologies in log-core correlation. Our results indicate that reflections along the borehole are primarily caused by compositional rather than textural changes. Reflections in the Seve Nappe Complex are not as distinct as in greater depths but continuous and several of them can be linked to magmatic intrusions, which have been metamorphically overprinted. Their setting indicates that the Seve Nappe Complex consists of the remnants of a volcanic continental margin. Our results suggest that ductile-deformed middle crustal reflectivity is primarily a function of pre-orogenic lithological variations which has to be considered when deciphering mountain building processes.
_eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2020GC009376
Keywords: central Scandinavian Caledonides; core-log-seismic integration; COSC-1

Controlling factors for organic carbon burial in the late cretaceous nenjiang formation of the songliao basin, ne China - Niu, L.; Gao, Y.; Huang, H.; Tian, X.; Dong, T.; Yang, Q.; Cao, X.; Wang, C. (Energies, 2021)
The Songliao Basin (SLB) is a large terrestrial petroliferous basin located in northeastern China. The Nenjiang Formation represents excellent hydrocarbon source rocks for the Daqing oil field. Previous studies have indicated that the oil shale intervals from the first (K2n1 ) and second (K2n2 ) members of the Nenjiang Formation were formed in different depositional settings. In this study, we provide a new high-resolution (1 m interval) record from SK-1s core and compile three sets of published datasets from two drilling holes (Zk3389 and LY-1) and a composite outcrop section. According to the total organic carbon (TOC) chemostratigraphy, we have divided three variation cycles spanning from K2n1 to K2n2 and detected three potential oil shale intervals in the Nenjiang Formation. Combined with the productivity, salinity, and oxygenation proxies, we discuss the paleolimnological environmental changes during deposition of the Nenjiang Formation. Our new and compiled records support the model that excellent preservation conditions were associated with the formation of organic-rich sediments in the K2n1, while the productivity was the major controlling factor for organic matter enrichment in the K2n2 . © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
cited By 1
Keywords: Deposition; Oil fields; Oil shale; Productivity; Depositional setting; Environmental change; Hydrocarbon source rocks; Organic carbon burial; Organic-rich sediment; Petroliferous basins; Preservation condition; Total Organic Carbon; Organic carbon

Contamination of the Bushveld Complex (South Africa) magmas by basinal brines: Stable isotopes in phlogopite from the UG2 chromitite - Zhou, Haoyang; Trumbull, Robert B; Veksler, Ilya V; Bindeman, Ilya N; Glodny, Johannes; Kaufmann, Felix ED; Rammlmair, Dieter (Geology, 2021)

Conceptualization and preliminary research on deep in situ rock mechanics; [深部原位岩石力学构想与初步探索] - Xie, Heping; Li, Cunbao; Gao, Mingzhong; Zhang, Ru; Gao, Feng; Zhu, Jianbo (Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering, 2021)
Deep earth science is the basic of deep resource exploitation. One critical challenge is to ascertain the physical and mechanical behaviours of rocks from different depths under in situ geological conditions. Rock mechanical experiments and theoretical studies suitable for shallow resource mining are difficult to consider the effects of deep in situ geological conditions of different buried depths on the rock physical and mechanical characteristics and engineering. This paper puts forward the concept and research content ofdeep in situ rock mechanics. Using rock cores collected from 10 different depths(1 000 m to 6 400 m) of Songke second well, the different characteristics of rock mechanical behaviors at different buried depths are studied. An in situ stress restoration and reconstruction method is proposed to approximately simulate the influence of in situ geostress on rock physical and mechanical parameters. Uniaxial compression tests indicate that rock mechanical parameters increase nonlinearly with increasing the buried depth and hence, cannot be treated as constants. Triaxial compression experimental results manifest that rock mechanical parameters vary more obviously with the buried depth due to the geostress, which is different from those under uniaxial compression. Rock mechanical tests retaining the in situ geological condition suggest that the rock mechanical parameters can present more obvious nonlinear behaviors with increasing the buried depth in the case of geostress restoration and reconstruction. The peak strength and Young's modulus in the in situ stress restoration and reconstruction tests, showing a logarithmic function relationship with the buried depth, are larger than the results in the triaxial compression tests. Also, the post peak strain softening behavior in the in situ stress restoration and reconstruction tests is more obvious than that in the triaxial compression tests. Especially, when the burial depth exceeds 4 800 m, the influences of in situ stress restoration and reconstruction on Poisson's ratio, strain hardening modulus and post peak are more remarkable. This research can provide support for exploring deep scientific laws and improving deep resource acquisition capabilities. © 2021, Science Press. All right reserved.
Keywords: Compression testing; Elastic moduli; Geology; Restoration; Rock mechanics; Strain hardening; Stresses; Logarithmic functions; Mechanical characteristics; Restoration and reconstruction; Rock mechanical parameters; Strain-hardening modulus; Tri-axial compression tests; Uni-axial compression; Uni-axial compression tests; Rocks

Comparison of stress orientation indicators in Chicxulub's peak ring: Kinked biotites, basal PDFs, and feather features - Ebert, M.; Poelchau, M.H.; Kenkmann, T.; Gulick, S.P.S.; Lofi, J.; McCall, N.; Rae, A.S.P. (Special Paper of the Geological Society of America, 2021)
During hypervelocity impacts, target rocks are subjected to shock wave compression with high pressures and differential stresses. These differential stresses cause microscopic shear-induced deformation, which can be observed in the form of kinking, twinning, fracturing, and shear faulting in a range of minerals. The orientation of these shear-induced deformation features can be used to constrain the maximum shortening axis. Under the assumption of pure shear deformation, the maximum shortening axis is parallel to the maximum principal axis of stress, σ1, which gives the propagation direction of the shock wave that passed through a rock sample. In this study, shocked granitoids cored from the uppermost peak ring of the Chicxulub crater (International Ocean Discovery Program [IODP]/International Continental Drilling Project [ICDP] Expedition 364) were examined for structures formed by shearing. Orientations of kink planes in biotite and basal planar deformation features (PDFs) in quartz were measured with a U-stage and compared to a previous study of feather feature orientations in quartz from the same samples. In all three cases, the orientations of the shortening axis derived from these measurements were in good agreement with each other, indicating that the shear deformation features all formed in an environment with similar orientations of the maximum principal axis of stress. These structures formed by shearing are useful tools that can aid in understanding the deformational effects of the shock wave, as well as constraining shock wave propagation and postshock deformation during the cratering process. © 2021 The Geological Society of America.
cited By 0

Clay mineralogical evidence for mid-latitude terrestrial climate change from the latest Cretaceous through the earliest Paleogene in the Songliao Basin, NE China - Gao, Y.; Ibarra, D.E.; Du, X.; Dong, T.; Liu, Z.; Wang, C. (Cretaceous Research, 2021)
From the latest Cretaceous (late Campanian to Maastrichtian, 76-66 Ma) through the earliest Paleogene, changes of greenhouse climate were linked to catastrophic geological events and massive biotic extinction and were primarily derived from marine records. Here we present a high-resolution, tightly age-constrained, clay mineralogical record from the Sifangtai and Mingshui formations of the terrestrial Songliao Basin, northeast China. Smectite and illite are the dominant clay species and are derived from the weathering of parent rocks and/or pedogenesis in paleosols. We use the percentage ratio of smectite and illite, the illite chemistry index, and the percentage ratio of phyllosilicate clay minerals and quartz in clay fractions for paleoclimatic reconstruction. Our results show that from the latest Cretaceous through the earliest Paleogene, values of all three clay mineralogical proxies in the Songliao Basin are generally higher during warming intervals than those during cooling intervals. This dataset suggests that warming caused strengthened moisture delivery from the Pacific, increasing precipitation and intensified chemical weathering, whereas cooling was accompanied by increasing dryness and physical weathering. Across the Cretaceous-Paleogene boundary, the warming likely related to Deccan volcanism, the transient cooling afterwards, and the warming in the earliest Paleogene are characterized by changes in the illite chemistry index and paleosol carbonate stable isotopic excursions as shown in previously published records, reflecting fluctuations in hydroclimate and weathering intensity. Our work demonstrates that terrestrial climate and weathering intensity in the mid-latitude Songliao Basin fluctuated during the latest Cretaceous through the earliest Paleogene and sensitively responded to global climate changes. © 2021 Elsevier Ltd
cited By 6
Keywords: clay mineral; climate variation; Cretaceous-Paleogene boundary; midlatitude environment; paleoclimate; terrestrial environment; weathering; China; Songliao Basin

Chronostratigraphy of the Baringo-Tugen Hills-Barsemoi (HSPDP-BTB13-1A) core – 40Ar/39Ar dating, magnetostratigraphy, tephrostratigraphy, sequence stratigraphy and Bayesian age modeling - Deino, Alan L.; Sier, Mark J.; Garello, Dominique I.; Keller, C. Brenhin; Kingston, John D.; Scott, Jennifer J.; Dupont-Nivet, Guillaume; Cohen, Andrew S. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2021)
The Baringo-Tugen Hills-Barsemoi 2013 drillcore (BTB13), acquired as part of the Hominin Sites and Paleolakes Drilling Project, recovered 228 m of fluvio-lacustrine sedimentary rocks and tuffs spanning a 3.29 –2.56 Ma interval of the highly fossiliferous and hominin-bearing Chemeron Formation, Tugen Hills, Kenya. Here we present a Bayesian stratigraphic age model for the core employing chronostratigraphic control points derived from 40Ar/39Ar dating of tuffs from core and outcrop, 40Ar/39Ar age calibration of related outcrop diatomaceous units, and core magnetostratigraphy. The age model reveals three main intervals with distinct sediment accumulation rates: an early rapid phase from 3.2 –2.9 Ma; a relatively slow phase from 2.9 –2.7 Ma; and the highest rate of accumulation from 2.7 –2.6 Ma. The intervals of rapid accumulation correspond to periods of high Earth orbital eccentricity, whereas the slow accumulation interval corresponds to low eccentricity at 2.9 –2.7 Ma, suggesting that astronomically mediated climate processes may be responsible for the observed changes in sediment accumulation rate. Lacustrine transgression-regression events, as delineated using sequence stratigraphy, dominantly operate on precession scale, particularly within the high eccentricity periods. A set of erosively based fluvial conglomerates correspond to the 2.9 –2.7 Ma interval, which could be related to either the depositional response to low eccentricity or to the development of unconformities due to local tectonic activity. Age calibration of core magnetic susceptibility and gamma density logs indicates a close temporal correspondence between a shift from high- to low-frequency signal variability at 3 Ma, approximately coincident the end of the mid-Piacenzian Warm Period, and the beginning of the cooling of world climate leading to the initiation of Northern Hemispheric glaciation c. 2.7 Ma. BTB13 and the Baringo Basin records may thus provide evidence of a connection between high-latitude glaciation and equatorial terrestrial climate toward the end of the Pliocene. © 2019 Elsevier B.V.
Keywords: Baringo; Kenya; Tugen Hills; Bayesian analysis; chronostratigraphy; dating method; eccentricity; magnetic susceptibility; magnetostratigraphy; modeling; outcrop; sedimentary rock; sequence stratigraphy

Chicxulub impact structure, IODP-ICDP Expedition 364 drill core: Geochemistry of the granite basement - Feignon, J.-G.; Graaff, S.J.; Ferrière, L.; Kaskes, P.; D'ehais, T.; Goderis, S.; Claeys, P.; Koeberl, C. (Meteoritics and Planetary Science, 2021)
The IODP-ICDP Expedition 364 drilling recovered a 829 m core from Hole M0077A, sampling 600 m of near continuous crystalline basement within the peak ring of the Chicxulub impact structure. The bulk of the basement consists of pervasively deformed, fractured, and shocked granite. Detailed geochemical investigations of 41 granitoid samples, that is, major and trace element contents, and Sr-Nd isotopic ratios are presented here, providing a broad overview of the composition of the granitic crystalline basement. Mainly granite but also granite clasts (in impact melt rock), granite breccias, and aplite were analyzed, yielding relatively homogeneous compositions between all samples. The granite is part of the high-K, calc-alkaline metaluminous series. Additionally, they are characterized by high Sr/Y and (La/Yb)N ratios, and low Y and Yb contents, which are typical for adakitic rocks. However, other criteria (such as Al2O3 and MgO contents, Mg#, K2O/Na2O ratio, Ni concentrations, etc.) do not match the adakite definition. Rubidium –Sr errorchron and initial 87Sr/86Srt=326Ma suggest that a hydrothermal fluid metasomatic event occurred shortly after the granite formation, in addition to the postimpact alteration, which mainly affected samples crosscut by shear fractures or in contact with aplite, where the fluid circulation was enhanced, and would have preferentially affected fluid-mobile element concentrations. The initial (ɛNd)t=326Ma values range from −4.0 to 3.2 and indicate that a minor Grenville basement component may have been involved in the granite genesis. Our results are consistent with previous studies, further supporting that the cored granite unit intruded the Maya block during the Carboniferous, in an arc setting with crustal melting related to the closure of the Rheic Ocean associated with the assembly of Pangea. The granite was likely affected by two distinct hydrothermal alteration events, both influencing the granite chemistry: (1) a hydrothermal metasomatic event, possibly related to the first stages of Pangea breakup, which occurred approximately 50 Myr after the granite crystallization, and (2) the postimpact hydrothermal alteration linked to a long-lived hydrothermal system within the Chicxulub structure. Importantly, the granites sampled in Hole M0077A are unique in composition when compared to granite or gneiss clasts from other drill cores recovered from the Chicxulub impact structure. This marks them as valuable lithologies that provide new insights into the Yucat'an basement. © 2021 The Authors. Meteoritics & Planetary Science published by Wiley Periodicals LLC on behalf of The Meteoritical Society (MET)
cited By 3

Characterizing Hydration of the Ocean Crust Using Shortwave Infrared Microimaging Spectroscopy of ICDP Oman Drilling Project Cores - Crotteau, Molly A; Greenberger, Rebecca N; Ehlmann, Bethany L; Rossman, George R; Harris, Michelle; Kelemen, Peter B; Teagle, Damon AH; Party, Oman Drilling Project Phase 1 Science (Journal of Geophysical Research: Solid Earth, 2021)
Although ocean crust covers over 60% of Earth's surface, the processes that form, cool, and alter the ocean crust are not completely understood. We utilize shortwave infrared micro-imaging spectroscopy of ∼1.2 km of rock cored by the International Continental Scientific Drilling Program's Oman Drilling Project to quantify hydration of basaltic dikes and gabbros from the Samail ophiolite as a function of depth, mineralogy and deformation. We develop a regression (R2 = 0.66) between area of the ∼1,350 –1,650 nm OH/H2O absorption and measurements of loss on ignition of samples and apply this relationship to generate quantitative ∼250 μm/pixel hydration maps for all cores. The lowest mean hydration is observed in the most pervasively altered dike-gabbro boundary (GT3A, H2Omean = 2.1 ± 1.6 wt%), consistent with the low H2O content of the dominant alteration minerals, amphibole and epidote. The highest H2O content occurs in deeper foliated and layered gabbros (GT2A, H2Omean = 3.2 ± 3.0 wt%) and layered gabbros (GT1A, H2Omean = 2.8 ± 3.1 wt%). The greater prevalence with depth of zeolite alteration as opposed to lower wt% H2O amphibole at shallow stratigraphic depths, as well as the occurrence of zones of intensive hydration associated with fault zones (H2Omean = 5.7 ± 4.0 wt%) lead to greater hydration of the lower ocean crust. This new approach provides an objective quantification of hydration in these cores, enabling an improved understanding of quantities and characteristics of ocean crust hydration. It highlights the importance of specific phases and faulting in controlling hydration, which has implications for ocean crust cooling, rheological properties, and the role of alteration in global biogeochemical cycling. © 2021. The Authors.
cited By 0
Keywords: dike; drilling; gabbro; hydration; infrared spectroscopy; oceanic crust; ophiolite; shortwave radiation

Carbon Geochemistry of the Active Serpentinization Site at the Wadi Tayin Massif: Insights From the ICDP Oman Drilling Project: Phase II - Ternieten, Lotta; Fr{uh-Green, Gretchen L; Bernasconi, Stefano M (Journal of Geophysical Research: Solid Earth, 2021)
A large part of the hydrated oceanic lithosphere consists of serpentinites exposed in ophiolites. Serpentinites constitute reactive chemical and thermal systems and potentially represent an effective sink for CO2. Understanding carbonation mechanisms within ophiolites are almost exclusively based on studies of outcrops, which can limit the interpretation of fossil hydrothermal systems. We present stable and radiogenic carbon isotope data that provide insights into the isotopic trends and fluid evolution of peridotite carbonation in ICDP Oman Drilling Project drill holes BA1B (400-m deep) and BA3A (300-m deep). Geochemical investigations of the carbonates in serpentinites indicate formation in the last 50 kyr, implying a distinctly different phase of alteration than the initial oceanic hydration and serpentinization of the Samail Ophiolite. The oldest carbonates (∼31 to >50 kyr) are localized calcite, dolomite, and aragonite veins, formed between 26°C and 43°C and related to focused fluid flow. Subsequent pervasive small amounts of dispersed carbonate precipitated in the last 1,000 years. Macroscopic brecciation and veining of the peridotite indicate that carbonation is influenced by tectonic features allowing infiltration of fluids over extended periods and at different structural levels such as along fracture planes and micro-fractures and grain boundaries, causing large-scale hydration of the ophiolite. The formation of dispersed carbonate is related to percolating fluids with δ18O lower than modern ground and meteoric water. Our study shows that radiocarbon investigations are an essential tool to interpret the carbonation history and that stable oxygen and carbon isotopes alone can result in ambiguous interpretations. © 2021 The Authors.
cited By 3
Keywords: carbon cycle; carbon sequestration; carbonate; drilling; hydrothermal system; radiocarbon dating; serpentinization; temperature anomaly; Oman

Cyclostratigraphy and paleoenvironmental inference from downhole logging of sediments in tropical Lake Towuti, Indonesia - Ulfers, A.; Hesse, K.; Zeeden, C.; Russell, J.M.; Vogel, H.; Bijaksana, S.; Wonik, T. (Journal of Paleolimnology, 2021)
Lake Towuti is located on central Sulawesi/Indonesia, within the Indo Pacific Warm Pool, a globally important region for atmospheric heat and moisture budgets. In 2015 the Towuti Drilling Project recovered more than 1000 m of drill core from the lake, along with downhole geophysical logging data from two drilling sites. The cores constitute the longest continuous lacustrine sediment succession from the Indo Pacific Warm Pool. We combined lithological descriptions with borehole logging data and used multivariate statistics to better understand the cyclic sequence, paleoenvironments, and geochronology of these sediments. Accurate chronologies are crucial to analyze and interpret paleoclimate records. Astronomical tuning can help build age-depth models and fill gaps between age control points. Cyclostratigraphic investigations were conducted on a downhole magnetic susceptibility log from the lacustrine facies (10 –98 m below lake floor) from a continuous record of sediments in Lake Towuti. This study provides insights into the sedimentary history of the basin between radiometric ages derived from dating a tephra layer ( 797 ka) and C14-ages ( 45 ka) in the cores. We derived an age model that spans from late marine isotope stage (MIS) 23 to late MIS 6 (903 ± 11 to 131 ± 67 ka). Although uncertainties caused by the relatively short record and the small differences in the physical properties of sediments limited the efficacy of our approach, we suggest that eccentricity cycles and/or global glacial-interglacial climate variability were the main drivers of local variations in hydroclimate in central Indonesia. We generated the first nearly complete age-depth model for the lacustrine facies of Lake Towuti and examined the potential of geophysical downhole logging for time estimation and lithological description. Future lake drilling projects will benefit from this approach, since logging data are available just after the drilling campaign, whereas core descriptions, though more resolved, only become available months to years later. © 2021, The Author(s).
Keywords: Greater Sunda Islands; Lake Towuti; Malili Lakes; South Sulawesi; Sulawesi; Sunda Isles; borehole logging; cyclostratigraphy; eccentricity; facies analysis; lacustrine deposit; magnetic susceptibility; marine isotope stage; moisture content; paleoclimate; proxy climate record; tephra; warm pool

Active Basalt Alteration at Supercritical Conditions in a Seawater-Recharged Hydrothermal System: IDDP-2 Drill Hole, Reykjanes, Iceland - Zierenberg, Robert A.; Friðleifsson, Guðmundur Ó.; Elders, Wilfred A.; Schiffman, Peter; Fowler, Andrew P. G. (Geochemistry, Geophysics, Geosystems, 2021)

A New Approach to Constrain the Seismic Origin for Prehistoric Turbidites as Applied to the Dead Sea Basin - Lu, Y.; Moernaut, J.; Bookman, R.; Waldmann, N.; Wetzler, N.; Agnon, A.; Marco, S.; Alsop, G.I.; Strasser, M.; Hubert-Ferrari, A. (Geophysical Research Letters, 2021)
The seismic origin of turbidites is verified either by correlating such layers to historic earthquakes, or by demonstrating their synchronous deposition in widely spaced, isolated depocenters. A historic correlation could thus constrain the seismic intensity required for triggering turbidites. However, historic calibration is not applicable to prehistoric turbidites. In addition, the synchronous deposition of turbidites is difficult to test if only one deep core is drilled in a depocenter. Here, we propose a new approach that involves analyzing the underlying in situ deformations of prehistoric turbidites, as recorded in a 457 m-long core from the Dead Sea center, to establish their seismic origin. These in situ deformations have been verified as seismites and could thus authenticate the trigger for each overlying turbidite. Moreover, our high-resolution chemical and sedimentological data validate a previous hypothesis that soft-sediment deformation in the Dead Sea formed at the sediment-water interface. © 2020. The Authors.
cited By 14
Keywords: Deformation; Deposition; Dead sea basins; High resolution; Sediment water interface; Sedimentological data; Seismic intensity; Seismic origin; Situ deformation; Soft-sediment deformation; Earthquakes

A python code for automatic construction of Fischer plots using proxy data - Yang, D.; Huang, Y.; Chen, Z.; Huang, Q.; Ren, Y.; Wang, C. (Scientific Reports, 2021)
Fischer plots are widely used in paleoenvironmental research as graphic representations of sea- and lake-level changes through mapping linearly corrected variation of accumulative cycle thickness over cycle number or stratum depth. Some kinds of paleoenvironmental proxy data (especially subsurface data, such as natural gamma-ray logging data), which preserve continuous cyclic signals and have been largely collected, are potential materials for constructing Fischer Plots. However, it is laborious to count the cycles preserved in these proxy data manually and map Fischer plots with these cycles. In this paper, we introduce an original open-source Python code “PyFISCHERPLOT” for constructing Fischer Plots in batches utilizing paleoenvironmental proxy data series. The principle of constructing Fischer plots based on proxy data, the data processing and usage of the PyFISCHERPLOT code and the application cases of the code are presented. The code is compared with existing methods for constructing Fischer plots. © 2021, The Author(s).
cited By 2
Keywords: article

A review of the 1999 Chi-Chi, Taiwan, earthquake from modeling, drilling, and monitoring with the Taiwan Chelungpu-fault drilling Project - Ma, Kuo-Fong (Earthquake Geology and Tectonophysics around Eastern Tibet and Taiwan, 2021)

A Volcanic Ash Layer in the N{ordlinger Ries Impact Structure (Miocene, Germany): Indication of Crater Fill Geometry and Origins of Long-Term Crater Floor Sagging - Arp, G.; Dunkl, I.; Jung, D.; Karius, V.; Luk'acs, R.; Zeng, L.; Reimer, A.; Head, III (Journal of Geophysical Research: Planets, 2021)
Since its recognition as an impact structure 60 years ago, no volcanics were anticipated in the circular depression of the 14.8 Ma old N{ordlinger Ries. Here, we describe for the first time a volcanic ash-derived clinoptilolite-heulandite-buddingtonite bed within the 330 m thick Miocene lacustrine crater fill. Zircon U-Pb ages of 14.20 ± 0.08 Ma point to the source of the volcanic ash in the Pannonian Basin, 760 km east of the Ries. The diagenetically derived zeolite-feldspar bed occurs in laminated claystones of the Ries soda-lake stage and represents the first unequivocal stratigraphic marker bed in this basin, traceable from marginal surface outcrops to 218 m below surface in the crater center. These relationships demonstrate a deeply bowl-shaped geometry of crater fill sediments, not explainable by sediment compaction and corresponding stratigraphic backstripping alone. Since most of the claystones formed at shallow water depths, the bowl-shaped geometry must reflect 134 +23/−49 m of sagging of the crater floor. We attribute the sagging to compaction and closure of the dilatant macro-porosity of the deeply fractured and brecciated crater floor during basin sedimentation and loading, a process that lasted for more than 0.6 Myr. As a result, the outcrop pattern of the lithostratigraphic crater-fill units in its present erosional plane forms a concentric pattern. Recognition of this volcanic ash stratigraphic marker in the Ries crater provides insights into the temporal and stratigraphic relationships of crater formation and subsidence that have implications for impact-hosted lakes on Earth and Mars. © 2021. The Authors.
cited By 4

Accessing the subsurface biosphere within rocks undergoing active low-temperature serpentinization in the Samail ophiolite (Oman Drilling Project) - Templeton, Alexis S; Ellison, Eric T; Glombitza, Clemens; Morono, Yuki; Rempfert, Kaitlin R; Hoehler, Tori M; Zeigler, Spencer D; Kraus, Emily A; Spear, John R; Nothaft, Daniel B; et al. (Journal of Geophysical Research: Biogeosciences, 2021)

Achievements and Future Prospects of the ICDP Oman Drilling Project - Takazawa, E. (Journal of Geography (Chigaku Zasshi), 2021)
The ICDP Oman Drilling Project carried out onshore drilling of the world's largest ophiolite, the Oman ophiolite (also known as Samail ophiolite). This drilling project provided an opportunity to explore major key boundaries of the oceanic lithosphere, represented by the Oman ophiolite, by drilling cores and boreholes. Below the layered gabbro at the bottom of the crustal section is the Moho Transition Zone(MTZ), which is mainly composed of dunite with small amounts of gabbroic sills. By drilling at the Wadi Zeeb CM site in the Wadi Tayin massif, cores were successfully collected from a 150 m MTZ. Also collected were fragile altered rocks from wadi outcrops that are easily lost. The core description campaign was carried out aboard deep-sea scientific drilling vessel “Chikyu” anchored at Shimizu Port. The core observations were performed and described according to the IODP procedure, and the analysis was conducted using many instruments. The resulting data provide important insights and will contribute to future drilling of the Mohorovicic discontinuity in the ocean. The most striking fact is that MTZ dunites are strongly influenced by serpentinization. In particular, the upper part of the MTZ just below the boundary with the lower crustal gabbro was most strongly altered, and a fracture zone was also developed. Understanding when and how these alterations occurred at the boundary between the crust and the mantle is an important future task. © 2021. All Rights Reserved.
cited By 2

Advanced Hyperspectral Analysis of Sediment Core Samples from the Chew Bahir Basin, Ethiopian Rift, in the Spectral Range from 0.25 to 17 µm: Support for Climate Proxy Interpretation - Arnold, Gabriele E.; Foerster, Verena; Trauth, Martin H.; Lamb, Henry; Schaebitz, Frank; Asrat, Asfawossen; Szczech, Claudia; G{unter, Christina (Frontiers in Earth Science, 2021)

Basalt-Hosted Microbial Communities in the Subsurface of the Young Volcanic Island of Surtsey, Iceland - Bergsten, Pauline; Vannier, Pauline; Klonowski, Alexandra Maria; Knobloch, Stephen; Gudmundsson, Magn'us Tumi; Jackson, Marie Dolores; Marteinsson, Vigg'o Th'or (Frontiers in microbiology, 2021)

Afar Dallol Drilling-ONset of sedimentary processes in an active rift basin (ADD-ON): Scientific drilling targets in the Afar (Ethiopia) - Foubert, Anneleen; Kidane, Tesfaye; Keir, Derek; Atnafu, Balemwal; et al. (EGU General Assembly Conference Abstracts, 2021)

AN UNBROKEN RECORD OF CLIMATE DURING THE AGE OF DINOSAURS: A scientific drilling project in China has retrieved a continuous history of conditions from Earth’s most recent “greenhouse” period that may offer insights about future climate scenarios - Wang, C.; Gao, Y.; Ibarra, D.E.; Wu, H.; Wang, P. (Eos (United States), 2021)
cited By 8
Keywords: climate variation; Cretaceous; future prospect; paleoclimate; China

Analysis of aluminum alloy drill pipe corrosion based on COMSOL (in Chinese with English abstract);[基于COMSOL的铝合金钻杆腐蚀分析] - Liang, J.; Zhao, J.; Wang, C.; He, X.; Yin, H. (Drilling Engineering, 2021)

Analysis of pyrite framboids in Nenjing Formation, Songliao Basin.and implications for the redox conditions of paleolake (in Chinese with English abstract); [松辽盆地嫩江组草莓状黄铁矿及其古环境意义] - Wang, T.; Huang, Y.; Zhang, Z.; Wang, C. (Journal of Shandong University of Science and Technology (Natural Science), 2021)

Aqueous geochemical and microbial variation across discrete depth intervals in a peridotite aquifer assessed using a packer system in the Samail Ophiolite, Oman - Nothaft, Daniel B; Templeton, Alexis S; Boyd, Eric S; Matter, Juerg M; Stute, Martin; Paukert Vankeuren, Amelia N; Team, Oman Drilling Project Science (Journal of Geophysical Research: Biogeosciences, 2021)

Assessing event magnitude and target water depth for marine-target impacts: Ocean resurge deposits in the Chicxulub M0077A drill core compared - Orm{o, J.; Gulick, S.P.S.; Whalen, M.T.; King, Jr.; Sturkell, E.; Morgan, J. (Earth and Planetary Science Letters, 2021)
The rim wall of water formed from even a modestly-sized marine impact may be kilometers in height. Although modeling has shown that this wave swiftly breaks and relatively rapidly loses energy during outwards travel from the impact site, the portion of the rim wall that collapses inwards may generate a resurge flow with tremendous transport energy. Here we compare the deposits generated by this ocean resurge inside one of the largest marine-target craters on Earth, the 200-km wide Chicxulub crater, Yucat'an Peninsula, M'exico, with resurge deposits (breccias) in eight drill cores from five other marine-target craters in Sweden and the United States. Examination of the wide range of cored locations within the craters, and target water depths (H) relative to modeled projectile diameters (d) reveal a high correlation between location, average clast frequency (〈N〉), and d/H from which any of the four variables can be obtained. The relationship shown here may provide an important tool for diagnosing marine impact cratering processes where there is limited understanding of crater size and/or paleobathymetry. © 2021 The Authors
cited By 8

Cryptotephras in the Lateglacial ICDP Dead Sea sediment record and their implications for chronology - Neugebauer, I.; M{uller, D.; Schwab, M.J.; Blockley, S.; Lane, C.S.; Wulf, S.; Appelt, O.; Brauer, A. (Boreas, 2021)
Due to a lack of visible tephras in the Dead Sea record, this unique palaeoenvironmental archive is largely unconnected to the well-established Mediterranean tephrostratigraphy. Here we present first results of the ongoing search for cryptotephras in the International Continental Drilling Program (ICDP) sediment core from the deep Dead Sea basin. This study focusses on the Lateglacial ( 15 –11.4 cal. ka BP), when Lake Lisan – the precursor of the Dead Sea – shrank from its glacial highstand to the Holocene low levels. We developed a glass shard separation protocol and counting procedure that is adapted to the extreme salinity and sediment recycling of the Dead Sea. Cryptotephra is abundant in the Dead Sea record (up to 100 shards cm-3), but often glasses are physically and/or chemically altered. Six glass samples from five tephra horizons reveal a heterogeneous geochemical composition, with mainly rhyolitic and some trachytic glasses potentially sourced from Italian, Aegean and Anatolian volcanoes. Most shards likely originate from the eastern Anatolian volcanic province and can be correlated using major element analyses with tephra deposits from swarm eruptions of the S{uphan Volcano 13 ka BP and with ashes from Nemrut Volcano, presumably the Lake Van V-16 volcanic layer at 13.8 ka BP. In addition to glasses that match the TM-10-1 from Lago Grande di Monticchio (15 820±790 cal. a BP) tentatively correlated with the St. Angelo Tuff of Ischia, we further identified a cryptotephra with glass analyses which are chemically identical with those of the PhT1 tephra in the Philippon peat record (13.9 –10.5 ka BP), and also a compositional match for the glass analyses of the Santorini Cape Riva Tephra (Y-2 marine tephra, 22 024±642 cal. a BP). These first results demonstrate the great potential of cryptotephrochronology in the Dead Sea record for improving its chronology and connecting the Levantine region to the Mediterranean tephra framework. © 2021 The Authors. Boreas published by John Wiley & Sons Ltd on behalf of The Boreas Collegium.
cited By 3
Keywords: geological record; Holocene; KTB borehole; late glacial; paleoenvironment; sediment core; tephra; tephrochronology; Dead Sea

A million year vegetation history and palaeoenvironmental record from the Lake Magadi Basin, Kenya Rift Valley - Muiruri, Veronica M.; Owen, R. Bernhart; Lowenstein, Tim K.; Renaut, Robin W.; Marchant, Robert; Rucina, Stephen M.; Cohen, Andrew; Deino, Alan L.; Sier, Mark J.; Luo, Shangde; Leet, Kennie; Campisano, Christopher; et al. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2021)
This study examines a one-million-year pollen record from a 194-m-long Lake Magadi core (HSPDP-MAG14-2A) in the south Kenya Rift Valley. The pollen indicate a general trend through the last 740 kyr from wetter conditions to generally drier environments. Grassland dominated with less common Podocarpus and Cyperaceae in a sparse flora between 1000 and 740 ka. Poaceae, woodland and herbaceous plants are common through the remaining core and abundant between 740 and 528 ka and after 200 ka. Pollen diversity increased after 200 ka. Podocarpus and Cyperaceae reached a peak abundance at 575 ka with a subsequent decline that suggests a progressive increase in aridity, interrupted by wetter intervals. Podocarpus-dominated forests expanded and contracted many times during the Quaternary and document an anti-phased relationship with data from Lake Malawi. Similar anti-phased correlations are noted for herbaceous plants, suggesting that the two basins responded differently to the same climate or were influenced by contrasting climate regimes. Increases in macrocharcoal correlate with increasing pollen abundance and suggest wetter conditions. Data from the Magadi, Koora and Olorgesailie basins indicate similar trends and a dominant climate control on vegetation and habitats. Large lakes characterised all three basins at 740 –528 ka with climate subsequently becoming drier, but with many wetter intervals. At various times the lakes expanded, contracted and dried out, except at Lake Magadi where spring inflows maintained lacustrine conditions through the late Quaternary. Faulting also contributed to fragmentation of the landscape and formation of a mosaic of habitats. An especially intense period of aridity at 528 –392 ka coincided with extinction of many large-bodied mammals and may have helped to drive a change from the use of Acheulean hand axes to the production of Middle Stone Age tools by 320 ka. After 200 ka pollen diversity increased substantially with a mix of montane, riparian and dry forest associations that were present in varying amounts through to 4.2 ka at the core top. © 2021 Elsevier B.V.
Keywords: East African Lakes; East African Rift; Kajiado; Kenya; Kenya Rift; Lake Magadi; Lake Malawi; Rift Valley; Cyperaceae; Mammalia; Poaceae; Podocarpus; Acheulean; dry forest; extinction; grassland; habitat fragmentation; habitat mosaic; historical record; mammal; Mesolithic; paleoenvironment; pollen; vegetation history

Dendritic reidite from the Chesapeake Bay impact horizon, Ocean Drilling Program Site 1073 (offshore northeastern USA): A fingerprint of distal ejecta? - Cavosie, A.J.; Biren, M.B.; Hodges, K.V.; Wartho, J.-A.; Horton Jr., J.W.; Koeberl, C. (Geology, 2021)
High-pressure minerals provide records of processes not normally preserved in Earth's crust. Reidite, a quenchable polymorph of zircon, forms at pressures >20 GPa during shock compression. However, there is no broad consensus among empirical, experimental, and theoretical studies on the nature of the polymorphic transformation. Here we decipher a multistage history of reidite growth recorded in a zircon grain in distal impact ejecta (offshore northeastern United States) from the ca. 35 Ma Chesapeake Bay impact event which, remarkably, experienced near-complete conversion (89%) to reidite. The grain displays two distinctive reidite habits: (1) intersecting sets of planar lamellae that are dark in cathodoluminescence (CL); and (2) dendritic epitaxial overgrowths on the lamellae that are luminescent in CL. While the former is similar to that described in literature, the latter has not been previously reported. A two-stage growth model is proposed for reidite formation at >40 GPa in Chesapeake Bay impact ejecta: formation of lamellar reidite by shearing during shock compression, followed by dendrite growth, also at high pressure, via recrystallization. The dendritic reidite is interpreted to nucleate on lamellae and replace damaged zircon adjacent to lamellae, which may be amorphous ZrSiO4 or possibly an intermediate phase, all before quenching. These results provide new insights on the microstructural evolution of the high-pressure polymorphic transformation over the microseconds-long interval of reidite stability during meteorite impact. Given the formation conditions, dendritic reidite may be a unique indicator of distal ejecta. © 2020 Geological Society of America.
cited By 4
Keywords: Offshore drilling; Offshore oil well production; Semiconductor insulator boundaries; Silicate minerals; Structural geology; Zircon; Epitaxial overgrowth; Formation condition; Intermediate phase; Meteorite impact; Ocean drilling programs; Polymorphic transformation; Shock compressions; Theoretical study; Meteor impacts; ejecta; high pressure; microstructure; mineral resource; Ocean Drilling Program; zircon; Chesapeake Bay; United States; Indicator indicator

Insight Into Hartoušov Mofette, Czech Republic: Tales by the Fluids - Daskalopoulou, Kyriaki; Woith, Heiko; Zimmer, Martin; Niedermann, Samuel; Barth, Johannes A. C.; Frank, Alexander H.; Vieth-Hillebrand, Andrea; Vlček, Josef; Bağ, Cemile Dilara; Bauz, Ralf (Frontiers in Earth Science, 2021)
The Cheb Basin (Czech Republic) is characterized by emanations of magma-derived gases and repeated occurrences of mid-crustal earthquake swarms with small to intermediate magnitudes (ML < 4.5). Associated intense mantle degassing occurs at the Hartoušov Mofette, a representative site for the Cheb Basin. Here, we performed 14 sampling campaigns between June 2019 and March 2020. Gas samples of fluids ascending in two boreholes (F1, ∼28 m depth and F2, ∼108 m depth) and from a nearby natural mofette were analyzed for their chemical (CO2, N2, O2, Ar, He, CH4, and H2) and isotope compositions (noble gases and CO2). CO2 concentrations were above 99.1% in most samples, while O2 and N2 were below 0.6%. He ranged from 19 to 34 μmol/mol and CH4 was mostly below 12 μmol/mol. Isotope compositions of helium and carbon in CO2 ranged from 5.39 to 5.86 RA and from −2.4 to −1.3 ‰ versus VPDB, respectively. Solubility differences of the investigated gases resulted in fluctuations of their chemical compositions. These differences were accompanied by observed changes of gas fluxes in the field and at the monitoring station for F1. Variations in solubilities and fluxes also impacted the chemical concentration of the gases and the δ13C values that were also likely influenced by Fischer-Tropsch type reactions. The combination of (a) the Bernard ratio, (b) CH4/3He distributions, (c) P-T conditions, (d) heat flow, and (e) the sedimentary regime led to the hypothesis that CH4 may be of mixed biogenic and volcanic/geothermal origin with a noticeable atmospheric contribution. The drilling of a third borehole (F3) with a depth of ∼238 m in August 2019 has been crucial for providing insights into the complex system of Hartoušov Mofette. © Copyright © 2021 Daskalopoulou, Woith, Zimmer, Niedermann, Barth, Frank, Vieth-Hillebrand, Vlček, Bağ and Bauz.
Keywords: Cheb Basin; Czech Republic; Karlovarsky; Atmospheric movements; Boreholes; Chemical analysis; Earthquakes; Inert gases; Isotopes; Solubility; Atmospheric contributions; Chemical compositions; Chemical concentrations; CO2 concentration; Crustal earthquakes; Isotope compositions; Monitoring stations; Sampling campaigns; carbon; carbon dioxide; carbon flux; concentration (composition); degassing; helium; isotopic composition; magma; mantle structure; solubility; Carbon dioxide

Hydroclimate changes in eastern Africa over the past 200,000 years may have influenced early human dispersal - Schaebitz, Frank; Asrat, Asfawossen; Lamb, Henry F.; Cohen, Andrew S.; Foerster, Verena; Duesing, Walter; Kaboth-Bahr, Stefanie; Opitz, Stephan; Viehberg, Finn A.; Vogelsang, Ralf; Dean, Jonathan; Leng, Melanie J.; et al. (Communications Earth and Environment, 2021)

Hydrogen Production from Alteration of Chicxulub Crater Impact Breccias: Potential Energy Source for a Subsurface Microbial Ecosystem - Kring, D.A.; Bach, W. (Astrobiology, 2021)
A sulfate-reducing population of thermophiles grew in porous, permeable niches within glass-bearing impact breccias of the Chicxulub impact crater. The microbial community grew in an impact-generated hydrothermal system that vented on the seafloor several hundred meters beneath the sea surface. Potential electron donors for that metabolism are hydrocarbons, although a strong C-isotope signature of that source does not exist. Model calculations explored here suggest that alteration of glass within the impact breccias may have produced H2 in sufficient quantities for population growth as the hydrothermal system cooled through thermophilic temperatures, although it is sensitive to the oxidation state of iron in the melt rock prior to hydrothermal alteration and the secondary mineral assemblage. At high water-to-rock ratios and temperatures below 45°C, H2 yields are insufficient to maintain a population of hydrogenotrophic sulfate-reducing bacteria, but yields double with a higher proportion of ferrous iron between 45 and 65°C. The most reduced rocks (i.e., highest proportion of ferrous iron) that are allowed to form andradite, which is observed in core samples, produce copious amounts of H2 in the temperature window for thermophiles and hyperthermophiles. Mixtures of melt rock and carbonate, which is observed in breccia matrices, produce somewhat less H2, and the onset of massive H2 production is shifted to higher temperatures (i.e., lower W/R). © Copyright 2021, Mary Ann Liebert, Inc., publishers 2021.
cited By 1

Hydrometeorological analysis and forecasting of a 3 d flash-flood-Triggering desert rainstorm - Rinat, Yair; Marra, Francesco; Armon, Moshe; Metzger, Asher; Levi, Yoav; Khain, Pavel; Vadislavsky, Elyakom; Rosensaft, Marcelo; Morin, Efrat (Natural Hazards and Earth System Sciences, 2021)

Hydrothermal alteration of the ocean crust and patterns in mineralization with depth as measured by micro-imaging infrared spectroscopy - Greenberger, Rebecca N; Harris, Michelle; Ehlmann, Bethany L; Crotteau, Molly A; Kelemen, Peter B; Manning, Craig E; Teagle, Damon AH; Team, Oman Drilling Project Science (Journal of Geophysical Research: Solid Earth, 2021)
Processes for formation, cooling, and altering Earth's ocean crust are not yet completely understood due to challenges in access and sampling. Here, we use contiguous micro-imaging infrared spectroscopy to develop complete-core maps of mineral occurrence and investigate spatial patterns in the hydrothermal alteration of 1.2 km of oceanic crust recovered from Oman Drilling Project Holes GT1A, GT2A, and GT3A drilled in the Samail Ophiolite, Oman. The imaging spectrometer shortwave infrared sensor measured reflectance of light at wavelengths 1.0 –2.6 μm at 250 –260 μm/pixel, resulting in >1 billion independent measurements. We map distributions of nine key primary and secondary minerals/mineral groups–clinopyroxene, amphibole, calcite, chlorite, epidote, gypsum, kaolinite/montmorillonite, prehnite, and zeolite–and find differences in their spatial occurrences and pervasiveness. Accuracy of spectral mapping of occurrence is 68% –100%, established using X-ray diffraction measurements from the core description. The sheeted dikes and gabbros of upper oceanic crust Hole GT3A show more pervasive alteration and alteration dominated by chlorite, amphibole, and epidote. The foliated/layered gabbros of GT2A from intermediate crustal depths have similarly widespread chlorite but more zeolite and little amphibole and epidote. The layered gabbros of the lower oceanic crust (GT1A) have remnant pyroxene and 2X less chlorite, but alteration is extensive within and surrounding major fault zones with widespread occurrences of amphibole. The results indicate greater distribution of higher temperature alteration minerals in the upper oceanic crust relative to deeper gabbros and highlight the importance of fault zones in hydrothermal convection in the lower ocean crust. © 2021. The Authors.
cited By 3
Keywords: dike; gabbro; hydrothermal alteration; imaging method; infrared spectroscopy; mineralization; multispectral image; oceanic crust; Oman

Ichnology, sedimentology, and orbital cycles in the hemipelagic Early Jurassic Laurasian Seaway (Pliensbachian, Cardigan Bay Basin, UK) - Pie'nkowski, Grzegorz; Uchman, Alfred; Ninard, Krzysztof; Hesselbo, Stephen P. (Global and Planetary Change, 2021)

Initial Results From the Oman Drilling Project Multi-Borehole Observatory: Petrogenesis and Ongoing Alteration of Mantle Peridotite in the Weathering Horizon - Kelemen, Peter B; Leong, James A; Obeso, Juan; Matter, J{urg M; Ellison, Eric T; Templeton, Alexis; Nothaft, Daniel B; Eslami, Alireza; Evans, Katy; Godard, Marguerite; et al. (Journal of Geophysical Research: Solid Earth, 2021)

Iron Mineralogy and Sediment Color in a 100 m Drill Core From Lake Towuti, Indonesia Reflect Catchment and Diagenetic Conditions - Sheppard, Rachel Y.; Milliken, Ralph E.; Russell, James M.; Sklute, Elizabeth C.; Dyar, M. Darby; Bijaksana, Satria; Hasberg, Ascelina K. M.; Morlock, Marina A. (Geochemistry, Geophysics, Geosystems, 2021)
Iron is the most abundant redox-sensitive element on the Earth's surface, and the oxidation state, mineral host, and crystallinity of Fe-rich phases in sedimentary systems can record details of water-rock interactions and environmental conditions. However, we lack a complete understanding of how these Fe-rich materials are created, maintained, and oxidized or reduced in sedimentary environments, particularly those with mafic sources. The catchment of Lake Towuti, Indonesia, is known to contain a wide range of abundant crystalline Fe oxide, and the lake has a long sedimentary history. Here, we study a ∼100 m long drill core from the lake to understand patterns of sedimentation and how young iron-rich sediments are affected by diagenesis through geologic time. We use visible/near infrared and M{ossbauer spectroscopy, X-ray diffraction, bulk chemistry measurements, and statistical cluster analysis to characterize the core sediment. We find that the core sediment can be divided into three statistically different zones dominated by Mg serpentine, Al clay minerals, and Fe2+ carbonate, respectively. The entire core is rich in nanophase Fe, and elemental correlations and Fe mineralogy vary between these zones. The nanophase Fe is highly complex with both ferrous and ferric components, and contributes to, but does not dictate, variations in sediment color. We propose that the distinctive zones are the result of structural basin changes (notably river capture and shifting drainage patterns), and diagenetic overprinting caused by deep burial of reactive Fe. This complex record has implications for disentangling depositional and diagenetic trends in other mafic lacustrine systems. © 2021. American Geophysical Union. All Rights Reserved.
Keywords: Greater Sunda Islands; Lake Towuti; Malili Lakes; South Sulawesi; Sulawesi; Sunda Isles; Catchments; Chemical analysis; Cluster analysis; Crystallinity; Drills; Infill drilling; Iron oxides; Lakes; Nanocrystalline materials; Runoff; Sedimentary rocks; Sedimentology; Sediments; Serpentine; Drainage patterns; Environmental conditions; Lacustrine systems; Redox sensitives; Sedimentary environment; Sedimentary systems; Visible/near infrared; Water rock interactions; diagenesis; iron oxide; lacustrine deposit; mineralogy; sediment chemistry; sediment core; sedimentation; Core drilling

Highly siderophile element and Os isotope results from the structurally atypical Batin dunite in the Wadi Tayin massif of the Oman ophiolite - Klaessens, Delphine; Reisberg, Laurie; Jousselin, David; Team, Oman Drilling Project Science (Journal of Geophysical Research: Solid Earth, 2021)
Dunites in ophiolites form by pyroxene dissolution and olivine precipitation during melt-peridotite interaction. We present structural and geochemical data on peridotites from the Batin region (Wadi Tayin massif) of the Oman ophiolite, where an exceptionally large (∼9.5 km long) dunite body was sampled by the ICDP Oman Drilling Project (BA4A borehole). 900 –1,200 m beneath the petrological Moho, this dunite is overlain by harzburgite hosting pyroxene-depleted and pyroxene-rich bands. Highly siderophile elements (HSEs) and Os isotopes, excellent tracers of melt flow through peridotites, were measured in dunites and interspersed harzburgites from BA4A borehole. The Batin dunite is structurally and chemically distinct from dunites from the Moho Transition Zone and basal section of the ophiolite, resembling instead sparse dunite veins in the main mantle section. Batin dunites have fairly uniform Os, Ir, and Ru abundances, but Pd and Pt contents increasing with depth. One deep dunite sample has initial 187Os/188Os more radiogenic than MORB. Though the limited number of data demands prudence, we suggest that the Batin dunite formed from a large pulse of radiogenic melts, whose flow was impeded ∼1,200 m below the Moho. As these melts ascended, they may have lost their radiogenic character and relative Pt and Pd enrichment through interaction with peridotites, which have much higher HSE contents than melts. Such interaction would also diminish the under-saturation in pyroxene of the melts, eliminating their capacity to sufficiently dissolve the pyroxene of the host harzburgite to form dunite, thus explaining the upper limit of the dunite at ∼900 m. © 2021. American Geophysical Union. All Rights Reserved.
cited By 0
Keywords: dunite; mantle structure; ophiolite; osmium isotope; siderophile element

Labyrinth patterns in Magadi (Kenya) cherts: Evidence for early formation from siliceous gels - Leet, Kennie; Lowenstein, Tim K.; Renaut, Robin W.; Owen, R. Bernhart; Cohen, Andrew (Geology, 2021)
Sedimentary cherts, with well-preserved microfossils, are known from the Archean to the present, yet their origins remain poorly understood. Lake Magadi, Kenya, has been used as a modern analog system for understanding the origins of nonbiogenic chert. We present evidence for synsedimentary formation of Magadi cherts directly from siliceous gels. Petrographic thin-section analysis and field-emission scanning electron microscopy of cherts from cores drilled in Lake Magadi during the Hominin Sites and Paleolakes Drilling Project in 2014 led to the discovery of two-dimensional branching “labyrinth patterns” in chert, which are a type of fractal “squeeze” pattern formed at air-liquid interfaces. Labyrinth patterns preserved in chert from Lake Magadi cores indicate invasion of air along planes in dewatering gels. These patterns support the precipitation of silica gels in the saline-alkaline Lake Magadi system and syndepositional drying of gels in contact with air as part of chert formation. Recognizing cherts as syndepositional has been critical for our use of them for U-Th dating. Identification of labyrinth patterns in ancient cherts can provide a better understanding of paleoenvironmental and geochemical conditions in the past © 2021 Geological Society of America. For permission to copy, contact editing@geosociety.org.
Keywords: Kajiado; Kenya; Lake Magadi; Binary alloys; Field emission microscopes; Infill drilling; Lakes; Phase interfaces; Scanning electron microscopy; Silica; Silica gel; Thorium alloys; Thorium metallography; Uranium alloys; Uranium metallography; Air liquid interfaces; Analog systems; Drilling projects; Field emission scanning electron microscopy; Geochemical conditions; Microfossils; Synsedimentary; Thin section; Archean; chert; depositional environment; microfossil; paleolimnology; petrography; precipitation (chemistry); silica; Gels

Lake Ohrid’s tephrochronological dataset reveals 1.36 Ma of Mediterranean explosive volcanic activity - Leicher, Niklas; Giaccio, Biagio; Zanchetta, Giovanni; Sulpizio, Roberto; Albert, Paul G.; Tomlinson, Emma L.; Lagos, Markus; Francke, Alexander; Wagner, Bernd (Scientific Data, 2021)

Land-sea correlations in the Eastern Mediterranean region over the past c. 800 kyr based on macro- and cryptotephras from ODP Site 964 (Ionian Basin) - Vakhrameeva, Polina; Koutsodendris, Andreas; Wulf, Sabine; Portnyagin, Maxim; Appelt, Oona; Ludwig, Thomas; Trieloff, Mario; Pross, J{org (Quaternary Science Reviews, 2021)
Direct correlations between terrestrial and marine climate-proxy records are essential in order to determine potential lead/lag relationships in the response of the terrestrial and marine realms to climate forcing. In the Eastern Mediterranean region, such land-sea correlations have not yet been established beyond c. 200 ka. To explore the potential of tephra layers for Late and Middle Pleistocene land-sea correlations in the Eastern Mediterranean region, we have revisited yet unconfirmed tephra layers previously reported from Ocean Drilling Program (ODP) Site 964 (Ionian Basin) for the past c. 800 kyr in order to identify their origin and examine potential terrestrial counterparts. Using major- and trace-element glass analyses, we confirmed the presence of seven visible tephra layers with ages from 623 to 38 ka. These tephra layers represent known tephra isochrons from Italian volcanic centers (Y-5, Y-7, X-6, and V-0) and three yet unknown eruptions from Etna (623 ka), the Campanian Volcanic Zone (CVZ; 238 ka), and Pantelleria (238 ka). Because the majority of the previously reported tephra layers from ODP Site 964 were identified as clastic layers of non-volcanic origin, cryptotephra analyses were carried out for cores spanning Marine Isotope Stages (MIS) 13 to 9 (500 –320 ka). This effort yielded 19 cryptotephra layers originating from Santorini volcano, the CVZ, possibly Roccamonfina volcano, and an undefined source in either the Aeolian Islands or the South Aegean Volcanic Arc. Two tephra layers are correlated with potential equivalents from terrestrial archives on the Italian and Balkan Peninsulas, including tephra isochrons SC5/A7/OH-DP-1966 (c. 493 ka; Mercure basin, Acerno basin, and Lake Ohrid) and TP09 –65.95 (c. 359 ka; Tenaghi Philippon) that represent an unknown eruption of Roccamonfina and the Cape Therma 1 eruption of Santorini, respectively. Direct linking of the marine record from ODP Site 964 with the terrestrial records from Tenaghi Philippon, Lake Ohrid, and the Acerno basin via tephra tie points allowed us to circumvent shortcomings of the individual age models, and to obtain a comprehensive picture of climate variability in the greater Eastern Mediterranean region for the MIS 13 –9 interval. © 2021 Elsevier Ltd
Keywords: Balkans; Catania [Sicily]; Central Macedonia; Cyclades; Etna; Greece; Italy; Lake Ohrid; Lipari Islands; Messina [Sicily]; Pantelleria; Santorin; Santorini [Southern Aegean]; Serrai [Central Macedonia]; Sicily; Southern Aegean; Tenaghi Philippon; Trapani; Lakes; Trace elements; Volcanoes; Climate variability; Eastern Mediterranean; Land-sea correlations; Major and trace elements; Marine isotope stages; Middle Pleistocene; Ocean drilling programs; South Aegean volcanic arc; Campanian; marine record; Mediterranean environment; Ocean Drilling Program; proxy climate record; tephra; tephrochronology; volcanic eruption; volcanic glass; volcanic island; Climate models

Late Pliocene to early Pleistocene climate dynamics in western North America based on a new pollen record from paleo-Lake Idaho - Allst{adt, F.J.; Koutsodendris, A.; Appel, E.; R{osler, W.; Reichgelt, T.; Kaboth-Bahr, S.; Prokopenko, A.A.; Pross, J. (Palaeobiodiversity and Palaeoenvironments, 2021)
Marked by the expansion of ice sheets in the high latitudes, the intensification of Northern Hemisphere glaciation across the Plio/Pleistocene transition at 2.7 Ma represents a critical interval of late Neogene climate evolution. To date, the characteristics of climate change in North America during that time and its imprint on vegetation has remained poorly constrained because of the lack of continuous, highly resolved terrestrial records. We here assess the vegetation dynamics in northwestern North America during the late Pliocene and early Pleistocene (c. 2.8 –2.4 Ma) based on a pollen record from a lacustrine sequence from paleo-Lake Idaho, western Snake River Plain (USA) that has been retrieved within the framework of an International Continental Drilling Program (ICDP) coring campaign. Our data indicate a sensitive response of forest ecosystems to glacial/interglacial variability paced by orbital obliquity across the study interval, and also highlight a distinct expansion of steppic elements that likely occurs during the first strong glacial of the Pleistocene, i.e. Marine Isotope Stage 100. The pollen data document a major forest biome change at 2.6 Ma that is marked by the replacement of conifer-dominated forests by open mixed forests. Quantitative pollen-based climate estimates suggest that this forest reorganisation was associated with an increase in precipitation from the late Pliocene to the early Pleistocene. We attribute this shift to an enhanced moisture transport from the subarctic Pacific Ocean to North America, confirming the hypothesis that ocean-circulation changes were instrumental in the intensification of Northern Hemisphere glaciation. © 2021, The Author(s).
cited By 4
Keywords: climate effect; climate variation; drilling; glaciation; ice sheet; Neogene; palynology; Pliocene-Pleistocene boundary; proxy climate record; vegetation dynamics; Idaho; North America; Pacific Ocean; Snake River Plain; United States; Coniferophyta

Lithospheric extension in response to subduction of the Paleo-Pacific Plate: Insights from Early Jurassic intraplate volcanic rocks in the Sk2 Borehole, Songliao Basin, NE China - Huang, Feng; Zhang, Zhao; Xu, Jifeng; Li, Xiyao; Zeng, Yunchuan; Xu, Rong; Liu, Xijun; Zhang, Liying; Zhang, Man; Yang, Changqi; Zhang, Liangliang; Yu, Hongxia; et al. (Lithos, 2021)
Subduction of the Paleo-Pacific and Mongol –Okhotsk oceanic plates is widely believed to have caused extensive Mesozoic magmatism and lithospheric deformation in East Asia. However, it remains unclear how the two tectonic domains affected NE China, and whether a boundary exists between them, because the Songnen Block in central NE China is covered by sedimentary rocks and the related mafic magmatism has been rarely discovered. Here we report a suite of Early Jurassic (ca. 175 Ma) mafic volcanic rocks (including basalt and basaltic andesite) from the Sk2 Borehole, Songliao Basin, NE China. The Sk2 mafic rocks are characterized by high Th/U, Zr/Y and Ti/Y ratios, and their geochemical signatures are consistent with formation in a back-arc extensional setting, rather than an arc setting. The rocks show depleted zircon εHf(t) and whole-rock εNd(t) values, which are comparable to mafic rocks located on the east of the Songliao Basin. This suggests that they both have a depleted mantle source, unlike the mafic rocks on the west of the Songliao Basin with relatively enriched Nd and Hf isotopes. Early –Middle Jurassic mafic rocks are distributed in the Erguna Block, >500 km to the west from the Sk2 Borehole, whereas coeval mafic rocks are widely distributed in the nearby eastern Heilongjiang and Jilin provinces. These intraplate-like mafic rocks and the Early Jurassic bimodal rocks within the Lesser Xing'an and Zhangguangcai ranges likely formed in response to lithospheric extension that was triggered by subduction of the Paleo-Pacific Plate. The Early Jurassic mafic rocks directly underlie the oldest sedimentary rocks (the Huoshiling Formation) in the Songliao Basin, which suggests that basin formation was probably initiated by lithospheric extension. © 2020 Elsevier B.V.
Keywords: borehole; deformation mechanism; extensional tectonics; intraplate process; Jurassic; lithospheric structure; Pacific plate; paleogeography; plate tectonics; subduction zone; tectonic evolution; tectonic setting; volcanic rock; China; Mongol-Okhotsk Fold Belt; Songliao Basin

Development trend of continental scientific drilling technology (in Chinese with English abstract);[大陆科学钻探工程技术发展动态及趋势分析] - Xue, Q.; Liang, N.; Han, L.; Ma, S.; Wang, K. (Drilling Engineering, 2021)

Hydration Imaging Spectroscopy Dataset for Oman Drilling Project Holes GT1A, GT2A, and GT3A - Crotteau, Molly A; Greenberger, Rebecca N; Ehlmann, Bethany L; Rossman, George R; Harris, Michelle; Kelemen, Peter B; Teagle, Damon AH; et al. (CaltechDATA, 2021)

Imaging the Chicxulub Central Crater Zone from Large-Scale Seismic Acoustic Wave Propagation and Gravity Modeling - Ortiz-Aleman, C.; Martin, R.; Urrutia-Fucugauchi, J.; Castillo, M.O.; Nava-Flores, M. (Pure and Applied Geophysics, 2021)
Large impact structures are characterized by peak ring and central uplifts with lateral/vertical mass transport during late formation stages. Here we investigate the Chicxulub crater, which has been surveyed by an array of marine, aerial and land-borne geophysical methods. Seismic reflection surveys in its central sector have shown lack of resolution, making it difficult to image the central uplift. We develop an integrated seismic and gravity model for the structural elements, imaging the central uplift and melt and breccia units. The 3D velocity model built from interpolation of seismic data is validated using perfectly matched layer seismic acoustic wave propagation modeling, optimized at grazing incidence using the shift in the frequency domain. Modeling shows that lack of illumination relates to seismic energy that remains trapped in an upper low-velocity zone corresponding to the carbonate sediments, upper melt/breccias and surrounding faulted blocks. After conversion of seismic velocities into a volume of density values, we apply parallel forward gravity modeling to constrain the size and shape of the central uplift, which has a 40 km diameter concave upwards top lying at 3.5 –4.5 km depth. The preferred model provides a high-resolution image of crater units and structure. The gravity response of modeled units shows asymmetries in structure and the distribution of breccias, melt and target carbonates. Finally, we apply an adjoint reverse time migration approach for seismic imaging using the density and velocity models built for the acoustic wave propagation and gravity modeling, which allows improved modeling of the crater structure. © 2021, Springer Nature Switzerland AG.
cited By 2

High-resolution seismic reflection survey crossing the Insubric Line into the Ivrea-Verbano Zone: Novel approaches for interpreting the seismic response of steeply dipping structures - Liu, Yu; Greenwood, Andrew; Het'enyi, Gy{orgy; Baron, Ludovic; Holliger, Klaus (Tectonophysics, 2021)
A high-resolution seismic reflection survey has been conducted across the Insubric Line from the Sesia Zone into the Ivrea-Verbano Zone (IVZ), where a remarkably complete cross-section of lower continental crust is exposed. The survey was carried out in preparation for the DIVE (Drilling the Ivrea-Verbano zonE) project, which was recently approved by the International Continental Scientific Drilling Program (ICDP). DIVE aims to gain new insights into the characteristics of the lower continental crust through targeted drilling, sampling, and borehole logging. A key borehole is planned near the Insubric Line at Balmuccia, where the deepest parts of the lower continental crust are exposed. As such, the primary objective of this seismic survey was to explore whether the sub-vertical structures prevailing at the surface can be expected to continue at depth or whether there are any indications for major flattening or fault-related offsets. Correspondingly, the acquisition and processing of the seismic reflection data were geared towards revealing weak backscattered events from local heterogeneities associated with the prevailing sub-vertical structural grain. The migrated sections, contain coherent backscattered events to a depth of 1 km, which form numerous short lineaments that seem to align sub-vertically. To substantiate this observation, we have generated synthetic seismic reflection surveys for canonical models of sub-vertical structures associated with Gaussian- and binary-distributed heterogeneities. Both the observed and synthetic seismic data were then subjected to energy-based attribute analysis as well as geostatistical estimations of the structural aspect ratios and the associated dips. The results of these quantitative interpretation approaches are indicative of the overall consistency between the synthetic and the observed seismic data and, hence, support the original qualitative interpretation of the latter in that the sub-vertical structural grain evident at the surface seems to prevail throughout the imaged part of the upper crust. © 2021 The Authors
Keywords: Italy; Ivrea-Verbano Zone; Aspect ratio; Boreholes; Geological surveys; Infill drilling; Seismic prospecting; Seismic response; Well logging; Continental scientific drillings; Geostatistical estimation; High resolution seismic; Local heterogeneity; Quantitative interpretation; Seismic reflection data; Seismic reflection survey; Vertical structures; fault zone; geostatistics; hard rock; seismic reflection; seismic response; seismic survey; structural response; Seismic waves

Estimating Stress from Three-Dimensional Borehole Displacements Induced by Fluid Injection in Different Types of Fractured or Faulted Rocks - Guglielmi, Y.; Cook, P.; Soom, F.; Dobson, P.; Kneafsey, T.; Valley, B.; Kakurina, M.; Niemi, A.; Tsang, C.F.; Tatomir, A.; Juhlin, C.; Basirat, F. (55th U.S. Rock Mechanics / Geomechanics Symposium 2021, 2021)

Globally distributed iridium layer preserved within the Chicxulub impact structure - Goderis, S.; Sato, H.; Ferrière, L.; Schmitz, B.; Burney, D.; Kaskes, P.; Vellekoop, J.; Wittmann, A.; Schulz, T.; Chernonozhkin, S.M.; Claeys, P.; Graaff, S.J.; et al. (Science Advances, 2021)
The Cretaceous-Paleogene (K-Pg) mass extinction is marked globally by elevated concentrations of iridium, emplaced by a hypervelocity impact event 66 million years ago. Here, we report new data from four independent laboratories that reveal a positive iridium anomaly within the peak-ring sequence of the Chicxulub impact structure, in drill core recovered by IODP-ICDP Expedition 364. The highest concentration of ultrafine meteoritic matter occurs in the post-impact sediments that cover the crater peak ring, just below the lowermost Danian pelagic limestone. Within years to decades after the impact event, this part of the Chicxulub impact basin returned to a relatively low-energy depositional environment, recording in unprecedented detail the recovery of life during the succeeding millennia. The iridium layer provides a key temporal horizon precisely linking Chicxulub to K-Pg boundary sections worldwide. Copyright © 2021 The Authors, some rights reserved.
cited By 24

Directional drilling technology takes lead with focus on deep earth anddeep sea exploration–Review of science and technology innovation by Institute of Exploration Techniques，CAGS during the 13th Five‑Year Plan and an outlook to the 14th Five‑Year Plan (in Chinese with English abstract);[定向钻井技术引领 聚焦深地深海探测––勘探技术所“十三五”科技创新回顾及“十四五”业务展望] - Ran, H.; Liang, J.; Liang, N.; Xue, Q.; Ma, S. (Drilling Engineering, 2021)

Drivers of phytoplankton community structure change with ecosystem ontogeny during the Quaternary - Cvetkoska, Aleksandra; Jovanovska, Elena; Hauffe, Torsten; Donders, Timme H.; Levkov, Zlatko; Waal, Dedmer B.; Reed, Jane M.; Francke, Alexander; Vogel, Hendrik; Wilke, Thomas; Wagner, Bernd; Wagner-Cremer, Friederike (Quaternary Science Reviews, 2021)

Effects of alteration and cracks on the seismic velocity structure of oceanic lithosphere inferred from ultrasonic measurements of mafic and ultramafic samples collected by the Oman Drilling Project - Hatakeyama, Kohei; Katayama, Ikuo; Abe, Natsue; Okazaki, Keishi; Michibayashi, Katsuyoshi; Party, Oman Drilling Project Science (Journal of Geophysical Research: Solid Earth, 2021)

Enhancing gas production from Class II hydrate deposits through depressurization combined with low-frequency electric heating under dual horizontal wells - Zhao, E.; Hou, J.; Ji, Y.; Liu, Y.; Bai, Y. (Energy, 2021)
Class II hydrate deposits are characterized by a mobile water zone (WZ) underneath the hydrate-bearing layer (HBL) and are encountered in permafrost and deep-sea sediments. In this work, an efficient method of depressurization combining low-frequency electric heating under dual horizontal wells is proposed to exploit Class II hydrate deposits, in which two parallel horizontal wells are arranged in the HBL and the WZ. Based on the geological parameters in the Mallik deposit, the energy recovery behaviors are studied through a numerical simulation approach. Electric heating significantly improves hydrate dissociation and gas production compared with the depressurization method. However, gas production lags electric heating for a long time, and the energy efficiency ratio decreases with time in the later stage. To address these shortcomings, two additional electric heating schemes are designed and optimized. The results show that the additional wellbore heating at the beginning of production accelerates the dissociation of hydrates near the production well, thus greatly reducing the lag time. When electric heating is terminated after the 800th day, the cumulative gas production is reduced by 9.1%, but the energy efficiency ratio is improved as high as 48.71, which confirms the great potential of the proposed method. © 2021 Elsevier Ltd
cited By 11
Keywords: Dissociation; Electric heating; Energy efficiency; Gas hydrates; Horizontal wells; Hydration; Class II; Depressurizations; Electrical heating; Energy; Energy recovery; Gas productions; Hydrate deposit; Lower frequencies; Thermal stimulation; Water zone; Deposits; energy efficiency; gas hydrate; gas production; numerical model; optimization; permafrost; simulation

Erratum to “Chronostratigraphy of the Baringo-Tugen-Barsemoi (HSPDP-BTB13-1A) core – 40Ar/39Ar dating, magnetostratigraphy, tephrostratigraphy, sequence stratigraphy and Bayesian age modeling” [PALAEO, Volume 532(2019), 109258] (Palaeogeography, Palaeoclimatology, Palaeoecology (2019) 532, (S0031018218310496), (10.1016/j.palaeo.2019.109258)) - Deino, Alan L. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2021)
The Publisher regrets that this article is an accidental duplication of an article that has already been published in, https://doi.org/10.1016/j.palaeo.2019.109519. The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal. © 2019 Elsevier B.V.

Environmental changes during MIS6-3 in the Basin of Mexico: A record of fire, lake productivity history and vegetation - Mart'inez-Abarca, L.R.; Lozano-Garc'ia, S.; Ortega-Guerrero, B.; Ch'avez-Lara, C.M.; Torres-Rodr'iguez, E.; Caballero, M.; Brown, E.T.; Sosa-N'ajera, S.; Acosta-Noriega, C.; Sandoval-Ibarra, V. (Journal of South American Earth Sciences, 2021)
The responses of lake productivity, vegetation, and fire events in the Basin of Mexico to orbital changes from late MIS 6 to MIS 3 (146 –35 ka) have been studied based on geochemical (Ti, TIC, TOC, C/N), charcoal (CHAR) and pollen data of the sediment core CHA08 from Lake Chalco. The paleoenvironmental reconstruction identifies the MIS 6 as a wetter period with episodes of dry conditions, low forest cover and low fire activity. A sudden change from wetter to dry environments with low to high forest cover and fire activity episodes characterized the end of the MIS 6 (132 –130 ka) coincident with high spring insolation. Variations in vegetation composition, with a tendency towards higher forest cover, fire-activity, runoff, and organic matter availability, are recorded during the MIS 5, MIS 4, and MIS 3. However, a reduction in the fire-activity was recorded for the cold and dry MIS 4. Spectral analysis based on the titanium concentration record of Lake Chalco suggests a precessional forcing on runoff variations. We explored the impact of the Intertropical Convergence Zone latitudinal migrations which have been related to the summer insolation at 65° N by comparing runoff data with other sedimentary records from North and Central America. Our results highlight the sensitivity of the high altitude tropical basin to climate variations. © 2021 Elsevier Ltd
cited By 11
Keywords: environmental change; fire history; glacial-interglacial cycle; paleoenvironment; palynology; reconstruction; vegetation dynamics; Lake Chalco; Mexico [North America]

Exotic rock block from the Koshava gypsum mine, Northwest Bulgaria: Petrography, geochemistry, mineralogy and melting phenomena - Yanev, Y.; Benderev, A.; Zotov, N.; Dubinina, E.; Iliev, I.; Georgiev, S.; Ilieva, I.; Sergeeva, I. (Geologica Balcanica, 2021)
The described exotic rock block (60×80×13-15 cm) was found at 290 m depth in a lower.middle Badenian gypsum layer in the Koshava mine, NW Bulgaria, near the Danube River. It is greyish-black, granular, with layered structure and layers composed of α-quartz rosettes covered with organic matter (kerogen-like type with high contents of Ge, Mo and B), wood relicts with chalcedony replacement, and porous lenses with compact accumulation of organic matter. The block is coated with quartz crust, up to 2 cm thick, with regmaglypt-like forms, also replaced by quartz. Aside from the surface, melting phenomena were also observed inside the quartz rosettes and especially in the wood relicts and porous lenses. The melted drops are actually crystallized chalcedony. The organic matter accumulations contain Si-organic zoned micrometre-sized spherules. Fe silicides were found in the organic matter of all parts of the block, in which hapkeite was determined by X-ray analysis. Other detected minerals include graphite, cristobalite, coesite, skeletal and framboidal pyrite, moassanite, magnetite, suessite, sphalerite and minerals formed in the gypsum lagoon (gypsum, celestine, barite, calcite, halite and clays). The geological position of the block in the gypsum without any other sediments, the extensive melting phenomena with melted spherules, crushed quartz, its enrichment in 18O isotope and the presence of coesite suggest that it is shock ejecta, in certain aspects resembling the large Muong Nong-type tektites, but its characteristics could be the basis for distinguishing it as a new tektite type. The fact that it was found in a gypsum layer of early.middle Badenian age points to its probable association with the Ries-Steinheim impact event, despite the long distance between them ( 1100 km). © 2021 Geological Institute â€Strashimir Dimitrovâ€, Bulgarian Academy of Sciences.
cited By 1

Diatom paleolimnology of late Pliocene Baringo Basin (Kenya) paleolakes - Westover, Karlyn S.; Stone, Jeffery R.; Yost, Chad L.; Scott, Jennifer J.; Cohen, Andrew S.; Rabideaux, Nathan M.; Stockhecke, Mona; Kingston, John D. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2021)
Kenya's Baringo-Tugen Hills-Barsemoi drill site is one of six localities across Kenya and Ethiopia from which the Hominin Sites and Paleolakes Drilling Project has obtained sediment cores in an effort to investigate the role of environmental forcing in shaping human evolution. The Baringo Basin site features extensive exposures of the Chemeron Formation, which contains >100 fossil vertebrate localities including five hominin sites. The 228-m drill core, dating from 3.29 to 2.56 Ma, is characterized by fluvio-lacustrine sediments, including multiple diatomites, with evidence of variable degrees of later pedogenic modification. In the lower part of the core ( 3.29 –3.04 Ma), diatoms were preserved only in very low abundance, consistent with predominantly fluvial or lake marginal environments. In contrast, five diatomites and two additional diatom-rich intervals were deposited after 3.04 Ma, reflecting a major shift in the basin hydrology. Planktonic freshwater species dominated these diatom-rich intervals, whereas periphytic taxa were present in proportions less than 2%, suggesting that these intervals represent open-water deposition during lake highstands. Littoral or saline assemblages are largely absent throughout the core. Instead, we observed a pattern of increasing diatom frustule dissolution at the tops and bottoms of diatomite units, indicating increased alkalinity during the transgressive/regressive phases. A Na-bearing zeolite (analcime) indicative of saline waters precipitated in clastic-dominated intervals between diatomites, suggesting extreme environmental variability between lake highstands and lowstands. Diatom assemblages were consistently dominated by a few species belonging to the genera Aulacoseira and Stephanodiscus, which were at times co-dominant. We infer that assemblages dominated by Aulacoseira represent a well-mixed lake with abundant supply of silica. When Stephanodiscus was dominant, which occurred more frequently in the later freshwater phases, we infer incomplete mixing and reduced silica flux to the epilimnion (upper water layer). © 2019 Elsevier B.V.
Keywords: Baringo; Ethiopia; Kenya; Tugen Hills; Aulacoseira; Bacillariophyta; Stephanodiscus; Vertebrata; alkalinity; diatom; diatomite; fluvial deposit; fossil assemblage; lacustrine deposit; paleolimnology; Pliocene; sediment core

Exploring the Past Biosphere of Chew Bahir/Southern Ethiopia: Cross-Species Hybridization Capture of Ancient Sedimentary DNA from a Deep Drill Core - Krueger, Johanna; Foerster, Verena; Trauth, Martin H.; Hofreiter, Michael; Tiedemann, Ralph (Frontiers in Earth Science, 2021)
Eastern Africa has been a prime target for scientific drilling because it is rich in key paleoanthropological sites as well as in paleolakes, containing valuable paleoclimatic information on evolutionary time scales. The Hominin Sites and Paleolakes Drilling Project (HSPDP) explores these paleolakes with the aim of reconstructing environmental conditions around critical episodes of hominin evolution. Identification of biological taxa based on their sedimentary ancient DNA (sedaDNA) traces can contribute to understand past ecological and climatological conditions of the living environment of our ancestors. However, sedaDNA recovery from tropical environments is challenging because high temperatures, UV irradiation, and desiccation result in highly degraded DNA. Consequently, most of the DNA fragments in tropical sediments are too short for PCR amplification. We analyzed sedaDNA in the upper 70 m of the composite sediment core of the HSPDP drill site at Chew Bahir for eukaryotic remnants. We first tested shotgun high throughput sequencing which leads to metagenomes dominated by bacterial DNA of the deep biosphere, while only a small fraction was derived from eukaryotic, and thus probably ancient, DNA. Subsequently, we performed cross-species hybridization capture of sedaDNA to enrich ancient DNA (aDNA) from eukaryotic remnants for paleoenvironmental analysis, using established barcoding genes (cox1 and rbcL for animals and plants, respectively) from 199 species that may have had relatives in the past biosphere at Chew Bahir. Metagenomes yielded after hybridization capture are richer in reads with similarity to cox1 and rbcL in comparison to metagenomes without prior hybridization capture. Taxonomic assignments of the reads from these hybridization capture metagenomes also yielded larger fractions of the eukaryotic domain. For reads assigned to cox1, inferred wet periods were associated with high inferred relative abundances of putative limnic organisms (gastropods, green algae), while inferred dry periods showed increased relative abundances for insects. These findings indicate that cross-species hybridization capture can be an effective approach to enhance the information content of sedaDNA in order to explore biosphere changes associated with past environmental conditions, enabling such analyses even under tropical conditions. © Copyright © 2021 Krueger, Foerster, Trauth, Hofreiter and Tiedemann.
Keywords: Ethiopia; Bacteria (microorganisms); Chlorophyta; Eukaryota; Gastropoda; Hexapoda; archaeological evidence; biosphere; core analysis; DNA; hominid; human settlement; hybridization; irradiation; paleoclimate; paleoecology; paleoenvironment; paleolimnology; reconstruction; timescale; tropical environment; ultraviolet radiation

Fine-grained gravity flow deposits and their depositional processes: A case study from the Cretaceous Nenjiang Formation, Songliao Basin, NE China - Tian, X.; Gao, Y.; Li, Z.; Carlos, Z.; Chen, Z.; Huang, Y.; Yu, E.; Wang, C. (Geological Journal, 2021)
The Songliao Basin in NE China is a large rift basin filled with Cretaceous terrestrial sediments. Lacustrine mudstones of the Nenjiang Formation form an important source rock in the Cretaceous Songliao Basin. These shales are commonly thought to have been deposited in deep, quiet, and anoxic environments. Samples obtained from the core of the SK-2 scientific borehole provide critical insights to understand the hydrodynamic and hydroclimatic environments, which are, however, different from the traditional views regarding the deposition of these rocks. By following a mudstone description guide, five different mudstone lithofacies (LF) transported and deposited by muddy hyperpycnal flows and muddy debris flows were recognized. They are laminated fine mudstone (LF1), laminated medium mudstone (LF2), and laminated coarse mudstone (LF3) showing pairs of inverse grading (Ha) and normal grading (Hb) under the microscope, graded coarse mudstone (LF4) and massive coarse mudstone (LF5). We found that mudstones of the First Member of the Nenjiang Formation are dominated by siliciclastic detritus and argillaceous components and show frequent variations in grain size. Because large-scale sub-lacustrine channels travelling long distance (>80 km) were widely distributed in the Songliao palaeolake during the deposition of the Nenjiang Formation, fluctuations in mudstone grain size might have been caused by velocity fluctuations in flows. Sedimentary structures and textures preserved in mudstones of the First Member of the Nenjiang Formation indicate that the majority of these lithofacies were accumulated by muddy hyperpycnal flows and muddy debris flows. Therefore, a depositional model dominantly influenced by muddy hyperpycnal flows and debris flows is proposed. This work not only provides a new view for the depositional process of mudstones of the Songliao Basin, NE China, but also give insights to understand lacustrine palaeoenvironment and terrestrial palaeoclimate. © 2020 John Wiley & Sons Ltd
cited By 2
Keywords: borehole; Cretaceous; debris flow; gravity flow; hydrocarbon reservoir; lacustrine deposit; lithofacies; mudstone; reservoir characterization; shale; source rock; China; Songliao Basin

Geochemical Profiles Across the Listvenite-Metamorphic Transition in the Basal Megathrust of the Semail Ophiolite: Results From Drilling at OmanDP Hole BT1B - Godard, Marguerite; Carter, EJ; Decrausaz, T; Lafay, R; Bennett, E; Kourim, F; Obeso, J-C; Michibayashi, K; Harris, M; Coggon, JA; et al. (Journal of Geophysical Research: Solid Earth, 2021)
The transition from the Semail ophiolite mantle to the underlying metamorphic sole was drilled at ICDP OmanDP Hole BT1B. We analyzed the bulk major, volatile and trace element compositions of the mantle-derived listvenite series and metamorphic rocks, with the aim to constrain chemical transfers associated with peridotite carbonation along the ophiolite basal thrust. The listvenite series comprise variously carbonated serpentinites and (fuchsite-bearing) listvenites. They have high CO2 (up to 43 wt.%) and variable H2O (0 –12 wt.%). Yet, they have compositions close to that of the basal banded peridotites for most major and lithophile trace elements, with fuchsite-bearing listvenites overlapping in composition with amphibole-bearing basal lherzolites (e.g., Al2O3 = 0.1 –2.2 wt.%; Yb = 0.05 –1 x CI-chondrite). The protolith of the listvenite series was likely similar in structure and composition to serpentinized banded peridotites which immediately overlie the metamorphic sole elsewhere in Oman. The listvenite series are enriched in fluid mobile elements (FME) compared to Semail peridotites (up to ∼103 –104 x Primitive Mantle), with concentrations similar to the underthrusted metabasalts and/or metasediments for Cs, Sr and Ca and sometimes even higher for Pb, Li, As, and Sb (e.g., Li up to 130 μg/g; As up to 170 μg/g). We also observe a decoupling between Sr-Ca enrichments and other FME, indicating interactions with several batches of deep CO2-rich fluids transported along the basal thrust. These results suggest that peridotite carbonation could represent one of the major trap-and-release mechanisms for carbon, water and FME along convergent margins. © 2021. American Geophysical Union. All Rights Reserved.
cited By 7
Keywords: drilling; metasediment; ophiolite; peridotite; petrogenesis; petrography; serpentinite; serpentinization; Oman

Geochemical, biological, and clumped isotopologue evidence for substantial microbial methane production under carbon limitation in serpentinites of the Samail Ophiolite, Oman - Nothaft, Daniel B; Templeton, Alexis S; Rhim, Jeemin H; Wang, David T; Labidi, Jabrane; Miller, Hannah M; Boyd, Eric S; Matter, Juerg M; Ono, Shuhei; Young, Edward D; et al. (Journal of Geophysical Research: Biogeosciences, 2021)

Geospatial management and analysis of microstructural data from san andreas fault observatory at depth (Safod) core samples - Holmes, E.M.; Gaughan, A.E.; Biddle, D.J.; Stevens, F.R.; Hadizadeh, J. (ISPRS International Journal of Geo-Information, 2021)
Core samples obtained from scientific drilling could provide large volumes of direct mi-crostructural and compositional data, but generating results via the traditional treatment of such data is often time-consuming and inefficient. Unifying microstructural data within a spatially referenced Geographic Information System (GIS) environment provides an opportunity to readily locate, visual-ize, correlate, and apply remote sensing techniques to the data. Using 26 core billet samples from the San Andreas Fault Observatory at Depth (SAFOD), this study developed GIS-based procedures for: 1. Spatially referenced visualization and storage of various microstructural data from core billets; 2. 3D modeling of billets and thin section positions within each billet, which serve as a digital record after irreversible fragmentation of the physical billets; and 3. Vector feature creation and unsuper-vised classification of a multi-generation calcite vein network from cathodluminescence (CL) imagery. Building on existing work which is predominantly limited to the 2D space of single thin sections, our results indicate that a GIS can facilitate spatial treatment of data even at centimeter to nanometer scales, but also revealed challenges involving intensive 3D representations and complex matrix transformations required to create geographically translated forms of the within-billet coordinate systems, which are suggested for consideration in future studies. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
cited By 0

Progress of Deep Geological Survey Project under the China Geological Survey - L{u, Qing-tian; Yan, Jia-yong; Chen, Xuan-hua; Hou, He-Sheng; Wang, Wen-shi; Hu, Yu-le (China Geology, 2020)

Pore characteristics of lacustrine shale oil reservoir in the Cretaceous Qingshankou Formation of the Songliao Basin, NE China - Cao, X.; Gao, Y.; Cui, J.; Han, S.; Kang, L.; Song, S.; Wang, C. (Energies, 2020)
Shale oil is hosted in nanopores of organic-rich shales, so pore characteristics are significant for shale oil accumulation. Here we analyzed pore characteristics of 39 lacustrine shale samples of the Late Cretaceous Qingshankou Formation (K2qn) in the Songliao Basin, which is one of the main shale oil resource basins in China, using field emission-scanning electron microscopy (FE-SEM), and low-pressure nitrogen adsorption. We accomplished fractal analysis, correlation analysis using correlation matrix and multidimensional scaling (MDS), and prediction of fractal dimensions, which is the first time to predict pore fractal dimensions of shales. Interparticle pores are highly developed in K2qn. These shales have mesoporous nature and slit-shaped pores. Compared with the second and third members (K2qn2,3), the first member of the Qingshankou Formation (K2qn1) has a larger average pore diameter, much smaller surface area, fewer micropores, simpler pore structure and surface indicated by smaller fractal dimensions. In terms of pore characteristics, K2qn1 is better than K2qn2,3 as a shale oil reservoir. When compared with marine Bakken Formation shales, lacustrine shales of the Qingshankou Formation have similar complexity of pore structure, but much rougher pore surface. This research can lead to an improved understanding of the pore system of lacustrine shales. © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
cited By 7
Keywords: Enamels; Field emission microscopes; Fractal dimension; Gas adsorption; Petroleum reservoir engineering; Petroleum reservoirs; Pore structure; Scanning electron microscopy; Shale oil; Correlation analysis; Correlation matrix; Field emission scanning electron microscopy; Fractal analysis; Multi-dimensional scaling; Nitrogen adsorption; Organic-rich shales; Pore characteristics; Nanopores

Potential mobilizable Fe from secondary phases of differentially altered subsurface basaltic rock – a sequential extraction study on ICDP site Hawaii - Stranghoener, M.; Dultz, S.; Behrens, H.; Schippers, A. (Applied Geochemistry, 2020)
The potential for the mobilization of Fe from secondary phases within subsurface basaltic rocks of the Hawaii Scientific Drilling Project Phase2 (HSDP2) drill core was investigated to elucidate the possible contribution of volcanic islands to the Fe budget of nearby ocean surface waters. Rock specific parameters governing Fe mobilization, such as Fe redox state, specific surface area (SSA), and connected porosity were determined. A four-step sequential extraction procedure using solutions with increasing strength of the extractants was applied to characterize different states of chemical bonding of Fe in secondary phases of the basaltic rocks, a controlling parameter for its release to oceanic water. The sequential extraction results were then used as a measure for the reactivity of secondary Fe-bearing phases and the mobilizable Fe from these rocks. Basaltic rocks with different degrees of weathering showed elevated Fe(III) contents up to 58% total Fe as Fe(III), compared to 11 –18% in fresh basalts. SSAs increased with depth, with maximum values of 70 m2/g observed for hyaloclastites. Both parameters depended mainly on the alteration state of the basalt, which was more strongly affected by the fluid chemistry (freshwater ↔ seawater) than by the age of the rocks. The sequential extractions revealed the presence of highly reactive secondary Fe-bearing phases in submarine rocks exposed to seawater whereas observations for rocks altered in freshwater point to better crystallized phases with lower mobilizable Fe contents. In seawater, aging of secondary Fe-bearing phases was most probably suppressed by the adsorption of silica and multivalent anions. Comparing different types of rock, hyaloclastites and pillow basalts showed the highest mobilizable Fe with up to 19% and 16%, respectively, of the total Fe of the bulk rock. The potential for high amounts of mobilizable Fe from basaltic rocks altered under seawater dominated conditions suggests that the submarine part of volcanic ocean islands represent an underestimated source of Fe supply to ocean surface waters. © 2020 Elsevier Ltd
cited By 1
Keywords: Basalt; Budget control; Chemical bonds; Core drilling; Extraction; Infill drilling; Positive ions; Seawater; Silica; Submarines; Surface waters; Volcanoes; Weathering; Chemical bondings; Controlling parameters; Scientific drilling; Secondary phasis; Sequential extraction; Sequential extraction procedure; Specific surface area (SSA); Volcanic ocean island; Iron compounds; adsorption; basalt; chemical bonding; mobilization; seawater; sequential extraction; silica; surface water; volcanic island; Hawaii

Precise maturity assessment over a broad dynamic range using polycyclic and heterocyclic aromatic compounds - Noah, M.; Horsfield, B.; Han, S.; Wang, C. (Organic Geochemistry, 2020)
The construction and reliable application of maturation indices is extremely important in deep Earth exploration, yet predicting levels of maturation on a molecular level, especially at overmature stages, is still a major challenge. Here, we report robust, broad ranging and precise maturity parameters that were developed using a continuous core of thermally overmature lacustrine deposits (Shahezi Fm.) from the deep Songke-2 Well (SK-2), Songliao Basin, China, augmented by shallow cores of lower maturity marine deposits (Posidonia Shale) from the Hils Syncline, Germany. The novel indices presented here are based on the general process of thermally-induced cyclization, aromatization and aliphatic chain cracking of hundreds to thousands of compounds during maturation. The newly developed parameters, with an extremely broad dynamic range extending from catagenesis and into metagenesis (vitrinite reflectances (Ro) range from 0.9% to 2.2%), are based on polycyclic and heterocyclic aromatic compounds measured using Fourier transform-ion cyclotron resonance-mass spectrometry (FT-ICR-MS). The high coefficient of correlations between the new maturity parameters with Ro and Tmax demonstrate their utility for assessing precisely the thermal maturity of overmature shales. © 2020 Elsevier Ltd
cited By 8
Keywords: Aromatic compounds; Deposits; Mass spectrometry; Shale; Coefficient of correlation; Fourier transform ion cyclotron resonance mass spectrometry; Heterocyclic aromatic compounds; Lacustrine deposits; Maturity assessments; Maturity parameters; Thermally induced; Vitrinite reflectance; Aromatization; catagenesis; chemical alteration; cracking (chemistry); maturation; molecular analysis; PAH; precision; thermal maturity; China; Germany; Songliao Basin; Posidonia

Preferred orientation distribution of shock-induced planar microstructures in quartz and feldspar - Pittarello, L.; Ferrière, L.; Feignon, J.-G.; Osinski, G.R.; Koeberl, C. (Meteoritics and Planetary Science, 2020)
Shocked quartz and feldspar grains commonly exhibit planar microstructures, such as planar fractures, planar deformation features, and possibly microtwins, which are considered to have formed by shock metamorphism. Their orientation and frequency are typically reported to be randomly distributed across a sample. The goal of this study is to investigate whether such microstructures are completely random within a given sample, or whether their orientation might also retain information on the direction of the local shock wave propagation. For this work, we selected samples of shatter cones, which were cut normal to the striated surface and the striation direction, from three impact structures (Keurusselk{a, Finland, and Charlevoix and Manicouagan, Canada). These samples show different stages of pre-impact tectonic deformation. Additionally, we investigated several shocked granite samples, selected at different depths along the drill core recovered during the joint IODP-ICDP Chicxulub Expedition 364 (Mexico). In this case, thin sections were cut along two orthogonal directions, one parallel and one normal to the drill core axis. All the results refer to optical microscopy and universal-stage analyses performed on petrographic thin sections. Our results show that such shock-related microstructures do have a preferred orientation, but also that relating their orientation with the possible shock wave propagation is quite challenging and potentially impossible. This is largely due to the lack of dedicated experiments to provide a key to interpret the observed preferred orientation and to the lack of information on postimpact orientation modifications, especially in the case of the drill core samples. © 2020 The Authors. Meteoritics & Planetary Science published by Wiley Periodicals LLC on behalf of The Meteoritical Society (MET)
cited By 7

Probing the hydrothermal system of the chicxulub impact crater - Kring, D.A.; Tikoo, S.M.; Schmieder, M.; Riller, U.; Rebolledo-Vieyra, M.; Simpson, S.L.; Osinski, G.R.; Gattacceca, J.; Wittmann, A.; Verhagen, C.M.; Cockell, C.S.; Coolen, M.J.L.; et al. (Science Advances, 2020)
The 180-km-diameter Chicxulub peak-ring crater and 240-km multiring basin, produced by the impact that terminated the Cretaceous, is the largest remaining intact impact basin on Earth. International Ocean Discovery Program (IODP) and International Continental Scientific Drilling Program (ICDP) Expedition 364 drilled to a depth of 1335 m below the sea floor into the peak ring, providing a unique opportunity to study the thermal and chemical modification of Earth's crust caused by the impact. The recovered core shows the crater hosted a spatially extensive hydrothermal system that chemically and mineralogically modified 1.4 × 105 km3 of Earth's crust, a volume more than nine times that of the Yellowstone Caldera system. Initially, high temperatures of 300° to 400°C and an independent geomagnetic polarity clock indicate the hydrothermal system was long lived, in excess of 106 years. © 2020 American Association for the Advancement of Science. All rights reserved.
cited By 49

Relationships between low-temperature fires, climate and vegetation during three late glacials and interglacials of the last 430 kyr in northeastern Siberia reconstructed from monosaccharide anhydrides in Lake El'gygytgyn sediments - Dietze, E.; Mangelsdorf, K.; Andreev, A.; Karger, C.; Schreuder, L.T.; Hopmans, E.C.; Rach, O.; Sachse, D.; Wennrich, V.; Herzschuh, U. (Climate of the Past, 2020)
Landscapes in high northern latitudes are assumed to be highly sensitive to future global change, but the rates and long-term trajectories of changes are rather uncertain. In the boreal zone, fires are an important factor in climate-vegetation interactions and biogeochemical cycles. Fire regimes are characterized by small, frequent, lowintensity fires within summergreen boreal forests dominated by larch, whereas evergreen boreal forests dominated by spruce and pine burn large areas less frequently but at higher intensities. Here, we explore the potential of the monosaccharide anhydrides (MA) levoglucosan, mannosan and galactosan to serve as proxies of low-intensity biomass burning in glacial-to-interglacial lake sediments from the high northern latitudes. We use sediments from Lake El'gygytgyn (cores PG 1351 and ICDP 5011-1), located in the far northeast of Russia, and study glacial and interglacial samples of the last 430 kyr (marine isotope stages 5e, 6, 7e, 8, 11c and 12) that had different climate and biome configurations. Combined with pollen and non-pollen palynomorph records from the same samples, we assess how far the modern relationships between fire, climate and vegetation persisted during the past, on orbital to centennial timescales. We find that MAs attached to particulates were well-preserved in up to 430 kyr old sediments with higher influxes from low-intensity biomass burning in interglacials compared to glacials. MA influxes significantly increase when summergreen boreal forest spreads closer to the lake, whereas they decrease when tundra-steppe environments and, especially, Sphagnum peatlands spread. This suggests that lowtemperature fires are a typical characteristic of Siberian larch forests also on long timescales. The results also suggest that low-intensity fires would be reduced by vegetation shifts towards very dry environments due to reduced biomass availability, as well as by shifts towards peatlands, which limits fuel dryness. In addition, we observed very low MA ratios, which we interpret as high contributions of galactosan and mannosan from biomass sources other than those currently monitored, such as the moss-lichen mats in the understorey of the summergreen boreal forest. Overall, sedimentary MAs can provide a powerful proxy for fire regime reconstructions and extend our knowledge of long-term natural fire-climate-vegetation feedbacks in the high northern latitudes. © Author(s) 2020.
cited By 10
Keywords: biomass burning; boreal forest; Boreal Kingdom; climate feedback; evergreen forest; fire; global change; interglacial; lacustrine deposit; late glacial; long-term change; low temperature; monosaccharide; paleoclimate; proxy climate record; reconstruction; vegetation history; Chukchi; Elgygytgyn Lake; Russian Federation; Russian Federation; Siberia; Bryophyta; Larix; Picea; Sphagnum

Protracted Shearing at Midcrustal Conditions During Large-Scale Thrusting in the Scandinavian Caledonides - Giuntoli, Francesco; Menegon, Luca; Warren, Clare J.; Darling, James; Anderson, Mark W. (Tectonics, 2020)
During continental collision, large tracts of crust are mobilized along major shear zones. The metamorphic conditions at which these zones operate, the duration of thrusting, and the deformation processes that facilitated hundreds of km of tectonic transport are still unclear. In the Scandinavian Caledonides, the Lower Seve Nappe displays a main mylonitic foliation with thickness of 1 km. This foliation is overprinted by a brittle-to-ductile deformation pattern localized in C- and C′-type shear bands proximal to the tectonic contact with the underlying S{arv Nappe. Thermobarometry of amphibolites and micaschists suggests a first high-pressure stage at 400 –500°C and 1 –1.3 GPa recorded in mineral relics. The main mylonitic foliation developed under epidote amphibolite facies conditions along the retrograde path from 600°C and 1 GPa to 500°C and 0.5 GPa. Age dating of synkinematic titanite grains in the amphibolites indicates that this mylonitic fabric formed at around 417 ± 9 Ma but older ages spanning 460 –430 Ma could represent earlier stages of mylonitization. The shear bands developed at lower metamorphic conditions of 300 –400°C and 0.3 GPa. In the micaschists, the recrystallized grain size of quartz decreases toward the shear bands. Monomineralic quartz layers are eventually dismembered to form polyphase aggregates deforming by dominant grain size sensitive creep accompanied by slip in muscovite and chlorite. Plagioclase zoning truncations suggest that the shear bands originated by fracturing followed by ductile deformation. The results suggest protracted and long-lasting shearing under amphibolite to greenschist facies conditions during the juxtaposition, stacking, and exhumation of the Lower Seve Nappe.
_eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2020TC006267
Keywords: U-Pb dating; Caledonides; electron backscatter diffraction; deformation mechanisms; petrochronology; thrusting; U-Pb dating

Quantification of gas hydrate saturation and morphology based on a generalized effective medium model - Pan, H.; Li, H.; Chen, J.; Riedel, M.; Holland, M.; Zhang, Y.; Cai, S. (Marine and Petroleum Geology, 2020)
Numerous models have been developed for prediction of gas hydrate saturation based on the microstructural relationship between gas hydrates and sediment grains. However, quantification of hydrate saturation and morphology from elastic properties has been hindered by failing to account for complex hydrate distributions. Here, we develop a generalized effective medium model by applying the modified Hashin-Shtrikman bounds to a newly developed cementation theory. This model is validated by experimental data for synthetic methane and tetrahydrofuran hydrates. Good comparison of model predictions with experimental measurements not only reveals its ability to merge the results of contact cementation theory and effective medium theory, but also indicates its feasibility for characterizing complex morphologies. Moreover, the results of inverting acoustic measurements quantitatively confirm that for synthetic samples in “excess-gas” condition gas hydrates mainly occur as a hybrid-cementing morphology with a low percentage of pore-filling morphology, whereas for pressure-core hydrate-bearing sediments in natural environments they exist as matrix-supporting and pore-filling morphologies with a very low percentage of hybrid-cementing morphology. The hydrate saturations estimated from sonic and density logs in several regions including northern Cascadia margin (Integrated Ocean Drilling Program Expedition 311, Hole U1326D and Hole U1327E), Alaska North Slope (Mount Elbert test well) and Mackenzie Delta (Mallik 5L-38), are comparable to the referenced hydrate saturations derived from core data and resistivity, and/or nuclear magnetic resonance log data, confirming validity and applicability of our model. Furthermore, our results indicate that 8% hybrid-cementing, 33% matrix-supporting and 59% pore-filling hydrates may coexist in the fine-grained and clay-rich marine sediments on the northern Cascadia margin, whereas 10% hybrid-cementing, 54% matrix-supporting and 36% pore-filling hydrates may coexist in the coarse-grained and sand-dominated terrestrial sediments of the Alaska North Slope and Mackenzie Delta. © 2019 The Authors
cited By 10
Keywords: Cementing (shafts); Elastic waves; Filling; Gases; Hydration; Matrix algebra; Morphology; Nuclear magnetic logging; Radioactivity logging; Sediments; Software testing; Submarine geology; Effective medium model; Effective medium theories; Elastic wave velocity; Hydrate bearing sediments; Hydrate saturation; Integrated ocean drilling programs; Modified cementation theory; Nuclear magnetic resonance logs; Gas hydrates; cementation; elastic wave; gas hydrate; marine sediment; model validation; quantitative analysis; saturation; wave velocity; Alaska; Alaska Peninsula; Canada; Cascadia Margin; Mackenzie Delta; Northwest Territories; Pacific Ocean; United States

RADIOCARBON RESERVOIR AGES in the HOLOCENE DEAD SEA - Weber, Nurit; Lazar, Boaz; Stern, Ofra; Burr, George; Gavrieli, Ittai; Roberts, Mark; Kurz, Mark D; Yechieli, Yoseph; Stein, Mordechai (Radiocarbon, 2020)

Real-time gas monitoring at the Tekke Hamam geothermal field (Western Anatolia, Turkey): an assessment in relation to local seismicity - S{uer, S.; Wiersberg, T.; G{uleç, N.; Erzinger, J.; Parlaktuna, M. (Natural Hazards, 2020)
This study presents the results of a real-time gas monitoring experiment conducted, via the use of a quadrupole mass spectrometer, in a mofette field within the Tekke Hamam geothermal site in western Anatolia (Turkey), a tectonically active region hosting several east –west trending grabens. The study is aimed to establish a baseline gas profile of the region. Within the framework of the experiment, gas compositions (CO2, N2, O2, H2, H2S, CH4, He, and Ar) and flow rate of a mofette were monitored during two observation periods: November 2007 –January 2008 and April –July 2008. During the course of monitoring, the major gas component was CO2 with concentration changing around 96 volume percent. Other gases, from the most abundant to the least, were N2, CH4, O2, H2S, Ar, H2, and He. The study produced a short-term, baseline gas profile of the region with daily/diurnal variations and temporal gas fluctuations appearing as instant signals. Although the temporal gas fluctuations did not reach the anomaly level (variations staying within the mean ± 2σ), some of the variations in more than one parameter in the gas compositions (exceeding the mean ± 1σ), accompanied by changes in the diurnal gas pulses lasting for long durations, were correlated with the seismic events selected according to the adopted seismic event elimination criteria. The variations were mainly attributed to changing gas mixing ratios in relation to porosity/permeability modifications possibly related to seismicity. Studies involving the continuous monitoring of meteorological parameters are necessary to assign these variations to geogenic events. © 2020, Springer Nature B.V.
cited By 1
Keywords: concentration (composition); environmental monitoring; gas flow; geothermal system; mass spectrometry; mixing ratio; real time; seismic method; seismicity; Anatolia; Turkey

Recognition of Milankovitch cycles in XRF core-scanning records of the Late Cretaceous Nenjiang Formation from the Songliao Basin (northeastern China) and their paleoclimate implications - Yang, H.; Huang, Y.; Ma, C.; Zhang, Z.; Wang, C. (Journal of Asian Earth Sciences, 2020)
Cretaceous terrestrial sedimentary records are crucial for our understanding of geological systems’ responses to past climate change under greenhouse condition. Numerous publications have documented that Milankovitch cycles were a dominant climate driver over multi-millennial timescales. However, most of these orbital signals were derived from marine records obtained during the Cenozoic geological period, whereas knowledge of Milankovitch cycles preserved in lacustrine sediments prior to the Cenozoic is limited due to the lack of a precise chronological framework, poor preservation rate of terrestrial sediments, limited records, and fewer experts in this research area. This paper reports high-resolution X-ray fluorescence (XRF) elemental records of K, Ti, Rb, Sr, Zr, Zr/Rb, Rb/Sr, and K/Ti from Member 1 (k2n1) and Member 2 (k2n2) of the Nenjiang Formation, which were obtained from a near-continuous SK-2 East (SK-2e) borehole drilled in the Songliao Basin (SB) of northeastern (NE) China. Variations of the elemental records reveal a humid-arid-humid-semiarid climatic evolution throughout the deposition of k2n1 and a humid-arid-humid-arid climatic variation throughout the deposition of k2n2. In this context, K2n1 experienced a relatively longer humid period and more pronounced climatic fluctuation than K2n2. A method of average spectral misfit (ASM) was adopted to successfully identify two optimal sedimentation rates of 6.577 and 8.369 cm/ka for K2n1 and K2n2, respectively. Based on these two sedimentation rates, nearly all significant Milankovitch cycles preserved in the Rb/Sr record were recognized. It is suggested that westerly wind was the main climatic driving factor of climate evolution in the SB under the forcing of Milankovitch cycles. The collectively regulation of obliquity and precession increased the seasonal contrasts during humid periods in the Nenjiang Formation and thereby amplified the paleomonsoon effect, thus bringing more moisture towards the SB and lead to enhanced rainfall. © 2019 Elsevier Ltd
cited By 14
Keywords: arid environment; climate variation; Cretaceous; deposition; humid environment; lacustrine deposit; Milankovitch cycle; paleoclimate; X-ray fluorescence; China; Songliao Basin

Reconstructing East African monsoon variability from grain-size distributions: End-member modeling and source attribution of diatom-rich sediments from Lake Chala - Meyer, Inka; Van Daele, Maarten; Tanghe, Niels; De Batist, Marc; Verschuren, Dirk (Quaternary Science Reviews, 2020)
Grain-size analysis and end-member modeling of the clastic fraction of the 25-kyr sediment sequence from Lake Chala, a meromictic crater lake on the lower east slope of Mt. Kilimanjaro, reveal crucial aspects of climate-driven environmental change in equatorial East Africa since the Last Glacial Maximum. The finely laminated sediments of Lake Chala contain only up to 40% of clastic components, the rest are mainly diatom frustules and amorphous organic matter. Measured grain-size distributions were split into six statistically meaningful end members, of which four could be linked to a distinct source and transport mechanism of clastic mineral input: fine aeolian dust from distal sources (EM1), fine catchment runoff (EM2), coarser aeolian dust from proximal sources (EM5) and coarse erosive material from the upper crater slopes (EM6). The two other end members (EM3 and EM4) represented frustules of the two most common diatom taxa in Lake Chala, Afrocymbella barkeri and Nitzschia fabiennejansseniana, which had (partly) survived sample pre-treatment. Temporal variation in normalized abundance of the two dust-derived end members are valuable proxies for past changes in monsoon circulation over equatorial East Africa. During Northern Hemisphere cold periods (e.g., Last Glacial Maximum and Younger Dryas) the Inter-Tropical Convergence Zone shifted southward, enhancing northeasterly monsoon winds in the Lake Chala area and increasing advection of fine dust from the dry Horn of Africa region. Simultaneously, more modest continental heating reduced the prevalence of small-scale atmospheric turbulence, and thus the occurrence of dust devils, resulting in reduced influx of coarse dust from drylands nearby. Conversely, abrupt intensification of the southeasterly monsoon at the onset of the Holocene is recorded by an abrupt increase in the amount of coarse dust delivered to Lake Chala. Temporal variation in the end members representing catchment run-off (EM2) and erosion (EM6) mainly reflect changes in lacustrine sedimentation dynamics associated with major lake-level fluctuation, as evidenced by other paleoenvironmental proxies. Overall this study shows that subdivision of the clastic fraction of lacustrine sediments into statistically robust grain-size end members can provide multiple independent and quantitative proxies which help constrain reconstructions of a region's multi-faceted climate history. © 2020 The Authors
Keywords: Bourgogne-Franche-Comte; France; Horn of Africa; Jura [Bourgogne-Franche-Comte]; Kilimanjaro [Kilimanjaro (RGA)]; Kilimanjaro [Tanzania]; Lake Chalain; Tanzania; Bacillariophyta; Nitzschia; Atmospheric thermodynamics; Atmospheric turbulence; Catchments; Climate change; Dust; Glacial geology; Grain size and shape; Lakes; Runoff; Size distribution; Amorphous organic matters; Grain size distribution; Intertropical convergence zone; Lacustrine sedimentations; Lacustrine sediments; Lake level fluctuations; Northern Hemispheres; Small-scale atmospheric turbulence; crater lake; diatom; environmental change; eolian deposit; grain size; lacustrine deposit; Last Glacial Maximum; paleoenvironment; proxy climate record; sedimentation; Sediments

Reflection seismic surveys to site the Drilling the Ivrea Verbano zonE (DIVE) proposed drill-holes, Val Sesia and Val d’Ossola, Italy. - Greenwood, Andrew; Baron, Ludovic; Liu, Yu; Het'enyi, Gy{orgy; Holliger, Klaus; Pistone, Mattia; Zanetti, Alberto; Ziberna, Luca; M{untener, Othmar (Copernicus Meetings, 2020)

Petrograpic and material observations of basaltic lapilli tuff, 1979 and 2017 Surtsey drill cores, Iceland - Jackson, Marie D (Surtsey Res, 2020)

Petrophysical properties, mechanical behaviour, and failure modes of impact melt-bearing breccia (suevite) from the Ries impact crater (Germany) - Heap, M.J.; Gilg, H.A.; Byrne, P.K.; Wadsworth, F.B.; Reuschl'e, T. (Icarus, 2020)
The physical properties and mechanical behaviour of impactites are an important parameter in fluid flow models and slope stability and landscape evolution assessments for heavily impacted planetary bodies. We first present porosity, permeability, Young's modulus, and uniaxial compressive strength measurements for three suevites from the Ries impact crater (Germany). Porosity ranges from 0.18 to 0.43, permeability from 5.8 × 10− 16 to 5.1 × 10− 14 m2, Young's modulus from 1.4 to 8.1 GPa, and uniaxial compressive strength from 7.3 to 48.6 MPa. To explore their mechanical behaviour, we performed triaxial deformation experiments on these samples at a range of confining pressures. The brittle –ductile transition for the lowest (0.25) and highest (0.38) porosity suevite samples was at a confining pressure of 30 and 10 MPa, respectively (corresponding to, for example, depths of 1 and 4 km on Mars, respectively). Microstructural observations show that the dominant deformation micromechanism during brittle deformation is microcracking, and during ductile deformation is distributed cataclastic pore collapse. We show that a theoretically grounded permeability model for welded granular media accurately captures the permeability of the studied suevites, and we use micromechanical models to glean insight as to their mechanical behaviour. Finally, we upscale our laboratory measurements to provide physical property values for length scales more relevant for large-scale models, and we compare these data with those for basalt (a lithology representative of the surface of the inner Solar System bodies). These analyses show how macroscopic fractures serve to increase the permeability and decrease the strength and Young's modulus of suevite and basalt. We also find, for example, that basalt can be a factor of 2 –5 stronger than suevite in the shallow crust. Our study suggests, therefore, that the rock masses comprising older, bombarded crusts are substantially weaker and more porous and permeable than the younger plains material on these bodies. These findings should be considered in large-scale fluid flow modelling and when providing crustal strength estimates or slope stability assessments for planetary bodies on which protracted records of impact bombardment are preserved. © 2020 Elsevier Inc.
cited By 3

Microbial diversity of drilling fluids from 3000m deep Koyna pilot borehole provides insights into the deep biosphere of continental earth crust - Bose, Himadri; Dutta, Avishek; Roy, Ajoy; Gupta, Abhishek; Mukhopadhyay, Sourav; Mohapatra, Balaram; Sarkar, Jayeeta; Roy, Sukanta; K. Kazy, Sufia; Sar, Pinaki (Scientific Drilling, 2020)

Petrographic characterization of Archaean impact spherule layers from Fairview Gold Mine, northern Barberton Greenstone Belt, South Africa - Oliveira, Grace Juliana Gonçalves de; Reimold, Wolf Uwe; Cr'osta, Alvaro Penteado; Hauser, Natalia; Mohr-Westheide, Tanja; Tagle, Roald; Galante, Douglas; Kaufmann, Felix (Journal of African Earth Sciences, 2020)
The oldest known evidence of large impacts in Early Earth history are Archaean to Palaeoproterozoic impact spherule layers of the Barberton Greenstone Belt in South Africa and the Pilbara craton in Western Australia. Four drill core sections (BH5901, BH5907, BH5911 and BH5949) containing spherule layers were intersected in exploration drilling at Fairview Gold Mine in the northern Barberton Greenstone Belt. Here, we provide a first detailed mineralogical study of these new spherule layer intersections. The spherule layers are densely packed with sand-sized, spherical to ovoid, i.e., in part strongly deformed, “beads”. They generally have morphological and textural features similar to other 3.4 –3.2 Ga old spherule layers of the Barberton Greenstone Belt. The Fairview spherule layers are stratigraphically positioned at the contact between the silicified volcanic tuff of the uppermost unit of the Onverwacht Group and the lowermost siliciclastic rocks of the Fig Tree Group, like the S2 and S4 layers in the southern, and S3 layer in the northern, domain of the greenstone belt. Micro-XRF scanning allowed (i) to distinguish spherule layers from their host rocks by their major element distribution, and (ii) to characterize secondary alteration and micro-deformation features in the SL and host rocks. Ni –Cr spinel, the only primary mineral in evidence in these sections, is not distributed uniformly along a spherule layer intersection, and occurrences can not be stratigraphically correlated between the four layer intersections either. Spinel crystals vary with respect to Ni, Cr, Fe and Zn contents and respective zonation patterns for these elements. Zinc abundances are likely related to post-depositional hydrothermal overprint. The results of this investigation comprising geological, petrographic, semiquantitative micro-X-ray fluorescence spectrometry, and quantitative electron microprobe analysis on spinel support a complex and heterogeneous genetic process that must have taken place during spherule formation in an impact vapor plume and in post-depositional times. The Fairview spherule layers are thought to possibly represent the product of a single impact event. They represent fallout into deep-water conditions, as they lack evidence for reworking or sorting by current or wave action. The heterogeneous Ni –Cr spinel concentrations are similar to what has been reported for spinel occurrences in the S3 layer, but considering the complex tectonic overprint on this lithostratigraphic sequence at the changeover from the Onverwacht to the Fig Tree Group it is not possible to conclude whether or not these spherule layers represent the same impact event. © 2019 Elsevier Ltd
Keywords: Australia; Barberton Greenstone Belt; Pilbara Block; Western Australia; Ficus (angiosperm); Archean; host rock; lithostratigraphy; mineralogy; petrography; Proterozoic; siliciclastic deposit; spinel; tuff; X-ray fluorescence

New Jersey's paleoflora and eastern North American climate through Paleogene –Neogene warm phases - Prader, S.; Kotthoff, U.; Greenwood, D.R.; McCarthy, F.M.G.; Schmiedl, G.; Donders, T.H. (Review of Palaeobotany and Palynology, 2020)
Pollen of middle Oligocene to early Miocene age from core sediments from the New Jersey Shallow Shelf (Atlantic Coastal Plain: IODP-Expedition 313, Site M0027A), was analyzed using light- and scanning electron microscopy, and a pollen-based bioclimatic analysis was performed. The microflora is dominated by Quercus pollen. Pollen ornamentations indicate that Quercus pollen most likely originated from species of sections Quercus, Lobatae, Quercus/Lobatae and aff. section Protobalanus. Eotrigonobalanus, an extinct Fagaceae lineage, was present in the coastal plain. Relative abundances of several tree taxa (e.g., Carya) did not change significantly between the Oligocene warm phases, but contrast to late middle Miocene (comprising most of the Langhian and Serravallian) records from the same area. By assigning terrestrial palynomorphs to paleovegetation units, topographic movements of these units were identified. The mesophytic forest was the most widespread and zonal vegetation type in the hinterland through the analyzed interval. Periodic changes in the relative abundances of paleovegetation units suggest altitudinal vegetation movements responding to global climate change. Observed movement signals are generally weak, but increases in bisaccate pollen, representing spread of high- and mid-latitude forest, probably reflect the onset of cold intervals such as cooling phases at 29.1, 28.5, and 23.5 Ma. Spread of edaphically controlled forest formations during regression phases also indicates climate change. The onset of the Mi-1 event at 23.03 Ma is probably reflected by a decrease in pollen-inferred paleotemperatures, although the event itself occurred during a sedimentation hiatus. Pollen-based paleoclimate reconstructions indicate long-term stability in temperature and precipitation within the humid warm temperate zone. © 2020 Elsevier B.V.
cited By 6
Keywords: climate variation; deciduous tree; dominance; fossil record; Miocene; Neogene; Oligocene; paleobotany; Paleogene; paleotemperature; palynomorph; pollen; relative abundance; sediment core; topography; New Jersey; North America; United States; Carya; Fagaceae; Quercus

Revised chronology of the ICDP Dead Sea deep drill core relates drier-wetter-drier climate cycles to insolation over the past 220 kyr - Goldstein, S.L.; Kiro, Y.; Torfstein, A.; Kitagawa, H.; Tierney, J.; Stein, M. (Quaternary Science Reviews, 2020)
The Dead Sea Deep Drilling Project drilled 456 meters into the deepest floor of the Dead Sea and recovered a record of the past ∼220 kyr of the Levant hydroclimate history, that is, Marine Isotope Stages 1 –7, including the last three interglacials and the last two glacials. We present an updated chronology of the core from DSDDP Hole 5017-1-A, from the Dead Sea's deepest basin, that refines our previous chronology (Torfstein et al. 2015) based on new information. The updated chronology uses the following approaches: (1) radiocarbon ages of Kitagawa et al. (2017); (2) correlation of specific layers in the core with U –Th-dated sediments on the Dead Sea margin, particularly during the interval of glacial Lake Lisan (MIS 2,3,4); (3) tuning of the δ18O data of DSDDP core aragonite to the U –Th dated oxygen isotopes of regional cave speleothems; and (4) tuning of the DSDDP aragonite δ18O data to summer insolation curves when the cave δ18O chronology is less clear. The updated chronology reveals a strong relationship between the sedimentary facies comprising the core and Northern Hemisphere summer insolation variations. It shows that sequences of sediments marking drier/wetter/drier climate conditions in the lake's watershed (e.g., salt/muds/salt, respectively) appear across the flank/peak/flank segments of several summer insolation peaks. In particular, the transition from drier to wetter sedimentary facies during mid-latitude insolation peaks coincides with the intervals of sapropel conditions in the Mediterranean, reflecting enhanced Nile flow due to intense African monsoonal conditions, and marking the impact of the tropical precession cycles on Eastern Mediterranean hydroclimate. This pattern was lost during MIS 2,3,4, when mostly sequences of primary aragonite are punctuated by gypsum precipitation during Heinrich events, marking the strong impact of the North Atlantic on the last glacial Levant hydroclimate. © 2020 Elsevier Ltd
cited By 18
Keywords: Carbonate minerals; Caves; Driers (materials); Glacial geology; Incident solar radiation; Infill drilling; Isotopes; Lakes; Sedimentology; Climate condition; Eastern Mediterranean; Gypsum precipitation; Heinrich Events; Marine isotope stages; Northern Hemispheres; Oxygen isotopes; Sedimentary facies; Core drilling; aragonite; chronology; climate conditions; climate cycle; Deep Sea Drilling Project; hydrometeorology; insolation; marine isotope stage; Northern Hemisphere; watershed; wetting-drying cycle; Atlantic Ocean; Atlantic Ocean (North); Dead Sea; Mediterranean Sea; Mediterranean Sea (East)