All ICDP Publications with Abstracts
From parent-sysfolder "Publications" + 2 folder-levels deep
2644.
An astronomical age-depth model and reconstruction of moisture availability in the sediments of Lake Chalco, central Mexico, using borehole logging data
Quaternary Science Reviews,
294
2022
ISSN: 02773791
Publisher: Elsevier Ltd
Keywords:▾
Carbon dioxide; Climate models; Continuous time systems; Gamma rays; Glacial geology; Lakes; Magnetic susceptibility; Magnetism; Moisture determination; Sediments; Tropics, %moisture; Authigenic; Authigenic urania; Cyclostratigraphy; Depth models; Milankovitch cycle; Palaeoclimatology; Quaternary; Spectral gamma rays; Tropical north america, Moisture, astronomy; borehole logging; interglacial; lacustrine deposit; lake level; magnetic susceptibility; moisture content; paleoclimate; Pleistocene; Postglacial; precession; reconstruction; uranium, Federal District [Mexico]; Lake Chalco; Mexico City; Mexico [North America]
Abstract: ▾ Understanding the moisture history of low latitudes from the most recent glacial period of the latest Pleistocene to post-glacial warmth in continental tropical regions is hampered by the lack of continuous time series. We conducted downhole spectral gamma (γ) ray and magnetic susceptibility logs over 300 m of lacustrine deposits of Lake Chalco (Mexico City) to reconstruct an age-depth model using an astronomical and correlative approach, and to reconstruct long-term moisture availability. Our results suggest that the Lake Chalco sediments contain several rhythmic alternations with a quasi-cyclic pattern comparable to the Pleistocene benthic stack. This allows us to calculate a time span of about 500,000 years for this sediment deposition. We developed proxies for moisture, detrital input, and salinity, all based on the physical properties of γ-ray spectroscopy and magnetic susceptibility. Our results indicate that Lake Chalco formed during Marine Isotope Stage 13 (MIS13) and the lake level gradually increased over time until the interglacial MIS9. Moisture content is generally higher during interglacials than during glacials. However, two periods, namely MIS6 and MIS4, have higher moisture contents. We developed a model by comparing the obtained moisture proxy with climatic drivers, to understand how different climate systems drove effective moisture availability in the Chalco sub-basin over the past 500,000 years. Carbon dioxide, eccentricity, and precession are all key drivers of the moisture content of Lake Chalco over the past 500,000 years. © 2022 The Authors
2643.
An ostracod-based record of paleoecological conditions during MIS6 and MIS5, from Lake Chalco, Basin of Mexico
Journal of Paleolimnology,
67
(4)
359-373
2022
ISSN: 09212728
Publisher: Springer Science and Business Media B.V.
Keywords:▾
dissolved oxygen; environmental conditions; lake level; lake water; marine isotope stage; ostracod; paleoecology; runoff; seawater, Lake Chalco; Mexico [North America]; Valley of Mexico
Abstract: ▾ 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.
2642.
Anisotropic velocity models for (3-D) seismic imaging of the Lower Seve Nappe in Jämtland, Sweden
Geophysical Journal International,
228
(1)
66 – 77
2022
ISSN: 0956-540XAbstract: ▾ 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 Jämtland and other parts in the Caledonides.
2641.
Convective Melting and Water Behavior around Magmatic-Hydrothermal Transition: Numerical Modeling with Application to Krafla Volcano, Iceland
Journal of Petrology,
63
(8)
2022
2640.
86Kr excess and other noble gases identify a billion-year-old radiogenically-enriched groundwater system
Nature Communications,
13
(1)
2022
ISSN: 20411723
Publisher: Nature Research
Keywords:▾
ground water; helium; helium 4; inert gas; krypton 86; neon; radioisotope; unclassified drug; uranium; xenon; xenon 136; inert gas, basement rock; concentration (composition); groundwater resource; helium; microbial community; Precambrian, air pollution; Article; astronomy; chemical composition; concentration (parameter); controlled study; geological time; gold mining; hydrosphere; Precambrian; sediment; South Africa; surface property; water residence time; water supply; geology; microflora, South Africa, Earth, Planet; Geology; Groundwater; Microbiota; Noble Gases
Abstract: ▾ Deep within the Precambrian basement rocks of the Earth, groundwaters can sustain subsurface microbial communities, and are targets of investigation both for geologic storage of carbon and/or nuclear waste, and for new reservoirs of rapidly depleting resources of helium. Noble gas-derived residence times have revealed deep hydrological settings where groundwaters are preserved on millions to billion-year timescales. Here we report groundwaters enriched in the highest concentrations of radiogenic products yet discovered in fluids, with an associated 86Kr excess in the free fluid, and residence times >1 billion years. This brine, from a South African gold mine 3 km below surface, demonstrates that ancient groundwaters preserved in the deep continental crust on billion-year geologic timescales may be more widespread than previously understood. The findings have implications beyond Earth, where on rocky planets such as Mars, subsurface water may persist on long timescales despite surface conditions that no longer provide a habitable zone. © 2022, The Author(s).
2639.
Culturable Bacterial Diversity from the Basaltic Subsurface of the Young Volcanic Island of Surtsey, Iceland
Microorganisms,
10
(6)
1177
2022
2638.
High resolution environmental conditions of the last interglacial (MIS5e) in the Levant from Sr, C and O isotopes from a Jerusalem stalagmite
Palaeogeography, Palaeoclimatology, Palaeoecology,
586
2022
ISSN: 00310182
Publisher: Elsevier B.V.
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
Abstract: ▾ 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.
2637.
Frictional stability and hydromechanical coupling of serpentinite-bearing fault gouge
Geophysical Journal International,
231
(1)
290-305
2022
ISSN: 0956540X
Publisher: Oxford University Press
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
Abstract: ▾ 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.
2636.
Gas Migration Episodes Observed During Peridotite Alteration in the Samail Ophiolite, Oman
Geophysical Research Letters,
49
(21)
2022
ISSN: 00948276
Publisher: John Wiley and Sons Inc
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
Abstract: ▾ 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.
2635.
Geochemical Characterization of the Oman Crust-Mantle Transition Zone, OmanDP Holes CM1A and CM2B
Journal of Geophysical Research: Solid Earth,
127
(4)
2022
ISSN: 21699313
Publisher: John Wiley and Sons Inc
Keywords:▾
crust-mantle boundary; drilling; dunite; geochemistry; harzburgite; partial melting; serpentinization; transition zone, Oman
Abstract: ▾ 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.
2634.
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
Journal of the Geological Society,
179
(1)
2022
ISSN: 00167649
Publisher: Geological Society of London
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
Abstract: ▾ 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).
2633.
Geomechanical Response Induced by Multiphase (Gas/Water) Flow in the Mallik Hydrate Reservoir of Canada
SPE Journal,
27
(1)
434-451
2022
ISSN: 1086055X
Publisher: Society of Petroleum Engineers (SPE)
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
Abstract: ▾ 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
2632.
Half-precession signals in Lake Ohrid (Balkan) and their spatio-temporal relations to climate records from the European realm
Quaternary Science Reviews,
280
2022
2631.
High-precision geochronology of the Early Cretaceous Yingcheng Formation and its stratigraphic implications for Songliao Basin, China
Geoscience Frontiers,
13
(4)
2022
ISSN: 16749871
Publisher: Elsevier B.V.
Keywords:▾
chronostratigraphy; correlation; Cretaceous; geochronology; precision; uranium-lead dating, China; Songliao Basin
Abstract: ▾ 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
2630.
Fault systems in the offshore sector of the Campi Flegrei caldera
(southern Italy): Implications for nested caldera structure, resurgent
dome, and volcano-tectonic evolution
JOURNAL OF STRUCTURAL GEOLOGY,
163
2022
Abstract: ▾ 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.
2629.
High-resolution crustal structure in the Songliao basin [松辽盆地地壳精细结构研究]
Acta Seismologica Sinica,
44
(4)
555-566
2022
ISSN: 02533782
Publisher: Acta Seismologica Sinica Press
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
Abstract: ▾ 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.
2628.
Hydrogen-rich gas discovery in continental scientific drilling project of Songliao Basin, Northeast China: new insights into deep Earth exploration
Science Bulletin,
67
(10)
1003-1006
2022
ISSN: 20959273
Publisher: Elsevier B.V.
2627.
Hydrothermal regeneration of ammonium as a basin-scale driver of primary productivity
Astrobiology
2022
2626.
Hyperthermal events recorded in the Palaeogene carbonate sequence of southern Gulf of Mexico—Santa Elena borehole, Yucatan Peninsula
Geological Journal,
57
(1)
99-113
2022
DOI:10.1002/gj.4285
Abstract: ▾ 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.
2625.
ICDP Oman Drilling Project: varitextured gabbros from the dike--gabbro transition within drill core GT3A
European Journal of Mineralogy,
34
(6)
603--626
2022
2624.
Cuspate-lobate folding in glacial sediments revealed by a small-scale 3-D seismic survey
Journal of Applied Geophysics,
200
2022
2623.
Formation of the crater suevite sequence from the Chicxulub peak ring: A petrographic, geochemical, and sedimentological characterization
Bulletin of the Geological Society of America,
134
(3-4)
895-927
2022
DOI:10.1130/B36020.1
Abstract: ▾ 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
2622.
ICDP drilling of the Eger Rift observatory: magmatic fluids driving the earthquake swarms and deep biosphere
Scientific Drilling,
3131-49
2022
ISSN: 1816-34592621.
Extended-Range Luminescence Dating of Central and Eastern Amazonia Sandy Terrains
Frontiers in Earth Science,
10
2022
2620.
Drilling Overdeepened Alpine Valleys (ICDP-DOVE): Quantifying the age, extent, and environmental impact of Alpine glaciations
Scientific Drilling,
3151-70
2022
ISSN: 18168957
Publisher: Copernicus Publications
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
Abstract: ▾ 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: