All ICDP Publications with Abstracts
From parent-sysfolder "Publications" + 2 folder-levels deep
2678.
The post-Caledonian thermo-tectonic evolution of Fennoscandia
Gondwana Research,
107201--234
2022
ISSN: 1342-937XKeywords:▾
Exhumation, AFTA, Craton, Missing section, Peneplain
Abstract: ▾ The evolution of Fennoscandia following the early Devonian collapse of the Caledonian mountains is a matter of debate, due largely to the scarcity of post-Caledonian cover rocks. The preserved geological record therefore provides only partial documentation of the geological evolution. A more complete understanding is obtained by also considering evidence of rocks that were formerly present but have since been removed. We report apatite fission track data and associated thermal history constraints in 331 samples of Precambrian basement, younger sedimentary cover, Paleozoic and Mesozoic igneous rocks from outcrops and boreholes (up to 6 km depth) across Fennoscandia, which define thirteen phases of cooling (each representing kilometre-scale exhumation) over the last 1100 Myr. Key post-Caledonian episodes began in the intervals 311–307 Ma (late Carboniferous), 245–244 Ma (Middle Triassic), 170–167 Ma (Middle Jurassic), 102–92 Ma (mid-Cretaceous) and 23–21 Ma (early Miocene). These episodes, varying in magnitude, are recognised across Fennoscandia, and their effects are documented in the stratigraphic record and as prominent regional peneplains. The results define a history involving repeated episodes of regional burial and exhumation. Major offsets in Mesozoic paleotemperatures over short distances define kilometre-scale differential vertical displacements, emphasising the tectonic nature of the history. Results from Finland record the same events recognised in Norway and Sweden (though less pronounced), and are not consistent with long-term cratonic stability. The lack of preserved Phanerozoic sedimentary cover in Finland is interpreted to be due to complete removal during multiple episodes of denudation. In southern Norway and Sweden, early Miocene exhumation led to creation of a peneplain, which in Pliocene times was uplifted and dissected, producing the modern landscape. Post-Caledonian exhumation episodes defined here are broadly synchronous with similar events in Greenland, the British Isles and North America. Far-field transmission of plate-tectonic stress and/or mantle processes may explain the vertical movements described here.
2677.
Intensified microbial sulfate reduction in the deep Dead Sea during the early Holocene Mediterranean sapropel 1 deposition
Geobiology,
20
(4)
518-532
2022
ISSN: 14724677
Publisher: John Wiley and Sons Inc
Keywords:▾
biomarker; cyanobacterium; Holocene; isotopic composition; lipid; microbial activity; phytoplankton; reduction; sapropel; stable isotope; sulfate, Dead Sea; Mediterranean Sea, benzopyran derivative; sapropel; sulfate; water, chemistry; ecosystem; humic substance; lake; sediment, Benzopyrans; Ecosystem; Geologic Sediments; Humic Substances; Lakes; Sulfates; Water
Abstract: ▾ The hypersaline Dead Sea and its sediments are natural laboratories for studying extremophile microorganism habitat response to environmental change. In modern times, increased freshwater runoff to the lake surface waters resulted in stratification and dilution of the upper water column followed by microbial blooms. However, whether these events facilitated a microbial response in the deep lake and sediments is obscure. Here we investigate archived evidence of microbial processes and changing regional hydroclimate conditions by reconstructing deep Dead Sea chemical compositions from pore fluid major ion concentration and stable S, O, and C isotopes, together with lipid biomarkers preserved in the hypersaline deep Dead Sea ICDP-drilled core sediments dating to the early Holocene (ca. 10,000 years BP). Following a significant negative lake water balance resulting in salt layer deposits at the start of the Holocene, there was a general period of positive net water balance at 9500–8300 years BP. The pore fluid isotopic composition of sulfate exhibit evidence of intensified microbial sulfate reduction, where both (Formula presented.) and (Formula presented.) of sulfate show a sharp increase from estimated base values of 15.0‰ and 13.9‰ to 40.2‰ and 20.4‰, respectively, and a (Formula presented.) vs. (Formula presented.) slope of 0.26. The presence of the n-C17 alkane biomarker in the sediments suggests an increase of cyanobacteria or phytoplankton contribution to the bulk organic matter that reached the deepest parts of the Dead Sea. Although hydrologically disconnected, both the Mediterranean Sea and the Dead Sea microbial ecosystems responded to increased freshwater runoff during the early Holocene, with the former depositing the organic-rich sapropel 1 layer due to anoxic water column conditions. In the Dead Sea prolonged positive net water balance facilitated primary production and algal blooms in the upper waters and intensified microbial sulfate reduction in the hypolimnion and/or at the sediment–brine interface. © 2022 The Authors. Geobiology published by John Wiley & Sons Ltd.
2676.
Biomarker proxy records of Arctic climate change during the Mid-Pleistocene transition from Lake El'gygytgyn (Far East Russia)
Climate of the Past,
18
(3)
559-577
2022
ISSN: 18149324
Publisher: Copernicus GmbH
Keywords:▾
biomarker; climate change; glacial-interglacial cycle; Pleistocene; vegetation cover; warming, Chukchi; Elgygytgyn Lake; Russian Federation
Abstract: ▾ The Mid-Pleistocene Transition (MPT) is a widely recognized global climate shift occurring between approximately 1250 and 700ka. At this time, Earth's climate underwent a major transition from dominant 40kyr glacial-interglacial cycles to quasi-100kyr cycles. The cause of the MPT remains a puzzling aspect of Pleistocene climate. Presently, there are few, if any, continuous MPT records from the Arctic, yet understanding the role and response of the high latitudes to the MPT is required to better evaluate the causes of this climatic shift. Here, we present new continental biomarker records of temperature and vegetation spanning 1142 to 752ka from Lake El'gygytgyn (Far East Russia). We reconstruct warm-season temperature variations across the MPT based on branched glycerol dialkyl glycerol tetraethers (brGDGTs). The new Arctic temperature record does not display an overall cooling trend during the MPT but does exhibit strong glacial-interglacial cyclicity. Spectral analysis demonstrates persistent obliquity and precession pacing over the study interval and reveals substantial sub-orbital temperature variations at 1/4900ka during the first "skipped"interglacial. Interestingly, Marine Isotope Stage (MIS) 31, which is widely recognized as a particularly warm interglacial, does not exhibit exceptional warmth in the Lake El'gygytgyn brGDGT record. Instead, we find that MIS 29, 27, and 21 were as warm or warmer than MIS 31. In particular, MIS 21 (1/4870 to 820ka) stands out as an especially warm and long interglacial in the continental Arctic while MIS 25 is a notably cold interglacial. Throughout the MPT, Lake El'gygytgyn pollen data exhibit a long-term drying trend, with a shift to an increasingly open landscape noted after around 900ka (Zhao et al., 2018), which is also reflected in our higher plant leaf wax (n-alkane) distributions. Although the mechanisms driving the MPT remain a matter of debate, our new climate records from the continental Arctic exhibit some similarities to changes noted around the North Pacific region. Overall, the new organic geochemical data from Lake El'gygytgyn contribute to expanding our knowledge of the high-latitude response to the MPT. © 2022 Kurt R. Lindberg et al.
2675.
Application of SPAC Method to Survey Deep Geothermal Water Storage Structures in SK-2; [基于SPAC法探测松科二井深层地热储水构造]
Acta Geoscientica Sinica,
43
(6)
909 – 916
2022
ISSN: 10063021
Publisher: Science Press
Abstract: ▾ As a method for acquiring the velocity structure of underground strata and hidden structural faults, microtremor surveying is very popular for shallow exploration in cities and villages because of its advantages of no active source, convenient survey process, and strong anti-interference ability. To explore the deep geothermal resource potential of the northern Songliao Basin in greater detail, the subsurface fine velocity structure within the burial depth range from the Nenjiang Formation to the Denglouku Formation at the bottom of the depression was obtained by using the micro motion detection method in and around Songke Well No. 2 (SK-2) south of Anda City, Heilongjiang Province. Based on the spatial autocorrelation method (SPAC), the S-wave dispersion curve was extracted from the vertical component of the micro motion signal and transformed into the apparent S-wave velocity curve. Finally, through interpolation and smooth calculation, a two-dimensional underground S-wave velocity structure section spanning 9 km and reaching 4000 m beneath the surface was obtained. Analysis of the micro motion profile revealed that the subsurface S-wave velocity generally shows a trend of high velocity in the west and low velocity in the east. There are three obvious low-speed anomaly zones with depths ranging from 1400 m to 2800-100 m in the west, 2300 m in the east, and 3700 m to the east of well SK-2-indicating that there are likely faults or hidden fault structures at these locations. By combining these data with the stratigraphic data, the Quantou and Denglouku Formations were determined as the main units in this depth range, and the lithology is mostly interbedded sandstone and mudstone. These are suitable units for hydrothermal storage. The study shows that the lateral low-velocity anomaly of the surface wave results can be used as a basis of discrimination for identifying deep geothermal water storage structures and can provide direction for further clean energy investigation in this area. © 2022, Science Press. All right reserved.
2674.
Archaeal lipids reveal climate-driven changes in microbial ecology at Lake El'gygytgyn (Far East Russia) during the Plio-Pleistocene
Journal of Quaternary Science,
37
(5)
900-914
2022
ISSN: 02678179
Publisher: John Wiley and Sons Ltd
DOI:10.1002/jqs.3347
Keywords:▾
biogeochemistry; biomarker; climate variation; isoprenoid; lacustrine environment; lake water; lipid; microbial ecology; paleoclimate; paleoenvironment; permafrost; Pliocene; Pliocene-Pleistocene boundary; proxy climate record; timescale, Chukchi; Elgygytgyn Lake; Russian Federation
Abstract: ▾ Isoprenoid glycerol dialkyl glycerol tetraethers (iGDGTs) are commonly preserved molecular biomarkers of archaea whose distributions can be used to reconstruct past temperature, and possibly, methane and nitrogen cycling. To date, iGDGT systematics have not been widely investigated in Arctic lacustrine environments. Here, we analyze iGDGTs in sediments of Lake El'gygytgyn, located in the Russian Arctic, to reconstruct the paleoenvironmental conditions from the Pliocene to today using TEX86 and other indices. The TEX86-inferred temperature history shows a long-term warming trend, in stark contrast to other Arctic records and other proxies from Lake El'gygytgyn, suggesting that non-temperature factors obfuscate the use of TEX86 at this site. Other GDGT-based indices including the BIT Index, ΔRing Index, Methane Index and the GDGT-0/crenarchaeol ratio suggest that TEX86 is strongly influenced by archaeal community changes. The most significant community shifts are observed c. 2.4 Ma and record an increase in Euryarchaeota production and/or a decrease in Thaumarchaeota production, which was driven by the establishment of permafrost and perennial lake ice during the early Pleistocene. Overall, this study demonstrates an important interpretative framework for iGDGTs in lacustrine systems and describes variations in Arctic climate and lake biogeochemistry over timescales of thousands to millions of years. © 2021 John Wiley & Sons, Ltd.
2673.
Artificial Water Reservoir-Triggered Seismicity (RTS): Most Prominent Anthropogenic Seismicity
Surveys in Geophysics,
43
(2)
619-659
2022
ISSN: 01693298
Publisher: Springer Science and Business Media B.V.
Keywords:▾
Boreholes; Diffusion in liquids; Earthquakes; Faulting; Induced Seismicity; Petroleum reservoir engineering; Pore pressure; Stresses, Anthropogenics; Artificial water; Coal-mining; Deep boreholes; Drilling projects; Geological conditions; High water; Permeability; Reservoir-triggered seismicity; Water reservoir level, Abstracting, diffusion; earthquake magnitude; environmental stress; fault zone; permeability; pore pressure; seismicity, India; Koyna; Maharashtra
Abstract: ▾ Abstract: Under certain suitable geological conditions, anthropogenic seismicity due to gold/coal mining, geothermal and natural gas/oil production, filling of artificial water reservoirs, and high-pressure fluid injection has been reported globally. The reservoir-triggered seismicity (RTS) is most prominent, having been reported from hundreds of with at least five sites where earthquakes exceeding M 6 occurred, claiming human lives and destruction of properties. The most important correlate for RTS to occur is the height of water column in the reservoir. Certain common characteristics of the RTS sequences have been identified, which discriminate them from normal earthquake sequences. Factors influencing RTS include the highest water levels reached in the reservoir, duration of the retention of high-water levels and rate of loading/unloading. The mechanism of RTS is reviewed. The absence of knowledge of physical properties of rocks and fluids in the fault zone does not permit us to comprehend the RTS mechanism. Koyna, India, is found to be a very suitable site for such investigations as the earthquakes have been occurring in a small region of 20 × 30 km, at shallow depths (mostly within 8 km), with no other seismic source in the vicinity, and the region being accessible for all kinds of observation and investigations. The suitability of Koyna for setting up of a deep borehole laboratory was discussed during International Continental Drilling Program (ICDP) workshop in 2011 and accepted. Suggestions were made for some additional scientific works, which were completed during 2011–2014. The second ICDP workshop in 2014 approved of going ahead. A 3-km-deep Pilot Borehole has been completed in the vicinity of Donachiwada fault that hosted the main 10 December 1967 M 6.3 earthquake and several earthquakes of M ~ 5. The investigations being carried out are providing the necessary input to set up the proposed ~ 7-km-deep borehole laboratory. In this article, an overview of RTS globally and at Koyna, India, specifically is focused. Article Highlights: Global review of the reservoir-triggered seismicity (RTS) sitesFactors influencing RTS, their common characteristics and mechanismContinued seismicity at Koyna, India, and near-field studies © 2021, The Author(s), under exclusive licence to Springer Nature B.V.
2672.
Benthic-Pelagic state changes in the primary trophic level of an ancient tropical lake
Palaeogeography, Palaeoclimatology, Palaeoecology,
594
2022
ISSN: 00310182
Publisher: Elsevier B.V.
Keywords:▾
Greater Sunda Islands; Lake Towuti; Malili Lakes; South Sulawesi; Sulawesi; Sunda Isles; benthic-pelagic coupling; plankton; primary production; sediment chemistry; trophic level
Abstract: ▾ Many large, ancient lakes support primarily planktonic-driven food webs. In contrast, the lowest trophic levels of the Malili Lakes of Sulawesi Island, Indonesia are dominated by benthic diatom communities composed mainly of endemic species. Centric diatoms are not observed in the current diatom assemblage and pennate pelagic species are rare. Using two deep drill-cores from Lake Towuti, we investigated whether the lake has always been dominated by benthic primary production. Despite the ultra-oligotrophic conditions observed in the lake today, we observed state changes characterized by productive planktonic communities and less productive, benthic-dominated diatom assemblages. Two periods of planktonic production, each lasting approximately 50 kyr, were dominated by a complex mixture of Aulacoseira spp., with valve densities >1.0 × 109 valves/g with a maximum biovolume of 3.5 × 1012 μm3/g. A similar planktonic assemblage was observed at much lower abundances (<107valves/g) in the deeper sediments (>1 Ma), during the earliest stages of lake formation. Two periods of increased benthic primary production of approximately ~11 kyr in duration, originating from the littoral zone of the lake, were also observed, one between the two planktonic phases and one above the last planktonic maxima. The benthic periods were dominated by Cymbopleura spp., with valve densities of approximately 2.0 × 108 valves/g and a maximum biovolume of 1.2 × 1011 μm3/g. Nonmetric multidimensional scaling analysis of sediment chemistry revealed that the benthic and pelagic states clustered with distinct chemical environments. The benthic phases were associated with well-mixed conditions in the lake whereas the planktonic phases were related to rapidly reoccurring water column mixing followed by intense stratification that generate nutrient recycling events. We conclude that lake mixing and nutrient cycling regimes regulated, in part, the switch between benthic and pelagic states in Lake Towuti. © 2022
2671.
Big volcano science: needs and perspectives
Bulletin of Volcanology,
84
(3)
2022
ISSN: 02588900
Publisher: Springer Science and Business Media Deutschland GmbH
Keywords:▾
magma; volcano; volcanology
Abstract: ▾ Volcano science has been deeply developing during last decades, from a branch of descriptive natural sciences to a highly multi-disciplinary, technologically advanced, quantitative sector of the geosciences. While the progress has been continuous and substantial, the volcanological community still lacks big scientific endeavors comparable in size and objectives to many that characterize other scientific fields. Examples include large infrastructures such as the LHC in Geneva for sub-atomic particle physics or the Hubble telescope for astrophysics, as well as deeply coordinated, highly funded, decadal projects such as the Human Genome Project for life sciences. Here we argue that a similar big science approach will increasingly concern volcano science, and briefly describe three examples of developments in volcanology requiring such an approach, and that we believe will characterize the current decade (2020–2030): the Krafla Magma Testbed initiative; the development of a Global Volcano Simulator; and the emerging relevance of big data in volcano science. © 2022, The Author(s).
2670.
Bimodal alteration of the oceanic crust revealed by halogen and noble gas systematics in the Oman Ophiolite
Journal of Geophysical Research: Solid Earth,
127
(1)
e2021JB022669
2022
2669.
Borehole logging and seismic data from Lake Ohrid (North Macedonia/Albania) as a basis for age-depth modelling over the last one million years
Quaternary Science Reviews,
276
2022
ISSN: 02773791
Publisher: Elsevier Ltd
Keywords:▾
Albania; Lake Ohrid; Macedonia; Cluster analysis; Lakes; Lithology; Seismic response; Seismic waves; Time series analysis; Albania; Borehole logging; Cyclostratigraphy; Depth models; Downhole methods; Downholes; Lake Ohrid; Macedonia; Sediment properties; Seismic interpretation; borehole logging; cluster analysis; magnetostratigraphy; modeling; sediment core; sedimentation; seismic data; seismic survey; Sediments
Abstract: ▾ Robust age-depth models are essential for developing sophisticated interpretations of the sedimentological history in lake basins. In most cases, such models are created using an integrated geoscientific approach, including biostratigraphy, magnetostratigraphy and radiometric dating. In this study, we present an approach to construct age-depth models based on integrating downhole logging and seismic survey data when there are no samples available for dating. An example of this method is shown using data from Lake Ohrid (North Macedonia/Albania). First, we interpret seismic data and correlate downhole logging data from three sites - DEEP, Pestani and Cerava - to the LR04 benthic stack. We cross-check the resulting age-depth models using cyclostratigraphic methods, which deliver sedimentation rates that are on the same order of magnitude. The maximum age of the investigated sediments is based on lacustrine seismic marker horizons and is approximately 1 million years at DEEP/Pestani and 0.6 million years at Cerava. In the second step, we construct an artificial lithological log based on cluster analysis using the physical properties of the sediments and integrate it with the age-depth model. This allows an initial interpretation of the sedimentological history at Cerava and Pestani. Our methodological approach cannot substitute classical sediment core investigations, but we suggest that this two-step approach be applied to future projects of the International Continental Scientific Drilling Program. It can rapidly provide preliminary results on age and sediment type and is particularly useful when datable material is not available. © 2021 The Authors
2668.
Application of Long-Tube Coring Technique in Quantou Formation of SK-3 well (in Chinese); 长筒取芯技术在松科三井泉头组地层的应用
West-China Exploration Engineering,
3474-77+79
2022
2667.
Borehole Seismic Observations From the Chicxulub Impact Drilling: Implications for Seismic Reflectivity and Impact Damage
Geochemistry, Geophysics, Geosystems,
23
(3)
2022
Abstract: ▾ We conducted a vertical seismic profile (VSP) in the borehole of International Ocean Discovery Program/International Continental Scientific Drilling Program Expedition 364 Site M0077 to better understand the nature of the seismic reflectivity and the in situ seismic properties associated with the Chicxulub impact structure peak ring. Extraction of the up-going wavefield from the VSP shows that a strong seismic reflection event imaged in seismic reflection data results from discontinuities in the elastic impedance Z (the product of density and wave speed) at the top and bottom of a zone of hydrothermally altered melt-bearing polymict breccia (suevite) that are characterized by anomalously low Z. Below this strong carbonate/suevite reflection event, the upgoing seismic wavefield is chaotic, indicating high levels of scattering from the suevites and underlying melt rocks and shocked granitoids of the peak ring, in contrast to the clear coherent reflections throughout the overlying Cenozoic sediments. We extract shear wave speeds, which, together with those provided from the complementary sonic log and densities from core scanning, allowed determination of VP/VS and Poisson's ratio v. These values are anomalously high relative to comparable terrestrial lithologies. We also calculate a variety of damage parameters for the disrupted peak ring granitoids. These values may assist in linking seismic observations to shock levels that are necessary to calibrate current impact models and may also be useful in assessing levels of fracturing within major fault zones. © 2022. The Authors.
2666.
Characteristics of Fault Rocks Within the Aftershock Cloud of the 2014 Orkney Earthquake (M5.5) Beneath the Moab Khotsong Gold Mine, South Africa
Geophysical Research Letters,
49
(14)
e2022GL098745
2022
Keywords:▾
earthquake, fault drilling, lamprophyre
Abstract: ▾ Abstract Cores recovered during the International Continental Scientific Drilling Program project “Drilling into Seismogenic zones of M2.0 to M5.5 earthquakes in deep South African Gold Mines” include fault breccia from within the aftershock cloud of the 2014 Orkney earthquake (M5.5). The breccia and surrounding intrusive rocks, probably lamprophyres rich in talc, biotite, calcite, and amphibole, had high magnetic susceptibilities owing to the presence of magnetite. All of these characteristics can be attributed to fluid-related alteration. Both the breccia and the lamprophyres had low friction coefficients and showed evidence of velocity strengthening, which is inconsistent with the occurrence of earthquakes. Variable amounts of talc, biotite, calcite, and amphibole within the lamprophyres might have produced complex frictional properties and spatial heterogeneity of fault stability. The altered lamprophyres may be the host rocks of the 2014 Orkney earthquake, but frictional complexity may have governed the magnitudes of the main- and aftershocks and their distributions.
2665.
Chemical weathering characteristics of the Late Cretaceous Nenjiang Formation from the Songliao Basin (Northeastern China) reveal prominent Milankovitch band variations
Palaeogeography, Palaeoclimatology, Palaeoecology,
601
2022
ISSN: 00310182
Publisher: Elsevier B.V.
Keywords:▾
China; Songliao Basin; chemical weathering; clastic sediment; correlation; Cretaceous; hydrological cycle; paleoclimate; spectral analysis
Abstract: ▾ The Songliao Basin (SLB) in Northeast China has a succession of terrestrial sedimentary deposits that span much of the Cretaceous. The sedimentary records recovered from SLB allow us to investigate the relationship between astronomically forced climate and clastic sediment accumulation in a terrestrial setting from the mid to high latitudes. Here, we compiled high-resolution X-Ray Fluorescence (XRF) datasets (K/Ti, Rb/Sr, Ca/Ti), and gamma ray (GR) logging data from Member 2 of the Nenjiang Formation in the SK-1n borehole. Power spectral analysis of the GR data revealed that sedimentary cycles had wavelengths of 27.4 m, 6.56 m, 2.60 m, and 1.27 m. These wavelengths are interpreted as the orbital cycles of long-eccentricity, short-eccentricity, obliquity, and precession, respectively. We established an astronomical time scale by assuming that the 27.4 m cycles represent ~405 kyr eccentricity. We also applied correlation coefficient (COCO) analysis to identify the astronomical forcing periods. The chemical weathering history was classified by the relative changes of Rb/Sr and K/Ti ratios. The lower Rb/Sr and higher K/Ti values correspond to weak weathering, interpreted as arid periods, and vice versa. Ca/Ti ratios correlate with the humid periods and we attribute this correspondence to a salinity control on Ca/Ti. Furthermore, the unconventional 173-kyr obliquity cycle associated with the secular frequency interference of orbital inclinations between Earth and Saturn was recognized and manifested by humid/arid cliamtic oscillations, suggesting that high obliquity contributed to strengthening the hydrological cycles in SLB and bringing more precipitation and runoff towards the basin. The unique paleogeographic location and the existing paleoclimate simulations of SLB further demonstrated the existence of paleomonsoon variations in East Asia during the Late Cretaceous. © 2022
2664.
Chicxulub Crater Joint Gravity and Magnetic Anomaly Analysis: Structure, Asymmetries, Impact Trajectory and Target Structures
Pure and Applied Geophysics,
179
(8)
2735-2756
2022
Abstract: ▾ Modeling gravity and magnetic anomalies over the Chicxulub crater are used to constrain the structure, stratigraphy, and asymmetries. Chicxulub is a multiring ~ 200 km rim diameter structure with a central uplift and well-preserved peak ring. The low relief terrain and physical property contrasts have facilitated geophysical modeling of the structure and impactite deposits. Nevertheless, contrasting models have been obtained due to data resolution limitations, uneven coverage, non-uniqueness solutions, boundary conditions, and heterogeneous/anisotropic media. We employ a multi-technique approach based on regional–residual separation, spectral analysis, first and second derivatives, upward and downward analytical continuations, horizontal gradients, analytical signal, Euler deconvolution, reduction to the pole, and forward modeling to constraint the anomaly sources, geometry and depths. Forward modeling of gravity anomaly favors central uplift flat-top models, whereas magnetic models show irregular shapes with a peak towards the NE, at 4–5 km depth. Analysis shows the effects of intersecting regional anomalies in the semicircular pattern that limit the definition of asymmetries, which constrains impact angle and trajectory, crater structure and pre-existing target features. Models link lateral–vertical density and magnetic property contrasts, distinguishing non-magnetic pre-and post-impact carbonates and carbonate-rich breccias from melt and basement rich breccias, and displaced, fractured impactites and basement uplift. © 2022, The Author(s), under exclusive licence to Springer Nature Switzerland AG.
2663.
Climatic Controls on a Holocene Mercury Stable Isotope Sediment Record of Lake Titicaca
ACS Earth and Space Chemistry,
6
(2)
346 – 357
2022
Keywords:▾
Lake Titicaca; atmospheric deposition; biogeochemistry; biomarker; climate change; erosion; geological record; Holocene; mercury (element); sediment core; stable isotope
Abstract: ▾ Mercury (Hg) records in sediment archives inform past patterns of Hg deposition and the anthropogenic contribution to global Hg cycling. Natural climate variations complicate the interpretation of past Hg accumulation rates (HgARs), warranting additional research. Here, we investigated Hg stable isotopes in a ca. 8k year-long sediment core of Lake Titicaca and combined isotopic data with organic biomarkers and biogeochemical measurements. A wet period in the early Holocene (8000-7300 BP) induced strong watershed erosion, leading to a high HgAR (20.2 ± 6.9 μg m-2 year-1), which exceeded the 20th century HgAR (8.4 ± 1.0 μg m-2 year-1). Geogenic Hg input dominated during the early Holocene (fgeog = 79%) and played a minor role during the mid- to late Holocene (4500 BP to present; fgeog = 20%) when atmospheric Hg deposition dominated. Sediment Δ200Hg values and the absence of terrestrial lignin biomarkers suggest that direct lake uptake of atmospheric Hg(0), and subsequent algal scavenging of lake Hg, represented an important atmospheric deposition pathway (42%) during the mid- to late Holocene. During wet episodes of the late Holocene (2400 BP to present), atmospheric Hg(II) deposition was the dominant source of lake sediment Hg (up to 82%). Sediment Δ199Hg values suggest that photochemical reduction and re-emission of Hg(0) occurred from the lake surface. Hg stable isotopes show promise as proxies for understanding the history of Hg sources and transformations and help to disentangle anthropogenic and climate factors influencing HgAR observed in sediment archives. © 2022 The Authors. Published by American Chemical Society
2662.
Complex Crater Formation by Oblique Impacts on the Earth and Moon
Geophysical Research Letters,
49
(21)
2022
Abstract: ▾ Almost all meteorite impacts occur at oblique incidence angles, but the effect of impact angle on crater size is not well understood, especially for large craters. To improve oblique impact crater scaling, we present a suite of simulations of complex crater formation on Earth and the Moon over a range of impact angles, velocities and impactor sizes. We show that crater diameter is larger than predicted by existing scaling relationships for oblique impacts; there is little dependence on obliquity for impacts steeper than 45° from the horizontal. Crater depth, volume and diameter depend on impact angle in different ways—relatively shallower craters are formed by more oblique impacts. Our simulation results have implications for how crater populations are determined from impactor populations and vice-versa. They suggest that existing approaches to account for impact obliquity may underestimate the number of complex craters larger than a given size by as much as one-third. © 2022. The Authors.
2661.
Application of machine learning to characterize gas hydrate reservoirs in Mackenzie Delta (Canada) and on the Alaska north slope (USA)
Computational Geosciences,
26
(5)
1151-1165
2022
ISSN: 14200597
Publisher: Springer Science and Business Media Deutschland GmbH
Keywords:▾
artificial neural network; gas hydrate; hydrocarbon reservoir; hydrocarbon resource; machine learning; nuclear magnetic resonance, Canada; Mackenzie Delta; Northwest Territories
Abstract: ▾ Artificial neural network-trained models were used to predict gas hydrate saturation distributions in permafrost-associated deposits in the Eileen Gas Hydrate Trend on the Alaska North Slope (ANS), USA and at the Mallik research site in the Beaufort-Mackenzie Basin, Northwest Territories, Canada. The database of Logging-While-Drilling (LWD) and wireline logs collected at five wells (Mount Elbert, Iġnik Sikumi, and Kuparuk 7–11–12 wells at ANS, plus 2L-38 and 5L-38 wells at the Mallik research site) includes more than 10,000 depth points, which were used for training, validation, and testing the machine learning (ML) models. Data used in training the ML models include the well logs of density, porosity, electrical resistivity, gamma radiation, and acoustic wave velocity measurements. Combinations of two or three out of these five well logs were found to reliably predict the gas hydrate saturation with accuracy varying between 80 and 90% when compared to the gas hydrate saturations derived from Nuclear Magnetic Resonance (NMR)-based technique. The ML models trained on data from three ANS wells achieved high fidelity predictions of gas hydrate saturation at the Mallik site. The results obtained in this study indicate that ML models trained on data from one geological basin can successfully predict key reservoir parameters for permafrost-associated gas hydrate accumulations within another basin. A generalized approach for selecting a well log combination that can improve model accuracy is discussed. Overall, the study outcome supports earlier work demonstrating that ML models trained on non-NMR well logs are a viable alternative to physics-driven methods for predicting gas hydrate saturations. © 2022, The Author(s), under exclusive licence to Springer Nature Switzerland AG.
2660.
Application of elemental capture spectroscopy in deep tight reservoir evaluation: A case study of well SK-2; [元素俘获能谱在深层致密储层评价中的应用: 以松科2井为例]
Earth Science Frontiers,
29
(1)
449 – 458
2022
ISSN: 10052321
Publisher: Science Frontiers editorial department
Keywords:▾
Brittleness; Fracture mechanics; Gases; Lithology; Organic carbon; Petroleum reservoir evaluation; Petroleum reservoirs; Plasticity; Porosity; Well logging; Brittleness index; Case-studies; Conventional well logs; Elemental capture spectroscopy; Gas logging; Gas potential; Shahezi formations; Songliao basin; Strong heterogeneities; Tight reservoir; Tight gas
Abstract: ▾ There are multiple gas logging anomalies in the Shahezi Formation, Songliao Basin, indicating its tight gas potential. However, deep tight reservoirs in the area have strong heterogeneity, thin thickness, interlayer development and various types. Based on the analysis of conventional well log of well SK-2, we used elemental capture spectroscopy (ECS) well logging to finely retrieve the mineral component content for accurate lithology identification, and subsequently identified five types of reservoirs by crossplot analysis. Combined with petrophysical experimental data, we further obtained the reservoir evaluation parameters such as variable skeleton porosity, brittleness index, and organic carbon content, which allowed us to categorize the reservoirs into three groups based on the well logging data and comprehensive evaluation indexes. In the Shahezi Formation (3730-4500 m), the porosity values range between 5%-9%, and the brittleness indexes range between 45%-60%. TOC of adjacent source rock is generally high, with relatively large accumulative thickness, and depth intervals at 3798-3831, 3950-3990 and 4150-4200 m show favorable tight gas potential for exploration and development. We demonstrated in this paper that, ECS well logging can accurately evaluate tight gas reservoirs so as to provide a reference basis for fracturing optimization in tight reservoirs. © 2022, Editorial Office of Earth Science Frontiers. All right reserved.
2659.
COSC-2 - drilling the basal décollement and underlying margin of palaeocontinent Baltica in the Paleozoic Caledonide Orogen of Scandinavia
Scientific Drilling,
3043--57
2022
ISSN: 1816-8957Abstract: ▾ {\textless}p{\textgreater}{\textless}strong class="journal-contentHeaderColor"{\textgreater}Abstract.{\textless}/strong{\textgreater} 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 décollement, 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 décollement and the expected rock types. Although the intensity of synsedime{\textless}span id="page44"/{\textgreater}ntary 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 décollement. 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.{\textless}/p{\textgreater}
2658.
A low-temperature, meteoric water-dominated origin for smectitic clay minerals in the Chicxulub impact crater upper peak ring, as inferred from their oxygen and hydrogen isotope compositions
Chemical Geology,
588
2022
Abstract: ▾ The peak-ring of the 66 Ma, ~180 km Chicxulub impact structure in the northern Yucatán peninsula and southern Gulf of Mexico was sampled during the International Ocean Discovery Program and International Continental Scientific Drilling Program (IODP–ICDP) Expedition 364 at Site M0077 (21.45° N, 89.95° W). Secondary clay minerals are pervasive throughout the upper peak-ring lithologies as a product of ubiquitous altered glass present throughout the impact melt and melt-bearing breccia sequence. Here we present the first detailed study of the clay mineralogy (microprobe, pXRD, spectral reflectance from 350 to 2500 nm) and isotope geochemistry (δ2H and δ18O) of the <0.2 μm size-fraction from upper peak-ring lithologies. The clay mineralogy is dominated by smectitic clay minerals, whose composition varies with stratigraphic position. Trioctahedral Mg[sbnd]Fe smectite (var. saponite) is most common in Units or Subunits 2A, 2C, 3 and 4, while a section of Subunit 2B contains a more dioctahedral, Al-rich smectite. Higher porosity regions of the lower to mid, dioctahedral smectite-dominated intervals have higher δ18O (+14.2 to +18.6‰) whereas intervals dominated by trioctahedral smectite have lower δ18O (+10.4 to +14.1‰). The range of smectite δ2H (−105 to −87‰), in comparison to that of oxygen isotopes, is proportionally much less variable and unrelated to smectite mineralogy. When combined, the oxygen and hydrogen isotope compositions of the smectitic clay minerals suggest low temperature (~20 to 50 °C) formation from meteoric water-dominated fluids. The lower end of this temperature range is below current ambient conditions, which conceivably could suggest smectite formation before much of the overlying sedimentary rocks were deposited (~56 Ma?). Calculated temperatures are generally lower than those associated with impact-generated hydrothermal alteration. Calculated δ18O and δ2H of meteoric water-dominated fluids associated with low-temperature formation of these clay minerals are lower than known for modern meteoric water in the Yucatán region. The simplest explanation for the source of these ancient fluids is meteoric water-dominated Gulf Coast brines. A more remote possibility is orogenically-driven, long-distance transport of groundwater from highlands to the east via an artesian aquifer formed in part by fractured Mesozoic rocks extending laterally beneath the impact structure. © 2021 Elsevier B.V.
2657.
ICDP research drilling in the Moodies Group of the Barberton Greenstone Belt is underway
Geobulletin,
6518-21
2022
2656.
700,000 years of tropical Andean glaciation
Nature,
607
(7918)
301 – 306
2022
ISSN: 00280836
Publisher: Nature Research
Keywords:▾
Greenland; Ice Cover; Temperature; Amazon River; Arctic; Greenland; glaciation; monsoon; Pleistocene; teleconnection; article; glaciation; Greenland; information center; periodicity; precipitation; ice cover; temperature
Abstract: ▾ Our understanding of the climatic teleconnections that drove ice-age cycles has been limited by a paucity of well-dated tropical records of glaciation that span several glacial–interglacial intervals. Glacial deposits offer discrete snapshots of glacier extent but cannot provide the continuous records required for detailed interhemispheric comparisons. By contrast, lakes located within glaciated catchments can provide continuous archives of upstream glacial activity, but few such records extend beyond the last glacial cycle. Here a piston core from Lake Junín in the uppermost Amazon basin provides the first, to our knowledge, continuous, independently dated archive of tropical glaciation spanning 700,000 years. We find that tropical glaciers tracked changes in global ice volume and followed a clear approximately 100,000-year periodicity. An enhancement in the extent of tropical Andean glaciers relative to global ice volume occurred between 200,000 and 400,000 years ago, during sustained intervals of regionally elevated hydrologic balance that modified the regular approximately 23,000-year pacing of monsoon-driven precipitation. Millennial-scale variations in the extent of tropical Andean glaciers during the last glacial cycle were driven by variations in regional monsoon strength that were linked to temperature perturbations in Greenland ice cores1; these interhemispheric connections may have existed during previous glacial cycles. © 2022, The Author(s).
2655.
A Four-Phase Model for Methane Production from an Unconsolidated Hydrate Reservoir. Part 1. Model Development
Industrial and Engineering Chemistry Research,
61
(20)
7103-7113
2022
ISSN: 08885885
Publisher: American Chemical Society
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
Abstract: ▾ 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.
2654.
A Four-Phase Model for Methane Production from an Unconsolidated Hydrate Reservoir. Part 2. Numerical Simulation
Industrial and Engineering Chemistry Research,
61
(20)
7114-7129
2022
ISSN: 08885885
Publisher: American Chemical Society
Keywords:▾
Gas hydrates; Hydration; Petroleum reservoir engineering, Flow modelling; Four-phase; Methane hydrates; Methane production; Model development; Phase flow; Phase model; Production test; Sand production; Solid deformation, Methane
Abstract: ▾ In this paper, the Mallik production tests are simulated using our four-phase flow model for an unconsolidated methane hydrate reservoir. Model development was outlined in part 1 of this paper series. The simulations suggest that the unconsolidated hydrate reservoir with sand production behaves like a naturally fracking reservoir. Solid deformation and the resultant permeability have a substantial effect on the gas production from an unconsolidated hydrate reservoir whether sand is produced or not. © 2022 American Chemical Society. All rights reserved.