All ICDP Publications with Abstracts
From parent-sysfolder "Publications" + 2 folder-levels deep
2394.
The mesoproterozoic stac fada member, nw scotland: An impact origin confirmed but refined
Journal of the Geological Society,
178
(1)
2020
Abstract: ▾ The origin of the Stac Fada Member has been debated for decades with several early hypotheses being proposed, but all invoking some connection to volcanic activity. In 2008, the discovery of shocked quartz led to the hypothesis that the Stac Fada Member represents part the continuous ejecta blanket of a meteorite impact crater, the location of which was, and remains, unknown. In this paper, we confirm the presence of shock-metamorphosed and-melted material in the Stac Fada Member; however, we also show that its properties are unlike any other confirmed and well documented proximal impact ejecta deposits on Earth. Instead, the properties of the Stac Fada Member are most similar to the Onaping Formation of the Sudbury impact structure (Canada) and impact melt-bearing breccias from the Chicxulub impact structure (Mexico). We thus propose that, like the Sudbury and Chicxulub deposits, Melt Fuel Coolant Interactions – akin to what occur during phreatomagmatic volcanic eruptions – played a fundamental role in the origin of the Stac Fada Member. We conclude that these rocks are not primary impact ejecta but instead were deposited beyond the extent of the continuous ejecta blanket as high-energy ground-hugging sediment gravity flows. © 2020 The Author(s). Published by The Geological Society of London. All rights reserved.
2393.
Millennial-scale vegetation history of the north-eastern Russian Arctic during the mid-Pliocene inferred from the Lake El'gygytgyn pollen record
Global and Planetary Change,
186
2020
ISSN: 09218181
Publisher: Elsevier B.V.
Keywords:▾
Deterioration; Ecosystems; Forestry; Lakes; Mammals, Coniferous forests; Environmental change; Marine isotope stages; Mid-Pliocene; Pollen; Russian Arctic; Vegetation change; Vegetation history, Vegetation, environmental change; fungus; grazing; Pliocene; pollen; vegetation history, Chukchi; Elgygytgyn Lake; Russian Federation, Abies; Fungi; Larix; Mammalia; Picea; Pseudotsuga; Pseudotsuga menziesii; Sphagnum
Abstract: ▾ The 318-m long sediment record from Lake El'gygytgyn, NE Russia situated in the present-day herb tundra zone, provides a unique archive of high Arctic environmental changes since ca 3.6 million years ago (Ma). This paper focuses on pollen-derived vegetation change during the mid-Pliocene Warm Period (mPWP) and in particular during Marine Isotope Stage (MIS) M2, which is known to represent the coldest interval of the Pliocene. Building on initial pollen studies, we provide a more complete record and a more detailed discussion of climatically-driven vegetation and environmental changes in the northeastern Russian Arctic, spanning the 203-thousand-year interval between 3.383 and 3.180 Ma ago. Pine-spruce-fir-larch-Douglas fir forests dominated the area around Lake El'gygytgyn between 3.383 and 3.330 Ma (MIS MG4 - MIS MG2). Colder and drier climate caused a decrease of coniferous forests and widespread Sphagnum habitats around the lake between 3.370 and 3.357 Ma. After 3.3 Ma, the presence of spruce, fir and Douglas fir decreased again. A very pronounced cooling took place at the first half of MIS M2 (3.312–3.283 Ma), when treeless tundra- and steppe-like habitats became common in the regional vegetation. Climate conditions were similar or only slightly warmer and wetter to those of the Holocene. Numerous coprophilous fungi spores identified in the MIS M2 pollen samples suggest the presence of grazing mammals around the lake. Larch-pine forests with some spruce started to dominate the area again after ca. 3.282 Ma, thus pointing to a significant climate amelioration during the mPWP. However, the forested area decreased, while herb- and shrub-dominated vegetation spread again during MIS KM6 (especially 3.235–3.223 Ma), suggesting a noticeable climatic deterioration and relatively cold and dry conditions. © 2020 Elsevier B.V.
2392.
A 45 kyr laminae record from the Dead Sea: Implications for basin erosion and floods recurrence
Quaternary Science Reviews,
229
2020
ISSN: 02773791
Publisher: Elsevier Ltd
Keywords:▾
Carbonate minerals; Catchments; Drops; Erosion; Floods; Glacial geology; Lakes; Paleolimnology; Seawater, Aragonite-detritus laminae; Dead sea; Flash flood; Magnitude-frequency; Transport-limited regime, Climate change, basin analysis; climate change; climate effect; erosion; flash flood; flood; flood frequency; historical record; Holocene; Last Glacial; magnitude; marine isotope stage; paleolimnology; sedimentation, Dead Sea
Abstract: ▾ Recording and analyzing how climate change impacts flood recurrence, basin erosion, and sedimentation can improve our understanding of these systems. The aragonite-detritus laminae couplets comprising the lacustrine formations that were deposited in the Dead Sea are considered as faithful monitors of the freshwater supply to the lakes. We count a total of ∼5600 laminae couplets deposited in the last 45 kyr (MIS3-MIS1) at the Dead Sea center, which encompass the upper 142 m of the ICDP Core 5017-1. The present study shows that aragonite and detritus laminae are thinner and occur at high frequency during MIS 3-2, while they are much thicker and less frequent during MIS 1. By analyzing multiple climate-connected factors, we propose that significant lake-level drops, enhanced dust input, and low vegetative cover in the drainage basin during the last deglaciation (22-11.6 ka) have considerably increased erodible materials in the Dead Sea watershed. We find a decoupling existed between the significant lake-level drop/lake size reduction and lamina thickness change during the last deglaciation. We argue that during the Last Glacial and the Holocene, the variation of lamina thickness at the multiple-millennium scale was not controlled directly by the lake-level/size change. We interpret this decoupling implying the transport capacity of flash-floods is low and might be saturated by the oversupply of erodible materials, and indicating a transport-limited regime during the time period. We suggest the observed thickness and frequency distribution of aragonite-detritus laminae points to the high frequency of small-magnitude floods during the Last Glacial, in contrast to low frequency, but large-magnitude floods during the Holocene. © 2019 Elsevier Ltd
2391.
Measurement of volume change and mass transfer during serpentinization: Insights from the Oman Drilling Project
Journal of Geophysical Research: Solid Earth,
125
(5)
e2019JB018877
2020
2390.
Composition, Stratigraphy, and Geological History of the Noachian Basement Surrounding the Isidis Impact Basin
Journal of Geophysical Research: Planets,
125
(7)
2020
Abstract: ▾ The western part of the Isidis basin structure hosts a well-characterized Early Noachian to Amazonian stratigraphy. The Noachian Basement comprises its oldest exposed rocks (Early to Mid-Noachian) and was previously considered a single low-Ca pyroxenes (LCP)- and Fe/Mg-smectite-bearing unit. Here, we divide the Noachian Basement Group into five distinct geological units (Stratified Basement Unit, Blue Fractured Unit, Mixed Lithology Plains Unit, LCP-bearing Plateaus Unit, and Fe/Mg-smectite-bearing Mounds Unit), two geomorphological features (megabreccia and ridges), and a mineral deposit (kaolinite-bearing bright materials), based on geomorphology, spectral characteristics, and stratigraphic relationships. Megabreccia contain four different pre-Isidis lithologies, possibly including deeper crust or mantle materials, formed through mass wasting associated with transient crater collapse during Isidis basin formation. The Fe/Mg-smectite-bearing Stratified Basement Unit and LCP-bearing Blue Fractured Unit likewise represent pre-Isidis units within the Noachian Basement Group. Multiple Fe/Mg-smectite-bearing geological units with different stratigraphic positions and younger kaolinite-bearing bright materials indicate several aqueous alteration episodes of different ages and styles. Units with slight changes in pyroxene spectral properties suggest a transition from low-Ca pyroxene-containing materials to those with higher proportions of pyroxenes higher in Ca and/or glass that could be related to different impact and/or igneous processes, or provenance. This long history of Noachian and potentially Pre-Noachian geological processes, including impact basin formation, aqueous alteration, and multiple igneous and sedimentary petrogeneses, records changing ancient Mars environmental conditions. All units defined by this study are available 20 km outside of Jezero crater for in situ analysis and sampling during a potential extended mission scenario for the Mars 2020 rover. ©2020. The Authors.
2389.
Borehole research in New York State can advance utilization of low-enthalpy geothermal energy, management of potential risks, and understanding of deep sedimentary and crystalline geologic systems
Scientific Drilling,
2875-91
2020
ISSN: 18168957
Publisher: Copernicus GmbH
Keywords:▾
Boring; Decision making; Geothermal fields; Groundwater; Hydrogeology; Infill drilling, Complex relationships; Continental scientific drillings; Discontinuous rock mass; Intraplate seismicity; Mechanical working; Subsurface characterizations; Subsurface research; U.S. Department of Energy, Exploratory boreholes
Abstract: ▾ In January 2020, a scientific borehole planning workshop sponsored by the International Continental Scientific Drilling Program was convened at Cornell University in the northeastern United States. Cornell is planning to drill test wells to evaluate the potential to use geothermal heat from depths in the range of 2700-4500 m and rock temperatures of about 60 to 120 °C to heat its campus buildings. Cornell encourages the Earth sciences community to envision how these boreholes can also be used to advance high-priority subsurface research questions. Because nearly all scientific boreholes on the continents are targeted to examine iconic situations, there are large gaps in understanding of the "average" intraplate continental crust. Hence, there is uncommon and widely applicable value to boring and investigating a "boring" location. The workshop focused on designing projects to investigate the coupled thermal-chemical-hydrological-mechanical workings of continental crust. Connecting the practical and scientific goals of the boreholes are a set of currently unanswered questions that have a common root: the complex relationships among pore pressure, stress, and strain in a heterogeneous and discontinuous rock mass across conditions spanning from natural to human perturbations and short to long timescales. The need for data and subsurface characterization vital for decision-making around the prospective Cornell geothermal system provides opportunities for experimentation, measurement, and sampling that might lead to major advances in the understanding of hydrogeology, intraplate seismicity, and fluid/chemical cycling. Subsurface samples could also enable regional geological studies and geobiology research. Following the workshop, the U.S. Department of Energy awarded funds for a first exploratory borehole, whose proposed design and research plan rely extensively on the ICDP workshop recommendations. © 2020 Copernicus GmbH. All rights reserved.
2388.
Brittle deformation of carbonated peridotite—Insights from listvenites of the Samail ophiolite (Oman Drilling Project Hole BT1B)
Journal of Geophysical Research: Solid Earth,
125
(10)
e2020JB020199
2020
2387.
Central uplift collapse in acoustically fluidized granular targets: Insights from analog modeling
Meteoritics and Planetary Science,
55
(2)
441-456
2020
Abstract: ▾ Depending on their sizes, impact craters have either simple or complex geometries. Peak-ring craters such as the Chicxulub impact structure possess a single interior ring of peaks and hills and a flat interior floor. The exact mechanisms leading to the formation of a morphological peak-ring are still a matter of debate. In this study, analog modeling was used to study the flow field of a collapsing central uplift. A 3-D-printed cast was used to bring the analog material in the shape of an overheightened central uplift that was based on numerical modeling. The cast was then quickly removed and the central peak collapsed, forming a flattened broad mound that spread out onto the annular moat of the crater cavity. A subwoofer was used to fluidize the granular target material. The kinematics of the collapse were analyzed with the aid of particle image velocimetry, revealing a downward and outward collapse of the central uplift. This mode of collapse is partly in agreement with numerical models, in particular for the initial and middle phases. The overthrusting of the collapsing central peak onto the inward moving crater floor predicted by numerical modeling was observed, though to a lesser degree. A peak-ring, however, could not be reproduced since the collapse came to a halt before the central peak was completely leveled. Nevertheless, the method provides qualitative insights into the kinematics of collapse phenomena. This experimental study provides independent support of the theory of acoustic fluidization, in addition to numerical simulations. © 2020 The Authors. Meteoritics & Planetary Science published by Wiley Periodicals, Inc. on behalf of The Meteoritical Society (MET)
2386.
Characterization of shocked quartz grains from Chicxulub peak ring granites and shock pressure estimates
Meteoritics and Planetary Science,
55
(10)
2206-2223
2020
Abstract: ▾ Planar deformation features (PDFs) in quartz are a commonly used and well-documented indicator of shock metamorphism in terrestrial rocks. The measurement of PDF orientations provides constraints on the shock pressure experienced by a rock sample. A total of 963 PDF sets were measured in 352 quartz grains in 11 granite samples from the basement of the Chicxulub impact structure’s peak ring (IODP-ICDP Expedition 364 drill core), with the aim to quantify the shock pressure distribution and a possible decay of the recorded shock pressure with depth, in the attempt to better constrain shock wave propagation and attenuation within a peak ring. The investigated quartz grains are highly shocked (99.8% are shocked), with an average of 2.8 PDF sets per grain; this is significantly higher than in all previously investigated drill cores recovered from Chicxulub and also for most K-Pg boundary samples (for which shocked quartz data are available). PDF orientations are roughly homogenous from a sample to another sample and mainly parallel to {10 (Formula presented.) 3} and {10 (Formula presented.) 4} orientations (these two orientations representing on average 68.6% of the total), then to {10 (Formula presented.) 2} orientation, known to form at higher shock pressure. Our shock pressure estimates are within a narrow range, between ~16 and 18 GPa, with a slight shock attenuation with increasing depth in the drill core. The relatively high shock pressure estimates, coupled with the rare occurrence of basal PDFs, i.e., parallel to the (0001) orientation, suggest that the granite basement in the peak ring could be one of the sources of the shocked quartz grains found in the most distal K-Pg boundary sites. © 2020 The Authors. Meteoritics & Planetary Science published by Wiley Periodicals LLC on behalf of The Meteoritical Society (MET)
2385.
Characterizing subseismic faults from SK-2 drilling core (2900-4200 m): Implication for reservoir transmissibility and regional tectonic evolution
Interpretation,
8
(2)
2020
ISSN: 23248858
Publisher: Society of Exploration Geophysicists
Keywords:▾
China; Songliao Basin; borehole; fault zone; gas flow; gas well; hydrocarbon migration; hydrocarbon resource; oil well; petroleum hydrocarbon; reservoir characterization; seismic reflection; tectonic evolution; tectonic setting; well logging
Abstract: ▾ Undiscernible faults on seismic reflection profiles are referred to as subseismic faults. Although most subseismic faults are undetected, they play a significant role in understanding regional tectonic evolution and can influence the flow of oil and gas. The Songliao Basin in NE China is a typical Meso-Cenozoic continental petroliferous basin characterized by stable sedimentation, rift-depression dual structure, and large-scale oil and gas production. However, the characteristics of subseismic faults and their effect on petroleum resources remain not well understood. Here we reported findings from the SK-2 east borehole located in the Songliao Basin, which is the deepest (7018 m deep below ground surface) continental scientific drilling borehole in East Asia. We identified 46 subseismic faults at 2900-4200 m depth based on observations of core- scanning images, macro- and micro-structures, and well-logging data. Macro- and micro-structural analyses indicate that most of the subseismic faults in the borehole show normal slip. These observations suggest these subseismic faults may form in response to regional extension in the Shahezi (K1sh) period. The cross-cutting relationships among several groups of sheared fault planes or elongated veins filled in the fractures likely reflect multi-stage faulting. The subseismic faults are considered to be related to the nearby larger-scale faulting as interpreted on the seismic profile. Spatial correlation between the observed subseismic faults and elevated hydrocarbon concentrations documented by borehole mud gas logging suggests that the subseismic faults might have controlled gas migration in the study area. © 2020 Society of Exploration Geophysicists and American Association of Petroleum Geologists.
2384.
Climatic control on magnetic mineralogy during the late MIS 6 - Early MIS 3 in Lake Chalco, central Mexico
Quaternary Science Reviews,
230
2020
ISSN: 02773791
Publisher: Elsevier Ltd
Keywords:▾
Glacial geology; Incident solar radiation; Magnetic properties; Magnetism; Minerals; Paleolimnology; Tropics, Climatic oscillations; Climatic variability; Interglacial(s); Magnetic mineralogy; Marine isotopic stages; Multiproxy approach; North America; Pleistocene, Lakes, interglacial; Last Glacial Maximum; Last Interglacial; magnetic property; marine isotope stage; mineralogy; paleoclimate; paleolimnology; Pleistocene; reconstruction; seasonal variation; seasonality, Bolivia; Lake Chalco; Lake Titicaca; Mexico [North America], Bacillariophyta
Abstract: ▾ Sediments from Lake Chalco in central Mexico spanning from ca. 150 to 35 ka ago provide evidence of paleoclimatic variability in the North American tropics associated with the end of Marine Isotopic Stage (MIS) 6, the transition to the last interglacial (MIS 5.5, ca. 130-115 ka ago), and part of the last glacial (MIS 5.4 to early MIS 3, 115 to 35 ka ago). We applied a multiproxy approach based on the analysis of mineral magnetism, diatom assemblages and major elements geochemistry. The reconstructed paleoenvironmental history identify the end of the globally cool MIS 6 as wetter than present, with high lake level, and a subsequent change to drier climates at the onset of the last interglacial (ca. 130 ka). Large amplitude changes in most of the analyzed parameters from ca. 130 to 74 ka are approximately coincident with MIS 5 (130-71 ka). The amplitude of these changes decreases in MIS 4 (71-57 ka) and the early part of MIS 3 (57-35 ka). We proposed that the inferred climatic oscillations follow insolation variations during MIS 6 and part of MIS 5 (150-88 ka). Low summer and spring insolation and lower seasonality inhibited evaporation and favored high lake levels. Conversely, maxima in spring and summer insolation promoted dry conditions and low lake levels. The major wet-cold glacial and dry-warm interglacial relationship found in Lake Titicaca (Bolivia) and Lake Chalco records shows the sensitivity of high altitude tropical sites to climatic variability. © 2020 Elsevier Ltd
2383.
Control of planar fabrics on the development of tensile damage zones under high-speed deformation: An experimental study with granite and gneiss
Journal of Structural Geology,
140
2020
Abstract: ▾ We have investigated the laboratory-scale, high-strain rate tensile failure processes responsible for Mode-I breccia dike formation in impact structures. Brazilian disc experiments with granite (isotropic) and gneiss (foliated) samples were performed on a Split Hopkinson Pressure Bar, equipped with high-speed photography. For the gneiss samples, the gneissic foliation was oriented (θ) at 0, 45 and 90° to the compression direction. Time-series images show the transient states of tensile rupture localization and propagation, leading to in situ fragmentation of the rocks. Granite samples produced a single incipient tensile rupture, accommodating pulverized clasts, whereas the gneisses underwent failure by way of major fracture and a network of secondary tensile fractures, forming large elongate clasts. For gneisses, θ greatly influenced the secondary crack growth, forcing propagation trajectories to orient preferentially either along or across the foliation. The two types of target rocks produced contrasting clast geometry in the fracture zones. The granite had mostly small clasts (<10 mm), with average aspect ratios around 1:2, whereas the gneisses produced larger clasts (<40 mm) with aspect ratios, 1:5, 1:4 and 1:4 for θ = 0, 45 and 90°, respectively. This study demonstrates that monomict breccia dikes could form in situ, rather than by a tensile dilation followed by infilling. © 2020 Elsevier Ltd
2382.
Astronomically forced variations in multiresolution resistivity logs of lower Upper Cretaceous (Cenomanian-Coniacian) terrestrial formations from the Songliao Basin, northeastern China
Palaeogeography, Palaeoclimatology, Palaeoecology,
555
2020
ISSN: 00310182
Publisher: Elsevier B.V.
Keywords:▾
borehole; Cretaceous; cyclic sedimentation; cyclostratigraphy; organic carbon; paleoclimate, China; Songliao Basin
Abstract: ▾ Continuous and high-resolution well logs from the SK-2 east (SK-2e) borehole in the Songliao Basin provide an opportunity to understand the relationship between astronomically forced climate and electrical responses in terrestrial Cretaceous strata. Here, we present well logs, mud logs, and core measurement data of lacustrine deposits in the Upper Cretaceous Qingshankou Fm and of fluvial/deltaic deposits in the Quantou Fm. The multiresolution resistivity logs used for the cyclostratigraphic analysis include deep laterolog resistivity logs, resistivity image logs, and array induction logs. The results show that the resistivity of strata in Quantou Fm mainly reflects changes in clay content, and that resistivity logs can be used as paleoenvironmental and paleoclimate proxies in cyclostratigraphic studies of the Quantou Fm. For the Qingshankou Fm, formation resistivity is mainly affected by clay minerals, which contribute to the overall electrical conductivity, as well as nonconductive organic carbon. Increasing clay and organic carbon contents usually correspond to wetter and warmer climatic conditions. The phase relationship between resistivity logs and astronomical cyclicity depends on factors that control resistivity. Spectral analyses of lithological changes and resistivity logs indicate the presence of eccentricity, obliquity, and precession cycles throughout the Quantou Fm. This provides strong evidence that climate was the dominant control on cyclic sedimentation in the Quantou Fm. The floating astronomical timescale, which was established by calibrating extracted 405-kyr cycles from resistivity logs, reveals that the duration of Quantou Fm was approximately 5.5 Myr. Comparative analysis of power spectra reveals that the sensitivity of resistivity logs with specific resolutions to Milankovitch cycles with different frequencies is variable. Comprehensive analysis of multiresolution resistivity logs is a new method in cyclostratigraphy analysis that has the potential to be effective in detecting signals of Milankovitch cycles in terrestrial deposits. © 2020 Elsevier B.V.
2381.
Cooling rates of pyroclastic deposits inferred from mineral magnetic investigations: a case study from the Pleistocene Mýtina Maar (Czech Republic)
International Journal of Earth Sciences,
109
(5)
1707 – 1725
2020
ISSN: 14373254
Publisher: Springer
Keywords:▾
Czech Republic; cooling; emplacement; mineral alteration; Pleistocene; pyroclastic deposit; tephra; volcanic eruption
Abstract: ▾ Tephra layers of the Mýtina Maar, Czech Republic, contain ferrimagnetic Mg–Al-rich titanomagnetite, which is suggested to originate from a fractionated alkaline CO2-rich lithospheric mantle melt. We investigated the magnetic mineralogy and Curie temperature (TC) from tephra deposits of two drill cores (< 9 m depth). TC calculated (208 ± 14 °C) from chemical composition (Fe2+0.8Mg0.5Fe3+1.1Al0.3Ti0.3O4) is in accordance with TC retrieved from cooling curves of temperature-dependent magnetic susceptibility measurements (195–232 °C). However, thermomagnetic curves are irreversible either with lower (type I) or higher (type II) TC in the heating curve. All curves show transition temperatures above ca. 390 °C, indicating maghemitization. We interpret the irreversibility of TC (∆TC) in terms of different degrees of cation ordering, overprinted or masked by different degrees of maghemitization, which is a low-temperature phenomenon. Negative ∆TC indicates that original deposited titanomagnetite has cooled faster and, therefore, has stored a lower degree of cation ordering compared to heating/cooling rate of 11 °C/min in the Kappabridge. Type II with positive ∆TC indicates higher degree of cation ordering, and, therefore, slower cooling rate. The central part of this deposit shows most severe maghemitization, indicating rather wet emplacement. We, therefore, suggest different eruption styles for deposition of type I pyroclastics with more phreatomagmatic and type II pyroclastics with more phreato-Strombolian eruption styles. Our study is a new approach to discriminate different cooling histories in maar deposits using the Curie temperature of titanomagnetite. We suggest that this method has the potential to discriminate different emplacement modes resulting from different eruption styles. © 2020, The Author(s).
2380.
Correlation of core and downhole seismic velocities in high-pressure metamorphic rocks: a case study for the COSC-1 borehole, Sweden
Solid Earth,
11
(2)
607--626
2020
ISSN: 1869-9510Abstract: ▾ {\textless}p{\textgreater}{\textless}strong{\textgreater}Abstract.{\textless}/strong{\textgreater} Deeply rooted thrust zones are key features of tectonic processes and the evolution of mountain belts. Exhumed and deeply eroded orogens like the Scandinavian Caledonides allow us to study such systems from the surface. Previous seismic investigations of the Seve Nappe Complex have shown indications of a strong but discontinuous reflectivity of this thrust zone, which is only poorly understood. The correlation of seismic properties measured on borehole cores with surface seismic data can constrain the origin of this reflectivity. To this end, we compare seismic velocities measured on cores to in situ velocities measured in the borehole. For some intervals of the COSC-1 borehole, the core and downhole velocities deviate by up to 2 km s{\textless}span class="inline-formula"{\textgreater}$^{\textrm{−1}}${\textless}/span{\textgreater}. These differences in the core and downhole velocities are most likely the result of microcracks mainly due to depressurization. However, the core and downhole velocities of the intervals with mafic rocks are generally in close agreement. Seismic anisotropy measured in laboratory samples increases from about 5 % to 26 % at depth, correlating with a transition from gneissic to schistose foliation. Thus, metamorphic foliation has a clear expression in seismic anisotropy. These results will aid in the evaluation of core-derived seismic properties of high-grade metamorphic rocks at the COSC-1 borehole and elsewhere.{\textless}/p{\textgreater}
2379.
Deep drilling reveals massive shifts in evolutionary dynamics after formation of ancient ecosystem
Science Advances,
6
(40)
2020
ISSN: 23752548
Publisher: American Association for the Advancement of Science
Keywords:▾
Biodiversity; Biological Evolution; Climate Change; Ecosystem; Fossils; Lakes; Dynamics; Economic and social effects; Lakes; Climate indicators; Ecosystem stability; Empirical data; Endemic species; Evolutionary dynamics; Extinction rates; High resolution; Lake formation; biodiversity; climate change; ecosystem; evolution; fossil; lake; Ecosystems
Abstract: ▾ The scarcity of high-resolution empirical data directly tracking diversity over time limits our understanding of speciation and extinction dynamics and the drivers of rate changes. Here, we analyze a continuous species-level fossil record of endemic diatoms from ancient Lake Ohrid, along with environmental and climate indicator time series since lake formation 1.36 million years (Ma) ago. We show that speciation and extinction rates nearly simultaneously decreased in the environmentally dynamic phase after ecosystem formation and stabilized after deep-water conditions established in Lake Ohrid. As the lake deepens, we also see a switch in the macroevolutionary trade-off, resulting in a transition from a volatile assemblage of short-lived endemic species to a stable community of long-lived species. Our results emphasize the importance of the interplay between environmental/climate change, ecosystem stability, and environmental limits to diversity for diversification processes. The study also provides a new understanding of evolutionary dynamics in long-lived ecosystems. © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).
2378.
Deep Scientific Drilling
Encyclopedia of Earth Sciences Series,
PartF4
2020
2377.
Design and applications of drilling trajectory measurement instrumentation in an ultra-deep borehole based on a fiber-optic gyro
Geoscientific Instrumentation, Methods and Data Systems,
9
(1)
79-104
2020
ISSN: 21930856
Publisher: Copernicus GmbH
Keywords:▾
Boreholes; Bottles; Electromagnetic pulse; Error compensation; Geology; Geothermal wells; Gyroscopes; Hot working; Infill drilling; Structural design; Temperature; Trajectories, Continental scientific drillings; Data measurements; Design and application; Engineering applications; Geological drilling; Temperature field simulation; Trajectory measurements; Working environment, Fiber optics, borehole geophysics; design method; drilling; fiber optics; geological survey; geothermal system; hot dry rock; instrumentation; measurement method; trajectory; well logging
Abstract: ▾ The working environment in hot dry rock boreholes, encountered in deep geothermal investigation drilling and ultra-deep geological drilling (up to 5000 m), is very difficult at the present stage. We have developed a drilling trajectory measuring instrumentation (DTMI), which is based on the interference fiber-optic gyro (FOG). This can work continuously, for 4 h, in an environment where the ambient temperature does not exceed 270 °C and the pressure does not exceed 120MPa. The DTMI is mainly divided into three parts: an external confining tube, a metal vacuum flask, and a FOG measurement probe. Here, we focus on the mechanical design, strength, and pressure field simulation analysis for the external tube, the structural design and temperature field simulation analysis for the vacuum flask, and the FOG Shupe error analysis and compensation in the temperature field. Finally, through the engineering applications of the SK-2 east borehole of the China Continental Scientific Drilling (CCSD) project and the geothermal well of Xingreguan-2, the data measurements of the drilling trajectory were used to analyze the stability of the DTMI. The instrument realizes long-duration, high-stability work in the process of making trajectory measurements in an ultra-deep hole. The instrument has the characteristic of anti-electromagnetic interference and enables work to be carried out in the blind zone of existing technologies and instrumentation. Therefore, DTMI has great potential in the promotion and development of geological drilling technology. © Author(s) 2020.
2376.
Distribution and transport of thermal energy within magma–hydrothermal systems
Geosciences (Switzerland),
10
(6)
1 – 26
2020
2375.
Between plate and salt tectonics—New stratigraphic constraints on the architecture and timing of the Dead Sea basin during the Late Quaternary
Basin Research,
32
(4)
636-651
2020
ISSN: 0950091X
Publisher: Blackwell Publishing Ltd
Keywords:▾
deformation mechanism; neotectonics; plate boundary; plate motion; plate tectonics; Quaternary; salt tectonics; sedimentation rate; seismic reflection; stratigraphy; structural control; structural geology, Dead Sea
Abstract: ▾ The Dead Sea is an extensional basin developing along a transform fault plate boundary. It is also a terminal salt basin. Without knowledge of precise stratigraphy, it is difficult to differentiate between the role of plate and salt tectonics on sedimentary accumulation and deformation patterns. While the environmental conditions responsible for sediment supply are reasonably constrained by previous studies on the lake margins, the current study focuses on deciphering the detailed stratigraphy across the entire northern Dead Sea basin as well as syn and post-depositional processes. The sedimentary architecture of the late Quaternary lacustrine succession was examined by integrating 851 km of seismic reflection data from three surveys with gamma ray and velocity logs and the stratigraphic division from an ICDP borehole cored in 2010. This allowed seismic interpretation to be anchored in time across the entire basin. Key surfaces were mapped based on borehole lithology and a newly constructed synthetic seismogram. Average interval velocities were used to calculate isopach maps and spatial and temporal sedimentation rates. Results show that the Amora Formation was deposited in a pre-existing graben bounded by two N-S trending longitudinal faults. Both faults remained active during deposition of the late Pleistocene Samra and Lisan Formations—the eastern fault continued to bound the basin while the western fault remained blind. On-going plate motion introduced a third longitudinal fault, increasing accommodation space westwards from the onset of deposition of the Samra Formation. During accumulation of these two formations, sedimentation rates were uniform over the lake and similar. High lake levels caused an increase in hydrostatic pressure. This led to salt withdrawal, which flowed to the south and southwest causing increased uplift of the Lisan and En Gedi diapirs and the formation of localized salt rim synclines. This induced local seismicity and slumping, resulting in an increased thickness of the Lisan succession within the lake relative to its margins. Sedimentation rates of the Holocene Ze'elim Fm were 4–5 times higher than before. The analysis presented here resolves central questions of spatial extent and timing of lithology, deposition rates and their variability across the basin, timing of faulting at and below the lake floor, and timing and extent of salt and plate tectonic phases and their effect on syn and post-depositional processes. Plate tectonics dictated the structure of the basin, while salt tectonics and sediment accumulation were primarily responsible for its fill architecture during the timeframe examined here. © 2019 The Authors. Basin Research © 2019 John Wiley & Sons Ltd, European Association of Geoscientists & Engineers and International Association of Sedimentologists
2374.
Assessment of the controls on (234U/238U) activity ratios recorded in detrital lacustrine sediments
Chemical Geology,
550
2020
2373.
Ecological opportunity enabled invertebrate radiations in ancient Lake Ohrid
Journal of Great Lakes Research,
46
(5)
1156 – 1161
2020
ISSN: 03801330
Publisher: International Association of Great Lakes Research
Keywords:▾
Balkans; Lake Ohrid; Invertebrata; Mya; Ecology; Ancient lakes; Buffer capacity; Deep drilling; Environmental change; Evolutionary history; Fresh water lakes; Molecular clock; Molecular phylogeny; adaptive radiation; evolution; invertebrate; lacustrine environment; phylogenetics; phylogeny; Lakes
Abstract: ▾ Ancient Lake Ohrid is the oldest and biologically most diverse freshwater lake in Europe. The recent deep-drilling campaign SCOPSCO provided detailed insights into the lake's limnological history over the past 1.36 my. However, it remains unclear what factors triggered the onset of radiations and whether diversification rates remained constant throughout their evolution. We therefore inferred time-calibrated molecular phylogenies for eight invertebrate groups endemic to Lake Ohrid and performed diversification-rate analyses for the four most species-rich groups. The molecular-clock analyses indicate that few groups possibly originated in springs or rivers in the ‘proto-Balkans’ during the pre-lake phase. The onset of all other radiations, however, can be correlated to one of the three limnological phases in the Ohrid Graben and in Lake Ohrid since 1.9 mya. We therefore assume that the onset of radiations was triggered by an increased ecological opportunity arising from massive environmental changes in the course of the lake deepening. The diversification-rate analyses further indicate that the groups examined diversified with a constant rate. Although the reconstruction of the early evolutionary history of these groups remains challenging, our data suggest that the relatively stable conditions in Lake Ohrid together with its high buffer capacity likely prevented significant changes in diversification rates over time. © 2020 International Association for Great Lakes Research
2372.
A modified Herschel–Bulkley model for rheological properties with temperature response characteristics of poly-sulfonated drilling fluid
Energy Sources, Part A: Recovery, Utilization and Environmental Effects,
42
(12)
1464-1475
2020
ISSN: 15567036
Publisher: Taylor and Francis Inc.
Keywords:▾
Drilling fluids; Infill drilling; Oil wells; Rheology; Viscosity, American Petroleum Institute; Estimation and predictions; Herschel-Bulkley equations; High temperature; Modifying factors; Prediction model; Rheological property; Water based drilling fluids, Shear deformation
Abstract: ▾ In the deep oil and gas drilling operations, estimation and prediction of the rheological properties for a drilling fluid are of crucial importance for precisely hydraulic calculating, cuttings carrying and wellbore stability controlling. Unfortunately, the existing well-known rheological models, such as Bingham Plastic, Power Law, Casson, and Herschel–Bulkley models neglect the effect of temperature on the apparent viscosity of water-based drilling fluid. In this paper, the rheological behavior of the poly-sulfonated drilling fluid applied to the Well SK-2 in Songliao basin, China, within a temperature range of 60–240°C, were experimentally determined using a FANN 50SL rheometer. Results showed that the apparent viscosity decreases with the increase of temperature, especially at the low shear rates. In the whole shear rate range, the rheology curve was divided into two parts. At low shear rates (<170.3 s−1), the Herschel Bulkley model fitted well with the measured data, while at higher shear rates (>170.3 s−1), the Bingham Plastic model got higher precision. Based on the viscosity equation recommended by the American Petroleum Institute, the temperature factor was introduced to modify the Herschel-Bulkley equation, and the apparent viscosity can be successfully predicted compared with the other commonly used rheological models. © 2019, © 2019 Taylor & Francis Group, LLC.
2371.
{Microbial life in the nascent Chicxulub crater}
Geology,
48
(4)
328-332
012020
ISSN: 0091-7613DOI:10.1130/G46799.1
Abstract: ▾ {The Chicxulub crater was formed by an asteroid impact at ca. 66 Ma. The impact is considered to have contributed to the end-Cretaceous mass extinction and reduced productivity in the world’s oceans due to a transient cessation of photosynthesis. Here, biomarker profiles extracted from crater core material reveal exceptional insights into the post-impact upheaval and rapid recovery of microbial life. In the immediate hours to days after the impact, ocean resurge flooded the crater and a subsequent tsunami delivered debris from the surrounding carbonate ramp. Deposited material, including biomarkers diagnostic for land plants, cyanobacteria, and photosynthetic sulfur bacteria, appears to have been mobilized by wave energy from coastal microbial mats. As that energy subsided, days to months later, blooms of unicellular cyanobacteria were fueled by terrigenous nutrients. Approximately 200 k.y. later, the nutrient supply waned and the basin returned to oligotrophic conditions, as evident from N2-fixing cyanobacteria biomarkers. At 1 m.y. after impact, the abundance of photosynthetic sulfur bacteria supported the development of water-column photic zone euxinia within the crater.}
2370.
Magnetite biomineralization in ferruginous waters and early Earth evolution
Earth and Planetary Science Letters,
549
2020
ISSN: 0012821X
Publisher: Elsevier B.V.
Keywords:▾
Greater Sunda Islands; Lake Matano; Lake Towuti; Malili Lakes; South Sulawesi; Sulawesi; Sunda Isles; Biology; Biomineralization; Geologic models; Lakes; Magnetite; Ore reduction; Oxidation; Abiotic pathways; Biological signatures; Earth's surface; Magnetite formation; Mediated reactions; Planetary bodies; Precambrian eons; Seawater chemistry; biomineralization; early Earth; evolution; lacustrine deposit; magnetite; mass spectrometry; oxidation; Precambrian; water column; Iron compounds
Abstract: ▾ Burial of large quantities of magnetite (Fe(II)Fe(III)2O4) in iron formations (IFs) likely contributed to the protracted oxidation of Earth's surface during the Precambrian Eons. Magnetite can form through a diversity of biological and abiotic pathways and its preservation in IFs may thus be variably interpreted as the result of some combination of these processes. Such interpretations give rise to divergent pictures of the Precambrian Earth system and models for its evolution through time. New knowledge on the contribution of specific magnetite formation pathways is, therefore, needed to accurately tether our conceptual and numerical models to the geologic record. To constrain pathways of magnetite formation under ferruginous conditions, we conducted geochemical and multi-method microspectroscopic analyses on particles obtained from the water columns and sediments of ferruginous lakes Matano and Towuti, in Indonesia. We find that biologically reactive Fe(III) mineral phases are reduced in the anoxic waters of both lakes, causing the formation of primary authigenic magnetite, directly in the water column. This water column magnetite often takes conspicuous framboidal forms, which given the link to microbial Fe(III) reduction, may provide a biological signature on early Earth and by extension, other planetary bodies. The consumption of more biologically reactive forms of Fe(III) and the resulting delivery of primary magnetite to underlying sediments promotes the burial of oxidized equivalents and implies that primary magnetite formation could have been a principal pathway of Fe delivery to IFs. Combined, the removal of Fe from Earth's surface through biologically induced magnetite formation and subsequent burial in IFs, suggests that seawater chemistry and the microbially mediated reactions that cause magnetite formation played key roles in Earth system evolution and in setting the pace for planetary oxidation through the Precambrian Eons. © 2020