All ICDP Publications with Abstracts
From parent-sysfolder "Publications" + 2 folder-levels deep
2369.
3D microscopic CT imaging and significance of SK-2 deep mudstone of Shahezi Group; [松科二井深层沙河子组泥岩三维显微CT成像及对深部油气预测的启示]
Geological Bulletin of China,
39
(7)
1006 – 1014
2020
ISSN: 16712552
Publisher: China Geological Survey
Abstract: ▾ In order to deepen the understanding of the vertical change rule of the deep shale gas in the Songke 2 Well, the authors selected the 3500~5700 m section of the Shahezi Formation to carry out the X-ray 3D Computed Tomography (CT) imaging experiment. X-ray CT scan was performed on 19 pieces of 2 cm-diameter columnar cores to obtain non-destructive core scan data, and a three-dimensional image spatial structure with a core resolution of up to 15 μm was established. The pore morphology structure and space of the reconstructed core pore model were analyzed by comparative study of spatial distribution and coordination number, statistics of the vertical distribution of sample porosity and connectivity. This experiment proves that the digital core data have high resolution and rich information. The gray value information reflects different components in the sample. The skeleton and minerals are high gray values, and the pores and cracks are low gray values. Studies have shown that areas with large equivalent pore diameters have high porosity, and areas with large coordination numbers have good connectivity. The vertical distribution of porosity and connectivity is consistent with traditional knowledge and can be verified with logging information. It is believed that the digital core can be used as an important auxiliary method for deep core research in the future. © 2020, Science Press. All right reserved.
2368.
A contribution towards the palynostratigraphical classification of the Middle Pleistocene in Central Europe: The pollen record of the Neualbenreuth Maar, northeastern Bavaria (Germany)
Quaternary Science Reviews,
250
2020
ISSN: 02773791
Publisher: Elsevier Ltd
Keywords:▾
Europe; Climate change; Deterioration; Stratigraphy; Vegetation; Climate deterioration; Marine isotope stages; Middle Pleistocene; Periglacial process; Sedimentary sequence; Sparse representation; Vegetation composition; Vegetation successions; allostratigraphy; Eemian; interglacial; interstadial; paleoecology; palynology; Pleistocene; Pliocene-Pleistocene boundary; Saalian; stratigraphy; Glacial geology
Abstract: ▾ Palaeoecological evidence of intra-Saalian warm stages in Central Europe, which was strongly affected by glacial and periglacial processes during the major Middle and Late Pleistocene cold periods, is ambiguous so far. Recently, the first continuous sedimentary sequence of Central Europe containing the Saalian complex (MIS 8–6) with the Eemian interglacial in stratigraphic superposition was recovered from the newly discovered Neualbenreuth Maar (NE-Bavaria). Here we present palynological results from this record allowing us to critically discuss the available biostratigraphical evidence of alternating intra-Saalian warm-cold intervals from Central Europe. The new pollen record from the Neualbenreuth Maar comprises a continuous record of vegetation and climate changes encompassing four warm stages and five cold periods. The dominance of cold and dry tolerant herbs and the sparse representation of pioneer trees and shrubs during most parts of the sequence indicate open landscapes of steppe to woody-steppe character typical of late Middle and Late Pleistocene glacial periods in Central Europe. The pollen assemblages of the warm stage in the upper part of the core clearly support its correlation with the Eemian interglacial. The three pre-Eemian warm stages represent terrestrial analogues of the marine isotope stages (MIS) 7e, 7c, and 7a. During each of these intervals forests were established, but the reduced abundances and lower diversity of thermophilous and sub-oceanic elements in comparison to the Eemian attest to a weak interglacial character. Each of these interglacials shows a similar vegetation succession and only minor differences in the vegetation composition. The intervening stadial periods represent a strong (MIS 7d) and a moderate (MIS 7b) climate deterioration, respectively. The vegetation and climate succession during the Saalian glacial-interglacial complex of Neualbenreuth is broadly in line with the respective palynological signature from the Velay record (French Massif Central) and the Hoogeveen interstadial (The Netherlands). In contrast, there is only limited correspondence with most pollen records from northern and southern Central Europe, which were hitherto classified as MIS 7. © 2020 Elsevier Ltd
2367.
A discussion on the organic matter enrichment model of the Nenjiang Formation, Songliao Basin: A case study of oil shale in the 1st and 2nd members of the Nenjiang Formation; [松辽盆地嫩江组泥页岩有机质富集模式探讨——以嫩江组一、二段油页岩为例]
Geology in China,
47
(1)
236 – 248
2020
ISSN: 10003657
Publisher: Science Press
Keywords:▾
China; Songliao Basin; enrichment; eutrophication; hydrocarbon exploration; model; oil shale; organic matter; volcanic ash
Abstract: ▾ The formation mechanism of the oil shale developed in the 1st and 2nd members of Nenjiang Formation in Songliao Basin was studied by combining theoretical model with geological data such as total carbon content, sulfur isotope of pyrite, and whole rock element from the Songke-1 Well (south hole). Some conclusions have been reached: (1) It may not be fully correct to attribute the formation of oil shale to seawater intrusion into the lake basin. Although seawater invasion can lead to salinization of the lake and subsequent algae blooming, the change of bottom water redox condition caused by the invasion of oxygen-rich seawater into the bottom lake can inhibit the accumulation and preservation of organic matter in sediments; (2) The impact of seawater transgression on oil shale formation was mainly related to algae blooming caused by the continuous salinization of the lake water after transgression; (3) Volcanic tuff deposits are widely distributed in the Songliao basin and usually associated with oil shale deposits. The increase of productivity in ancient Songliao lake basin was directly related to nutrients such as phosphorus and iron brought by volcanic ash input; (4) The formation of oil shale in the Nenjiang Formation was controlled by a combination of mechanisms such as water eutrophication events induced by instantaneous mass input of volcanic ash and seawater invasion. It is concluded that organic matter enrichment in the oil shale is controlled by both water depth and the influence of sediment input from rivers. © 2020 Editorial Board of Geology in China. All rights reserved.
2366.
A Floating Astronomical Time Scale for the Early Late Cretaceous Continental Strata in the Songliao Basin, Northeastern China
Acta Geologica Sinica (English Edition),
94
(1)
27-37
2020
ISSN: 10009515
Publisher: John Wiley and Sons Inc
Keywords:▾
borehole; Cretaceous; detection method; eccentricity; marine environment; paleoclimate; proxy climate record; terrestrial environment; thorium, China; Songliao Basin
Abstract: ▾ A continuous terrestrial succession was recovered from the Songke-2 (SK-2) borehole in the Songliao Basin, Northeastern China. This borehole provides a unique material for further research on the continental paleoclimate during Cretaceous greenhouse period, following a series of achievements of the Songke-1 (SK-1) core. In this study, thorium (Th) logging data were chosen as a paleoclimate proxy to conduct a detailed cyclostratigraphic analysis. The Th series varies quasi-periodically; power spectra and evolutionary fast Fourier transformation (FFT) analysis reveal significant cycles in the Quantou (K2q), Qingshankou (K2qn), Yaojia (Ky and Nenjiang (K2n) formations. The ratio of cycle wavelengths in these stratigraphic units is approximately 20:5:2:1, corresponding to long orbital eccentricity (405 kyr), short orbital eccentricity (100 kyr), obliquity (37 kyr), and precession cycles (22.5 kyr and 18.4 kyr). The durations of the K2n, K2y, K2qn and K2q are estimated as 6.97, 1.83, 5.30 and 4.52 Myr, respectively, based on the constructed ∼18.62 Myr “floating” astronomical time scale (ATS). Comparison of the durations between the SK-1 s and SK-2 boreholes exhibits a slight difference of 0.06 Myr and 0.459 Myr for K2qn and K2y. Nevertheless, our ATS of K2n supports the chronostratigraphic frame constructed by the CA-ID-TIMS data of the SK-1s borehole. This new “floating” ATS provides precise numerical ages for stratigraphic boundaries, biozones and geological events in the Songliao Basin, and can serve as a basis for correlation of strata and events between marine and terrestrial systems. © 2020 Geological Society of China
2365.
A steeply-inclined trajectory for the Chicxulub impact
Nature Communications,
11
(1)
2020
Abstract: ▾ The environmental severity of large impacts on Earth is influenced by their impact trajectory. Impact direction and angle to the target plane affect the volume and depth of origin of vaporized target, as well as the trajectories of ejected material. The asteroid impact that formed the 66 Ma Chicxulub crater had a profound and catastrophic effect on Earth’s environment, but the impact trajectory is debated. Here we show that impact angle and direction can be diagnosed by asymmetries in the subsurface structure of the Chicxulub crater. Comparison of 3D numerical simulations of Chicxulub-scale impacts with geophysical observations suggests that the Chicxulub crater was formed by a steeply-inclined (45–60° to horizontal) impact from the northeast; several lines of evidence rule out a low angle (<30°) impact. A steeply-inclined impact produces a nearly symmetric distribution of ejected rock and releases more climate-changing gases per impactor mass than either a very shallow or near-vertical impact. © 2020, The Author(s).
2364.
Artificial Water Reservoir-Triggered Earthquakes, with Special Emphasis on Koyna, India
Encyclopedia of Earth Sciences Series,
PartF4
2020
ISSN: 13884360
Publisher: Springer Science and Business Media B.V.
2363.
A unified contactcementation theory for gas hydrate morphology detection and saturation estimation from elastic-wave velocities
Marine and Petroleum Geology,
113
2020
ISSN: 02648172
Publisher: Elsevier Ltd
Keywords:▾
Acoustic logging; Acoustics; Boreholes; Cementing (shafts); Elastic waves; Electric logging; Friction; Gases; Hydration; Morphology; Nuclear magnetic logging; Velocity, Accurate quantifications; Effective medium theories; Elastic wave velocity; Gas hydrate saturations; Hikurangi margin; Hydrate saturation; Reservoir characterization; Unified contact cementation theory, Gas hydrates, detection method; elastic wave; estimation method; gas hydrate; hydrocarbon exploration; hydrocarbon reservoir; morphology; wave velocity
Abstract: ▾ Good knowledge of hydrate morphology and accurate quantification of hydrate saturation are significant for reservoir characterization, resource exploitation and geohazards assessment. Although many of empirical or theoretical models have been developed to detect hydrate morphology and predict hydrate saturation from elastic-wave velocities, they either fail to hold true for complex morphologies or cannot provide accurate hydrate saturation estimate. In this study, we propose a unified contact cementation theory by applying the modified Hashin-Shtrikman upper and lower bounds to an extended cementation theory. By merging the cementation theory and effective medium theory, it can be used to account for four types of hydrate morphologies. Numerical modeling results provide some new insights into effects of normalized thickness of hydrate layer, friction coefficient and effective pressure on elastic-wave velocities for different morphologies, which will be helpful for analyzing the borehole stability and determining optimum production-related strategies. In addition, we propose a hydrate morphology-based inversion method by introducing the ratio of multiple hydrate morphologies from statistical analyses and apply it to the acoustic logs from the Mallik 5L-38 permafrost-related gas hydrate research well in Mackenzie Delta and other three marine wells in Nankai Trough and Hikurangi margin. The velocity-based gas hydrate saturation estimations are in good agreement with those predicted from resistivity log and Nuclear Magnetic Resonance measurement, as well as core data, confirming feasibility and applicability of our theory and inversion method, and indicating its potential in seismic characterization of gas hydrate reservoirs. © 2019 Elsevier Ltd
2362.
Abrupt climate change and its influences on hominin evolution during the early Pleistocene in the Turkana Basin, Kenya
Quaternary Science Reviews,
245
2020
2361.
Acoustic evidence for a broad, hydraulically active damage zone surrounding the Alpine Fault, New Zealand
Tectonophysics,
781
2020
2360.
Alteration progress within the Surtsey hydrothermal system, SW Iceland--A time-lapse petrographic study of cores drilled in 1979 and 2017
Journal of Volcanology and Geothermal Research,
392106754
2020
2359.
An 11 million-year-long record of astronomically forced fluvial-alluvial deposition and paleoclimate change in the Early Cretaceous Songliao synrift basin, China
Palaeogeography, Palaeoclimatology, Palaeoecology,
541
2020
2358.
Analysis of bit balling and application of the balling-preventing drilling fluid in well Songke-2; [钻头泥包原因分析及松科二井防泥包钻井液的应用]
Meitiandizhi Yu Kantan/Coal Geology and Exploration,
48
(5)
254 – 261+268
2020
ISSN: 10011986
Publisher: Science Press
Abstract: ▾ In order to solve the problem of the high mud content and easy hydration and dispersion of the Cretaceous sedimentary strata in well Songke-2, the bit balling is prone to occur in the water-based drilling fluid environment, which affects the drill bit ROP and induces downhole adhesion stuck, the paper combined the core drilling technology of well Songke-2, systematically analyzed of the causes of bit balling generated by the drill bit in the mudstone and water-based drilling fluid environment, provided a basis for the design of the anti-balling of the drill bit and the formulation of the anti-ball in drilling fluid, and proposed a drilling fluid formulation with excellent anti-balling performance. The results show that the mudstone drilled in well Songke-2 had the characteristics of high shale content and easy hydration and viscosity, it is very easy to induce the bit balling caused by the adhesion of cuttings and the mechanical “inlaying” of cuttings. Mechanical adhesion of drill bit and drill structure size, bottom hole hydraulic condition, bit material and surface condition, drilling procedure parameters and drilling fluid performance indicators are closely related. Adjusting the performance of the drilling fluid is an effective way to solve the bit balling problem at the drilling site. According to the technical characteristics of the high-temperature and high-pressure sections in the fourth opening of the well Songke-2,after repeated matching, the drilling fluid composition with excellent high temperature resistance and anti-adhesion performance was obtained. The test results of high temperature inhibition, water loss wall-building and the lubricity show that this drilling fluid has strong inhibition at high temperature(230℃), little water loss and good lubricity, it can solve the bit balling problem of the well Songke-2, effectively avoid the instability of the ROP and the occurrence of sticking stuck, the field application effect is ideal. © Meitiandizhi Yu Kantan/Coal Geology and Exploration 2020.
2357.
Andean drought and glacial retreat tied to Greenland warming during the last glacial period
Nature Communications,
11
(1)
2020
ISSN: 20411723
Publisher: Nature Research
Keywords:▾
Amazon Basin; Andes; Arctic; Greenland; Peru; cordillera; Dansgaard-Oeschger cycle; drought stress; glacier retreat; hydrometeorology; Last Glacial; monsoon; precipitation assessment; seasonality; Arctic; article; deglaciation; drought; evaporation; glacial period; Greenland; Peru; precipitation; sediment; summer; warming
Abstract: ▾ Abrupt warming events recorded in Greenland ice cores known as Dansgaard-Oeschger (DO) interstadials are linked to changes in tropical circulation during the last glacial cycle. Corresponding variations in South American summer monsoon (SASM) strength are documented, most commonly, in isotopic records from speleothems, but less is known about how these changes affected precipitation and Andean glacier mass balance. Here we present a sediment record spanning the last ~50 ka from Lake Junín (Peru) in the tropical Andes that has sufficient chronologic precision to document abrupt climatic events on a centennial-millennial time scale. DO events involved the near-complete disappearance of glaciers below 4700 masl in the eastern Andean cordillera and major reductions in the level of Peru’s second largest lake. Our results reveal the magnitude of the hydroclimatic disruptions in the highest reaches of the Amazon Basin that were caused by a weakening of the SASM during abrupt arctic warming. Accentuated warming in the Arctic could lead to significant reductions in the precipitation-evaporation balance of the southern tropical Andes with deleterious effects on this densely populated region of South America. © 2020, The Author(s).
2356.
Downward remagnetization of a ∼74-m-thick zone in lake sediments from palaeo-Lake Idaho (NW United States) - Locating the Gauss/Matuyama geomagnetic boundary within a dual-polarity zone
Geophysical Journal International,
222
(2)
754-768
2020
ISSN: 0956540X
Publisher: Oxford University Press
Keywords:▾
Basalt; Core drilling; Demagnetization; Gaussian distribution; Geomagnetism; Lakes; Lithology; Magnetite; Magnetization; Minerals, Chemical remanent magnetization; Lacustrine sediments; Microscopic observations; Remanent magnetization; Single components; Snake river plains; Stepwise thermal demagnetization; United States of America, Magnetic polarity, basalt; geomagnetism; lacustrine deposit; magnetic mineral; paleomagnetism; remagnetization; remanent magnetization; titanomagnetite, Idaho; Snake River Plain; United States
Abstract: ▾ Remagnetization is an important issue in palaeomagnetism. Here, we discuss an extraordinarily thick (∼74 m) dual-polarity transition zone between the Gauss and Matuyama Chrons. The studied succession is from a drill core through lacustrine sediments of palaeo-Lake Idaho (Snake River Plain, NW United States of America) that are intercalated with basalt units. We identified detrital Ti-rich titanomagnetite and magnetite in lamellar exsolutions as the main carriers of a primary remanence, likely derived from the basalts that erupted in the Snake River Plain. Stepwise thermal demagnetization revealed a single-component remanent magnetization with reversed and normal polarities above and below the transition zone, respectively. Based on rock-magnetic results, microscopic observations, and previously known events in the evolution of palaeo-Lake Idaho, the reversed-polarity component in the transition zone represents a secondary chemical remanent magnetization caused by magnetic mineral alteration or partial neo-formation of magnetite, in association with strong depletion of the primary detrital magnetic minerals that affected a wide depth range below the level where the remagnetization event occurred. This remagnetization event was most likely related to lake-level lowering and partial desiccation of palaeo-Lake Idaho. Understanding the nature and origin of the remagnetization allows to identify the polarity boundary in the unusual case of a secondary magnetization with reversed polarity produced downward in a sequence to an extraordinary large depth. Based on available age information, the observed reversal represents the Gauss/Matuyama boundary, which provides an important age constraint for palaeoclimatic interpretation of the succession. © 2020 The Author(s) 2020. Published by Oxford University Press on behalf of The Royal Astronomical Society.
2355.
3-D seismic attenuation structure of Long Valley caldera: Looking for melt bodies in the shallow crust
Geophysical Journal International,
220
(3)
1677-1686
2020
ISSN: 0956540X
Publisher: Oxford University Press
Keywords:▾
Landforms, Coda normalization method; Hydrothermal fluids; Hydrothermal system; Long valley caldera; Seismic attenuation; Seismic tomography; Subsurface structures; Vertical component, Earthquakes, caldera; crustal structure; earthquake event; earthquake magnitude; magma; seismic attenuation; seismic data; seismic source; seismicity; seismology; three-dimensional modeling; waveform analysis, California; Long Valley Caldera; United States
Abstract: ▾ Unrest at Long Valley caldera (California) during the past few decades has been attributed to the ascent of hydrothermal fluids or magma recharge. The difference is critical for assessing volcanic hazard. To better constrain subsurface structures in the upper crust and to help distinguish between these two competing hypotheses for the origin of unrest, we model the 3-D seismic attenuation structure because attenuation is particularly sensitive to the presence of melt. We analyse more than 47 000 vertical component waveforms recorded from January 2000 through November 2016 obtained from the Northern California Earthquake Data Center. We then inverted the S-to-coda energy ratios using the coda normalization method and obtained an average Q of 250. Low attenuation anomalies are imaged in the fluid-rich western and eastern areas of the caldera, one of which corresponds to the location of an earthquake swarm that occurred in 2014. From a comparison with other geophysical images (magnetotellurics, seismic tomography) we attribute the high attenuation anomalies to hydrothermal systems. Average to high attenuation values are also observed at Mammoth Mountain (southwest of the caldera), and may also have a hydrothermal origin. A large high attenuation anomaly within the caldera extends from the surface to the depths we can resolve at 9 km. Shallow rocks here are cold and this is where earthquakes occur. Together, these observations imply that the high attenuation region is not imaging a large magma body at shallow depths nor do we image any isolated high attenuation bodies in the upper ≈8 km that would be clear-cut evidence for partially molten bodies such as sills or other magma bodies. © 2019 The Author(s). Published by Oxford University Press on behalf of The Royal Astronomical Society.
2354.
Effect of Perforation Interval Design on Gas Production from the Validated Hydrate-Bearing Deposits with Layered Heterogeneity by Depressurization
Geofluids,
2020
2020
ISSN: 14688115
Publisher: Hindawi Limited
Keywords:▾
bearing capacity; gas hydrate; gas production; gas supply; hydrocarbon reservoir; natural gas; permeability; porosity; reservoir characterization; two-dimensional modeling, Canada
Abstract: ▾ Natural gas hydrate is considered as one of the best potential alternative resource to address the world's energy demand. The available geological data at the Mallik site of Canada indicates the vertical heterogeneities of hydrate reservoir petrophysical properties. According to the logging data and sample analysis results at the Mallik 2L-38 well, a 2D model of geologically descriptive hydrate-bearing sediments was established to investigate the multiphase flow behaviors in hydrate reservoir induced by gas recovery and the effects of perforation interval on gas production performance. Firstly, the constructed model with vertical heterogeneous structures of permeability, porosity, and hydrate saturation was validated by matching the measured data in the Mallik 2007 test. The excessive residual methane in the hydrate reservoir observed in simulated results indicates insufficient gas production efficiency. For more effective methane recovery from a hydrate reservoir, the effect of perforation interval on long-term gas production performance was investigated based on the validated reservoir model. The simulation results suggest that both the location and length of the perforation interval have significant impact on hydrate dissociation behavior, while the gas production performance is mainly affected by the length of the perforation interval. To be specific, an excellent gas release performance is found in situations where the perforation interval is set at the interface between a hydrate reservoir and an underlying water-saturated zone. By increasing the perforation interval lengths of 5 m, 8 m, and 10 m, the gas release volumes from hydrate dissociation and gas production volumes from production wells are increased by 34%, 52%, and 57% and 37%, 58%, and 62%, respectively. © 2020 Yingli Xia et al.
2353.
Identification of gas inflow zones in the COSC-1 borehole (Jämtland, central Sweden) by drilling mud gas monitoring, downhole geophysical logging and drill core analysis
Applied Geochemistry,
114104513
2020
ISSN: 0883-2927Keywords:▾
COSC, Downhole logging, Drilling mud gas analysis, Formation fluids, Natural fractures
Abstract: ▾ On-line monitoring of drilling mud gas was for the first time applied during continuous wireline coring of the COSC-1 borehole (Jämtland, central Sweden) to analyse formation gases and to identify inflow gas zones. Nearly complete gas records were obtained with 3 m depth resolution from 662 m (installation of the separator for gas extraction) to 1709 m and 6 m resolution from 1709 m to 2490 m depth (COSC-1 final depth: 2496 m) for H2, CH4, CO2, and He. Between 662 m and 1400 m, both He and CH4 form broad peaks superimposed by several spike-like features. Zones with gas spikes coincide with high resistivity intervals from dual laterolog (DLL) geophysical borehole logging and show fractures in borehole televiewer (BHTV) images, drill core scans, and visual core inspection. Therefore, we assume gas inflow through open fractures where DLLd/DLLs ratios {\textgreater}1.5 imply the presence of free gas. The correlation between helium and DLLd/DLLs ratios no longer appears at depths greater than {\textasciitilde}1550 m, probably because the formation gases are dissolved in formation fluids at higher pressure. Below 1550 m depth, the He concentration drops significantly, whereas the CH4 concentration remains relatively high and H2 and CO2 reach maximum values. The high amount of H2 and CH4 at depths below 1616 m, from where friction between the casing and the drill string was reported, imply that these gases are most certainly artificially generated at depths below 1616 m and at least partly of artificial origin at shallower depths.
2352.
High-resolution microstructural and compositional analyses of shock deformed apatite from the peak ring of the Chicxulub impact crater
Meteoritics and Planetary Science,
55
(8)
2020
2351.
History of scoria-cone eruptions on the eastern shoulder of the Kenya–Tanzania Rift revealed in the 250-ka sediment record of Lake Chala near Mount Kilimanjaro
Journal of Quaternary Science,
35
(1-2)
245-255
2020
ISSN: 02678179
Publisher: John Wiley and Sons Ltd
DOI:10.1002/jqs.3140
Keywords:▾
geochemistry; historical perspective; lacustrine deposit; tephra; tephrochronology; volcanic eruption; volcanic glass; volcanism, East African Rift; East African Rift; Kenya; Kenya Rift; Kilimanjaro [Tanzania]; Lake Challa; Tanzania
Abstract: ▾ Reconstructions of the timing and frequency of past eruptions are important to assess the propensity for future volcanic activity, yet in volcanic areas such as the East African Rift only piecemeal eruption histories exist. Understanding the volcanic history of scoria-cone fields, where eruptions are often infrequent and deposits strongly weathered, is particularly challenging. Here we reconstruct a history of volcanism from scoria cones situated along the eastern shoulders of the Kenya–Tanzania Rift, using a sequence of tephra (volcanic ash) layers preserved in the ~250-ka sediment record of Lake Chala near Mount Kilimanjaro. Seven visible and two non-visible (crypto-) tephra layers in the Lake Chala sequence are attributed to activity from the Mt Kilimanjaro (northern Tanzania) and the Chyulu Hills (southern Kenya) volcanic fields, on the basis of their glass chemistry, textural characteristics and known eruption chronology. The Lake Chala record of eruptions from scoria cones in the Chyulu Hills volcanic field confirms geological and historical evidence of its recent activity, and provides first-order age estimates for seven previously unknown eruptions. Long and well-resolved sedimentary records such as that of Lake Chala have significant potential for resolving regional eruption chronologies spanning hundreds of thousands of years. © 2019 The Authors. Journal of Quaternary Science Published by John Wiley & Sons Ltd
2350.
Hydrological modelling in desert areas of the eastern Mediterranean
Journal of Hydrology,
587
2020
2349.
Hydrothermal alteration associated with the Chicxulub impact crater upper peak-ring breccias
Earth and Planetary Science Letters,
547
2020
Abstract: ▾ The 66 Ma, ∼180 km Chicxulub impact structure in the northern Yucatán peninsula and southern Gulf of Mexico is the best-preserved large impact crater on Earth with a well-developed peak ring. The most recent drilling campaign took place offshore during the joint International Ocean Discovery Program – International Continental Scientific Drilling Program (IODP–ICDP) Expedition 364 at site M0077A (21.45°N, 89.95°W) and recovered ∼830 m of continuous core. Initial examination revealed that the peak-ring comprises four main lithological units (from the base upwards): crystalline basement granitoid rocks (Unit 4); a thin layer of impact melt rocks (Units 3A and B); melt-bearing breccias (Units 2A–C); and post-impact sedimentary rocks (Unit 1). Preliminary analysis of the drill core indicated that hydrothermal alteration has affected all lithologies and is especially pervasive in the melt-bearing breccias of Unit 2 (721.6 to 617.33 meters below sea floor, mbsf). Here we present the first detailed investigation of hydrothermal alteration within the melt-bearing breccias. Alteration phases are predominantly Fe-Mg clay minerals, zeolites, alkali feldspars, calcite and minor sulfides, sulfates, opal and Fe-Ti oxides. Alteration is especially intense proximal to lithologic contacts, particularly at the base of subunit 2B where there is an abrupt increase in host rock porosity ∼30 m above the impact melt rocks. The pervasiveness of clay minerals and zeolites is attributed to the high amounts of devitrified silicate glass throughout Unit 2. The phases preserved here are consistent with the findings of previous hydrothermal studies in other areas of the Chicxulub structure, and suggest an evolving water-rock system that was alkaline-saline, comparable to seawater-volcanic glass alteration. © 2020 Elsevier B.V.
2348.
Hydrothermal circulation and oil migration at the root of the heterogeneous micro-structure of carbonaceous material in the 2.0 Ga Zaonega Formation, Onega Basin, Russia
Precambrian Research,
343105705
2020
2347.
ICDP workshop on the Lake Tanganyika Scientific Drilling Project: A late Miocene-present record of climate, rifting, and ecosystem evolution from the world's oldest tropical lake
Scientific Drilling,
2753-60
2020
ISSN: 18168957
Publisher: Copernicus GmbH
Keywords:▾
Biology; Climate change; Ecosystems; Forestry; Geochronology; Infill drilling; Tropics, Continental climate; Environmental contexts; Evolutionary process; Global environmental change; Research objectives; Scientific discipline; Scientific drilling; Tropical dry forest, Lakes
Abstract: ▾ The Neogene and Quaternary are characterized by enormous changes in global climate and environments, including global cooling and the establishment of northern high-latitude glaciers. These changes reshaped global ecosystems, including the emergence of tropical dry forests and savannahs that are found in Africa today, which in turn may have influenced the evolution of humans and their ancestors. However, despite decades of research we lack long, continuous, well-resolved records of tropical climate, ecosystem changes, and surface processes necessary to understand their interactions and influences on evolutionary processes. Lake Tanganyika, Africa, contains the most continuous, long continental climate record from the mid-Miocene (∼ 10 Ma) to the present anywhere in the tropics and has long been recognized as a top-priority site for scientific drilling. The lake is surrounded by the Miombo woodlands, part of the largest dry tropical biome on Earth. Lake Tanganyika also harbors incredibly diverse endemic biota and an entirely unexplored deep microbial biosphere, and it provides textbook examples of rift segmentation, fault behavior, and associated surface processes. To evaluate the interdisciplinary scientific opportunities that an ICDP drilling program at Lake Tanganyika could offer, more than 70 scientists representing 12 countries and a variety of scientific disciplines met in Dar es Salaam, Tanzania, in June 2019. The team developed key research objectives in basin evolution, source-to-sink sedimentology, organismal evolution, geomicrobiology, paleoclimatology, paleolimnology, terrestrial paleoecology, paleoanthropology, and geochronology to be addressed through scientific drilling on Lake Tanganyika. They also identified drilling targets and strategies, logistical challenges, and education and capacity building programs to be carried out through the project. Participants concluded that a drilling program at Lake Tanganyika would produce the first continuous Miocene-present record from the tropics, transforming our understanding of global environmental change, the environmental context of human origins in Africa, and providing a detailed window into the dynamics, tempo and mode of biological diversification and adaptive radiations. © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License.
2346.
Impact of fluid-rock interaction on water uptake of the Icelandic crust: Implications for the hydration of the oceanic crust and the subducted water flux
Earth and Planetary Science Letters,
538116210
2020
2345.
Groundwater flow characterization of an ophiolitic hard-rock aquifer from cross-borehole multi-level hydraulic experiments
Journal of Hydrology,
589125152
2020