All ICDP Publications with Abstracts
From parent-sysfolder "Publications" + 2 folder-levels deep
2269.
[en]
Crystalline Disposal R&D at LBNL: FY19 Progress Report. Spent Fuel and Waste Disposition.
Lawrence Berkeley National Laboratory (LBNL),
Berkeley
2019
2268.
New shock microstructures in titanite (CaTiSiO5) from the peak ring of the Chicxulub impact structure, Mexico
Contributions to Mineralogy and Petrology,
174
(5)
2019
Abstract: ▾ Accessory mineral geochronometers such as apatite, baddeleyite, monazite, xenotime and zircon are increasingly being recognized for their ability to preserve diagnostic microstructural evidence of hypervelocity-impact processes. To date, little is known about the response of titanite to shock metamorphism, even though it is a widespread accessory phase and a U–Pb geochronometer. Here we report two new mechanical twin modes in titanite within shocked granitoid from the Chicxulub impact structure, Mexico. Titanite grains in the newly acquired core from the International Ocean Discovery Program Hole M0077A preserve multiple sets of polysynthetic twins, most commonly with composition planes (K1) = ~ { 1 ¯ 11 } , and shear direction (η1) = < 110 > , and less commonly with the mode K1 = {130}, η1 = ~ <522 >. In some grains, {130} deformation bands have formed concurrently with the deformation twins, indicating dislocation slip with Burgers vector b = < 341 > can be active during impact metamorphism. Titanite twins in the modes described here have not been reported from endogenically deformed rocks; we, therefore, propose this newly identified twin form as a result of shock deformation. Formation conditions of the twins have not been experimentally calibrated, and are here empirically constrained by the presence of planar deformation features in quartz (12 ± 5 and ~ 17 ± 5 GPa) and the absence of shock twins in zircon (< 20 GPa). While the lower threshold of titanite twin formation remains poorly constrained, identification of these twins highlight the utility of titanite as a shock indicator over the pressure range between 12 and 17 GPa. Given the challenges to find diagnostic indicators of shock metamorphism to identify both ancient and recent impact evidence on Earth, microstructural analysis of titanite is here demonstrated to provide a new tool for recognizing impact deformation in rocks where other impact evidence may be erased, altered, or did not manifest due to generally low (< 20 GPa) shock pressure. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.
2267.
Vertical distribution characteristics of light hydrocarbon components in Well SK-2 and its implications for deep oil and gas [松科二井轻烃组分垂向分布特征及其对深部油气的指示]
Geology in China,
46
(5)
943-953
2019
ISSN: 10003657
Publisher: Science Press
Abstract: ▾ With the maturation of oil and gas exploration and development in Songliao basin, it is urgent to expand strategic replacement areas for oil and gas storage and production. In this task，deep oil and gas seem to be an important direction. Roof gas logging with continuous sampling in the whole well section of Well SK-2 obtained 6042 groups of light hydrocarbon composition data containing 103 monomers，and fully demonstrated vertical variation characteristics of light hydrocarbon components in the deep part of Well SK-2，which shows obvious segmentation. As a whole, it can be divided into 6 sections: section I (470-1000 m in well section), which has a small peak area, a small number of peak outfalls, and a low heavy hydrocarbon content, showing the characteristics of shallow and low-mature oil and gas; Section II (well section 1000-2800 m) has a large peak area, a large number of peaks and a high heavy hydrocarbon content. It is a mature type I source rock and a conventional oil and gas section dominated by oil generation; Section III (2800-3320 m in well section) has fewer and scattered peaks, low content of heavy hydrocarbon and no hydrocarbon source rocks, which are characteristic of reservoirs; Section IV (3320- 5940 m in well section) is the upper unconventional gas section of Shahezi Formation, with a large peak area and a large number of peak outputs, high content of heavy hydrocarbon, being Type III source rocks with large thickness in the maturation - over-maturation stage, and sandstone interbeds can form various types of unconventional natural gas, suggesting an important section for future exploration; Section V (5940-6200 m in well section) is the lower part of Shahezi Formation and Huoshiling Formation, and the peak area and peak number of roof gas are scattered within the section which is considered to be in the stage of over-maturation; Section VI (6200-7108 m in well section) is volcanic rock and basement segment, and the peak area and number of peaks are generally low. However, the peak area of top gas in 7000-7100 m well segment shows that the light hydrocarbon parameters are different from those of section V, and it is inferred that there may be gas sources of type II-III organic matter in the deep part. These characteristics show that the vertical distribution of light hydrocarbon components reflects the different characteristics among Jurassic, Cretaceous and the basal formations in oil and gas formation, maturation, gas content and oil and gas sources. The results obtained by the authors reveal the potential of deep unconventional gas resource, and provide an important foundation for Songliao Basin's exploration shift from conventional oil and gas exploration and tight conglomerate gas exploration at the edge of fault depression to deep trough zone for the exploration and expansion of unconventional natural gas. © 2019 Editorial Board of Geology in China. All rights reserved.
2266.
U-Pb memory behavior in Chicxulub's peak ring — Applying U-Pb depth profiling to shocked zircon
Chemical Geology,
525356-367
2019
Abstract: ▾ The zircon U-Pb system is one of the most robust geochronometers, but during an impact event individual crystals can be affected differently by the passage of the shock wave and impact generated heat. Unraveling the potentially complex thermal history recorded by zircon crystals that experienced variable levels of shock and heating, as well as additioanl pre- and post-impact thermal events, has been difficult using classical geochronological methods. The existing high-precision 40Ar/39Ar age constraints for the K-Pg Chicxulub event, and the previous U-Pb dating of the basement rocks from the impact site, make Chicxulub an ideal location to study impact-induced effects on the zircon U-Pb systematics and to evaluate potential 'memory effects' of pre-impact U-Pb signatures preserved within those individual zircon crystals. Recent IODP-ICDP drilling of the Chicxulub impact structure recovered 580 m of uplifted shocked granitoid and 130 m of melt and suevite, providing an unprecedented opportunity to study zircon crystals subjected to a range of shock pressures, thermal, and deformational histories. Zircon morphologies were classified using scanning electron microscopy (SEM) imaging and then samples were depth profiled using laser ablation inductively coupled plasma mass-spectrometry (LA-ICP-MS) to document the range of preserved age domains from rim-to-center within individual crystals. The results show U-Pb ages range from 66 to 472 Ma, which are consistent with both inherited Carboniferous and Late Paleozoic basement ages as well as Pb loss ages in response to the K-Pg impact event. While the bulk of the zircon grains preserve Paleozoic ages, high U (metamict) zones within fractured zircon crystals exhibited an age within uncertainty (66 ± 6.2 Ma) of the impact age (66.038 ± 0.049 Ma), indicating that inherited intragrain U-Pb kinetics and/or hydrothermal fluid flow may have controlled age resetting those zircon crystals rather than impact-induced shock and heating alone. Moreover, the calculated α-decay doses suggest that the zircon crystals experienced Stage 1 or early Stage 2 radiation damage accumulation. Therefore, we suggest that the lowered crystal annealing temperature in crystals that previoulsy experienced radiation damage make the zircon U-Pb clock either more susceptible to the relatively short heat pulse of the impact event, the moderate pressure and temperature conditions in the peak ring, and/or to hot-fluid flow in the long-lasting post impact hydrothermal system. © 2019 Elsevier B.V.
2265.
Scientific drilling of Lake Chalco, Basin of Mexico (MexiDrill)
Scientific Drilling,
261-15
2019
ISSN: 18168957
Publisher: Copernicus GmbH
Keywords:▾
Explosives; Infill drilling; Oceanography; Risk assessment; Surface waters; Volcanoes, Environmental change; Hydrological variability; Intertropical convergence zone; Natural climate variabilities; Paleoclimate reconstruction; Paleoclimate records; Scientific objectives; Sea surface temperature (SST), Tropics
Abstract: ▾ The primary scientific objective of MexiDrill, the Basin of Mexico Drilling Program, is development of a continuous, high-resolution <span classCombining double low line"inline-formula ∼4400kyr lacustrine record of tropical North American environmental change. The field location, in the densely populated, water-stressed Mexico City region gives this record particular societal relevance. A detailed paleoclimate reconstruction from central Mexico will enhance our understanding of long-term natural climate variability in the North American tropics and its relationship with changes at higher latitudes. The site lies at the northern margin of the Intertropical Convergence Zone (ITCZ), where modern precipitation amounts are influenced by sea surface temperatures in the Pacific and Atlantic basins. During the Last Glacial Maximum (LGM), more winter precipitation at the site is hypothesized to have been a consequence of a southward displacement of the mid-latitude westerlies. It thus represents a key spatial node for understanding large-scale hydrological variability of tropical and subtropical North America and is at an altitude (2240 a.s.l.), typical of much of western North America. In addition, its sediments contain a rich record of pre-Holocene volcanic history; knowledge of the magnitude and frequency relationships of the area's explosive volcanic eruptions will improve capacity for risk assessment of future activity. Explosive eruption deposits will also be used to provide the backbone of a robust chronology necessary for full exploitation of the paleoclimate record. Here we report initial results from, and outreach activities of, the 2016 coring campaign. © Author(s) 2019.
2264.
Structural characteristics of Shahezi Formation beneath the Well SK-2 and its periphery: An analysis of logging and seismic data; [松科二井邻域沙河子组含油气地层结构特征-基于测井和地震数据的分析]
Geology in China,
46
(5)
1052 – 1060
2019
ISSN: 10003657
Publisher: Science Press
Abstract: ▾ During implementation of the Deep Continental Scientific Drilling Engineering Project Well SK-2 in Songliao Basin, the most integrated core data of Shahezi Formation was obtained. And 43 abnormal strata of deep shale gas were preliminarily identified, with a cumulative thickness of 102 meters, indicating that Shahezi Formation has good deep energy prospect. For further analysis of oil and gas resources potential of Shahezi Formation in Songliao basin, in this paper, on the basis of previous studies and in combination with well logging, core data of Well SK-2 and the newly acquired 2-d seismic data in the north-south direction crossing Well SK-2, the spatial distribution and sequence characteristics of Shahezi formation in the vicinity of Well SK-2 well were analyzed. At the same time, based on gas abnormal data acquired form logging during drilling, the authors studied logging and seismic responses of oil and gas perspective reservoirs in Shahezi Formation. It is shown that the Shahezi Formation adjacent to Well SK-2 has large thickness but small lateral extension, and hence the authors divided it into 4 stratigraphic sequences based on well logging as well as seismic and core data, i.e., SQ1, SQ2, SQ3 and SQ4. Among the 4 stratigraphic sequences, SQ4 has a better energy prospect. Its lithology is dominated by mudstone and has the characteristics of high porosity and low wave impedance on logging curves, with continuous strong amplitude on seismic section. Impedance inversion section shows the characteristics of large wave impedance alternated with many smaller wave impedances. Thus, the occurrence conditions of deep natural gas resources of Shahezi Formation in this area are revealed. © 2019 Editorial Board of Geology in China. All rights reserved.
2263.
Sediment residence time reveals Holocene shift from climatic to vegetation control on catchment erosion in the Balkans
Global and Planetary Change,
177186-200
2019
ISSN: 09218181
Publisher: Elsevier B.V.
Keywords:▾
Catchments; Erosion; Geomorphology; Glacial geology; Global warming; Isotopes; Lakes; Land use; Nuclear fuels; Organic carbon; Runoff; Sediments; Uranium; Vegetation, Balkan peninsulas; Human impact; Lake Ohrid; Landscape evolutions; Paleoclimates; Residence time; Soil systems; Tephrochronology; Uranium isotopes, Soils, catchment; detrital deposit; geomorphology; global warming; Holocene; landscape evolution; organic carbon; residence time; sediment analysis; soil erosion; tephrochronology; uranium isotope; vegetation cover; weathering rate, Albania; Balkans; Greece; Lake Ohrid; Macedonia [Greece]
Abstract: ▾ Understanding the evolution of soil systems on geological time scales has become fundamentally important to predict future landscape development in light of rapid global warming and intensifying anthropogenic impact. Here, we use an innovative uranium isotope-based technique combined with organic carbon isotopes and elemental ratios of sediments from Lake Ohrid (North Macedonia/Albania) to reconstruct soil system evolution in the lake's catchment during the last ~16,000 cal yr BP. Uranium isotopes are used to estimated the paleo-sediment residence time, defined as the time elapsed between formation of silt and clay sized detrital matter and final deposition. The chronology is based on new cryptotephra layers identified in the sediment sequence. The isotope and elemental data are compared to sedimentary properties and pollen from the same sample material to provide a better understanding of past catchment erosion and landscape evolution in the light of climate forcing, vegetation development, and anthropogenic land use. During the Late Glacial and the Early Holocene, when wide parts of the catchment were covered by open vegetation, wetter climates promoted the mobilisation of detrital matter with a short paleo-sediment residence time. This is explained by erosion of deeper parts of the weathering horizon from thin soils. Detrital matter with a longer paleo-sediment residence time, illustrating shallow erosion of thicker soils is deposited in drier climates. The coupling between climatic variations and soil erosion terminates at the Early to Mid-Holocene transition as evidenced by a pronounced shift in uranium isotope ratios indicating that catchment erosion is dominated by shallow erosion of thick soils only. This shift suggests a threshold is crossed in hillslope erosion, possibly as a result of a major change in vegetation cover preventing deep erosion of thin soils at higher elevation. The threshold in catchment erosion is not mirrored by soil development over time, which gradually increases in response to Late Glacial to Holocene warming until human land use during the Late Holocene promotes reduced soil development and soil degradation. Overall, we observe that soil system evolution is progressively controlled by climatic, vegetation, and eventually by human land use over the last ~16,000 years. © 2019 Elsevier B.V.
2262.
Seismic clustering in the Sea of Marmara: Implications for monitoring earthquake processes
Tectonophysics,
768
2019
ISSN: 00401951
Publisher: Elsevier B.V.
Keywords:▾
Faulting, Earthquake dynamics; Earthquake process; Fault segmentation; Metropolitan regions; North Anatolian Fault; Regional earthquakes; Seismicity clusters; Seismicity pattern, Earthquakes, aftershock; cluster analysis; earthquake catalogue; earthquake event; earthquake mechanism; earthquake trigger; fault; foreshock; North Anatolian Fault; seismicity, Gulf of Gemlik; Istanbul [Istanbul (PRV)]; Istanbul [Turkey]; Sea of Marmara; Turkey
Abstract: ▾ Quantifying regional earthquake cluster style is essential for providing a context for studies of seismicity patterns and earthquake interactions. Here, we identify clusters of seismicity in the Sea of Marmara region of the North Anatolian Fault, NW Turkey, using a recently derived high-resolution seismicity catalog and the nearest-neighbor earthquake cluster approach. The detected earthquake clusters are utilized for (1) determining spatial distribution of mainshock and aftershock rates and estimating the proximity to failure on different fault segments, (2) identifying fault sections having earthquake repeaters, and (3) finding areas with enhanced foreshock activity. About 6%, 70% and 24% of the events are identified as foreshocks, mainshocks and aftershocks, respectively, with the largest concentration of aftershocks and foreshocks located along the Western High and the Cinarcik Fault, respectively. The method successfully identifies regions where previous studies reported earthquake repeaters as indicator for fault creep and suggests additional repeater areas in the Gulf of Gemlik. The largest proportion of mainshocks with associated foreshocks and aftershocks are along the Western High and Cinarcik Fault segments, potentially indicating that these segments are closer to failure and have increased susceptibility to seismic triggering. Continuing studies can contribute to monitoring possible preparation phase of a large (M > 7) earthquake in the Marmara region near the Istanbul Metropolitan region. © 2019 Elsevier B.V.
2261.
Seismic depth imaging of sequence boundaries beneath the New Jersey shelf
Marine Geophysical Research,
40
(1)
17-32
2019
ISSN: 00253235
Publisher: Springer Netherlands
Keywords:▾
Geologic models; Geophysical prospecting; Groundwater; Groundwater flow; Seismic response; Tomography; Well logging, Complementary data; Geological modeling; Groundwater modelling; Hydrogeological models; Seismic imaging; Seismic reflection survey; Seismic resolution; Two-stage processing, Seismic waves, borehole logging; groundwater flow; imaging method; numerical model; Ocean Drilling Program; seismic data; seismic tomography; seismic velocity, Atlantic Ocean; New Jersey Shelf
Abstract: ▾ Numerical modelling of fluid flow and transport processes relies on a well-constrained geological model, which is usually provided by seismic reflection surveys. In the New Jersey shelf area a large number of 2D seismic profiles provide an extensive database for constructing a reliable geological model. However, for the purpose of modelling groundwater flow, the seismic data need to be depth-converted which is usually accomplished using complementary data from borehole logs. Due to the limited availability of such data in the New Jersey shelf, we propose a two-stage processing strategy with particular emphasis on reflection tomography and pre-stack depth imaging. We apply this workflow to a seismic section crossing the entire New Jersey shelf. Due to the tomography-based velocity modelling, the processing flow does not depend on the availability of borehole logging data. Nonetheless, we validate our results by comparing the migrated depths of selected geological horizons to borehole core data from the IODP expedition 313 drill sites, located at three positions along our seismic line. The comparison yields that in the top 450 m of the migrated section, most of the selected reflectors were positioned with an accuracy close to the seismic resolution limit (≈ 4 m) for that data. For deeper layers the accuracy still remains within one seismic wavelength for the majority of the tested horizons. These results demonstrate that the processed seismic data provide a reliable basis for constructing a hydrogeological model. Furthermore, the proposed workflow can be applied to other seismic profiles in the New Jersey shelf, which will lead to an even better constrained model. © 2018, Springer Science+Business Media B.V., part of Springer Nature.
2260.
Seismic Velocity Estimation Using Passive Downhole Distributed Acoustic Sensing Records: Examples From the San Andreas Fault Observatory at Depth
Journal of Geophysical Research: Solid Earth,
124
(7)
6931-6948
2019
ISSN: 21699313
Publisher: Blackwell Publishing Ltd
Keywords:▾
acoustic survey; borehole geophysics; estimation method; geophone; P-wave; S-wave; San Andreas Fault; seismic velocity, California; San Andreas; United States
Abstract: ▾ Structural imaging and event location require an accurate estimation of the seismic velocity. However, active seismic surveys used to estimate it are expensive and time-consuming. During the last decade, fiber-optic-based distributed acoustic sensing has emerged as a reliable, enduring, and high-resolution seismic sensing technology. We show how downhole distributed acoustic sensing passive records from the San Andreas Fault Observatory at Depth can be used for seismic velocity estimation. Using data recorded from earthquakes propagating near-vertically, we compute seismic velocities using first-break picking as well as slant stack decomposition. This methodology allows for the estimation of both P and S wave velocity models. We also use records of the ambient seismic field for interferometry and P wave velocity model extraction. Results are compared to a regional model obtained from surface seismic as well as a conventional downhole geophone survey. We find that using recorded earthquakes, we obtain the highest P wave model resolution. In addition, it is the only method that allows for S wave velocity estimation. Computed P and S models unravel three distinct areas at the depth range of 50-750 m, which were not present in the regional model. In addition, we find high VP/VS values near the surface and a possible VP/VS anomaly about 500 m deep. We confirm its existence by observing a strong S-P mode conversion at that depth. ©2019. American Geophysical Union. All Rights Reserved.
2259.
Slow strain release along the eastern Marmara region offshore Istanbul in conjunction with enhanced local seismic moment release
Earth and Planetary Science Letters,
510209 – 218
2019
ISSN: 0012821X
Publisher: Elsevier B.V.
Keywords:▾
Armutlu Peninsula; Istanbul [Istanbul (PRV)]; Istanbul [Turkey]; Sea of Marmara; Turkey; Earthquakes; Offshore oil well production; Sea level; Strain measurement; Transform faults; Sea of Marmara; Seismic hazards; slow slip; Strain transients; Strain-meter; amplitude; earthquake event; earthquake rupture; fault slip; seismic hazard; strain; stress; transform fault; Fault slips
Abstract: ▾ We analyze a large transient strainmeter signal recorded at 62.5 m depth along the southern shore of the eastern Sea of Marmara region in northwestern Turkey. This region represents a passage of stress transfer from the Izmit rupture to the Marmara seismic gap. The strain signal was recorded at the Esenkoy site by one of the ICDP-GONAF (International Continental Drilling Programme – Geophysical Observatory at the North Anatolian Fault) strainmeters on the Armutlu peninsula with a maximum amplitude of 5 microstrain and lasting about 50 days. The onset of the strain signal coincided with the origin time of a M W 4.4 earthquake offshore Yalova, which occurred as part of a seismic sequence including eight M W ≥3.5 earthquakes. The M W 4.4 event occurred at a distance of about 30 km from Esenkoy on June 25th 2016 representing the largest earthquake in this region since 2008. Before the event, the maximum horizontal strain was subparallel to the regional maximum horizontal stress derived from stress inversion of local seismicity. During the strain transient, we observe a clockwise rotation in the local horizontal strain field of about 20°. The strain signal does not correlate with known environmental parameters such as annual changes of sea level, rainfall or temperature. The strain signal could indicate local slow slip on the Cinarcik fault and thus a transfer of stress to the eastern Marmara seismic gap. © 2019 Elsevier B.V.
2258.
Spatial and temporal reconstruction of the late Quaternary Dead Sea sedimentary facies from geophysical properties
Journal of Applied Geophysics,
16015-27
2019
ISSN: 09269851
Publisher: Elsevier B.V.
Keywords:▾
Boreholes; Boring; Gamma rays; Geophysics; Glacial geology; Infill drilling; Lakes; Lithology; Sandstone; Sodium chloride; Stratigraphy; Well logging, Dead sea basins; Downholes; Geophysical properties; ICDP; Petrophysical properties; Sedimentary structure; Stratigraphic architecture; Well logs, Sedimentology, facies analysis; lacustrine deposit; lithofacies; lithology; mudstone; Quaternary; reconstruction; sediment core; sedimentary sequence; sedimentary structure; siltstone; spatial analysis; temporal analysis; well logging, Dead Sea
Abstract: ▾ The sedimentary sequences that accumulated within various lakes that occupied the Dead Sea Basin since the Pliocene, contain a detailed record of the climate and tectonic history of the area. Until recently, most of the information about these paleo-lakes was derived from exposures along the marginal terraces of the current Dead Sea (lake), focusing mainly on the last Glacial Lake Lisan and the Holocene-modern Dead Sea. The International Continental Drilling Program (ICDP) recovered a series of cores in the northern Dead Sea Basin, both in the deep depocenter (300 m water depth) and in shallower waters near the current shore. Here, we present downhole logging measurements that were used to provide continuous records of petrophysical properties at depth and to reconstruct lithological profiles. The study highlights how logging data can overcome gaps in drilled-core recovery and be used to examine subsurface geology on a regional scale. Gamma ray, resistivity and velocity wire logs were examined to infer a log-derived lithofacies. The reconstructed profiles presented in this study constitute a first attempt to link deep central settings of the basin with marginal sedimentary sequences. Three main facies were identified in the boreholes including: (Bartov et al., 2002) Finely laminated sequences of mudstones interbedded with siltstones to sandstones; (Bartov et al., 2003) Medium to thick bedded mudstone to sandstone: and (Bartov et al., 2007) Evaporites (e.g. halite and gypsum with some intervals of detrital sediments). The formations that were previously defined along the marginal terraces of the Dead Sea: the Holocene Ze'elim Formation, the last Glacial Lisan Formation, the last interglacial Samra Formation and the early to mid-Pleistocene Amora Formation are identified in the boreholes. A spatial correlation is established providing the stratigraphic architecture of the sedimentary structure beneath the Dead Sea during the late Quaternary. This paper combines geophysical and lithological data and provides the base for subsequent studies on facies interpretation. © 2018 Elsevier B.V.
2257.
SUSTAIN drilling at Surtsey volcano, Iceland, tracks hydrothermal and microbiological interactions in basalt 50 years after eruption
Scientific Drilling,
2535-46
2019
ISSN: 18168957
Publisher: Copernicus GmbH
Keywords:▾
Boreholes; Boring; Geomagnetism; Infill drilling; Volcanoes, Azimuthal direction; Circulating fluids; Continental scientific drillings; Drilling operation; Effusive eruptions; Hydrothermal fluids; Microbial contamination; Vertical borehole, Core drilling
Abstract: ▾ The 2017 Surtsey Underwater volcanic System for Thermophiles, Alteration processes and INnovative concretes (SUSTAIN) drilling project at Surtsey volcano, sponsored in part by the International Continental Scientific Drilling Program (ICDP), provides precise observations of the hydrothermal, geochemical, geomagnetic, and microbiological changes that have occurred in basaltic tephra and minor intrusions since explosive and effusive eruptions produced the oceanic island in 1963-1967. Two vertically cored boreholes, to 152 and 192m below the surface, were drilled using filtered, UV-sterilized seawater circulating fluid to minimize microbial contamination. These cores parallel a 181m core drilled in 1979. Introductory investigations indicate changes in material properties and whole-rock compositions over the past 38 years. A Surtsey subsurface observatory installed to 181m in one vertical borehole holds incubation experiments that monitor in situ mineralogical and microbial alteration processes at 25-124 °C. A third cored borehole, inclined 55° in a 264° azimuthal direction to 354m measured depth, provides further insights into eruption processes, including the presence of a diatreme that extends at least 100m into the seafloor beneath the Surtur crater. The SUSTAIN project provides the first time-lapse drilling record into a very young oceanic basaltic volcano over a range of temperatures, 25-141 °C from 1979 to 2017, and subaerial and submarine hydrothermal fluid compositions. Rigorous procedures undertaken during the drilling operation protected the sensitive environment of the Surtsey Natural Preserve. © Author(s) 2019.
2256.
The utilization of integrated geophysical profiles to reveal the basement geology and geophysical characteristics of the Songliao Basin: A case study of the profile of Well SK-2; [综合物探剖面揭示松辽盆地基底地质与地球物理特征-以过松科二井剖面为例]
Geology in China,
46
(5)
1126 – 1136
2019
ISSN: 10003657
Publisher: Science Press
Abstract: ▾ 收稿日期：2019-04-03；改回日期：2019-09-16 基金项目：中国地质调查局地质调查项目（DD20160207）；国家重点研发专项（2017YFC0601305）及国家自然科学基金青年科学基金项目(41504076)联合资助。作者简介：王天琪，女，1994年生，硕士生，主要从事综合地球物理调查研究工作；E-mail：641149482 @qq.com。通讯作者：韩江涛，男，1982年生，副教授，主要从事深部地球物理勘查工作；E-mail：hanjt@jlu.edu.cn。Abstract: Songliao Basin is a Meso-Cenozoic continental sedimentary basin in Northeast China. Based on a detailed analysis of the Paleozoic stratigraphic characteristics, sedimentary environment and tectonic evolution in Northeast China, the authors conducted the interpretation of the comprehensive geophysical data across Well SK- 2 to investigate the properties and geophysical characteristics of the basement in this paper. On the SN profile, the authors have found some phenomena: the Bouguer gravity anomaly in Well SK-2 is high in the middle and low on both sides; the magnetic anomaly shows a negative correlation with gravity anomaly; magnetotelluric properties are characterized by partial layers and high-low resistance crossover in the shallow part and partial regions in the deep part. On the EW profile, the gravity anomaly curve has the trend high in the west and low in the east; the magnetic anomaly curve is“bowl-shaped”; there exists a high resistance structure compared with features of the SN-trending profile. Combining geophysical characteristics with lithofacies palaeogeography, the authors have reached the following conclusions: 1. From the Late Carboniferous to Late Permian in the Upper Paleozoic, there were many sedimentary environments such as shallow marine facies, continental facies, rivers and lakes. The corresponding lithologic combinations had different physical characteristics; 2. The geomagnetic characteristics of the gravity, magnetic method and magnetotelluric sounding's results reveal that the basement of the study area is mainly composed of mudstone, marble and intrusive rocks, and the burial depth of the roof of the basement is about 7km. The base of the study area is formed by the Upper Paleozoic and intrusive rocks. 3. The location and orientation of the Binzhou fault zone, the Sunwu-Shuangliao fault zone, the Helen-Renmin fault zone and the deep fault system are identified. The fault structures are mainly dominated by SN and EW trending structures. They are important components of the Paleozoic structural skeleton and control the migration and storage of deep oil and gas. © 2019 Editorial Board of Geology in China. All rights reserved.
2255.
Tephra geochemistry from Lake Ohrid (Macedonia/Albania) sediment core ICDP5045-1
PANGAEA
2019
Abstract: ▾ Geochemical finger print data (in wt. {%}) of individual glass shards from 3 three previously described cryptotephra layer in the Late Glacial to Holocene sediments of the DEEP site sequence. FeO? is reported for both Fe${^2}$? and Fe${^3}$? (University of Cologne, Germany , University of Pisa, Italy).
2254.
The evolution of latitudinal temperature gradients from the latest Cretaceous through the Present
Earth-Science Reviews,
189147-158
2019
ISSN: 00128252
Publisher: Elsevier B.V.
Keywords:▾
climate variation; Cretaceous; glacial-interglacial cycle; greenhouse gas; Oligocene; paleoceanography; Paleocene-Eocene boundary; paleoclimate; Pliocene; temperature gradient; thermometry, Animalia
Abstract: ▾ Latitudinal temperature gradients are a defining characteristic of the climate system. Using thermometric indicators, including δ18O, plant and animal fossils, glycerol dialkyl glycerol tetraether (GDGT) proxies, and clumped isotope estimates, we document marine and terrestrial temperature gradients for the latest Cretaceous, Late Paleocene-Early Eocene, Early Oligocene, Pliocene, and Recent. The changes in gradients reflect the transition greenhouse to icehouse conditions. The evolution of latitudinal temperature gradients in marine and terrestrial realms are similar but has some distinctive differences. Marine temperatures are generally warmer than those on land. Except for the Late Paleocene-Early Eocene, the marine records show distinct inflection points at ~30° and ~50° latitude indicating the existence of frontal systems in the ocean. Except for the Late Paleocene-Early Eocene, the marine records show an increasingly steeper trend, from latest Cretaceous through Recent, being most pronounced after the Early Oligocene greenhouse-icehouse transition. This trend reflects the increasing intensity of high-latitude and polar cooling as the icehouse state developed. During the Late Paleocene-Early Eocene the oceans were characterized by slightly warmer tropics and much warmer higher latitudes than at present. The continents have generally had tropical temperatures like those of today, varying by <5 °C. Higher latitude temperatures cooled during the latest Cretaceous, became much warmer during the Late Paleocene-Early Eocene, then cooled during the Early Oligocene and have become increasingly colder since then. The results suggest that there is a climate thermostat mechanism, probably related to greenhouse gas concentrations, that ameliorates tropical warming by redistributing warmth to the poles in the greenhouse world. That mechanism broke down as greenhouse gas concentrations declined resulting in the conversion from greenhouse to icehouse conditions. © 2019 Elsevier B.V.
2253.
The first day of the Cenozoic
Proceedings of the National Academy of Sciences of the United States of America,
116
(39)
19342-19351
2019
Abstract: ▾ Highly expanded Cretaceous-Paleogene (K-Pg) boundary section from the Chicxulub peak ring, recovered by International Ocean Discovery Program (IODP)-International Continental Scientific Drilling Program (ICDP) Expedition 364, provides an unprecedented window into the immediate aftermath of the impact. Site M0077 includes ∼130 m of impact melt rock and suevite deposited the first day of the Cenozoic covered by <1 m of micrite-rich carbonate deposited over subsequent weeks to years. We present an interpreted series of events based on analyses of these drill cores. Within minutes of the impact, centrally uplifted basement rock collapsed outward to forma peak ring capped in melt rock. Within tens of minutes, the peak ring was covered in ∼40 m of brecciated impact melt rock and coarsegrained suevite, including clasts possibly generated by melt-water interactions during ocean resurge. Within an hour, resurge crested the peak ring, depositing a 10-m-thick layer of suevite with increased particle roundness and sorting.Within hours, the full resurge deposit formed through settling and seiches, resulting in an 80-m-thick fining-upward, sorted suevite in the flooded crater. Within a day, the reflected rim-wave tsunami reached the crater, depositing a cross-bedded sand-to-fine gravel layer enriched in polycyclic aromatic hydrocarbons overlain by charcoal fragments. Generation of a deep crater open to the ocean allowed rapid flooding and sediment accumulation rates among the highest known in the geologic record. The high-resolution section provides insight into the impact environmental effects, including charcoal as evidence for impactinduced wildfires and a paucity of sulfur-rich evaporites from the target supporting rapid global cooling and darkness as extinction mechanisms. © 2019 National Academy of Sciences. All rights reserved.
2252.
The Marine Isotope Stage 12 pollen record from Lake Ohrid (SE Europe): Investigating short-term climate change under extreme glacial conditions
Quaternary Science Reviews,
221
2019
ISSN: 02773791
Publisher: Elsevier Ltd
Keywords:▾
Balkans; Lake Ohrid; Mediterranean Sea; Mediterranean Sea (East); Expansion; Forestry; Glacial geology; Isotopes; Lakes; Sea level; Vegetation; Climate variability; Eastern Mediterranean; Lake Ohrid; Middle Pleistocene; Quantitative climate estimates; Vegetation dynamics; climate change; climate variation; forest cover; glaciation; ice sheet; ice-rafted debris; interstadial; Last Glacial; marine isotope stage; meridional circulation; Pleistocene; sea level; terrestrial ecosystem; vegetation dynamics; Climate change
Abstract: ▾ Characterised by a maximum expansion of continental ice sheets in the Northern Hemisphere, Marine Isotope Stage (MIS) 12 (∼478–424 ka before present) was one of the strongest glacials of the Quaternary. Because the information currently available on MIS 12 is predominantly derived from marine records, the imprint of this extreme glaciation on the terrestrial realm – and notably on terrestrial ecosystems – has remained poorly constrained. Here we present a new, centennial-scale-resolution pollen record from Lake Ohrid (Balkan Peninsula, SE Europe) augmented by pollen-based quantitative temperature and precipitation estimates. Our dataset, which spans the period from 488 to 420 ka, shows that the forest cover around Lake Ohrid decreased substantially over the course of MIS 12; this decrease was associated with a gradual lowering of winter and mean annual temperatures (and to a lesser extent of summer temperatures) as well as mean annual precipitation. Superimposed on this long-term development, abrupt changes in regional forest cover indicate a pronounced millennial-scale climate variability that bears strong resemblance to the interstadial and stadial events of the Last Glacial. This variability is expressed by repeated high-amplitude forest expansions and contractions around Lake Ohrid during MIS 12c and the oldest part of 12b substage (i.e., from ∼477 to 448 ka). The forest oscillations can be correlated to previously documented episodes of surface-water variability and ice-rafted debris deposition in the North Atlantic. This pattern suggests a coupling between the climatically forced tree-population changes in SE Europe and the variability of the Atlantic Meridional Ocean Circulation during MIS 12c and partially 12b on millennial timescales. In contrast, the youngest part of MIS 12b and MIS 12a (i.e., from ∼448 to 424 ka) lack high-amplitude forest expansions and contractions around Lake Ohrid. Comparison with sea-level reconstructions for MIS 12 suggests that millennial-scale vegetation variability in Lake Ohrid was strongest when sea level was between 30 and 100 m lower than today, whereas it was absent when sea level was lower than 100 m relative to the present. © 2019 Elsevier Ltd
2251.
The sedimentary origin of black and white banded cherts of the Buck Reef, Barberton, South Africa
Geosciences (Switzerland),
9
(10)
2019
ISSN: 20763263
Publisher: MDPI AG
Abstract: ▾ The Buck Reef is a 250–400 m thick sequence of banded black and white (B&W) cherts deposited ca. 3416 Ma ago in a shallow basin. We provide field, petrological and geochemical constraints on the chert-forming process and the origin of the banding. White layers consist of nearly pure microquartz, while black layers are mixed with detrital carbonaceous matter, quartz grains and carbonaceous microlaminae, interpreted as remnants of microbial mats. The circulation of Si-rich fluid is recorded by abundant chert veins and pervasive silicification. However, the high purity of the white layers, their lack of internal structures and extremely low Al, Ti and high-field-strength elements preclude an origin by silicification of sedimentary or volcanic precursors. Moreover, their reworking at the surface into slab conglomerates, and sediment-like contacts with black layers rule out a diagenetic origin. We propose a new model whereby the white layers were periodically deposited as precipitates of pure silica; and the micro-layering within the black layers formed by annual temperature fluctuations, favouring microbial activity in summer and inorganic silica precipitation in winter. Outcrop-scale alternation of B&W layers was associated with major, thousand-year-long climate events: white cherts represent massive silica precipitation resulting from changes in ocean circulation and temperature during cold intervals. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.
2250.
The status of exploitation techniques of natural gas hydrate
Chinese Journal of Chemical Engineering,
27
(9)
2133-2147
2019
ISSN: 10049541
Publisher: Materials China
Keywords:▾
Carbon dioxide; Environmental impact; Gas industry; Gases; Hydration; Ice problems; Natural gas; Petroleum reservoir evaluation; Production; Proven reserves; Sustainable development, CO2 exchange; Depressurizations; Exploitation techniques; Exploration and exploitation; Gas production technique; Production efficiency; Production techniques; Thermal stimulation, Gas hydrates
Abstract: ▾ Natural gas hydrate (NGH) has been widely considered as an alternative form of energy with huge potential, due to its tremendous reserves, cleanness and high energy density. Several countries involving Japan, Canada, India and China have launched national projects on the exploration and exploitation of gas hydrate resources. At the beginning of this century, an early trial production of hydrate resources was carried out in Mallik permafrost region, Canada. Japan has conducted the first field test from marine hydrates in 2013, followed by another trial in 2017. China also made its first trial production from marine hydrate sediments in 2017. Yet the low production efficiency, ice/hydrate regeneration, and sand problems are still commonly encountered; the worldwide progress is far before commercialization. Up to now, many gas production techniques have been proposed, and a few of them have been adopted in the field production tests. Nevertheless, hardly any method appears really promising; each of them shows limitations at certain conditions. Therefore, further efforts should be made on the economic efficiency as well as sustainability and environmental impacts. In this paper, the investigations on NGH exploitation techniques are comprehensively reviewed, involving depressurization, thermal stimulation, chemical inhibitor injection, CO2–CH4 exchange, their combinations, and some novel techniques. The behavior of each method and its further potential in the field test are discussed. The advantages and limitations of laboratory studies are also analyzed. The work could give some guidance in the future formulation of exploitation scheme and evaluation of gas production behavior from hydrate reservoirs. © 2019 Elsevier B.V.
2249.
Nonvolcanic Carbon Dioxide Emission at Continental Rifts: The Bublak Mofette Area, Western Eger Rift, Czech Republic
Geofluids,
2019
2019
ISSN: 14688115
Publisher: Hindawi Limited
Keywords:▾
Cheb Basin; Czech Republic; Karlovarsky; carbon dioxide; carbon emission; degassing; flux measurement; rift zone; tectonics
Abstract: ▾ This study presents the results of gas flux measurements of cold, mantle-derived CO2 release at the Bublák mofette field (BMF), located inside of the N-S directed Počátky Plesná fault zone (PPFZ). The PPFZ is presently seismically active, located in the eastern part of the Cheb Basin, western Eger Rift, Central Europe. The goal of the work was to identify the linkage between tectonics and gas flux. The investigated area has a size of 0,43 km2 in which 1.115 locations have been measured. Besides classical soil CO2 gas flux measurements using the closed chamber method (West Systems), drone-based orthophotos were used in combination with knowledge of plant zonation to find zones of high degassing in the agriculturally unused part of the BMF. The highest observed soil CO2 gas flux is 177.926,17 g m-2 d-1, and the lowest is 0,28 g m-2 d-1. Three statistical methods were used for the calculation of the gas flux: arithmetic mean, kriging, and trans-Gaussian kriging. The average CO2 soil degassing of the BMF is 30 t d-1 for an area of 0,43 km2. Since the CO2 soil degassing of the Hartoušov mofette field (HMF) amounts to 23 t d-1 for an area of 0,35 km2, the average dry degassing values of the BMF and HMF are in the same magnitude of order. The amount of CO2 flux from wet mofettes is 3 t d-1 for the BMF and 0,6 t d-1 for the HMF. It was found that the degassing in the BMF and HMF is not in accordance with the pull-apart basin interpretation, based on the direction of degassing as well as topography and sediment fill of the suggested basins. En-echelon faults inside of the PPFZ act as fluid channels to depth (CO2 conduits). These structures inside the PPFZ show beginning faulting and act as tectonic control of CO2 degassing. © 2019 Horst Kämpf et al.
2248.
Stress-Strain Evolution During Peak-Ring Formation: A Case Study of the Chicxulub Impact Structure
Journal of Geophysical Research: Planets,
124
(2)
396-417
2019
Abstract: ▾ Deformation is a ubiquitous process that occurs to rocks during impact cratering; thus, quantifying the deformation of those rocks can provide first-order constraints on the process of impact cratering. Until now, specific quantification of the conditions of stress and strain within models of impact cratering has not been compared to structural observations. This paper describes a methodology to analyze stress and strain within numerical impact models. This method is then used to predict deformation and its cause during peak-ring formation: a complex process that is not fully understood, requiring remarkable transient weakening and causing a significant redistribution of crustal rocks. The presented results are timely due to the recent Joint International Ocean Discovery Program and International Continental Scientific Drilling Program drilling of the peak ring within the Chicxulub crater, permitting direct comparison between the deformation history within numerical models and the structural history of rocks from a peak ring. The modeled results are remarkably consistent with observed deformation within the Chicxulub peak ring, constraining the following: (1) the orientation of rocks relative to their preimpact orientation; (2) total strain, strain rates, and the type of shear during each stage of cratering; and (3) the orientation and magnitude of principal stresses during each stage of cratering. The methodology and analysis used to generate these predictions is general and, therefore, allows numerical impact models to be constrained by structural observations of impact craters and for those models to produce quantitative predictions. ©2019. American Geophysical Union. All Rights Reserved.
2247.
New geochronological constraints for the Upper Cretaceous Nenjiang Formation in the Songliao Basin, NE China
Cretaceous Research,
102160-169
2019
ISSN: 01956671
Publisher: Academic Press
Keywords:▾
Cretaceous; geochronology; mass spectrometry; paleoenvironment; uranium-lead dating; zircon, China; Songliao Basin
Abstract: ▾ The Nenjiang Formation in the Songliao Basin, northeastern China, is of great significance because it records a series of geological, geodynamical and paleoenvironmental events, such as lake transgression events, lake anoxic events, sea water incursion events, Cretaceous Normal Superchron, and important stratigraphic boundaries. Here we report a chronology for the non-marine Upper Cretaceous Nenjiang Formation based on secondary ion mass spectrometry (SIMS) U–Pb zircon analyses from the east borehole of the Cretaceous Continental Scientific Drilling and two outcrop sections, which are located in different structural provinces of the Songliao Basin. Stratigraphic correlation between the borehole sequence and the exposed outcrop sections is achieved by combining lithostratigraphy, biostratigraphy, and SIMS U–Pb zircon geochronology. Two bentonite layers are recognized in the Nenjiang Formation: the older occurs at the formational contact between the Yaojia and Nenjiang Formations; the younger occurs between Members 1 and 2 of the Nenjiang Formation. SIMS U–Pb zircon dating yields ages of 85.1–85.2 Ma and 83.0–83.3 Ma, respectively, representing ages of the boundaries of the Yaojia/Nenjiang Formations and Members 1/2 of the Nenjiang Formation, as well as ages of lake transgression events and associated lake anoxic events, and two of the sea water incursion events. Furthermore, the age of Cretaceous Normal Superchron termination can be estimated at 82.5–82.8 Ma. © 2019 Elsevier Ltd
2246.
Classifying past climate change in the Chew Bahir basin, southern Ethiopia, using recurrence quantification analysis
Climate Dynamics,
53
(5-6)
2557-2572
2019
ISSN: 09307575
Publisher: Springer Verlag
Keywords:▾
atmospheric dynamics; climate change; Holocene; paleoclimate; Pleistocene; recurrence interval; time series analysis, Ethiopia
Abstract: ▾ The Chew Bahir Drilling Project (CBDP) aims to test possible linkages between climate and evolution in Africa through the analysis of sediment cores that have recorded environmental changes in the Chew Bahir basin. In this statistical project we consider the Chew Bahir palaeolake to be a dynamical system consisting of interactions between its different components, such as the waterbody, the sediment beneath lake, and the organisms living within and around the lake. Recurrence is a common feature of such dynamical systems, with recurring patterns in the state of the system reflecting typical influences. Identifying and defining these influences contributes significantly to our understanding of the dynamics of the system. Different recurring changes in precipitation, evaporation, and wind speed in the Chew Bahir basin could result in similar (but not identical) conditions in the lake (e.g., depth and area of the lake, alkalinity and salinity of the lake water, species assemblages in the water body, and diagenesis in the sediments). Recurrence plots (RPs) are graphic displays of such recurring states within a system. Measures of complexity were subsequently introduced to complement the visual inspection of recurrence plots, and provide quantitative descriptions for use in recurrence quantification analysis (RQA). We present and discuss herein results from an RQA on the environmental record from six short (< 17 m) sediment cores collected during the CBDP, spanning the last 45 kyrs. The different types of variability and transitions in these records were classified to improve our understanding of the response of the biosphere to climate change, and especially the response of humans in the area. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.
2245.
Characteristics of spores and pollen assemblages from the Lower Cretaceous Shahezi Formation in the SK2 Borehole
Geology in China,
46
(5)
1245-1246
2019
ISSN: 1000-3657