All ICDP Publications with Abstracts
From parent-sysfolder "Publications" + 2 folder-levels deep
2419.
Winding down the Chicxulub impact: The transition between impact and normal marine sedimentation near ground zero
Marine Geology,
430
2020
Abstract: ▾ The Chicxulub impact led to the formation of a ~ 200-km wide by ~1-km deep crater on México's Yucatán Peninsula. Over a period of hours after the impact the ocean re-entered and covered the impact basin beneath several hundred meters of water. A suite of impactites were deposited across the crater during crater formation, and by the resurge, tsunami and seiche events that followed. International Ocean Discovery Program/International Continental Scientific Drilling Program Expedition 364 drilled into the peak ring of the Chicxulub crater, and recovered ~130 m of impact deposits and a 75-cm thick, fine-grained, carbonate-rich “Transitional Unit”, above which normal marine sedimentation resumed. Here, we describe the results of analyses of the uppermost impact breccia (suevite) and the Transitional Unit, which suggests a gradual waning of energy recorded by this local K-Pg boundary sequence. The dominant depositional motif in the upper suevite and the Transitional Unit is of rapid sedimentation characterized by graded bedding, local cross bedding, and evidence of oscillatory currents. The lower Transitional Unit records the change from deposition of dominantly sand-sized to mainly silt to clay sized material with impact debris that decreases in both grain size and abundance upward. The middle part of the Transitional Unit is interrupted by a 20 cm thick soft sediment slump overlain by graded and oscillatory current cross-laminated beds. The uppermost Transitional Unit is also soft sediment deformed, contains trace fossils, and an increasing abundance of planktic foraminifer and calcareous nannoplankton survivors. The Transitional Unit, as with similar deposits in other marine target impact craters, records the final phases of impact-related sedimentation prior to resumption of normal marine conditions. Petrographic and stable isotopic analyses of carbon from organic matter provide insight into post-impact processes. δ13Corg values are between terrestrial and marine end members with fluctuations of 1–3‰. Timing of deposition of the Transitional Unit is complicated to ascertain. The repetitive normally graded laminae, both below and above the soft sediment deformed interval, record rapid deposition from currents driven by tsunami and seiches, processes that likely operated for weeks to potentially years post-impact due to subsequent continental margin collapse events. Highly siderophile element-enrichment at the top of the unit is likely from fine-grained ejecta that circulated in the atmosphere for several years prior to settling. The Transitional Unit is thus an exquisite record of the final phases of impact-related sedimentation related to one of the most consequential events in Earth history. © 2020 The Authors
2418.
Assessment of rock damage using seismic methods: Wave speeds and attenuation from borehole measurements in the Chicxulub Impact structure.
2020
University of Alberta, Edmonton, AB, Canada; Purdue University, West Lafayette, IN, United States; University of Texas Institute for Geophysics, Austin, TX, United States; Université de Montpellier, Montpellier, Languedoc-Roussillon, France; Imperial College London, London, United Kingdom2417.
[English]
Shallow geothermal potential of the snake river plain
Volume 44
,
Page 504-534
Publisher
Geothermal Resources Council
2020
Roy M. Huffington Department of Earth Sciences, Southern Methodist University, Dallas, TX, United States; National Renewable Energy Laboratory, Golden, CO, United States; Columbia Geoscience, Portland, OR, United StatesISBN:
9781713822097
2416.
A Strainmeter Array Along the Alto Tiberina Fault System, Central Italy
EGU General Assembly Conference Abstracts
,
Page 19792
2020
2415.
The Bushveld Complex Drilling Project: an ICDP project on the origins, emplacement and consequences of the world's largest known igneous intrusion
,
AGU Fall Meeting Abstracts
Volume2020
,
Page NS008--01
2020
2414.
Microbial Signatures in Deep CO2-Saturated Miocene Sediments of the Active Hartoušov Mofette System (NW Czech Republic)
Frontiers in Microbiology,
11
2020
ISSN: 1664302X
Publisher: Frontiers Media S.A.
Keywords:▾
biological marker; carbon; carbon dioxide; carbon nitrogen sulfur monocycle; clario star; fluorescein sodium; ground water; organic carbon; organic nitrogen; RNA 16S; soil organic matter; urea; Acidobacteria; Actinobacteria; Alphaproteobacteria; Arabidopsis thaliana; Article; bacterial microbiome; Bacteroidetes; Betaproteobacteria; biogeography; bioinformatics; biosphere; calibration; carbon dioxide fixing bacterium; Chloroflexi; column chromatography; Comamonadaceae; community structure; Crenarchaeota; cyanobacterium; DNA extraction; DNA purification; electrospray mass spectrometry; Escherichia coli; freeze drying; Gallionella; Gammaproteobacteria; gene sequence; geochemical analysis; high performance liquid chromatography; homogenate; isotope analysis; lipid analysis; liquid chromatography; methanogenesis; Methanosaeta; Methanosarcina; microbial biomass; microbial community; microbial contamination; microbial diversity; migration; Miocene; multidimensional scaling; nonhuman; organisms by metabolism; population abundance; real time polymerase chain reaction; saponification; soil microflora; stratigraphy; sulfate oxidizing bacterium; Sulfuricurvum; thermal spring; total nitrogen content; total organic carbon; ultra performance liquid chromatography
Abstract: ▾ The Hartoušov mofette system is a natural CO2 degassing site in the central Cheb Basin (Eger Rift, Central Europe). In early 2016 a 108 m deep core was obtained from this system to investigate the impact of ascending mantle-derived CO2 on indigenous deep microbial communities and their surrounding life habitat. During drilling, a CO2 blow out occurred at a depth of 78.5 meter below surface (mbs) suggesting a CO2 reservoir associated with a deep low-permeable CO2-saturated saline aquifer at the transition from Early Miocene terrestrial to lacustrine sediments. Past microbial communities were investigated by hopanoids and glycerol dialkyl glycerol tetraethers (GDGTs) reflecting the environmental conditions during the time of deposition rather than showing a signal of the current deep biosphere. The composition and distribution of the deep microbial community potentially stimulated by the upward migration of CO2 starting during Mid Pleistocene time was investigated by intact polar lipids (IPLs), quantitative polymerase chain reaction (qPCR), and deoxyribonucleic acid (DNA) analysis. The deep biosphere is characterized by microorganisms that are linked to the distribution and migration of the ascending CO2-saturated groundwater and the availability of organic matter instead of being linked to single lithological units of the investigated rock profile. Our findings revealed high relative abundances of common soil and water bacteria, in particular the facultative, anaerobic and potential iron-oxidizing Acidovorax and other members of the family Comamonadaceae across the whole recovered core. The results also highlighted the frequent detection of the putative sulfate-oxidizing and CO2-fixating genus Sulfuricurvum at certain depths. A set of new IPLs are suggested to be indicative for microorganisms associated to CO2 accumulation in the mofette system. © Copyright © 2020 Liu, Adler, Lipus, Kämpf, Bussert, Plessen, Schulz, Krauze, Horn, Wagner, Mangelsdorf and Alawi.
2413.
Reflection seismic surveys to site the Drilling the Ivrea Verbano zonE (DIVE) proposed drill-holes, Val Sesia and Val d’Ossola, Italy.
Copernicus Meetings
2020
2412.
Thermal imprints of Cenozoic tectonic evolution in the Songliao Basin, NE China: Evidence from apatite fission-track (AFT) of CCSD-SK1 borehole
Journal of Asian Earth Sciences,
195
2020
ISSN: 13679120
Publisher: Elsevier Ltd
Keywords:▾
apatite; borehole; Cenozoic; exhumation; fission track dating; historical perspective; plate tectonics; subduction; tectonic evolution, China; Songliao Basin
Abstract: ▾ We conduct apatite fission-track analysis in the Songliao Basin to reveal the Cenozoic tectonic uplifts and determine how basin development was associated with the transformation from the Paleo-Pacific plate to the Pacific plate and the change of the Pacific plate velocity. Our results from the CCSD-SK1 boreholes in the northern Songliao Basin reveal three Cenozoic cooling (uplift) events:Paleocene (65–50 Ma), Oligocene (33–22 Ma), late Miocene–Pliocene (14–6 Ma) with the apparent mean exhumation rates of 0.08–0.09 mm/yr, 0.08–0.09 mm/yr and 0.11–0.24 mm/yr, respectively. The total removal of the sedimentary cover resulted from 3 cooling (uplift) events is about 1500 m, the removal by the extreme cooling (uplift) event (14–6 Ma) is about 900 m. In this paper, we infer that the transformation of the Paleo-Pacific plate (Izanagi plate) to the Pacific plate plays the first-order control on the first cooling event (65–50 Ma). The second (33–22 Ma) and third (14–6 Ma) cooling events are closely related to the steady and relatively high motion velocity of the Pacific plate. Since Oligocene, a large scale of tectonic uplifts widely happened not only in basins but also in the ranges around them in northeastern China. © 2020 Elsevier Ltd
2411.
The Role of Meteorite Impacts in the Origin of Life
Astrobiology,
20
(9)
1121-1149
2020
Abstract: ▾ The conditions, timing, and setting for the origin of life on Earth and whether life exists elsewhere in our solar system and beyond represent some of the most fundamental scientific questions of our time. Although the bombardment of planets and satellites by asteroids and comets has long been viewed as a destructive process that would have presented a barrier to the emergence of life and frustrated or extinguished life, we provide a comprehensive synthesis of data and observations on the beneficial role of impacts in a wide range of prebiotic and biological processes. In the context of previously proposed environments for the origin of life on Earth, we discuss how meteorite impacts can generate both subaerial and submarine hydrothermal vents, abundant hydrothermal-sedimentary settings, and impact analogues for volcanic pumice rafts and splash pools. Impact events can also deliver and/or generate many of the necessary chemical ingredients for life and catalytic substrates such as clays as well. The role that impact cratering plays in fracturing planetary crusts and its effects on deep subsurface habitats for life are also discussed. In summary, we propose that meteorite impact events are a fundamental geobiological process in planetary evolution that played an important role in the origin of life on Earth. We conclude with the recommendation that impact craters should be considered prime sites in the search for evidence of past life on Mars. Furthermore, unlike other geological processes such as volcanism or plate tectonics, impact cratering is ubiquitous on planetary bodies throughout the Universe and is independent of size, composition, and distance from the host star. Impact events thus provide a mechanism with the potential to generate habitable planets, moons, and asteroids throughout the Solar System and beyond. © G.R. Osinski et al., 2020; Published by Mary Ann Liebert, Inc. 2020.
2410.
Shocked titanite records Chicxulub hydrothermal alteration and impact age
Geochimica et Cosmochimica Acta,
28112-30
2020
Abstract: ▾ Hydrothermal activity is a common phenomenon in the wake of impact events, yet identifying and dating impact hydrothermal systems can be challenging. This study provides the first detailed assessment of the effects of shock microstructures and impact-related alteration on the U-Pb systematics and trace elements of titanite (CaTiSiO5), focusing on shocked granite target rocks from the peak ring of the Chicxulub impact structure, Mexico. A > 1 mm long, shock-twinned titanite grain preserves a dense network of irregular microcracks, some of which exploit shock twin interfaces. Secondary microcrystalline anatase and pyrite are heterogeneously distributed along some microcracks. In situ laser ablation multi-collector inductively-coupled plasma mass spectrometry (LA-MC-ICPMS) analysis reveals a mixture of three end-member Pb components. The Pb components are: 1) common Pb, consistent with the Pb isotopic signature of adjacent alkali feldspar; 2) radiogenic Pb accumulated since magmatic crystallization; and 3) a secondary, younger Pb signature due to impact-related complete radiogenic Pb loss. The youngest derived ages define a regression from common Pb that intersects Concordia at 67 ± 4 Ma, in agreement with the established age of 66.04 ± 0.05 Ma for the Chicxulub impact event. Contour maps of LA-MC-ICPMS data reveal that the young ages are spatially restricted to microstructurally-complex domains that correlate with significant depletion in trace elements (REE-Y-Zr-Nb-Mo-Sn-Th) and reduction in magnitude of the Eu/Eu* anomaly. Mapping by time-of-flight secondary ion mass spectrometry (ToF-SIMS) show that patterns of localised element depletion in titanite are spatially related to microcracks, which are enriched in Al. The spatial correlation of ages and trace element abundance is consistent with localised removal of Pb and other trace elements from a pervasive network of fast fluid pathways in fractured domains via a fluid-mediated element transport process associated with the impact event. Here we interpret the 67 ± 4 Ma U-Pb age to represent hydrothermal Pb-loss in the Chicxulub peak ring in the wake of the impact event. These results highlight the potential of our analytical approach using titanite geochronology and geochemistry for dating post-impact hydrothermal activity in impact structures elsewhere. © 2020 Elsevier Ltd
2409.
Testing lake-level reconstructions based on rock magnetic proxies for the sediment record of Laguna Cháltel (Patagonia, Argentina)
Quaternary Research (United States),
95113 – 128
2020
2408.
Source/reservoir characteristics and shale gas “sweet spot” interval in Shahezi mudstone of Well SKII in Songliao Basin, NE China
Arabian Journal of Geosciences,
13
(13)
2020
2407.
Stratigraphic correlation and splice generation for sediments recovered from a large-lake drilling project: an example from Lake Junín, Peru
Journal of Paleolimnology,
63
(1)
83-100
2020
ISSN: 09212728
Publisher: Springer
Keywords:▾
deep drilling; historical record; lacustrine deposit; physical property; project assessment; reconstruction; recovery; scale effect; sediment core; stratigraphic correlation, Junin; Lake Junin; Peru
Abstract: ▾ Sediment records from deep-drilling projects such as those carried out by the International Continental Scientific Drilling Program are often tens to hundreds of meters in length. To ensure the complete recovery of a stratigraphic section, a basin is usually cored multiple times in adjacent holes so that gaps between sequential cores, poorly recovered sections, or intervals affected by disturbance can be bridged or replaced with sediments from another hole. Stratigraphic correlation, the alignment of stratigraphically-equivalent horizons in cores from different holes in a common-depth scale, and splice generation, the integration of the most-representative core sections into a composite-stratigraphic section, are essential steps in this process to both evaluate and synthesize the recovered-sediment record and focus the scientific analyses. However, these undertakings can be complex and are inherently subjective, making the need for the development of a single robust stratigraphic section early in the project critical to its success. Despite this, the steps between core recovery and on-splice data generation are rarely published in sufficient detail to allow reconstruction, or refinement, of the composited record at a later date. To increase the transparency of how the composite record is created, and to provide a template for future projects, we detail the step-by-step approaches and decisions involved in generating the composite-depth scale and complete-stratigraphic splice following recovery of sediments from Lake Junín, Peru. We first explain the details and nuances of different drilling-depth scales before describing how we integrated different physical property records to generate the composite-depth scale and complete-stratigraphic splice. Here, we show that due to the complex stratigraphy in the Lake Junín sediments, high-resolution line-scan images of the cores offer millimeter-scale precision for construction of the primary-stratigraphic splice at a resolution not afforded by other physical property data. Finally, through comparison of the spliced record to physical-property records acquired in situ on the borehole, we demonstrate that the stratigraphic splice is an accurate representation of the sediment accumulated in the Lake Junín basin. © 2019, Springer Nature B.V.
2406.
Stress Field Interactions Between Overlapping Shield Volcanoes: Borehole Breakout Evidence From the Island of Hawai'i, USA
Journal of Geophysical Research: Solid Earth,
125
(8)
2020
ISSN: 21699313
Publisher: Blackwell Publishing Ltd
Keywords:▾
Hawaii [(ISL) Hawaiian Islands]; Hawaii [United States]; Hawaiian Islands; Mauna Kea; Mauna Loa; borehole breakout; in situ stress; lava flow; shield volcano; stress field; volcanic island
Abstract: ▾ Knowledge of the in situ stress state of the Earth's crust plays a key role in understanding geological processes including plate tectonics, earthquakes, slope failure, and igneous emplacement. In this paper, we determine the in situ stress orientation from the PTA2 borehole on the island of Hawai'i, drilled into a lava flow dominated sequence between Mauna Kea and Mauna Loa. High-resolution acoustic images were collected from the open hole interval 886 m to 1,567 m. Based on identification of 371 borehole breakouts for a total length of 310 m, the mean orientation of the minimum horizontal principal stress is N106° and remains constant across different volcanic rock fabrics. Changes in borehole breakout shape are linked to the different strength of volcanic facies and intra-facies. The orientation of the present-day stress field at Mauna Kea deviates from the plate forces and regional tectonic stress field. We interpret the compressive stress regime at the PTA2 site as resulting from the competing gravitational fields of the large topographic highs of Mauna Kea and Mauna Loa. Our study reveals that the mass accumulation associated with shield volcano growth imparts significant local variations to the subsurface stress state on volcanic islands consisting of overlapping shield volcanoes. The results have significant implications for stress accumulation leading to brittle failure and flank collapse, along with potentially influencing magma accumulation and ascent pathways during volcanic island evolution. This study provides the first insights into the orientation of the present-day stress field between the major island forming shield volcanoes of Hawai'i. ©2020. The Authors.
2405.
Stress-state differences between sedimentary cover and basement of the Songliao Basin, NE China: In-situ stress measurements at 6–7 km depth of an ICDP Scientific Drilling borehole (SK-II)
Tectonophysics,
777
2020
ISSN: 00401951
Publisher: Elsevier B.V.
Keywords:▾
Boreholes; Buildings; Sedimentology; Stresses; Strike-slip faults, Anelastic strain recovery; In-situ stress measurement; Insitu stress; Maximum principal stress; Scientific drilling; Seismic reflection profiles; Songliao basin; Stress state, Fault slips, anelasticity; basement rock; borehole; depth; drilling; in situ measurement; normal fault; Pacific plate; sedimentary basin; seismic reflection; strain analysis; stress field, China; Songliao Basin
Abstract: ▾ The stress state down to the basement within sedimentary basins yet remains poorly understood. The anelastic strain recovery (ASR) method was employed to measure the stress state in the SK-II borehole in the Songliao Basin, Northeast China. The results show that the stress state differs significantly between the sedimentary cover and basement. In the sedimentary cover (6296–6335 m), the maximum principal stress σ1 is nearly vertical, which is in the normal faulting stress regime dominated by gravitation, in accordance with the normal faults observed on seismic reflection profiles within the sedimentary cover. In contrast, the basement (6646–6846 m) shows that σ1 is nearly horizontal, suggesting a strike-slip or reverse-faulting regime. The stress state of the basement is close to the reasonable stress condition for the Eurasian Plate far from a western Pacific plate subduction zone and consistent with the focal mechanisms of earthquakes (7–15 km) in the vicinity of ICDP SK-II borehole. The difference of stress state may imply that the far-field stress generated by the western Pacific plate has limited effects on the sedimentary cover, an increase in thickness correlates with an increasing influence of tectonic stress with depth. © 2020 Elsevier B.V.
2404.
Superdeep Drilling and Its Impact on the Seismic Models of the Fennoscandian Shield
Springer Proceedings in Earth and Environmental Sciences
253 – 261
2020
ISSN: 2524342X
Publisher: Springer Nature
Abstract: ▾ Attempts to interpret the origin of seismic boundaries in the crystalline crust in the Fennoscandian Shield from deep drilling records and available geological and geophysical data were made by a number of authors. This article contains an overview of the most essential results reported so far. Deep drilling was conducted in several regions of the Fennoscandian Shield: Kola, Russia (SG-3), to a depth of 12,262 m (1970–1990); Gravberg (GR) and Stenberg-I, Central Sweden, to a depth of 6337 m (1986–1987); and 6529 m (1991–1992); Outokumpu (OU), SE Finland, to a depth of 2516 m (2004–2005); Pogranichnaya (P-1), Sredny Peninsula, Murmansk Region, Russia, to a depth of 5200 m (2004–2006); and Onega, Central Karelia, Russia (ON), to a depth of 3537 m (2007–2008). The results obtained were analyzed. They show considerable discrepancies between forecast seismic-geological models and the actual structure of the upper portion of the continental crust. Deep drilling has proved that heterogeneities in the upper portion of the crystalline crust, indicated by geophysical data, are due to changes in the composition and physical conditions of deep-seated rocks. Therefore, even approximate rock composition cannot be uniquely estimated from elastic wave velocities alone. Deep drilling showed the real pattern and origin of low-velocity zones in the upper portion of the crust and did not show that layers become more homogeneous with depth. The origin of intra-crustal seismic boundaries could be associated with various factors, such as variations in mineralogical composition, structural and textural differences between the rocks, and a thermodynamic setting. © 2020, Springer Nature Switzerland AG.
2403.
Tertiarius minutulus sp. Nov. (Stephanodiscaceae, Bacillariophyta) – A new fossil diatom species from lake ohrid
European Journal of Taxonomy,
2020
(670)
1 – 14
2020
2402.
The challenge of the enigmatic tricolporate tropical pollen type: A case study from Sulawesi, Indonesia
Review of Palaeobotany and Palynology,
273
2020
ISSN: 00346667
Publisher: Elsevier B.V.
Keywords:▾
Greater Sunda Islands; Indonesia; Lake Towuti; Malili Lakes; South Sulawesi; Sulawesi; Sunda Isles; Saurauia; colonization; fossil record; Last Glacial Maximum; palynology; range expansion; river bank; sedimentary sequence
Abstract: ▾ Any palynologist who has worked in the tropics has undoubtedly dealt with the frustration of trying to classify small, tricolporate pollen into meaningful taxonomic groups. While this is not a significant issue where coarse-scale identifications represent similar habitat indicators or “unknown” types are rare, it poses a problem when one of these “unknowns” overwhelm the record. This is the case with unknown “type 69” – a small, tricolporate pollen grain encountered within a 60,000-year sediment sequence from Lake Towuti in Sulawesi, Indonesia. This type comprises up to 35% of the pollen count for some Last Glacial Maximum (LGM) samples (highlighting its climatic sensitivity) but could not be identified by experts in the field. This study thus aimed to compare the metrics of “type 69” with reference pollen from Sulawesi to aid with its identification. In doing so, we present a pollen atlas of 63 maritime southeast Asian pollen types. Our results show that “type 69” aligns with metrics taken from Saurauia pollen. While detailed ecological data on Saurauia species in Sulawesi are lacking, they appear to favor higher elevations and riverbank settings, and are post-disturbance colonizers. Proliferation of this pollen type during the LGM is therefore linked to a combination of downslope range expansion of Saurauia species under a cooler climate and potentially, out competition of upland everwet forest taxa. This study demonstrates an approach to managing important unknown fossil pollen types in tropical records and, through the ensuing pollen atlas, provides a tool for progressing palynology in southeast Asia. © 2019 Elsevier B.V.
2401.
The onset of oxidative weathering traced by uranium isotopes
Precambrian Research,
338
2020
2400.
The Cretaceous stratigraphy, Songliao Basin, Northeast China: Constrains from drillings and geophysics
Open Geosciences,
12
(1)
1212 – 1223
2020
ISSN: 23915447
Publisher: De Gruyter Open Ltd
Keywords:▾
China; Songliao Basin; Geochronology; Infill drilling; Magnetotellurics; Petroleum industry; Sedimentology; Seismology; Stratigraphy; Continental scientific drillings; Environmental evolution; Geological boundaries; Geothermal drilling; Magnetotelluric soundings; Sedimentary facies; Sedimentary strata; Stratigraphic correlation; borehole geophysics; Cretaceous; drilling; geometry; magnetotelluric method; stratigraphic correlation; tectonic setting; Petroleum geology
Abstract: ▾ The Cretaceous nonmarine sedimentary strata are widespread in Songliao Basin, Northeast China. As the largest oil producer in China, an abundance of data has been generated by the petroleum industry, including sedimentology, seismology, geochemistry, and geochronology in the Songliao Basin. This article reviews the achievements in China Cretaceous Continental Scientific Drilling SK and presents the new results of the China Continental Geothermal Drilling SR1 in stratigraphy and geophysics. The results allow us to establish the relationships among SK-1, SK-2, and SR1, provide some constrains on the tectonic setting of Songliao Basin, and interpret the sedimentary facies and environmental evolution. After stratigraphic correlation of SK and SR boreholes, the result indicates that the geological boundary between the late Cretaceous Mingshui formation and the Paleogene Yi'an formation is at the depth of 115 m. The magnetotelluric sounding anomaly areas are corresponding with the unconformities, which are equivalent to seismic horizon T03, T1, T2, and T3, respectively. In addition, the typical "steer's-head"geometry in the magnetotellurics indicates that the SLB has experienced five evolution stages. © 2020 Zhihe Xu et al., published by De Gruyter 2020.
2399.
The formation of dunite channels within harzburgite in the Wadi Tayin Massif, Oman Ophiolite: insights from compositional variability of Cr-Spinel and olivine in Holes BA1B and BA3A, Oman Drilling Project
Minerals,
10
(2)
167
2020
2398.
The ICDP dead sea deep drilling project – introduction
Quaternary Science Reviews,
249
2020
ISSN: 02773791
Publisher: Elsevier Ltd
Keywords:▾
deep drilling; deep sea; maintenance; paleoenvironment; reconstruction
2397.
The Iceland Deep Drilling Project at Reykjanes: Drilling into the root zone of a black smoker analog
Journal of Volcanology and Geothermal Research,
391
2020
ISSN: 03770273
Publisher: Elsevier B.V.
Keywords:▾
Clay alteration; Drilling fluids; Earthquakes; Effluent treatment; Geothermal fields; Hydraulic structures; Mineral exploration; Rhenium compounds; Rock drills; Silicate minerals; Smoke; Supercritical fluids, Black smokers; Deep drilling; Geothermal; IDDP; Reykjanes, Infill drilling, amphibolite facies; analog model; black smoker; Deep Sea Drilling Project; drilling; exploration; flow field; geothermal system; greenschist facies; hydrothermal alteration; mineral alteration; spreading center; supercritical flow, Atlantic Ocean; Iceland; Mid-Atlantic Ridge; Reykjanes Peninsula
Abstract: ▾ The aim of the Iceland Deep Drilling Project is to drill into supercritical geothermal systems and examine their economic potential. The exploratory well IDDP-2 was drilled in the Reykjanes geothermal field in SW Iceland, on the landward extension of the Mid-Atlantic Ridge. The Reykjanes geothermal field produces from a <300 °C reservoir at 1 to 2.5 km depth and is unusual because it is recharged by seawater. The well was cased to 3000 m depth, and then angled towards the main up-flow zone of the system, to a total slant depth of 4659 m (~4500 m vertical depth). Based on alteration mineral assemblages, joint inversion of wireline logging, and rate of heating measurements, the bottom hole temperature is estimated to be about 535 °C. The major problem encountered during drilling was the total loss of circulation below 3 km depth and continuing to the final depth. Drilling continued without recovering drill cuttings, consequently spot coring provided the only deep rock samples from the well. These cores are characteristic of a basaltic sheeted dike complex, with hydrothermal alteration mineral assemblages that range from greenschist to amphibolite facies, hornblende hornfels, and pyroxene hornfels, allowing the opportunity to investigate water-rock interaction in the active roots of an analog of a submarine hydrothermal system. As they have not yet been sampled, the composition of the deep fluids at Reykjanes is unknown at present. Cold water is currently being injected with the aim of enhancing permeability at depth, before allowing the well to heat up prior to flow tests planned for early 2019. The well has at least two fluid feed zones, a dominant one at 3.4 km depth and a second smaller one at 4.5 km. Extensive geophysical surveys of the Reykjanes Peninsula completed recently allow correlation of geophysical signals with rocks properties and in-situ conditions in the subsurface. Earthquake activity monitored with a local seismic network during drilling the IDDP-2 drilling detected abundant small earthquakes (ML ≤ 2) within the depth range of 3–5 km. A zone at 3–5 km depth below the producing geothermal field that was generally aseismic prior to drilling, but became seismically active during the drilling. The drilling of the IDDP-2 has achieved number of scientific and engineering firsts. It is the deepest and hottest drill hole so far sited on an active mid-ocean spreading center. It penetrated an active supercritical hydrothermal environment at depths analogous to those postulated as the high temperature reaction zones feeding black smoker systems. © 2018 Elsevier B.V.
2396.
The Lake Chad hydrology under current climate change
Scientific Reports,
10
(1)
2020
ISSN: 20452322
Publisher: Nature Research
Abstract: ▾ Lake Chad, in the Sahelian zone of west-central Africa, provides food and water to ~50 million people and supports unique ecosystems and biodiversity. In the past decades, it became a symbol of current climate change, held up by its dramatic shrinkage in the 1980s. Despites a partial recovery in response to increased Sahelian precipitation in the 1990s, Lake Chad is still facing major threats and its contemporary variability under climate change remains highly uncertain. Here, using a new multi-satellite approach, we show that Lake Chad extent has remained stable during the last two decades, despite a slight decrease of its northern pool. Moreover, since the 2000s, groundwater, which contributes to ~70% of Lake Chad’s annual water storage change, is increasing due to water supply provided by its two main tributaries. Our results indicate that in tandem with groundwater and tropical origin of water supply, over the last two decades, Lake Chad is not shrinking and recovers seasonally its surface water extent and volume. This study provides a robust regional understanding of current hydrology and changes in the Lake Chad region, giving a basis for developing future climate adaptation strategies. © 2020, The Author(s).
2395.
The late quaternary tectonic, biogeochemical, and environmental evolution of ferruginous Lake Towuti, Indonesia
Palaeogeography, Palaeoclimatology, Palaeoecology,
556
2020
ISSN: 00310182
Publisher: Elsevier B.V.
Keywords:▾
Far East; Greater Sunda Islands; Lake Towuti; Malili Lakes; Pacific Ocean; Pacific Ocean (West); South Sulawesi; Sulawesi; Sunda Isles; Bacillariophyta; Pisces; Telmatherinidae; biogeochemistry; climate variation; diatom; dispersal; lacustrine deposit; Pleistocene; Quaternary; speciation (biology); subsidence
Abstract: ▾ There is a paucity of long and continuous continental records from South East Asia suitable to inform on past changes and underlying causes of the region's climate and associated diverse ecosystem evolution during the late Quaternary. In 2015, the Towuti Drilling Project (TDP) collected a series of sedimentary drill cores from the tectonic, ferruginous, and highly biodiverse Lake Towuti, Sulawesi, one of Indonesia's oldest lakes. The drill cores contain ~1 Myr of uninterrupted lacustrine sedimentation to document long-term environmental and climatic change in the tropical western Pacific, the impacts of geological and environmental changes on the biological evolution of aquatic taxa, and the geomicrobiology and biogeochemistry of metal-rich, ultramafic-hosted lake sediment. Here we use lithostratigraphic, mineralogical, geochemical, and geochronological datasets to elucidate Lake Towuti's tectonic emergence and its biogeochemical responses to climatic and volcanic forcings since lake formation. Our data document that Lake Towuti emerged during a phase of accelerated tectonic subsidence from a landscape characterized by active river channels, shallow lakes and swamps into a permanent lake at ~1 Ma. The lacustrine sediments feature quasi-rhythmic alternations of green organic rich and red sideritic clay beds reflecting changes in lake mixing and biogeochemistry as a response to temperature and hydrological changes driven by orbital-scale changes in insolation and continental ice volume through the mid- to late Pleistocene. Clay deposition is interrupted by two beds of diatomaceous oozes composed primarily of planktonic diatoms that reflect phases of substantially increased primary productivity. The occurrence of these diatomaceous oozes in close association with multiple tephra beds suggests a trophic state change driven by the addition of volcanically sourced P, possibly in combination with a lake mixing state that supports recycling of P. Data on lake age and ontogeny are also in agreement with molecular-clock estimates of ~0.7 Ma (0.18–1.37 Ma) for the divergence of Lake Towuti's Telmatherinid fishes from a riverine ancestor. Our data therefore are compatible with an evolutionary model in which Lake Towuti's endemic fauna is a result of geographic speciation in the Malili Lakes, a set of large lakes in Southeast Sulawesi, driven by physical or chemical dispersal limits imposed by the regional rivers and lakes. More detailed chronological constraints and refined climate and environmental proxy datasets are currently in preparation and will help to paint a more detailed history of the region's climate and environmental history in future studies. © 2020 Elsevier B.V.