All ICDP Publications with Abstracts
From parent-sysfolder "Publications" + 2 folder-levels deep
2069.
Extreme durability in ancient Roman concretes
Am. Ceram. Soc. Bull,
97
(5)
22--28
2018
2068.
Extraordinary rocks from the peak ring of the Chicxulub impact crater: P-wave velocity, density, and porosity measurements from IODP/ICDP Expedition 364
Earth and Planetary Science Letters,
4951-11
2018
Abstract: ▾ Joint International Ocean Discovery Program and International Continental Scientific Drilling Program Expedition 364 drilled into the peak ring of the Chicxulub impact crater. We present P-wave velocity, density, and porosity measurements from Hole M0077A that reveal unusual physical properties of the peak-ring rocks. Across the boundary between post-impact sedimentary rock and suevite (impact melt-bearing breccia) we measure a sharp decrease in velocity and density, and an increase in porosity. Velocity, density, and porosity values for the suevite are 2900–3700 m/s, 2.06–2.37 g/cm3, and 20–35%, respectively. The thin (25 m) impact melt rock unit below the suevite has velocity measurements of 3650–4350 m/s, density measurements of 2.26–2.37 g/cm3, and porosity measurements of 19–22%. We associate the low velocity, low density, and high porosity of suevite and impact melt rock with rapid emplacement, hydrothermal alteration products, and observations of pore space, vugs, and vesicles. The uplifted granitic peak ring materials have values of 4000–4200 m/s, 2.39–2.44 g/cm3, and 8–13% for velocity, density, and porosity, respectively; these values differ significantly from typical unaltered granite which has higher velocity and density, and lower porosity. The majority of Hole M0077A peak-ring velocity, density, and porosity measurements indicate considerable rock damage, and are consistent with numerical model predictions for peak-ring formation where the lithologies present within the peak ring represent some of the most shocked and damaged rocks in an impact basin. We integrate our results with previous seismic datasets to map the suevite near the borehole. We map suevite below the Paleogene sedimentary rock in the annular trough, on the peak ring, and in the central basin, implying that, post impact, suevite covered the entire floor of the impact basin. Suevite thickness is 100–165 m on the top of the peak ring but 200 m in the central basin, suggesting that suevite flowed downslope from the collapsing central uplift during and after peak-ring formation, accumulating preferentially within the central basin. © 2018 Elsevier B.V.
2067.
Exploration of deep terrestrial subsurface microbiome in Late Cretaceous Deccan traps and underlying Archean basement, India
Scientific Reports,
8
(1)
2018
ISSN: 20452322
Publisher: Nature Publishing Group
Keywords:▾
RNA 16S, biodiversity; biology; environmental microbiology; genetics; India; metagenome; metagenomics; microbiology; microflora; procedures; sediment, Biodiversity; Computational Biology; Environmental Microbiology; Geologic Sediments; India; Metagenome; Metagenomics; Microbiota; RNA, Ribosomal, 16S
Abstract: ▾ Scientific deep drilling at Koyna, western India provides a unique opportunity to explore microbial life within deep biosphere hosted by ~65 Myr old Deccan basalt and Archaean granitic basement. Characteristic low organic carbon content, mafic/felsic nature but distinct trend in sulfate and nitrate concentrations demarcates the basaltic and granitic zones as distinct ecological habitats. Quantitative PCR indicates a depth independent distribution of microorganisms predominated by bacteria. Abundance of dsrB and mcrA genes are relatively higher (at least one order of magnitude) in basalt compared to granite. Bacterial communities are dominated by Alpha-, Beta-, Gammaproteobacteria, Actinobacteria and Firmicutes, whereas Euryarchaeota is the major archaeal group. Strong correlation among the abundance of autotrophic and heterotrophic taxa is noted. Bacteria known for nitrite, sulfur and hydrogen oxidation represent the autotrophs. Fermentative, nitrate/sulfate reducing and methane metabolising microorganisms represent the heterotrophs. Lack of shared operational taxonomic units and distinct clustering of major taxa indicate possible community isolation. Shotgun metagenomics corroborate that chemolithoautotrophic assimilation of carbon coupled with fermentation and anaerobic respiration drive this deep biosphere. This first report on the geomicrobiology of the subsurface of Deccan traps provides an unprecedented opportunity to understand microbial composition and function in the terrestrial, igneous rock-hosted, deep biosphere. © 2018, The Author(s).
2066.
Field-scale permeability and temperature of volcanic crust from borehole data: Campi Flegrei, southern Italy
Journal of Volcanology and Geothermal Research,
357276 – 286
2018
ISSN: 03770273
Publisher: Elsevier B.V.
Keywords:▾
Campania [Italy]; Campi Flegrei; Italy; Napoli [Campania]; Boreholes; Core drilling; Drilling; Fiber optic sensors; Flow of gases; Mechanical permeability; Minerals; Risk assessment; Temperature; Thermal gradients; Thermocouples; Volcanoes; Campi Flegrei; Combined measurements; Comparative assessment; Continental scientific drillings; Geophysical parameters; Petrophysics; Temperature profiles; Thermocouple sensors; borehole; caldera; crustal structure; deep drilling; hydrothermal system; permeability; temperature profile; volcano; Boring
Abstract: ▾ We report combined measurements of petrophysical and geophysical parameters for a 501-m deep borehole located on the eastern side of the active Campi Flegrei caldera (Southern Italy), namely (i) in situ permeability by pumping tests, (ii) laboratory-determined permeability of the drill core, and (iii) thermal gradients by distributed fiber optic and thermocouple sensors. The borehole was drilled during the Campi Flegrei Deep Drilling Project (in the framework of the International Continental Scientific Drilling Program) and gives information on the least explored caldera sector down to pre-caldera deposits. The results allow comparative assessment of permeability obtained from both borehole (at depth between 422 a 501 m) and laboratory tests (on a core sampled at the same depth) for permeability values of ~10−13 m2 (borehole test) and ~10−15 m2 (laboratory test) confirm the scale-dependency of permeability at this site. Additional geochemical and petrophysical determinations (porosity, density, chemistry, mineralogy and texture), together with gas flow measurements, corroborate the hypothesis that discrepancies in the permeability values are likely related to in-situ fracturing. The continuous distributed temperature profile points to a thermal gradient of about 200 °C km−1. Our findings (i) indicate that scale-dependency of permeability has to be carefully considered in modelling of the hydrothermal system at Campi Flegrei, and (ii) improve the understanding of caldera dynamics for monitoring and mitigation of this very high volcanic risk area. © 2018 Elsevier B.V.
2065.
Discrimination of Holocene tephra units in Lake Van using mineral magnetic analysis
Quaternary International,
48644-56
2018
ISSN: 10406182
Publisher: Elsevier Ltd
Keywords:▾
geochemistry; Holocene; lacustrine deposit; magnetic mineral; magnetic susceptibility; remanent magnetization; sediment core; tephra, Lake Van; Turkey
Abstract: ▾ Detailed magnetic analysis of the four sediment cores from Lake Van, Eastern Turkey dating back to 9.4 cal ka BP were carried out for discriminating and correlating tephras and laminated sediments in four different cores. Six tephra units (T0, T1, T2, T3, T4 and T5) with distinct magnetic properties were identified in the cores. The tephra units are characterized by ferrimagnetic material, with a grain size in the pseudo single domain (PSD) range. There is no significant correlation between magnetic susceptibility peaks of the different tephra units except for the tephra T1 and T2. On the contrary ARM profiles show significant correlations as remanent magnetization indicators. The tephra units T1 and T2, have a higher magnetic susceptibility and a higher intensity of remanent magnetization, and finer grain size than the other tephra units. The results suggest that there is a clear difference between the magnetic properties of the different tephra units and the lake sediments. Our findings show that also differential deposition of volcanic material including magnetic mineral occurs during the transport with distance from the volcanic source. © 2018 Elsevier Ltd and INQUA
2064.
Diatoms do radiate: evidence for a freshwater species flock
Journal of Evolutionary Biology,
31
(12)
1969 – 1975
2018
ISSN: 1010061X
Publisher: Blackwell Publishing Ltd
Keywords:▾
Diatoms; Evolution, Molecular; Fossils; Fresh Water; Genetic Variation; Phylogeny; Time Factors; Lake Ohrid; Aneumastus; Bacillariophyta; Protista; fresh water; biogeography; colonization; diatom; endemic species; eukaryote; evolutionary biology; fossil record; freshwater environment; habitat type; molecular analysis; phylogenetics; sediment analysis; species flock; diatom; fossil; genetic variation; genetics; molecular evolution; phylogeny; physiology; time factor
Abstract: ▾ Due to the ubiquity and high dispersal capacity of unicellular eukaryotes, their often extraordinary diversity found in isolated and long-lived ecosystems such as ancient lakes is typically attributed to multiple colonization events rather than to in situ speciation. However, respective evolutionary studies are very scarce and the often high number of species flocks in ancient lakes across multicellular taxa raises the question whether unicellular species, such as diatoms, may radiate as well. Here, we use an integrative approach that includes molecular data from benthic diatom species of the genus Aneumastus endemic to ancient Lake Ohrid, fossil data obtained from the sediment record of a recent deep-drilling project and biogeographical information to test if this group, indeed, constitutes a species flock. Molecular-clock and phylogenetic analyses indicate a young monophyletic group of several endemic species. Molecular, fossil and biogeographical data strongly suggest a rapid intralacustrine diversification, which was possibly triggered by the emergence of novel habitats. This finding is the first evidence for a species flock in diatoms and suggests that in situ speciation is also a relevant evolutionary process for unicellular eukaryotes in isolated ecosystems. © 2018 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2018 European Society For Evolutionary Biology
2063.
Evolution of the Toarcian (Early Jurassic) carbon-cycle and global climatic controls on local sedimentary processes (Cardigan Bay Basin, UK)
Earth and Planetary Science Letters,
484396 – 411
2018
ISSN: 0012821X
Publisher: Elsevier B.V.
Keywords:▾
Cardigan Bay; United Kingdom; Wales; Carbon; Deposits; Geochemistry; Iron deposits; Iron ores; Isotopes; Sedimentology; Sulfur compounds; Trace elements; Weathering; Carbon isotope stratigraphy; Early Jurassic; Global weathering rates; Gravity flows; Oceanic anoxic events; siderite; biostratigraphy; carbon cycle; carbon isotope; deposition; depositional environment; evaporite; global climate; paleoceanography; paleotemperature; siderite; stratigraphy; sulfide; Toarcian; weathering; Stratigraphy
Abstract: ▾ The late Early Jurassic Toarcian Stage represents the warmest interval of the Jurassic Period, with an abrupt rise in global temperatures of up to ∼7 °C in mid-latitudes at the onset of the early Toarcian Oceanic Anoxic Event (T-OAE; ∼183 Ma). The T-OAE, which has been extensively studied in marine and continental successions from both hemispheres, was marked by the widespread expansion of anoxic and euxinic waters, geographically extensive deposition of organic-rich black shales, and climatic and environmental perturbations. Climatic and environmental processes following the T-OAE are, however, poorly known, largely due to a lack of study of stratigraphically well-constrained and complete sedimentary archives. Here, we present integrated geochemical and physical proxy data (high-resolution carbon-isotope data (δ13C), bulk and molecular organic geochemistry, inorganic petrology, mineral characterisation, and major- and trace-element concentrations) from the biostratigraphically complete and expanded entire Toarcian succession in the Llanbedr (Mochras Farm) Borehole, Cardigan Bay Basin, Wales, UK. With these data, we (1) construct the first high-resolution biostratigraphically calibrated chemostratigraphic reference record for nearly the complete Toarcian Stage, (2) establish palaeoceanographic and depositional conditions in the Cardigan Bay Basin, (3) show that the T-OAE in the hemipelagic Cardigan Bay Basin was marked by the occurrence of gravity-flow deposits that were likely linked to globally enhanced sediment fluxes to continental margins and deeper marine (shelf) basins, and (4) explore how early Toarcian (tenuicostatum and serpentinum zones) siderite formation in the Cardigan Bay Basin may have been linked to low global oceanic sulphate concentrations and elevated supply of iron (Fe) from the hinterland, in response to climatically induced changes in hydrological cycling, global weathering rates and large-scale sulphide and evaporite deposition. © 2017 The Authors
2062.
Dietary versatility of Early Pleistocene hominins
Proceedings of the National Academy of Sciences of the United States of America,
115
(52)
13330 – 13335
2018
ISSN: 00278424
Publisher: National Academy of Sciences
Keywords:▾
Adaptation, Physiological; Animals; Biological Evolution; Carbon Isotopes; Dental Enamel; Diet; Ecosystem; Environment; Feeding Behavior; Fossils; History, Ancient; Hominidae; carbon; adaptation; Article; C3 plant; diet; ecosystem; enamel; evolution; feeding behavior; fluid intake; fossil hominin; habitat; Homo rudolfensis; isotope analysis; Malawi; nonhuman; Paranthropus boisei; Pleistocene; priority journal; animal; chemistry; diet; environment; fossil; history; hominid; metabolism; physiology
Abstract: ▾ New geochemical data from the Malawi Rift (Chiwondo Beds, Karonga Basin) fill a major spatial gap in our knowledge of hominin adaptations on a continental scale. Oxygen (δ 18 O), carbon (δ 13 C), and clumped (Δ 47 ) isotope data on paleosols, hominins, and selected fauna elucidate an unexpected diversity in the Pleistocene hominin diet in the various habitats of the East African Rift System (EARS). Food sources of early Homo and Paranthropus thriving in relatively cool and wet wooded savanna ecosystems along the western shore of paleolake Malawi contained a large fraction of C 3 plant material. Complementary water consumption reconstructions suggest that ca. 2.4 Ma, early Homo (Homo rudolfensis) and Paranthropus (Paranthropus boisei) remained rather stationary near freshwater sources along the lake margins. Time-equivalent Paranthropus aethiopicus from the Eastern Rift further north in the EARS consumed a higher fraction of C 4 resources, an adaptation that grew more pronounced with increasing openness of the savanna setting after 2 Ma, while Homo maintained a high versatility. However, southern African Paranthropus robustus had, similar to the Malawi Rift individuals, C 3 -dominated feeding strategies throughout the Early Pleistocene. Collectively, the stable isotope and faunal data presented here document that early Homo and Paranthropus were dietary opportunists and able to cope with a wide range of paleohabitats, which clearly demonstrates their high behavioral flexibility in the African Early Pleistocene. © 2018 National Academy of Sciences. All Rights Reserved.
2061.
Dinosaur-killing asteroid impact made huge dead zones in oceans
Eos,
99
2018
2060.
Direct geometrical simulation of pore space evolution through hydrate dissociation in methane hydrate reservoirs
Marine and Petroleum Geology,
89786-798
2018
ISSN: 02648172
Publisher: Elsevier Ltd
Keywords:▾
Dissociation; Gas permeability; Grain size and shape; Hydration; Methane; Particle size; Porous materials; Sensitivity analysis; Size distribution, Absolute permeability; Effective permeability; Gas relative permeabilities; Geometrical simulations; Grain size distribution; Morphological simulation; Physical characteristics; Visualization and simulation, Gas hydrates, displacement; hydrocarbon reservoir; methane; microstructure; permeability; pore space; porous medium; sensitivity analysis
Abstract: ▾ The identification of methane hydrate behavior in porous media is one of the most challenging yet rewarding pore-level visualization and simulation tasks. The hydrate morphology influences the physical characteristics of the host sediments as during the hydrate formation and dissociation processes the pore space and flow pathways constantly evolve. Here, a direct three-phase pore morphological simulation approach is proposed, verified and utilized to simulate hydrate deformities and predict fluid occupancies and absolute and effective permeabilities of hydrate-bearing geological formations. The proposed technique simulates capillary-dominant displacements by applying a set of geomaterial rules directly to the pixels of pore-level porous media images. The case studies are sandy microstructures generated based on the particle size distributions of the Mallik gas hydrate deposit. The fluid occupancy profiles, absolute permeability, and hydraulic tortuosity curves are comparable with the experimental datasets. The sensitivity analysis shows that although the gas relative permeability is less sensitive to the hydrate specifications, the porosity, grain size distribution, and hydrate content and occupancy remarkably influence the rock absolute permeability. © 2017 Elsevier Ltd
2059.
Diurnal Course of Evaporation From the Dead Sea in Summer: A Distinct Double Peak Induced by Solar Radiation and Night Sea Breeze
Water Resources Research,
54
(1)
150 – 160
2018
2058.
Drilling-induced and logging-related features illustrated from IODP-ICDP Expedition 364 downhole logs and borehole imaging tools
Scientific Drilling,
241-13
2018
Abstract: ▾ Expedition 364 was a joint IODP and ICDP mission-specific platform (MSP) expedition to explore the Chicxulub impact crater buried below the surface of the Yucatán continental shelf seafloor. In April and May 2016, this expedition drilled a single borehole at Site M0077 into the crater's peak ring. Excellent quality cores were recovered from ~ 505 to ~1335m below seafloor (m b.s.f.), and high-resolution open hole logs were acquired between the surface and total drill depth. Downhole logs are used to image the borehole wall, measure the physical properties of rocks that surround the borehole, and assess borehole quality during drilling and coring operations. When making geological interpretations of downhole logs, it is essential to be able to distinguish between features that are geological and those that are operation-related. During Expedition 364 some drilling-induced and logging-related features were observed and include the following: effects caused by the presence of casing and metal debris in the hole, logging-tool eccentering, drilling-induced corkscrew shape of the hole, possible re-magnetization of low-coercivity grains within sedimentary rocks, markings on the borehole wall, and drilling-induced changes in the borehole diameter and trajectory. © Author(s) 2018.
2057.
Dynamics of microseismicity and its relationship with the active structures in the western Corinth Rift (Greece)
Geophysical Journal International,
215
(1)
196 – 221
2018
ISSN: 0956540X
Publisher: Oxford University Press
Keywords:▾
Corinth Rift; Greece; Ionian Sea; Mediterranean Sea; Database systems; Earthquakes; Pore pressure; Signal to noise ratio; Cross-correlation coefficient; Double-difference technique; Earthquake dynamics; Europe; Pressure variations; Seismicity and tectonics; Transient deformation; Waveform similarity; deformation; earthquake mechanism; normal fault; rift zone; seismic migration; seismicity; signal-to-noise ratio; tectonics; wave velocity; waveform analysis; Fault slips
Abstract: ▾ We analyse the complete earthquake archive of the western Corinth Rift using both crosscorrelations between pairs of event waveforms and accurate differential traveltimes observed at common stations, in order to identify small-scale fault structures at depth. The waveform database was generated by the dense Corinth Rift Laboratory network and includes about 205 000 events between 2000 and 2015. Half of them are accurately relocated using doubledifference techniques. The novelty of this relocated catalogue is the integration of the recent westernmost earthquakes due to the extension of the network in 2010 to the western extremity of the Corinth Rift and the consideration of the whole database over more than 15 yr. The total relocated seismicity exhibits well-defined clusters at the root of the main normal faults mainly between 5 and 10 km depth in the middle of the gulf and illuminates thin active structure planes dipping north about 20° under the northern coast. Some seismicity is observed in the footwall of the main active faults, along theWest and East Helike faults.We also built a multiplet database based on waveform similarity taking into account cross-correlation coefficients weighted by signal-to-noise ratios. Short-termmultiplets are concentrated in the middle of the gulf along the Kamarai fault system, in a 1-2 km thick layer at 6-8 km depth, interpreted as a highly fractured geological layer. They are often associated to slow seismic migration velocities occurring in this zone during strong swarm episodes and are thus likely to be triggered by pore pressure variations. On the other hand, most long-term and regular multiplets are located deeper (7- 10 km), under the northern coast, within a layer less than 0.3 km thick. They occur at the border of nearly planar structures with low seismicity rate, which we identify as fault planes, and they may be explained by aseismic slip on the fault surface around them. This supports the existence of an immature structure growing downdip towards the north at the base of the active geological layer, which possibly connects to the ductile middle crust around 15 km depth, as suggested by the occurrence of deeper events in the continuity of the 1995-fault plane. The different migration velocities (from 0.05 km d-1 to several km d-1) highlighted during the western 2014-swarms indicate that both pore pressure and creep diffusion are operating in the fault zone. The fast migrations observed in the Psathopyrgos fault zone, where a slow slip event was detected by dilatometers in 2002, compare with that for creeping faults. To the west, from spatial distribution of events, we show that the Rion-Patras fault connecting the western extremity of the Corinth Rift fault system to the Patras Rift, is dipping around 60° north-west with a rake angle of -115°. Finally, we identified two new areas within the central active zone which may correspond to large scale, locked asperities on active fault surfaces, similar in size to the main asperity broken during the 1995, MW 6.3, Aigion earthquake. © The Author(s) 2018.
2056.
Environmental change during MIS4 and MIS 3 opened corridors in the Horn of Africa for Homo sapiens expansion
Quaternary Science Reviews,
202139 – 153
2018
ISSN: 02773791
Publisher: Elsevier Ltd
Keywords:▾
Geology, Archaeological findings; Climatic conditions; Eastern Mediterranean; Environmental change; Genome analysis; Humid periods; Lake sediment cores; Rapid shifts, Natural sciences, anatomy; archaeology; aridity; climate conditions; dispersal; environmental change; horn; lacustrine deposit; marine isotope stage; sediment core, Arabian Sea; Ethiopia; Indian Ocean; Levantine Sea; Mediterranean Sea; Mediterranean Sea (East), Homo sapiens
Abstract: ▾ Archaeological findings, numerical human dispersal models and genome analyses suggest several time windows in the past 200 kyr (thousands of years ago) when anatomically modern humans (AMH) dispersed out of Africa into the Levant and/or Arabia. From close to the key hominin site of Omo-Kibish, we provide near continuous proxy evidence for environmental changes in lake sediment cores from the Chew Bahir basin, south Ethiopia. The data show highly variable hydroclimate conditions from 116 to 66 kyr BP with rapid shifts from very wet to extreme aridity. The wet phases coincide with the timing of the North African Humid Periods during MIS5, as defined by Nile discharge records from the eastern Mediterranean. The subsequent record at Chew Bahir suggests stable regional hydrological setting between 58 and 32 kyr (MIS4 and 3), which facilitated the development of more habitable ecosystems, albeit in generally dry climatic conditions. This shift, from more to less variable hydroclimate, may help account for the timing of later dispersal events of AMH out of Africa. © 2018 The Authors
2055.
Evaluating Late Cretaceous OAEs and the influence of marine incursions on organic carbon burial in an expansive East Asian paleo-lake
Earth and Planetary Science Letters,
48441-52
2018
ISSN: 0012821X
Publisher: Elsevier B.V.
Keywords:▾
Biogeochemistry; Isotopes; Lakes; Petroleum geology; Stratigraphy; Weathering, Biogeochemical cycling; Chemostratigraphy; Oceanic Anoxic Event; Osmium isotopes; Paleoclimates; Songliao basin, Organic carbon, anoxic conditions; biogeochemical cycle; carbon isotope; chemostratigraphy; Cretaceous; lacustrine deposit; mudstone; organic carbon; osmium isotope; paleoclimate; paleoenvironment, China; Songliao Basin; Western Interior
Abstract: ▾ Expansive Late Cretaceous lacustrine deposits of East Asia offer unique stratigraphic records to better understand regional responses to global climate events, such as oceanic anoxic events (OAEs), and terrestrial organic carbon burial dynamics. This study presents bulk organic carbon isotopes (δ13Corg), elemental concentrations (XRF), and initial osmium ratios (187Os/188Os, Osi) from the Turonian–Coniacian Qingshankou Formation, a ∼5 Ma lacustrine mudstone succession in the Songliao Basin of northeast China. A notable δ13Corg excursion (∼+2.5‰) in organic carbon-lean Qingshankou Members 2–3 correlates to OAE3 in the Western Interior Basin (WIB) of North America within temporal uncertainty of high-precision age models. Decreases in carbon isotopic fractionation (Δ13C) through OAE3 in the WIB and Songliao Basin, suggest that significantly elevated global rates of organic carbon burial drew down pCO2, likely cooling climate. Despite this, Osi chemostratigraphy demonstrates no major changes in global volcanism or weathering trends through OAE3. Identification of OAE3 in a lake system is consistent with lacustrine records of other OAEs (e.g., Toarcian OAE), and underscores that terrestrial environments were sensitive to climate perturbations associated with OAEs. Additionally, the relatively radiogenic Osi chemostratigraphy and XRF data confirm that the Qingshankou Formation was deposited in a non-marine setting. Organic carbon-rich intervals preserve no compelling Osi evidence for marine incursions, an existing hypothesis for generating Member 1's prolific petroleum source rocks. Based on our results, we present a model for water column stratification and source rock deposition independent of marine incursions, detailing dominant biogeochemical cycles and lacustrine organic carbon burial mechanisms. © 2017 Elsevier B.V.
2054.
Evidence for carbon cycling in a large freshwater lake in the Balkans over the last 0.5 million years using the isotopic composition of bulk organic matter
Quaternary Science Reviews,
202154 – 165
2018
ISSN: 02773791
Publisher: Elsevier Ltd
Keywords:▾
Balkans; Lake Ohrid; Biogeochemistry; Biological materials; Carbon dioxide; Groundwater; Isotopes; Lakes; Paleolimnology; Recycling; Springs (components); Springs (water); Carbon isotope composition; Dissolved inorganic carbon; Europe; Lake Ohrid; Organic matter recycling; Pleistocene; Stable isotopes; Total inorganic carbon; carbon cycle; carbon isotope; freshwater environment; glacial-interglacial cycle; isotopic composition; karst; lacustrine environment; lake water; methanogenesis; paleolimnology; Pleistocene; primary production; spring water; stratification; Organic carbon
Abstract: ▾ In the DEEP core from the Lake Ohrid ICDP drilling project, the carbon isotope composition of bulk organic matter (δ13CTOC) over the last 516 ka shows a negative correlation with total organic carbon (TOC) and total inorganic carbon (TIC). This relationship is marked by periods of lower δ13CTOC values corresponding to higher TIC and TOC. Along with TOC/TN, the correlation between δ13CTOC and δ13CTIC suggests that most of the organic matter in the core is from aquatic primary production within the lake. The combination of TOC, TIC, and δ13CTOC is able to disentangle long-term glacial/interglacial cycles and, to a lesser extent, millennial scale climate variability. Over the longer term, δ13CTOC shows modest variability, indicating that the δ13C of the dissolved inorganic carbon (DIC) pool is stabilised by the supply of karst spring water characterised by δ13CDIC influenced by the bedrock δ13C value, and the long residence time of the lake water and well mixed upper water column promoting equilibration with atmospheric CO2. However, comparison between arboreal pollen (AP%), TIC and TOC data indicates that the δ13CTOC signal is modulated by the leaching of soil CO2 through runoff and spring discharge, changes in primary productivity, and recycling of organic matter within the lake, all affecting δ13CDIC. Exceptionally low δ13CTOC during some interglacial periods (e.g. MIS7 and MIS9) possibly indicate rapid intensification of organic matter recycling and/or increasing stratification and enhanced methanogenesis, even if the latter process is not supported by the sedimentological data. © 2018 Elsevier Ltd
2053.
Evidence for cyclical fractional crystallization, recharge, and assimilation in basalts of the kimama drill core, central snake river plain, idaho: 5.5-million-years of petrogenesis in a mid-crustal sill complex
Frontiers in Earth Science,
6
2018
ISSN: 22966463
Publisher: Frontiers Media S.A.
Keywords:▾
Basalt; Binary alloys; Drills; Infill drilling; Iron alloys; Moon; Olivine; Petrology; Rivers; Titanium alloys; Trace elements, Chemical compositions; Chemical heterogeneities; Drill core; Fractional crystallization; Geochemical variations; Mid-crustal sill complex; Snake river plains; Tholeiite, Core drilling, basalt; crystal structure; data assimilation; fractional crystallization; hydrothermal alteration; magma; petrogenesis; petrology; tholeiitic basalt, Idaho; Snake River Plain; United States
Abstract: ▾ Basalts erupted in the Snake River Plain of central Idaho and sampled in the Kimama drill core link eruptive processes to the construction of mafic intrusions over 5.5Ma. Cyclic variations in basalt composition reveal temporal chemical heterogeneity related to fractional crystallization and the assimilation of previously-intruded mafic sills. A range of compositional types are identified within 1,912m of continuous drill core: Snake River olivine tholeiite (SROT), low K SROT, high Fe-Ti, and evolved and high K-Fe lavas similar to those erupted at Craters of the Moon National Monument. Detailed lithologic and geophysical logs document 432 flow units comprising 183 distinct lava flows and 78 flowgroups. Each lava flowrepresents a single eruptive episode, while flow groups document chemically and temporally related flows that formed over extended periods of time. Temporal chemical variation demonstrates the importance of source heterogeneity and magma processing in basalt petrogenesis. Low-K SROT and high Fe-Ti basalts are genetically related to SROT as, respectively, hydrothermally-altered and fractionated daughters. Cyclic variations in the chemical composition of Kimama flow groups are apparent as 21 upward fractionation cycles, six recharge cycles, eight recharge-fractionation cycles, and five fractionation-recharge cycles. We propose that most Kimama basalt flows represent typical fractionation and recharge patterns, consistent with the repeated influx of primitive SROT parental magmas and extensive fractional crystallization coupled with varying degrees of assimilation of gabbroic to ferrodioritic sills at shallow to intermediate depths over short durations. Trace element models show that parental SROT basalts were generated by 5–10% partial melting of enriched mantle at shallow depths above the garnet-spinel lherzolite transition. The distinctive evolved and high K-Fe lavas are rare. Found at four depths, 319, 1045, 1,078, and 1,189m, evolved and high K-Fe flows are compositionally unrelated to SROT magmas and represent highly fractionated basalt, probably accompanied by crustal assimilation. These evolved lavas may be sourced from the Craters of the Moon/Great Rift system to the northeast. The Kimama drill core is the longest record of geochemical variation in the central Snake River Plain and reinforces the concept of magma processing in a layered complex. © 2018 Potter, Shervais, Christiansen and Vetter.
2052.
Evolution of atmospheric xenon and other noble gases inferred from Archean to Paleoproterozoic rocks
Geochimica et Cosmochimica Acta,
23282 – 100
2018
ISSN: 00167037
Publisher: Elsevier Ltd
Keywords:▾
Archean; atmospheric chemistry; fluid inclusion; isotopic composition; isotopic fractionation; nitrogen isotope; paleoatmosphere; Proterozoic; xenon
Abstract: ▾ We have analyzed ancient atmospheric gases trapped in fluid inclusions contained in minerals of Archean (3.3 Ga) to Paleozoic (404 Ma) rocks in an attempt to document the evolution of the elemental composition and isotopic signature of the atmosphere with time. Doing so, we aimed at understanding how physical and chemical processes acted over geological time to shape the modern atmosphere. Modern atmospheric xenon is enriched in heavy isotopes by 30–40‰ u−1 relative to Solar or Chondritic xenon. Previous studies demonstrated that, 3.3 Ga ago, atmospheric xenon was isotopically fractionated (enriched in the light isotopes) relative to the modern atmosphere, by 12.9 ± 1.2 (1σ) ‰ u−1, whereas krypton was isotopically identical to modern atmospheric Kr. Details about the specific and progressive isotopic fractionation of Xe during the Archean, originally proposed by Pujol et al. (2011), are now well established by this work. Xe isotope fractionation has evolved from 21‰ u−1 at 3.5 Ga to 12.9‰ u−1 at 3.3 Ga. The current dataset provides some evidence for stabilization of the Xe fractionation between 3.3 and 2.7 Ga. However, further studies will be needed to confirm this observation. After 2.7 Ga, the composition kept evolving and reach the modern-like atmospheric Xe composition at around 2.1 Ga ago. Xenon may be the second atmospheric element, after sulfur, to show a secular isotope evolution during the Archean that ended shortly after the Archean-Proterozoic transition. Fractionation of xenon indicates that xenon escaped from Earth, probably as an ion, and that Xe escape stopped when the atmosphere became oxygen-rich. We speculate that the Xe escape was enabled by a vigorous hydrogen escape on the early anoxic Earth. Organic hazes, scavenging isotopically heavy Xe, could also have played a role in the evolution of atmospheric Xe. For 3.3 Ga-old samples, Ar-N2 correlations are consistent with a partial pressure of nitrogen (pN2) in the Archean atmosphere similar to, or lower than, the modern one, thus requiring other processes than a high pN2 to keep the Earth's surface warm despite a fainter Sun. The nitrogen isotope composition of the atmosphere at 3.3 Ga was already modern-like, attesting to inefficient nitrogen escape to space since that time. © 2018 The Authors
2051.
Real‐Time Earthquake Monitoring during the Second Phase of the Deep Fault Drilling Project, Alpine Fault, New Zealand
Seismological Research Letters,
88
(6)
1443-1454
092017
ISSN: 0895-0695Abstract: ▾ The Deep Fault Drilling Project (DFDP) is a multinational scientific drilling effort to study the evolution, structure, and seismogenesis of the Alpine fault, New Zealand, via in situ measurements of fault rock properties. The second phase of drilling (DFDP‐2), undertaken in the Whataroa Valley in late 2014, was intended to intersect the Alpine fault at a depth of around 1 km. In conjunction with the drilling and on‐site science activities, a real‐time seismic monitoring scheme and traffic‐light response protocol were established to detect, locate, and if necessary respond to seismicity within 30 km of the drill site. This network was operated around the clock between late August 2014 and early January 2015, and we detected and located 493 earthquakes of ML 0.6–4.2. None of these earthquakes occurred within 3 km of the drill site, and nor did any of the seismicity detected require changes to drilling operations. The monitoring was undertaken using open‐source software operated by an international team of 16 seismologists (including eight postgraduate students) working in 7 institutions and 3 countries to provide rapid on‐ and off‐site manual checking and relocating of events. The team’s standard response time between detection and final location was less than 30 min under normal background seismicity conditions and up to 1 hr during swarm activity and for low‐priority, distant (≥30 km epicentrally from the drill site) earthquakes. This article documents the methodology, infrastructure, protocols, outcomes, and key lessons of this monitoring.
2050.
Rates and cycles of microbial sulfate reduction in the hyper-saline dead sea over the last 200 kyrs from sedimentary δ34 S and δ18 O(SO4)
Frontiers in Earth Science,
5
2017
ISSN: 22966463
Publisher: Frontiers Media S.A.
Keywords:▾
Glacial geology; Gypsum; Lakes; Metabolism; Oxidation; Oxygen; Paleolimnology; Pyrites; Sedimentology, Dead sea; Isotope fractionation; Sulfate reduction; Sulfates; Sulfide oxidation, Sulfur compounds, gypsum; outcrop; oxygen isotope; pyrite; sediment core; sulfate-reducing bacterium; sulfur, Dead Sea
Abstract: ▾ We report the δ34 S and δ18 O(SO4) measured in gypsum, pyrite, and elemental sulfur through a 456-m thick sediment core from the center of the Dead Sea, representing the last ∼200 kyrs, as well as from the exposed glacial outcrops of the Masada M1 section located on the margins of the modern Dead Sea. The results are used to explore and quantify the evolution of sulfur microbial metabolism in the Dead Sea and to reconstruct the lake’s water column configuration during the late Quaternary. Layers and laminae of primary gypsum, the main sulfur-bearing mineral in the sedimentary column, display the highest δ34 S and δ18 O(SO4) in the range of 13–28 and 13–30%, respectively. Within this group, gypsum layers deposited during interglacials display lower δ34 S and δ18 O(SO4) relative to those associated with glacial or deglacial stages. The reduced sulfur phases, including chromiumreducible sulfur, andsecondary gypsumcrystals are characterizedby extremely low δ34 S in the range of −27 to +7%. The δ18 O(SO4) of the secondary gypsum in the M1 outcrop ranges from 8 to 14%. The relationship between δ34 S and δ18 O(SO4) of primary gypsumsuggests that the rate of microbial sulfate reduction was lower during glacial relative to interglacial times. This suggests that the freshening of the lake during glacial wet intervals, and the subsequent rise in sulfate concentrations, slowed the rate of microbial metabolism. Alternatively, this could imply that sulfate-driven anaerobic methane oxidation, the dominant sulfur microbial metabolism today, is a feature of the hypersalinity in the modern Dead Sea. Sedimentary sulfides are quantitatively oxidized during epigenetic exposure, retaining the lower δ34 S signature; the δ18 O(SO4) of this secondary gypsum is controlled by oxygen atoms derived equally from atmospheric oxygen and from water, which is likely a unique feature in this hyperarid environment. © 2017 Torfstein and Turchyn.
2049.
Radiocarbon chronology of the dsddp core at the deepest floor of the dead sea
Radiocarbon,
59
(2)
383-394
2017
ISSN: 00338222
Publisher: Cambridge University Press
Keywords:▾
carbon isotope; chronology; Deep Sea Drilling Project; lacustrine environment; lake level; radiocarbon dating; sedimentary sequence; terrestrial environment, Dead Sea
Abstract: ▾ This study establishes the chronological framework of the sedimentary sequence deposited Dead Sea, ICDP 5017-1, Radiocarbon chronology during the past 50 ka at the deepest part of the Dead Sea (the ICDP 5017-1 site), which was recovered by the Dead Sea Deep Drilling Project (DSDDP) under the auspices of the International Continental Scientific Drilling Program (ICDP). The age-depth model is constructed using 3814C dates of terrestrial plant remains in a composite 150-m-long profile, generated by anchoring 32 marker layers identified in five cores. The sedimentary records at the ICDP 5017-1 site fills gaps in those obtained from the exposed sections at the high margins of the lake, particularly in times of lake-level retreat, and allows for a high-resolution comparison between the lake’s margins and deepest floor. © 2017 by the Arizona Board of Regents on behalf of the University of Arizona.
2048.
Sedimentology, stratigraphic context, and implications of Miocene intrashelf bottomset deposits, offshore New Jersey
Geosphere,
14
(1)
95-114
2017
ISSN: 1553040X
Publisher: Geological Society of America
Keywords:▾
Erosion; Ocean currents; Offshore drilling; Sea level; Sediment transport; Sedimentology; Sediments; Stratigraphy; Thin walled structures; Turbidity, Benthic foraminifera; Compensational stacking; Highstand systems tract; Integrated ocean drilling programs; Maximum flooding surfaces; Sediment gravity flow; Sequence-stratigraphic interpretation; Stratigraphic organizations, Deposits, chronostratigraphy; debris flow; Miocene; quartz; sediment transport; sedimentology, New Jersey; United States, Foraminifera
Abstract: ▾ Drilling of intrashelf Miocene clinothems onshore and offshore New Jersey has provided better understanding of their topset and foreset deposits, but the sedimentology and stratigraphy of their bottomset deposits have not been documented in detail. Three coreholes (Sites M27-M29), collected during Integrated Ocean Drilling Program (IODP) Expedition 313, intersect multiple bottomset deposits, and their analysis helps to refine sequence stratigraphic interpretations and process response models for intrashelf clinothems. At Site M29, the most downdip location, chronostratigraphically well-constrained bottomset deposits follow a repeated stratigraphic motif. Coarse-grained glauconitic quartz sand packages abruptly overlie deeply burrowed surfaces. Typically, these packages coarsen then fine upwards and pass upward into bioturbated siltstones. These coarse sand beds are amalgamated and poorly sorted and contain thin-walled shells, benthic foraminifera, and extrabasinal clasts, consistent with an interpretation of debrites. The sedimentology and mounded seismic character of these packages support interpretation as debrite-dominated lobe complexes. Farther updip, at Site M28, the same chronostratigraphic units are amalgamated, with the absence of bioturbated silts pointing to more erosion in proximal locations. Graded sandstones and dune-scale cross-bedding in the younger sequences in Site M28 indicate deposition from turbidity currents and channelization. The sharp base of each package is interpreted as a sequence boundary, with a period of erosion and sediment bypass evidenced by the burrowed surface, and the coarse-grained debritic and turbiditic deposits representing the lowstand systems tract. The overlying fine-grained deposits are interpreted as the combined transgressive and highstand systems tract deposits and contain the deepwater equivalent of the maximum flooding surface. The variety in thickness and grain-size trends in the coarse-grained bottomset packages point to an autogenic control, through compensational stacking of lobes and lobe complexes. However, the large-scale stratigraphic organization of the bottomset deposits and the coarse-grained immature extrabasinal and reworked glauconitic detritus point to external controls, likely a combination of relative sea-level fall and waxing- and-waning cycles of sediment supply. This study demonstrates that large amounts of sediment gravity-flow deposits can be generated in relatively shallow (~100-200 m deep) and low-gradient (~1°-4°) clinothems that prograded across a deep continental shelf. This physiography likely led to the dominance of debris flow deposits due to the short transport distance limiting transformation to low-concentration turbidity currents. © 2017 The Authors.
2047.
Quantifying the Release of Climate-Active Gases by Large Meteorite Impacts With a Case Study of Chicxulub
Geophysical Research Letters,
44
(20)
10,180-10,188
2017
Abstract: ▾ Potentially hazardous asteroids and comets have hit Earth throughout its history, with catastrophic consequences in the case of the Chicxulub impact. Here we reexamine one of the mechanisms that allow an impact to have a global effect—the release of climate-active gases from sedimentary rocks. We use the SOVA hydrocode and model ejected materials for a sufficient time after impact to quantify the volume of gases that reach high enough altitudes (> 25 km) to have global consequences. We vary impact angle, sediment thickness and porosity, water depth, and shock pressure for devolatilization and present the results in a dimensionless form so that the released gases can be estimated for any impact into a sedimentary target. Using new constraints on the Chicxulub impact angle and target composition, we estimate that 325 ± 130 Gt of sulfur and 425 ± 160 Gt CO2 were ejected and produced severe changes to the global climate. ©2017. American Geophysical Union. All Rights Reserved.
2046.
Pyrite in a sulfate-poor Paleoarchean basin was derived predominantly from elemental sulfur: Evidence from 3.2 Ga sediments in the Barberton Greenstone Belt, Kaapvaal Craton
Chemical Geology,
449135 – 146
2017
ISSN: 00092541
Publisher: Elsevier B.V.
Keywords:▾
Barberton Greenstone Belt; Kaapvaal Craton; Ficus (angiosperm); Earth atmosphere; Iron; Iron oxides; Isotopes; Oxide minerals; Photolysis; Redox reactions; Sedimentary rocks; Sedimentology; Sulfur; Sulfur compounds; Composition of the Earth; Fe isotopes; Greenstone belts; Low sulfate concentrations; Multiple sulfur isotopes; Paleoarchean; Reactive transport modeling; S isotopes; Archean; iron; isotopic fractionation; pyrite; sediment chemistry; sedimentary rock; sulfate; sulfur; sulfur isotope; Pyrites
Abstract: ▾ Multiple sulfur isotope variability in Archean sedimentary rocks provides constraints on the composition of the Earth's earliest atmosphere. The magnitude and sign of mass-independent anomalies reflect not only atmospheric processes, but also transformations due to the Archean marine sulfur cycle prior to preservation into sedimentary pyrite. The processes affecting the Archean marine sulfur cycle and the role of microbial or abiotic redox reactions during pyrite formation remain unclear. Here we combine iron (Fe) and multiple sulfur (S) isotope data in individual pyrite grains with petrographic information and a one-dimensional reactive transport model, to investigate the sources of Fe and S in pyrite formed in a Paleoarchean sedimentary basin. Pyrites were selected from mudstones, sandstones and chert obtained from a drill core in the ca. 3.2 Ga Mapepe and Mendon Formations of the Fig Tree and Onverwacht Groups, respectively, in the Barberton Greenstone Belt, Kaapvaal Craton, South Africa. Pyrite textures and δ56Fe distinguish early-diagenetic pyrite formed with pore-water ferrous iron (disseminated grains with average δ56Fepyrite = 0‰) from late-diagenetic pyrite formed through sulfidation of iron oxide minerals (layered and aggregate forms with average δ56Fepyrite = + 1‰). Mass dependent S isotope variability in pyrite was small (δ34Spyrite ranged from − 1.1 to + 3.3‰) with a correspondingly minor spread in Δ33Spyrite (ranging from + 0.3 to + 2.1‰) and Δ36Spyrite (ranging from − 3.08 to + 0.27‰) that indicates a lack of post-depositional re-working with other distinct sulfur sources. Our combined Fe and S isotope data are most readily explained with pyrite sulfide derived from microbial-reworking of solid elemental S. Iron oxide minerals were necessary to buffer sulfide concentrations and provide favorable conditions for microbial sulfur disproportionation to proceed. The lack of a negative Δ33S signal indicates that pyrite from relatively deep marine diagenetic environments only partially records the products of atmospheric photolysis, consistent with low sulfate concentrations in the Paleoarchean ocean. © 2016
2045.
Progress in the study of paleoclimate change in continental scientific drilling projects
Earth Science Frontiers,
24
(1)
229 – 241
2017
ISSN: 10052321
Publisher: Science Frontiers editorial department
Keywords:▾
Greenhouses; Sedimentology; Continental scientific drillings; Greenhouse climates; Paleoclimate studies; Paleoclimates; Paleoclimatic reconstruction; Paleoclimatic record; Rapid climate change; Sedimentary records; Climate change
Abstract: ▾ Today climate change has caused extensive concern of the whole society. Paleoclimate change studies in geological time (including Quaternary and “Deep Time”), in which continental scientific drilling plays a significant role, provide important references to the current climate change. This paper reviews scientific progresses in the study of paleoclimate change in continental scientific drilling projects. In advantage of the continuous sedimentary records acquired by the continental scientific drilling projects, high-resolution chronostratigraphic framework is established and multiple paleoclimatic proxies are applied. With the aim to decipher the process and mechanism of climate change, progresses have been achieved on paleoclimatic reconstructions on different timescales, detailed studies on rapid climate changes, and precise correlation between marine and terrestrial paleoclimatic records. It is predictable that continental scientific drilling will be more influential in the paleoclimate studies in future, especially in deep-time greenhouse climate studies. © 2017, Editorial Office of Earth Science Frontiers. All right reserved.