All ICDP Publications with Abstracts
From parent-sysfolder "Publications" + 2 folder-levels deep
1894.
Seismic-wave propagation in shallow layers at the GONAF-tuzla site, Istanbul, Turkey
Bulletin of the Seismological Society of America,
106
(3)
912 – 927
2016
ISSN: 00371106
Publisher: Seismological Society of America
Keywords:▾
Istanbul [Turkey]; Turkey; Tuzla [Istanbul]; Seismic waves; Seismology; Shear waves; Time domain analysis; Wave propagation; Well logging; Impedance contrast; Interference effects; Istanbul , Turkey; Low velocity layers; Low velocity zones; North Anatolian Fault; Observation point; P- and S-wave velocities; Green function; North Anatolian Fault; P-wave; S-wave; seismic wave; seismogram; shallow water; wave propagation; wave velocity; Velocity
Abstract: ▾ Using the first dataset available from the downhole Geophysical Observatory of the North Anatolian Fault, we investigated near-surface seismic-wave propagation on the Tuzla Peninsula, Istanbul, Turkey. We selected a dataset of 26 seismograms recorded at Tuzla at sensor depths of 0, 71, 144, 215, and 288 m. To determine near-surface velocities and attenuation structures, the waveforms from all sensors were pairwise deconvolved and stacked. This produced low-noise empirical Green’s functions for each borehole depth interval. From the Green’s functions, we identified reflections from the free surface and a low-velocity layer between ∼90 and ∼140 m depth. The presence of a low-velocity zone was also confirmed by a sonic log run in the borehole. This structure, plus high near-surface P- and S-wave velocities of ∼3600–4100 and ∼1800 m=s, lead to complex interference effects between upgoing and downgoing waves. As a result, the determination of quality factors (Q) with standard spectral ratio techniques was not possible. Instead, we forward modeled the Green’s functions in the time domain to determine effective Q values and to refine our velocity estimates. The effective QPvalues for the depth intervals of 0–71, 0–144, 0–215, and 0–288 m were found to be 19, 35, 39, and 42, respectively. For the S waves, we obtained an effective QS of 20 in the depth interval of 0–288 m. Considering the assumptions made in our modeling approach, it is evident that these effective quality factors are biased by impedance contrasts between our observation points. Our results show that, even after correcting for a free-surface factor of 2, the motion at the surface was found to be 1.7 times greater than that at 71 m depth. Our efforts also illustrate some of the difficulties of dealing with site effects in a strongly heterogeneous subsurface. © 2016, Seismological Society of America. All rights reserved.
1893.
Relationship between total organic carbon content and sedimentation rate of the Upper Cretaceous source rocks in Well CCSD-SK-1n Songliao Basin (in Chinese with English abstract); [松辽盆地松科1井上白垩统烃源岩有机碳含量与沉积速率的关系]
Journal of Palaeogeography,
18
(5)
857-864
2016
1892.
Origin and diversification of Lake Ohrid's endemic acroloxid limpets: the role of geography and ecology
BMC Evolutionary Biology,
16
(1)
1 – 13
2016
ISSN: 14712148
Publisher: BioMed Central
Keywords:▾
Animals; Biodiversity; DNA, Mitochondrial; Ecosystem; Europe; Genetic Speciation; Lakes; Models, Biological; Phylogeny; Phylogeography; Sequence Analysis, DNA; Snails; Albania; Balkan; Lake Ohrid; Macedonia [Southern Europe]; Turkmenistan; Acroloxidae; Acroloxus; Gastropoda; Invertebrata; Mya; Patellidae; mitochondrial DNA; biodiversity; divergence; endemic species; genetic differentiation; lacustrine environment; molecular ecology; morphology; origin of life; phylogenetics; phylogeny; phylogeography; snail; speciation (biology); vertical distribution; animal; biodiversity; biological model; DNA sequence; ecosystem; Europe; genetics; lake; phylogeny; phylogeography; snail; species differentiation
Abstract: ▾ Background: Ancient Lake Ohrid, located on the Albania-Macedonia border, is the most biodiverse freshwater lake in Europe. However, the processes that gave rise to its extraordinary endemic biodiversity, particularly in the species-rich gastropods, are still poorly understood. A suitable model taxon to study speciation processes in Lake Ohrid is the pulmonate snail genus Acroloxus, which comprises two morphologically distinct and ecologically (vertically) separated endemic species. Using a multilocus phylogenetic framework of Acroloxus limpets from the Euro-Mediterranean subregion, together with molecular-clock and phylogeographic analyses of Ohrid taxa, we aimed to infer their geographic origin and the timing of colonization as well as the role of geography and ecology in intra-lacustrine diversification. Results: In contrast to most other endemic invertebrate groups in Lake Ohrid, the phylogenetic relationships of the endemic Ohrid Acroloxus species indicate that the Balkan region probably did not serve as their ancestral area. The inferred monophyly and estimated divergence times further suggest that these freshwater limpets colonized the lake only once and that the onset of intra-lacustrine diversification coincides with the time when the lake reached deep-water conditions ca 1.3 Mya. However, the difference in vertical distribution of these two ecologically distinct species is not reflected in the phylogeographic pattern observed. Instead, western and eastern populations are genetically more distinct, suggesting a horizontal structure. Conclusions: We conclude that both geography and ecology have played a role in the intra-lacustrine speciation process. Given the distinct morphology (sculptured vs. smooth shell) and ecology (littoral vs. sublittoral), and the timing of intra-lacustrine diversification inferred, we propose that the onset of deep-water conditions initially triggered ecological speciation. Subsequent geographic processes then gave rise to the phylogeographic patterns observed today. However, the generally weak genetic differentiation observed suggests incipient speciation, which might be explained by the comparatively young age of the lake system and thus the relatively recent onset of intra-lacustrine diversification. © 2016 The Author(s).
1891.
Recording of climate and diagenesis through sedimentary DNA and fossil pigments at Laguna Potrok Aike, Argentina
Biogeosciences,
13
(8)
2475 – 2492
2016
1890.
Propidium monoazide treatment to distinguish between live and dead methanogens in pure cultures and environmental samples
Journal of Microbiological Methods,
12111-23
2016
ISSN: 01677012
Publisher: Elsevier
Keywords:▾
DNA; dye; propidium monoazide; unclassified drug; azide; bacterial DNA; humic substance; intercalating agent; propidium iodide; propidium monoazide; soil, Article; bacterial strain; cell membrane; cell viability; clay rich sediment; controlled study; culture technique; denaturing gradient gel electrophoresis; diagnostic kit; environment; feasibility study; fluorescence; humic substance; led light; light; membrane permeability; methanogenic archaeon; microscopy; nonhuman; particle rich environmental sample; particle size; photoactivation; polymerase chain reaction; priority journal; quantitative analysis; sandy soil; sediment; silt sediment; soil texture; suspended particulate matter; turbidity; analogs and derivatives; analysis; chemistry; classification; drug effects; Euryarchaeota; fluorescence microscopy; genetics; humic substance; isolation and purification; microbial viability; microbiological examination; microbiology; procedures; soil, Azides; Bacteriological Techniques; DNA, Bacterial; Environmental Microbiology; Euryarchaeota; Humic Substances; Intercalating Agents; Microbial Viability; Microscopy, Fluorescence; Polymerase Chain Reaction; Propidium; Soil; Soil Microbiology
Abstract: ▾ In clinical trials investigating human health and in the analysis of microbial communities in cultures and natural environments, it is a substantial challenge to differentiate between living, potentially active communities and dead cells. The DNA-intercalating dye propidium monoazide (PMA) enables the selective masking of DNA from dead, membrane-compromised cells immediately before DNA extraction. In the present study, we evaluated for the first time a PMA treatment for methanogenic archaea in cultures and particle-rich environmental samples. Using microscopic analyses, we confirmed the applicability of the LIVE/DEAD® BacLight™ kit to methanogenic archaea and demonstrated the maintenance of intact cell membranes of methanogens in the presence of PMA. Although strain-specific differences in the efficiency of PMA treatment to methanogenic archaea were observed, we developed an optimal procedure using 130μM PMA and 5min of photo-activation with blue LED light. The results showed that the effectiveness of the PMA treatment strongly depends on the texture of the sediment/soil: silt and clay-rich sediments represent a challenge at all concentrations, whereas successful suppression of DNA from dead cells with compromised membranes was possible for low particle loads of sandy soil (total suspended solids (TSS)≤200mgmL-1). Conclusively, we present two strategies to overcome the problem of insufficient light activation of PMA caused by the turbidity effect (shielding) in particle-rich environmental samples by (i) dilution of the particle-rich sample and (ii) detachment of the cells and the free DNA from the sediment prior to a PMA treatment. Both strategies promise to be usable options for distinguishing living cells and free DNA in complex environmental samples. © 2015 Elsevier B.V.
1889.
Pollen-based paleoenvironmental and paleoclimatic change at Lake Ohrid (south-eastern Europe) during the past 500 ka
Biogeosciences,
13
(5)
1423 – 1437
2016
ISSN: 17264170
Publisher: Copernicus GmbH
Keywords:▾
Albania; Lake Ohrid; Macedonia [Southern Europe]; Coniferophyta; Quercus; Alpine orogeny; biogeochemical cycle; biostratigraphy; climate variation; core analysis; deep drilling; interglacial; marine isotope stage; montane forest; paleobotany; paleoclimate; paleoenvironment; palynology; proxy climate record; refugium; tephra; vegetation dynamics
Abstract: ▾ Lake Ohrid is located at the border between FYROM (Former Yugoslavian Republic of Macedonia) and Albania and formed during the latest phases of Alpine orogenesis. It is the deepest, the largest and the oldest tectonic lake in Europe. To better understand the paleoclimatic and paleoenvironmental evolution of Lake Ohrid, deep drilling was carried out in 2013 within the framework of the Scientific Collaboration on Past Speciation Conditions (SCOPSCO) project that was funded by the International Continental Scientific Drilling Program (ICDP). Preliminary results indicate that lacustrine sedimentation of Lake Ohrid started between 1.2 and 1.9 Ma ago. Here we present new pollen data (selected percentage and concentration taxa/groups) of the uppermost ∼ 200 m of the 569 m long DEEP core drilled in the depocentre of Lake Ohrid. The study is the fruit of a cooperative work carried out in several European palynological laboratories. The age model of this part of the core is based on 10 tephra layers and on tuning of biogeochemical proxy data to orbital parameters. According to the age model, the studied sequence covers the last ∼ 500 000 years at a millennial-scale resolution ( ∼ 1.6 ka) and records the major vegetation and climate changes that occurred during the last 12 (13 only pro parte) marine isotope stages (MIS). Our results indicate that there is a general good correspondence between forested/non-forested periods and glacial-interglacial cycles of the marine isotope stratigraphy. The record shows a progressive change from cooler and wetter to warmer and drier interglacial conditions. This shift in temperature and moisture availability is visible also in vegetation during glacial periods. The period corresponding to MIS11 (pollen assemblage zone OD-10, 428-368 ka BP) is dominated by montane trees such as conifers. Mesophilous elements such as deciduous and semi-deciduous oaks dominate forest periods of MIS5 (PASZ OD-3, 129-70 ka BP) and MIS1 (PASZ OD-1, 14 ka BP to present). Moreover, MIS7 (PASZ OD-6, 245-190 ka) shows a very high interglacial variability, with alternating expansions of montane and mesophilous arboreal taxa. Grasslands (open vegetation formations requiring relatively humid conditions) characterize the earlier glacial phases of MIS12 (PASZ OD-12, 488-459 ka), MIS10 (corresponding to the central part of PASZ OD-10, 428-366 ka) and MIS8 (PASZ OD-7, 288-245 ka). Steppes (open vegetation formations typical of dry environments) prevail during MIS6 (OD-5 and OD-4, 190-129 ka) and during MIS4-2 (PASZ OD-2, 70-14 ka). Our palynological results support the notion that Lake Ohrid has been a refugium area for both temperate and montane trees during glacials. Closer comparisons with other long southern European and Near Eastern pollen records will be achieved through ongoing high-resolution studies. © 2016 Author(s).
1888.
Petrology, geochemistry and fluid inclusion analysis of altered komatiites of the Mendon Formation in the BARB4 drill core, Barberton greenstone belt, South Africa
South African Journal of Geology,
119
(4)
639 – 654
2016
ISSN: 10120750
Publisher: Geological Society of South Africa
Keywords:▾
Barberton Greenstone Belt; banded iron formation; fluid inclusion; greenstone belt; komatiite; metamorphism; petrology; quartz vein; ultramafic rock
Abstract: ▾ The 3.33 to 3.26 Ga Mendon Formation in the Palaeoarchaean Barberton greenstone belt, South Africa, forms the uppermost unit of the Onverwacht Group. It is dominated by ultramafic volcanic rocks interbedded with thin layers of cherty sediments that show pervasive alteration, including widespread serpentinisation, silicification and chert and quartz veining. The BARB4 drill core of the ICDP Barberton drilling project exposes a unique section through the Mendon Formation in the Manzimnyama Syncline. The komatiites are pervasively altered to an assemblage comprising quartz, chlorite, carbonate, talc, biotite, and, locally, plagioclase, K-feldspar, muscovite, amphibole, stilpnomelane and ankerite. The overlying sediments are made up of banded iron formations and rare beds of siliciclastic rocks. Though the altered komatiites are pervasively silicified, SiO, contents do not exceed 58 wt.%, and their major and trace element geochemistry is similar to other komatiitic rocks of the Mendon Formation, particularly those of the M2v-member. Quartz veins and, less commonly, quartz-carbonate and quartz-carbonate-plagioclase veins are found throughout the core. Overall, composition and texture of the veins differ from primary and early diagenetic veins found in silicified komatiites elsewhere in the Barberton greenstone belt. In the BARB4 drill core, the veins are generally coarse-grained, and the immediate wall rocks are locally foliated along the vein margins. In addition, the δ18O values of vein quartz range from 14.1 to 15.3%o, significantly lower than the values typically found in veins on the modern seafloor that formed during low temperature hydrothermal seafloor alteration (∼22 to 32%o). Fluid inclusions in vein quartz are homogeneous two-phase (L+V) aqueous inclusions that occur in trans- and intragranular trails and clusters. Intragranular and isolated fluid inclusions have a similar homogenisation temperature (Th) of 130 to 200°C, with most data ranging between 145 and 175°C. Salinities cluster in three different groups of high (20 to 27wt.% NaCl equiv.), medium (10 to 15wt.% NaCl equiv.) and low salinity (0.3 to 1.5wt.% NaCl equiv.). The composition and microthermometric characteristics of the fluid inclusions analysed within the drill core show similarities to those found in quartz veins in silicified komatiites of the Mendon Formation, which are interpreted to have been entrapped during metamorphism. P-T calculations based on fluid inclusion microthermometry reveal conditions of 230 to 400 MPa and 250 to 400°C. Similar conditions of 240 to 270°C have been obtained using oxygen isotope thermometry, assuming a metamorphic fluid with a δ180 value of 6%o. Collectively, the δ18O values, together with the texture and composition of the veins, are interpreted to indicate a metamorphic origin of the veins. The presence of high salinity inclusions indicates the occurrence of a highly saline fluid that locally mixed with the dominant lower salinity fluids. The high salinity might have been derived from fluid circulation through evaporites. © 2016 December Geological Society of South Africa.
1887.
Petrography and the REE-composition of apatite in the Paleoproterozoic Pilgujärvi sedimentary Formation, Pechenga Greenstone Belt, Russia
Geochimica et Cosmochimica Acta,
186135--153
2016
1886.
Peak-ring structure and kinematics from a multi-disciplinary study of the Schrödinger impact basin
Nature Communications,
7
2016
Abstract: ▾ The Schrödinger basin on the lunar farside is â ;1/4320 km in diameter and the best-preserved peak-ring basin of its size in the Earth-Moon system. Here we present spectral and photogeologic analyses of data from the Moon Mineralogy Mapper instrument on the Chandrayaan-1 spacecraft and the Lunar Reconnaissance Orbiter Camera (LROC) on the LRO spacecraft, which indicates the peak ring is composed of anorthositic, noritic and troctolitic lithologies that were juxtaposed by several cross-cutting faults during peak-ring formation. Hydrocode simulations indicate the lithologies were uplifted from depths up to 30 km, representing the crust of the lunar farside. Through combining geological and remote-sensing observations with numerical modelling, we show that a Displaced Structural Uplift model is best for peak rings, including that in the K-T Chicxulub impact crater on Earth. These results may help guide sample selection in lunar sample return missions that are being studied for the multi-Agency International Space Exploration Coordination Group. © The Author(s) 2016.
1885.
Northern Mediterranean climate since the Middle Pleistocene: A 637 ka stable isotope record from Lake Ohrid (Albania/Macedonia)
Biogeosciences,
13
(6)
1801-1820
2016
ISSN: 17264170
Publisher: Copernicus GmbH
Keywords:▾
calcite; carbon isotope; climate variation; core analysis; glacial-interglacial cycle; long-term change; marine isotope stage; Mediterranean environment; oxygen isotope; paleoenvironment; reconstruction; siderite; stable isotope, Lake Mikri Prespa; Lake Ohrid
Abstract: ▾ Lake Ohrid (Macedonia/Albania) is an ancient lake with unique biodiversity and a site of global significance for investigating the influence of climate, geological, and tectonic events on the generation of endemic populations. Here, we present oxygen (δ18O) and carbon (δ13C) isotope data from carbonate over the upper 243 m of a composite core profile recovered as part of the Scientific Collaboration on Past Speciation Conditions in Lake Ohrid (SCOPSCO) project. The investigated sediment succession covers the past ca. 637 ka. Previous studies on short cores from the lake (up to 15 m, < 140 ka) have indicated the total inorganic carbon (TIC) content of sediments to be highly sensitive to climate change over the last glacial-interglacial cycle. Sediments corresponding to warmer periods contain abundant endogenic calcite; however, an overall low TIC content in glacial sediments is punctuated by discrete bands of early diagenetic authigenic siderite. Isotope measurements on endogenic calcite (δ18Oc and δ13Cc) reveal variations both between and within interglacials that suggest the lake has been subject to palaeoenvironmental change on orbital and millennial timescales. We also measured isotope ratios from authigenic siderite (δ18Os and δ13Cs) and, with the oxygen isotope composition of calcite and siderite, reconstruct δ18O of lake water (δ18Olw) over the last 637 ka. Interglacials have higher δ18Olw values when compared to glacial periods most likely due to changes in evaporation, summer temperature, the proportion of winter precipitation (snowfall), and inflow from adjacent Lake Prespa. The isotope stratigraphy suggests Lake Ohrid experienced a period of general stability from marine isotope stage (MIS) 15 to MIS 13, highlighting MIS 14 as a particularly warm glacial. Climate conditions became progressively wetter during MIS 11 and MIS 9. Interglacial periods after MIS 9 are characterised by increasingly evaporated and drier conditions through MIS 7, MIS 5, and the Holocene. Our results provide new evidence for long-term climate change in the northern Mediterranean region, which will form the basis to better understand the influence of major environmental events on biological evolution within Lake Ohrid. © Author(s) 2016.
1884.
Nondestructive spectroscopic and petrochemical investigations of Paleoarchean spherule layers from the ICDP drill core BARB5, Barberton Mountain Land, South Africa
Meteoritics and Planetary Science,
51
(12)
2441-2458
2016
Abstract: ▾ A Paleoarchean impact spherule-bearing interval of the 763 m long International Continental Scientific Drilling Program (ICDP) drill core BARB5 from the lower Mapepe Formation of the Fig Tree Group, Barberton Mountain Land (South Africa) was investigated using nondestructive analytical techniques. The results of visual observation, infrared (IR) spectroscopic imaging, and micro-X-ray fluorescence (μXRF) of drill cores are presented. Petrographic and sedimentary features, as well as major and trace element compositions of lithologies from the micrometer to kilometer-scale, assisted in the localization and characterization of eight spherule-bearing intervals between 512.6 and 510.5 m depth. The spherule layers occur in a strongly deformed section between 517 and 503 m, and the rocks in the core above and below are clearly less disturbed. The μXRF element maps show that spherule layers have similar petrographic and geochemical characteristics but differences in (1) sorting of two types of spherules and (2) occurrence of primary minerals (Ni-Cr spinel and zircon). We favor a single impact scenario followed by postimpact reworking, and subsequent alteration. The spherule layers are Al2O3-rich and can be distinguished from the Al2O3-poor marine sediments by distinct Al-OH absorption features in the short wave infrared (SWIR) region of the electromagnetic spectrum. Infrared images can cover tens to hundreds of square meters of lithologies and, thus, may be used to search for Al-OH-rich spherule layers in Al2O3-poor sediments, such as Eoarchean metasediments, where the textural characteristics of the spherule layers are obscured by metamorphism. © The Meteoritical Society, 2016.
1883.
Nondestructive spectroscopic and petrochemical investigations of Paleoarchean spherule layers from the ICDP drill core BARB5, Barberton Mountain Land, South Africa
Meteoritics and Planetary Science,
51
(12)
2441 – 2458
2016
ISSN: 10869379
Publisher: University of Arkansas
Abstract: ▾ A Paleoarchean impact spherule-bearing interval of the 763 m long International Continental Scientific Drilling Program (ICDP) drill core BARB5 from the lower Mapepe Formation of the Fig Tree Group, Barberton Mountain Land (South Africa) was investigated using nondestructive analytical techniques. The results of visual observation, infrared (IR) spectroscopic imaging, and micro-X-ray fluorescence (μXRF) of drill cores are presented. Petrographic and sedimentary features, as well as major and trace element compositions of lithologies from the micrometer to kilometer-scale, assisted in the localization and characterization of eight spherule-bearing intervals between 512.6 and 510.5 m depth. The spherule layers occur in a strongly deformed section between 517 and 503 m, and the rocks in the core above and below are clearly less disturbed. The μXRF element maps show that spherule layers have similar petrographic and geochemical characteristics but differences in (1) sorting of two types of spherules and (2) occurrence of primary minerals (Ni-Cr spinel and zircon). We favor a single impact scenario followed by postimpact reworking, and subsequent alteration. The spherule layers are Al2O3-rich and can be distinguished from the Al2O3-poor marine sediments by distinct Al-OH absorption features in the short wave infrared (SWIR) region of the electromagnetic spectrum. Infrared images can cover tens to hundreds of square meters of lithologies and, thus, may be used to search for Al-OH-rich spherule layers in Al2O3-poor sediments, such as Eoarchean metasediments, where the textural characteristics of the spherule layers are obscured by metamorphism. © The Meteoritical Society, 2016.
1882.
Noble gas composition and 40Ar/39Ar age in eclogites from the main hole of the Chinese Continental Scientific Drilling project
Contributions to Mineralogy and Petrology,
171
(10)
2016
ISSN: 00107999
Publisher: Springer Verlag
Keywords:▾
argon-argon dating; chemical composition; Chinese Continental Scientific Drilling Project; concentration (composition); eclogite; fluid composition; meteoric water; noble gas; ultrahigh pressure metamorphism
Abstract: ▾ We present the first comprehensive noble gas study on eclogites. The four eclogite samples were recovered during the Chinese Continental Scientific Drilling and are from two distinct profile depth sections differing in their degree of interaction with meteoric water, based on their δ18O-values (surface related and of mantle-type). Hence, noble gas analyses offer the potential to further discriminate between shallow (meteoric) and deep (mantle) fluid sources. Noble gas compositions reveal typical crustal fluid compositions, characterized by a variable mixture of atmospheric gases with significant contributions of nucleogenic neon, radiogenic 4He*, radiogenic 40Ar*, fissiogenic 131–136Xe, and presumably bariogenic 131Xe, but no significant addition of mantle gases. This signature can be also considered to represent one endmember component of eclogitic diamonds. Concentrations of non-radiogenic noble gases are rather low, with depletion of light relative to the heavier noble gases. Eclogites from lower depth which experienced a higher degree of interaction with meteoric water also showed higher contributions of atmospheric gas compared with eclogites recovered from greater depth. This is interpreted to result from interaction with high-salinity fluids during ultrahigh pressure (UHP). It demonstrates that the atmospheric noble gas abundance is a proxy for interaction with surface related fluids. 40Ar/39Ar (inverse) isochron ages of two phengite separates (241.2 ± 0.4 Ma and 275.0 ± 1.8 Ma, 1σ-errors) predate the main phase of UHP metamorphism (ca. 220 Ma). Biotite yields an integrated age of about 1100 Ma. These age values are interpreted to reflect the likely addition of excess 40Ar without any chronological meaning. © 2016, Springer-Verlag Berlin Heidelberg.
1881.
Miocene relative sea level on the New Jersey shallow continental shelf and coastal plain derived from one-dimensional backstripping: A case for both eustasy and epeirogeny
Geosphere,
12
(5)
1437-1456
2016
ISSN: 1553040X
Publisher: Geological Society of America
Keywords:▾
Offshore drilling; Submarine geology; Subsidence; Tectonics, Continental shelves; Integrated ocean drilling programs; Middle Miocene; Ocean drilling programs; Offshore sea level; Onshore drilling; Relative sea level; Sealevel change, Sea level, coastal plain; continental shelf; eustacy; Miocene; Ocean Drilling Program; paleoceanography, New Jersey; United States
Abstract: ▾ Onshore drilling by Ocean Drilling Program (ODP) Legs 150X and 174AX and offshore drilling by Integrated Ocean Drilling Program (IODP) Expedition 313 provides continuous cores and logs of seismically imaged Lower to Middle Miocene sequences. We input ages and paleodepths of these sequences into one-dimensional backstripping equations, progressively accounting for the effects of compaction, Airy loading, and thermal subsidence. The resulting difference between observed subsidence and theoretical thermal subsidence provide relative sea-level curves that reflect both global average sea level and non-thermal subsidence. In contrast with expectations, backstripping suggests that the relative sea-level maxima in proximal onshore sites were lower than correlative maxima on the shelf. This requires that the onshore New Jersey coastal plain has subsided relative to the shelf, which is consistent with models of relative epeirogeny due to subduction of the Farallon plate. These models predict subsidence of the coastal plain relative to the shelf. Although onshore and offshore sea-level estimates are offset by epeirogeny, the amplitude of million-year-scale Early to Middle Miocene sea-level changes seen at the New Jersey margin is generally 5-20 m and occasionally as great as 50 m. These events are interpreted to represent eustatic variations, because they occur on a shorter time frame than epeirogenic influences. Correction for epeirogenic effects largely reconciles differences between onshore and offshore relative sea-level estimates and suggests that backstripping provides a testable eustatic model for the Early to Middle Miocene.
1880.
Millennial-scale vegetation changes in the north-eastern Russian Arctic during the Pliocene/Pleistocene transition (2.7–2.5 Ma) inferred from the pollen record of Lake El'gygytgyn
Quaternary Science Reviews,
147245-258
2016
ISSN: 02773791
Publisher: Elsevier Ltd
Keywords:▾
Algae; Climate change; Ecosystems; Forestry; Vegetation, Early pleistocene; Marine isotope stages; North-easter Russian Arctic; Pliocene; Pollen assemblage; Pollen record; Shallow water environment; Vegetation change, Lakes, climate variation; coniferous tree; fossil record; herb; lacustrine deposit; lake level; marine isotope stage; paleobotany; paleoenvironment; palynology; Pliocene-Pleistocene boundary; shrub; vegetation dynamics, Arctic; Russian Federation, Alnus; Artemisia; Betula nana; Botryococcus; Chlorophyta; Larix; Picea; Zygnema
Abstract: ▾ The sediment record of Lake El'gygytgyn (67°30′N, 172°05′E) spans the past 3.6 Ma and provides unique opportunities for qualitative and quantitative reconstructions of the regional paleoenvironmental history of the terrestrial Arctic. Millennial-scale pollen studies of the sediments that accumulated during the Late Pliocene and Early Pleistocene (ca. 2.7 to 2.5 Ma) demonstrate orbitally-driven vegetation and climate changes during this transitional interval. Pollen spectra show a significant vegetation shift at the Pliocene/Pleistocene boundary that is, however, delayed by a few thousand years compared to lacustrine response. About 2.70–2.68 Ma the vegetation at Lake El'gygytgyn, currently a tundra area was mostly dominated by larch forests with some shrub pine, shrub alder and dwarf birch in understory. During the marine isotope stages G3 and G1, ca. 2.665–2.647 and 2.625–2.617 Ma, some spruce trees grew in the local larch-pine forests, pointing to relatively warm climate conditions. At the beginning of the Pleistocene, around 2.588 Ma, a prominent climatic deterioration led to a change from larch-dominated forests to predominantly treeless steppe- and tundra-like habitats. Between ca. 2.56–2.53 Ma some climate amelioration is reflected by the higher presence of coniferous taxa (mostly pine and larch, but probably also spruce) in the area. After 2.53 Ma a relatively cold and dry climate became dominant again, leading to open steppe-like and shrubby environments followed by climate amelioration between ca. 2.510 and 2.495 Ma, when pollen assemblages show that larch forests with dwarf birch and shrub alder still grew in the lake's vicinity. Increased contents of green algae colonies (Botryococcus) remains and Zygnema cysts around 2.691–2.689, 2.679–2.677, 2.601–2.594, 2.564–2.545, and 2.532–2.510 Ma suggest a spread of shallow-water environments most likely due to a lake-level lowering. These events occurred simultaneously with dry climate conditions inferred from broad distribution of steppe habitats with Artemisia and other herbs. © 2016 Elsevier Ltd
1879.
Shallow crustal discontinuities inferred from waveforms of microearthquakes: Method and application to KTB Drill Site and West Bohemia Swarm Area
Journal of Geophysical Research: Solid Earth,
121
(2)
881 – 902
2016
ISSN: 21699313
Publisher: Blackwell Publishing Ltd
Keywords:▾
Bohemian Massif; crustal structure; discontinuity; earthquake swarm; focal mechanism; microearthquake; seismic wave; waveform analysis
Abstract: ▾ The waveforms of microearthquakes are of high frequency and complicated. They contain many phases secondarily generated at crustal interfaces and at small-scale inhomogeneities. They are highly sensitive to focal mechanisms and thus very different for each station of local networks. However, with a large number of microearthquakes, the scattered waves present in the waveforms can serve for identifying the prominent crustal discontinuities and for determining their depth. In this paper, we develop a new approach for extracting information on crustal structure from such waveforms and apply it for determining depth and lateral variations of crustal discontinuities. We show that strong dependence of microseismic waveforms on radiation pattern requires good station coverage and knowledge of focal mechanisms of the microearthquakes. Analysis of real observations is supported by waveform modeling and by analysis of radiation patterns of scattered waves. The robustness of the inversion for depth of crustal interfaces is achieved by stacking of a large number of waveforms and by applying a grid search algorithm. The method is demonstrated on two microseismic data sets of different origin: microseismicity induced during the Continental Super-Deep Drilling Project (KTB) 2000 fluid injection experiment and natural seismicity in the West Bohemia swarm region. High-frequency conversions at the KTB site indicate a prominent interface at depths of 2.3-4.1 km consistent with previous interpretations. Geologically, it may represent the contact of granitoids with much faster metabasites underneath. Seismicity in West Bohemia indicates a strong-contrast interface at depths of 3.5-6.0 km. This interface is in agreement with previous profiling and might be related to trapping of fluid emanations ascending from the mantle. ©2016. American Geophysical Union. All Rights Reserved.
1878.
Millennial to orbital-scale variations of drought intensity in the Eastern Mediterranean
Quaternary Science Reviews,
13377-95
2016
ISSN: 02773791
Publisher: Elsevier Ltd
Keywords:▾
Glacial geology; Lakes; Sea ice, Atlantic meridional overturning circulations; Atmospheric reorganization; Dansgaard-Oeschger variability; Eastern Mediterranean; ICDP PALEOVAN; Insolation seasonality; Lake vans; Milankovitch cycle, Drought, climate change; climate modeling; Dansgaard-Oeschger cycle; drought; ice sheet; iceberg calving; Last Glacial-Interglacial; Mediterranean environment; Northern Hemisphere; paleoclimate; precipitation (climatology); seasonality; sediment analysis, Atlantic Ocean; Atlantic Ocean (North); Lake Van; Turkey
Abstract: ▾ Millennial to orbital-scale rainfall changes in the Mediterranean region and corresponding variations in vegetation patterns were the result of large-scale atmospheric reorganizations. In spite of recent efforts to reconstruct this variability using a range of proxy archives, the underlying physical mechanisms have remained elusive. Through the analysis of a new high-resolution sedimentary section from Lake Van (Turkey) along with climate modeling experiments, we identify massive droughts in the Eastern Mediterranean for the past four glacial cycles, which have a pervasive link with known intervals of enhanced North Atlantic glacial iceberg calving, weaker Atlantic Meridional Overturning Circulation and Dansgaard-Oeschger cold conditions. On orbital timescales, the topographic effect of large Northern Hemisphere ice sheets and periods with minimum insolation seasonality further exacerbated drought intensities by suppressing both summer and winter precipitation. © 2015 Elsevier Ltd.
1877.
Seismicity distribution in conjunction with spatiotemporal variations of coseismic slip and postseismic creep along the combined 1999 Izmit-Düzce rupture
Tectonophysics,
686132-145
2016
ISSN: 00401951
Publisher: Elsevier B.V.
Keywords:▾
Creep; Strike-slip faults, Earthquake dynamics; NW Turkey; Postseismic creeps; Seismic cycle; Seismicity; Seismicity and tectonics; Seismotectonics; Spatial analysis, Earthquakes, coseismic process; creep; earthquake rupture; Kocaeli earthquake 1999; postseismic process; seismicity; seismotectonics; slip rate; spatial analysis; spatial distribution; spatial variation; temporal distribution; temporal variation, Duzce [Turkey]; Izmit; Kocaeli [Turkey]; Turkey
Abstract: ▾ The North Anatolian Fault Zone (NAFZ) in NW Turkey as one of the most active and best studied strike-slip faults provides a unique opportunity to study earthquake related relaxation processes through analyzing co- and postseismic deformation. We study the spatial and temporal distributions of seismicity related to the two consecutive 1999 M > 7 Izmit and Düzce earthquakes. A high-resolution aftershock catalogue including ~ 10,000 hypocenters extending along the combined rupture zone and extending from prior to the Izmit event to after the Düzce event is studied. Spatial and temporal distributions of events allow to identify distinct seismically active and inactive fault patches. Their location is related to the co- and postseismic deformation within and below the seismogenic layer, respectively. Four seismically inactive patches extending 30–50 km along the rupture zone and down to 10 km depth are identified with a systematic spatial shift between them introduced by the Düzce mainshock. The cumulative distribution of sub-areas hosting coseismic slip, aftershock clusters and postseismic creep shows that the entire upper (seismogenic) and lower (ductile) portions of the crust along the combined Izmit and Düzce rupture zone are activated between rupture initiation and a two-year postseismic period. This observation was only achieved due to the subsequent occurrence of two adjacent M > 7 strike-slip earthquakes in combination with a distinct local seismic and geodetic monitoring. Our findings suggest that a coseismically introduced lateral and vertical slip deficit is systematically compensated postseismically in both the brittle and ductile portions of the crust. © 2016 Elsevier B.V.
1876.
The water retention curve and relative permeability for gas production from hydrate-bearing sediments: pore-network model simulation
Geochemistry, Geophysics, Geosystems,
17
(8)
3099-3110
2016
ISSN: 15252027
Publisher: Blackwell Publishing Ltd
Keywords:▾
Computerized tomography; Curve fitting; Dissociation; Flow of water; Gas permeability; Gases; Hydration; Hydraulics; Morphology; Sediments, Brooks-Corey model; Hydrate bearing sediments; Pore-network modeling; Relative permeability; Van Genuchten model; Water retention curve, Gas hydrates, gas hydrate; gas production; hydrocarbon reservoir; numerical model; permeability; porosity; water retention
Abstract: ▾ The water retention curve and relative permeability are critical to predict gas and water production from hydrate-bearing sediments. However, values for key parameters that characterize gas and water flows during hydrate dissociation have not been identified due to experimental challenges. This study utilizes the combined techniques of micro-focus X-ray computed tomography (CT) and pore-network model simulation to identify proper values for those key parameters, such as gas entry pressure, residual water saturation, and curve fitting values. Hydrates with various saturation and morphology are realized in the pore-network that was extracted from micron-resolution CT images of sediments recovered from the hydrate deposit at the Mallik site, and then the processes of gas invasion, hydrate dissociation, gas expansion, and gas and water permeability are simulated. Results show that greater hydrate saturation in sediments lead to higher gas entry pressure, higher residual water saturation, and steeper water retention curve. An increase in hydrate saturation decreases gas permeability but has marginal effects on water permeability in sediments with uniformly distributed hydrate. Hydrate morphology has more significant impacts than hydrate saturation on relative permeability. Sediments with heterogeneously distributed hydrate tend to result in lower residual water saturation and higher gas and water permeability. In this sense, the Brooks-Corey model that uses two fitting parameters individually for gas and water permeability properly capture the effect of hydrate saturation and morphology on gas and water flows in hydrate-bearing sediments. © 2016. American Geophysical Union. All Rights Reserved.
1875.
Short Note. the smectite to corrensite transition: X-ray diffraction results from the MH-2B core, western Snake River Plain, Idaho, USA
Clay Minerals,
51
(4)
691-696
2016
ISSN: 00098558
Publisher: Mineralogical Society
Keywords:▾
X ray diffraction analysis, Air Force Base; Artesian pressure; Corrensite; Hyaloclastites; Lake sediments; Project hotspot; Smectites; Snake river plains, Basalt, artesian well; basalt; borehole breakout; Cenozoic; corrensite; hyaloclastite; hydrothermal alteration; lacustrine deposit; smectite, Idaho; Snake River Plain; United States
Abstract: ▾ The MH-2B borehole, a part of Project HOTSPOT, was drilled to a depth of 1821 m in late Cenozoic basalts, hyaloclastites and interbedded lake sediments, on the Mountain Home Air Force Base in southern Idaho, USA. Drillers encountered hot water (145°C) under artesian pressure at 1745 m in a narrow zone of highly fractured rock associated with a major sub-surface fault. X-ray diffraction (XRD) analysis identified corrensite (with and without smectite) between 1700 and 1800 m, but only smectite above 1700 m and below 1800 m. This corrensite horizon contains a relatively narrow zone of fracturing and hot artesian water near its centre but for the most part occurs in relatively massive basalt flows. No evidence was found for randomly interstratified chlorite-smectite. © 2016 by Walter de Gruyter Berlin/Boston.
1874.
Three novel species of bacillariophyta (Diatoms) belonging to aulacoseira and lindavia from the pliocene hadar formation, afar depression of Ethiopia
Phytotaxa,
272
(4)
235 – 247
2016
ISSN: 11793155
Publisher: Magnolia Press
Abstract: ▾ Paleolake Hadar was an expansive lake in the lower Awash Valley of Ethiopia’s Afar Depression that existed periodically through the Late Pliocene. The sedimentary deposits from this ancient lake (Hadar Formation) have broad importance because a significant number of hominin fossils have been recovered from the formation. Samples of the Hadar Formation lacustrine sequence were collected from sediment cores extracted as part of the Hominin Sites and Paleolakes Drilling Project (HSPDP). A paleoecological study of the HSPDP Northern Awash (Hadar Formation) material has unearthed three novel species of Bacillariophyta (diatoms) from diatomites that appear periodically in the cores. The Hadar Formation assemblage represents a newly revealed excerpt from the evolutionary history of freshwater diatoms in East Africa during the Piacenᴢian age (2.59-3.60 Ma). The HSPDP Northern Awash diatom species are compared to previously reported diatoms from Pliocene outcrops, modern and fossil core material from Lake Malawi, and extant species. Here we describe two new species of Aulacoseira and one of Lindavia. Taxonomic treatment of two diatom varieties reported by previous researchers as Melosira are transferred into Aulacoseira herein. © 2016 Magnolia Press.
1873.
Microstructures and their implications for faulting processes -Insights from DGLab core samples from the Gulf of Corinth
Journal of Structural Geology,
8662 – 74
2016
ISSN: 01918141
Publisher: Elsevier Ltd
Keywords:▾
Gulf of Corinth; Ionian Sea; Mediterranean Sea; Calcite; Cements; Electron microscopy; High resolution transmission electron microscopy; Mass transfer; Microstructure; Porosity; Rocks; Scanning electron microscopy; Stainless steel; Transmission electron microscopy; X ray diffraction; Clay fabrics; Dissolution precipitations; EBSD; Fault rock; Fluid-rock interaction; Gulf of Corinth; Microstructure analysis; core analysis; deformation mechanism; dissolution; fault slip; fault zone; faulting; microstructure; precipitation (chemistry); stress field; water-rock interaction; Structural geology
Abstract: ▾ We have examined microstructures, mineralogical composition, geochemical alteration, and texture of four selected fault rock samples from the Deep Geodynamical Laboratory (DGLab) Gulf of Corinth project using optical microscopy, cathodoluminescence microscopy (CL), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and synchrotron X-ray diffraction measurements. The fault core is composed of red and gray clayey gouge material and surrounded by a damage zone of brecciated limestones. Pressure solution features, calcite veins and calcite clasts in the breccia and gouge material attest the presence of paleo-fluids and fluid-driven mass transfer during deformation. Differences in CL-colors between the matrix and calcite vein cement and inside the vein cement suggest repeated infiltration of fluids with different composition from various sources (formation water and meteoric water). Twin lamellae densities estimated in calcite veins are used as paleo-piezometer. The deduced differential stress is ~140 ± 70 MPa for the older vein generation and appears to be higher than stress for the youngest veins (45 ± 23 MPa). In spite of the relatively small clay content in both samples, newly formed clay minerals have been observed in gray as well as red clayey gouge material. Differences between gray and red clay gouge material are found in fault rock composition, porosity and clay fabric. The proportion of chlorite in the red gouge is significantly less than that in the gray gouge whereas the initial porosity is significantly higher than in the gray gouge material. The detection of a well-oriented clay fabric in red clay gouge samples is unique in comparison to other major fault zones. © 2016 Elsevier Ltd.
1872.
Methods for sampling and analysis of attached and planktonic microorganisms in deep granitic rock aquifers
SKB report R-16-09 p 61
2016
1871.
Deep Borehole Field Test Research Activities at LBNL. Fuel Cycle Technology.
Lawrence Berkeley National Laboratory (LBNL),
Berkeley, CA (United States)
2016
1870.
Fe-Ti-V-(P) resources in the upper zone of the Bushveld complex, South Africa
,
Papers and Proceedings of the Royal Society of Tasmania
Volume150
,
Page 15--22
2016