Operational overview of the first offshore production test of methane hydrates in the Eastern Nankai Trough - Yamamoto, K.; Terao, Y.; Fujii, T.; Ikawa, T.; Seki, M.; Matsuzawa, M.; Kanno, T. (Proceedings of the Annual Offshore Technology Conference, 2014)
In March 2013, the world's first field trial of gas production from marine methane hydrate deposits was conducted in the Daini Atsumi Knoll area of the Eastern Nankai Trough off the Pacific coast of Japan as a process to bring gas hydrates under seafloor to valuable energy resource. The technique used to dissociate the ice-like material was depressurization method that had been applied in the previous production test in Mallik site, the Northwest Territories, Canada in 2007-2008. Japan Oil, Gas and Metals National Corporation (JOGMEC) as a part of MH21, the Research Consortium for Methane Hydrate Resources in Japan planed and supervised the project with the funding of the Ministry of Economy, Trade and Industry (METI), and scientific supports from the National Institute of Advance Industrial Science and Technology (AIST). One production well with two monitoring boreholes were drilled in the test site for the test. Along with the flow test operation, intensive data acquisition program was planned and implemented to understand behavior of methane hydrate dissociation-bearing sediments against depressurization. To realize high degree of drawdown in relatively shallow formation below deepwater, several downhole devices were designed and installed. The flow test started in the morning of March 12 and lasted until severe sand production forced to terminate the operation six days later. During the stable production term, gas flow rate was approximately 20,000m3 under atmospheric condition, and gas liquid ratio was larger than 100. A lot of data including formation temperatures, fluid pressure and temperature, and physical property changes in the formation were obtained. The data taken are under studies to verify applicability of the depressurization technique as a methane hydrate production technologies. Copyright 2014, Offshore Technology Conference.
cited By 240
Keywords: Atmospheric movements; Data acquisition; Energy resources; Flow of gases; Gases; Hydration; Industrial research; Methane; Offshore oil well production; Offshore oil wells; Offshore technology; Software testing; Acquisition programs; Atmospheric conditions; Depressurization methods; Formation temperature; Methane hydrate dissociation; Methane hydrate productions; Ministry of economy; trade and industries; Science and Technology; Gas hydrates

New proposed drilling at Surtsey Volcano, Iceland: SUSTAIN workshop; Heimaey Island, Iceland, 30 September to 4 October 2014 - Jackson, M.D. (Eos (United States), 2014)
Surtsey, an isolated oceanic island and a World Heritage Site of the United Nations Educational, Scientific and Cultural Organization, is a uniquely well-documented natural laboratory for investigating processes of rift zone volcanism, hydrothermal alteration of basaltic tephra, and biological colonization and succession in surface and subsurface pyroclastic deposits. Deposits from Surtsey's eruptions from 1963 to 1967 were first explored via a 181-meter hole drilled in 1979 by the U.S. Geological Survey and Icelandic Museum of Natural History. © 2014. American Geophysical Union. All Rights Reserved.
cited By 2
Keywords: colonization; conference proceeding; drilling; hydrothermal alteration; microbial activity; mineral; pyroclastic deposit; rift zone; tephra; volcanic eruption; volcanism; World Heritage Site; Iceland; Surtsey

Noble gas residence times of saline waters within crystalline bedrock, Outokumpu Deep Drill Hole, Finland - Kiet{av{ainen, Riikka; Ahonen, Lasse; Kukkonen, Ilmo T.; Niedermann, Samuel; Wiersberg, Thomas (Geochimica et Cosmochimica Acta, 2014)
Noble gas residence times of saline groundwaters from the 2516m deep Outokumpu Deep Drill Hole, located within the Precambrian crystalline bedrock of the Fennoscandian Shield in Finland, are presented. The accumulation of radiogenic (4He, 40Ar) and nucleogenic (21Ne) noble gas isotopes in situ together with the effects of diffusion are considered. Fluid samples were collected from depths between 180 and 2480m below surface, allowing us to compare the modelled values with the measured concentrations along a vertical depth profile. The results show that while the concentrations in the upper part are likely affected by diffusion, there is no indication of diffusive loss at or below 500m depth. Furthermore, no mantle derived gases were found unequivocally. Previous studies have shown that distinct vertical variation occurs both in geochemistry and microbial community structuring along the drill hole, indicating stagnant waters with no significant exchange of fluids between different fracture systems or with surface waters. Therefore in situ accumulation is the most plausible model for the determination of noble gas residence times. The results show that the saline groundwaters in Outokumpu are remarkably old, with most of the samples indicating residence times between 20 and 50Ma. Although being first order approximations, the ages of the fluids clearly indicate that their formation must predate more recent events, such as Quaternary glaciations. Isolation within the crust since the Eocene-Miocene epochs has also direct implications to the deep biosphere found at Outokumpu. These ecosystems must have been isolated for a long time and thus very likely rely on energy and carbon sources such as H2 and CO2 from groundwater and adjacent bedrock rather than from the ground surface. © 2014 Elsevier Ltd.
Keywords: Baltic Shield; East European Craton; Finland; Outokumpu; Pohjois-Karjala; bedrock; carbon dioxide; diffusion; groundwater; hydrochemistry; hydrogen; isotopic composition; noble gas; residence time

Noble gases in the sediments of Lake Van - solute transport and palaeoenvironmental reconstruction - Tomonaga, Y.; Brennwald, M.S.; Meydan, A.F.; Kipfer, R. (Quaternary Science Reviews, 2014)
Sediment samples acquired in 2010 from the long cores of the International Continental Scientific Drilling Program (ICDP) PaleoVan drilling project on Lake Van for noble-gas analysis in the pore water allow determination of the local terrestrial He-gradient as a function of depth within a sediment column of more than 200m. These measurements yield first insights into the physical transport mechanisms of terrigenic He through the uppermost part of unconsolidated lacustrine sediments overlying the continental crust.In line with our previous work on the spatial distribution of the terrigenic He release into Lake Van, we identify a high He concentration gradient in the uppermost 10m of the sediment column. The He concentration gradient decreases below this depth down to approx. 160. m following in general the expectations of the modelling of radiogenic He production and transport in a sediment column with homogeneous fluid transport properties. Overall the in-situ radiogenic He production due to the decay of U and Th in the mineral phases of the sediments accounts for about 80% of the He accumulation. At approx. 190. m we observe a very high He concentration immediately below a large lithological unit characterised by strong deformations. We speculate that this local enrichment is the result of the lower effective diffusivities in the pore space that relate to the abrupt depositional history of this deformed unit. This particular lithological unit seems to act as a barrier that limits the transport of solutes in the pore space and hence might trap information on the past geochemical conditions in the pore water of Lake Van.The dissolved concentrations of atmospheric noble gases in the pore waters of the ICDP PaleoVan cores are used to geochemically reconstruct salinity on the time scale of 0-55kaBP. Higher salinities in the pore water at a depth of about 20m suggest a significantly lower lake level of Lake Van in the past. © 2014 Elsevier Ltd.
cited By 19
Keywords: Inert gases; Infill drilling; Lakes; Lithology; Mineral industry; Solute transport; Water; Concentration gradients; Continental scientific drillings; Deep drilling; Dissolved concentrations; ICDP; Palaeo-salinity; Palaeoenvironmental reconstruction; PaleoVan; Sediments; continental crust; deep drilling; helium; lacustrine deposit; lithology; mineral; noble gas; paleoenvironment; paleosalinity; porewater; reconstruction; sediment analysis; sediment chemistry; solute transport; Lake Van; Turkey

Observations of the genus Cyclotella (K{utzing) Br'ebisson in ancient lakes Ohrid and Prespa and a description of two new species c. paraocellata sp. nov. and C. prespanensis sp. nov - Cvetkoska, Aleksandra; Hamilton, Paul B.; Ognjanova-Rumenova, Nadja; Levkov, Zlatko (Nova Hedwigia, 2014)
Several taxa from the genus Cyclotella observed in two ancient sister lakes, Prespa and Ohrid were studied and compared to the regionally common species Cyclotella ocellata. Two new species are described from Lake Prespa and additionally Cyclotella thienemannii var. minuscula from Lake Ohrid is formally transferred to Cyclotella minuscula (Jurilj) Cvetkoska stat. nov. Cyclotella paraocellata sp. nov. is compared to C. ocellata and is characterized by a large morphological variability in the fossil and recent diatom assemblages. Cyclotella prespanensis sp. nov. is described and distinguished as a separate taxon by its valve size range, colliculate central area, stria density and number and position of marginal fultoportulae and rimoportulae. The investigation reveals C. ocellata and C. minuscula as the only taxa of the genus Cyclotella present in fossil and contemporary diatom assemblages from both Lake Ohrid and Lake Prespa. © 2014 J. Cramer in Gebr. Borntraeger Verlagsbuchhandlung, Stuttgart. Germany.

Pliocene to Pleistocene climate and environmental history of Lake El'gygytgyn, Far East Russian Arctic, based on high-resolution inorganic geochemistry data - Wennrich, V.; Minyuk, P. S.; Borkhodoev, V.; Francke, A.; Ritter, B.; Nowaczyk, N. R.; Sauerbrey, M. A.; Brigham-Grette, J.; Melles, M. (Climate of the Past, 2014)
The 3.6 Ma sediment record of Lake El'gygytgyn/NE Russia, Far East Russian Arctic, represents the longest continuous climate archive of the terrestrial Arctic. Its elemental composition as determined by X-ray fluorescence scanning exhibits significant changes since the mid-Pliocene caused by climate-driven variations in primary production, postdepositional diagenetic processes, and lake circulation as well as weathering processes in its catchment. During the mid-to late Pliocene, warmer and wetter climatic conditions are reflected by elevated Si/Ti ratios, indicating enhanced diatom production in the lake. Prior to 3.3 Ma, this signal is overprinted by intensified detrital input from the catchment, visible in maxima of clastic-related proxies, such as K. In addition, calcite formation in the early lake history points to enhanced Ca flux into the lake caused by intensified weathering in the catchment. A lack of calcite deposition after ca. 3.3 Ma is linked to the development of permafrost in the region triggered by cooling in the mid-Pliocene. After ca. 3.0 Ma the elemental data suggest a gradual transition to Pleistocene-style glacial-interglacial cyclicity. In the early Pleistocene, the cyclicity was first dominated by variations on the 41 kyr obliquity band but experienced a change to a 100 kyr eccentricity dominance during the middle Pleistocene transition (MPT) at ca. 1.2-0.6 Ma. This clearly demonstrates the sensitivity of the Lake El'gygytgyn record to orbital forcing. A successive decrease of the baseline levels of the redox-sensitive Mn/Fe ratio and magnetic susceptibility between 2.3 and 1.8 Ma reflects an overall change in the bottom-water oxygenation due to an intensified occurrence of pervasive glacial episodes in the early Pleistocene. The coincidence with major changes in the North Pacific and Bering Sea paleoceanography at ca. 1.8 Ma implies that the change in lake hydrology was caused by a regional cooling in the North Pacific and the western Beringian landmass and/or changes in the continentality. Further increases in total organic carbon and total nitrogen content after ca. 1.6 Ma are attributed to reduced organic matter decay in the sediment during prolonged anoxic periods. This points to more extensive periods of perennial ice coverage, and thus, to a progressive shifts towards more intense peak glacial periods. In the course of the Pleistocene glacial-interglacial sequence eight so-called super-interglacials occur. Their exceptionally warm conditions are reflected by extreme Si/Ti peaks accompanied by lows in Ti, K, and Fe, thus indicating extraordinary high lake productivity. © 2014 Author(s).
cited By 44

Past freeze and thaw cycling in the margin of the El'gygytgyn crater deduced from a 141 m long permafrost record - Schwamborn, G.; Meyer, H.; Schirrmeister, L.; Fedorov, G. (Climate of the Past, 2014)
The continuous sediment record from Lake El'gygytgyn in the northeastern Eurasian Arctic spans the last 3.6 Ma and for much of this time permafrost dynamics and lake level changes have likely played a crucial role for sediment delivery to the lake. Changes in the ground-ice hydrochemical composition (δ18O, δD, pH, electrical conductivity, Na+, Mg2+, Ca2+, K+, HCO3-, Cl-, SO4-) of a 141 m long permafrost record from the western crater plain are examined to reconstruct repeated periods of freeze and thaw at the lake edge. Stable water isotope and major ion records of ground ice in the permafrost reflect both a synsedimentary palaeo-precipitation signal preserved in the near-surface permafrost (0.0-9.1 m core depth) and a post-depositional record of thawing and refreezing in deeper layers of the core (9.1-141.0 m core depth). These lake marginal permafrost dynamics were controlled by lake level changes that episodically flooded the surfaces and induced thaw in the underlying frozen ground. During times of lake level fall these layers froze over again. At least three cycles of freeze and thaw are identified and the hydrochemical data point to a vertical and horizontal talik refreezing through time. Past permafrost thaw and freeze may have destabilised the basin slopes of Lake El'gygytgyn and this has probably promoted the release of mass movements from the lake edge to the deeper basin as known from frequently occurring turbidite layers in the lake sediment column. © Author(s) 2014.
cited By 8
Keywords: data set; freeze-thaw cycle; lacustrine deposit; mass movement; metal; permafrost; precipitation (climatology); sediment analysis; turbidity; Chukchi; Elgygytgyn Lake; Russian Federation

Origin and palaeoenvironmental significance of C25 and C27 n-alk-1-enes in a 25,000-year lake-sedimentary record from equatorial East Africa - Van Bree, L.G.J.; Rijpstra, W.I.C.; Cocquyt, C.; Al-Dhabi, N.A.; Verschuren, D.; Sinninghe Damst'e, J.S.; Leeuw, J.W. (Geochimica et Cosmochimica Acta, 2014)
We studied the distribution of long-chain alkenes (n-C23 to n-C31) in well-dated sediments from Lake Challa, a deep crater lake near Mt. Kilimanjaro in equatorial East Africa, to reveal signatures of palaeo-environmental and palaeo-climatic changes affecting the production of these compounds during the last 25kyr. The apolar fractions of organic sediment extracts dated to the last 16kyr showed an unusual dominance of δ13C-depleted n-C25:1 and n-C27:1 alk-1-enes. These alkenes were not detected in soil and litter from near the shoreline and from the inner rim of the crater, pointing to an autochthonous, aquatic source. Analysis of suspended particulate matter indicated that the n-alk-1-enes are produced in the well-oxygenated upper 30m of the water column, indicating a phytoplanktonic origin. Sedimenting particles collected monthly from December 2006 to November 2007 showed increased fluxes of n-alk-1-enes following the locally prominent short rain season in November-December. Green algae and/or cyanobacteria were identified as candidate sources of these alkenes. Production of the n-C25:1 and n-C27:1 alkenes in Lake Challa was much reduced during the Last Glacial Maximum and early late-glacial period, suggesting a temperature or CO2 effect on habitat suitability. We explored the potential of n-alk-1-ene accumulation rates, and of a derived Alkene Index [n-C27:1]/([n-C25:1]+[n-C27:1]), to record longer-term climatic changes. The Alkene Index record of Lake Challa over the past 25kyr shows clear periodicity with a dominant frequency of 2.3kyr, potentially indicative of monsoon variability directly or indirectly forced by variation in solar radiation. © 2014 Elsevier Ltd.
cited By 16
Keywords: accumulation rate; alkene; climate variation; cyanobacterium; geological record; green alga; lacustrine deposit; Last Glacial Maximum; monsoon; paleoclimate; paleoenvironment; solar radiation; suspended particulate matter; Kilimanjaro [Kilimanjaro (RGA)]; Kilimanjaro [Tanzania]; Lake Challa; Tanzania

Paleoenvironmental conditions define current sustainability of microbial populations in Laguna Potrok Aike sediments, Argentina - Vuillemin, Aurèle; Ariztegui, Daniel; L{ucke, Andreas; Mayr, Christoph (Aquatic Sciences, 2014)

Paleomagnetism of Lake Van sediments: Chronology and paleoenvironment since 350ka - Vigliotti, L.; Channell, J.E.T.; Stockhecke, M. (Quaternary Science Reviews, 2014)
In the framework of the PALEOVAN project, a high-resolution paleomagnetic and rock magnetic study was carried out on a 149m sedimentary sequence recovered from Ahlat Ridge in the deepest part of the Lake Van (Eastern Turkey; ICDP Site 5034-2). High sedimentation rates (average 30cm/ka) allow high-resolution measurements of natural remanent magnetization (NRM), magnetic susceptibility (κ), anhysteretic remanence (ARM) and hence of anhysteretic susceptibility (κARM) over the last 350ka. The carrier of the remanence is detrital titanomagnetite largely from volcanic sources, based on the similarity of magnetite grain size of tephra layers and the other lacustrine lithologies observed in a plot of the κ versus κARM. Bulk magnetic parameters often covary with paleoclimatic signals in the Lake Van sediments. A correlation exists between variations of κ and ARM intensity and glacial-interglacial marine isotopic stages, as well as dust flux and temperatures observed in ice cores from Greenland and Antarctica. The quality of the paleomagnetic record is compromised by weak NRM intensities, as well as by the presence of tephra and turbidites throughout the sequence. Nonetheless, a correlation is observed between the relative paleointensity (RPI) record, based on NRM/ARM, and the calibrated PISO RPI stack, that supports the independently derived age model for the site. © 2014 Elsevier Ltd.
cited By 25
Keywords: Lacustrine sediments; Lake vans; Late quaternary; Paleoclimates; Paleomagnetism; grain size; lacustrine deposit; magnetic intensity; magnetic susceptibility; natural remanent magnetization; paleoclimate; paleoenvironment; paleomagnetism; Quaternary; sedimentary sequence; sedimentation rate; tephra; Lake Van; Turkey

Past freeze and thaw cycling in the margin of the El'gygytgyn crater deduced from a 141 m long permafrost record - Schwamborn, G.; Meyer, H.; Schirrmeister, L.; Fedorov, G. (Climate of the Past, 2014)

Pilot testing of handling the fluids from the IDDP-1 exploratory geothermal well, Krafla, N.E. Iceland - Hauksson, Trausti; Markusson, Sigurdur; Einarsson, Kristj'an; Karlsd'ottir, Sigrun Nanna; Einarsson, 'Asbj{orn; M{oller, Aðalsteinn; Sigmarsson, Þorsteinn (Geothermics, 2014)
Material tests and scrubbing experiments were carried out at the IDDP-1 well in the Krafla geothermal field in Iceland. The 450°C superheated steam contained acid gas (approx. 90mg/kg HCl and 7mg/kg HF) and was highly corrosive when it condensed making it unsuitable for utilization without scrubbing. The acid gas could effectively be scrubbed from the steam with water. The steam contained gasous sulfur compond (80 –100mg/kgS), which could only be scrubbed from the steam with alkaline water. The steam contained both silica dust and dissolved silica which was effectively washed from the steam with wet scrubbing. Experiments on corrosion and erosion resistance of metals and alloys were problematic to run because of equipment clogging by silica dust.
Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma
Keywords: Steam scrubbing; Acid; Sulfur; Silica dust

Morphology and ultrastructure of Hippodonta qinghainensis sp. Nov. (bacillariophyceae), a new diatom from lake Qinghai, China - Peng, Yumei; Rioual, Patrick; Levkov, Zlatko; Wiliams, David M; Jin, Zhangdong (Phytotaxa, 2014)
A new medium-sized species of Hippodonta (Bacillariophyceae) is described from Lake Qinghai, China. The morphology and ultrastructure of Hippodonta qinghainensis sp. nov. are described using light and scanning electron microscopy. This new species is compared with similar species of Hippodonta using conventional and geometric morphometric analyses. Hippodonta qinghainensis can be separated from the other species of Hippodonta by a unique combination of characters that include an elliptic-lanceolate to rhombic-lanceolate valve shape, non protracted apices, the absence of fascia, relatively coarse, uniseriate striae and the presence of two rows of lineolae around the valves apices. © 2014 Magnolia Press.
Keywords: Bacillariophyceae; Bacillariophyta; Hippodonta

New isotopic and geochemical data from the Palaeoproterozoic Pechenga Greenstone Belt, NW Russia: Implication for basin development and duration of the volcanism - Hanski, Eero J; Huhma, Hannu; Melezhik, Victor A (Precambrian Research, 2014)

Late Cretaceous palynology and paleoclimate change: Evidence from the SK1 (South) core, Songliao Basin, NE China - Zhao, J.; Wan, X.Q.; Xi, D.P.; Jing, X.; Li, W.; Huang, Q.H.; Zhang, J.Y. (Science China Earth Sciences, 2014)
Cretaceous climate was warmer than today. The Songliao Basin contains one of the most important Late Cretaceous non-marine deposits in China for the research of the paleoenvironment and paleoclimate. This research is based on core samples from the SK1(S) borehole. The strata sampled are the upper part of the Quantou Formation to member 2 of the Nenjiang Formation, where spores, pollen, dinoflagellates, and other microfossils are abundantly preserved. Based on analysis of the spores and pollen fossils from the core samples, the following six fossil assemblage zones have been recognized in ascending order: The Cicatricosisporites-Cyathidites-Pinuspollenites, Schizaeoisporites-Cyathidites-Classopollis, Cyathidites-Schizaeoisporites, Schizaeoisporites-Cyathidites-Proteacidites, Proteacidites-Cyathidites-Dictyotriletes, and the Lythraites-Callistipollenites-Schizaeoisporites zones. The six fossil zones range from the late Cenomanian to early Campanian. The Late Cretaceous dinoflagellate cysts in the Songliao Basin are of high abundance and low diversity. Specific phytoplankton types reflect salinity changes of the Songliao Lake. Paleoecology of the dinoflagellates suggests that sediments of members 2 and 3 of the Yaojia Formation (K2y2+3) were deposited in a freshwater environment, whereas members 2 and 3 of the Qingshankou Formation (K2q2+3) and members 1 and 2 of the Nenjiang Formation (K2n1+2) were deposited in freshwater to brackish water environments. Combined with the paleoecology of dinoflagellates and the palynomorph biozones, valuable information of the paleoclimate was provided. The quantitative analyses of spores and pollen fossils, such as vegetation type, climate type, and humidity type, diversity and dominance, indicate a relatively sub-humid, mid-subtropical paleoclimate, with slight climatic fluctuation and/or temporal change. © 2014, Science China Press and Springer-Verlag Berlin Heidelberg.
cited By 32
Keywords: Climate change; Ecology; Water; dinoflagellate; Late cretaceous; Paleoclimates; Songliao basin; spores and pollen; Core samples; borehole; climate variation; Cretaceous; dinoflagellate cyst; dominance; fossil assemblage; microfossil; paleoclimate; paleoecology; paleoenvironment; palynology; sediment core; species diversity; warming; China; Songliao Basin; Dinophyceae

More than one million years of history in Lake Ohrid cores - Wagner, Bernd; Wilke, Thomas; Krastel, Sebastian; Zanchetta, Giovanni; Sulpizio, Roberto; Reicherter, Klaus; Leng, Melanie; Grazhdani, Andon; Trajanovski, Sasho; Levkov, Zlatko; Reed, Jane; Wonik, Thomas (Eos, 2014)
Continental scientific drilling is an important tool for exploring natural and anthropogenic processes on Earth. In past decades the results obtained from lake drilling projects contributed significantly to a better understanding of short-term and long-term climate change and natural hazards. ©2014. American Geophysical Union. All Rights Reserved.
Keywords: Lake Ohrid; climate variation; core analysis; deep drilling; lacustrine deposit; natural hazard; paleoclimate; paleolimnology; paleontology; stratigraphic correlation; Earth

Late Pliocene and Early Pleistocene vegetation history of northeastern Russian Arctic inferred from the Lake El'gygytgyn pollen record - Andreev, A. A.; Tarasov, P. E.; Wennrich, V.; Raschke, E.; Herzschuh, U.; Nowaczyk, N. R.; Brigham-Grette, J.; Melles, M. (Climate of the Past, 2014)
The 318m thick lacustrine sediment record from Lake El'gygytgyn, northeastern Russian Arctic cored by the international El'gygytgyn Drilling Project provides unique opportunities for the time-continuous reconstruction of the regional paleoenvironmental history for the past 3.6 Myr. Pollen studies of the lower 216m of the lacustrine sediments demonstrate their value as an excellent archive of vegetation and climate changes during the Late Pliocene and Early Pleistocene. About 3.5-3.35 Myr BP, the vegetation at Lake El'gygytgyn, now an area of tundra was dominated by spruce-larch-fir-hemlock forests. After ca. 3.35 Myr BP dark coniferous taxa gradually disappeared. A very pronounced environmental change took place ca. 3.31-3.28 Myr BP, corresponding to the Marine Isotope Stage (MIS) M2, when treeless tundra- and steppe-like habitats became dominant in the regional vegetation. Climate conditions were similar to those of Late Pleistocene cold intervals. Numerous coprophilous fungi spores identified in the pollen samples suggest the presence of grazing animals around the lake. Following the MIS M2 event, larch-pine forests with some spruce mostly dominated the area until ca. 2.6 Myr BP, interrupted by colder and drier intervals ca. 3.043-3.025, 2.935-2.912, and 2.719-2.698 Myr BP. At the beginning of the Pleistocene, ca. 2.6 Myr BP, noticeable climatic deterioration occurred. Forested habitats changed to predominantly treeless and shrubby environments, which reflect a relatively cold and dry climate. Peaks in observed green algae colonies (Botryococcus) around 2.53, 2.45, 2.32-2.305, 2.20 and 2.16-2.15 Myr BP suggest a spread of shallow water environments. A few intervals (i.e., 2.55-2.53, ca. 2.37, and 2.35-2.32 Myr BP) with a higher presence of coniferous taxa (mostly pine and larch) document some relatively shortterm climate ameliorations during Early Pleistocene glacial periods. © Author(s) 2014.
cited By 36
Keywords: climate variation; coniferous forest; glacial history; green alga; lacustrine deposit; marine isotope stage; paleoenvironment; palynology; Pleistocene; Pliocene; reconstruction; sediment analysis; spore; vegetation history; Arctic; Chukchi; Elgygytgyn Lake; Russian Federation

Potential influence of sulphur bacteria on Palaeoproterozoic phosphogenesis - Lepland, A.; Joosu, L.; Kirsim{ae, K.; Prave, A.R.; Romashkin, A.E.; Črne, A.E.; Fallick, A.E.; Somelar, P.; {Upraus, K.; M{and, K.; Roberts, N.M.W.; Van Zuilen, M.A.; et al. (Nature Geoscience, 2014)
All known forms of life require phosphorus, and biological processes strongly influence the global phosphorus cycle. Although the record of life on Earth extends back to 3.8 billion years ago and the advent of biological phosphate processing can be tracked to at least 3.5 billion years ago, the earliest known P-rich deposits appeared only 2 billion years ago. The onset of P deposition has been attributed to the rise of atmospheric oxygen 2.4-2.3 billion years ago and the related profound biogeochemical shifts, which increased the riverine input of phosphate to the ocean and boosted biological productivity and phosphogenesis. However, the P-rich deposits post-date the rise of oxygen by about 300 million years. Here we use microfabric, trace element and carbon isotope analyses to assess the environmental setting and redox conditions of the 2-billion-year-old P-rich deposits of the vent-or seep-influenced Zaonega Formation, northwest Russia. We identify phosphatized microorganism fossils that resemble modern methanotrophic archaea and sulphur-oxidizing bacteria, analogous to organisms found in modern seep settings and upwelling zones with a sharp redoxcline. We therefore propose that the P-rich deposits in the Zaonega Formation were formed by phosphogenesis mediated by sulphur bacteria, similar to modern sites, and by the precipitation of calcium phosphate minerals on microbial templates during early diagenesis. © 2014 Macmillan Publishers Limited.
cited By 44

Lake level and climate records of the last 90ka from the Northern Basin of Lake Van, eastern Turkey - Çağatay, M.N.; {Oğretmen, N.; Damci, E.; Stockhecke, M.; Sancar, {U.; Eriş, K.K.; {Ozeren, S. (Quaternary Science Reviews, 2014)
Sedimentary, geochemical and mineralogical analyses of the ICDP cores recovered from the Northern Basin (NB) of Lake Van provide evidence of lake level and climatic changes related to orbital and North Atlantic climate system over the last 90ka. High lake levels are generally observed during the interglacial and interstadial periods, which are marked by deposition of varved sediments with high total organic carbon (TOC), total inorganic carbon (TIC), low detrital influx (high Ca/F) and high δ18O and δ13C values of authigenic carbonate. During the glacial and stadial periods of 71-58kaBP (Marine Isotope Stage 4, MIS4) and end of last glaciation-deglaciation (30-14.5kaBP; MIS3) relatively low lake levels prevailed, and grey homogeneous to faintly laminated clayey silts were deposited at high sedimentation and low organic productivity rates.Millennial-scale variability of the proxies during 60-30kaBP (MIS3 is correlated with the Dansgaard-Oeschger (D-O)) and Holocene abrupt climate events in the Atlantic. These events are characterized by laminated sediments, with high TOC, TIC, Ca/Fe, δ18O and δ13C values. The Lake Van NB records correlate well in the region with the climate records from the lakes Zeribar and Urmia in Iran and the Sofular Cave in NW Anatolia, but are in general in anti-phase to those from the Dead Sea Basin (Lake Lisan) in the Levant. The relatively higher δ18O values (0 to-0.4‰) for the interglacial and interstadial periods in the Lake Van NB section are due to the higher temperature and seasonality of precipitation and higher evaporation, whereas the lower values (-0.8 to-2‰) during the glacial and stadial periods are caused mainly by relative decrease in both temperature and seasonality of precipitation. The high δ18O values (up to 4.2‰) during the Younger Dryas, together with the presence of dolomite and low TOC contents, supports evaporative conditions and low lake level. A gradual decrease in the δ18O values from an average of-0.4‰ during the humid early Holocene to an average of-3.5‰ during the more arid late Holocene suggests an increasing contribution of winter precipitation. The changes in the seasonality of precipitation in eastern Anatolia are probably caused by changes in the temperatures of North Atlantic and Mediterranean and in the strength of Siberian High. © 2014 Elsevier Ltd.
cited By 73
Keywords: Climate record; ICDP PaleoVan; Lake levels; Lake vans; Multproxy analyses; Northern basins; authigenesis; climate variation; Dansgaard-Oeschger cycle; Holocene; interstadial; lake level; marine isotope stage; paleoclimate; precipitation (climatology); proxy climate record; Anatolia; Atlantic Ocean; Iran; Kordestan; Lake Urmia; Lake Van; Lake Zeribar; Levant; Mediterranean Region; Turkey

Lake Van deep drilling project PALEOVAN - Litt, T.; Anselmetti, F.S. (Quaternary Science Reviews, 2014)
A complete succession of the lacustrine sediment sequence deposited during the last 600,000 years in Lake Van, Eastern Anatolia (Turkey) was drilled in 2010 supported by the International Continental Scientific Drilling Program (ICDP). Based on a detailed seismic site survey, two sites at a water depth of up to 360m were drilled in summer 2010, and cores were retrieved from sub-lake-floor depths of 140m (Northern Basin) and 220m (Ahlat Ridge). To obtain a complete sedimentary section, the two sites were multiple cored in order to investigate the paleoclimate history of a sensitive semi-arid region between the Black, Caspian, and Mediterranean seas. This introductory paper provides background information of the deep drilling project and an overview of the studies presented in this special volume by the PALEOVAN science team dealing with chronology, paleomagnetism, paleoenvironmental proxies, geophysical and petrophysical investigations as well as pore-water and fluid transport. © 2014 Elsevier Ltd.
cited By 33
Keywords: Deep drilling; Lake vans; Long continental record; Near East; Quaternary; deep drilling; lacustrine deposit; paleoclimate; Quaternary; sediment core; seismic survey; semiarid region; Lake Van; Turkey

Late cretaceous-early paleocene ostracod biostratigraphy of scientific drilling Sk1(N) in the Songliao Basin, northeast China - Qu, H.; Xi, D.; Li, S.; Colin, J.P.; Huang, Q.; Wan, X. (Journal of Paleontology, 2014)
Cretaceous non-marine deposits are widespread in China and have been studied comprehensively. The Songliao Basin in northeast China is thought to be well suited for investigation of Cretaceous biostratigraphy. However, despite much research having been conducted in the basin, little is known about its Late Cretaceous biostratigraphy and paleoenvironment. Here, we establish a high-resolution biostratigraphy of the Late Cretaceous based on ostracods from borehole SK1(n) in the Songliao Basin, northeast China. As part of the present study, 45 species assigned to 20 genera have been recovered, with one new species (Ilyocypris bisulcata n. sp.) and five ostracod assemblages: the Cypridea gunsulinensis-Mongolocypris magna assemblage, which is marked by the first occurrence (F.O.) of Ilyocyprimorpha with nodes and spines; the Ilyocyprimorpha-Limnocypridea sunliaonensis-Periacanthella assemblage, which ranges from the F.O. of Ilyocyprimorpha with nodes and spines to the F.O. of Strumosia sp.; the Strumosia inandita assemblage from the F.O. of Strumosia sp. to the lower occurrence (L.O.) of Strumosia inandita; the Talicypridea amoena-Metacypris kaitunensis-Ziziphocypris simakovi assemblage from the F.O. of Mongolocypris apiculata (Cea) and Talicypridea amoena to the F.O. of Ilyocypris sp.; and the Ilyocypris assemblage from the F.O. of Ilyocypris sp. to the L.O. of Ilyocypris bisulcata n. sp. Moreover, the zonal fossil Ilyocypris bisulcata n. sp. of Zone 5 is here described for the first time from the upper Mingshui Formation, and Paleocene charophyte genera including Neochara and Grovesicahra have been found to coexist with the Zone 5 fauna. The age of the Ilyocypris Assemblage is assigned to the latest Maastrichtian to the earliest Danian. Copyright © 2014, The Paleontological Society.
cited By 29
Keywords: biostratigraphy; community structure; Cretaceous; Danian; fossil record; Maastrichtian; new species; ostracod; Paleocene; paleoenvironment; taxonomy; China; Songliao Basin

Late Eocene to middle Miocene (33 to 13 million years ago) vegetation and climate development on the North American Atlantic Coastal Plain (IODP Expedition 313, Site M0027) - Kotthoff, U.; Greenwood, D.R.; McCarthy, F.M.G.; M{uller-Navarra, K.; Prader, S.; Hesselbo, S.P. (Climate of the Past, 2014)
We investigated the palynology of sediment cores from Site M0027 of IODP (Integrated Ocean Drilling Program) Expedition 313 on the New Jersey shallow shelf to examine vegetation and climate dynamics on the east coast of North America between 33 and 13 million years ago and to assess the impact of over-regional climate events on the region. Palynological results are complemented with pollen-based quantitative climate reconstructions. Our results indicate that the hinterland vegetation of the New Jersey shelf was characterized by oak-hickory forests in the lowlands and conifer-dominated vegetation in the highlands from the early Oligocene to the middle Miocene. The Oligocene witnessed several expansions of conifer forest, probably related to cooling events. The pollen-based climate data imply an increase in annual temperatures from ∼11.5 °C to more than 16 °C during the Oligocene. The Mi-1 cooling event at the onset of the Miocene is reflected by an expansion of conifers and mean annual temperature decrease of ∼4 °C, from ∼16 °C to ∼12 °C around 23 million years before present. Relatively low annual temperatures are also recorded for several samples during an interval around ∼20 million years before present, which may reflect the Mi-1a and the Mi-1aa cooling events. Generally, the Miocene ecosystem and climate conditions were very similar to those of the Oligocene. Miocene grasslands, as known from other areas in the USA during that time period, are not evident for the hinterland of the New Jersey shelf, possibly reflecting moisture from the proto-Gulf Stream. The palaeovegetation data reveal stable conditions during the mid-Miocene climatic optimum at ∼15 million years before present, with only a minor increase in deciduous-evergreen mixed forest taxa and a decrease in swamp forest taxa. Pollen-based annual temperature reconstructions show average annual temperatures of ∼14 °C during the mid-Miocene climatic optimum, ∼2 °C higher than today, but ∼1.5 °C lower than preceding and following phases of the Miocene. We conclude that vegetation and regional climate in the hinterland of the New Jersey shelf did not react as sensitively to Oligocene and Miocene climate changes as other regions in North America or Europe due to the moderating effects of the North Atlantic. An additional explanation for the relatively low regional temperatures reconstructed for the mid-Miocene climatic optimum could be an uplift of the Appalachian Mountains during the Miocene, which would also have influenced the catchment area of our pollen record. © Author(s) 2014.
cited By 29
Keywords: climate variation; Eocene; Miocene; paleoclimate; palynology; reconstruction; regional climate; sediment core; Atlantic Coastal Plain; New Jersey; United States

Late Glacial to Holocene climate change and human impact in the Mediterranean: The last ca. 17ka diatom record of Lake Prespa (Macedonia/Albania/Greece) - Cvetkoska, Aleksandra; Levkov, Zlatko; Reed, Jane M.; Wagner, Bernd (Palaeogeography, Palaeoclimatology, Palaeoecology, 2014)
Lake Prespa (Macedonia/Albania/Greece) occupies an important location between Mediterranean and central European climate zones. Although previous multi-proxy research on the Late Glacial to Holocene sequence, core Co1215 (320cm; ca. 17cal ka BP to present), has demonstrated its great value as an archive of Quaternary palaeoclimate data, some uncertainty remains in the interpretation of climate change. With the exception of oxygen stable isotope data, previous palaeolimnological interpretation has relied largely on proxies for productivity. Here, existing interpretation is strengthened by the addition of diatom data. Results demonstrate that shifts in diatom assemblage composition are driven primarily by lake-level changes and thus permit more confident interpretation of shifts in moisture availability over time, while corroborating previous interpretation of catchment- and climate-induced productivity shifts. An inferred cold, arid shallow lake phase between ca. 17.1 and 15.7cal ka BP is not only followed by a high-productivity phase from ca. 15.7cal ka BP with Late Glacial warming, but also is the first evidence for a gradual increase in lake level, in line with other regional records. Clear evidence for a Younger Dryas climate reversal between ca. 13.1 and 12.3cal ka BP is followed by an unusually gradual transition to the Holocene and deeper, oligotrophic-mesotrophic lake conditions are reached by ca. 11.0cal ka BP. In contrast to the arid episode from ca. 10.0 to 8.0ka inferred from positive 18δOcalcite values, rapid diatom-inferred lake-level increase after the start of the Holocene suggests high moisture availability, in line with palynological evidence, but with only very subtle evidence for the impact of an 8.2ka cold event. The maintenance of high lake levels until 1.9cal ka BP, and the peak of inferred humidity from ca. 7.9 to 6.0cal ka BP, matches the oxygen stable isotope profile and confirms that the latter is driven primarily by evaporative concentration rather than reflecting regional shifts in precipitation sources over time. During the Late Holocene progressive eutrophication is inferred between 1.9 and present. Two shallow phases at ca. 1.0cal ka BP and at ca. 100years ago probably represent an aridity response which is added to increase human impact in the catchment. Overall, the study is important in confirming previous tentative inferences that Late Glacial to Holocene moisture availability has strong affinity with other sites in the Eastern Mediterranean. It also tracks the pattern of North Atlantic forcing. © 2014 Elsevier B.V.
Keywords: Albania; Greece; Lake Mikri Prespa; Macedonia [Greece]; anthropogenic effect; aridity; climate variation; community composition; diatom; Holocene; lake level; late glacial; Mediterranean environment; moisture content; paleoclimate; paleoecology; paleolimnology; paleoproductivity; palynology; Younger Dryas

Lithology of the long sediment record recovered by the ICDP Dead Sea Deep Drilling Project (DSDDP) - Neugebauer, I.; Brauer, A.; Schwab, M.J.; Waldmann, N.D.; Enzel, Y.; Kitagawa, H.; Torfstein, A.; Frank, U.; Dulski, P.; Agnon, A.; Ariztegui, D.; Ben-Avraham, Z.; et al. (Quaternary Science Reviews, 2014)
The sedimentary sections that were deposited from the Holocene Dead Sea and its Pleistocene precursors are excellent archives of the climatic, environmental and seismic history of the Levant region. Yet, most of the previous work has been carried out on sequences of lacustrine sediments exposed at the margins of the present-day Dead Sea, which were deposited only when the lake surface level rose above these terraces (e.g. during the Last Glacial period) and typically are discontinuous due to major lake level variations in the past. Continuous sedimentation can only be expected in the deepest part of the basin and, therefore, a deep drilling has been accomplished in the northern basin of the Dead Sea during winter of 2010-2011 within the Dead Sea Deep Drilling Project (DSDDP) in the framework of the ICDP program. Approximately 720m ofsediment cores have been retrieved from two deep and several short boreholes. The longest profile (5017-1), revealed at a water depth of 300m, reaches 455m below the lake floor (blf, i.e. to 1175m below global mean sea level) and comprises approximately the last 220-240ka. The record covers the upper part of the Amora (penultimate glacial), the Last Interglacial Samra,the Last Glacial Lisan and the Holocene Ze'elim Formations and, therewith, two entire glacial-interglacial cycles. Thereby, for the first time, consecutive sediments deposited during the MIS 6/5, 5/4 and 2/1 transitions were recovered from the Dead Sea basin, which are not represented in sediments outcropping on the present-day lake shores. In this paper, we present essential lithological data including continuous magnetic susceptibility and geochemical scanning data and the basic stratigraphy including first chronological data of the long profile (5017-1) from the deep basin. The results presented here (a) focus on the correlation of the deep basin deposits with main on-shore stratigraphic units, thus providing a unique comprehensive stratigraphic framework for regional paleoenvironmental reconstruction, and (b) highlight the outstanding potential of the Dead Sea deep sedimentary archive to record hydrological changes during interglacial, glacial and transitional intervals. © 2014 Elsevier Ltd.
cited By 86
Keywords: Glacial geology; Infill drilling; Lakes; Lithology; Magnetic susceptibility; Salinity measurement; Sea level; Sedimentology; Stratigraphy; Deep drilling; Hypersaline lakes; Laminated sediments; Paleoclimates; Sediment facies; Sediments; deep drilling; depositional sequence; facies; Holocene; hypersaline environment; lithology; magnetic susceptibility; ocean basin; outcrop; paleoclimate; paleoenvironment; sediment core; sedimentation; sequence stratigraphy; water depth; Dead Sea

Modern seasonality in Lake Challa (Kenya/Tanzania) and its sedimentary documentation in recent lake sediments - Wolff, Christian; Kristen-Jenny, Iris; Schettler, Georg; Plessen, Birgit; Meyer, Hanno; Dulski, Peter; Naumann, Rudolf; Brauer, Achim; Verschuren, Dirk; Haug, Gerald H. (Limnology and Oceanography, 2014)
From November 2006 to January 2010, a sediment trap that was cleared monthly was deployed in Lake Challa, a deep stratified freshwater lake on the eastern slope of Mt. Kilimanjaro in southern Kenya. Geochemical data from sediment trap samples were compared with a broad range of limnological and meteorological parameters to characterize the effect of single parameters on productivity and sedimentation processes in the crater basin. During the southern hemisphere summer (November–March), when the water temperature is high and the lake is biologically productive (nondiatom algae), calcite predominated in the sediment trap samples. During the “long rain” season (March–May) a small amount of organic matter and lithogenic material caused by rainfall appeared. This was followed by the cool and windy months of the southern hemisphere winter (June–October) when diatoms were the main component, indicating a diatom bloom initiated by improvement of nutrient availability related to upwelling processes. The sediment trap data support the hypothesis that the light–dark lamination couplets, which are abundant in Lake Challa cores, reflect seasonal delivery to the sediments of diatom-rich particulates during the windy months and diatom-poor material during the wet season. However, interannual and spatial variability in upwelling and productivity patterns, as well as El Niño–Southern Oscillation (ENSO)-related rainfall and drought cycles, exert a strong influence on the magnitude and geochemical composition of particle export to the hypolimnion of Lake Challa.

Long-term freshening of the Dead Sea brine revealed by porewater Cl- and δO18 in ICDP Dead Sea deep-drill - Lazar, B.; Sivan, O.; Yechieli, Y.; Levy, E.J.; Antler, G.; Gavrieli, I.; Stein, M. (Earth and Planetary Science Letters, 2014)
The geological evolution of the unique Dead Sea Ca-chloride brine has been the focus of many research efforts for several decades. These studies relied on the information obtained from sedimentary exposures of the marginal terraces of the modern Dead Sea, mostly documenting the history of the surface lake brine during its high stands periods. The present study is the first attempt to establish the history of the deepest part of the lake by direct measurements of the chemical and isotopic composition of pore-fluids that were extracted from cores drilled during 2011 by ICDP in the deep basin of the Dead Sea at water depth of 300 m. The vertical profiles of chloride (Cl-) and oxygen isotopes (δO18) in pore brines reveal a substantial decrease in the salinity of the hyper-saline lake during the last glacial and particularly during MIS2 ( 31-17 kaBP). The Cl- concentration of the deep brine in the lake decreased gradually, reaching a minimum of less than 2/3 of its present value while the δO18 increased to maximum of 7‰ (3‰ higher than today). The low Cl- indicates significant dilution of the bottom water mass (hypolimnion) of Lake Lisan (the last glacial predecessor of the modern Dead Sea) during its highest stand period. Beforehand, during the interglacial and later during the post-glacial and the Holocene the Cl- concentrations and δO18 values were similar to those of the modern Dead Sea. The slow dilution of the deep Ca-chloride brine was caused probably by continuous turbulent mixing of the hypolimnion with the less saline high δO18 epilimnetic brine, across the epilimnion/hypolimnion interface (EHI). While the increase in δO18 during the salinity decrease of Lake Lisan is a result of normal evaporation of the less saline epilimnetic brine, the post-glacial δO18 decrease (contemporaneous with salinity increase) is attributed to the reversed behavior of δO18 during evaporation of high salinity brine. During the long freshening period the hypolimnion was enriched with dissolved sulfate supplied by the freshwater and transported by the turbulent mixing across the EHI until reaching gypsum saturation that commenced massive gypsum deposition at the end of this period, when full overturn took place. © 2014 Elsevier B.V.
cited By 24
Keywords: Calcium; Chlorine; Chlorine compounds; Evaporation; Glacial geology; Gypsum; Isotopes; Lakes; Mixing; Oxygen; Paleolimnology; Shock tubes; Turbulent flow; Chloride; Dead sea; Oxygen isotopes; Pore brine profiles; Quarter-nary; Brines; brine; Chinese Continental Scientific Drilling Project; chloride; isotopic composition; oxygen isotope; paleolimnology; Quaternary; Dead Sea

Magnetic fabrics in deformed metaperidotites of the Outokumpu Deep Drill Core, Finland: Implications for a major crustal shear zone - Kontny, Agnes; Dietze, Frank (Tectonophysics, 2014)
The Outokumpu (OKU) assemblage was studied in drill cores from the 2516m deep OKU Deep Drill Hole, Finland, and we observed that the strongest magnetic anomalies found in borehole measurements are related to three ferrimagnetic metaperidotite units with magnetic susceptibilities of up to 93×10-3SI separated by paramagnetic rock units. The main ferrimagnetic minerals are magnetite and minor pyrrhotite. Magnetic fabric studies were done in order to examine deformation within the OKU assemblage during the collisional deformation event 1.9Ga ago. Well-defined magnetic axes (kmax, kmin) and nearly horizontal magnetic foliation subparallel to the macroscopic foliation occur at the top and the bottom of the OKU formation. Low- and high-field AMS measurements showed that ferri- and paramagnetic subfabrics are coaxial. Paramagnetic units intercalated between the ferrimagnetic units show mostly triaxial magnetic fabrics, and low degrees of magnetic anisotropy values (P'<1.3) with a high variation of the shape factor (T) from prolate to oblate shapes. P' of the ferrimagnetic metaperidotite is high and range between 1.3 and 3.6 and T tends to more oblate shapes (T>0). Ferrimagnetic unit 2 shows the highest magnetic susceptibility and P' up to 5.6, which is related to a high amount of magnetite and pyrrhotite mostly concentrated in huge aggregates and veins. Alignment of magnetic minerals parallel with the structural foliation and the high P' values in the ferrimagnetic metaperidotite indicate that magnetic fabric was acquired in a high strain zone. The magnetic fabrics represent shear zone (SC) fabrics, which have been formed during early obduction-related deformation of the Svecofennian orogeny. The stacked sequence of the ferri- and paramagnetic metaperidotite bodies can be interpreted as a thrust system with an imbricate fan, in which three individual listric thrust sheets occur. This interpretation is in accordance with previous tectonic models of the Outokumpu area. © 2014 Elsevier B.V.
Keywords: Finland; Outokumpu; Pohjois-Karjala; Deformation; Drills; Ferrimagnetism; Horizontal wells; Infill drilling; Iron ores; Magnetic anisotropy; Magnetic susceptibility; Magnetite; Paramagnetism; Core drilling; Magnetism; Tectonics; Borehole measurements; Deep drilling; Ferrimagnetic minerals; Finland; Magnetic anomalies; Magnetic fabrics; Magnetic foliation; Outokumpu area; High-strain zones; Magnetic minerals; crustal structure; deformation; magnetic anisotropy; magnetic anomaly; magnetic fabric; magnetic mineral; magnetic susceptibility; peridotite; shear zone; deep drilling; geomagnetism; petrofabric; tectonic setting; Core drilling; Magnetic anisotropy

Magnetic susceptibility logging of Chicxulub proximal impact breccias in the Santa Elena borehole: Implications for emplacement mode - Urrutia-Fucugauchi, J.; P'erez-Cruz, L.; Campos-Arriola, S.E.; Escobar-S'anchez, E.; Velasco-Villarreal, M. (Studia Geophysica et Geodaetica, 2014)
Magnetic susceptibility logging is used to study the impact breccias in the Chicxulub crater. The basic premise is that the high contrasts in magnetic properties can be used to characterize the breccias. The Santa Elena borehole was drilled 110 km radial distance from crater center and sampled a 172 m thick sequence of impact breccias, between 332 and 504 m depth. Breccia units are distinguished from differences in composition, size, and relative contents of clasts, type of matrix and textural and lithological assemblages, which can be resolved in the susceptibility logs. The whole-core log shows characteristic variation patterns with high, intermediate and low susceptibilities. High resolution logging of matrix and clasts records the heterogeneous nature of impactites, with higher variability at smaller spatial scales. Measurements confirm that diamagnetic susceptibilities characterize the carbonate clasts, high susceptibilities the basement granitic clasts and intermediate values the silicate melt-rich and silicate-poor matrix. Intermediate variable susceptibilities characterize breccias rich in melt particles. Correlation of matrix and clast logs with whole-core log shows that signal is controlled by the matrix. Logs for clast shows a discrete distribution with peaks of intermediate to high values, which correlate with large clast distributions. The ejecta blanket includes the fallback suevites rich in silicate melt particles and shocked minerals, the high temperature vapor deposits from ejecta curtain collapse and high velocity basal flows, and the carbonate rich deposits from lateral basal flows and secondary cratering. Late fallback suevites record minor turbulent conditions resulting from progressive cooling of the ejecta plume. © 2013 Institute of Geophysics of the ASCR, v.v.i.
cited By 6

Magnetostratigraphy of sediments from Lake El'gygytgyn ICDP Site 5011-1: paleomagnetic age constraints for the longest paleoclimate record from the continental Arctic - Haltia, E. M.; Nowaczyk, N. R. (Climate of the Past, 2014)
Paleomagnetic measurements were performed on sediments drilled from ICDP Site 5011-1 in Lake El'gygytgyn (67°30' N, 172°05' E) located in Far East Russian Arctic. The lake partly fills a crater formed by a meteorite impact 3.58 ± 0.04 Ma ago. Sediments from three parallel cores (5011-1A, 5011-1B and 5011-1C), recovered from the middle part of the lake, yield a total of 355 m of sediment. Sediments are characterized by a variable lithology, where intervals of homogenous and laminated sediments alternate, and mass movement deposits occur frequently along the sediment profile. Mineral magnetic investigation made on sediments enclosed in core catchers suggests that magnetic carrier in these sediments is partly maghemitized Ti-rich pseudo-single domain magnetite. Its detrital origin can be shown by mineral magnetic measurements and SEM-EDS analyses performed on mini-sized cylindrical rock samples, polished rock sections and creek sediments. The intensity of the natural remanent magnetization in the sediments is high with a range from about 1 to 1000 mA mg-1. Most of the sediments carry a stable magnetization interpreted as primary depositional remanent magnetization. Characteristic inclination data show alternating intervals of steep positive and negative inclinations that are used to assign magnetic polarity to the lake sediment profile. This is a rather straightforward procedure owing to the mainly high quality of data. The Matuyama/Gauss (M/G) (2.608 Ma) and Brunhes/Matuyama (B/M) (0.780 Ma) reversals were recognized in the sediments. The Mammoth and Kaena reversed subchrons were identified during the Gauss chron, and the Olduvai and Jaramillo normal subchrons as well as the R'eunion and Cobb Mountain cryptochrons were identified during the Matuyama chron. Sediments also provide a record of the Olduvai precursor and Intra-Jaramillo geomagnetic excursions. Sediment deposition rate is highest at the base of the sequence laid down in the early Gauss chron, when the deposition rate is approximately 44 cm kyr-1. Sediment deposition decelerates upcore and it is an order of magnitude lower during the Brunhes chron in comparison with the early Gauss chron. Decrease in sediment deposition in the late Pliocene probably relates to atmospheric and oceanic reorganization heralding the onset of Quaternary climate change. The high-quality magnetostratigraphy reconstructed from Lake El'gygytgyn sediments provides 12 first-order tie points to pin down the age of the longest paleoclimate record from the continental Arctic. © 2014 Author (s).
cited By 16
Keywords: climate variation; crater; deposition; lacustrine deposit; lamination; magnetite; magnetostratigraphy; mass movement; paleoclimate; paleomagnetism; Pliocene; proxy climate record; remanent magnetization; scanning electron microscopy; sediment core; Arctic; Chukchi; Elgygytgyn Lake; Russian Far East; Russian Federation

Modeling submarine landslide-generated waves in lake Ohrid, Macedonia/Albania - Lindhorst, Katja; Krastel, Sebastian; Papenberg, Cord; Heidarzadeh, Mohammed (Advances in Natural and Technological Hazards Research, 2014)
We study potential tsunami hazards associated with submarine landslides in Lake Ohrid, Macedonia/Albania. The transboundary Lake Ohrid located on the Balkan Peninsula shared by Macedonia and Albania is considered to be the oldestcontinuously existing lake in Europe (2 –5 Ma), though the age and the origin are not completely unraveled to date. Previous studies by means of hydroacoustic methods have shown that the western margin of Lake Ohrid has a long history of mass wasting. Based on seismic data, slide deposits are found in different stratigraphic levels as well as on the lake floor where they have affected a large area. This study is focused on the well-studied Udenisht Slide Complex covering an area of 27 km2 within the southwestern part of Lake Ohrid. The Udenisht slide is by far the largest mass movement with an average thickness of 30 –40 m and an estimated volume of about 0.11 km3. It is therefore well within the limits of submarine landslides that are known to be capable of triggering tsunamis. Using numerical modeling, the propagation of a landslide-generated tsunami with an initial wave height of more than 5 m has been calculated. Run-up heights estimated for coastal communities around the lake are moderate in the north (2 –3 m) can reach up to 10 m directly at the site where the slide initiated. This study is a first generation of landslide tsunami hazard assessment for Lake Ohrid and further detailed modeling is recommended for the region. © Springer International Publishing Switzerland 2014.

Modelling of temperature conditions near the bottom of well IDDP-1 in Krafla, Northeast Iceland - Axelsson, Gudni; Egilson, Thorsteinn; Gylfad'ottir, Sigr'idur Sif (Geothermics, 2014)
The transient temperature conditions near the bottom of well IDDP-1 in Krafla, which was drilled into a magma intrusion, have been simulated by some simple models of: (i) evolution of temperature conditions at the magma intrusion, (ii) cooling of the producing zone, a permeable layer above the intrusion, due to circulation losses during drilling and subsequent injection, (iii) reheating of the permeable layer after drilling and (iv) temperature evolution during the early phases of discharge testing in 2010. The modelling is not definitive, and does not consider later, more long-term flow testing (2011 –2012), because the necessary down-hole data are lacking. However, results indicate that the evolution of the temperature conditions can be explained by these models. If the magma was emplaced during the most recent Krafla volcanic episode 25 –35 years ago, the intrusion must have a thickness of at least 50 –100m. The effective thickness of the permeable layer is estimated to be about 45m and its equilibrium temperature to be 390 –400°C. No direct contact of the fluid with the magma is needed to explain the superheated steam discharged by the well. The situation near the bottom of the well clearly warrants further study, both through more advanced modelling and input of further data. The IDDP-1 well had to be quenched in July 2012. Whether it can maintain in the long-term the high energy output (15 –40MWe), achieved during discharge testing, depends on sufficient recharge and efficient heat-exchange, if it can be rehabilitated. Carefully executed reinjection may be the solution if long-term recharge is not sufficient.
Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma
Keywords: Geothermal; Krafla; IDDP-1; Magma intrusion; Temperature conditions; Modelling; Superheated steam

Post-rift geodynamics of the Songliao Basin, NE China: Origin and significance of T11 (Coniacian) unconformity - Song, Y.; Ren, J.; Stepashko, A.A.; Li, J. (Tectonophysics, 2014)
The T11 unconformity lies between the Qingshankou and Yaojia Formations in the post-rifting sequence of the Cretaceous Songliao Basin, NE China. It is intimately associated with petroleum reservoirs and considered to be a disconformity forming in the tectonic quiet stage. We present the interpretations from new seismic surveys and cored sections of the Cretaceous Continental Scientific Drilling borehole (CCSD-SK-1) in order to resolve the nature and origin of T11 unconformity. The T11 is often a low-angle unconformity with underlying Qingshankou Formation having been deformed and eroded prior to deposition of the Yaojia Formation. In the post-rift evolution of the basin it marks an abrupt change from a deep lake to shallow lake or subaerial environment, documented by reddening of the lacustrine mudstone, extinction of the ostracod assemblages and a great increase of coarse detrital inputs. The sharp change of depositional environment, the truncation of gentle folds and the cluster of volcanic and paleoearthquake activities, all happened simultaneously, immediately before the development of T11 unconformity, indicating a significant regional compressional uplift event in the basin. The timing of the T11 unconformity formation is within the interval 88-86.2. Ma. Correlations with coeval unconformities in other Cretaceous sedimentary basins in eastern Asia indicate that this compressional uplift coincided with an episode of global plate reorganization between the Eurasian and Paleo-Pacific plates that culminated at 88-87. Ma. During this short interval the northeast Asian margin, in eastern China, South Korea, Japan and Russian Far East experienced widespread violent volcanic and granite emplacement activity triggered by compression resulting from rapid and orthogonal slab subduction. The post-rift basin tectonic inversion occurred during T11 (Coniacian) time; thereafter the basin again evolved in an extension regime. Two subsidence phases in post-rift history took place as the direct consequence of Coniacian compression peak, which defined the distribution of oil sources and reservoirs. © 2014 Elsevier B.V.
cited By 66
Keywords: Deposition; Geodynamics; Lakes; Petroleum reservoirs; Structural geology; Tectonics; Volcanoes; Basin inversions; Northeast Asia; Post-rift; Songliao basin; Unconformity; Petroleum reservoir engineering; Coniacian; depositional environment; depositional sequence; geodynamics; lacustrine deposit; paleoenvironment; plate tectonics; rifting; sedimentary basin; tectonic reconstruction; unconformity; China; Songliao Basin; Ostracoda

Water level changes in Lake Van, Turkey, during the past ca. 600 ka: climatic, volcanic and tectonic controls - Cukur, D.; Krastel, S.; Schmincke, H.U.; Sumita, M.; Tomonaga, Y.; Namık Çağatay, M. (Journal of Paleolimnology, 2014)
Sediments of Lake Van, Turkey, preserve one of the most complete records of continental climate change in the Near East since the Middle Pleistocene. We used seismic reflection profiles to infer past changes in lake level and discuss potential causes related to changes in climate, volcanism, and regional tectonics since the formation of the lake ca. 600 ka ago. Lake Van’s water level ranged by as much as 600 m during the past 600 ka. Five major lowstands occurred, at 600, 365 –340, 290 –230, 150 –130 and 30 –14 ka. During Stage A, between about 600 and 230 ka, lake level changed dramatically, by hundreds of meters, but phases of low and high stands were separated by long time intervals. Changes in the lake level were more frequent during the past 230 ka, but less dramatic, on the order of a few tens of meters. We identified period B1 as a time of stepwise transgressions between 230 and 150 ka, followed by a short regression between ca. 150 and 130 ka. Lake level rose stepwise during period B2, until 30 ka. During the past 30 ka, a regression and a final transgression occurred, each lasting about 15 ka. The major lowstand periods in Lake Van occurred during glacial periods, suggesting climatic control on water level changes (i.e. greatly reduced precipitation led to lower lake levels). Although climate forcing was the dominant cause for dramatic water level changes in Lake Van, volcanic and tectonic forcing factors may have contributed as well. For instance, the number of distinct tephra layers, some several meters thick, increases dramatically in the uppermost 100 m of the sediment record (i.e. the past 230 ka), an interval that coincides largely with low-magnitude lake level fluctuations. Tectonic activity, highlighted by extensional and/or compressional faults across the basin margins, probably also affected the lake level of Lake Van in the past. © 2014, Springer Science+Business Media Dordrecht.
cited By 32

Preparation for drilling well IDDP-2 at Reykjanes - Friðleifsson, G.Ó.; Sigurdsson, O.; Þorbj{ornsson, D.; Karlsd'ottir, R.; G'islason, Þ.; Albertsson, A.; Elders, W.A. (Geothermics, 2014)
Preparation has begun for drilling the second deep IDDP well into the saline Reykjanes high-temperature field in SW-Iceland. The site selection for the IDDP-2 drillhole is under review and the prime candidate is essentially the same as the 1st priority site suggested for the Reykjanes field in 2003. More recent drillhole data and new MT surveys have amplified the justification for selecting that site. Deep drilling to 4 –5km depth is an important part of the HS Orka exploration strategy for enhanced power production, either by direct use of high energy steam, or by attempting to enhance the field performance by re-injecting geothermal fluid deep into very hot rocks. Pending on several decisions and development in Iceland, outside the control of the IDDP energy consortium, the IDDP-2 well might possibly be drilled to 4 –5km depth as early as 2014.
Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma
Keywords: Supercritical fluids; Iceland Deep Drilling Project; IDDP-2 well at Reykjanes; Black smoker analog

Stratigraphy and otolith microchemistry of the naked carp Gymnocypris przewalskii (Kessler) and their indication for water level of Lake Qinghai during the Ming Dynasty of China - Wang, Yujiao; Jin, Zhangdong; Zhou, Ling; Li, Fuchun; Zhang, Fei; Chen, Liumei; Qiu, XinNing; Qi, RuGui (Science China Earth Sciences, 2014)
Otoliths are biogenic carbonate minerals in the inner ear of teleost fish, whose compositions can record the physical and chemical conditions of the ambient water environment inhabited by individual fish. In this research, the fishbones and otoliths of naked carp sampled near the Bird Island, offshore Lake Qinghai, were dated and analyzed for mineralogy and microchemical compositions. Comparing the microchemical compositions of ancient otoliths with those of modern otoliths, we conclude that the ancient naked carps inhabited a relict lake formed when the lake shrank from a high lake level, by combining with the AMS-14C ages of fishbones and otoliths, the stratigraphy and surrounding topography of the sample site. AMS-14C dating results of ancient fishbones and otoliths show that these naked carps lived from 680 to 300 years ago, i.e. during the Ming Dynasty of China. The X-ray diffraction (XRD) patterns demonstrate that the ancient lapillus is composed of pure aragonite, identical to modern one, indicating that the mineral of lapillus didn’t change after a long time burial and that the ancient lapillus is suitable for comparative analysis thereafter. Microchemical results show that both ratios of Mg/Ca ((70.12±18.50)×10−5) and δ18O ((1.76±1.03)‰) of ancient lapilli are significantly higher than those of modern lapilli (average Mg/Ca=(3.11±0.41)× 10−5 and δ18O=(−4.82±0.96)‰). This reflects that the relict water body in which the ancient naked carp lived during the Ming Dynasty was characterized by higher Mg/Ca and δ18O ratios than modern Lake Qinghai, resulting from strong evaporation after being isolated from the main lake, similar to today’s Lake Gahai. Based upon the stratigraphy and altitude of naked carp remains, it can be inferred that the altitude of lake level of Lake Qinghai reached at least 3202 m with a lake area of 4480 km2 during the Ming Dynasty, approximately ∼5% larger than it is today. © 2014, Science China Press and Springer-Verlag Berlin Heidelberg.
Keywords: Carbonate minerals; Fish; Offshore oil well production; Stratigraphy; Topography; Water levels; Fishbone; Lake levels; Lake Qinghai naked carps; lapillus; Oxygen isotopes; Lakes

Yellowstone hotspot-continental lithosphere interaction - Jean, M.M.; Hanan, B.B.; Shervais, J.W. (Earth and Planetary Science Letters, 2014)
The Snake River Plain represents 17 m.y. of volcanic activity that took place as the North American continent migrated over a relatively fixed magma source, or hotspot. We present new Pb, Sr, and Nd data for a suite of 25 basalts collected from Western and Central Snake River Plain (SRP). The new isotope data, combined with previously published data from the SRP, provide a traverse of the Wyoming craton margin, from the 87Sr/86Sr = 0.706 line boundary of western SRP with Phanerozoic accreted terranes, east through the central and eastern SRP, to the Yellowstone Plateau. Low-K basalts from the western SRP, overlain by high-K basalts, provide a temporal record of regional source variation from 16.8 to 0.2 Ma. Principal Component Analysis (PCA) of the new and previously published SRP basalt Pb isotopes reveals that >97% of the total variability is accounted for by mixing between three end-members and is consistent with a sublithospheric Yellowstone hotspot mantle source with a radiogenic isotope composition similar to the mantle source of the early Columbia River Basalt Group (CRBG) and two continental lithosphere end-members, heterogeneous in age and composition. We use the SRP Pb, Sr, and Nd isotope data to model the Yellowstone Hotspot-continental lithosphere interaction by three component mixing between two continental lithospheric components, Archean lithosphere (CL1) that represents older lithosphere underlying the Yellowstone Plateau in the east, and Paleoproterozoic lithosphere (CL2) representing the younger lithosphere underlying the SRP in the west near the craton margin, and a sublithospheric end-member, representing the Yellowstone hotspot (PL). The results suggest a continuous flow of PL material westward as the NA continental lithosphere migrated over the upwelling hotspot along a shoaling gradient in the sub-continental mantle lithosphere. The model shows a decrease in Total Lithosphere end-members (CL1 + CL2) and the Lithosphere Ratio (CL1/CL2), from the craton interior at Yellowstone toward its western margin, consistent with geologic and geophysical evidence that the continental lithosphere beneath the SRP decreases in age and thickness from east to west. The Lithosphere Ratio shows step-like decreases from Yellowstone in the east to the 87Sr/86Sr = 0.706 line in the west, indicating that the SRP cuts across geochemically distinct parcels of lithospheric mantle, consistent with terrane accretion models for the craton margin. In the western SRP, young high-K basalts have a lower mass fraction of Total Lithospheric compared to the underlying low-K tholeiites, but the same Lithosphere Ratio, consistent with a recent (700-900 ka) decrease in lithosphere contribution between eruption of early low- and younger high-K basalts. © 2013 Elsevier B.V.
cited By 24
Keywords: Columbia river basalts; Continental lithosphere; Geophysical evidence; Plume dynamics; Snake river plains; Total variabilities; Volcanic activities; Yellowstones; Basalt; Isotopes; Lead; Lithology; Mixing; Principal component analysis; Rivers; Strontium; alkali basalt; continental lithosphere; craton; hot spot; igneous geochemistry; isotopic analysis; isotopic composition; lead isotope; neodymium isotope; plume; strontium isotope; terrane; tholeiitic basalt; Idaho; Snake River Plain; United States; Wyoming; Yellowstone Volcanic Plateau

Well design for the Iceland Deep Drilling Project (IDDP) - Th'orhallsson, S.; P'alsson, B.; H'olmgeirsson, S.; Ingason, K.; Matth'iasson, M.; B'oasson, H.'A.; Sverrisson, H. (Geothermics, 2014)
The aim of the Iceland Deep Drilling Projects (IDDP) was to drill to a depth of 4 –5km in known high-temperature areas to investigate their roots. The paper describes the design of the “generic” IDDP well and what the plans were. The challenges are to drill a large well with five cemented casing strings to 4500m into a reservoir which can have a temperature of 400 –600°C. In 2009 well IDDP-1 was drilled according to these plans but could not reach below 2100m due to the intersection of magma, as will be described in other papers in this special issue of Geothermics. The paper is thus for the historical record of the original design premises and intentions.
Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma
Keywords: Iceland Deep Drilling; Well design; Supercritical steam

Water salinity and productivity recorded by ostracod assemblages and their carbon isotopes since the early Holocene at Lake Qinghai on the northeastern Qinghai-Tibet Plateau, China - Li, Xiangzhong; Liu, Weiguo (Palaeogeography, Palaeoclimatology, Palaeoecology, 2014)
Lake Qinghai, the largest saline lake in China, is a closed-basin lake with a salinity of 16. g/L and is situated in the sensitive semi-arid zone between the Asian monsoon-controlled area and the westerly jet stream-influenced area. With the support of the International Continental Drilling Program (ICDP), Lake Qinghai was drilled in 2005 using the ICDP GLAD800 drilling system. Two ostracod species, i.e., Limnocythere inopinata and Eucypris mareotica, were found only in the upper 5.15. m of the drilled core 1F, covering 12. ka, where the depths of 5.15 to 3.15. m (12.0-7.4. ka) are dominated by E. mareotica and the depths of 3.15 to 0. m (7.4. ka-present) are dominated by L. inopinata.The presence of the ostracod Eucypris mareotica was related to the high salinity of the water (exceeding 30g/L), and the dominant species of ostracod (Limnocythere inopinata) was related to the brackish water (3-16g/L) in the Lake Qinghai area (Li et al., 2010). The changes in the carbon isotope in the modern ostracod shells were related to the water salinity and productivity on the lake bottom in Lake Qinghai (Li et al., 2012). On this basis, this study evaluated the changes in lake salinity and productivity and their relation to climatic change using changes in the relative abundances of ostracod fossil species assemblages and the stable carbon isotope in ostracod shells from core 1F and other published data (e.g., total organic carbon content, δ13CTOC and ice core δ18O).The single occurrence of ostracod Eucypris mareotica and the highest average δ13C values (-0.2‰) in their shells indicated that the lake salinity and productivity were very high, a phenomenon that was related to the high temperature and low lake level (caused by intense evaporation even though the precipitation increased sharply) in the early Holocene. The deceased abundance of ostracod E. mareotica and the lowest average δ13C values (-2.0‰) in ostracod shells showed that the lake salinity and productivity decreased because of the increased lake level and decreased temperatures in the middle Holocene. Finally, the lake level decreased, but the water salinity and the lake productivity gradually increased because of the high E/I ratio related to the increased temperature in the late Holocene. © 2014 Elsevier B.V.
Keywords: China; Qinghai; Qinghai Lake; Qinghai-Xizang Plateau; brackish water; carbon isotope; climate variation; drilling; fossil assemblage; Holocene; jet stream; lake level; monsoon; ostracod; primary production; saline lake; salinity; semiarid region; temperature effect; westerly

Volcanic ash layers in Lake El'gygytgyn: eight new regionally significant chronostratigraphic markers for western Beringia - Bogaard, C.; Jensen, B. J. L.; Pearce, N. J. G.; Froese, D. G.; Portnyagin, M. V.; Ponomareva, V. V.; Wennrich, V. (Climate of the Past, 2014)
Ash layers from explosive volcanic eruptions (i.e., tephra) represent isochronous surfaces independent from the environment in which they are deposited and the distance from their source. In comparison to eastern Beringia (nonglaciated Yukon and Alaska), few Plio-Pleistocene distal tephra are known from western Beringia (non-glaciated arctic and subarctic eastern Russia), hindering the dating and correlation of sediments beyond the limit of radiocarbon and luminescence methods. The identification of eight visible tephra layers (T0-T7) in sediment cores extracted from Lake El'gygytgyn, in the Far East Russian Arctic, indicates the feasibility of developing a tephrostratigraphic framework for this region. These tephra range in age from ca 45 ky to 2.2My old, and each is described and characterized by its major-, minor-, trace-element and Pb isotope composition. These data show that subduction-zone-related volcanism from the Kurile-Kamchatka-Aleutian Arc and Alaska Peninsula is the most likely source, with Pb isotope data indicating a Kamchatkan volcanic source for tephra layers T0-T5 and T7, while a source in the Aleutian Arc is possible for tephra T6. The location of Lake El'gygytgyn relative to potential source volcanoes (>1000 km) suggests these tephra are regionally distributed over a large area. These deposits provide a unique opportunity to correlate the highresolution paleoenvironmental records of Lake El'gygytgyn to other terrestrial paleoenvironmental archives from western Beringia and marine records from the western North Pacific and Bering Sea, and to move towards the development of a robust integrated framework between the continuous paleoclimatic records of Lake El'gygytgyn and other terrestrial and marine records in NE Eurasia. © Author(s) 2014.
cited By 11
Keywords: Beringia; chronostratigraphy; core analysis; explosive volcanism; lead isotope; luminescence; paleoclimate; paleoenvironment; Pleistocene; Pliocene; tephra; tephrochronology; volcanic ash; volcanic eruption; Alaska; Aleutian Islands; Arctic; Bering Sea; Canada; Chukchi; Elgygytgyn Lake; Kamchatka; Kuril Islands; Pacific Ocean; Pacific Ocean (Northwest); Russian Far East; Russian Federation; Sakhalin; United States; Yukon Territory

Utilization of the chloride bearing, superheated steam from IDDP-1 - Hjartarson, Steind'or; Sævarsd'ottir, Guðr'un; Ingason, Kristinn; P'alsson, Bjarni; Harvey, William S.; P'alsson, Halld'or (Geothermics, 2014)
When a dry steam containing volatile chloride cools to saturation temperature, the compound dissolves in the condensate and forms hydrochloric acid. This can have tremendous consequences for equipment as hydrochloric acid aggressively attacks steel and other metals, causing severe pitting corrosion, crystalline corrosion and stress corrosion cracking of stainless steel components. The Icelandic Deep Drilling Project is dealing with extreme circumstances with high enthalpy, superheated steam possibly containing hydrogen chloride. Successful corrosion mitigation is essential for the feasibility of the development. The goal of this work is to examine different technologies to utilize such a steam, with regard to exergy conservation.
Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma
Keywords: IDDP; Volatile chloride; Corrosion mitigation; Superheated geothermal steam

Travertine precipitation in the Paleoproterozoic Kuetsj{arvi Sedimentary Formation, Pechenga Greenstone Belt, NE Fennoscandian Shield - Salminen, PE; Brasier, AT; Karhu, JA; Melezhik, VA (Precambrian Research, 2014)

The SCOPSCO drilling project recovers more than 1.2 million years of history from Lake Ohrid - Wagner, B.; Wilke, T.; Krastel, S.; Zanchetta, G.; Sulpizio, R.; Reicherter, K.; Leng, M.J.; Grazhdani, A.; Trajanovski, S.; Francke, A.; Lindhorst, K.; Levkov, Z.; et al. (Scientific Drilling, 2014)
The Scientific Collaboration on Past Speciation Conditions in Lake Ohrid (SCOPSCO) project is an international research initiative to study the influence of major geological and environmental events on the biological evolution of lake taxa. SCOPSCO drilling campaigns were carried out in 2011 and 2013. In 2011 we used gravity and piston coring at one of the five proposed drill sites, and in 2013 we undertook deep drilling with the Deep Lake Drilling System (DLDS) of Drilling, Observation and Sampling of the Earth's Continental Crust (DOSECC). In April and May 2013, a total of 2100m sediments were recovered from four drill sites with water depths ranging from 125 to 260 m. The maximum drill depth was 569m below the lake floor in the centre of the lake. By retrieving overlapping sediment sequences, 95% of the sediment succession was recovered. Initial data from borehole logging, core logging and geochemical measurements indicate that the sediment succession covers > 1.2 million years (Ma) in a quasi-continuous sequence. These early findings suggest that the record from Lake Ohrid will substantially improve the knowledge of long-term environmental change and short-term geological events in the northeastern Mediterranean region, which forms the basis for improving understanding of the influence of major geological and environmental events on the biological evolution of endemic species. © Author(s) 2014.

The effects of solar irradiation changes on the migration of the Congo Air Boundary and water levels of paleo-Lake Suguta, Northern Kenya Rift, during the African Humid Period (15-5ka BP) - Junginger, Annett; Roller, Sybille; Olaka, Lydia A.; Trauth, Martin H. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2014)
The water-level record from the 300. m deep paleo-lake Suguta (Northern Kenya Rift) during the African Humid Period (AHP, 15-5. ka BP) helps to explain decadal to centennial intensity variations in the West African Monsoon (WAM) and the Indian Summer Monsoon (ISM). This water-level record was derived from three different sources: (1) grain size variations in radiocarbon dated and reservoir corrected lacustrine sediments, (2) the altitudes and ages of paleo-shorelines within the basin, and (3) the results of hydro-balance modeling, providing important insights into the character of water level variations (abrupt or gradual) in the amplifier paleo-Lake Suguta. The results of these comprehensive analyses suggest that the AHP highstand in the Suguta Valley was the direct consequence of a northeastwards shift in the Congo Air Boundary (CAB), which was in turn caused by an enhanced atmospheric pressure gradient between East Africa and India during a northern hemisphere insolation maximum. Rapidly decreasing water levels of up to 90. m over less than a hundred years are best explained by changes in solar irradiation either reducing the East African-Indian atmospheric pressure gradient and preventing the CAB from reaching the study area, or reducing the overall humidity in the atmosphere, or a combination of both these effects. In contrast, although not well documented in our record we hypothesize a gradual end of the AHP despite an abrupt change in the source of precipitation when a decreasing pressure gradient between Asia and Africa prevented the CAB from reaching the Suguta Valley. The abruptness was probably buffered by a contemporaneous change in precession producing an insolation maximum at the equator during October. Whether or not this is the case, the water-level record from the Suguta Valley demonstrates the importance of both orbitally-controlled insolation variations and short-term changes in solar irradiation as factors affecting the significant water level variations in East African rift lakes. © 2013 Elsevier B.V.
Keywords: Atlantic Ocean; Congo Margin; Kenya; Rift Valley; Suguta Valley; Congo; East African Rift; Kenya; Kenya Rift; Rift Valley; Suguta Valley; atmospheric pressure; irradiation; migration determinant; paleoatmosphere; paleolimnology; pressure gradient; radiocarbon dating; shoreline; solar radiation; water level; atmospheric pressure; grain size; highstand; insolation; irradiation; monsoon; Northern Hemisphere; pressure gradient; rift zone; summer; water level

The concept of the Iceland deep drilling project - Friðleifsson, G.Ó.; Elders, W.A.; Albertsson, A. (Geothermics, 2014)
Calculations discussed in the Iceland Deep Drilling Project feasibility study in 2003 indicated that, for same volumetric flow rate of steam, a geothermal well producing from natural supercritical fluid would have the potential to generate power outputs an order of magnitude greater than from conventional high-temperature wells (240 –340°C). To reach supercritical hydrous fluid conditions in natural geothermal systems requires deep drilling to a minimum depth of some 3.5 –5km were temperature conditions can be expected to range between 400 and 600°C in reasonably active high-temperature fields. Three geothermal fields in Iceland, Reykjanes, Hengill and Krafla, were selected as suitable locations for deep drilling to test this concept in search of natural supercritical geothermal fluid systems.
Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma
Keywords: Iceland Deep Drilling Project; Supercritical geothermal fluid systems

The Bow City structure, southern Alberta, Canada: The deep roots of a complex impact structure? - Glombick, P.; Xie, W.; Bown, T.; Hathway, B.; Banks, C. (Meteoritics and Planetary Science, 2014)
Geological and geophysical evidence is presented for a newly discovered, probable remnant complex impact structure. The structure, located near Bow City, southern Alberta, has no obvious morphological expression at surface. The geometry of the structure in the shallow subsurface, mapped using downhole geophysical well logs, is a semicircular structural depression approximately 8 km in diameter with a semicircular uplifted central region. Detailed subsurface mapping revealed evidence of localized duplication of stratigraphic section in the central uplift area and omission of strata within the surrounding annular region. Field mapping of outcrop confirmed an inlier of older rocks present within the center of the structure. Evidence of deformation along the eastern margin of the central uplift includes thrust faulting, folding, and steeply dipping bedding. Normal faults were mapped along the northern margin of the annular region. Isopach maps reveal that structural thickening and thinning were accommodated primarily within the Belly River Group. Evidence from legacy 2-D seismic data is consistent with the subsurface mapping and reveals additional insight into the geometry of the structure, including a series of listric normal faults in the annular region and complex faulting within the central uplift. The absence of any ejecta blanket, breccia, suevite, or melt sheet (based on available data) is consistent with the Bow City structure being the remnant of a deeply eroded, complex impact structure. Accordingly, the Bow City structure may provide rare access and insight into zones of deformation remaining beneath an excavated transient crater in stratified siliciclastic target rocks. © The Meteoritical Society, 2014.
cited By 5

The 2011 expedition to the El'gygytgyn impact structure, Northeast Russia: Toward a new geological map for the crater area - Raschke, U.; Zaag, P.T.; Schmitt, R.T.; Reimold, W.U. (Meteoritics and Planetary Science, 2014)
El'gygytgyn is a 3.6 Ma, 18 km diameter, impact crater formed in an approximately 88 Ma old volcanic target in Northeast Siberia. The structure has been the subject of a recent ICDP drilling project. In parallel to those efforts, a Russian-German expedition was undertaken in summer 2011 to investigate the permafrost soil, lake terraces, and the volcanic rocks of the southern and eastern crater rim. This provided the unique opportunity for mapping and sampling of the volcanic target rocks around a large part of this complex impact structure. Samples from 43 outcrops were collected and analyzed petrographically and geochemically. The results were combined with earlier mapping outcomes to create a new geological map of this impact structure and its immediate environs, at the scale of 1:50,000. Compositions of our rock suites are compared with the lithologies of the 2009 ICDP drill core. The ignimbrite described as lower bedrock in the ICDP drill core shows petrographically and chemically strong similarities to the rhyolitic and rhyodacitic ignimbrites observed on surface. The suevite sequence exposed in the ICDP drill core is a mixture of all observed target rocks at their respective proportions in the area. In contrast to previous studies, the calculated average target composition of El'gygytgyn takes the contribution of the basic target rocks into consideration: mafic and intermediate rocks approximately 7.5%, and felsic rocks approximately 92.5%. © The Meteoritical Society, 2014.
cited By 6

Surirella subrotunda sp. nov. and Surirella parahelvetica sp. nov., two new diatom (Bacillariophyta) species from Lake Prespa, Macedonia - Cvetkoska, Aleksandra; Levkov, Zlatko; Hamilton, Paul B. (Phytotaxa, 2014)
The genus Surirella is highly diverse and many taxa are reported as endemic, especially from ancient lakes and tropical continental regions. In ancient Lake Ohrid, 25 different Surirella species have been identified by different authors, five are considered to be endemic for the lake. In contrast, research on its sister Lake Prespa has been less rigorous and data for recent and fossil species of Surirella is very sparse. The number of Surirella taxa reported from Lake Prespa is 11; only one is considered an endemic for both lakes, Ohrid and Prespa. In this study, taxa from the genus Surirella were observed in a number of recent and fossil samples from Lake Prespa. Two taxa possess unique characters that distinguish them from known species. Their formal descriptions, based on detailed LM and SEM observations, are presented here. Surirella subrotunda sp. nov. is differentiated from other similar species by its valve outline, size, and shape of median area; it has been observed only in fossil diatom samples from core Co1215 recovered from Lake Prespa. Surirella parahelvetica sp. nov. is distinguished by its size, valve outline, number of alar canals and stria density. © 2014 Magnolia Press.

Joint Inversion of Body-Wave Arrival Times and Surface-Wave Dispersion for Three-Dimensional Seismic Structure Around SAFOD - Zhang, H.; Maceira, M.; Roux, P.; Thurber, C. (Pure and Applied Geophysics, 2014)
We incorporate body-wave arrival time and surface-wave dispersion data into a joint inversion for three-dimensional P-wave and S-wave velocity structure of the crust surrounding the site of the San Andreas Fault Observatory at Depth. The contributions of the two data types to the inversion are controlled by the relative weighting of the respective equations. We find that the trade-off between fitting the two data types, controlled by the weighting, defines a clear optimal solution. Varying the weighting away from the optimal point leads to sharp increases in misfit for one data type with only modest reduction in misfit for the other data type. All the acceptable solutions yield structures with similar primary features, but the smaller-scale features change substantially. When there is a lower relative weight on the surface-wave data, it appears that the solution over-fits the body-wave data, leading to a relatively rough Vs model, whereas for the optimal weighting, we obtain a relatively smooth model that is able to fit both the body-wave and surface-wave observations adequately. © 2014, Springer Basel.
cited By 35
Keywords: Economic and social effects; Seismic waves; Shear waves; Strike-slip faults; Surface waves; Wave propagation; Optimal solutions; Optimal weighting; Relative weights; S-wave velocity structure; San Andreas fault; Seismic structure; Surface wave data; Surface wave dispersion; Dispersion (waves); arrival time; body wave; inverse problem; P-wave; S-wave; San Andreas Fault; surface wave; three-dimensional modeling; velocity structure; wave dispersion

Stratigraphy, alteration mineralogy, permeability and temperature conditions of well IDDP-1, Krafla, NE-Iceland - Mortensen, A.K.; Egilson, Þ.; Gautason, B.; 'Arnad'ottir, S.; Guðmundsson, 'A. (Geothermics, 2014)
The stratigraphy, alteration mineralogy and temperature conditions in well IDDP-1 were established through drill cutting analyses and geophysical logs. The stratigraphy comprises basaltic lava and hyaloclastite sequences extending to 1362m succeeded by an intrusive complex. Intrusions comprise basaltic dykes, dolerites and below 2020m, granophyre and felsites. Rhyolitic magma was intersected below 2100m. Alteration reflects cooling in the upper ∼1500m of the reservoir. Below 1600m temperature follows the boiling-point-depth curve. Alteration minerals are scarce in vicinity to the feed zone at 2035 –2080m correlating with a superheated steam zone above the magma, but estimated bottom-hole temperature is ∼500°C.
Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma
Keywords: IDDP-1; Krafla; Alteration; Magma; Superheated conditions

Sources of core and intact branched tetraether membrane lipids in the lacustrine environment: Anatomy of Lake Challa and its catchment, equatorial East Africa - Buckles, Laura K.; Weijers, Johan W.H.; Verschuren, Dirk; Sinninghe Damst'e, Jaap S. (Geochimica et Cosmochimica Acta, 2014)
The MBT/CBT palaeotemperature proxy uses the distribution of branched glycerol dialkyl glycerol tetraethers (brGDGTs), membrane lipids that are supposed to derive from soil bacteria, to reconstruct mean annual air temperature (MAAT). Applied successfully in coastal marine sediments, its extension to lake-sediment records with potentially high time resolution would greatly expand its utility. Over the last years, however, studies have indicated the presence of additional sources of brGDGTs within lake systems. To constrain the factors influencing the MBT/CBT palaeotemperature proxy in lakes, detailed investigation of brGDGT fluxes in a modern lake system is necessary to identify their potential sources. This study concentrates on Lake Challa, a permanently stratified crater lake in equatorial East Africa with limited catchment area. An almost 3-year time series of approximately monthly samples of settling particles, supplemented with a depth profile of suspended particulate matter (SPM) and sets of profundal surface-sediment and catchment soil samples, were analysed for both the 'living' intact polar lipids (IPLs) and 'fossil' core lipids (CLs) of GDGTs. We found that brGDGTs are produced in oxic, suboxic and anoxic zones of the water column, and in substantial amounts compared to influxes from catchment soils. Additional in situ production within the lake sediments is most probable, but cannot be definitely confirmed at this time. These lacustrine brGDGTs display a different response to temperature variation than soil-derived brGDGTs, signifying either a different physiological adaptation to changing conditions within the water column and/or a different composition of the respective bacterial communities. Using this specific relationship with temperature, a local calibration based on brGDGT distributions in SPM generates relatively accurate water temperature estimates from settling particles but fails for surface sediments. © 2014 Elsevier Ltd.
Keywords: Kilimanjaro [Tanzania]; Lake Challa; Tanzania; Bacteria (microorganisms); core analysis; lacustrine deposit; lacustrine environment; lipid; membrane; microbial community; paleotemperature; soil biota; suspended particulate matter; water temperature

Probing reservoir-triggered earthquakes in Koyna, India, through scientific deep drilling - Gupta, H.; Nayak, S.; Rao, Y.J.B.; Rajan, S.; Bansal, B.K.; Purnachandra Rao, N.; Roy, S.; Arora, K.; Mohan, R.; Tiwari, V.M.; Satyanarayana, H.V.S.; Patro, P.K.; et al. (Scientific Drilling, 2014)
We report here the salient features of the recently concluded International Continental Scientific Drilling Program (ICDP) workshop in Koyna, India. This workshop was a sequel to the earlier held ICDP workshop in Hyderabad and Koyna in 2011. A total of 49 experts (37 from India and 12 from 8 other countries) spent 3 days reviewing the work carried out during the last 3 years based on the recommendations of the 2011 workshop and suggesting the future course of action, including detailed planning for a full deep drilling proposal in Koyna, India. It was unanimously concluded that Koyna is one of the best sites anywhere in the world to investigate genesis of triggered earthquakes from near-field observations. A broad framework of the activities for the next phase leading to deep drilling has been worked out.
cited By 9
Keywords: Drilling; Energy resources; Continental scientific drillings; Course of action; Deep drilling; Detailed planning; Near fields; Salient features; Scientific deep-drilling; Triggered Earthquakes; Earthquakes

Rock-magnetic signature of precipitation and extreme runoff events in south-eastern Patagonia since 51,200calBP from the sediments of Laguna Potrok Aike - Lis'e-Pronovost, A.; St-Onge, G.; Gogorza, C.; Jouve, G.; Francus, P.; Zolitschka, B. (Quaternary Science Reviews, 2014)
A 106-m long sediment sequence from the maar lake Laguna Potrok Aike in southern Patagonia was recovered in the framework of the International Continental Scientific Drilling Program (ICDP) Potrok Aike maar lake Sediment Archive Drilling prOject (PASADO). About half of the sedimentary sequence is composed of mass movement deposits (MMDs) and the event-corrected record reaches back to 51,200calBP. Here we present a high-resolution rock-magnetic study revealing two sedimentary facies associated with MMDs and characterized by two different types of spurious gyroremanent magnetization (GRM) acquired during static alternating field demagnetization. The first rock-magnetic signature is detected in MMDs composed of reworked sand and tephra material. The signature consists of GRM acquired during demagnetization of the natural remanent magnetization (NRM) and other rock-magnetic properties typical of iron sulfides such as greigite. We interpret these intervals as authigenic formation of iron sulfides in suboxic conditions within the MMD. The second rock-magnetic signature consists of a series of 10 short intervals located on the top of MMDs characterized by GRM acquisition during demagnetization of the isothermal remanent magnetization (IRM). Based on geological, limnological, stratigraphic and climatic evidence these layers are interpreted as reflecting pedogenic hematite and/or goethite brought to the lake by runoff events related to precipitation and permafrost melt. The pedogenic iron minerals mobilized from the catchment most likely settled out of suspension on top of MMDs after a rapid remobilization event. The series of runoff events corresponds to periods of increased lacustrine productivity in Laguna Potrok Aike and are coeval within the limit of the chronology to warm periods of the Last Glacial as recorded in Antarctica, the deglaciation in the mid-latitudes of the Southern Hemisphere and enhanced precipitation during the Early Holocene in southeastern Patagonia. © 2014 Elsevier Ltd.
Keywords: Argentina; Laguna Potrok Aike; Patagonia; Santa Cruz [Argentina]; Catchments; Demagnetization; Deposits; Geomagnetism; Iron; Lakes; Magnetization; Runoff; Sedimentology; Sediments; Stratigraphy; Lacustrine sediments; Laguna potrok aike; Mass movement; Paleo-environment; Rock magnetism; facies; geochronology; hematite; isotherm; lacustrine deposit; last glaciation; magnetization; paleoenvironment; precipitation (climatology); runoff; sedimentary sequence; sulfide; Sedimentary rocks

Quaternary forest associations in lowland tropical West Africa - Miller, Charlotte S.; Gosling, William D. (Quaternary Science Reviews, 2014)
Terrestrial fossil pollen records are frequently used to reveal the response of vegetation to changes in both regional and global climate. Here we present a fossil pollen record from sediment cores extracted from Lake Bosumtwi (West Africa). This record covers the last c. 520 thousand years (ka) and represents the longest terrestrial pollen record from Africa published to date. The fossil pollen assemblages reveal dynamic vegetation change which can be broadly characterized as indicative of shifts between savannah and forest. Savannah formations are heavily dominated by grass (Poaceae) pollen (>55%) typically associated with Cyperaceae, Chenopodiaceae-Amaranthaceae and Caryophyllaceae. Forest formations are palynologically more diverse than the savannah, with the key taxa occurring in multiple forest zones being Moraceae, Celtis, Uapaca, Macaranga and Trema. The fossil pollen data indicate that over the last c. 520ka the vegetation of lowland tropical West Africa has mainly been savannah; however six periods of forest expansion are evident which most likely correspond to global interglacial periods. A comparison of the forest assemblage composition within each interglacial suggests that the Holocene (11-0ka) forest occurred under the wettest climate, while the forest which occurred at the time of Marine Isotope Stage 7 probably occurred under the driest climate. © 2013 The Authors.
Keywords: Forestry; Isotopes; Lakes; Plants; Pollen; Ashanti; Georgia; Ghana; Lake Bosumtwi; Savannah; United States; West Africa; Amaranthaceae; Caryophyllaceae; Celtis; Cyperaceae; Macaranga; Moraceae; Poaceae; Trema; Uapaca; Isotopes; Lakes; Vegetation; Assemblage composition; Ghana; Interglacial periods; Marine Isotope Stage 7; Pollen; Quaternary; Terrestrial pollen records; West Africa; forest; fossil record; global climate; Holocene; interglacial; marine isotope stage; pollen; Quaternary; savanna; vegetation; Forestry

Recent anthropogenic impact in ancient Lake Ohrid (Macedonia/Albania): a palaeolimnological approach - Lorenschat, Julia; Zhang, Xiaosen; Anselmetti, Flavio S.; Reed, Jane M.; Wessels, Martin; Schwalb, Antje (Journal of Paleolimnology, 2014)
Ancient lakes, which are important centres of biodiversity and endemism, are threatened by a wide variety of human impacts. To assess environmental impact on ancient Lake Ohrid we have taken short sediment cores from two contrasting site locations, comprising a site of urban pollution and an apparently pristine area. Recent impacts on water quality and ecology were assessed using sediment, geochemical, ostracode, and diatom data derived from analysis of two 210Pb-dated sediment cores spanning the period from 1918 to 2009. According to the index of geoaccumulation, sediments were often moderately contaminated with As. Fe and Ni concentrations often exceeded reported maximum limits above which harmful effects on sediment-dwelling organisms are expected. Productivity in the (pristine) south-eastern part of Lake Ohrid (Sveti Naum) is generally lower than in the north, probably due to the strong influence of spring discharge. Low ostracode and diatom concentrations, low abundance of the epilimnetic diatom Cyclotellaocellata, and low values of TOC and TIC indicate a lower productivity from the early 1920s to the late 1980s. Since the mid 1970s, increased relative abundance of C. ocellata and increasing diatom concentration indicate increasing productivity in the south-eastern part. Rising numbers of ostracode valves and higher TIC and TOC contents in both sediment cores indicate an increase in productivity during the late 1980s. A slight increase in productivity near Sveti Naum continued from the early 1990s until 2009, witnessed by rising TC, TIC, and TOC content and a generally high number of ostracode valves and ostracode diversity. The area near the City of Struga (site of urban pollution) is also characterized by rising TOC and TIC contents and, furthermore, by increasing Cu, Fe, Pb, and Zn concentrations since the early 1990s. The recent reduction in the number of ostracode valves and ostracode diversity is probably caused by a higher heavy metal load into the lake. This suggests that living conditions for the endemic species in Lake Ohrid have become less favourable in the northern part of the lake, which might threaten the unique flora and fauna of Lake Ohrid. © 2014, Springer Science+Business Media Dordrecht.

Resolution of non-double-couple components in the seismic moment tensor using regional networks-i: A synthetic case study - Stierle, E.; Vavryčuk, V.; Š'ilen'y, J.; Bohnhoff, M. (Geophysical Journal International, 2014)
We perform a detailed synthetic study on the resolution of non-double-couple (non-DC) components in the seismic moment tensors from short-period data observed at regional networks designed typically for monitoring aftershock sequences of large earthquakes. In addition, we test two different inversion approaches-a linear full moment tensor inversion and a nonlinear moment tensor inversion constrained to a shear-tensile source model. The inversions are applied to synthetic first-motion P- and S-wave amplitudes, which mimic seismic observations of aftershocks of the 1999 Mw = 7.4 Izmit earthquake in northwestern Turkey adopting a shear-tensile source model. To analyse the resolution capability for the obtained non-DC components inverted, we contaminate synthetic amplitudes with random noise and incorporate realistic uncertainties in the velocity model as well as in the hypocentre locations. We find that the constrained moment tensor inversion yields significantly smaller errors in the non-DC components than the full moment tensor inversion. In particular, the errors in the compensated linear vector dipole (CLVD) component are reduced if the constrained inversion is applied. Furthermore, we show that including the S-wave amplitudes in addition to P-wave amplitudes into the inversion helps to obtain reliable non-DC components. For the studied station configurations, the resolution remains limited due to the lack of stations with epicentral distances less than 15 km. Assuming realistic noise in waveform data and uncertainties in the velocity model, the errors in the non-DC components are as high as ±15 per cent for the isotropic and CLVD components, respectively, thus being non-negligible in most applications. However, the orientation of P- and T-axes is well determined even when errors in the modelling procedure are high. © The Authors 2014. Published by Oxford University Press on behalf of The Royal Astronomical Society.
cited By 55

Resolution of non-double-couple components in the seismic moment tensor using regional networks-II: Application to aftershocks of the 1999Mw 7.4 Izmit earthquake - Stierle, E.; Bohnhoff, M.; Vavryčuk, V. (Geophysical Journal International, 2014)
We study potential non-double-couple (non-DC) components in aftershocks of the 1999 Izmit earthquake. The Izmit earthquake ruptured a 140-km-long segment of the North Anatolian Fault Zone in northwestern Turkey and was followed by the Mw = 7.1 D{uzce earthquake that extended the rupture further to the east. Focal mechanisms of Izmit aftershocks clearly indicate a segmentation of the rupture into several segments, one of which is the Akyazi Plain, a pull-apart structure, where significant non-DC components might be observed. The analysed earthquake catalogue containswaveforms ofmore than 4000 accurately located events observed at 35 three-component short-period seismic stations. To ensure high-quality datawith good focal coverage, we apply strict quality criteria to the aftershock catalogue reducing the number of events to only 33 aftershocks for which stable moment tensors were calculated using P-and S-wave amplitudes. The moment tensors of the 33 analysed aftershocks display significant differences in the percentage of the non-DC components for the three distinct fault segments: the Izmit-Sapanca, Karadere-D{uzce and the Akyazi segments. Events located in the Izmit-Sapanca and Karadere-D{uzce segments exhibit only small percentages of the non-DC components and if existent they are mainly positive. This correlates well with the predominant strike-slip stress regime along these segment and also with the main shock rupture being rightlateral strike-slip. In contrary, we found a substantial percentage of non-DC components for events below the Akyazi Plain where the Sapanca Fault splits into the Mudurnu and Karadere faults. There, the observed non-DC components are entirely positive indicating a tensional regime and ranging from 20 to 48 per cent, clearly exceeding the defined error bounds found in a synthetic study. This observation is in accordance with the post-seismic setting following the Izmit main shock that left a remarkable slip deficit of 3.5 m below the Akyazi bend.
cited By 43

Road to offshore gas production test - From Mallik to Nankai Trough - Saeki, T. (Proceedings of the Annual Offshore Technology Conference, 2014)
The world's first offshore gas production test from methane hydrate deposits was conducted in March 2013, at the test site located on the margin of Daini Atsumi Knoll, off the coasts of Atsumi and Shima peninsulas, in the easten Nankai Trough, of Japan. Approximately 120, 000 cubic meters of methane gas was produced in 6 days using the depressurization technique. The test was a significant advance in Japan's national program to construct the technical base for future commertial methane hydrate resource development. A series of researches for more than 10 years, including two times of onshore production tests in Mallik field and explorations in eastern Nankai Trough, were required to reach the test. This report reviews Japan's research history for methane hydrates. Copyright © 2014, Offshore Technology Conference.
cited By 17
Keywords: Hydration; Methane; Offshore oil well production; Offshore technology; Software testing; Testing; Depressurizations; Gas production test; Methane hydrates; Nankai troughs; National program; Production test; Research history; Resource development; Gas hydrates

Rock and mineral transformations in a fault zone leading to permanent creep: Interactions between brittle and viscous mechanisms in the San Andreas Fault - Richard, J.; Gratier, J.-P.; Doan, M.-L.; Boullier, A.-M.; Renard, F. (Journal of Geophysical Research: Solid Earth, 2014)
Creep processes may relax part of the tectonic stresses in active faults, either by continuous or episodic processes. The aim of this study is to obtain a better understanding of these creep mechanisms and the manner in which they change in time and space. Results are presented from microstructural studies of natural samples collected from San Andreas Fault Observatory at Depth borehole drilled through the San Andreas Fault, which reveal the chronology of the deformation within three domain types. (i) A relatively undeformed zone of the host rock reflects the first step of the deformation process with fracturing and grain indentations showing the coupling between fracturing and pressure solution. (ii) Shear deformation development that associates fracturing and solution cleavage processes leads to profound changes in rock composition and behavior with two types of development depending on the ratio between the amount of dissolution and deposition: abundant mineral precipitation strengthens some zones while pervasive dissolution weakens some others, (iii) zones with mainly dissolution trended toward the present-day creeping zones thanks to both the passive concentration of phyllosilicates and their metamorphic transformation into soft minerals such as saponite. This study shows how interactions between brittle and viscous mechanisms lead to widespread transformation of the rocks and how a shear zone may evolve from a zone prone to earthquakes and postseismic creep to a zone of steady state creep. In parallel, the authors discuss how the creeping mechanism, mainly controlled by the very low friction of the saponite in the first 3-4 km depth, may evolve with depth. ©2014. American Geophysical Union. All Rights Reserved.
cited By 31
Keywords: active fault; brittle deformation; creep; fault zone; metamorphic rock; rock microstructure; San Andreas Fault; tectonic setting; viscosity

Roles of Meteoric Water on Secondary Porosity of Siliciclastic Reservoirs (in Chinese with English abstract) (in Chinese with English abstract); [大气淡水在碎屑岩次生孔隙中的作用] - Ding, X.; Han, M.; Zhang, S.; Fu, M.; Wan, Y. (Geological review, 2014)

Site selection for the well IDDP-1 at Krafla - Friðleifsson, G.Ó.; 'Armannsson, H.; Guðmundsson, 'A.; 'Arnason, K.; Mortensen, A.K.; P'alsson, B.; Einarsson, G.M. (Geothermics, 2014)
This paper describes the site selection for the IDDP-1 well within the Krafla volcano in 2008. In a feasibility study in 2003, 12 potential well sites within three geothermal areas were suggested and prioritized to meet the goal of finding supercritical temperatures and pressures together with high permeability. In 2006 one of these priority sites was selected within the Krafla field, but in autumn 2007 due to its proximity to the Krafla power plant a new location had to be selected only a few months before drilling. Choice of that new site was justified by new MT-resistivity survey data, seismic data and information from an earlier nearby production well, K-36.
Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma
Keywords: IDDP-1 well site at Krafla; Superheated and supercritical reservoir conditions; MT-resistivity data

Sediment colour reflectance spectroscopy as a proxy for wet/dry cycles at Lake El'gygytgyn, Far East Russia, during Marine Isotope Stages 8 to 12 - Wei, J.H.; Finkelstein, D.B.; Brigham-Grette, J.; Castañeda, I.S.; Nowaczyk, N. (Sedimentology, 2014)
Marine Isotope Stage 11 has been proposed as an analogue for the present interglacial interval; yet, terrestrial climate records from both this region and time interval are rare. The sediments deposited at Lake El'gygytgyn (67°30′N, 172°5′E) in Far East Russia contain a 3·56 Ma record of climate variability. This study presents a high-resolution record of sediment colour change from Marine Isotope Stage 8 to 12 (ca 275 to 475 ka) and demonstrates the link between lake catchment processes and climate variability. The hue colour parameter, calculated from data collected via colour reflectance spectroscopy in the visible spectrum (380 to 720 nm), exhibits correspondence with global climate records. Determining the source of sediment colour changes was achieved through detailed mineralogical and sedimentological methods, and linked to colour changes through a series of colour sensitivity tests. Mineralogical data, measured by X-ray diffraction, reveal fluctuations in concentrations of clay minerals corresponding to colour changes. Further analyses of the clay mineral assemblages show no change in relative clay mineral abundances, yet demonstrate a lake catchment dominated by physical weathering processes. Using measured mineral abundances, reconstructions of sediment colour based on colour reflectance mineral standards link mineral and clay mineral content to overall sediment colour. Colour sensitivity tests demonstrate the ability of iron oxide minerals to stain sediments red. Additionally, colour sensitivity to organic matter content was tested, suggesting that organic content drives variability in the red portion of the spectrum and darkens the overall colour signal. Sediment colour is then ultimately linked to physical weathering of bedrock minerals, with small amounts of chemical weathering producing iron oxides during wet intervals. Fluctuations in the sediment colour reveal a high-resolution record of wet/dry cycles, and provide new information about wet periods for the Russian Arctic region not yet understood from other lake proxy records. © 2014 The Authors. Sedimentology © 2014 International Association of Sedimentologists.
cited By 13
Keywords: Catchments; Climate change; Color; Digital storage; Erosion; Glacial geology; Iron oxides; Isotopes; Lakes; Oxide minerals; Rare earths; Reflection; Runoff; Sediments; Spectroscopy; Weathering; Chemical weathering; Clay mineral assemblages; Clay mineralogy; High resolution; Marine isotope stages; Organic matter content; Palaeoclimate; Reflectance spectroscopy; Clay minerals

Sedimentary evolution and environmental history of Lake Van (Turkey) over the past 600 000 years - Stockhecke, M.; Sturm, M.; Brunner, I.; Schmincke, H.-U.; Sumita, M.; Kipfer, R.; Cukur, D.; Kwiecien, O.; Anselmetti, F.S. (Sedimentology, 2014)
The lithostratigraphic framework of Lake Van, eastern Turkey, has been systematically analysed to document the sedimentary evolution and the environmental history of the lake during the past ca 600 000 years. The lithostratigraphy and chemostratigraphy of a 219 m long drill core from Lake Van serve to separate global climate oscillations from local factors caused by tectonic and volcanic activity. An age model was established based on the climatostratigraphic alignment of chemical and lithological signatures, validated by 40Ar/39Ar ages. The drilled sequence consists of ca 76% lacustrine carbonaceous clayey silt, ca 2% fluvial deposits, ca 17% volcaniclastic deposits and 5% gaps. Six lacustrine lithotypes were separated from the fluvial and event deposits, such as volcaniclastics (ca 300 layers) and graded beds (ca 375 layers), and their depositional environments are documented. These lithotypes are: (i) graded beds frequently intercalated with varved clayey silts reflecting rising lake levels during the terminations; (ii) varved clayey silts reflecting strong seasonality and an intralake oxic-anoxic boundary, for example, lake-level highstands during interglacials/interstadials; (iii) CaCO3-rich banded sediments which are representative of a lowering of the oxic-anoxic boundary, for example, lake level decreases during glacial inceptions; (iv) CaCO3-poor banded and mottled clayey silts reflecting an oxic-anoxic boundary close to the sediment-water interface, for example, lake-level lowstands during glacials/stadials; (v) diatomaceous muds were deposited during the early beginning of the lake as a fresh water system; and (vi) fluvial sands and gravels indicating the initial flooding of the lake basin. The recurrence of lithologies (i) to (iv) follows the past five glacial/interglacial cycles. A 20 m thick disturbed unit reflects an interval of major tectonic activity in Lake Van at ca 414 ka bp. Although local environmental processes such as tectonic and volcanic activity influenced sedimentation, the lithostratigraphic pattern and organic matter content clearly reflect past global climate changes, making Lake Van an outstanding terrestrial archive of unprecedented sensitivity for the reconstruction of the regional climate over the last 600 000 years. © 2014 The Authors Sedimentology © 2014 International Association of Sedimentologists.
cited By 80
Keywords: Argon; Calcium carbonate; Climate change; Deposits; Environmental protection; Glacial geology; Lakes; Lithology; Oxic sediments; Sedimentology; Silt; Tectonics; Volcanoes; Continental archive; Eastern Anatolia; Glacial/interglacial climate; ICDP project PALEOVAN; Lake sediments; Palaeoenvironmental reconstruction; Anoxic sediments

Seismic correlated Mallik 3D gas hydrate distribution: Effect of geomechanics in non-homogeneous hydrate dissociation by depressurization - Uddin, M.; Wright, F.; Dallimore, S.; Coombe, D. (Journal of Natural Gas Science and Engineering, 2014)
The delineation of the Mallik gas hydrate field has utilized extensive well logging and substantial 3D seismic testing and interpretation. This study explores the use of seismic data to quantify the areally heterogeneous gas hydrate distribution. The available Mallik 3D seismic data was compiled and compared/contrasted with available well log data from two adjacent wells. Based on the seismic information, two areally variable (i.e. non-homogeneous) scenarios for gas hydrate distributions are considered: Scenario I having the same initial total hydrate amount as our earlier model areally uniform (homogeneous) distribution, and Scenario II with significantly less overall total hydrate, but honouring the same relative distribution. The scenarios of variable gas hydrate distributions are used in dynamic simulations of the lower Mallik zone. Simulations of each were conducted with and without the role of geomechanics.In Scenario I, we observed multiple gas production peaks (which quite similar to 6 days production behaviour) with higher localized pressure pulses occurred due to strong gas hydrate heterogeneity. In Scenario II, this drastic change in gas production rate was not observed (due to faster pressure evolution in the reservoir). In both Scenarios, the overall reservoir gas production peak is delayed compared to the homogeneous case. This is further delayed by the role of geomechanics. More interestingly, all simulation cases show a very similar overall production trend. This is probably a unique for the Mallik gas hydrate production using single vertical well, including a gas production peak but terminating in a stabilized period of lower but significant gas production.With geomechanics, gas production in general and the gas production peak is shifted and delayed. The geomechanics effect is not purely compaction drive (as in conventional reservoirs, gas production increases with geomechanics). The simulations utilized two set of geomechanical parameters obtained from logs (dynamic parameters) and rocks testing (static parameters). Geomechanical responses based on dynamic parameters were essentially equivalent to simulations ignoring geomechanical effects. The geomechanics simulations indicate an essentially elastic reservoir response (i.e. no plastic failure) assuming a cased vertical well. The Mallik upper zone A and middle zone B are closer to the permafrost and nearer to plasticity limits should be explored. © 2014 .
cited By 10
Keywords: Digital storage; Dissociation; Failure (mechanical); Gas industry; Gases; Geomechanics; Geophysical prospecting; Hydration; Seismic response; Seismic waves; Well logging; Well testing; Depressurizations; Dynamic parameters; Gas-hydrate production; Hydrate dissociation; Hydrate distribution; Seismic; Seismic information; Simulation; Gas hydrates

Seismic stratigraphy of Lake Van, eastern Turkey - Cukur, D.; Krastel, S.; Schmincke, H.-U.; Sumita, M.; Çağatay, M.N.; Meydan, A.F.; Damci, E.; Stockhecke, M. (Quaternary Science Reviews, 2014)
More than 1500km of multi-channel seismic reflection profiles combined with ICDP (International Continental Scientific Drilling Program) drilling data, provide important insights into the stratigraphic evolution of Lake Van, eastern Turkey. Three major basins (Tatvan, Northern and the Deveboynu basins) comprise the main lake basin and are separated by morphological highs (Ahlat ridge and Northern ridge). Moreover, NE-SW faults, parallel to the general tectonic lineament of the area, dominate the entire basin and are in charge of creating graben and half-graben structures. Well-developed prograding deltaic sequences on top of the basement were recognized by seismic stratigraphy analysis. Most likely, they formed during the initial flooding of Lake Van 600ka. The Tatvan basin sediments are dominated by mass-flow deposits of various origins alternating with undisturbed lacustrine sediments including distinct tephra layers. Faulting along the Tatvan basin margins may have triggered margin-wide slope failures. Ahlat ridge started to form between ca340ka-290ka. Since then, Ahlat ridge was sheltered from major mass-flows due to its elevation. Hence, slow lacustrine sedimentation has prevailed throughout lake history on Ahlat ridge, which was the location of the main drill site during the ICDP. Several lake level fluctuations are evident on the eastern slope area but the deep basins were permanently covered by water. A significant lake-level low stand (ca600kaBP) was found at 610m below present lake level. The setting of the lake changed at about 30ka. Tectonic activity appears to have waned significantly as the mass-transport deposition decreased across the Tatvan basin while normal undisturbed lacustrine sedimentation prevailed. A different setting is found in the Northern basin from ca90ka to Present, especially due to the strong influx of mostly volcaniclastic turbidites causing sedimentation rates to be about 3.5 times higher (drill Site 1), than at Site 2 (Ahlat ridge). © 2014 Elsevier Ltd.
cited By 27
Keywords: Drills; Faulting; Infill drilling; Mass transfer; Sedimentation; Seismic waves; Seismology; Stratigraphy; Ahlat ridge; Lake vans; Northern basins; Seismic reflections; Tatvan basin; Lakes; delta; drilling; fault; geomorphology; lacustrine deposit; lake evolution; sedimentation; seismic reflection; seismic stratigraphy; turbidity; Lake Van; Turkey

Seismic velocity variations at TCDP are controlled by MJO driven precipitation pattern and high fluid discharge properties - Hillers, G.; Campillo, M.; Ma, K.-F. (Earth and Planetary Science Letters, 2014)
Using seismic noise based monitoring techniques we find that seismic velocity variations (dv/v) observed with the borehole array of the Taiwan Chelungpu-fault Drilling Project (TCDP) are controlled by strong precipitation events associated with the Madden-Julian Oscillation (MJO), a dynamic intraseasonal atmospheric pattern in the tropical atmosphere. High-frequency noise (>1 Hz) excited by steady anthropogenic activity in the vicinity of the TCDP allows daily resolution of dv/v time series. Relatively large fluid discharge properties control the equilibration of the ground water table and hence seismic velocities on time scales smaller than the average precipitation recurrence interval. This leads to the observed synchronous 50-80 day periodicity in dv/v and rainfall records in addition to the dominant annual component. Further evidence for the governing role of hydraulic properties is inferred from the similarity of observed dv/v timing, amplitude, and recovery properties with dv/v synthetics generated by a combined model of ground water table changes and diffusive propagation of seismic energy. The lapse time (τ) dependent increase of dv/v amplitudes is controlled by the sensitivity of the diffuse wave field sampled at 1100 m depth to shallower water level fluctuations. The significant vertical offset between stations and water level explains the direct τ dependence which is opposite to the trend previously inferred from measurements at the surface. © 2014 Elsevier B.V.
cited By 45

Seismically triggered anomalies in the isotope signatures of mantle-derived gases detected at degassing sites along two neighboring faults in NW Bohemia, central Europe - Br{auer, Karin; K{ampf, Horst; Strauch, Gerhard (Journal of Geophysical Research: Solid Earth, 2014)
The Vogtland and NW Bohemia region is known for its earthquake swarms; the most intensive swarm since 1985/86 occurred in October 2008. To find further indications for the interaction of ascending mantle-derived fluids and the occurrence of earthquake swarms, detailed fortnightly studies of gas compositions (CO2, N2, Ar, He, H2, and CH 4) and isotope ratios (δ13C, δ15N, and 3He/4He) were carried out between October 2008 and April 2011 at four locations close to the Nov'y Kostel focal zone and at the Wettinquelle spring (Bad Brambach). From the start of the 2008 earthquake swarm seismically induced isotope-geochemical anomalies were recorded at locations along the Počatky-Plesn'a fault zone (PPZ) and were, for the first time, also found at degassing locations on the Mari'ansk'e L'azn{A• fault zone (MLF). Variations were observed in both the temporal and spatial distributions of the anomalies as well in anomaly strengths, probably due to the positions of these fault zones relative to the focal zone, and to differences in fluid migration pathways. Prior to both the 2000 and 2008 swarms, 3He/4He ratios>6Ra were recorded at the Bubl'ak mofette. These anomalous pre-seismic 3He/ 4He ratios suggest that both the 2000 and 2008 swarms may have been associated with the supply of fresh magma from a less degassed reservoir in the lithospheric mantle. The temporal δ13CCO2 pattern from detailed studies at Bubl'ak between 2005 and 2011 indicates progressive magma degassing, as well as seismically induced variations in the δ13C, providing additional support to the interpretation derived from the 3He/4He ratios. Key Points Isotope anomalies detected in gases from different faults after earthquakes A pre-seismic increase in 3He/4He (> 6 Ra) indicates magma ascent from mantle Isotope monitoring is an excellent way to track active geodynamic processes ©2014. American Geophysical Union. All Rights Reserved.
Keywords: Bohemia; Czech Republic; Germany; Vogtland; carbon dioxide; carbon isotope; degassing; earthquake swarm; earthquake trigger; fault zone; geodynamics; helium isotope; igneous geochemistry; intraplate process; isotopic analysis; isotopic ratio; magmatism; nitrogen isotope; spatial distribution; temporal distribution

Structural geology of impact craters - Kenkmann, T.; Poelchau, M.H.; Wulf, G. (Journal of Structural Geology, 2014)
The formation of impact craters is a highly dynamic and complex process that subjects the impacted target rocks to numerous types of deformation mechanisms. Understanding and interpreting these styles of micro-, meso- and macroscale deformation has proved itself challenging for the field of structural geology. In this paper, we give an overview of the structural inventory found in craters of all size ranges on Earth, and look into the structures of craters on other planetary bodies. Structural features are discussed here that are caused by i) extremely high pressures and temperatures that occur during the initial passage of the shock wave through the target rock and projectile, ii) the resulting flow field in the target that excavates and ejects rock materials, and iii) the gravitationally induced modification of the crater cavity into the final crater form. A special focus is put on the effects that low-angle impacting bodies have on crater formation. We hope that this review will help both planetary scientists and structural geologists understand the deformation processes and resulting structures generated by meteorite impact. © 2014.
cited By 124

Investigating ultra high-enthalpy geothermal systems: A collaborative initiative to promote scientific opportunities - Elders, W.A.; Nielson, D.; Schiffman, P.; Schriener, Jr. (Scientific Drilling, 2014)
Scientists, engineers, and policy makers gathered at a workshop in the San Bernardino Mountains of southern California in October 2013 to discuss the science and technology involved in developing high-enthalpy geothermal fields. A typical high-enthalpy geothermal well between 2000 and 3000m deep produces a mixture of hot water and steam at 200-300 °C that can be used to generate about 5-10MWe of electric power. The theme of the workshop was to explore the feasibility and economic potential of increasing the power output of geothermal wells by an order of magnitude by drilling deeper to reach much higher pressures and temperatures. Development of higher enthalpy geothermal systems for power production has obvious advantages; specifically higher temperatures yield higher power outputs per well so that fewer wells are needed, leading to smaller environmental footprints for a given size of power plant. Plans for resource assessment and drilling in such higher enthalpy areas are already underway in Iceland, New Zealand, and Japan. There is considerable potential for similar developments in other countries that already have a large production of electricity from geothermal steam, such as Mexico, the Philippines, Indonesia, Italy, and the USA. However drilling deeper involves technical and economic challenges. One approach to mitigating the cost issue is to form a consortium of industry, government and academia to share the costs and broaden the scope of investigation. An excellent example of such collaboration is the Iceland Deep Drilling Project (IDDP), which is investigating the economic feasibility of producing electricity from supercritical geothermal reservoirs, and this approach could serve as model for future developments elsewhere. A planning committee was formed to explore creating a similar initiative in the USA.
cited By 4
Keywords: Electric power generation; Enthalpy; Geothermal energy; Geothermal wells; Well drilling; Economic challenges; Economic feasibilities; Environmental footprints; Geothermal reservoir; Iceland deep drilling projects; Resource assessments; Science and Technology; Southern California; Geothermal fields

Comparative study of geophysical and soil-gas investigations at the Hartoušov (Czech Republic) natural CO2 degassing site - Sandig, Claudia; Sauer, Uta; Br{auer, Karin; Serfling, Ulrich; Sch{utze, Claudia (Environmental Earth Sciences, 2014)
Our study at this natural analog site contributes to the evaluation of methods within a hierarchical monitoring concept suited for the control of CO2 degassing. It supports the development of an effective monitoring concept for geological CO2 storage sites-carbon capture and storage as one of the pillars of the European climate change efforts. This study presents results of comprehensive investigations along a 500-m long profile within the Hartoušov (Czech Republic) natural CO2 degassing site and gives structural information about the subsurface and interaction processes in relation to parameters measured. Measurements of CO2 concentrations and investigation of the subsurface using electrical resistivity tomography and self-potential methods provide information about subsurface properties. For their successful application it is necessary to take seasonal variations (e.g., soil moisture, temperature, meteorological conditions) into consideration due to their influence on these parameters. Locations of high CO2 concentration in shallow depths are related to positive self-potential anomalies, low soil moistures and high resistivity distributions, as well as high δ13C values and increased radon concentrations. CO2 ascends from deep geological sources via preferential pathways and accumulates in coarser sediments. Repetition of measurements (which includes the effects of seasonal variations) revealed similar trends and allows us to identify a clear, prominent zone of anomalous values. Coarser unconsolidated sedimentary layers are beneficial for the accumulation of CO2 gas. The distribution of such shallow geological structures needs to be considered as a significant environmental risk potential whenever sudden degassing of large gas volumes occurs. © 2014 Springer-Verlag Berlin Heidelberg.
Keywords: Czech Republic; Carbon; Carbon capture; Climate change; Degassing; Electric conductivity; Geology; Moisture; Risk assessment; Soil moisture; Soils; Electrical resistivity tomography; Evaluation of methods; Meteorological condition; Permeable structures; Preferential pathways; Self potential; Self-potential anomalies; Structural information; carbon dioxide; carbon sequestration; climate change; comparative study; degassing; electrical resistivity; leakage; permeability; radon; risk assessment; underground storage; Carbon dioxide

Chemical composition of sediments in Baikal deep-water boreholes as a basis for reconstructions of climatic and environmental changes - Kuz'min, M.I.; Bychinskii, V.A.; Kerber, E.V.; Oshchepkova, A.V.; Goreglyad, A.V.; Ivanov, E.V. (Russian Geology and Geophysics, 2014)
Earlier reconstructions of climatic and environmental changes from data of deep-water drilling on the Akademichesky Ridge in Lake Baikal were based both on the content of biogenic silica or the abundance of diatom valves and on the results of X-ray diffraction (XRD) analysis of the sediment mineralogy. It was established that clay minerals are the main carrier of information about climatic variations in a drainage basin. The content of biogenic silica strictly correlates with two chrystallochemical parameters: the abundance of smectite beds in illite-smectite and the abundance of illite. However, detailed analysis of clay minerals calls for exclusive XRD techniques without mass determination of minerals in the sediments of long Baikal cores. We propose a new approach to determine the mineral composition of bottom sediments, based on their chemical composition. We compared the average chemical compositions of Pleistocene, Pliocene, and Miocene core sediments from the boreholes BDP-96 and BDP-98 and sediments of the Paleo-Barguzin River avandelta and recognized groups of chemical elements marking warm and cold climatic periods. However, the difference in the chemical compositions of sediments in warm and cold periods is insignificant. Since an XRD analysis of mineral composition is usually performed for short time intervals, it was necessary to identify cold and warm intervals by the mineral composition calculated from the chemical composition of sediments. The mineral contents were estimated using the Selektor software. Based on the average contents of chemical elements, we computed the mineral composition of the bottom sediments throughout the BDP-98 section and studied its warm and cold periods. We have established that feldspars weakly respond to climatic changes, their contents show minor variations in warm and cold epochs, whereas the contents of mica minerals change seriously. Thus, clay minerals, together with biogenic silica, are a good indicator of paleoclimatic environmental changes. © 2014 V.S. Sobolev IGM, Siberian Branch of the RAS.
Keywords: Akademichesky Ridge; Barguzin River; Buryatia; Lake Baikal; Russian Federation; Bacillariophyta; borehole; chemical composition; clay mineral; climate variation; deep water; drainage basin; environmental change; environmental indicator; Miocene; Pleistocene; Pliocene; reconstruction; sediment chemistry; silica; stratigraphic correlation

Chronostratigraphy of Huoshiling Formation in the Songliao Basin, NE China: An overview - Qu, X.; Wang, P.; Gao, Y.; Wan, X. (Earth Science Frontiers, 2014)
The chronostratigraphy, sequence and distribution of Huoshiling Formation (H-Form) in the Songliao Basin are discussed and summarized on the basis of biostratigraphy, isotopic dating, lithostratigraphy as well as magnetostratigraphy. The H-Form is the first rifting basin stage with the filling sequence of mainly volcanic rocks in northeastern China and adjacent areas. Laterally, it is characterized by the widespread distribution, remarkable variation in volcanic eruption time and scale between fault depressions. The H-Form yielded plant megafossils in a wide range of periods. The sporo-pollen assemblages show a blooming age of the early Cretaceous. Characteristic megaspore fossil and magnetostratigraphy indicate the age of the Jurassic. Overlying sequence of the H-Form is also concerned in order to constrain its time span. The bottom of Yingcheng Formation is 130 Ma, the duration of Shahezi Formation is about 10 Ma, so that the top age of the H-Form should be ca. 140 Ma. The minimum duration of H-Form is calculated ca. 8 Ma, and its bottom age ought to approach about 150 Ma. The isotopic age dating on the volcanic rocks of H-Form mainly ranges from 140 Ma to 150 Ma. All these evidences above suggest that the age of H-Form can be well constrained from the Tithonian to the Berriasian or to the bottom of the Valanginian. The Jurassic-Cretaceous boundary(J/K boundary) in the Songliao Basin probably exists inside the Huoshiling Formation.
cited By 19
Keywords: Isotopes; Volcanic rocks; Chronostratigraphy; Huoshiling Formation; Jurassic-Cretaceous; Jurassic-Cretaceous boundary; Magnetostratigraphy; Shahezi formations; Songliao basin; Volcanic eruptions; Plants (botany)

Chronostratigraphy of the 600,000 year old continental record of Lake Van (Turkey) - Stockhecke, M.; Kwiecien, O.; Vigliotti, L.; Anselmetti, F.S.; Beer, J.; Çağatay, M.N.; Channell, J.E.T.; Kipfer, R.; Lachner, J.; Litt, T.; Pickarski, N.; Sturm, M. (Quaternary Science Reviews, 2014)
Lake Van sediment cores from the Ahlat Ridge and Northern Basin drill sites of the ICDP project PALEOVAN contain a wealth of information about past environmental processes. The sedimentary sequence was dated using climatostratigraphic alignment, varve chronology, tephrostratigraphy, argon-argon single-crystal dating, radiocarbon dating, magnetostratigraphy, and cosmogenic nuclides. Based on the lithostratigraphic framework, the different age constraints are compiled and a robust and precise chronology of the 600,000 year-old Lake Van record is constructed. Proxy records of total organic carbon content and sediment color, together with the calcium/potassium-ratios and arboreal pollen percentages of the 166-m-long event-corrected Ahlat Ridge record, mimic the Greenland isotope stratotype (NGRIP). Therefore, the proxy records are systematically aligned to the onsets of interstadials reflected in the NGRIP and synthesized Greenland ice-core stratigraphy. The chronology is constructed using 49 age control points derived from visual synchronization with the Greenland ice-core stratigraphy using the GICC05 timescale, an absolutely-dated speleothem timescale (e.g., Hulu, Sanbao, Linzhu cave) and the Epica Dome C timescale. In addition, the uppermost part of the sequence is complemented with four ages from Holocene varve chronology and three calibrated radiocarbon ages. Furthermore, nine argon-argon ages and a comparison of the relative paleointensity record of the magnetic field with reference curve PISO-1500 confirm the accuracy of the age model. Also the identification of the Laschamp event via measurements of 10Be in the sediment confirms the presented age model. The chronology of the Ahlat Ridge record is transferred to the 79-m-long event-corrected composite record from the Northern Basin and supplemented by additional radiocarbon dating on organic marco-remains. The basal age of the Northern Basin record is estimated at 90ka. The variations of the time series of total organic carbon content, the Ca/K ratio, and the arboreal pollen percentages illustrate that the presented chronology links ice-marine-terrestrial stratigraphies and that the paleoclimate data are suited for reconstructions and modeling of the Quaternary and Pleistocene climate evolution in the Near East at millennial timescales. Furthermore, the chronology of the last 250ka can be used to test other dating techniques. © 2014 Elsevier Ltd.
cited By 71
Keywords: Argon; Glacial geology; Ice control; Isotopes; Lakes; Organic carbon; Sediments; Single crystals; Stratigraphy; ICDP project PALEOVAN; Long terrestrial paleoenvironmental records; Magnetostratigraphy; Radiometric dating; Tephrostratigraphy; Ice; argon-argon dating; chronostratigraphy; lithostratigraphy; magnetostratigraphy; NorthGRIP; paleoclimate; Quaternary; radiometric method; sediment core; sediment property; sedimentary sequence; tephrochronology; total organic carbon; Lake Van; Turkey

Clay mineral records of the Erlangjian drill core sediments from the Lake Qinghai Basin, China - Zeng, MengXiu; Song, YouGui; An, ZhiSheng; Chang, Hong; Li, Yue (Science China Earth Sciences, 2014)
Located at the northeastern margin of the Qinghai-Tibet Plateau (QTP) in the Asian interior, the Lake Qinghai is sensitive to environmental change and thus an outstanding site for studying paleoenvironmental changes. Thick deposits in the Lake Qinghai provide important geological archives for obtaining high-resolution records of continental environmental history. The longest drilling core obtained from the Lake Qinghai, named Erlangjian (ELJ), reached about 1109 m and was investigated to determine its clay mineral assemblage and grain size distributions. Clay mineralogical proxies, including type, composition, and their ratios, as well as the illite crystallinity (KI) and chemical index (CI), in combination with grain size data, were used for reconstructing the history of paleoenvironmental evolution since the late Miocene in the Lake Qinghai Basin. The clay mineral records indicate that the clay mainly comprise detritus originating from peripheral material and has experienced little or no diagenesis. The proportion of authigenic origin was minor. Illite was the most abundant clay mineral, followed by chlorite, kaolinite, and smectite. Variations of clay mineral indexes reflect the cooling and drying trends in the Lake Qinghai region, and the grain size distribution is coincided with the clay minerals indexes. The paleoclimatic evolution of the Lake Qinghai Basin since the late Miocene can be divided into five intervals. The climate was relatively warm and wet in the early of late Miocene, then long-term trends in climate change character display cooling and drying; later in the late Miocene until early Pliocene the climate was in a short relatively warm and humid period; since then the climate was relatively colder and drier. These results also suggest multiple tectonic uplift events in the northeastern QTP. © 2014 Science China Press and Springer-Verlag Berlin Heidelberg.
Keywords: China; Qinghai; Qinghai Lake; Qinghai-Xizang Plateau; Clay minerals; Climate change; Grain size and shape; Kaolinite; Tectonics; Clay mineral assemblages; Grain size distribution; Lake Qinghai; Paleoclimates; Paleoenvironmental change; Qinghai Tibet plateau; Tectonic uplift; Weathering conditions; clay mineral; grain size; Miocene; paleoclimate; paleoenvironment; proxy climate record; sediment core; uplift; weathering; Lakes

Climate variability over the last 92 ka in SW Balkans from analysis of sediments from Lake Prespa - Panagiotopoulos, K.; B{ohm, A.; Leng, M.J.; Wagner, B.; Sch{abitz, F. (Climate of the Past, 2014)
The transboundary Lake Prespa (Albania/former Yugoslav Republic of Macedonia/Greece) has been recognized as a conservation priority wetland. The high biodiversity encountered in the catchment at present points to the refugial character of this mountainous region in the southwestern Balkans. A lake sediment core retrieved from a coring location in the northern part of the lake was investigated through sedimentological, geochemical, and palynological analyses. Based on tephrochronology, radiocarbon and electron spin resonance (ESR) dating, and cross correlation with other Northern Hemisphere records, the age model suggests that the basal part of core Co1215 reaches back to 92 ka cal BP. Here we present the responses of this mid-altitude site (849 m a.s.l.) to climate oscillations during this interval and assess its sensitivity to millennial-scale variability. Endogenic calcite precipitation occurred in marine isotope stages (MIS) 5 and 1 and is synchronous with periods of increased primary production (terrestrial and/or lacustrine). Periods of pronounced phytoplankton blooms (inferred from green algae and dinoflagellate concentrations) are recorded in MIS 5 and MIS 1 and suggest that the trophic state and lake levels underwent substantial fluctuations. Three major phases of vegetation development are distinguished: the forested phases of MIS 5 and MIS 1 dominated by deciduous trees with higher temperatures and moisture availability, the open landscapes of MIS 3 with significant presence of temperate trees, and the pine-dominated open landscapes of MIS 4 and MIS 2 with lower temperatures and moisture availability. Our findings suggest significant changes in forest cover and landscape openness, as well as in the properties of the vegetation belts (composition and distribution) over the period examined. The study area most likely formed the upper limit of several drought-sensitive trees (temperate tree refugium) at these latitudes in the Mediterranean mountains. © Author(s) 2014.
Keywords: Balkan; Turkmenistan; algal bloom; climate variation; electron spin resonance dating; mountain region; Northern Hemisphere; paleoclimate; palynology; phytoplankton; primary production; radiocarbon dating; sediment core; tephrochronology; transboundary cooperation

Comparative mineral chemistry and textures of SAFOD fault gouge and damage-zone rocks - Moore, D.E. (Journal of Structural Geology, 2014)
Creep in the San Andreas Fault Observatory at Depth (SAFOD) drillhole is localized to two foliated gouges, the central deforming zone (CDZ) and southwest deforming zone (SDZ). The gouges consist of porphyroclasts of serpentinite and sedimentary rock dispersed in a foliated matrix of Mg-smectite clays that formed as a result of shearing-enhanced reactions between the serpentinite and quartzofeldspathic rocks. The CDZ takes up most of the creep and exhibits differences in mineralogy and texture from the SDZ that are attributable to its higher shearing rate. In addition, a 0.2-m-wide sector of the CDZ at its northeastern margin (NE-CDZ) is identical to the SDZ and may represent a gradient in creep rate across the CDZ. The SDZ and NE-CDZ have lower clay contents and larger porphyroclasts than most of the CDZ, and they contain veinlets and strain fringes of calcite in the gouge matrix not seen elsewhere in the CDZ. Matrix clays in the SDZ and NE-CDZ are saponite and corrensite, whereas the rest of the CDZ lacks corrensite. Saponite is younger than corrensite, reflecting clay crystallization under declining temperatures, and clays in the more actively deforming portions of the CDZ have better equilibrated to the lower-temperature conditions. © 2014.
cited By 19
Keywords: Corrensite; Fault gouge; SAFOD; San Andreas fault; Saponite; Shearing-enhanced reactions; corrensite; creep; damage; deformation; fault gouge; mineralogy; San Andreas Fault; saponite; sedimentary rock; serpentinite; shear zone; texture

Comparison of petrophysical properties of impactites for four meteoritic impact structures - Popov, Y.; Mayr, S.; Romushkevich, R.; Burkhardt, H.; Wilhelm, H. (Meteoritics and Planetary Science, 2014)
We reanalyzed and compared unique data sets, which we obtained in the frame of combined petrophysical and geothermal investigations within scientific drilling projects on four impact structures: the Puchezh-Katunki impact structure (Vorotilovo borehole, Russia), the Ries impact structure (Noerdlingen-73 borehole, Germany), the Chicxulub impact structure (ICDP Yaxcopoil-1 borehole, Mexico), and the Chesapeake impact structure (ICDP-USGS-Eyreville borehole, USA). For a joined interpretation, we used the following previously published data: thermal properties, using the optical scanning technique, and porosities, both measured on densely sampled halfcores of the boreholes. For the two ICDP boreholes, we also used our previously published P-wave velocities measured on a subset of cores. We show that thermal conductivity, thermal anisotropy, porosity, and velocity can be correlated with shock metamorphism (target rocks of the Puchezh-Katunki and Ries impact structures), and confirm the absence of shock metamorphism in the samples taken from megablocks (Chicxulub and Chesapeake impact structure). The physical properties of the lithic impact breccias and suevites are influenced mainly by their impact-related porosity. Physical properties of lower porosity lithic impact breccias and suevites are also influenced by their chemical composition. These data allow for a distinction between different types of breccias due to differences concerning the texture and chemistry and the different amounts of melt and rock clasts. © The Meteoritical Society, 2014.

Caldera subsidence in extensional tectonics - Carlino, Stefano; Tramelli, Anna; Somma, Renato (Bulletin of Volcanology, 2014)

Comparison of petrophysical properties of impactites for four meteoritic impact structures - Popov, Y.; Mayr, S.; Romushkevich, R.; Burkhardt, H.; Wilhelm, H. (Meteoritics and Planetary Science, 2014)
We reanalyzed and compared unique data sets, which we obtained in the frame of combined petrophysical and geothermal investigations within scientific drilling projects on four impact structures: the Puchezh-Katunki impact structure (Vorotilovo borehole, Russia), the Ries impact structure (Noerdlingen-73 borehole, Germany), the Chicxulub impact structure (ICDP Yaxcopoil-1 borehole, Mexico), and the Chesapeake impact structure (ICDP-USGS-Eyreville borehole, USA). For a joined interpretation, we used the following previously published data: thermal properties, using the optical scanning technique, and porosities, both measured on densely sampled halfcores of the boreholes. For the two ICDP boreholes, we also used our previously published P-wave velocities measured on a subset of cores. We show that thermal conductivity, thermal anisotropy, porosity, and velocity can be correlated with shock metamorphism (target rocks of the Puchezh-Katunki and Ries impact structures), and confirm the absence of shock metamorphism in the samples taken from megablocks (Chicxulub and Chesapeake impact structure). The physical properties of the lithic impact breccias and suevites are influenced mainly by their impact-related porosity. Physical properties of lower porosity lithic impact breccias and suevites are also influenced by their chemical composition. These data allow for a distinction between different types of breccias due to differences concerning the texture and chemistry and the different amounts of melt and rock clasts. © The Meteoritical Society, 2014.
cited By 5

Compressional and shear-wave velocities from gas hydrate bearing sediments: Examples from the India and Cascadia margins as well as Arctic permafrost regions - Riedel, M.; Goldberg, D.; Guerin, G. (Marine and Petroleum Geology, 2014)
Shear wave velocity data have been acquired at several marine gas hydrate drilling expeditions, including the India National Gas Hydrate Program Expedition 1 (NGHP-01), the Ocean Drilling Program (ODP) Leg 204, and Integrated Ocean Drilling Program (IODP) Expedition 311 (X311). In this study we use data from these marine drilling expeditions to develop an understanding of general grain-size control on the P- and S-wave properties of sediments. A clear difference in the downhole trends of P-wave (Vp) and S-wave (Vs) velocity and the Vp/Vs ratio from all three marine regions was observed: the northern Cascadia margin (IODP X311) shows the highest P-wave and S-wave velocity values overall and those from the India margin (Expedition NGHP-01) are the lowest. The southern Cascadia margin (ODP Leg 204) appears to have similar low P-wave and S-wave velocity values as seen off India. S-wave velocity values increase relative to the sites off India, but they are not as high as those seen on the northern Cascadia margin. Such regional differences can be explained by the amount of silt/sand (or lack thereof) occurring at these sites, with northern Cascadia being the region of the highest silt/sand occurrences. This grain-size control on P-wave and S-wave velocity and associated mineral composition differences is amplified when compared to the Arctic permafrost environments, where gas hydrate predominantly occurs in sand- and silt-dominated formations. Using a cross-plot of gamma ray values versus the Vp/Vs ratio, we compare the marine gas hydrate occurrences in these regions: offshore eastern India margin, offshore Cascadia margin, the Ignik-Sikumi site in Alaska, and the Mallik 5L-38 site in the Mackenzie Delta. The log-data from the Arctic permafrost regions show a strongly linear Vp-Vs relationship, similar to the previously defined empirical relationships by Greenberg and Castagna (1992). P- and S-wave velocity data from the India margin and ODP Leg 204 deviate strongly from these linear trends, whereas data from IODP X311 plot closer to the trend of the Arctic data sets and previously published relationships. Three new linear relationships for different grain size marine sediment hosts are suggested:. a)mud-dominated (Mahanadi Basin, ODP Leg 204 & NGHP-01-17): Vs=1.5854×Vp-2.1649b)silty-mud (KG Basin): Vs=0.8105×Vp-1.0223c)silty-sand (IODP X311): Vs=0.5316×Vp-0.4916We investigate the relationship of gas hydrate saturation determined from electrical resistivity on the Vp/Vs ratio and found that the sand-dominated Arctic hosts show a clearly decreasing trend of Vp/Vs ratio with gas hydrate saturation. Though limited due to lower overall GH saturations, a similar trend is seen for sites from IODP X311 and at the ash-dominated NGHP-01-17 sediment in the Andaman Sea. Gas hydrate that occurs predominantly in fractured clay hosts show a different trend where the Vp/Vs ratio is much higher than at sand-dominated sites and remains constant or increases slightly with increasing gas hydrate saturation. This trend may be the result of anisotropy in fracture-dominated systems, where P- and S-wave velocities appear higher and Archie-based saturations of gas hydrate are overestimated. Gas hydrate concentrations were also estimated in these three marine settings and at Arctic sites using an effective medium model, combining P- and S-wave velocities as equally weighted constraints on the calculation. The effective medium approach generally overestimates S-wave velocity in high-porosity, clay-dominated sediments, but can be accurately used in sand-rich formations. © 2014.
cited By 20

Coseismic velocity change associated with the 2011 Van earthquake (M7.1): Crustal response to a major event - Acarel, D.; Bulut, F.; Bohnhoff, M.; Kartal, R. (Geophysical Research Letters, 2014)
Monitoring coseismic velocity changes is a major challenge, since the Earth crust has to be uniformly sampled at preseismic, coseismic, and postseismic stages using repeating active or natural sources. Here we investigate the crustal response to the 2011 Van/Turkey earthquake using ambient noise, which provides the best possible temporal resolution. Combined recordings from the nearest five broadband stations are analyzed for a time period of 6 months framing the main shock. We observe a coseismic velocity decrease of up to 0.76% in the vicinity of the main shock in the frequency range of 0.05-0.3 Hz. The velocity drop is largest at close proximity to the earthquake hypocenter and decreases systematically with distance. We also find a correlation between coseismic velocity decrease and the amount of coseismic slip on the rupture plane. The observed velocity drop shows the drastic response of the brittle crust in response to a major earthquake. Key Points A coseismic velocity change The 2011 Van earthquake Scaling between the velocity change and slip ©2014. American Geophysical Union. All Rights Reserved.
cited By 10
Keywords: Acoustic noise; Drops; Earthquakes; Structural geology; 2011 Van earthquake/Turkey; Ambient noise; Broadband station; Close proximity; Coseismic slips; Frequency ranges; Temporal resolution; Velocity changes; Velocity

Cyclostratigraphy and orbital tuning of the terrestrial upper Santonian-Lower Danian in Songliao Basin, northeastern China - Wu, H.; Zhang, S.; Hinnov, L.A.; Jiang, G.; Yang, T.; Li, H.; Wan, X.; Wang, C. (Earth and Planetary Science Letters, 2014)
The Songke-1 north (SK-1n) borehole recovered a continuous, 1541.66 m Late Santonian-Early Danian terrestrial succession in Songliao Basin (SB), northeastern China. It provides a unique record for improving our understanding of continental paleoclimate and ecological system in Cretaceous greenhouse world. Here we use thorium (Th) logging data as a paleoenvironmental and paleoclimatic proxy to conduct a detailed cyclostratigraphic study on the SK-1n core. Power spectra, evolutionary fast Fourier transformation and wavelet analysis all reveal significant decameter- to meter-scale sedimentary cycles in the Nenjiang (K2n), Sifangtai (K2s) and Mingshui (K2m) formations. The ratios of cycle wavelengths in these stratigraphic units are 20:5:2:1, and are interpreted as Milankovitch cycles of 405 kyr and 100 kyr eccentricity, 38.4 kyr obliquity and 20 kyr precession cycles, respectively. An astronomical time scale (ATS) is established by tuning filtered 405 kyr eccentricity cycles to a target curve of the astronomical solution La2010d based on the magnetostratigraphic time framework of the SK-1n borehole. This ATS provides precise numerical ages for stratigraphic boundaries, biozones, geological and geophysical events, and serves as a basis for correlation of strata and events between marine and terrestrial systems. The Cretaceous/Paleogene (K/Pg), Campanian/Maastrichtian, Santonian/Campanian boundaries are estimated at core depths of 318 m, 752.8 m and 1751.1 m, respectively. A 3.8 myr-long hiatus between the Nenjiang (K2n) and Sifangtai (K2s) formations occurs from 76.1 to 79.9 million years ago. The ages and durations of magnetochrons C33r to C30n are precisely estimated and provide new constraints on the Late Cretaceous Geomagnetic Polarity Time Scale (GPTS) and South Atlantic sea-floor spreading rates. © 2014 Elsevier B.V.
cited By 95
Keywords: Astronomical time scale (ATS); Continental environments; Cyclostratigraphy; Late cretaceous; Songliao basin; borehole; cyclostratigraphy; Danian; eccentricity; geological record; magnetostratigraphy; paleoclimate; paleoecology; paleoenvironment; proxy climate record; Santonian; seafloor spreading; stratigraphic boundary; thorium; timescale; Atlantic Ocean; Atlantic Ocean (South); China; Songliao Basin

Dating Palaeoproterozoic glacial deposits of the Fennoscandian Shield using detrital zircons from the Kola Peninsula, Russia - G{artner, Claudia; Bahlburg, Heinrich; Melezhik, Victor A; Berndt, Jasper (Precambrian Research, 2014)

David Blackwell's forty years in the Idaho desert, the foundation for 21st century geothermal research - McLing, T.; McCurry, M.; Cannon, C.; Neupane, G.; Wood, T.; Podgorney, R.; Welhan, J.; Mines, G.; Mattson, E.; Wood, R.; Palmer, C.; Smith, R. (Transactions - Geothermal Resources Council, 2014)
In the coming summer (Summer 2014), we will have another sampling campaign. The composition of waters presented in Table 1 as well as compositions of waters yet to be collected will be used for temperature estimates with MEG and traditional geothermometers. In addition to the geothermometry, different mixing models will be applied to delineate areas with high potential for geothermal resources in the ESRP. As the project progresses, more detailed reports will be presented/published in appropriate venues. Copyright © (2014) by the Geothermal Resources Council All right reserved.
cited By 2
Keywords: Aquifers; Heat transfer; Aquifer model; Blackwell Session; Enhanced geothermal; Geothermal; Snake river plains; System; Geothermal fields

Characterizing oxygen isotope variability and host water relation of modern and subfossil aquatic mosses - Zhu, Jiayun; L{ucke, Andreas; Wissel, Holger; Mayr, Christoph; Ohlendorf, Christian; Zolitschka, Bernd (Geochimica et Cosmochimica Acta, 2014)

Biomarker characteristics of source rocks in Well SK1 in Songliao Basin - Nie, ZY; Huang, QH; Xi, DP; Wan, XQ (Earth Sci. Front., 2014)

Deep permeability of the San Andreas Fault from San Andreas Fault Observatory at Depth (SAFOD) core samples - Morrow, C.A.; Lockner, D.A.; Moore, D.E.; Hickman, S. (Journal of Structural Geology, 2014)
The San Andreas Fault Observatory at Depth (SAFOD) scientific borehole near Parkfield, California crosses two actively creeping shear zones at a depth of 2.7km. Core samples retrieved from these active strands consist of a foliated, Mg-clay-rich gouge containing porphyroclasts of serpentinite and sedimentary rock. The adjacent damage zone and country rocks are comprised of variably deformed, fine-grained sandstones, siltstones, and mudstones. We conducted laboratory tests to measure the permeability of representative samples from each structural unit at effective confining pressures, Pe up to the maximum estimated in situ Pe of 120MPa. Permeability values of intact samples adjacent to the creeping strands ranged from 10-18 to 10-21m2 at Pe=10MPa and decreased with applied confining pressure to 10-20-10-22m2 at 120MPa. Values for intact foliated gouge samples (10-21-6×10-23m2 over the same pressure range) were distinctly lower than those for the surrounding rocks due to their fine-grained, clay-rich character. Permeability of both intact and crushed-and-sieved foliated gouge measured during shearing at Pe≥70MPa ranged from 2 to 4×10-22m2 in the direction perpendicular to shearing and was largely insensitive to shear displacement out to a maximum displacement of 10mm. The weak, actively-deforming foliated gouge zones have ultra-low permeability, making the active strands of the San Andreas Fault effective barriers to cross-fault fluid flow. The low matrix permeability of the San Andreas Fault creeping zones and adjacent rock combined with observations of abundant fractures in the core over a range of scales suggests that fluid flow outside of the actively-deforming gouge zones is probably fracture dominated. © 2013.
cited By 33
Keywords: Clay minerals; Deformation; Flow of fluids; Fracture; Mechanical permeability; Observatories; Rock pressure; Shearing; Strike-slip faults; Confining pressures; Fault gouge; Low matrix permeability; Maximum displacement; Representative sample; SAFOD; San Andreas fault; Shear displacement; Core samples; confining pressure; country rock; displacement; fault gouge; permeability; San Andreas Fault; sedimentary rock; serpentinite; shear zone; California; San Andreas; United States

A 600,000 year long continental pollen record from Lake Van, eastern Anatolia (Turkey) - Litt, T.; Pickarski, N.; Heumann, G.; Stockhecke, M.; Tzedakis, P.C. (Quaternary Science Reviews, 2014)
Lake Van is the fourth largest terminal lake in the world (38.5°N, 43°E, volume 607km3, area 3570km2, maximum water depth 460m), extending for 130km WSW-ENE on the eastern Anatolian high plateau, Turkey. The sedimentary record of Lake Van, partly laminated, obtains a long and continuous continental sequence that covers multiple interglacial-glacial cycles. Promoted by the potential of the sedimentary sequence for reconstructing the paleoecological and paleoclimate development of the Near East, a deep drilling operation was carried out in 2010 supported by the International Continental Scientific Drilling Program (ICDP). The 219m long continental pollen record presented here is based on a well-dated composite profile drilled on the so-called Ahlat Ridge in water depth of 360m encompassing the last 600,000 years. It is the longest continuous continental pollen record of the Quaternary in the entire Near East and central Asia obtained to date. The glacial-interglacial cycles and pronounced interstadials are clearly reflected in the vegetation development based on millennial-scale time resolution. In general, the glacial/stadial vegetation is characterized by dwarf-shrub steppe and desert steppe, whereas the climax vegetation of past interglacials can be described as oak steppe-forest similar to the present interglacial in this sensitive semi-arid region between the Black, Caspian, and Mediterranean Seas. By comparing the Lake Van pollen record with other western Asian and southern European long continental pollen sequences as well as marine and ice-core records, the regional variability of the climate signals is also discussed. © 2014.
cited By 108
Keywords: Eastern Anatolia; Lake vans; Long continental pollen record; Near East; Paleoclimates; climax; deciduous tree; deep drilling; glacial-interglacial cycle; ice core; paleoclimate; paleoecology; palynology; Quaternary; sedimentary sequence; water depth; Black Sea; Caspian Sea; Lake Van; Mediterranean Sea; Turkey

Investigating reservoir characteristics by mapping P wave velocity dispersion - Sun, L.F.; Milkereit, B. (76th European Association of Geoscientists and Engineers Conference and Exhibition 2014: Experience the Energy - Incorporating SPE EUROPEC 2014, 2014)
Velocity dispersion allows special insight into the physical properties of reservoir rocks. The total velocity dispersion may provide a link to rock physical properties, such as permeability and concentration of a certain material, but the shape of a velocity dispersion curve, including the critical frequency (fc), can provide more essential information, such as the existence of different attenuation mechanisms. For this purpose, continuous velocity measurement in a broad frequency band is desirable. In this study, we use broadband full-waveform multi-channel sonic logging data from Mallik gas hydrate research wells and measure the P wave velocity (Vp) dispersion curves with the filter-semblance-correlation (FiSCo) method. Profiles of Vp gradient and accumulated dispersion are obtained. In the profiles, the total Vp dispersion and fc are observed varying with several rock physical properties. The Biot's model is then applied to interpret the results. Also Biot's model can generally fit the results, more realistic models are needed to better describe the complicated geological condition of the gas hydrate reservoir.
cited By 1
Keywords: Acoustic logging; Acoustic wave velocity; Gas hydrates; Hydration; Physical properties; Seismic waves; Wave propagation; Accumulated dispersion; Complicated geological conditions; Critical frequencies; Dispersion curves; Gas hydrate reservoir; Reservoir characteristic; Rock physical properties; Velocity dispersion; Dispersion (waves)

10Be content in clasts from fallout suevitic breccia in drill cores from the Bosumtwi impact crater, Ghana: Clues to preimpact target distribution - Losiak, Anna; Wild, Eva Maria; Michlmayr, Leonard; Koeberl, Christian (Meteoritics and Planetary Science, 2014)
Rocks from drill cores LB-07A (crater fill) and LB-08A (central uplift) into the Bosumtwi impact crater, Ghana, were analyzed for the presence of the cosmogenic radionuclide 10Be. The aim of the study was to determine the extent to which target rocks of various depths were mixed during the formation of the crater-filling breccia, and also to detect meteoric water infiltration within the impactite layer. 10Be abundances above background were found in two (out of 24) samples from the LB-07A core, and in none of five samples from the LB-08A core. After excluding other possible explanations for an elevated 10Be signal, we conclude that it is most probably due to a preimpact origin of those clasts from target rocks close to the surface. Our results suggest that in-crater breccias were well mixed during the impact cratering process. In addition, the lack of a 10Be signal within the rocks located very close to the lake sediment-impactite boundary suggests that infiltration of meteoric water below the postimpact crater floor was limited. This may suggest that the infiltration of the meteoric water within the crater takes place not through the aerial pore-space, but rather through a localized system of fractures. © The Meteoritical Society, 2014.

14C chronostratigraphy for Qinghai lake in China - Zhou, Weijian; Cheng, Peng; Timothy Jull, A.J.; Lu, Xuefeng; An, ZhiSheng; Wang, Hao; Zhu, Yizhi; Wu, Zhenkun (Radiocarbon, 2014)
Radiocarbon accelerator mass spectrometry (AMS) techniques were used to date total organic carbon and plant seeds in the 1Fs core sequence (36°48′N, 100°08′E) from Qinghai Lake, China. This core was drilled 18 m into Qinghai Lake sediments as part of an international cooperative research project, Scientific Drilling at Qinghai Lake in the Northeastern Tibetan Plateau: High-Resolution Paleoenvironmental Records of Eastern Asia Linked to Global Change, which began in 2004. Based on the differences in lithology and total organic content (TOC) in core 1Fs, the core was divided into 3 sections for age-modeling purposes: the upper 499 cm lacustrine silty clay to clay; the middle unit of silty clay with silt layers from 499-901 cm; and the lower 901-1861 cm silty clay, loess-like silt, and fine sand layers. Three different approaches are applied to the reservoir age problem. First, a simple linear regression gives an offset of 1342 yr. If the core is divided into three sections, linear regressions can be applied separately for the three segments, which results in an age estimate for the average hardwater effect of 135 yr BP for the surface section up to 499 cm. If extrapolated for deeper sections, these results imply a higher reservoir offset for those two sections, which may be as much as 1143 and 2523 yr, but this assumes that there are no discontinuities in the core. A third approach using a wiggle-matching approach gave an offset of 196 yr. This study concludes that the reservoir age of Qinghai Lake is complex, but these new data add to our understanding of the 14C chronology of Qinghai Lake for the last 32 ka. © 2014 by the Arizona Board of Regents on behalf of the University of Arizona.
Keywords: China; Qinghai; Qinghai Lake; accelerator mass spectrometry; age determination; chronostratigraphy; lacustrine deposit; lake ecosystem; radiocarbon dating; reservoir; total organic carbon

3D interpretation by integrating seismic and potential field data in the vicinity of the proposed COSC-1 drill site, central Swedish Caledonides - Hedin, Peter; Malehmir, Alireza; Gee, David G.; Juhlin, Christopher; Dyrelius, Dan (Geological Society, London, Special Publications, 2014)
Skip to Next Section The scientific drilling project COSC (Collisional Orogeny in the Scandinavian Caledonides), designed to study key questions concerning orogenic processes, aims to drill two fully cored boreholes to depths of c. 2.5 km each at carefully selected locations in west-central Sweden. The first of these, COSC-1, is scheduled for start late spring 2014 and will target the Seve Nappe Complex, characterized by inverted metamorphism and with parts that have evidently been subjected to hot ductile extrusion. In this study available seismic sections have been combined with surface geology to produce a 3D interpretation of the tectonic structures in the vicinity of the COSC-1 borehole. Constrained 3D inverse gravity modelling over the same area supports the interpretation, and the high-density Seve Nappe Complex stands out clearly in the model. Interpretation and models show that the maximum depth extent of the Seve Nappe Complex is less than 2.5 km, consistent with reflection seismic data. The gravity modelling also requires underlying units to comprise low-density material, consistent with the Lower Allochthon, but the modelling is unable to discern the d'ecollement separating the allochthons from the crystalline Precambrian basement.
Publisher: Geological Society of London Section: Development of the Seve nappe complex and its position within the orogen

A slice-and-view (FIB-SEM) study of clay gouge from the SAFOD creeping section of the San Andreas Fault at 2.7km depth - Warr, L.N.; Wojatschke, J.; Carpenter, B.M.; Marone, C.; Schleicher, A.M.; Pluijm, B.A. (Journal of Structural Geology, 2014)
The San Andreas Fault is one of the most studied earthquake-generating structures on Earth, but the reason that some sections are anomalously weak, and creep without apparent seismicity, remains poorly understood. Here, we present results from nanoscale (FIB-SEM) 3D microstructural observations of weak (friction coefficient of 0.095) SAFOD clay fault gouge containing serpentinite clasts, recovered from the active Central Deforming Zone at 2.7km vertical depth. Our nanoscale observations confirm that frictional slip and extreme weakness occurvia deformation of smectite clay that forms a shear fabric within the fault zone. We infer that creep initiates by fracture-controlled, substrate growth of oriented Mg-smectite on R, P and Y shears, followed by clay smearing and ductile flow of an evolving and expanding clay matrix. At the crystal-scale, pervasive sliding occurs along hydrated smectite interlayers and surfaces occupied by exchangeable Mg- and Ca-ions, with slip typically spaced at 3-5 lattice layers apart. We conclude that the strength and seismic behaviour of major tectonic faults at shallow crustal levels evolves as clay fabric develops with accumulated fault slip. © 2014 Elsevier Ltd.
cited By 24
Keywords: Clay fabrics; SAFOD; San Andreas fault; SEM and TEM; Smectites; Creep; creep; deformation; fault gouge; fault zone; magnesium; San Andreas Fault; scanning electron microscopy; seismicity; smectite; transmission electron microscopy

A 60,000-year record of hydrologic variability in the Central Andes from the hydrogen isotopic composition of leaf waxes in Lake Titicaca sediments - Fornace, Kyrstin L.; Hughen, Konrad A.; Shanahan, Timothy M.; Fritz, Sherilyn C.; Baker, Paul A.; Sylva, Sean P. (Earth and Planetary Science Letters, 2014)
A record of the hydrogen isotopic composition of terrestrial leaf waxes (δDwax) in sediment cores from Lake Titicaca provides new insight into the precipitation history of the Central Andes and controls of South American Summer Monsoon (SASM) variability since the last glacial period. Comparison of the δDwax record with a 19-kyr δD record from the nearby Illimani ice core supports the interpretation that precipitation δD is the primary control on δDwax with a lesser but significant role for local evapotranspiration and other secondary influences on δDwax. The Titicaca δDwax record confirms overall wetter conditions in the Central Andes during the last glacial period relative to a drier Holocene. During the last deglaciation, abrupt δDwax shifts correspond to millennial-scale events observed in the high-latitude North Atlantic, with dry conditions corresponding to the Bølling-Allerød and early Holocene periods and wetter conditions during late glacial and Younger Dryas intervals. We observe a trend of increasing monsoonal precipitation from the early to the late Holocene, consistent with summer insolation forcing of the SASM, but similar hydrologic variability on precessional timescales is not apparent during the last glacial period. Overall, this study demonstrates the relative importance of high-latitude versus tropical forcing as a dominant control on glacial SASM precipitation variability. © 2014 Elsevier B.V.
Keywords: Lake Titicaca; Central Andes; Holocenes; Hydrogen isotopic composition; Last glacial period; Stable hydrogen isotope; Summer monsoon; deglaciation; glacial lake; Holocene; hydrogen isotope; isotopic composition; Last Glacial Maximum; monsoon; precipitation (chemistry); sediment core; stable isotope; summer; Younger Dryas

A fixed sublithospheric source for the late Neogene track of the Yellowstone hotspot: Implications of the Heise and Picabo volcanic fields - Anders, M.H.; Rodgers, D.W.; Hemming, S.R.; Saltzman, J.; Divenere, V.J.; Hagstrum, J.T.; Embree, G.F.; Walter, R.C. (Journal of Geophysical Research: Solid Earth, 2014)
The Heise and Picabo volcanic fields of eastern Idaho are part of the more extensive time-transgressive Yellowstone-Snake River Plain hotspot track. Calderas associated with these two silicic volcanic fields are buried under 1 to 3 km of younger basalt, so their locations and eruption record histories have been based on analysis of silicic units along the margins of the eastern Snake River Plain along with some limited geophysical data. A 1.5 km borehole penetrating through basalt into underlying silicic rocks provides new data we used to reassess caldera locations and the timing of eruptions of these volcanic fields. Using these new caldera locations, we calculate an extension-adjusted rate of 2.35 cm/yr for the North American plate over the last 6.66 m.y. and a velocity of 2.30 cm/yr over the 10.27 m.y. Recalculation of a previously determined plate velocity-based migration of the deformation field surrounding the eastern Snake River Plain yields an extension-adjusted rate of 2.38 ± 0.21 cm/yr. These migration rates all fall within the previously published range of North American plate velocities of 2.2 ± 0.8 cm/yr, 2.4 cm/yr, and 2.68 ± 0.78 cm/yr based on a global hot spot reference frame. The consistency of these rates suggest that over the last 10 m.y., the Yellowstone hot spot is fixed with respect to the motion of the North American plate and therefore consistent with a classical deep-sourced hotspot model. ©2014. American Geophysical Union. All Rights Reserved.
cited By 20
Keywords: basalt; caldera; deformation; hot spot; ignimbrite; lithospheric structure; Neogene; North American plate; volcanic eruption; volcanic landform; Idaho; Snake River Plain; United States; Yellowstone River

Biogeochemical variability during the past 3.6 million years recorded by FTIR spectroscopy in the sediment record of Lake El'gygytgyn, Far East Russian Arctic - Meyer-Jacob, C.; Vogel, H.; Gebhardt, A. C.; Wennrich, V.; Melles, M.; Rosen, P. (Climate of the Past, 2014)
A number of studies have shown that Fourier transform infrared spectroscopy (FTIRS) can be applied to quantitatively assess lacustrine sediment constituents. In this study, we developed calibration models based on FTIRS for the quantitative determination of biogenic silica (BSi; n Combining double low line 420; gradient: 0.9-56.5%), total organic carbon (TOC; n Combining double low line 309; gradient: 0-2.9%), and total inorganic carbon (TIC; nCombining double low line 152; gradient: 0-0.4%) in a 318 m-long sediment record with a basal age of 3.6 million years from Lake El'gygytgyn, Far East Russian Arctic. The developed partial least squares (PLS) regression models yield high cross-validated (CV) R2CV Combining double low line 0.86-0.91 and low root mean square error of cross-validation (RMSECV) (3.1-7.0% of the gradient for the different properties). By applying these models to 6771 samples from the entire sediment record, we obtained detailed insight into bioproductivity variations in Lake El'gygytgyn throughout the middle to late Pliocene and Quaternary. High accumulation rates of BSi indicate a productivity maximum during the middle Pliocene (3.6-3.3 Ma), followed by gradually decreasing rates during the late Pliocene and Quaternary. The average BSi accumulation during the middle Pliocene was ∼3 times higher than maximum accumulation rates during the past 1.5 million years. The indicated progressive deterioration of environmental and climatic conditions in the Siberian Arctic starting at ca. 3.3 Ma is consistent with the first occurrence of glacial periods and the finally complete establishment of glacial-interglacial cycles during the Quaternary. ©Author(s) 2014.
cited By 19
Keywords: accumulation rate; climate variation; FTIR spectroscopy; glacial-interglacial cycle; paleoclimate; Quaternary; regression analysis; Chukchi; Elgygytgyn Lake; Far East; Russian Federation

A scaling law to characterize fault-damage zones at reservoir depths - Johri, M.; Zoback, M.D.; Hennings, P. (AAPG Bulletin, 2014)
We analyze fracture-density variations in subsurface fault-damage zones in two distinct geologic environments, adjacent to faults in the granitic SSC reservoir and adjacent to faults in arkosic sandstones near the San Andreas fault in central California. These damage zones are similar in terms of width, peak fracture or fault (FF) density, and the rate of FF density decay with distance from the main fault. Seismic images from the SSC reservoir exhibit a large basement master fault associated with 27 seismically resolvable second-order faults. A maximum of 5 to 6 FF/m (1.5 to 1.8 FF/ft) are observed in the 50 to 80 m (164 to 262 ft) wide damage zones associated with second-order faults that are identified in image logs from four wells. Damage zones associated with second-order faults immediately southwest of the San Andreas Fault are also interpreted using image logs from the San Andreas Fault Observatory at Depth (SAFOD) borehole. These damage zones are also 50-80 m wide (164 to 262 ft) with peak FF density of 2.5 to 6 FF/m (0.8 to 1.8 FF/ft). The FF density in damage zones observed in both the study areas is found to decay with distance according to a power law F = F0r-n. The fault constant F0 is the FF density at unit distance from the fault, which is about 10-30 FF/m (3.1-9.1 FF/ft) in the SSC reservoir and 6-17 FF/m (1.8-5.2 FF/ft) in the arkose. The decay rate n ranges from 0.68 to 1.06 in the SSC reservoir, and from 0.4 to 0.75 in the arkosic section. This quantification of damage-zone attributes can facilitate the incorporation of the geometry and properties of damage zones in reservoir flow simulation models. Copyright © 2014. The American Association of Petroleum Geologists. All rights reserved.
cited By 53
Keywords: Boreholes; Decay (organic); Well logging; Density decay; Fault damage zone; Fracture density; Geologic environment; Reservoir flow; San Andreas fault; Second orders; Seismic image; Strike-slip faults; damage mechanics; fault geometry; fault plane; fault propagation; fracture zone; sandstone; seismic stratigraphy; simulation; California; California; San Andreas; United States

Abrupt deglaciation on the northeastern Tibetan Plateau: Evidence from Lake Qinghai - Liu, Xiuju; Colman, Steven M.; Brown, Erik T.; Henderson, Andrew C.G.; Werne, Josef P.; Holmes, Jonathan A. (Journal of Paleolimnology, 2014)
We inferred the climate history for Central Asia over the past 20,000 years, using sediments from core QH07, taken in the southeastern basin of Lake Qinghai, which lies at the northeastern margin of the Tibetan Plateau. Results from multiple environmental indicators are internally consistent and yield a clear late Pleistocene and Holocene climate record. Carbonate content and total organic carbon (TOC) in Lake Qinghai sediments are interpreted as indicators of the strength of the Asian summer monsoon. Warm and wet intervals, associated with increased monsoon strength, are indicated by increased carbonate and TOC content. During the glacial period ( 20,000 to 14,600 cal year BP), summer monsoon intensity remained low and relatively constant at Lake Qinghai, suggesting cool, dry, and relatively stable climate conditions. The inferred stable, cold, arid environment of the glacial maximum seems to persist through the Younger Dryas time period, and little or no evidence of a warm interval correlative with the Bølling-Allerød is found in the QH07 record. The transition between the late Pleistocene and the Holocene, about 11,500 cal year BP, was abrupt, more so than indicated by speleothems in eastern China. The Holocene ( 11,500 cal year BP to present) was a time of enhanced summer monsoon strength and greater variability, indicating relatively wetter but more unstable climatic conditions than those of the late Pleistocene. The warmest, wettest part of the Holocene, marked by increased organic matter and carbonate contents, occurred from 11,500 to 9,000 cal year BP, consistent with maximum summer insolation contrast between 30°N and 15°N. A gradual reduction in precipitation (weakened summer monsoon) is inferred from decreased carbonate content through the course of the Holocene. We propose that changes in the contrast of summer insolation between 30°N and 15°N are the primary control on the Asian monsoon system over glacial/interglacial time scales. Secondary influences may include regional and global albedo changes attributable to ice-cover and vegetation shifts and sea level changes (distance from moisture source in Pacific Ocean). The abruptness of the change at the beginning of the Holocene, combined with an increase in variability, suggest a threshold for the arrival of monsoonal rainfall at the northeastern edge of the Tibetan Plateau. © 2013 Springer Science+Business Media Dordrecht.
Keywords: China; Qinghai; Qinghai Lake; Qinghai-Xizang Plateau; climate conditions; deglaciation; environmental indicator; Holocene; paleoclimate; precipitation (climatology); sediment analysis; timescale

Advances of continental scientific drilling programs in China - Sun, Y.H.; Mao, J.S.; Liu, B.C.; Fan, X.P. (International Journal of Earth Sciences and Engineering, 2014)
Continental scientific drilling is an important scientific and engineering project that has been attracting world-wide attentions. Since International Continental Scientific Drilling Program (ICDP) was founded in 1996, great advances have been brought about in many fields of earth sciences by continental scientific drilling. As one of the three founding members of ICDP, China has also achieved a lot of developments in continental scientific drilling. This paper summarizes the continental scientific drilling projects in China, such as the Chinese Continental Scientific Drilling (CCSD), the Lake Qinghai Scientific Drilling Project(CESD), and the preliminary progresses of the third approved ICDP project of China–the Chinese Cretaceous Continental Scientific Drilling Project(SK-I,SK-II project). The implementing Wenchuan Fault Scientific Drilling Program (WFSD) is also included in the paper. Their scientific objectives, drilling and coring situations and drilling equipment used in the project are all introduced. © 2014 CAFET-INNOVA TECHNICAL SOCIETY.
cited By 1
Keywords: Engineering; Industrial engineering; Continental scientific drillings; Coring situation; Engineering project; Lake Qinghai; Scientific drilling; Scientific objectives; Drilling equipment; Drilling equipment; Chinese Continental Scientific Drilling Project; deep drilling; Earth science; regional geology; Earth structure; equipment; international organization; China

Ambient noise analysis in the eastern sea of Marmara region in northwest Turkey: Lateral variations of the crustal velocity field - Acarel, D.; Bulut, F.; Bohnhoff, M. (Bulletin of the Seismological Society of America, 2014)
We analyze the ambient seismic-noise field in order to investigate the crustal structure at the North Anatolian fault zone (NAFZ) in northwest Turkey. We focus on the eastern Sea of Marmara section, where the NAFZ is in the final phase of the seismic cycle prior to an expected major (M >7) earthquake. We apply crosscorrelation analysis of the seismic ambient noise to determine the spectral dependence of the seismic velocity in order to image the crustal structure at seismogenic depth. Time-domain cross correlations are calculated for available station pairs in the target area. Interstation distances span 0.3-90 km. Here, the vertical component is analyzed in order to recover fundamental-mode Rayleigh waves in the 0.05-1.1 Hz frequency range. Group velocity dispersion curves are obtained for selected correlation paths in particular to address the azimuthal dependence of the velocity field. In the frequency band of interest, average group velocities range between 1:8 and 3:5 km=s. Dispersion curves corresponding to the north-south-trending paths crossing the main NAFZ fault branch below the eastern Sea of Marmara show low group velocities between 1:5 and 1:8 km=s, which is well explained by the 3-4 km-deep Çidotlessnarcidotlessk basin, located between the two major fault branches, the Princes Islands and Armutlu fault segments. In contrast, ray paths restricted to within the mainland of Istanbul and the Armutlu peninsulas (primarily trending east-west) show higher group velocities up to 3:2 km=s. By averaging the dispersion curves, we determine an optimized 1D S-wave velocity model for the eastern Sea of Marmara region, allowing for a significant improvement in hypocenter determination for local seismicity.
cited By 1
Keywords: Acoustic noise; Frequency bands; Group velocity dispersion; Light velocity; Wave propagation; Azimuthal dependence; Cross correlations; Cross-correlation analysis; Group velocity dispersion curve; Low group velocity; North Anatolian Fault Zone; Seismic velocities; Spectral dependences; Earthquakes; ambient noise; crustal structure; dispersion; earthquake hypocenter; North Anatolian Fault; S-wave; seismic noise; seismic velocity; seismicity; spectral analysis; Sea of Marmara; Turkey

Annealing the chicxulub impact: Paleogene yucatàn carbonate slope development in the chicxulub Impact Basin, Mexico - Whalen, M.T.; Gulick, S.S.P.; Pearson, Z.F.; Norris, R.D.; Cruz, L.P.; Fucugauchi, J.U. (SEPM Special Publications, 2014)
Stratigraphic analysis of the Yaxcopoil-1 core (Yax-1) and seismic analysis of offshore two-dimensional (2D) seismic data provide insight into the Paleogene history of the Chicxulub impact basin and Yucatàn platform development. Ten facies were identified based on core and petrographic analysis. Slope sediments include redeposited and background facies. The former are carbonate supportstones and finer-grained facies with evidence of soft sediment deformation deposited as gravity flows. Background facies are shales and mud-wackestone interpreted as sub-storm wave base suspension deposits. Depositional setting ranged from a steep bathyal slope inside the crater rim to neritic outer carbonate platform environments of the seaward prograding Yucatàn platform. Through sequence stratigraphic analysis of Yax-1, we documented five sequences based on identification of transgressive and maximum flooding surfaces and facies stacking patterns. Biostratigraphic ages are equivocal, but they imply that sequences 1 and 2 are Early Paleocene, sequences 3 and 4 are Early Eocene, and sequence 5 is Middle Eocene. Coarse-grained redeposited carbonates in lower sequences 1 to 4 indicate slope gravity flow processes. Upper sequence 3 records the first evidence of fine-grained turbidites, indicating progradation of the Yucatàn platform. By the top of sequence 4, facies indicate that the platform margin had prograded over the position of Yax-1. Seismic analysis identified six units, the lower five of which appear to correlate with cored Yax-1 sequences. The geometry and distribution of seismic units A and B indicate deposition confined to the western and central parts of the basin. Unit C, with two sets of clinoforms, records a major progradational event in the eastern part of the basin likely related to Yax-1 sequence 3 turbidites. Mainly parallel reflectors in seismic units D and E indicate relatively level bottom conditions similar to the environments of facies in upper sequence 4 and 5. The tops of units D and E, in proximal settings, are erosionally truncated. This unconformity marks the base of unit F, which is characterized by discontinuous reflectors and is restricted to the northeastern portion of the basin. Stratal patterns in seismic units C to E are more controlled by relative sea-level change, as suggested by the development of clinoforms and regional unconformities. If Chicxulub and others like the Chesapeake Bay structure are representative, large marine impacts in tectonically quiescent regions may dominate local depositional environments for millions to tens of millions of years postimpact before returning control to eustasy. Copyright © 2013 SEPM (Society for Sedimentary Geology).
cited By 11

Deep ore exploration of sulfides with seismic reflection profiling in outokumpu, Finland - Heinonen, S.E.; Aatos, S.; Heikkinen, P.J.; Hellqvist, N.; Kurimo, M.; Levaniemi, H.; Kukkonen, I.T. (76th EAGE Conference and Exhibition 2014, Workshops, 2014)
A network ofhigh resolution seismic reflection profiles was acquired in Outokumpu, Finland. Outokumpu is one of the most important mining regions in Finland where active sulphide exploration is ongoing. Over 5 km long spread with 402 active channels and nominal vibroseismic source point interval of 25 m guarantee high fold and good signal-to-noise ratio of the seismic data. These high quality data have been commercially processed by Vniigeofizika, Moscow with standard hardrock seismic processing flow including careful static corrections. Seismic sections were migrated and depth converted with constant velocity (5400 m/s) that corresponds approximately to the seismic P-wave velocity in the main lithology of the area, mica schist. Additionally to seismic velocities, also densities of the main lithologies have been measured from the 2.5 km long drill hole. This enables estimation of the main sources of reflectivity in the Outokumpu area. Encouragingly, typical ore hosting lithological assemblage was found to be brightly reflective both externally and internally due to interlayers ofhigh acoustic impedance skarns and low acoustic impedance serpentinites. All together nine interconnected seismic profiles combined with the drill hole logging data and other geophysical data, including ZTEM survey, enable the 3D-modeling of the Outokumpu subsurface structures.
Keywords: 3D modeling; Acoustic impedance; Infill drilling; Lithology; Mica; Mineral exploration; Rock drills; Seismology; Signal to noise ratio; Sulfur compounds; Wave propagation; Constant velocities; High quality data; Seismic processing; Seismic reflection profiles; Seismic reflections; Seismic velocities; Static correction; Subsurface structures; Seismic waves

Alkenone distribution in Lake Van sediment over the last 270ka: Influence of temperature and haptophyte species composition - Randlett, M.-E.; Coolen, M.J.L.; Stockhecke, M.; Pickarski, N.; Litt, T.; Balkema, C.; Kwiecien, O.; Tomonaga, Y.; Wehrli, B.; Schubert, C.J. (Quaternary Science Reviews, 2014)
Fossil long-chain alkenones have been used for several decades to reconstruct past ocean surface water temperatures and gained recent interest as a paleotemperature proxy for continental lake settings. However, factors besides temperature can affect alkenone distributions in haptophyte algae, and alkenone compositions can differ between haptophyte species. Alkenone-biosynthesizing haptophyte algae are genetically much more diverse in lakes than in the marine realm, and species-level variations in alkenone compositions could have implications for alkenone paleothermometry. Here, we performed a paired analysis of alkenone distributions and haptophyte species compositions using ancient DNA in up to 270ka-old sediments of Lake Van in Turkey to reveal a possible species-effect on fossil alkenone distributions and paleotemperature estimates. The same predominant haptophyte in Lake Van today prevailed also since the last 100ka. However, a calibration of alkenone paleotemperature especially in the oldest analyzed intervals is complicated due to a more complex haptophyte species composition predominated by a haptophyte (LVHap_6), which is phylogenetically different from sequences recovered from currently existing lakes including Lake Van and from haptophyte species existing in culture. The predominance of LVHap_6 coincided with the presence of alkenone MeC38:3 and relatively high MeC37:3/4 (2.4) and MeC38:4/5 ratios (3.0). Uk37 index values in the sediment core over the last 270ka reflect relative changes in past temperature and are additionally linked to haptophyte species composition. A sustained period of high salinity, as indicated by pore-water salinity measurements, could potentially have triggered the succession of haptophytes as sources of alkenones in Lake Van. © 2014 The Authors.
cited By 59
Keywords: Algae; Biomarkers; Lakes; Paleolimnology; Salinity measurement; Sediments; Alkenones; Haptophyte species; Lake vans; Long chain alkenones; Paleoproxy; Paleotemperature proxy; Paleotemperatures; Species composition; Population distribution; alga; alkenone; biomarker; fossil record; lacustrine deposit; paleolimnology; paleotemperature; reconstruction; spatial distribution; temperature effect; Lake Van; Turkey

Design and development of the discharge system of IDDP-1 - Ingason, K.; Kristj'ansson, V.; Einarsson, K. (Geothermics, 2014)
The initial discharge of IDDP-1 took place in March 2010 and the well was discharged intermittently until July 2012. In the beginning a mixture of steam and water flowed from the well but soon the fluid became superheated and enthalpy gradually increased, approaching 3200kJ/kg. The flow rate from the well was up to 50kg/s. The design condition at well head turned out to be challenging due to high pressure, temperature, corrosion and erosion. Valves, rated for higher pressure and temperature, failed during operation. Five different designs of discharge systems were installed. The well had to be quenched when the master valves failed. Plans for its future are still being evaluated.
Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma
Keywords: Krafla; IDDP-1; Geothermal well head; Geothermal well discharge; Geothermal superheated steam; Corrosion; Erosion

Incursion of meteoric waters into the ductile regime in an active orogen - Menzies, C.D.; Teagle, D.A.H.; Craw, D.; Cox, S.C.; Boyce, A.J.; Barrie, C.D.; Roberts, S. (Earth and Planetary Science Letters, 2014)
Rapid tectonic uplift on the Alpine Fault, New Zealand, elevates topography, regional geothermal gradients, and the depth to the brittle ductile transition, and drives fluid flow that influences deformation and mineralisation within the orogen. Oxygen and hydrogen stable isotopes, fluid inclusion and Fourier Transform Infrared (FT-IR) analyses of quartz from veins which formed at a wide range of depths, temperatures and deformation regimes identify fluid sources and the depth of penetration of meteoric waters. Most veins formed under brittle conditions and with isotope signatures (δ18OH2O = -9.0 to +8.7‰VSMOW and δD = - 73 to - 45‰VSMOW) indicative of progressively rock-equilibrated meteoric waters. Two generations of quartz veins that post-date mylonitic foliation but endured further ductile deformation, and hence formation below the brittle to ductile transition zone ( >6-8 km depth), preserve included hydrothermal fluids with δD values between -84 and -52‰, indicating formation from meteoric waters. FT-IR analyses of these veins show no evidence of structural hydrogen release, precluding this as a source of low δD values. In contrast, the oxygen isotopic signal of these fluids has almost completely equilibrated with host rocks (δ18OH2O = +2.3 to +8.7‰). These data show that meteoric waters dominate the fluid phase in the rocks, and there is no stable isotopic requirement for the presence of metamorphic fluids during the precipitation of ductilely deformed quartz veins. This requires the penetration during orogenesis of meteoric waters into and possibly below the brittle to ductile transition zone. © 2014 The Authors.
cited By 79
Keywords: Digital storage; Flow of fluids; Hydrogen; Isotopes; Metamorphic rocks; Mineralogy; Oxygen; Quartz; Alpine Faults; Fluid inclusion; Meteoric waters; Southern Alps; Stable isotopes; Deformation

ICDP Deep drilling and geophysical exploration of the Bushveld Complex, South Africa - Webb*, Susan J; Ashwal, Lewis D; Trumbull, Robert; Veksler, Ilya (SEG Technical Program Expanded Abstracts 2014, 2014)

Iceland Deep Drilling Project: The first well, IDDP-1, drilled into magma - Elders, Wilfred A.; Friðleifsson, Guðmundur Ó.; P'alsson, Bjarni (Geothermics, 2014)
Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma

IDDP–The chemistry of the IDDP-01 well fluids in relation to the geochemistry of the Krafla geothermal system - 'Armannsson, Halld'or; Fridriksson, Thr'ainn; Gudfinnsson, Gudmundur H.; Ólafsson, Magn'us; Óskarsson, Finnbogi; Thorbj{ornsson, Dadi (Geothermics, 2014)
The Leirbotnar field, where IDDP-01 is situated consists of an upper liquid dominated zone to 1000 –1400m depth, 190 –220°C, sulphate major anion, and a lower two phase zone, 300°C chloride main anion. The IDDP-01 fluid is dry steam, local origin, pH 3. The major anion is chloride (20 –166mg/kg), probably of magmatic origin. The major metallic cations, Fe (5 –100mg/kg), Cr (0 –6mg/kg), Ni (0 –5mg/kg) and Mn (0.1 –0.8mg/kg) seem to be derived from the well casing and sampling equipment. The gas content is low (about 0.1%) and the gas is apparently not directly emitted from magma.
Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma
Keywords: IDDP; Krafla; Geochemistry; Acid well fluids

Impact of Lake-Level and Climate Changes on Microbial Communities in a Terrestrial Permafrost Sequence of the El'gygytgyn Crater, Far East Russian Arctic - Bischoff, J.; Mangelsdorf, K.; Schwamborn, G.; Wagner, D. (Permafrost and Periglacial Processes, 2014)
Microbial permafrost communities play an important role in carbon cycling and greenhouse gas fluxes. Despite the importance of these processes, there is a lack of knowledge about how environmental and climatic changes affect the abundance and composition of microorganisms. Here, we investigated the changing distribution of permafrost microorganisms in response to climate and lake-level changes. The permafrost core was drilled at the near shore of Lake El'gygytgyn, Far East Russian Arctic, and a combined microbiological and lipid biomarker approach was applied. The lower part of the permafrost core, deposited under subaquatic conditions, contains only small amounts of microbial signals; total organic carbon (TOC) content is sparse. After exposure of the site to subaerial conditions during the Allerød, the abundance of Bacteria and Archaea started to increase and the lake-level change is especially evidenced by the relative proportion of archaeal biomarkers. This increase is supported by rising bacterial and archaeal 16S ribosomal ribonucleic acid (rRNA) gene copy numbers and significant amounts of TOC during the late Allerød. After a small decrease during the colder Younger Dryas, the TOC content and the microbial signals strongly increase during the Holocene, presumably stimulated by pedogenesis. The occurrence of intact phospholipids indicates the presence of living microorganisms in these deposits. Our data suggest that methane formation is mainly expected for the subaerial interval, especially the Holocene where methanogens were identified by fingerprinting. This study emphasises the role of the uppermost permafrost deposits as a hotspot of carbon cycling in arctic environments, especially in the light of expected future global warming. © 2014 John Wiley & Sons, Ltd.
cited By 9
Keywords: abundance; arctic environment; biomarker; carbon cycle; climate change; Holocene; lake level; methane; microbial community; microbiology; microorganism; pedogenesis; permafrost; phospholipid; RNA; total organic carbon; Younger Dryas; Arctic; Chukchi; Elgygytgyn Lake; Russian Federation; Archaea; Bacteria (microorganisms)

Impact of volcanism on the evolution of Lake Van (eastern Anatolia) III: Periodic (Nemrut) vs. episodic (S{uphan) explosive eruptions and climate forcing reflected in a tephra gap between ca. 14 ka and ca. 30 ka - Schmincke, H.-U.; Sumita, M. (Journal of Volcanology and Geothermal Research, 2014)
Fifteen Lateglacial to Holocene rhyolitic, dominantly primary tephra layers piston-cored and drilled (ICDP Paleovan drilling project) in western Lake Van (eastern Anatolia, Turkey) were precisely correlated to either of the two adjacent and active large volcanoes Nemrut and S{uphan based on shard textures, mineralogy and mineral and glass compositions. The young peralkaline (comenditic to pantelleritic) primary rhyolitic Nemrut tephras are characterized by anorthoclase, hedenbergitic to augitic clinopyroxene, fayalitic olivine, minor quartz, and rare accessory chevkinite and zircon. Phenocrysts in subalkaline primary rhyolitic S{uphan tephras are chiefly oligoclase-labradorite, with minor K-rich sanidine in some, biotite, amphibole, hypersthene, rare augitic clinopyroxene, relatively common allanite and rare zircon.Two contrasting explosive eruptive modes are distinguished from each other: episodic (S{uphan) and periodic (Nemrut). The Lateglacial S{uphan tephra swarm covers a short time interval of ca. 338. years between ca. 13,078. vy BP and 12,740. vy BP, eruptions having occurred statistically every ca. 42. years with especially short intervals between V-11 (reworked) and V-14. Causes for the strongly episodic S{uphan explosive behavior might include seismic triggering of a volcano-magma system unable to erupt explosively without the benefit of external triggering, as reflected in pervasive faulting preceding the S{uphan tephra swarm. Seismic triggering may have caused the rise of more mafic (trachyandesitic) parent magma, heating near-surface pockets of highly evolved magma - that might have formed silicic domes during this stage of volcano evolution - resulting in ascent and finally explosive fragmentation of magma essentially by external factors, probably significantly enhanced by magma-water/ice interaction.Explosive eruptions of the Nemrut volcano system, interpreted to be underlain by a large fractionating magma reservoir, follow a more periodic mode of (a) long-term relatively constant supply of parent magma, (b) evolution by low pressure crystal fractionation resulting in sporadic relatively low-volume eruption of trachytic and minor rhyolitic magmas, (c) evolution of a large magma reservoir to the point of highly explosive large-volume peralkaline rhyolitic Plinian eruptions at temporal intervals of ca. 20-40. ky, some accompanied by ignimbrites and inferred caldera collapse.A striking tephra gap between ca. 14. ka and ca. 30. ka, i.e. during glacial climate conditions, is postulated to be due to climate-forcing via lithosphere unloading following deglaciation. © 2014 Elsevier B.V.
cited By 26
Keywords: Explosive activity; Lake vans; Tephra swarm; Tephrostratigraphy; Volcanic activities; climate forcing; earthquake trigger; explosive volcanism; Holocene; late glacial; stratigraphy; tephra; volcanic eruption; Anatolia; Bitlis; Lake Van; Nemrut; Turkey

In situ frictional properties of San Andreas Fault gouge at SAFOD - Coble, C.G.; French, M.E.; Chester, F.M.; Chester, J.S.; Kitajima, H. (Geophysical Journal International, 2014)
Along the central segment of the San Andreas Fault (SAF) near Parkfield, California, displacement occurs by a combination of aseismic creep and micro-earthquake slip. To constrain the strength and parametrize a constitutive relation for the creeping behaviour of the central segment of the SAF, we conducted friction experiments on clay-rich gouge retrieved by coring the Central Deforming Zone (CDZ) of the SAF at 2.7 km vertical depth. The gouge was flaked rather than powdered to preserve the natural scaly microfabric, and formed into 2-mm-thick layers that were sheared using a triaxial deformation apparatus. Experiments were conducted at in situ effective normal stress (100 MPa), pore pressure (25 MPa) and temperature (80-120 °C) conditions using brine pore fluid with the ionic composition of the in situ formation fluid. Velocity-stepping (0.006-0.6 μm s-1) and temperature-stepping experiments were conducted on brine-saturated gouge, and slide-hold-slide experiments were conducted on brine-saturated and room-dry gouge. Results are used to quantify the effects of rate, state, temperature and pore fluid on the strength of the CDZ gouge. We find that the gouge is extremely weak (μ < 0.13) and rate-strengthening, consistent with findings of previous studies on the CDZ gouge. We also find that, in a rate and state friction framework, slip history has a negligible effect on strength (b ≈ 0) under both saturated and dry conditions. The CDZ gouge is temperature-weakening from 80 to 120 °C and weakens 17 per cent when saturated with brine compared to room-dry conditions. Employing the laboratory-derived friction constitutive parameters, and including the temperature weakening and the strain-rate strengthening effects, we determine an approximate in situ friction coefficient of μ ≈ 0.11. For μ ≈ 0.11, aseismic creep under normal pore fluid conditions is permitted for angles up to 79° between the maximum horizontal stress and the plane of the SAF, consistent with nearby stress orientation measurements., Copy; The Authors 2014.
cited By 22
Keywords: Creep; Geomechanics; Strain rate; Strike-slip faults; Constitutive parameters; Constitutive relations; Creep and deformations; Effective normal stress; Fault zone; Friction coefficients; Rate and state friction; Strain-rate strengthening effects; Friction; creep; deformation; displacement; fault gouge; fault zone; friction; geomechanics; rheology; San Andreas Fault; California; San Andreas; United States

Inorganic geochemistry data from Lake El'gygytgyn sediments: Marine isotope stages 6-11 - Minyuk, P.S.; Borkhodoev, V.Y.; Wennrich, V. (Climate of the Past, 2014)
Geochemical analyses were performed on sediments recovered by deep drilling at Lake El'gygytgyn in central Chukotka, northeastern Russia (67 30' N; 172 05' E). Major and rare element concentrations were determined using X-ray fluorescence spectroscopy (XRF) on the < 250 μm fraction from 617 samples dated to ca. 440 and 125 ka, which approximates marine isotope stages (MIS) 11 to 6. The inorganic geochemistry indicates significant variations in elemental composition between glaciations and interglaciations. Interglacial sediments are characterized by high contents of SiO2, Na2O, CaO, K 2O, and Sr and are depleted in Al2O3, Fe2O 3, TiO2, and MgO. An extreme SiO2 enrichment during MIS 11.3 and 9.3 was caused by an enhanced flux of biogenic silica (BSi). The geochemical structure of MIS 11 shows similar characteristics as seen in MIS 11 records from Lake Baikal (southeastern Siberia) and Antarctic ice cores, thereby arguing for the influence of global forcings on these records. High sediment content of TiO2, Fe2O3, MgO, Al 2O3, LOI, Ni, Cr, and Zr typifies glacial stages, with the most marked increases during MIS 7.4 and 6.6. Reducing conditions during glacial times are indicated by peaks in the Fe2O3 content and coinciding low Fe2O3/MnO ratios. This conclusion also is supported by P2O5 and MnO enrichment, indicating an increased abundance of authigenic, fine-grained vivianite. Elemental ratios (CIA, CIW, PIA, and Rb/Sr) indicate that glacial sediments are depleted in mobile elements, like Na, Ca, K and Sr. This depletion was caused by changes in the sedimentation regime and thus reflects environmental changes. © 2014 Author(s).
cited By 42
Keywords: chemical composition; concentration (composition); data set; drilling; environmental change; glacial deposit; glaciation; interglacial; lacustrine deposit; marine isotope stage; sediment chemistry; sedimentation; Chukchi; Elgygytgyn Lake; Lake Baikal; Russian Federation; Siberia

High temperature metamorphism in the conductive boundary layer adjacent to a rhyolite intrusion in the Krafla geothermal system, Iceland - Schiffman, Peter; Zierenberg, Robert A.; Mortensen, Anette K.; Friðleifsson, Guðmundur Ó.; Elders, Wilfred A. (Geothermics, 2014)
A rhyolite magma body within the Krafla geothermal system that was encountered at a depth of 2.1km during drilling of the IDDP-1 borehole is producing high temperature metamorphism within a conductive boundary layer (CBL) in adjacent host rocks. Cuttings recovered during drilling within a few meters of the intrusive contact in IDDP-1 are mainly comprised of granoblastic hornfelses, the rock type which confirms the presence of the CBL at the base of the IDDP-1 bore hole. The two pyroxenes in these hornfelses record temperatures that are in the range of 800 –950°C. The minimum heat flow across the CBL is 23Wm−2. Country rocks at distances beyond 30m of the intrusive contact are essentially unaltered, implying that they have been emplaced very recently and/or as yet unaffected by hydrothermal fluid flow.
Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma
Keywords: Krafla; IDDP-1; Geothermal; Contact metamorphism

Inorganic geochemistry data from Lake El'gygytgyn sediments: marine isotope stages 6 –11 - Minyuk, P. S.; Borkhodoev, V. Y.; Wennrich, V. (Climate of the Past, 2014)

Insights into early Earth from the Pt-Re-Os isotope and highly siderophile element abundance systematics of Barberton komatiites - Puchtel, Igor S.; Walker, Richard J.; Touboul, Mathieu; Nisbet, Euan G.; Byerly, Gary R. (Geochimica et Cosmochimica Acta, 2014)

International Continental Scientific Drilling Programme Workshop on the Bushveld Complex - Roelofse, F (Geobulletin, 2014)

Intra-continental earthquake swarms in West-Bohemia and Vogtland: A review - Fischer, T.; Hor'alek, J.; Hrubcov'a, P.; Vavryčuk, V.; Br{auer, K.; K{ampf, H. (Tectonophysics, 2014)
Earthquake swarms and high CO2 flow of mantle origin are the characteristic features of West Bohemia/Vogtland (Central Europe). At present, the highest concentration of earthquake activity and CO2 degassing occurs in the area of the Cheb Basin at the intersection of the Eger Rift and Regensburg-Leipzig-Rostock Zone with three Quaternary active volcanoes. We review about 140 studies on structure, tectonics, volcanism, seismicity, earthquake source, triggering mechanisms, and gas-isotope geochemistry focused on the earthquake swarms from this area with the aim to build a complex image of the ongoing processes and find a possible link between activity of the mantle-derived fluids and the earthquake swarms. The so far unpublished data on the 2011 swarm and little known data on the 1824 swarm are presented, as well, showing that earthquake swarms activate a complex fault system and display long-term migration that differs from the occurrence of CO2 escapes. The activity of individual swarms is consistent with models involving high-pressure fluids; the isotopic signature of the rising gas proves its origin at depths below the hypocenters. We show that the earthquake swarms and degassing of CO2 of magmatic origin represent common result of the geodynamic activity of the area. Nevertheless, current knowledge does not preclude processes other than fluid-induced failure in triggering swarm seismicity. © 2013 Elsevier B.V.
Keywords: Bohemia; Cheb Basin; Czech Republic; Germany; Karlovarsky; Vogtland; Carbon dioxide; Degassing; Exploratory geochemistry; Fluids; Geodynamics; Isotopes; Complex fault system; Earthquake swarms; Earthquake triggering; High-pressure fluids; Isotopic signatures; Triggering mechanism; Vogtland; West Bohemia; carbon dioxide; degassing; earthquake hypocenter; earthquake swarm; earthquake trigger; geochemistry; geodynamics; seismic source; seismicity; seismotectonics; trigger mechanism; volcanism; Earthquakes

Invaders versus endemics: alien gastropod species in ancient Lake Ohrid - Albrecht, Christian; F{oller, Kirstin; Clewing, Catharina; Hauffe, Torsten; Wilke, Thomas (Hydrobiologia, 2014)
Species invasions into ancient lakes are an important but little understood phenomenon. At ancient Lake Ohrid, a systematic assessment of invasive mollusc species using morphological and genetic data was conducted from 2003 to 2012. Two globally invasive gastropod species, Physa acuta and Ferrissia fragilis, have recently been discovered at 4 out of 386 sites. These sites are anthropogenically impacted. The invasive species co-occur with endemics. Phylogenetic analyses of populations from native and invaded ranges of both species confirmed their identities and provided insights into their invasion histories. Accordingly, P. acuta is genetically more diverse than F. fragilis. Both species are currently present in a considerable number of lakes on the Balkan Peninsula. Possible future trends in Lake Ohrid and the Balkans are discussed and further spread of both species is likely. Given the ongoing environmental change in Lake Ohrid, the number of observations of non-indigenous or other widespread species will probably rise in the coming years and such species and their impact on native species should be carefully monitored. Moreover, ancient lakes with recurrent invasions of alien species might serve as interesting model systems for the study of important topics of invasion biology. © 2013, Springer Science+Business Media Dordrecht.
Keywords: Lake Ohrid; Ferrissia fragilis; Ferrissia wautieri; Gastropoda; Physa acuta; coexistence; endemism; gastropod; identification key; introduced species; invasive species; lake ecosystem; phylogenetics; species diversity

Displacement and dynamic weakening processes in smectite-rich gouge from the Central Deforming Zone of the San Andreas Fault - French, M.E.; Kitajima, H.; Chester, J.S.; Chester, F.M.; Hirose, T. (Journal of Geophysical Research: Solid Earth, 2014)
The strength of clay-rich gouge from the Central Deforming Zone (CDZ) of the San Andreas Fault (SAF) was measured using a high-speed rotary shear apparatus to evaluate the potential for unstable slip along the creeping segment of the SAF. Wet and dry gouge was sheared at 0.1-1.3 m/s, 0.5-1.5 MPa normal stress, and 1-20 m displacement. CDZ gouge is weaker wet than dry and exhibits displacement strengthening to peak friction followed by weakening to steady state strength that decreases with increasing velocity. A clay foliation (Unit 2) develops from the initial microstructure (Unit 1) during the first 1.5 m of slip coincident with increasing strength. Subsequent weakening occurs during shear within Unit 2, and subsequently with development of a localized foliated slip zone (Unit 4) and fluidized material (Unit 3). Displacement and dynamic weakening result from slip along clay foliation assisted by shear-heating pressurization of pore fluid in wet gouge and additional grain-size reduction and possible clay dehydration in dry gouge. Peak strength is proportional to normal stress, but steady state strength is insensitive to normal stress probably because pore pressure approaches the normal stress. As such, CDZ gouge is weak at coseismic rates relative to interseismic creep strength. The potential for sustaining rupture propagation into the CDZ from an adjacent seismic segment is sensitive to the relationship used to extrapolate the critical weakening displacement from experimental to in situ conditions. Rupture propagation from a microseismic patch within the CDZ is unlikely, but sustained propagation from a large earthquake (e.g., Parkfield event) may be possible. ©2014. American Geophysical Union. All Rights Reserved.
cited By 32
Keywords: clay; coseismic process; dehydration; displacement; fault gouge; grain size; microstructure; pore pressure; San Andreas Fault; smectite; stress analysis; California; San Andreas; United States

Hydraulic and acoustic properties of the active Alpine Fault, New Zealand: Laboratory measurements on DFDP-1 drill core - Carpenter, B.M.; Kitajima, H.; Sutherland, R.; Townend, J.; Toy, V.G.; Saffer, D.M. (Earth and Planetary Science Letters, 2014)
We report on laboratory measurements of permeability and elastic wavespeed for a suite of samples obtained by drilling across the active Alpine Fault on the South Island of New Zealand, as part of the first phase of the Deep Fault Drilling Project (DFDP-1). We find that clay-rich cataclasite and principal slip zone (PSZ) samples exhibit low permeabilities (≤10-18m2), and that the permeability of hanging-wall cataclasites increases (from c. 10-18 m2 to 10-15 m2) with distance from the fault. Additionally, the PSZ exhibits a markedly lower P-wave velocity and Young's modulus relative to the wall rocks. Our laboratory data are in good agreement with in situ wireline logging measurements and are consistent with the identification of an alteration zone surrounding the PSZ defined by observations of core samples. The properties of this zone and the low permeability of the PSZ likely govern transient hydrologic processes during earthquake slip, including thermal pressurization and dilatancy strengthening. © 2013 Elsevier B.V.
cited By 48
Keywords: Alpine Faults; Drilling projects; Fault mechanics; Hydrologic process; Laboratory measurements; Low permeability; Petrophysics; Thermal pressurization; Elastic moduli; Mechanical permeability; Research laboratories; Wave propagation; Acoustic properties; acoustic property; active fault; core analysis; drilling; fault zone; hydraulic property; permeability; well logging; Alpine Fault Zone; New Zealand; South Island

Influence of Methanogenic Populations in Holocene Lacustrine Sediments Revealed by Clone Libraries and Fatty Acid Biogeochemistry - Vuillemin, A.; Ariztegui, D.; Nobbe, G.; Schubert, C.J. (Geomicrobiology Journal, 2014)

High temperature instruments and methods developed for supercritical geothermal reservoir characterisation and exploitation–The HiTI project - 'Asmundsson, Ragnar; Sanjuan, Bernard; Henninges, Jan; Deltombe, Jean-Luc; Halladay, Nigel; Lebert, François; Gadalia, Alain; Millot, Romain; Gibert, Benoit; Violay, Marie; Reinsch, Thomas; Naisse, Jean-Marc; et al. (Geothermics, 2014)
During the early years of the Iceland Deep Drilling Project (IDDP), development of three distinctive technological and scientific approaches were formalised and then carried out until 2010 within a European funded project called HiTI (high temperature instruments for supercritical geothermal reservoir characterisation and exploitation). These approaches were: (1) development of several downhole instruments allowing them to function up to 300°C and 400°C, (2) identification of two new Na/Li cation ratio geothermometric relationships valid at very high temperature, (3) tracer testing with high temperature tolerant organic isomers and finally and (4) basalt rock deformation and petrophysical properties laboratory investigations at high temperature and pressure conditions.
Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma
Keywords: High temperature; Supercritical; Downhole; Geothermometers; Televiewer; Basalt experiments

Eustasy, its controlling factors, and the limno-eustatic hypothesis - Concepts inspired by Eduard Suess - Wagreich, M.; Lein, R.; Sames, B. (Austrian Journal of Earth Sciences, 2014)
For many years Eduard Suess dealt with the phenomenon of displaced shorelines and the search for explanations for their genesis and the controlling factors. In the year 1888 Suess introduced the term eustatic movements referring to the global synchroneity of marker events in marine successions of the Earth history. Since the times of Suess, rapid scientific progress has considerably widened our understanding of the processes involved in changing sea levels. Eustasy now describes global sea-level changes that play a major role in controlling the development, structure and distribution of marine sedimentary successions. Relative (regional and local) and global (eustatic) sea-level fluctuations are controlled by a variety of endogenic and exogenic processes. Mantle convection and resulting gravity anomalies and tectonism, and climate changes are the main drivers, and apply at different temporal and spatial scales. The long-term sea-level record, i.e. 1st to 2nd order cycles and stratigraphic sequences, occurring over millions to tens of millions of years, is mainly controlled by the internal dynamic history of the Earth, e.g., the changing rates of ocean crust production. Short-term eustatic sea-level changes during ice house phases of Earth's climate are clearly controlled by waxing and waning of continental ice sheets. However, significant short-term, i.e. 10s kyr to a few Myr (3rd to 4th order cycles), sea-level changes during greenhouse episodes of Earth history are still enigmatic. Such cycles are often explained by the presence of ephemeral ice sheets even during the hottest greenhouse phases (hothouse periods) of the Phanerozoic climate history such as the mid-Cretaceous. We argue that the effect of groundwater storage and release on sea-level change, particularly important during ice-free greenhousephases, has been and is widely underestimated in its order of magnitude. It is considered to constitute a water volume that is about equivalent to today's ice volume, thus corresponding to a potential sea-level change of up to ca. 50 m applying isostatic adjustment. Groundwater storage, including both freshwater and saline pore waters, strongly exceeds lake and river storage capacities. We introduce the term limno-eustatic to describe the effect of water volumes that are bound to groundwater and lake storage on sea-level fluctuations and cycles during major greenhouse phases of Earth history. Based on these terms the dimension of purely ice-driven glacio-eustatic processes can be better differentiated. The limno-eustatic hypothesis may be testable given high-resolution stratigraphic correlations between marine and continental lake archives during supposed ice-free periods of Earth history. Lake-level and sea-level fluctuations should be in an out of phase relation, i.e. a major marine sea-level lowstand should correspond to a lake-level highstand, and vice versa. Preliminary tests using selected stratigraphic levels of the Late Cretaceous record of the long-lived lacustrine Songliao basin in China indicate such an outof- phase relation, and thus support the limno-eustatic hypothesis as a mechanism to explain significant short-term sea-level fluctuations during greenhouse climate phases.
cited By 68
Keywords: Cretaceous; eustacy; geodynamics; geological record; isostasy; limnology; mantle convection; paleoclimate; sedimentary structure; sequence stratigraphy; spatiotemporal analysis; stratigraphic correlation; tectonic setting; China; Songliao Basin

Distinct lake level lowstand in Lake Prespa (SE Europe) at the time of the 74 (75) ka Toba eruption - Wagner, B.; Leng, M.J.; Wilke, T.; B{ohm, A.; Panagiotopoulos, K.; Vogel, H.; Lacey, J.H.; Zanchetta, G.; Sulpizio, R. (Climate of the Past, 2014)
The 74 (75) ka Toba eruption in Sumatra, Indonesia, is considered to be one of the largest volcanic events during the Quaternary. Tephra from the Toba eruption has been found in many terrestrial and marine sedimentary deposits, and acidity peaks related to the eruption have been used to synchronize ice core records from Greenland and Antarctica. Seismic profiles and sedimentological data from Lake Prespa on the Balkan Peninsula, SE Europe, indicate a lake level lowstand at 73.6 ± 7.7 ka based on ESR dating of shells. Tephrostratigraphy, radiocarbon dating and tuning of the total organic carbon content with the NGRIP isotope record, corroborate that the lake level lowstand was a short-term event superimposed on the general cooling trend at the end of MIS 5, most likely at the onset of the Greenland Stadial GS-20. Acknowledging that tectonic events or karst processes could have triggered this lake level lowstand, the chronological correspondence between the lowstand and the Toba eruption is intriguing. Therefore a Toba-driven short-term shift to aridity in the Balkan region, leading to lake level changes and triggering spatial expansion events in one of the lake's most abundant benthic species, the carino mussel Dreissena presbensis, cannot be excluded. © Author(s) 2014.
Keywords: Arctic; Greater Sunda Islands; Greenland; Indonesia; Lake Mikri Prespa; Sumatra; Sunda Isles; Dreissena; benthos; bivalve; data set; dating method; ice core; karst; Quaternary; radiocarbon dating; sedimentology; tephrochronology; volcanic eruption

Glacial forcing of central Indonesian hydroclimate since 60,000 y B.P. - Russell, James M.; Vogel, Hendrik; Konecky, Bronwen L.; Bijaksana, Satria; Huang, Yongsong; Wattrus, Nigel; Costa, Kassandra; King, John W. (Proceedings of the National Academy of Sciences of the United States of America, 2014)
The Indo-Pacific warm pool houses the largest zone of deep atmospheric convection on Earth and plays a critical role in global climate variations. Despite the region's importance, changes in Indo-Pacific hydroclimate on orbital timescales remain poorly constrained. Here we present high-resolution geochemical records of surface runoff and vegetation from sediment cores fromLake Towuti, on the island of Sulawesi in central Indonesia, that continuously span the past 60,000 y.We show that wet conditions and rainforest ecosystems on Sulawesi present during marine isotope stage 3 (MIS3) and the Holocene were interrupted by severe drying between ∼33,000 and 16,000 y B.P. when Northern Hemisphere ice sheets expanded and global temperatures cooled. Our record reveals little direct influence of precessional orbital forcing on regional climate, and the similarity between MIS3 and Holocene climates observed in Lake Towuti suggests that exposure of the Sunda Shelf has a weaker influence on regional hydroclimate and terrestrial ecosystems than suggested previously. We infer that hydrological variability in this part of Indonesia varies strongly in response to high-latitude climate forcing, likely through reorganizations of the monsoons and the position of the intertropical convergence zone. These findings suggest an important role for the tropical western Pacific in amplifying glacial-interglacial climate variability.
Keywords: runoff; titanium; article; canopy; climate; climate change; ecosystem; geochemistry; glacial interglacial variability; glacial period; Holocene; hydroclimate; hydrology; ice sheet; Indonesia; interglacial; lake; marine isotope stage 3; Northern Hemisphere; paleoclimate; precipitation; priority journal; sea surface temperature; sediment; stratigraphy; tropical rain forest; vegetation

Diversity and spatial distribution of extant freshwater ostracodes (crustacea) in ancient Lake Ohrid (Macedonia/Albania) - Lorenschat, Julia; Pe´rez, Liseth; Correa-Metrio, Alexander; Brenner, Mark; Bramann, Ullrich; Schwalb, Antje (Diversity, 2014)
We carried out an intensive sampling survey in ancient Lake Ohrid (Macedonia/Albania), covering all seasons, to determine total species number, relative species abundances and spatial distribution of Ostracoda. We identified 32 living species that belong to seven families (Candonidae, Ilyocyprididae, Cyprididae, Leptocytheridae, Limnocytheridae, Cytherideidae, and Darwinulidae) and 15 genera (Candona, Fabaeformiscandona, Candonopsis, Cypria, Cyclocypris, Ilyocypris, Eucypris, Prionocypris, Bradleystrandesia, Herpetocypris, Dolerocypris, Amnicythere, Paralimnocythere, Cytherissa, and Darwinula). Six additional species were identified from empty carapaces and valves. Dominant families in Lake Ohrid were Candonidae and Limnocytheridae, representing 53% and 16% of all species, respectively. Prevalence of species flocks in these two families confirms the young ancient status of the lake. Amnicythere displays a preference for oligo-haline to meso-haline waters, but some species are found in saline environments, which suggests Lake Ohrid has a marine history. Recent studies, however, indicate fluvial/glaciofluvial deposition at the onset of Lake Ohrid sedimentation. Candona is the most diverse genus in Lake Ohrid, represented by 12 living species. Paralimnocythere is represented by five living species and all other genera are represented by one or two species. Reports of Candona bimucronata, Ilyocypris bradyi, Eucypris virens, Eucypris sp., Prionocypris zenkeri, Bradleystrandesia reticulate, Herpetocypris sp. 2, and Dolerocypris sinensis are firsts for this lake. Living ostracodes were collected at the maximum water depth (280 m) in the lake (Candona hadzistei, C. marginatoides, C. media, C. ovalis, C. vidua, Fabaeformiscandona krstici, Cypria lacustris, C. obliqua and Amnicythere karamani). Cypria lacustris was overall the most abundant species and Cypria obliqua displayed the highest abundance at 280 m water depth. Principal environmental variables that influence ostracode distributions in Lake Ohrid are water depth and conductivity. In general, species richness, diversity and evenness were greater in waters <60 m deep, with highest values often found in the littoral zone, at depths <30 m. Candonids, however, displayed highest diversity in the sublittoral (30-50 m) and profundal (50-280 m) zones. The most frequent species encountered are taxa endemic to the lake (14 living species), which have a wide depth range (≤280 m), and display higher abundance with greater water depth. Non-endemic species were rare, limited to water depths <50 m, and were found mainly in the north part of the lake where anthropogenic pressure is high. Several cosmopolitan species were encountered for the first time, which suggests that these widespread species are new arrivals that may replace endemics as human impacts increase. © 2014 by the authors.
Keywords: Albania; Greece; Lake Ohrid; Macedonia [Greece]; Crustacea; Ostracoda; anthropogenic effect; biodiversity; endemism; human activity; intertidal environment; ostracod; spatial distribution; species diversity; species evenness; species richness; taxonomy; water depth

Drilling into magma and the implications of the Iceland Deep Drilling Project (IDDP) for high-temperature geothermal systems worldwide - Elders, W.A.; Friðleifsson, G.Ó.; Albertsson, A. (Geothermics, 2014)
Drilling deeper in high-temperature geothermal systems by the IDDP is aimed at increasing the power output of shallower high-temperature geothermal fields by an order of magnitude without increasing their environmental footprints. The main thrust of the IDDP is to develop deep supercritical systems, but an unexpected encounter with a shallow body of magma demonstrated that very high power outputs are also possible from the contact zone of an intrusion. In the future it may be feasible to produce energy directly from magma. Favorable environments to implement these concepts are likely worldwide wherever active volcanoes and young volcanic rocks occur.
Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma
Keywords: Magma energy; Supercritical geothermal energy; Krafla Iceland

Drilling into the track of the yellowstone hot spot - Shervais, J.W.; Evans, J.P.; Christiansen, E.H.; Prokopenko, A. (Eos, 2014)
The Yellowstone supervolcano erupted roughly 640,000 years ago, covering much of North America in a thick coat of ash. Material ejected from the volcano devastated the surrounding area, and particles injected into the atmosphere changed the Earth's climate. Over the past 18 million years the Yellowstone hot spot has powered a series of similar eruptions. In southern Idaho, the 640-kilometer-long Snake River Plain traces the path of the Yellowstone hot spot over this period. ©2014. American Geophysical Union. All Rights Reserved.
cited By 6
Keywords: ash; climate change; drilling; hot spot; mantle plume; volcanic eruption; volcanic ash; Idaho; Snake River Plain; United States; Yellowstone Volcanic Plateau

Dynamics of the last four glacial terminations recorded in Lake Van, Turkey - Kwiecien, O.; Stockhecke, M.; Pickarski, N.; Heumann, G.; Litt, T.; Sturm, M.; Anselmetti, F.; Kipfer, R.; Haug, G.H. (Quaternary Science Reviews, 2014)
A well-dated suite of Lake Van climate-proxy data covering the last 360ka documents environmental changes over 4 glacial/interglacial cycles in Eastern Anatolia, Turkey. The picture of cold and dry glacials and warm and wet interglacials emerging from pollen, organic carbon, authigenic carbonate content, elemental profiling by XRF and lithological analyses is inconsistent with classical interpretation of oxygen isotopic composition of carbonates pointing to a more complex pattern in Lake Van region. Detailed analysis of glacial terminations allows for the constraining of a depositional model explaining different patterns observed in all the proxies. We hypothesize that variations in relative contribution of rainfall, snowmelt and glacier meltwater recharging the basin have a very important role for all sedimentary processes in Lake Van. Lake level of glacial Lake Van, predominantly fed by snowmelt, was low, the water column was oxic, and carbonates precipitating in the epilimnion recorded the light isotopic signature of inflow. During terminations, increasing rainfall and significant supply of mountain glaciers' meltwater contributed to lake level rise. Increased rainfall enhanced density gradients in the water column, and hindered mixing leading to development of bottom-water anoxia. Carbonates precipitating during terminations show large fluctuations in their isotopic composition. Full interglacial conditions in Lake Van are characterized by high or slowly falling lake level. Rainfall and snowmelt feed the lake but due tore-established mixing, the isotopic composition of authigenic carbonates is heavier and closer to that of evaporation-influenced lake water than that of runoff representing snowmelt and atmospheric precipitation. © 2014 Elsevier Ltd.
cited By 45
Keywords: Carbonates; Glacial geology; Isotopes; Lithology; Mixing; Organic carbon; Rain; Snow melting systems; Eastern Mediterranean; Glacial/interglacial cycle; Lake vans; Multi proxies; Oxygen isotopes; Termination; Lakes; anoxia; carbonate; epilimnion; glacial environment; glacial-interglacial cycle; isotopic composition; lithology; numerical model; oxygen isotope; paleoclimate; proxy climate record; rainfall; runoff; snowmelt; Anatolia; Lake Van; Mediterranean Sea; Mediterranean Sea (East); Turkey

Elemental composition of the Laguna Potrok Aike sediment sequence reveals paleoclimatic changes over the past 51 ka in southern Patagonia, Argentina - Hahn, Annette; Kliem, Pierre; Oehlerich, Markus; Ohlendorf, Christian; Zolitschka, Bernd (Journal of Paleolimnology, 2014)
During the lake deep drilling campaign PASADO in 2008, more than 500 m of lacustrine sediment was recovered from the maar lake Laguna Potrok Aike, Argentina. The major element composition was assessed at high resolution with an ITRAX X-ray fluorescence core scanner. The sharp boundary between a carbonate-bearing and a carbonate-free depositional system occurs at 13.5 cal. ka BP and marks the transition from glacial to Late Glacial sediments. Holocene and Late Glacial sediments can be distinguished by elements that are indicative of organic matter (Br, Cl) or calcite (Ca). Glacial sediments are characterized by elements that represent terrigenous clastic input (Fe, Ti, K, Si). Trace elements (Mn, Rb, V, Ni) accumulate with the bulk of lithogenic elements indicating frequent oxic conditions and rare diagenetic remobilization. Based on principal component analysis we interpret the scores of the first principle component as a summarizing indicator for climate-related variations of depositional conditions. During the Holocene climate changes mirror the total inorganic carbon profile, which was used as a proxy for lake-level reconstructions of the past 16 ka in previous studies. High scores in the first principle component probably reflect periods of increased chemical over mechanical weathering and developing soils and vegetation cover limiting sediment availability for erosional processes. These intervals often also show increases in total organic carbon values and total organic carbon/total nitrogen ratios, which are associated with periods of Antarctic warming in the last glacial. Geochemical variations of the clastic glacial sediments are explored by excluding carbonate-bearing sediments from principal component analysis. Although, in this lake, Ca is a purely clastic signal in carbonate-free sediments, it does not correlate with the bulk of indicators for terrigenous input. Instead Ca dominates a second principal component together with Sr. This component mainly distinguishes coarse grained layers from the remaining sediment. The main provenance of this coarse-grained material is suggested to be a basalt outcrop at the western shore. Low lake levels, high waves and flash-flood events may have increased the availability of basaltic sand during extremely cold, arid and windy conditions. High wind speeds and lack of vegetation may have facilitated the increased transport of coarse-grained material into the center of Laguna Potrok Aike. Decreases in the second principal component can be observed during Oxygen Isotope Stage 2 when increased dust input has been found in cores from Laguna Potrok Aike, the Southern Ocean and Antarctica. © 2014, Springer Science+Business Media Dordrecht.

Drilling of the well IDDP-1 - P'alsson, B.; H'olmgeirsson, S.; Guðmundsson, 'A.; B'oasson, H.'A.; Ingason, K.; Sverrisson, H.; Th'orhallsson, S. (Geothermics, 2014)
The first well of three proposed by the Iceland Deep Drilling Project (IDDP) was drilled in the Krafla Geothermal Field in 2008 –2009 by Landsvirkjun, the National Power Company of Iceland. The well was designed to reach supercritical conditions at 4500m, temperatures above 374°C and pressures above 22MPa. Drilling progress was as planned down to around 2000m when drilling became quite challenging, including becoming stuck at 2094 and 2095m depth, followed by twist offs and subsequent side tracking. Finally, drilling came to an end at 2096m depth in the third leg when cuttings of fresh glass indicated the presence of a magma body at the bottom. As the well had such a rigorous well design, the steering committee of the IDDP decided to complete and flow test the well, rather than abandoning it. The well was very powerful and the project has proved to be a valuable experience for drilling supercritical wells in the future and what happens when magma is encountered. Most importantly, it has been proven that it is possible to drill and complete a well in a very hot zone and produce fluid from an environment near a magma body. If sustained long term production proves possible, the drilling of well IDDP-1 will mark a new era in power production in Krafla.
Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma
Keywords: Iceland Deep Drilling Project; Drilling; Magma; Superheat

Facies characterization based on physical properties from downhole logging for the sediment record of Lake Van, Turkey - Baumgarten, H.; Wonik, T.; Kwiecien, O. (Quaternary Science Reviews, 2014)
Lake Van (Turkey) is the 4th largest terminal lake in the world and is located at a key position for climatic reconstruction. The ICDP project 'PALEOVAN' is a deep-drilling campaign initiated in the summer of 2010 to enhance the understanding of paleoclimatic and paleoenvironmental conditions in the Middle East for a period of 550,000 years. Multiple coring of two sites (Northern Basin and Ahlat Ridge) at a water depth of up to 360m has been performed. The sedimentary record is mainly composed of clayey silts and tephra deposits that were supplied by four volcanic sources: 1) the S{uphan volcano, located on the northern shore, 2) the Nemrut volcano, 15km west of the westernshore, 3) the Incekaya volcano, on the southwestern shore and 4) intralake eruptive centers. The dominant chemical composition of the volcanic sources is known from studies of land deposits.High-quality downhole logs have been acquired from both sites. To construct a continuous lithological profile, 180m of downhole logging data from the Ahlat Ridge have been analyzed by cluster analysis. To improve the differentiation of the sediments, two elemental intensity profiles from x-ray fluorescence core-scanning (calcium and zirconium) performed on the composite profile core material were added to the cluster analysis. Five cluster units were derived and transformed into three tephra and two clayey silt units. To compare the two clayey silt units with the composite profile from the visual core description (VCD) that showed 15 lithological units, the composite profile was classified into two major groups of lacustrine sediments: banded clayey silts (interpreted as glacial deposits) and laminated clayey silts (interpreted as interglacial deposits). Despite this simplification, no correlation between the two clayey silt units derived from cluster analysis and the banded and laminated clayey silts could be found. The following reasons are proposed: (a) the comparability of the datasets was limited by significant depth shifts of up to 2.5m between the composite profile based on the VCD and the downhole measurements in hole 2D of the Ahlat Ridge, (b) a correlation was difficult to ascertain from the vertical resolution of the downhole logging data and the extremely detailed core description in mm-scale, (c) mixed signals were obtained because of prevailing thin layers and intercalations of different lithotypes and (d) cluster analysis was difficult to perform because the contrast within the input data is too low (possibly background sedimentation) to distinguish between glacial and interglacial deposits. Tephra units are characterized by contrasting properties and differ mainly in their magnetic susceptibility, spectral gamma ray components (uranium, thorium and potassium) and XRF-intensities of calcium and zirconium. Tephra units have been linked to the dominant volcanic composition of the deposited tephra layers and partly to the volcanic sources. Depth trends are derived with prevailing basaltic deposits in the bottom part (128m-210m below lake floor) and are gradually outweighed by the highly differentiated (dacitic and rhyolitic/trachytic) products towards the top of the record. © 2014 Elsevier Ltd.
cited By 10
Keywords: Physical properties; Downholes; ICDP; Lake sediments; Paleoclimates; PALEOVAN; Quaternary; Tephra; Cluster analysis; basalt; chemical composition; clay; cluster analysis; depositional environment; facies; lacustrine deposit; paleoclimate; paleolimnology; physical property; Pleistocene; sediment core; sedimentation; silt; tephra; volcanic eruption; volcanogenic deposit; well logging; Lake Van; Turkey; Turkey

Geochemistry sampling for traditional and multicomponent equilibrium geothermometry in southeast Idaho - Cannon, C.; Wood, T.; Neupane, G.; McLing, T.; Mattson, E.; Dobson, P.; Conrad, M. (Transactions - Geothermal Resources Council, 2014)
The Eastern Snake River Plain (ESRP) is an area of high regional heat flux due the movement of the North American Plate over the Yellowstone Hotspot beginning ca. 16 Ma. Temperature gradients between 45-60 °C/km (up to double the global average) have been calculated from deep wells that penetrate the upper aquifer system (Blackwell 1989). Despite the high geothermal potential, thermal signatures from hot springs and wells are effectively masked by the rapid flow of cold groundwater through the highly permeable basalts of the Eastern Snake River Plain aquifer (ESRPA) (up to 500+ m thick). This preliminary study is part of an effort to more accurately predict temperatures of the ESRP deep thermal reservoir while accounting for the effects of the prolific cold water aquifer system above. This study combines the use of traditional geothermometry, mixing models, and a multicomponent equilibrium geothermometry (MEG) tool to investigate the geothermal potential of the ESRP. In March, 2014, a collaborative team including members of the University of Idaho, the Idaho National Laboratory, and the Lawrence Berkeley National Laboratory collected 14 thermal water samples from and adjacent to the Eastern Snake River Plain. The preliminary results of chemical analyses and geothermometry applied to these samples are presented herein. Copyright © (2014) by the Geothermal Resources Council All right reserved.
cited By 1
Keywords: Aquifers; Chemical analysis; Geochemistry; Geothermal fields; Geothermal prospecting; Geothermal springs; Groundwater; Groundwater geochemistry; Groundwater resources; Heat flux; Heat transfer; Hot springs; Rivers; Geothermal; Geothermometry; MEG; RTEst; Snake river plains; Geothermal energy

Fault delineation using earthquake energy as a source for pre-stack depth imaging - Haldorsen, J.B.U.; Taylor, S.; Miller, D.E. (SEG Technical Program Expanded Abstracts, 2014)
The San Andreas Fault Observatory at Depth (SAFOD) is a deep borehole observatory constructed to investigate the source of recurring earthquakes at a specific location on the San Andreas Fault. Numerous geophysical datasets were acquired at the SAFOD site to characterize the subsurface environment. Among these, we collected three independent seismic datasets to characterize the local geologic structure. These datasets include VSP, drill-bit noise, and earthquake recordings. Initially, interferometric deconvolution was applied to the drill-bit noise using Schlumberger patented methods to determine the reference signal from rig-based receivers. Next, it was applied in a modified processing flow to determine the reference signal from downhole receivers. Finally, as a result of the application of the technique to earthquake data, we obtained high resolution imaging of the San Andreas Fault at depths exceeding 2.5 km. In conjunction with the other seismic datasets collected at the site, we interpret the complex system of faults and fractures to constitute a flower structure which is partially exposed at Middle Mountain northeast of the SAFOD site. © 2014 SEG.
cited By 0
Keywords: Bits; Drills; Earthquakes; Infill drilling; Observatories; Seismic prospecting; Signal processing; Strike-slip faults; Downhole receivers; Earthquake recording; Fault delineations; Flower structures; Geologic structures; High-resolution imaging; San Andreas fault; Subsurface environment; Signal receivers

Faulting processes in active faults - Evidences from TCDP and SAFOD drill core samples - Janssen, C.; Wirth, R.; Wenk, H.-R.; Morales, L.; Naumann, R.; Kienast, M.; Song, S.-R.; Dresen, G. (Journal of Structural Geology, 2014)
The microstructures, mineralogy and chemistry of representative samples collected from the cores of the San Andreas Fault drill hole (SAFOD) and the Taiwan Chelungpu-Fault Drilling project (TCDP) have been studied using optical microscopy, TEM, SEM, XRD and XRF analyses. SAFOD samples provide a transect across undeformed host rock, the fault damage zone and currently active deforming zones of the San Andreas Fault. TCDP samples are retrieved from the principal slip zone (PSZ) and from the surrounding damage zone of the Chelungpu Fault. Substantial differences exist in the clay mineralogy of SAFOD and TCDP fault gouge samples. Amorphous material has been observed in SAFOD as well as TCDP samples. In line with previous publications, we propose that melt, observed in TCDP black gouge samples, was produced by seismic slip (melt origin) whereas amorphous material in SAFOD samples was formed by comminution of grains (crush origin) rather than by melting. Dauphin'e twins in quartz grains of SAFOD and TCDP samples may indicate high seismic stress. The differences in the crystallographic preferred orientation of calcite between SAFOD and TCDP samples are significant. Microstructures resulting from dissolution-precipitation processes were observed in both faults but are more frequently found in SAFOD samples than in TCDP fault rocks. As already described for many other fault zones clay-gouge fabrics are quite weak in SAFOD and TCDP samples. Clay-clast aggregates (CCAs), proposed to indicate frictional heating and thermal pressurization, occur in material taken from the PSZ of the Chelungpu Fault, as well as within and outside of the SAFOD deforming zones, indicating that these microstructures were formed over a wide range of slip rates. © 2014 Elsevier Ltd.
cited By 26
Keywords: Chemical analysis; Deformation; Grinding (comminution); Microstructure; Minerals; Quartz; Seismology; Strike-slip faults; Tectonics; CPO; EBSD; Fault rock; SAFOD; TCDP; Structural geology; active fault; amorphous medium; calcite; clay mineral; crystal structure; crystallography; deformation; fault gouge; faulting; host rock; melting; microstructure; quartz; San Andreas Fault; slip rate

Frictional properties of exhumed fault gouges in DFDP-1 cores, Alpine Fault, New Zealand - Boulton, C.; Moore, D.E.; Lockner, D.A.; Toy, V.G.; Townend, J.; Sutherland, R. (Geophysical Research Letters, 2014)
Principal slip zone gouges recovered during the Deep Fault Drilling Project (DFDP-1), Alpine Fault, New Zealand, were deformed in triaxial friction experiments at temperatures, T, of up to 350°C, effective normal stresses, σn′, of up to 156 MPa, and velocities between 0.01 and 3 μm/s. Chlorite/white mica-bearing DFDP-1A blue gouge, 90.62 m sample depth, is frictionally strong (friction coefficient, μ, 0.61-0.76) across all experimental conditions tested (T = 70-350°C, σn′ = 31.2-156 MPa); it undergoes a transition from positive to negative rate dependence as T increases past 210°C. The friction coefficient of smectite-bearing DFDP-1B brown gouge, 128.42 m sample depth, increases from 0.49 to 0.74 with increasing temperature and pressure (T = 70-210°C, σn′ = 31.2-93.6 MPa); the positive to negative rate dependence transition occurs as T increases past 140°C. These measurements indicate that, in the absence of elevated pore fluid pressures, DFDP-1 gouges are frictionally strong under conditions representative of the seismogenic crust.
cited By 57
Keywords: Friction; Mica deposits; Alpine Faults; Fault friction; Frictional stability; New zealand; Plate boundaries; strike-slip; Strike-slip faults; deep drilling; experimental study; fault zone; friction; pore pressure; stress field; temperature effect; Alpine Fault Zone; New Zealand; South Island

Frictional strength, rate-dependence, and healing in DFDP-1 borehole samples from the Alpine Fault, New Zealand - Ikari, M.J.; Carpenter, B.M.; Kopf, A.J.; Marone, C. (Tectonophysics, 2014)
The Alpine Fault in southern New Zealand is a major plate-boundary fault zone that, according to various lines of evidence, may be nearing the end of its seismic cycle and approaching earthquake failure. In order to better characterize this fault and obtain a better understanding of its seismic potential, two pilot boreholes have been completed as part of a larger drilling project. Samples representative of the major lithologic subdivisions of the fault zone at shallow ( 100. m) depths were recovered and investigated in laboratory friction experiments. We show here that materials from within and very near the principal slip zone (PSZ) tend to exhibit velocity strengthening frictional behavior, and restrengthen (heal) rapidly compared to samples of the wall rock recovered near the PSZ. Fluid saturation causes the PSZ to be noticeably weaker than the surrounding cataclasites (μ = 0.45), and eliminates the velocity-weakening behavior in these cataclasites that is observed in dry tests. Our results indicate that the PSZ has the ability to regain its strength in a manner required for repeated rupture, but its ability to nucleate a seismic event is limited by its velocity-strengthening nature. We suggest that seismogenic behavior at depth would require alteration of the PSZ material to become velocity weakening, or that earthquake nucleation occurs either within the wall rock or at the interface between the wall rock and the PSZ. Coseismic ruptures which propagate to the surface have been inferred for previous earthquakes on the Alpine Fault, and may be facilitated by the slightly weaker PSZ material and/or high rates of healing in the PSZ which support fault locking and eventual stress drops. © 2014 Elsevier B.V.
cited By 19
Keywords: Boreholes; Boring; Earthquakes; Friction; Interfaces (materials); Locks (fasteners); Seismology; Velocity; Alpine Faults; Earthquake nucleation; Friction experiments; Frictional behavior; Frictional strength; Scientific drilling; Seismicity; Velocity-weakening; Faulting; borehole; earthquake mechanism; earthquake rupture; failure mechanism; friction; lithology; plate boundary; saturation; seismicity; Alpine Fault Zone; New Zealand; South Island

Gas hydrate dissociations in Mallik hydrate bearing zones A, B, and C by depressurization: Effect of salinity and hydration number in hydrate dissociation - Uddin, M.; Wright, F.; Dallimore, S.; Coombe, D. (Journal of Natural Gas Science and Engineering, 2014)
The Mallik gas hydrate deposit was found to consist of 3 distinct, highly concentrated, high quality zones of structure I hydrate with partial occupancy of 5.75-6.2. Earlier simulation studies focused on history matching the 6 days production test of the lower zone, assuming 100% hydrate occupancy. The focus of the current study is on a simulation comparison of the expected response of the three hydrate bearing zones (lower, middle and upper) of the Mallik well 2L-38 to a single vertical well depressurization test. Additionally, a revised history match of the bottom zone field test considering partial gas occupancy of the hydrate, and a further assessment of the kinetic dissociation model are studied. This study extends the previously developed model found to successfully represent the physical and thermodynamic mechanisms involved with hydrate dissociation in the Mallik field test.The simulation results indicate that hydrate production from the middle hydrate zone is feasible and attractive, while production from the upper zone is not, due to its low pressure/temperature condition. Generally speaking, all three zones showed a similar role of the bottom aquifer in determining the water and gas flows, and all three zones showed an upward gas migration block by different existing hydrate layers. This effect is contrary to gas production from conventional gas reservoirs and indicates that the use of horizontal wells in such reservoirs may not be attractive.This study has also explored the role of partial gas cavity occupancy in the lower zone production characteristics and a re-history match of the 6 days Mallik production test showed an improved match and some indication about partial occupancy close to 6.88. Finally an in-depth examination of a previously reported laboratory scale study of methane hydrate decomposition and some observations from even smaller scale molecular dynamics study gave exciting clues of how to further interpret and improve our kinetic gas hydrate model, to be used at multiple time and length scales. Such an improved model has been proposed and awaits further testing and matching of appropriate data. © 2014.
cited By 52
Keywords: Aquifers; Dissociation; Gas industry; Gases; Horizontal wells; Hydration; Molecular dynamics; Petroleum reservoirs; Depressurizations; Hydrate dissociation; Hydration number; Salinity; Simulation; Gas hydrates

Modeling volcano growth on the Island of Hawaii: Deep-water perspectives - Lipman, Peter W.; Calvert, Andrew T. (Geosphere, 2013)
Recent ocean-bottom geophysical surveys, dredging, and dives, which complement surface data and scientific drilling at the Island of Hawaii, document that evolutionary stages during volcano growth are more diverse than previously described. Based on combining available composition, isotopic age, and geologically constrained volume data for each of the component volcanoes, this overview provides the first integrated models for overall growth of any Hawaiian island. In contrast to prior morphologic models for volcano evolution (preshield, shield, postshield), growth increasingly can be tracked by age and volume (magma supply), defining waxing alkalic, sustained tholeiitic, and waning alkalic stages. Data and estimates for individual volcanoes are used to model changing magma supply during successive compositional stages, to place limits on volcano life spans, and to interpret composite assembly of the island. Volcano volumes vary by an order of magnitude; peak magma supply also varies sizably among edifices but is challenging to quantify because of uncertainty about volcano life spans. Three alternative models are compared: (1) near-constant volcano propagation, (2) near-equal volcano durations, (3) high peak-tholeiite magma supply. These models define inconsistencies with prior geodynamic models, indicate that composite growth at Hawaii peaked ca. 800 –400 ka, and demonstrate a lower current rate. Recent age determinations for Kilauea and Kohala define a volcano propagation rate of 8.6 cm/yr that yields plausible inception ages for other volcanoes of the Kea trend. In contrast, a similar propagation rate for the less-constrained Loa trend would require inception of Loihi Seamount in the future and ages that become implausibly large for the older volcanoes. An alternative rate of 10.6 cm/yr for Loa-trend volcanoes is reasonably consistent with ages and volcano spacing, but younger Loa volcanoes are offset from the Kea trend in age-distance plots. Variable magma flux at the Island of Hawaii, and longer-term growth of the Hawaiian chain as discrete islands rather than a continuous ridge, may record pulsed magma flow in the hotspot/plume source.

Petrology of impactites from El'gygytgyn crater: Breccias in ICDP-drill core 1C, glassy impact melt rocks and spherules - Wittmann, A.; Goderis, S.; Claeys, P.; Vanhaecke, F.; Deutsch, A.; Adolph, L. (Meteoritics and Planetary Science, 2013)
El'gygytgyn is a 18km diameter, 3.6Ma old impact crater in NE Siberia. International Continental Scientific Drilling Program-El'gygytgyn hole 1C was drilled on the frozen crater lake, 2.3km from the crater center to a final depth of 517m below the lake floor. Petrographic and geochemical analyses of 26 drill core samples, three impact melt rocks from the surface, and seven glass spherules from surface deposits outside the crater are used to characterize the impactite inventory at El'gygytgyn. The bottom 98m of hole 1C intersected monomict brecciated, unshocked, rhyolitic ignimbrite with minor intercalations of polymict breccia and mafic inclusions. These lithologies are overlain by 89m of polymict breccia whose components occasionally exhibit scarce, low-degree shock metamorphic features. This unit is succeeded by 10m of suevite that contains about 1 vol% glassy impact melt shards <1cm in size and a low amount of shock metamorphosed lithic clasts. The suevite is capped by a reworked fallout deposit that constitutes a transition over 4m into lacustrine sedimentation. A higher abundance of shock metamorphosed lithic clasts, and glass spherules, some with Ni-rich spinel and admixture of an ultramafic component, characterize this unit. We tentatively interpret this impactite section as allochthonous breccia in the vicinity of El'gygytgyn's central ring uplift. The geochemical compositions of seven glass spherules from terrace deposits 2km outside the crater and eight spherules from the reworked fallout deposit in hole 1C show far greater variability than the composition of impact melt shards and impact melt rocks. Some of these spherules also show strong enrichments in siderophile elements. © The Meteoritical Society, 2013.
cited By 29

Petrography, geochemistry, and Hf-Nd isotope evolution of drill core samples and target rocks from the El'gygytgyn impact crater, NE Chukotka, Arctic Russia - Pittarello, L.; Schulz, T.; Koeberl, C.; Hoffmann, J.E.; M{unker, C. (Meteoritics and Planetary Science, 2013)
El'gygytgyn in northeast Chukotka (Russia) is a 3.6 Ma, 18-km-diameter impact structure. The impact crater was recently drilled in the framework of a project sponsored by the International Continental Scientific Drilling Program (ICDP). Target rocks at the El'gygytgyn area are dominated by the felsic members of the Late Cretaceous Okhotsk-Chukotka Volcanic Belt (OCVB). Such a target lithology is unique among terrestrial impact craters, thereby providing the opportunity to study shock metamorphism in siliceous volcanic rocks. Here, we present a petrographic, geochemical, and isotopic study of the section of the drill core underneath the lacustrine sediments, extending from ∼316 m to 517 m below the lake bottom (blb). The drill core stratigraphy includes ∼80 m of suevite and a cross section through a volcanic suite, which consists of (1) a middle section (∼390-423 mblb) with dominant felsic tuffs and a few mafic members, and (2) a welded rhyolitic-dacitic ignimbrite (∼423-517 mblb). The melt fragments embedded in the suevite are interpreted as being impact-related by comparison with impact glasses from the crater and in opposition to the target rock, which does not include similar melts. A suevitic dyke crosscuts the lower section of the core at the depth 471.40 mblb. Evidence for shock metamorphism is concentrated in the upper 10 m of the drill core and almost limited to the suevitic breccia. The geochemical and isotope (Nd and Hf) composition of samples from the target and the drill core reveals relationships to the Berlozhya magmatic assemblage (BMA) arguing for similar source magmas. The primitive upper mantle (PUM)-normalized trace element plot of rocks investigated here confirms a subduction-related signature, as previously proposed for rocks from both OCVB and BMA. © The Meteoritical Society, 2013.
cited By 20

Paleoflora Assemblages of Late Cretaceous Algae from SK-1s Well in the Songliao Basin (in Chinese); 松辽盆地松科1井南孔晚白垩世藻类化石组合划分 - Zhang, Y. (Journal of Stratigraphy, 2013)

Petrography and geochemistry of impactites and volcanic bedrock in the ICDP drill core D1c from Lake El'gygytgyn, NE Russia - Raschke, U.; Schmitt, R.T.; Reimold, W.U. (Meteoritics and Planetary Science, 2013)
The 3.6 Ma old and 18 km diameter El'gygytgyn impact structure in NE Siberia was drilled in 2008/09 by ICDP (International Continental Scientific Drilling Program). A 517 m long core hole (D1c) was drilled into the outer flank of the central uplift structure, with an overall core recovery of approximately 63%. Thereby, approximately 315 m lake sediments and approximately 202 m impactites were recovered. Here, we present a detailed petrographic and geochemical assessment of the impact breccia and bedrock sections in this core. The 97 m long lower bedrock unit (517-420 m below lake floor [blf]) consists of an ignimbrite. In the overlying upper bedrock unit (420-390 mblf), the core recovered a sequence of similar ignimbrite and several decimeters of mafic rocks. We interpret these units as rocks that are located close to their former, preimpact position, but have been somewhat rotated due to collapse of the central uplift (i.e., it represents parautochthonous basement). From about 390 to 328 mblf occurs a suevite package with an impact melt poor, clast-dominated matrix, and lithic and mineral clasts that cover the entire range of volcanic target rocks known from the El'gygytgyn region. All stages of shock metamorphism (unshocked to melted) were observed in clasts, and in microclasts of the matrix, of suevite from different depths. Immediately below this package, at the contact to the underlying bedrock, occurs a 1 m wide sheared zone within vitrophyric ignimbrite, which we consider the actual crater floor. The uppermost approximately 12 m, from 328-316 mblf depth, seem to comprise reworked suevite, consisting of a mixture of sediments and suevite with more and, on average, stronger shocked minerals than found in the main suevite unit. This includes a small component of glassy spherules and impact melt fragments. Toward the top of this unit, lake sediments progressively become the dominant material in this section. We assume that this unit contains a fallback component from the ejecta plume that was mixed with the first sediments of the postimpact crater lake, and possibly some rocks that slumped off the inner crater wall-similar to a thin layer at the base of the sediment section of borehole LB-5A recovered in Lake Bosumtwi (Ghana). © The Meteoritical Society, 2013.
cited By 32

Past climate changes and permafrost depth at the Lake El'gygytgyn site: implications from data and thermal modeling - Mottaghy, D.; Schwamborn, G.; Rath, V. (Climate of the Past, 2013)
This study focuses on the temperature field observed in boreholes drilled as part of interdisciplinary scientific campaign targeting the El'gygytgyn Crater Lake in NE Russia. Temperature data are available from two sites: the lake borehole 5011-1 located near the center of the lake reaching 400 m depth, and the land borehole 5011-3 at the rim of the lake, with a depth of 140 m. Constraints on permafrost depth and past climate changes are derived from numerical simulation of the thermal regime associated with the lake-related talik structure. The thermal properties of the subsurface needed for these simulations are based on laboratory measurements of representative cores from the quaternary sediments and the underlying impact-affected rock, complemented by further information from geophysical logs and data from published literature. The temperature observations in the lake borehole 5011-1 are dominated by thermal perturbations related to the drilling process, and thus only give reliable values for the lowermost value in the borehole. Undisturbed temperature data recorded over more than two years are available in the 140 m deep land-based borehole 5011-3. The analysis of these observations allows determination of not only the recent mean annual ground surface temperature, but also the ground surface temperature history, though with large uncertainties. Although the depth of this borehole is by far too insufficient for a complete reconstruction of past temperatures back to the Last Glacial Maximum, it still affects the thermal regime, and thus permafrost depth. This effect is constrained by numerical modeling: assuming that the lake borehole observations are hardly influenced by the past changes in surface air temperature, an estimate of steady-state conditions is possible, leading to a meaningful value of 14 ± 5 K for the post-glacial warming. The strong curvature of the temperature data in shallower depths around 60 m can be explained by a comparatively large amplitude of the Little Ice Age (up to 4 K), with low temperatures prevailing far into the 20th century. Other mechanisms, like varying porosity, may also have an influence on the temperature profile, however, our modeling studies imply a major contribution from recent climate changes. © Author(s) 2013.
cited By 12
Keywords: borehole; climate variation; crater lake; drilling; interdisciplinary approach; Last Glacial Maximum; Little Ice Age; paleoclimate; paleotemperature; permafrost; reconstruction; recovery plan; surface temperature; talik; Chukchi; Elgygytgyn Lake; Russian Federation

Paleobathymetry and sequence stratigraphic interpretations from benthic foraminifera: Insights on New Jersey shelf architecture, IODP Expedition 313 - Katz, M.E.; Browning, J.V.; Miller, K.G.; Monteverde, D.H.; Mountain, G.S.; Williams, R.H. (Geosphere, 2013)
Integrated Ocean Drilling Program (IODP) Expedition 313 drilled three holes (Sites M27, M28, and M29; 34-36 m present water depth) across a series of prograding clinothems from the inner continental shelf of the New Jersey (USA) margin, a region that is sensitive to sea-level change. We examined 702 late Eocene to Miocene samples for benthic foraminiferal assemblages and planktonic foraminiferal abundances. We integrate our results with lithofacies to reconstruct paleobathymetry. Biofacies at all three sites indicate a long-term shallowing-upward trend as clinothems built seaward and sediment fi lled accommodation space. Patterns in biofacies and lithofacies indicate shallowing-and deepening-upward successions within individual sequences, providing the basis to recognize systems tracts, and therefore sequence stratigraphic relationships in early to early-middle Miocene sequences (ca. 23-13 Ma). The clinothem bottomsets and the lower portions of the foresets, which contain the thickest parts of clinothems, yield the deepest water biofacies. Shallower bio facies characterize the sequences in the upper portions of the clinothem foresets and on the topsets. Topsets are characterized by transgressive (TST) and highstand systems tracts (HST). Foresets contain lowstand systems tracts (LST), TSTs, and HSTs. Flooding surfaces mark parasequence boundaries within LSTs, TSTs, and HSTs. Superimposed on the long-term trends, short-term variations in paleowater depth are likely linked to global sea-level changes indicated by global oxygen isotopic variations.
cited By 23
Keywords: Accommodation space; Benthic foraminifera; Foraminiferal assemblages; Highstand systems tract; Individual sequences; Integrated ocean drilling programs; Sequence-stratigraphic interpretation; Short-term variations; Sea level; Stratigraphy; Tectonics; Coastal zones; benthic foraminifera; continental shelf; depositional sequence; Eocene; Miocene; Ocean Drilling Program; parasequence; sequence boundary; sequence stratigraphy; systems tract; transgression; Atlantic Ocean; New Jersey Shelf; Foraminifera

Paleoatmospheric pCO2 fluctuations across the Cretaceous-Tertiary boundary recorded from paleosol carbonates in NE China - Huang, C.; Retallack, G.J.; Wang, C.; Huang, Q. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2013)
A dramatic change in atmospheric composition has been postulated because of global carbon cycle disruption during the Cretaceous (K)-Tertiary (T) transition following the Chicxulub impact and Deccan Trap eruptions. Here, pedogenic carbonates were collected from drill core of a borehole (SK-1 (N)) straddling the Late Cretaceous and early Paleocene strata in the Songliao Basin, northeast China, to reconstruct atmospheric CO2 concentrations using a paleosol paleobarometer. Our estimates for atmospheric pCO2 from paleosol carbonates range between 277±115ppmv and 837±164ppmv between 67.8Ma and 63.1Ma. One large ( 66-65.5Ma) and several small CO2 spikes ( 64.7- 64.2Ma) during the latest Maastrichtian to earliest Danian are reported here and incorporated with previously published pCO2 estimates also estimated from paleosol carbonates. These CO2 spikes are attributed to one-million-year-long emplacement of the large Deccan flood basalts along with the extraterrestrial impact at the K-T boundary. © 2013 Elsevier B.V.
cited By 47
Keywords: atmospheric chemistry; borehole; carbon cycle; carbon dioxide; carbonate; crater; Cretaceous-Tertiary boundary; Danian; flood basalt; Maastrichtian; paleoatmosphere; paleoclimate; paleosol; pedogenesis; volcanic eruption; Atlantic Ocean; Bay of Campeche; Chicxulub Crater; China; Deccan; Gulf of Mexico; India; Mexico [North America]; Songliao Basin; Yucatan

Petrophysical characterization of the lacustrine sediment succession drilled in Lake El'gygytgyn, Far East Russian Arctic - Gebhardt, A. C.; Francke, A.; K{uck, J.; Sauerbrey, M.; Niessen, F.; Wennrich, V.; Melles, M. (Climate of the Past, 2013)
Seismic profiles of Far East Russian Lake El'gygytgyn, formed by a meteorite impact some 3.6 million years ago, show a stratified sediment succession that can be separated into subunits Ia and Ib at approximately 167 m below lake floor (Combining double low line∼3.17 Ma). The upper (Ia) is well-stratified, while the lower is acoustically more massive and discontinuous. The sediments are intercalated with frequent mass movement deposits mainly in the proximal areas, while the distal region is almost free of such deposits at least in the upper part. In spring 2009, a long core drilled in the lake center within the framework of the International Continental Scientific Drilling Program (ICDP) penetrated the entire lacustrine sediment succession down to ∼320 m below lake floor and about 200 m farther into the meteorite-impact-related bedrock. Downhole logging data down to 390 m below lake floor show that the bedrock and the lacustrine part differ significantly in their petrophysical characteristics. The contact between the bedrock and the lacustrine sediments is not abrupt, but rather transitional with a variable mixture of impact-altered bedrock clasts in a lacustrine matrix. Physical and chemical proxies measured on the cores can be used to divide the lacustrine part into five different statistical clusters. These can be plotted in a redox-condition vs. input-type diagram, with total organic carbon content and magnetic susceptibility values indicating anoxic or oxic conditions and with the Si/Ti ratio representing more clastic or more biogenic input. Plotting the clusters in this diagram allows identifying clusters that represent glacial phases (cluster I), super interglacials (cluster II), and interglacial phases (clusters III and IV). © Author(s) 2013.
cited By 12
Keywords: bedrock; biogenic deposit; clastic sediment; diagram; drilling; interglacial; lacustrine deposit; mass movement; meteorite; petrology; physicochemical property; redox conditions; Chukchi; Elgygytgyn Lake; Russian Federation

Petrology, major and trace element geochemistry, geochronology, and isotopic composition of granitic intrusions from the vicinity of the Bosumtwi impact crater, Ghana - Losiak, Anna; Schulz, Toni; Buchwaldt, Robert; Koeberl, Christian (Lithos, 2013)
The Bosumtwi crater is 10.5. km in diameter, 1.07. Ma old, well preserved impact structure located in Ghana (centered at 06°30'N, 01°25'W). It was excavated in rocks of the Early Proterozoic Birimian Supergroup, part of the West African craton. Here, we present a full and detailed characterization of the three granitoid complexes and one mafic dike in the vicinity of the Bosumtwi crater in terms of petrology, major and trace element geochemistry, geochronology, and isotopic composition. This allows us to characterize magmatic evolution of the West African Craton in this area and better understand the geological framework and target rocks of the impact.This study shows that the similar composition (strongly peraluminous muscovite granites and granodiorites) and age (between 2092. ±. 6. Ma and 2098. ±. 6. Ma) of all granitic intrusions in the proximity of the Bosumtwi crater suggest that they are co-genetic. Granitoids were probably formed as a result of anatexis of TTGs (or rocks derived from them) at relatively low pressure and temperature. We propose that the intrusions from the Bosumtwi area are genetically related to the Banso granite occurring to the east of the crater and can be classified as basin-type, late-stage granitoids. Also a mafic dike located to the NE of the Bosumtwi crater seems to be genetically related to those felsic intrusions. Based on those findings a revised version of the geological map of the Bosumtwi crater area is proposed. © 2013.
Keywords: Ghana; geochronology; granite; granitoid; igneous geochemistry; igneous intrusion; impact structure; isotopic composition; magmatism; petrogenesis; petrology; Proterozoic; trace element

Reevaluation of siderophile element abundances and ratios across the Cretaceous-Paleogene (K-Pg) boundary: Implications for the nature of the projectile - Goderis, S.; Tagle, R.; Belza, J.; Smit, J.; Montanari, A.; Vanhaecke, F.; Erzinger, J.; Claeys, P. (Geochimica et Cosmochimica Acta, 2013)
The discovery over 30years ago at Gubbio (Italy) and Caravaca (Spain) of an enrichment in the concentrations of iridium (Ir) and the other platinum group elements (PGE) by up to four orders of magnitude (Irmax=0.10-87ng/g) compared to average continental crustal background levels remains one of the most important discoveries in the Earth sciences. Since then, similar anomalies have been detected in more than 120 Cretaceous-Paleogene (K-Pg) boundary sites worldwide. Highly elevated Ir and other siderophile element abundances in roughly chondritic ratios are considered strong indicators for the presence of a meteoritic contribution in impact-related lithologies (melt rocks, impact ejecta material, etc.), delivered when an extraterrestrial object strikes Earth. The presented work adds 113 unpublished PGE analyses of 38 K-Pg sections worldwide to the existing literature. The analytical protocol relied on for this purpose consisted of a combination of a nickel-sulfide fire assay pre-concentration technique and subsequent trace metal determination via inductively coupled plasma-mass spectrometry (ICP-MS). Through repeated determination of key siderophile elements (i.e., Cr, Co, Ni, and PGE), the importance of sampling, nugget effects, and analytical methodologies applied becomes more apparent. Even more critically, these analytical effects are superimposed by the local syn- and post-depositional conditions that have affected the pristine meteoritic signature of the K-Pg impactor, including potential fractionation during vaporization and condensation, dissimilar PGE carrier phases, terrestrial PGE input, sedimentation rate, reworking, diagenesis, bioturbation, and chemical diffusion. While chondrite-normalized PGE patterns of individual sites appear relatively flat (i.e., chondritic), strong variations in siderophile element content and inter-element ratios exist between K-Pg locations, inter-laboratory measurements, and replicate analyses, hampering a precise projectile identification using (highly) siderophile elements. Only when considering improved databases of siderophile element concentrations in meteorites, in combination with linear regression analysis to calculate inter-element ratios from a large suite of ejecta deposit sites, the nature of the K-Pg projectile can be resolved. Application of this methodology to an extensive data set of continental and marine sites, very proximal to distal to the Chicxulub impact structure, supports a carbonaceous chondritic impactor (type CM or CO). © 2013 Elsevier Ltd.
cited By 61

Pleistocene sequence stratigraphy of the shallow continental shelf, offshore New Jersey: Constraints of integrated ocean drilling program Leg 313 core holes - Miller, K.G.; Sugarman, P.J.; Browning, J.V.; Sheridan, R.E.; Kulhanek, D.K.; Monteverde, D.H.; Wehmiller, J.F.; Lombardi, C.; Feigenson, M.D. (Geosphere, 2013)
We used cores and logs from Integrated Ocean Drilling Program (IODP) Expedition 313 to generate biostratigraphic, lithofacies, biofacies, and geochemical data that constrain the ages and paleoenvironments of Pleistocene sequences. We integrate sequence stratigraphy on cores with new seismic stratigraphic data to interpret the Pleistocene history of the Hudson shelf valley and paleoenvironmental and sea-level changes on the inner to middle continental shelf. Improved age control compared to previous studies is provided by integrated calcareous nannofossil biostratigraphy, Sr isotopic stratigraphy, and amino acid racemization. We recognize four upper Pleistocene-Holocene sequences: sequence uP1 is correlated with Marine Isotope Chrons (MIC; chron is the correct stratigraphic term for a time unit, not stage) 7 or 5e, sequence uP2 with MIC 5c, sequence uP3 with MIC 5a, and sequence uP4 with the latest Pleistocene to Holocene (MIC 1-2). However, within our age resolution it is possible that sequences uP2 and uP3 correlate with MIC 4-3c and 3a, respectively, as suggested by previous studies. Lower Pleistocene sequences lP1 and lP2 likely correlate with peak interglacials (e.g., MIC 31 and MIC 45 or 47, respectively). Thus, we suggest that preservation of sequences occurs only during peak eustatic events (e.g., MIC 45 or 47, MIC 31, and MIC 5), unless they are preserved in eroded valleys. The architecture of the Pleistocene deposits at Sites M27 and M29 is one of thin remnants of highstand and transgressive systems tracts, with lowstand deposits only preserved in the thalwegs of incised valleys. Incised valleys at the bases of sequences uP3 (IODP Site M27) and uP2 (IODP Site M29) document more southward courses of the paleo-Hudson valley, compared to the more southeastward course of the MIC 1-2 paleo-Hudson valley. The patchy distribution of Pleistocene sequences beneath the New Jersey inner-middle continental shelf is due to low accommodation during an interval of large eustatic changes; this predicts that sequences in such settings will be discontinuous, patchy, and difficult to correlate, consistent with previous studies in Virginia and North Carolina. © 2013 Geological Society of America.
cited By 19
Keywords: biofacies; biostratigraphy; continental shelf; eustacy; incised valley; integrated approach; lithofacies; marine isotope stage; nanofossil; Ocean Drilling Program; paleoceanography; paleoenvironment; Pleistocene; Pleistocene-Holocene boundary; sea level change; seismic stratigraphy; sequence stratigraphy; thalweg; transgression; New Jersey; United States

Pliocene warmth, polar amplification, and stepped pleistocene cooling recorded in NE Arctic Russia - Brigham-Grette, J.; Melles, M.; Minyuk, P.; Andreev, A.; Tarasov, P.; DeConto, R.; Koenig, S.; Nowaczyk, N.; Wennrich, V.; Rosen, P.; Haltia, E.; Cook, T.; et al. (Science, 2013)
Understanding the evolution of Arctic polar climate from the protracted warmth of the middle Pliocene into the earliest glacial cycles in the Northern Hemisphere has been hindered by the lack of continuous, highly resolved Arctic time series. Evidence from Lake El'gygytgyn, in northeast (NE) Arctic Russia, shows that 3.6 to 3.4 million years ago, summer temperatures were ∼8°C warmer than today, when the partial pressure of CO2 was ∼400 parts per million. Multiproxy evidence suggests extreme warmth and polar amplification during the middle Pliocene, sudden stepped cooling events during the Pliocene-Pleistocene transition, and warmer than present Arctic summers until ∼2.2 million years ago, after the onset of Northern Hemispheric glaciation. Our data are consistent with sea-level records and other proxies indicating that Arctic cooling was insufficient to support large-scale ice sheets until the early Pleistocene.
cited By 181
Keywords: carbon dioxide; climate variation; cooling; ice sheet; Northern Hemisphere; paleoclimate; Pliocene-Pleistocene boundary; proxy climate record; sea level change; arctic climate; article; carbon dioxide tension; cooling; glacial period; glaciation; greenhouse gas; ice sheet; Pleistocene; Pliocene; priority journal; summer; Arctic Ocean; Russian Federation

Potential and limits of OSL, TT-OSL, IRSL and pIRIR290 dating methods applied on a Middle Pleistocene sediment record of Lake El'gygytgyn, Russia - Zander, A.; Hilgers, A. (Climate of the Past, 2013)

Preliminary estimation of Lake El'gygytgyn water balance and sediment income - Fedorov, G.; Nolan, M.; Brigham-Grette, J.; Bolshiyanov, D.; Schwamborn, G.; Juschus, O. (Climate of the Past, 2013)
Modern process studies of the hydrologic balance of Lake El'gygytgyn, central Chukotka, and the sediment income from the catchment were carried out during a field campaign in spring and summer 2003. Despite high uncertainties due to the limited data, the results provide important first estimates for better understanding the modern and past sedimentation processes in this basin. Formed ca. 3.6 million years ago as a result of a meteorite impact, the basin contains one of the longest paleoclimate records in the terrestrial Arctic. Fluvial activity is concentrated over the short snowmelt period (about 20 days in second part of June). Underground outflow plays a very important role in the water balance and predominates over surface outflow. The residence time of the lake water is estimated to be about 100 yr. © 2013. CC Attribution 3.0 License.
cited By 16
Keywords: catchment; data acquisition; estimation method; fluvial deposit; outflow; paleoclimate; residence time; seasonal variation; terrestrial ecosystem; uncertainty analysis; water budget; Chukchi; Elgygytgyn Lake; Russian Federation

Pyrite morphology in the first member of the Late Cretaceous Qingshankou Formation, Songliao Basin, Northeast China - Wang, P.; Huang, Y.; Wang, C.; Feng, Z.; Huang, Q. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2013)
The study of sedimentary pyrite morphological characteristics provides useful information on depositional environments and early diagenic processes and can be used as an indicator of redox conditions in ancient lake bottom waters. The results of this study in the Songliao basin in northeastern China show that euhedral crystals and framboids are the dominant pyrite forms in the mudstones of the first member of the Qingshankou Formation (K2qn1). The framboidal size distribution indicates that during the deposition of K2qn1, redox conditions in the bottom water fluctuated from oxic-dysoxic to euxinic-anoxic to oxic-dysoxic. The presence of euxinic-anoxic bottom water suggests that an anoxic event developed in the Songliao ancient-lake and continued for 196ka. The development of an anoxic bottom environment was the most important factor in hydrocarbon source rock formation in the Songliao Basin. © 2012 Elsevier B.V.
cited By 54
Keywords: anoxic conditions; bottom water; Cretaceous; depositional environment; diagenesis; hydrocarbon resource; lake water; mudstone; pyrite; redox conditions; size distribution; source rock; China; Songliao Basin

Quantitative and qualitative constraints on hind-casting the formation of multiyear lake-ice covers at Lake El'gygytgyn - Nolan, M. (Climate of the Past, 2013)

Reconstruction of palaeoprecipitation based on pollen transfer functions - the record of the last 16ka from Laguna Potrok Aike, southern Patagonia - Sch{abitz, Frank; Wille, Michael; Francois, Jean-Pierre; Haberzettl, Torsten; Quintana, Flavia; Mayr, Christoph; L{ucke, Andreas; Ohlendorf, Christian; Mancini, Virginia; Paez, Marta M.; Prieto, Aldo R.; Zolitschka, Bernd (Quaternary Science Reviews, 2013)
Based on modern pollen samples from different vegetation units in southern Patagonia, showing a close relation to yearly amounts of precipitation and mean annual temperatures, different pollen-climate transfer functions are developed and tested. Comparing the performance of MAT (Modern Analogue Techniques), WA (Weighted Average), as well as WAPLS (Weighted Average Partial Least Square) statistical techniques, it is possible to determine the statistically most robust model (WAPLS for precipitation). This transfer function is then used to estimate palaeoprecipitation amounts based on Laguna Potrok Aike pollen results for the last 16,000 years. Generally, the results of the precipitation model indicate less precipitation during the Lateglacial and alternating wet and dry periods during the Holocene. The Holocene started with higher amounts of precipitation until about 8kacal.BP, followed by a period with lower amounts between 8 and 2.5kacal.BP, while the Late Holocene shows a general increase in precipitation. Comparisons with former shoreline reconstructions and carbonate concentrations in the sediments of Laguna Potrok Aike not always show similarities due to the complex environmental factors recorded by these proxies. Moreover, changes in the moisture availability due to the interplay of precipitation and temperature, cannot be reconstructed directly. Nevertheless, the general long-term trend of palaeoprecipitation is in accordance with the absolute moisture content in the air, which is determined mainly by temperature: during cold periods with less absolute moisture, the model shows less precipitation. Moreover, the model also points to a relation with the position and strength of the Southern Hemisphere Westerlies. © 2013 Elsevier Ltd.
Keywords: Argentina; Laguna Potrok Aike; Patagonia; Santa Cruz [Argentina]; Moisture; Statistical methods; Transfer functions; ICDP-project PASADO; Late quaternary; Modern pollen samples; Palaeoclimate; Pollen; Precipitation reconstruction; Southern Hemisphere; carbonate; concentration (composition); environmental factor; Holocene; numerical model; pollen; precipitation (climatology); reconstruction; Southern Hemisphere; temperature effect; Lasers

Relaxation of concentration variance: A new tool to measure chemical element mobility during mixing of magmas - Perugini, D.; De Campos, C.P.; Dingwell, D.B.; Dorfman, A. (Chemical Geology, 2013)
The ability of chemical elements to diffuse in silicate melts is central to igneous processes. It controls the rates of phase transitions such as crystal growth and dissolution kinetics, the rate of homogenization of compositional gradients generated by fractional crystallization and assimilation of country rocks as well as one of the most intriguing processes of all, magma mixing.A very useful measure, commonly used to quantify the rate of homogenization of chemical elements in silicate melts, is the diffusion coefficient. It is widely approximated to be of a constant value (at a fixed pressure and temperature) for a melt with a given composition and rheology. When dealing with magma mixing processes, melts with different initial compositions and rheological properties (e.g. basalt and rhyolite) coexist in the same system. Under such circumstances, the compositional and rheological dependence of diffusion coefficients must be considered, leading to a considerable increase of complexity in the modeling of magma mixing. Yet, an additional and even more dramatic increase in complexity is due to the fact that the mixing of magmas is undoubtedly a very dynamic process. Scale-invariant distributions of filaments of different melts are generated by stretching and folding dynamics. This has a dual effect on the mobility of chemical elements. On the one hand their mobility increases because of an exponential increase of contact area. On the other hand, mobility can be buffered by the different diffusivities in the melts (larger in the low-viscosity than in the high-viscosity melt). Uphill diffusion of chemical elements is likely to develop at the interface between interacting magmas, further increasing the complexity of the process.Here we aim to understand chemical element mobility during melt homogenization in a magma mixing event under dynamic conditions. We have performed experiments by mixing phonolitic and alkali-basaltic melts. The mixing process was induced using a high-temperature centrifuge apparatus. The rotating speed and acceleration during all experiments were 1850. rpm and 1000. g, respectively. Experiments were performed for 5, 20 and 120. min. Samples were arranged in a buoyantly unstable geometry, with the denser material placed at the inner side of the rotating circle, resulting in injection of the mafic melt into the felsic melt during rotation. The temperature during experimental runs was 1200 (± 1)°C.From the resultant glasses, vortex-like structures generated by repeated stretching and folding dynamics were observed at the interface between the two melts. The concentrations of major and trace elements were then measured along interfaces by electron microprobe and LA-ICP-MS. The mobility of each element was next quantified by calculating the decrease (or relaxation) of concentration variance with time. The first notable result is that for major and trace elements, concentrations variance decays exponentially. The exponent of the exponential function is then chosen as a measure of element mobility. Our results show clearly that different chemical elements homogenize in the melt at differing rates. Amongst the major elements Na is the fastest element followed by Al, Mg, Ca, K and Si. The trace elements, Ba, Rb, Sr, Nb and Zr exhibit similar mobilities. The REE display the lowest mobility and they show a systematic decrease from light to heavy.The results from this study indicate that the decay of concentration variance is a robust tool for obtaining new insights into chemical exchanges during the mixing of silicate melts. Concentration variance includes in a single measure an expression of the influence of all possible factors (e.g. viscosity, composition, fluid-dynamic regime) controlling the mobility of chemical elements during the mixing of two liquids. A new parameter, the Relaxation of Concentration Variance (RCV), is proposed as an effective tool for quantifying the homogenization of chemical elements during the mixing of silicate melts. © 2012 Elsevier B.V.
cited By 28
Keywords: Centrifuge experiments; Chemical exchange; Compositional gradients; Contact areas; Crystal growth and dissolution; Dual effect; Dynamic condition; Dynamic process; Effective tool; Electron microprobes; Element mobility; Exponential increase; Folding dynamics; Fractional crystallization; High temperature; High viscosities; Initial composition; La-ICP-MS; Magma mixing; Major and trace elements; Major elements; Mixing process; Natural melts; New parameters; Pressure and temperature; Rheological property; Rotating speed; Scale-invariant; Silicate melts; Up-hill diffusion; Barium; Centrifuges; Chemical elements; Crystal growth; Diffusion; Dynamics; Experiments; Mixing; Niobium; Rheology; Rubidium; Silicates; Sodium; Spectrometry; Viscosity; Zirconium; Process control; alkali basalt; centrifugal model test; concentration (composition); country rock; dissolution; element mobility; experimental study; fractional crystallization; igneous geochemistry; magma; P-T conditions; reaction kinetics; rheology; silicate melt; trace element

Origin of two Verwey transitions in different generations of magnetite from the Chesapeake Bay impact structure, USA - Mang, C.; Kontny, A. (Journal of Geophysical Research: Solid Earth, 2013)
We observed two different Verwey transition temperatures in fragments of crystalline basement rocks and impact sediments from the Chesapeake Bay impact structure, USA. Our study aims to the question if this feature can be used as shock indicator in impact craters. We distinguished three generations of magnetite. (1) Primary magnetite in crystalline basement rocks has average grain sizes up to several hundreds of micrometers and shows a regular TV at ≈ 121 K. (2) Shocked magnetite occurs in fragments of crystalline basement rocks and also in the suevite and impact breccia. These magnetites show two Verwey transitions - a regular one and a lowerature transition (LTV) at around 89 K. LTV is related to a small grain size fraction, whereas a larger grain size fraction (some hundreds of micrometers) causes the regular TV. The small grain size fraction contains a distinctly higher amount of superficially oxidized material due to the high surface/volume ratio, which causes a decrease of the Verwey transition temperature (LTV). (3) A secondary magnetite generation shows also two Verwey transition temperatures, one at 121 K and a LTV range between 91 and 105 K. The LTV in this generation is also linked to thin oxidized surface layers. This study shows that especially the Verwey transition temperature of small magnetite grains reacts very sensitively to surface oxidation and can therefore not be used as a reliable pressure indicator for impact structures on Earth. Key Points Reduction of Verwey transition due to nonstoichiometry Degree of nonstoichiometry triggered by grain size Surface/volume ratio crucial for reduction of Verwey transition ©2013. American Geophysical Union. All Rights Reserved.
cited By 9
Keywords: basement rock; breccia; crystalline rock; grain size; hysteresis; impact structure; low temperature; magnetite; oxidation; suevite; temperature gradient; Chesapeake Bay; United States

REPORT ON THE ICDP WORKSHOP DOVE “DRILLING OVERDEEPENED ALPINE VALLEYS”(COMO AND VALTELLINA, 3-5 APRIL 2013) - Pini, Roberta (Alpine and Mediterranean Quaternary, 2013)

Paleoarchean sulfur cycle and biogeochemical surface conditions on the early Earth, Barberton, South Africa - Grosch, Eugene G.; McLoughlin, Nicola (Earth and Planetary Science Letters, 2013)
This study presents the first multiple sulfur isotope dataset on sulfides from the ca. 3.5-3.2 Ga Onverwacht Group in the Paleoarchean Barberton Greenstone Belt (BGB) of South Africa. In situ δ34SCDT and δ33S values of pyrite (n = 568) are reported from a wide range of hydrothermal, volcanic and sedimentary environments and are used to explore Mid-Archean biogeochemical sulfur cycling. Samples are from fresh drill core collected by the Barberton Scientific Drilling Project that intercepted cherts, metabasalts and sheared ultramafics of the 3.3-3.35 Ga Kromberg Formation; the sedimentary units of the 3.432 Ga Noisy formation; and the unconformably underlying metabasaltic pillow lavas of the 3.472 Ga Hooggenoeg Formation.Pyrite in quartz-carbonate-veins in the lower diamictite of the Noisy sequence records the largest range and most negative δ34SCDT values so far reported from an Archean terrain (δ34SCDT = - 55.04 to +27.46‰). The Noisy sediments also contain detrital and diagenetic pyrites with a significant variation in δ33S of between -0.62 to +1.4‰ and δ34SCDT of between -7.00 and +12.6‰, interpreted to reflect tectonic exposure of these early sediments to atmospheric - shallow marine conditions. Early marine pyrites from the Kromberg Cherts also display strong positive δ33S values up to +2.50‰ with narrow range in δ34SCDT values (-6.00 to +1.50‰), whereas hydrothermal veins in the basal ultramafic shear zones preserve magmatic values ( 0‰). This study reveals a potential proto-tectonic control on atmospheric, geodynamic and hydrothermal environments available for early sulfate reducing and/or methanogenic microbes in the Paleoarchean.No evidence for microbial sulfate reduction or disproportionation was identified in the Kromberg Cherts, despite previous morphological claims for microbial life. Highly variable and negative δ34SCDT values were found in the Noisy turbidites and Hooggenoeg pillow lava breccia supporting the presence of microbial sulfate reduction in early tectono-sedimentary basins and in the Paleoarchean sub-seafloor, respectively. In light of current controversies surrounding sulfur isotope studies in similar-aged rocks of the Pilbara Craton (West Australia), we argue that microbial elemental sulfur disproportionation was not a preferred metabolic pathway on the Paleoarchean earth. © 2013 Elsevier B.V.
Keywords: Australia; Barberton Greenstone Belt; Pilbara Block; Western Australia; Biogeochemistry; Gallium; Geodynamics; Isotopes; Pyrites; Quartz; Sedimentology; Sulfur compounds; Tectonics; Disproportionations; Greenstone belts; Hydrothermal environment; Multiple sulfur isotopes; Scientific drilling; Sedimentary environment; Sulfate reduction; Sulfur cycling; anoxic conditions; Archean; atmosphere-biosphere interaction; biogeochemistry; chert; detrital deposit; early Earth; metabasalt; pyrite; seafloor; sulfur cycle; sulfur isotope; tectonics; Sulfur

Microbial community analysis of deeply buried marine sediments of the New Jersey shallow shelf (IODP Expedition 313) - Breuker, A.; Stadler, S.; Schippers, A. (FEMS Microbiology Ecology, 2013)
The investigated deeply buried marine sediments of the shallow shelf off New Jersey, USA, are characterized by low organic carbon content and total cell counts of < 107 cells per mL sediment. The qPCR data for Bacteria and Archaea were in the same orders of magnitude as the total cell counts. Archaea and Bacteria occurred in similar 16S rRNA gene copy numbers in the upper part of the sediments, but Bacteria dominated in the lowermost part of the analyzed sediment cores down to a maximum analyzed depth of c. 50 meters below seafloor (mbsf). The bacterial candidate division JS1 and the classes Anaerolineae and Caldinilineae of the Chloroflexi were almost as highly abundant as the total Bacteria. Similarly high dsrA gene copy numbers were found for sulfate reducers. The abundance of the Fe(III) and Mn(IV) reducers comprising Geobacteraceae in the upper c. 15 mbsf correlated with concentrations of manganese and iron in the pore water. The isolated 16S rRNA gene sequences of Archaea in clone libraries could be allocated to the phyla Thaumarchaeota, Euryarchaeota, and Crenarchaeota with 1%, 14%, and 85%, respectively. The typical deep subsurface sediment-associated groups MBG-B, MBG-D, MCG, and SAGMEG were represented in the sediment community. MCG was the dominant group with a high diversity of the isolated 16S rRNA gene sequences. © 2013 Federation of European Microbiological Societies.
cited By 34
Keywords: RNA 16S; abundance; biosphere; data set; gene; manganese; marine sediment; microbial community; organic carbon; polymerase chain reaction; porewater; seafloor; shallow soil; sulfate; archaeon; article; bacterium; biodiversity; Chloroflexi; classification; Crenarchaeota; deep biosphere; Deltaproteobacteria; Euryarchaeota; genetics; IODP; isolation and purification; microbiology; Miscellaneous Crenarchaeotal Group; phylogeny; sea; sediment; sediments; travel; United States; Crenarchaeota; deep biosphere; Euryarchaeota; IODP; Miscellaneous Crenarchaeotal Group; sediments; Archaea; Bacteria; Biodiversity; Chloroflexi; Crenarchaeota; Deltaproteobacteria; Euryarchaeota; Expeditions; Geologic Sediments; New Jersey; Oceans and Seas; Phylogeny; RNA; Ribosomal; 16S; New Jersey; United States; Anaerolineae; Archaea; Bacteria (microorganisms); Chloroflexi; Chloroflexi (class); Crenarchaeota; Euryarchaeota; Geobacteraceae; Lake Victoria marburgvirus

Origin of two Verwey transitions in different generations of magnetite from the Chesapeake Bay impact structure, USA - Mang, C.; Kontny, A. (Journal of Geophysical Research: Solid Earth, 2013)
We observed two different Verwey transition temperatures in fragments of crystalline basement rocks and impact sediments from the Chesapeake Bay impact structure, USA. Our study aims to the question if this feature can be used as shock indicator in impact craters. We distinguished three generations of magnetite. (1) Primary magnetite in crystalline basement rocks has average grain sizes up to several hundreds of micrometers and shows a regular TV at ≈ 121 K. (2) Shocked magnetite occurs in fragments of crystalline basement rocks and also in the suevite and impact breccia. These magnetites show two Verwey transitions - a regular one and a lowerature transition (LTV) at around 89 K. LTV is related to a small grain size fraction, whereas a larger grain size fraction (some hundreds of micrometers) causes the regular TV. The small grain size fraction contains a distinctly higher amount of superficially oxidized material due to the high surface/volume ratio, which causes a decrease of the Verwey transition temperature (LTV). (3) A secondary magnetite generation shows also two Verwey transition temperatures, one at 121 K and a LTV range between 91 and 105 K. The LTV in this generation is also linked to thin oxidized surface layers. This study shows that especially the Verwey transition temperature of small magnetite grains reacts very sensitively to surface oxidation and can therefore not be used as a reliable pressure indicator for impact structures on Earth. Key Points Reduction of Verwey transition due to nonstoichiometry Degree of nonstoichiometry triggered by grain size Surface/volume ratio crucial for reduction of Verwey transition ©2013. American Geophysical Union. All Rights Reserved.
cited By 9

Modern sedimentation patterns in Lake El'gygytgyn, NE Russia, derived from surface sediment and inlet streams samples - Wennrich, V.; Francke, A.; Dehnert, A.; Juschus, O.; Leipe, T.; Vogt, C.; Brigham-Grette, J.; Minyuk, P. S.; Melles, M.; Party, El'gygytgyn Science (Climate of the Past, 2013)

Revisiting wildfires at the K-Pg boundary - Morgan, J.; Artemieva, N.; Goldin, T. (Journal of Geophysical Research: Biogeosciences, 2013)
The discovery of large amounts of soot in clays deposited at the Cretaceous-Paleogene (K-Pg) boundary and linked to the 65 Ma Chicxulub impact crater led to the hypothesis that major wildfires were a consequence of the asteroid impact. Subsequently, several lines of evidence, including the lack of charcoal in North American sites, were used to argue against global wildfires. Close to the impact site fires are likely to be directly ignited by the impact fireball, whereas globally they could be ignited by radiation from the reentry of hypervelocity ejecta. To-date, models of the latter have yet to take into account that ejection - and thus the emission of thermal radiation - is asymmetric and dependent on impact angle. Here, we model: (1) the impact and ejection of material, (2) the ballistic continuation of ejecta around a spherical Earth, and (3) the thermal pulse delivered to the Earth's surface when ejecta reenters the atmosphere. We find that thermal pulses in the downrange direction are sufficient to ignite flora several thousand kilometers from Chicxulub, whereas pulses at most sites in the uprange direction are too low to ignite even the most susceptible plant matter. Our analyses and models suggest some fires were ignited by the impact fireball and ejecta reentry, but that the nonuniform distribution of thermal radiation across the surface of the Earth is inconsistent with the ignition of fires globally as a direct and immediate result of the Chicxulub impact. Instead, we propose that the desiccation of flora by ejecta reentry, as well as the effects of postimpact global cooling/darkness, left much of the terrestrial flora prone to fires, and that the volume of soot in the global K-Pg layer is explained by a combination of syn- and postimpact wildfires. Key Points K-Pg thermal radiation from re-entering ejecta is simulated with a new 3D model Radiation varied with distance and direction from Chicxulub Wildfires were ignited in some directions, but they were not global ©2013. American Geophysical Union. All Rights Reserved.
cited By 41

Magnitude, geomorphologic response and climate links of lake level oscillations at Laguna Potrok Aike, Patagonian steppe (Argentina) - Kliem, P.; Buylaert, J.P.; Hahn, A.; Mayr, C.; Murray, A.S.; Ohlendorf, C.; Veres, D.; Wastegård, S.; Zolitschka, B. (Quaternary Science Reviews, 2013)
Laguna Potrok Aike is a large maar lake located in the semiarid steppe of southern Patagonia known for its Lateglacial and Holocene lake level fluctuations. Based on sedimentary, seismic and geomorphological evidences, the lake level curve is updated and extended into the Last Glacial period and the geomorphological development of the lake basin and its catchment area is interpreted.Abrasion and lake level oscillations since at least 50ka caused concentric erosion of the surrounding soft rocks of the Miocene Santa Cruz Formation and expanded the basin diameter by approximately 1km. A high lake level and overflow conditions of the lake were dated by luminescence methods and tephra correlation to the early Lateglacial as well as to 45ka. The lowest lake level of record occurred during the mid-Holocene. A further lake level drop was probably prevented by groundwater supply. This low lake level eroded a distinct terrace into lacustrine sediments. Collapse of these terraces probably caused mass movement deposits in the profundal zone of the lake. After the mid-Holocene lake level low stand a general and successive transgression occurred until the Little Ice Age maximum; i.e. ca 40m above the local groundwater table. Frequent lake level oscillations caused deflation of emerged terraces only along the eastern shoreline due to prevailing westerly winds. Preservation of eolian deposits might be linked to relatively moist climate conditions during the past 2.5ka.Precisely dated lake level reconstructions in the rain-shadow of the Andes document high Last Glacial and low Holocene lake levels that could suggest increased precipitation during the Last Glacial period. As permafrost in semiarid Patagonia is documented and dated to the Last Glacial period we argue that the frozen ground might have increased surficial runoff from the catchment and thus influenced the water balance of the lake. This is important for investigating the glacial to Holocene latitudinal shift and/or strengthening of the Southern Hemispheric Westerlies by using lake level reconstructions as a means to assess the regional water balance. Our interpretation explains the contradiction with investigations based on pollen data indicating drier climatic conditions for the Last Glacial period. © 2012 Elsevier Ltd.
Keywords: Argentina; Laguna Potrok Aike; Patagonia; Santa Cruz [Argentina]; Catchments; Curve fitting; Deposits; Glacial geology; Groundwater; Permafrost; Rain; Runoff; Salinity measurement; Sedimentary rocks; Soils; Glacial; Holocenes; ICDP-project PASADO; Lacustrine sediments; Lake level fluctuations; Regional water balance; Southern Hemispheric Westerlies; Surrounding soft rock; catchment; data set; geomorphology; groundwater; Last Glacial Maximum; Little Ice Age; luminescence; maar; magnitude; mass movement; Miocene; oscillation; permafrost; precipitation (climatology); semiarid region; Southern Hemisphere; steppe; tephrochronology; transgression; Lakes

Marine incursion events in the Late Cretaceous Songliao Basin: Constraints from sulfur geochemistry records - Huang, Y.; Yang, G.; Gu, J.; Wang, P.; Huang, Q.; Feng, Z.; Feng, L. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2013)
Songliao Basin in NE China developed the most productive oilfield in the world sourced from terrestrial rocks. The main source rock of the basin includes member 1 of the Qingshankou (K2qn1) and members 1 and 2 of the Nenjiang Formation (K2nj1-2). However the exact reasons for the formation of the source rock, especially the K2qn1 are still controversial. Former paleontological and organic geochemical research suggested that organic matter was deposited during marine incursion events of K2qn1 but further geochemical evidence is needed. This paper explores the distinct sulfate levels that distinguish marine from fresh waters of the Songliao paleo-lake. We undertook a systematic investigation the sulfur geochemistry of the sediments from top of member 4 of the Quantou Formation (K1q4) to top of member 1 of the Qingshankou (K2qn1). The ratio of organic carbon to the pyrite sulfur (TOC/PYS) proved the previously suggested saline conditions during the deposition of K2qn1; and the pyrite sulfur isotope indicated that marine incursion may not only have occurred for K2qn1, but also for top of K1q4. The exact time for the beginning of marine incursion is to be determined. The marine incursion within K2qn1 is not strong and partially controlled by the fluctuation of paleo-lake level. The present study will be helpful for understanding the contribution of marine incursion events to the burial of organic carbon in the Songliao paleo-lake, although further studies are still needed. © 2013 Elsevier B.V.
cited By 59
Keywords: Cretaceous; geochemistry; lake level; oil field; organic carbon; paleolimnology; paleontology; source rock; sulfate; sulfur isotope; China; Nen Basin; Songliao Basin

Mass movement deposits in the 3.6 Ma sediment record of Lake El'gygytgyn, Far East Russian Arctic - Sauerbrey, M. A.; Juschus, O.; Gebhardt, A. C.; Wennrich, V.; Nowaczyk, N. R.; Melles, M. (Climate of the Past, 2013)
This paper focuses on the characterization and genesis of mass movement deposits (MMDs) in the Quaternary and Pliocene sediments of Lake El'gygytgyn, Far East Russian Arctic. Three partly overlapping holes were drilled into the 320 m long sediment record at International Continental Scientific Drilling Program (ICDP) Site 5011-1 in the lake basin, recovering the Quaternary almost completely, and the Pliocene down to 3.6 Ma with 52% recovery. Mass movement deposits were investigated in all three cores, based on macroscopical core descriptions, radiographic images, high-resolution magnetic susceptibility and gamma-ray density. Five different types of MMDs were identified: turbidites, grain-flow deposits, debrites, slumps and slides. These are formed by transitional mass movement processes, and thus can be co-generic. An initial slope failure is thought to transform into a debris flow that deforms frontal sediments, partly disintegrates and dilutes into a turbidity flow. Turbidites are by far the most frequent MMD type in the lake center. They occur throughout the record in all pelagic sedimentary facies, but they are thinner in facies formed during cold climate conditions. All other MMDs, by contrast, incise exclusively the pelagic facies deposited during warm climates. In the 123 m thick Quaternary composite sediment record 230 mass movement events are identified, comprising 33% of the sediment length. Turbidites contribute 93% of the number of Quaternary MMDs, but only 35% of their thickness. In the Pliocene sediments between 123 and 320 m, 181 additional mass movement deposits are identified, which constitute ∼33% of the recovered sediments. The mean recurrence interval for MMDs is 11 and 5 ka in the Quaternary and Pliocene, respectively. © Author(s) 2013.
cited By 36
Keywords: debris flow; depositional environment; facies; lacustrine deposit; mass movement; Pliocene; Quaternary; slope failure; turbidite; turbidity; Arctic; Chukchi; Elgygytgyn Lake; Russian Federation

Mechanisms of lake-level change at Laguna Potrok Aike (Argentina) - insights from hydrological balance calculations - Ohlendorf, Christian; Fey, Michael; Gebhardt, Catalina; Haberzettl, Torsten; L{ucke, Andreas; Mayr, Christoph; Sch{abitz, Frank; Wille, Michael; Zolitschka, Bernd (Quaternary Science Reviews, 2013)
Laguna Potrok Aike is an exceptional site in the southern hemisphere's mid-latitudes because it records changes in the hydrological regime through lake-level variations in a continuous, high-resolution sediment record back into the late Pleistocene. In this study, driving forces of lake-level changes at Laguna Potrok Aike are evaluated by means of process studies using data from an extensive multi-year monitoring in and around the lake. Lake-volume changes were calculated with an energy-budget/bulk-transfer approach and translated into lake-level variations, which were then compared to pressure sensor data. Calculated lake levels are in broad agreement with measured data. We hypothesize that on short time scales, lake-level fluctuations are mainly driven by the precipitation-to-evaporation ratio. Apart from changing catchment conditions, relative humidity, precipitation, temperature, wind strength and wind direction have the most important influence on the hydrological balance of the lake. Lake level decreases during periods of persistently high wind speeds from westerly directions, whereas, during periods with more frequent occurrences of easterly winds, it increases. These situations are linked to a strengthening of the Southern Hemispheric Westerlies in the first and more frequent blocking situations in the latter case. Although lake-level changes at Laguna Potrok Aike show some degree of similarity to variations of the El Niño Southern Oscillation (ENSO) and the Southern Hemisphere Annular Mode (SAM), a persistent correspondence remains to be documented.Water chemistry and sediment-trap data suggest that lake-internal carbonate precipitation is highly sensitive to short-term changes in the lake water volume and, thus, to lake-level variations. However, it becomes obvious that the sedimentary carbonate record, representing changes on longer time scales, is not linearly linked to lake-level changes, hence complicating quantitative lake-level reconstructions back in time. We suggest that short-term changes in authigenic carbonate production are mainly driven by changing precipitation/evaporation ratios probably superimposed on longer-term changes in groundwater input that represent a buffered climate signal.Scenario calculations for a period of 60 years show that changes of the controlling meteorological parameters in the range of 15-17% can lead to lake-level changes with a magnitude comparable to the reconstructed Holocene and Lateglacial extreme situations. In addition, modifications in the water-retaining capacity of the lake can also produce large lake-level changes. It is hypothesized that the development or disappearance of permafrost in the catchment of Laguna Potrok Aike during the Last Glacial/Interglacial transition may have changed the water-retaining capacity tremendously. The lake-level reconstructions for Laguna Potrok Aike might express some of the meridional climate variability observed in coupled general circulation model (CGCM) simulations for southern South America for the Last Glacial Maximum (LGM) and the mid Holocene. © 2012 Elsevier Ltd.
Keywords: Argentina; Laguna Potrok Aike; Santa Cruz [Argentina]; Atmospheric pressure; Carbonation; Catchments; Climatology; Digital storage; Groundwater; Lasers; Monitoring; Runoff; Sediment traps; Sedimentology; Authigenic carbonates; Carbonate precipitation; Coupled general circulation models; ICDP-project PASADO; Meteorological parameters; Southern Hemisphere; Southern hemisphere annular modes; Southern south america; carbonate; energy budget; environmental monitoring; evaporation; general circulation model; hydrochemistry; hydrological change; lacustrine environment; mathematical analysis; permafrost; precipitation (chemistry); sediment chemistry; sediment trap; Southern Hemisphere; timescale; volume; wind velocity; Lakes

Microsedimentological characterization using image analysis and μ-XRF as indicators of sedimentary processes and climate changes during Lateglacial at Laguna Potrok Aike, Santa Cruz, Argentina - Jouve, Guillaume; Francus, Pierre; Lamoureux, Scott; Provencher-Nolet, Laurence; Hahn, Annette; Haberzettl, Torsten; Fortin, David; Nuttin, Laurence (Quaternary Science Reviews, 2013)

Modeling East Asian climate and impacts of atmospheric CO2 concentration during the Late Cretaceous (66Ma) - Chen, J.; Zhao, P.; Wang, C.; Huang, Y.; Cao, K. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2013)
Utilizing the Community Climate System Model version 2 from the National Center for Atmospheric Research (NCAR) and the reconstructed paleogeographic data, we simulate East Asian climate in the Late Cretaceous (66Ma) and investigate the impacts of atmospheric CO2 concentration on climate. The simulations show that the large-scale pressure systems and prevailing wind directions showed a remarkable seasonal variation over East Asia at 66Ma, which indicates a monsoon feature over East Asia. The East Asian winter and summer monsoons showed a synchronous variation, that is, a strong (weak) winter monsoon accompanied a strong summer (weak) monsoon. At 66Ma, there was more precipitation over the eastern coasts of Asia and less precipitation in the mid-latitudes of the inland areas, but there was no meiyu rainy belt in the subtropics of the East Asian land like the present climate. Moreover, the simulated Cretaceous climate over East Asia was warmer relative to the present day. Annual mean surface air temperature was higher over Asia at that time and close to the estimation from the geological evidence. In the Late Cretaceous, when atmospheric CO2 concentration is reduced, the East Asia climate has a significant change, with weaker winter and summer monsoons over East Asia. Annual mean surface air temperature and annual total precipitation reduce in most of land and ocean. Negative difference of surface water budget appeared mainly in the eastern part of East Asia, indicating a drier soil surface, while positive differences appeared in the mid-latitudes of central-western Asia, indicating a wetter soil surface. © 2012 Elsevier B.V.
cited By 26
Keywords: air temperature; carbon dioxide; climate effect; climate modeling; climate variation; concentration (composition); Cretaceous; greenhouse gas; monsoon; paleogeography; precipitation (climatology); seasonal variation; water budget; wind direction; Far East

Modern carbon burial in Lake Qinghai, China - Xu, Hai; Lan, Jianghu; Liu, Bin; Sheng, Enguo; Yeager, Kevin M. (Applied Geochemistry, 2013)
The quantification of carbon burial in lake sediments, and carbon fluxes derived from different origins are crucial to understand modern lacustrine carbon budgets, and to assess the role of lakes in the global carbon cycle. In this study, we estimated carbon burial in the sediment of Lake Qinghai, the largest inland lake in China, and the carbon fluxes derived from different origins. We find that: (1) The organic carbon burial rate in lake sediment is approximately 7.23gm-2a-1, which is comparable to rates documented in many large lakes worldwide. We determined that the flux of riverine particulate organic carbon (POC) is approximately 10 times higher than that of dissolved organic carbon (DOC). Organic matter in lake sediments is primarily derived from POC in lake water, of which approximately 80% is of terrestrial origin. (2) The inorganic carbon burial rate in lake sediment is slightly higher than that of organic carbon. The flux of riverine dissolved inorganic carbon (DIC) is approximately 20 times that of DOC, and more than 70% of the riverine DIC is drawn directly and/or indirectly from atmospheric CO2. (3) Both DIC and DOC are concentrated in lake water, suggesting that the lake serves as a sink for both organic and inorganic carbon over long term timescales. (4) Our analysis suggests that the carbon burial rates in Lake Qinghai would be much higher in warmer climatic periods than in cold ones, implying a growing role in the global carbon cycle under a continued global warming scenario. © 2013 Elsevier Ltd.
Keywords: China; Qinghai; Qinghai Lake; Carbon; Carbon dioxide; Global warming; Sediments; Climatic periods; Different origins; Dissolved inorganic carbon; Dissolved organic carbon; Global carbon cycle; Inorganic carbon; Organic carbon burial rates; Particulate organic carbon; carbon budget; carbon cycle; global warming; lacustrine deposit; organic carbon; sediment chemistry; Lakes

Modern isotope hydrology and controls on δD of plant leaf waxes at Lake El'gygytgyn, NE Russia - Wilkie, K. M. K.; Chapligin, B.; Meyer, H.; Burns, S.; Petsch, S.; Brigham-Grette, J. (Climate of the Past, 2013)
Stable isotope data from lipid biomarkers and diatom silica recovered from lake sediment cores hold great promise for paleoclimate and paleohydrological reconstructions. However, these records rely on accurate calibration with modern precipitation and hydrologic processes and only limited data exist on the controls on the -D values for nalkanoic acids from plant leaf waxes. Here we investigate the stable isotopic composition of modern precipitation, streams, lake water and ice cover, and use these data to constrain isotope systematics of the Lake El'gygytgyn Basin hydrology. Compound-specific hydrogen isotope ratios determined from n-alkanoic acids from modern vegetation are compared with modern precipitation and lake core top sediments. Multispecies net (apparent) fractionation values between source water (precipitation) and modern vegetation (e.g., quot;wax/precip mean value is ?107±12 ) agree with previous results and suggest a consistent offset between source waters and the -D values of alkanoic acids. We conclude that although there may be some bias towards a winter precipitation signal, overall -D values from leaf wax n-alkanoic acids record annual average precipitation within the El'gygytgyn Basin. A net fractionation calculated for 200-yr-integrated lake sediments yields quot;30/precip = ?968and can provide robust net apparent fractionation to be used in future paleohydrological reconstructions. © Author(s) 2013. CC Attribution 3.0 License.
cited By 30
Keywords: biomarker; calibration; diatom; hydrogen isotope; ice cover; isotopic analysis; isotopic composition; isotopic ratio; lacustrine deposit; lipid; paleoclimate; paleohydrology; precipitation (climatology); reconstruction; sediment core; silica; wax; Chukchi; Elgygytgyn Lake; Russian Federation

Modern sedimentation patterns in Lake El’gygytgyn, NE Russia, derived from surface sediment and inlet streams samples - Wennrich, V.; Francke, A.; Dehnert, A.; Juschus, O.; Leipe, T.; Vogt, C.; Brigham-Grette, J.; Minyuk, P.S.; Melles, M.; Party, El'gygytgyn Science (Climate of the Past, 2013)
Lake El’gygytgyn/NE Russia holds a continuous 3.58 Ma sediment record, which is regarded as the most long-lasting climate archive of the terrestrial Arctic. Based on multi-proxy geochemical, mineralogical, and granulometric analyses of surface sediment, inlet stream and bedrock samples, supplemented by statistical methods, major processes influencing the modern sedimentation in the lake were investigated. Grain-size parameters and chemical elements linked to the input of feldspars from acidic bedrock indicate a wind-induced two-cell current system as major driver of sediment transport and accumulation processes in Lake El’gygytgyn. The distribution of mafic rock related elements in the sediment on the lake floor can be traced back to the input of weathering products of basaltic rocks in the catchment. Obvious similarities in the spatial variability of manganese and heavy metals indicate sorption or co-precipitation of these elements with Fe and Mn hydroxides and oxides. But the similar distribution of organic matter and clay contents might also point to a fixation to organic components and clay minerals. An enrichment of mercury in the inlet streams might be indicative of neotectonic activity around the lake. The results of this study add to the fundamental knowledge of the modern lake processes of Lake El’gygytgyn and its lake-catchment interactions, and thus, yield crucial insights for the interpretation of paleo-data from this unique archive. © Author(s) 2013.
cited By 24

Origin and significance of diagenetic concretions in sediments of Laguna Potrok Aike, southern Argentina - Vuillemin, A.; Ariztegui, D.; De Coninck, A.S.; L{ucke, A.; Mayr, C.; Schubert, C.J. (Journal of Paleolimnology, 2013)
Authigenic minerals can form in the water column and sediments of lakes, either abiotically or mediated by biological activity. Such minerals have been used as paleosalinity and paleoproductivity indicators and reflect trophic state and early diagenetic conditions. They are also considered potential indicators of past and perhaps ongoing microbial activity within sediments. Authigenic concretions, including vivianite, were described in late glacial sediments of Laguna Potrok Aike, a maar lake in southernmost Argentina. Occurrence of iron phosphate implies specific phosphorus sorption behavior and a reducing environment, with methane present. Because organic matter content in these sediments was generally low during glacial times, there must have been alternative sources of phosphorus and biogenic methane. Identifying these sources can help define past trophic state of the lake and diagenetic processes in the sediments. We used scanning electron microscopy, phosphorus speciation in bulk sediment, pore water analyses, in situ ATP measurements, microbial cell counts, and measurements of methane content and its carbon isotope composition (δ13CCH4) to identify components of and processes in the sediment. The multiple approaches indicated that volcanic materials in the catchment are important suppliers of iron, sulfur and phosphorus. These elements influence primary productivity and play a role in microbial metabolism during early diagenesis. Authigenic processes led to the formation of pyrite framboids and revealed sulfate reduction. Anaerobic oxidation of methane and shifts in pore water ion concentration indicated microbial influence with depth. This study documents the presence of active microbes within the sediments and their relationship to changing environmental conditions. It also illustrates the substantial role played by microbes in the formation of Laguna Potrok Aike concretions. Thus, authigenic minerals can be used as biosignatures in these late Pleistocene maar sediments. © 2013 Springer Science+Business Media Dordrecht.
Keywords: Argentina; Laguna Potrok Aike; Santa Cruz [Argentina]; diagenesis; environmental conditions; late glacial; maar; metabolism; methane; microbial activity; paleoproductivity; paleosalinity; phosphorus; porewater; pyrite; scanning electron microscopy; sorption; vivianite; water column

Moho depth determination from waveforms of microearthquakes in the West Bohemia/Vogtland swarm area - Hrubcov'a, Pavla; Vavryčuk, V'aclav; Bouškov'a, Alena; Hor'alek, Josef (Journal of Geophysical Research: Solid Earth, 2013)
The West Bohemia/Vogtland area is known for its increased geodynamic activity with reoccurrence of intraplate earthquake swarms. Previous geophysical studies, namely active and passive seismic investigations, revealed a high velocity lower crust in this area with increased reflectivity. To refine this result and retrieve a more detailed structure of the deep crust and the Moho discontinuity, we analyzed waveforms of local microearthquakes that occurred in this area during the 2008 swarm. The waveforms of earthquakes were grouped into clusters with similar focal mechanisms, and the clusters were processed separately. We developed a new multiazimuthal approach in data processing to increase resolution of Moho phases in the waveforms. We applied the waveform cross-correlation of the P and S waves, and rotated, aligned, and stacked the seismograms to extract the Moho SmS, PmP, and PmS reflected/converted phases. These phases were inverted for laterally varying Moho depth by ray tracing and a grid search inversion algorithm. The model retrieved was verified using modeling of full waveforms computed by the discrete wave number method. The multiazimuthal approach reveals details in the velocity structure of the crust/mantle transition at each station. Instead of a single interface with a sharp velocity contrast, the inversion indicates a reflective zone at Moho depths with one or two strongly reflective interfaces, which is in agreement with the zone interpreted by previous investigations. The thickness of the zone varies from 2 to 4 km within the depth range of 27-31.5 km and is delimited by reflections from its top and bottom boundaries, sometimes with strong reflectors within the zone. The average Vp/Vs ratio determined from the Moho reflections and conversions is 1.73. Key Points Moho topography from waveforms of local microearthquakes New multi-azimuthal approach to reveal details of the crust/mantle transition Combined data processing, ray tracing, discrete wave-number and grid search ©2012. American Geophysical Union. All Rights Reserved.
Keywords: Bohemia; Bohemian Massif; Czech Republic; Germany; Vogtland; crustal structure; focal mechanism; lower crust; microearthquake; modeling; Moho; P-wave; S-wave; seismicity; velocity structure; waveform analysis

Morphochemistry of patterns produced by mixing of rhyolitic and basaltic melts - Morgavi, D.; Perugini, D.; De Campos, C.P.; Ertel-Ingrisch, W.; Dingwell, D.B. (Journal of Volcanology and Geothermal Research, 2013)
In this work we present the results of time series experiments performed by mixing basaltic and rhyolitic melts at high temperature using a device recently developed to trigger chaotic dynamics in a mixing system. The morphology of mixing patterns is quantified at different times by measuring their fractal dimension and a linear relationship is derived between mixing time and morphological complexity. The complexity of mixing patterns is also compared to the degree of homogenization of chemical elements during mixing and empirical relationships are established between the fractal dimension and the temporal variation of concentration variance of elements.New concepts and tools to study the magma mixing process unfold from the experimental results presented in this work. The first one is that the mixing patterns are fractals and they can be quantified by measuring their fractal dimension. This represents a further step in the quantification of the magma mixing process. The second outcome is that the relationship between the fractal dimension of the mixing patterns and mixing time is linear. This has important volcanological implications as the analyses of the morphology of mixing patterns in volcanic rocks can be complemented by experiments to build a new chronometer to estimate the mixing-to-eruption time. A further result from this work is the relationship between the fractal dimension of mixing patterns and concentration variance of chemical elements. This represents the first morphochemical study in igneous petrology bringing with it the potential to infer the relative mobility of chemical elements during the time progression of mixing by analyzing the morphology of mixing patterns in the rocks. © 2012.
cited By 17
Keywords: Basaltic melts; Chaotic dynamics; Empirical relationships; High temperature; Linear relationships; Magma mixing; Mixing system; Mixing time; Morphological complexity; Relative mobility; Rhyolitic; Rhyolitic melts; Temporal variation; Time-series experiments; Chemical elements; Experiments; Fractal dimension; Fractals; Igneous rocks; Morphology; Petrography; Mixing; basalt; concentration (composition); element mobility; experimental study; high temperature; igneous geochemistry; magma chemistry; mixing ratio; morphometry; rhyolite; temporal variation; volcanology

Multivariate statistic and time series analyses of grain-size data in quaternary sediments of Lake El'gygytgyn, NE Russia - Francke, A.; Wennrich, V.; Sauerbrey, M.; Juschus, O.; Melles, M.; Brigham-Grette, J. (Climate of the Past, 2013)
Lake El'gygytgyn, located in the Far East Russian Arctic, was formed by a meteorite impact about 3.58 Ma ago. In 2009, the International Continental Scientific Drilling Program (ICDP) at Lake El'gygytgyn obtained a continuous sediment sequence of the lacustrine deposits and the upper part of the impact breccia. Here, we present grain-size data of the past 2.6 Ma. General downcore grain-size variations yield coarser sediments during warm periods and finer ones during cold periods. According to principal component analysis (PCA), the climate-dependent variations in grain-size distributions mainly occur in the coarse silt and very fine silt fraction. During interglacial periods, accumulation of coarser material in the lake center is caused by redistribution of clastic material by a wind-induced current pattern during the ice-free period. Sediment supply to the lake is triggered by the thickness of the active layer in the catchment and the availability of water as a transport medium. During glacial periods, sedimentation at Lake El'gygytgyn is hampered by the occurrence of a perennial ice cover, with sedimentation being restricted to seasonal moats and vertical conduits through the ice. Thus, the summer temperature predominantly triggers transport of coarse material into the lake center. Time series analysis that was carried out to gain insight into the frequency of the grain-size data showed variations predominately on 98.5, 40.6, and 22.9 kyr oscillations, which correspond to Milankovitch's eccentricity, obliquity and precession bands. Variations in the relative power of these three oscillation bands during the Quaternary suggest that sedimentation processes at Lake El'gygytgyn are dominated by environmental variations caused by global glacial-interglacial variations (eccentricity, obliquity), and local insolation forcing and/or latitudinal teleconnections (precession), respectively. ©Author(s) 2013.
cited By 33
Keywords: breccia; eccentricity; grain size; lacustrine deposit; meteorite; multivariate analysis; obliquity; principal component analysis; Quaternary; research program; sediment property; teleconnection; time series analysis; Chukchi; Elgygytgyn Lake; Russian Federation

New research results of the ries suevite [Neue forschungsergebnisse am riessuevit] - Meyer, C. (Zeitschrift der Deutschen Gesellschaft fur Geowissenschaften, 2013)
The processes of formation and transport of particles in suevite during impact crater formation remain poorly understood. This paper gives a summary of the investigations at the 14.6 Ma old, 25 km wide N{ordlinger Ries Crater in Southern Germany, performed during the last years. The suevite of the Ries Crater occurs in three different geological settings: (1) crater suevite in the central crater cavity inside the inner ring, (2) outer suevite on top of the continuous ejecta blanket, and (3) dikes in the crater basement and in displaced megablocks. For suevite genesis, the following processes have been discussed to-date in literature: (1) fall-back of material into the crater and its periphery upon collapse of an ejecta plume, and (2) horizontal transport of ejected material, akin to (a) an impact melt flow, (b) a pyroclastic flow, or (c) initiated by phreatomagmatic explosion. On the basis of geophysical investigations, numerical models, 3D shape fabrics, modal composition, stereometric and geochemical characteristics fi ve stages will be distinguished for the formation and deposition of the Ries Suevite: (1) an early ejecta plume, (2) a phreatomagmatic explosion after a hiatus, (3) a basal, non-erosive pyroclastic surge, (4) a pyroclastic flow, (5) a second ejecta plume with accretionary lapilli. © 2013 E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Germany.
cited By 2

Noise measurements at seismic array in the drilling site of Bagnolifutura, Campi Flegrei - Petrosino, Simona; Bianco, Francesca; Bobbio, Antonella; Castellano, Mario; Cusano, Paola; Del Pezzo, Edoardo; Galluzzo, Danilo; La Rocca, Mario; Maiello, Veronica (Quaderni di Geofisica, 2013)
In 2012 two seismic surveys were carried out in the area of Bagnolifutura (Campi Flegrei, Naples), with the aim of characterizing the properties of the seismic noise during the drilling activity performed in the framework of the Campi Flegrei Deep Drilling Project (CFDDP; https://sites.google.com/site/ cfddpproject/). During the first survey, which was conducted from 2 to 4 April, before the drilling, seven broadband threecomponent seismometers were installed in two different array configurations. The second survey started on November 26, in concomitance with the drilling operations and fluid injection, and ended on December 5, four days after the end of the drilling, when the maximum depth of 502 m was reached. During this period seven broadband and one short-period three-component sensors were installed. A preliminary spectral analysis was performed on samples of seismic noise; moreover the root mean square of the amplitude of the signals and the polarization parameters were calculated. The preliminary results show similar spectral and polarization features for the data of the two surveys, whereas the amplitude of the seismic noise collected during the second survey is greatly influenced by the bad meteorological conditions. As future development experimental site transfer functions from Nakamura's technique and surface wave dispersion from array techniques will be calculated to obtain the shallow crustal structure. The results corresponding to the different phases of the drilling activity will be compared, with the aim of establishing if significant variations of the medium properties have occurred during the experiment. Moreover the recorded signals will be deeply investigated in order to detect the eventual occurrence of microseismicity induced by fluid injection and to define its features. © 2013 INGV Istituto Nazionale di Geofisica e Vulcanologia.

Observations of the genus Diploneis from Lake Ohrid, Macedonia - Jovanovska, Elena; Nakov, Teofil; Levkov, Zlatko (Diatom Research, 2013)
Lake Ohrid is an important biodiversity hotspot, including diatom diversity and endemism. Numerous, putatively endemic diatom species have been described from the lake, alongside reports of relict taxa otherwise known only as fossils from European Neogene deposits. Diploneis Ehrenberg ex Cleve is considered to be one of the species-rich genera in Lake Ohrid. This study presents a detailed account of Diploneis in Lake Ohrid, providing additional information on some of the infrequently recorded taxa. In addition, sediment core samples from Lake Ohrid were used to provide an historical account of some of the more abundant taxa and to determine the morphological similarity between fossil (core samples) and extant populations. To this end, detailed light and scanning electron microscope observations were carried out to ascertain the identity and describe the morphological variation of Diploneis taxa. As a result, 15 Diploneis taxa from Lake Ohrid are reported with four potentially endemic species described as new: D. parabudayana, D. rotunda, D. pulchra and D. vetusa. Among the remaining taxa, two endemic species (D. heisingeriae Jurilj and D. tavcharii Jurilj) previously described from Lake Ohrid were observed, along with nine widespread species commonly reported throughout Europe and elsewhere. © 2013 The International Society for Diatom Research.
Keywords: Lake Ohrid; biodiversity; diatom; endemic species; endemism; fossil record; new species; sediment core; taxonomy

Observations on Hippodonta (Bacillariophyceae) in selected ancient lakes - Pavlov, Aleksandar; Levkov, Zlatko; Williams, David M.; Edlund, Mark B. (Phytotaxa, 2013)
This study provides an evaluation of the diversity and distribution of taxa belonging to the genus Hippodonta (Bacillariophyceae) in selected ancient lakes from different geographical regions of the world. The lakes considered are: Lakes Ohrid, Prespa and Dojran from Macedonia, Lake Tanganyika, Tanzania, Lake Turkana, Kenya and Lake Baikal, Russia. In total, there are 34 Hippodonta taxa. Of these, 21 are described as new, 20 species and one variety. The primary morphological features of each taxon are provided and formal descriptions are given for all new taxa. The distinctive characters distinguishing similar taxa are noted. The genus is most diverse in Lake Baikal with 13 taxa, of which four are described as new species (Hippodonta acuta, H. certa, H. communis and H. pulchra). Lake Tanganyika has six taxa, all of which are described as new (H. angustata, H. avittatiformis, H. cocquytiae, H. conspicua, H. crassa and H. radiata). Lake Turkana has only one taxon, also described as new (H. minuta). In the Macedonian old tectonic lakes, seven taxa were found in Lake Ohrid, with five described as new (H. abunda, H. humboldtiana, H. latelanceolata, H. naviculiformis and H. subrostrata), five taxa were found in Lake Prespa, all of which are described as new (H. affinis, H. costulatiformis var. densistriata, H. exigua, H. media and H. rostratoides), and three known taxa were found in Lake Dojran. © 2013 Magnolia Press.

Onset of intense permafrost conditions in Northern Eurasia at 2.55 Ma seen in a cryogenic weathering record from Lake El'gygytgyn - Schwamborn, G.; Schirrmeister, L.; Diekmann, B. (Climate of the Past Discussions, 2013)

Oral histories in meteoritics and planetary science-XXIII: Dieter St{offler - Sears, D.W.G. (Meteoritics and Planetary Science, 2013)
In this interview, Dieter St{offler (Fig. 1) describes how his interest in meteorites and impact craters dates from his Ph.D. studies at the University of T{ubingen when it was learned that the Ries crater was formed by impact. A paper by Dieter's advisor, Wolf von Engelhardt, also triggered an interest in meteorites. After graduation, Dieter helped to establish a laboratory for high pressure mineralogy and he examined rocks from the Ries crater, which led to the concept of progressive shock metamorphism. The group also worked on newly returned Apollo samples and guided astronauts over the crater. A year at the NASA Ames Research Center taught Dieter about experimental impact research with a light-gas gun. After a few more years at T{ubingen, Dieter obtained a professorship at the University of M{unster where he created the Institute of Planetology, got involved in planning space missions including comet sample return, and continued high pressure mineralogy in collaboration with colleagues in Freiburg. Through several decades of research, Dieter and colleagues have documented the effects of shock on all the major rock-forming minerals and devised widely accepted schemes for the classification of shocked rocks. After the unification of Germany, Dieter became Director of the Natural History Museum in Berlin, during which he made much progress rebuilding the laboratories and the collections. Dieter also helped to create a museum and research center in the Ries crater. He received the Barringer Award of the Meteoritical Society in 1994 and several prestigious awards in Germany. © 2013 The Meteoritical Society.
cited By 0

Response of methanogenic archaea to Late Pleistocene and Holocene climate changes in the Siberian Arctic - Bischoff, J.; Mangelsdorf, K.; Gattinger, A.; Schloter, M.; Kurchatova, A.N.; Herzschuh, U.; Wagner, D. (Global Biogeochemical Cycles, 2013)
In order to investigate the link between the methane dynamics in permafrost deposits and climate changes in the past, we studied the abundance, composition, and methane production of methanogenic communities in Late Pleistocene and Holocene sediments of the Siberian Arctic. We detected intervals of increased methane concentrations in Late Pleistocene and Holocene deposits along a 42 ka old permafrost sequence from Kurungnakh Island in the Lena Delta (northeast Siberia). Increased amounts of archaeal life markers (intact phospholipid ethers) and a high variety in genetic fingerprints detected by 16S ribosomal ribonucleic acid gene analyses of methanogenic archaea suggest presently living and presumably active methanogenic archaea in distinct layers predominantly in Holocene deposits, but also in deep frozen ground at 17 m depth. Potential methanogenic activity was confirmed by incubation experiments. By comparing methane concentrations, microbial incubation experiments, gene analysis of methanogens, and microbial life markers (intact phospholipid esters and ethers) to already partly degraded membrane lipids, such as archaeol and isoprenoid glycerol dialkyl glycerol tetraethers, we demonstrated that archaeol likely represents a signal of past methanogenic archaea. The archaeol signal was used to reconstruct the response of methanogenic communities to past temperature changes in the Siberian Arctic, and the data suggest higher methane emissions occurred during warm periods, particularly during an interval in the Late Pleistocene and during the Holocene. This new data on present and past methanogenic communities in the Siberian terrestrial permafrost imply that these microorganisms will respond to the predicted future temperature rise in the Arctic with increasing methane production, as demonstrated in previous warmer periods. ©2012. American Geophysical Union. All Rights Reserved.
cited By 39
Keywords: Genetic fingerprints; Holocene climate change; Lipid biomarkers; Methane concentrations; Methanogenic activity; Methanogenic archaea; Methanogenic community; Temperature changes; Deposits; Ethers; Experiments; Genes; Glycerol; Methanation; Methane; Methanogens; Permafrost; Phospholipids; RNA; Sediments; Soils; Climate change; biomarker; climate variation; concentration (composition); Holocene; lipid; methane; methanogenesis; paleoclimate; permafrost; Pleistocene; prokaryote; Arctic; Kurungnakh Island; Lena Delta; Russian Federation; Sakha; Siberia

Time evolution of chemical exchanges during mixing of rhyolitic and basaltic melts - Morgavi, D.; Perugini, D.; Campos, C.P.; Ertel-Ingrisch, W.; Dingwell, D.B. (Contributions to Mineralogy and Petrology, 2013)
We present the first set of chaotic mixing experiments performed using natural basaltic and rhyolitic melts. The mixing process is triggered by a recently developed apparatus that generates chaotic streamlines in the melts, mimicking the development of magma mixing in nature. The study of the interplay of physical dynamics and chemical exchanges between melts is carried out performing time series mixing experiments under controlled chaotic dynamic conditions. The variation of major and trace elements is studied in detail by electron microprobe and Laser Ablation ICP-MS. The mobility of each element during mixing is estimated by calculating the decrease in the concentration variance in time. Both major and trace element variances decay exponentially, with the value of exponent of the exponential function quantifying the element mobility. Our results confirm and quantify how different chemical elements homogenize in the melt at differing rates. The differential mobility of elements in the mixing system is considered to be responsible for the highly variable degree of correlation (linear, nonlinear, or scattered) of chemical elements in many published inter-elemental plots. Elements with similar mobility tend to be linearly correlated, whereas, as the difference in mobility increases, the plots become progressively more nonlinear and/or scattered. The results from this study indicate that the decay of concentration variance is in fact a robust tool for obtaining new insights into chemical exchanges during mixing of silicate melts. Concentration variance is (in a single measure) an expression of the influence of all possible factors (e.g., viscosity, composition, and fluid dynamic regime) controlling the mobility of chemical elements and thus can be an additional petrologic tool to address the great complexity characterizing magma mixing processes. © 2013 Springer-Verlag Berlin Heidelberg.
cited By 37
Keywords: chaotic dynamics; concentration (composition); element mobility; experimental study; magma chemistry; mixing; rhyolite; tectonic evolution; tectonic setting; time series analysis

Ries crater and suevite revisited-Observations and modeling Part I: Observations - St{offler, D.; Artemieva, N.A.; W{unnemann, K.; Reimold, W.U.; Jacob, J.; Hansen, B.K.; Summerson, I.A.T. (Meteoritics and Planetary Science, 2013)
We report results of an interdisciplinary project devoted to the 26 km-diameter Ries crater and to the genesis of suevite. Recent laboratory analyses of crater suevite occurring within the central crater basin and of outer suevite on top of the continuous ejecta blanket, as well as data accumulated during the past 50 years, are interpreted within the boundary conditions imposed by a comprehensive new effort to model the crater formation and its ejecta deposits by computer code calculations (Artemieva et al. 2013). The properties of suevite are considered on all scales from megascopic to submicroscopic in the context of its geological setting. In a new approach, we reconstruct the minimum/maximum volumes of all allochthonous impact formations (108/116 km3), of suevite (14/22 km3), and the total volume of impact melt (4.9/8.0 km3) produced by the Ries impact event prior to erosion. These volumes are reasonably compatible with corresponding values obtained by numerical modeling. Taking all data on modal composition, texture, chemistry, and shock metamorphism of suevite, and the results of modeling into account, we arrive at a new empirical model implying five main consecutive phases of crater formation and ejecta emplacement. Numerical modeling indicates that only a very small fraction of suevite can be derived from the primary ejecta plume, which is possibly represented by the fine-grained basal layer of outer suevite. The main mass of suevite was deposited from a secondary plume induced by an explosive reaction (fuel-coolant interaction) of impact melt with water and volatile-rich sedimentary rocks within a clast-laden temporary melt pool. Both melt pool and plume appear to be heterogeneous in space and time. Outer suevite appears to be derived from an early formed, melt-rich and clast-poor plume region rich in strongly shocked components (melt ≫ clasts) and originating from an upper, more marginal zone of the melt pool. Crater suevite is obviously deposited from later formed, clast-rich and melt-poor plumes dominated by unshocked and weakly shocked clasts and derived from a deeper, central zone of the melt pool. Genetically, we distinguish between primary suevite which includes dike suevite, the lower sublayer of crater suevite, and possibly a basal layer of outer suevite, and secondary suevite represented by the massive upper sublayer of crater suevite and the main mass of outer suevite. © The Meteoritical Society, 2013.
cited By 121

Magnetopolarity zone and geological age of the Nenjiang Formation at the CCSD-SK-1 drill core in the Songliao Basin - Meng, QA; Huang, QH; Wan, XQ; Deng, CL; He, HY (Journal of Stratigraphy, 2013)

Testing the ureilite projectile hypothesis for the El'gygytgyn impact: Determination of siderophile element abundances and Os isotope ratios in ICDP drill core samples and melt rocks - Goderis, S.; Wittmann, A.; Zaiss, J.; Elburg, M.; Ravizza, G.; Vanhaecke, F.; Deutsch, A.; Claeys, P. (Meteoritics and Planetary Science, 2013)
The geochemical nature of the impactites from International Continental Scientific Drilling Project-El'gygytgyn lake drill core 1C is compared with that of impact melt rock fragments collected near the western rim of the structure and literature data. Concentrations of major and trace elements, with special focus on siderophile metals Cr, Co, Ni, and the platinum group elements, and isotope ratios of osmium (Os), were determined to test the hypothesis of an ureilite impactor at El'gygytgyn. Least squares mixing calculations suggest that the upper volcanic succession of rhyolites, dacites, and andesites were the main contributors to the polymict impact breccias. Additions of 2-13.5 vol% of basaltic inclusions recovered from drill core intervals between 391.6 and 423.0 mblf can almost entirely account for the compositional differences observed for the bottom of a reworked fallout deposit at 318.9 mblf, a polymict impact breccia at 471.4 mblf, and three impact melt rock fragments. However, the measured Os isotope ratios and slightly elevated PGE content (up to 0.262 ng g-1 Ir) of certain impactite samples, for which the CI-normalized logarithmic PGE signature displays a relatively flat (i.e., chondritic) pattern, can only be explained by the incorporation of a small meteoritic contribution. This component is also required to explain the exceptionally high siderophile element contents and corresponding Ni/Cr, Ni/Co, and Cr/Co ratios of impact glass spherules and spherule fragments that were recovered from the reworked fallout deposits and from terrace outcrops of the Enmyvaam River approximately 10 km southeast of the crater center. Mixing calculations support the presence of approximately 0.05 wt% and 0.50-18 wt% of ordinary chondrite (possibly type-LL) in several impactites and in the glassy spherules, respectively. The heterogeneous distribution of the meteoritic component provides clues for emplacement mechanisms of the various impactite units. © The Meteoritical Society, 2013.
cited By 15

The 14 April 2012 Koyna Earthquake of Mw 4.8: Insights into active tectonics of the Koyna region - Shashidhar, D.; Rao, N.P.; Srinagesh, D.; Gupta, H.; Satyanarayana, H.V.S.; Suresh, G.; Satish, A. (Journal of Seismology, 2013)
The 14 April 2012 earthquake of Mw 4.8 is the best monitored event in the Koyna region, a globally significant site of reservoir triggered seismicity in western India. Hence, investigation of this event assumes great importance, also considering its epicentral location close to that of the 1967 Koyna earthquake of M 6.3, the world's largest reservoir triggered earthquake. Inversion of P-wave amplitude data along with the first motion polarities at 30 digital seismic stations provides a well-constrained strike-slip type focal mechanism solution, similar to that of the 1967 earthquake. The mechanism is further confirmed by moment tensor inversion of 3-component waveform data recorded at the three nearest broadband stations. The depth distribution of the aftershocks clearly delineates a NNE-SSW trending fault plane dipping about 78° to the WNW and coinciding with the trend of the Donachiwada fault, as well as the left-lateral fault plane of the focal mechanism solution obtained. The precise location, focal mechanism and the seismicity distribution from our dense network indicate that the activity in the Koyna region is mainly controlled by the NNE-SSW trending Donachiwada (D) fault zone rather than the Koyna River Fault Zone (KRFZ) on the west as suggested previously. © 2013 Springer Science+Business Media Dordrecht.
cited By 18
Keywords: active fault; aftershock; earthquake event; fault zone; focal mechanism; moment tensor; reservoir-induced seismicity; seismotectonics; India; Koyna; Maharashtra; Warna

The exploratory study of the colorimetry index reflect the paleoclimate–As the Late Cretaceous Turonian of the Songliao Basin for example (in Chinese with English abstract);[色度学指标反映古气候的探索研究––以松辽盆地晚白垩世土伦阶(Turonian)为例] - Zhao, B.; Wang, Y.; Wu, D.; Hang, Y. (Jilin Geology, 2013)

The future of geothermal energy: The shale gas analogy significant electrical EGS resource areas in the US - Blackwell, D.; Frone, Z.; Richards, M. (Transactions - Geothermal Resources Council, 2013)
The geothermal industry has been referred to as mature because of the length of time the industry has been producing electricity and the level of technology involved in projects. The same could have been stated about the oil and gas industry in the early 2000's. Yet both industries are continuously trying to advance through research involving resource understanding, technology advances, and technique development. The shale gas play is an outcome of this advancement by the oil and gas industry, taking approximately 20 years to reach the current level of intensive and successful development characterized by using uniform techniques and standards applied to broad areas of similar resource types. In the geothermal industry Enhanced Geothermal Systems (EGS) have been conceptualized for over 40 years and are now starting the initial development phase in a few sites worldwide. Geothermal Energy could follow a track analogous to the oil and gas industry and reach large scale development in 20 years if it learns from the shale play process and addresses the key factors that will enable it to succeed on a large scale. The factors are related to identifying and characterizing the large-scale thermal resources in the upper 3 to 4 km and developing the ability to access the heat-in-place. Accessing the heat in place includes a grid to transport the energy to market and a supply of water. For near-term successful research and development these crucial factors must be maximized. This paper addresses the locations where EGS research and development activities might be optimal over the near term to facilitate development over the longer term.
cited By 5
Keywords: EGS; Enhanced geothermal systems; Gulf coast; Haynesville shales; Raton Basin; Shale gas; Snake river plains; Cascades (fluid mechanics); Gas industry; Geothermal fields; Geothermal wells; Research; Shale

The last Glacial-Interglacial transition in Patagonia, Argentina: The stable isotope record of bulk sedimentary organic matter from Laguna Potrok Aike - Zhu, Jiayun; L{ucke, Andreas; Wissel, Holger; M{uller, Daniela; Mayr, Christoph; Ohlendorf, Christian; Zolitschka, Bernd (Quaternary Science Reviews, 2013)
An investigation of stable isotope (δ13CTOC and δ15NTN) and elemental parameters (TOC, TN contents and TOC/TN ratios) of bulk organic matter (<200μm) from sediment cores recovered from the Patagonian lake Laguna Potrok Aike (Argentina) in the framework of the ICDP deep drilling project PASADO provided insights into past changes in lake primary productivity and environmental conditions in South Patagonia throughout the last Glacial-Interglacial transition. Stratigraphically constrained cluster analyses of all proxy parameters suggest four main phases. From ca 26,100 to 17,300cal.yearsBP, lacustrine phytoplankton was presumably the predominant organic matter source in an aquatic environment with low primary productivity rates. At around 17,300cal.years BP, abrupt and distinct shifts of isotopic and elemental values indicate that the lacustrine system underwent a rapid reorganization. Lake primary productivity (phytoplankton and aquatic macrophytes) shows higher levels albeit with large variations during most of the deglaciation until 13,000cal.yearsBP. The main causes for this development can be seen in improved growing conditions for primary producers because of deglacial warming in combination with expedient availability of nutrients and likely calm wind conditions. After 13,000cal.yearsBP, decreased δ13CTOC values, TOC, TN contents and TOC/TN ratios indicate that the lake approached a new state with reduced primary productivity probably induced by unfavourable growing conditions for primary producers like strengthened winds and reduced nutrient availability. The steady increase in δ15NTN values presumably suggests limitation of nitrate supply for growth of primary producers resulting from a nutrient shortage after the preceding phase with high productivity. Nitrate limitation and consequent decreased lacustrine primary productivity continued into the early Holocene (10,970-8400cal.yearsBP) as reflected by isotopic and elemental values. © 2012 Elsevier Ltd.
Keywords: Argentina; Laguna Potrok Aike; Patagonia; Santa Cruz [Argentina]; Biogeochemistry; Biological materials; Cluster analysis; Isotopes; Lakes; Nitrates; Nutrients; Organic compounds; Photosynthesis; Sedimentology; ICDP; Lake sediments; Last deglaciation; PASADO; Primary productivity; South America; Stable carbon and nitrogen isotopes; carbon isotope; cluster analysis; deglaciation; environmental conditions; glacial-interglacial cycle; growing season; Last Glacial Maximum; macrophyte; nitrogen isotope; organic matter; phytoplankton; primary production; proxy climate record; sediment chemistry; sediment core; stable isotope; Phytoplankton

The motion decoupled delivery system: A new deployment system for downhole tools is tested at the New Jersey margin - Flemings, P.B.; Polito, P.J.; Pettigrew, T.L.; Iturrino, G.J.; Meissner, E.; Aduddell, R.; Brooks, D.L.; Hetmaniak, C.; Huey, D.; Germaine, J.T.; Norris, R.D.; Wilson, P.A.; et al. (Scientific Drilling, 2013)
cited By 1

Thermo-hydro-mechanical sand production model in hydrate-bearing sediments - Uchida, S.; Klar, A.; Charas, Z.; Yamamoto, K. (International Workshop on Geomechanics and Energy: The Ground as Energy Source and Storage, 2013)
A better understanding of the behavior of hydrate-bearing sediments during gas extraction is a vital step towards realization of commercially viable gas production for the future. In 2007, the world first trial of gas production from hydrate-bearing sediments by depressurization method was conducted at the Mallik gas hydrate site, located in the Mackenzie Delta of Northwest Territories, Canada. However, the operation encountered a large amount of sand migration into the well, a phenomenon known as sand production, and thus was terminated after 24 hours. This incident highlights the importance of development of hydro-mechanical sand production model within hydrate-bearing sediments and understanding of the behavior of hydrate-bearing sediments with the effect of sand production during gas extraction. This extended abstract provides a formulation for the sand production including grain flow and hydraulic dispersion effect. A formulation is fully-coupled such that the sand production affects fluid pressures, saturations and temperature. In addition, the effective stress reduction due to grain detachment is incorporated. This results in further deformation of hydrate-bearing sediments, which may need to be considered for stability of the wellbore.
cited By 15
Keywords: Bearings (machine parts); Extraction; Geomechanics; Hydration; Production engineering; Sand; Sediments; Depressurization methods; Dispersion effect; Effective stress; Extended abstracts; Further deformations; Gas extractions; Gas productions; Hydro-mechanical; Gas hydrates

Three-dimensional magnetotelluric inversion in practice-the electrical conductivity structure of the San Andreas fault in central California - Tietze, K.; Ritter, O. (Geophysical Journal International, 2013)
3-D inversion techniques have become a widely used tool in magnetotelluric (MT) data interpretation. However, with real data sets, many of the controlling factors for the outcome of 3-D inversion are little explored, such as alignment of the coordinate system, handling and influence of data errors and model regularization. Here we present 3-D inversion results of 169 MT sites from the central San Andreas Fault in California. Previous extensive 2-D inversion and 3-D forward modelling of the data set revealed significant along-strike variation of the electrical conductivity structure. 3-D inversion can recover these features but only if the inversion parameters are tuned in accordance with the particularities of the data set. Based on synthetic 3-D data we explore the model space and test the impacts of a wide range of inversion settings. The tests showed that the recovery of a pronounced regional 2-D structure in inversion of the complete impedance tensor depends on the coordinate system. As interdependencies between data components are not considered in standard 3-D MT inversion codes, 2-D subsurface structures can vanish if data are not aligned with the regional strike direction. A priori models and data weighting, that is, how strongly individual components of the impedance tensor and/or vertical magnetic field transfer functions dominate the solution, are crucial controls for the outcome of 3-D inversion. If deviations from a prior model are heavily penalized, regularization is prone to result in erroneous and misleading 3-D inversion models, particularly in the presence of strong conductivity contrasts. A 'good' overall rms misfit is often meaningless or misleading as a huge range of 3-D inversion results exist, all with similarly 'acceptable' misfits but producing significantly differing images of the conductivity structures. Reliable and meaningful 3-D inversion models can only be recovered if data misfit is assessed systematically in the frequency-space domain. © The Authors 2013 Published by Oxford University Press on behalf of The Royal Astronomical Society.
cited By 87
Keywords: Continental margins: transforms; Crustal structure; Geomagnetic induction; Inverse theory; Magnetotelluric; North America; Data processing; Electric conductivity; Geomagnetism; Magnetotellurics; Recovery; Strike-slip faults; Structural geology; Tensors; Three dimensional; continental margin; crustal structure; data inversion; electrical conductivity; fault zone; geomagnetic field; magnetotelluric method; three-dimensional modeling; California; San Andreas; United States

Three-dimensional seismic velocity model of the west Bohemia/Vogtland seismoactive region - Růžek, Bohuslav; Hor'alek, Josef (Geophysical Journal International, 2013)
In this paper, we present a smooth 3-D seismic model WB2012 for theWest Bohemia/Vogtland earthquake swarm region derived by means of seismic tomography. Inverted data were represented by a set of 2920 P-wave traveltimes from controlled shots fired in a framework of different experiments and a set of 11339 P- and S-wave arrival times from 661 local earthquakes between 1991 December and 2010 March. We used a standard tomographic approach for independent calculation of P- and S-wave velocity fields in a rectangular grid whose size was 1 km in all coordinates. The traveltimes and rays were calculated by a numerical solution of the eiconal equation. While locating seismic events, our new WB2012 model yielded arrival time residuals on average by 13 per cent lower and hypocentre depths by 0.95 km shallower compared to the locations of the foci in the standard 1-D vertically inhomogeneous isotropic velocity model of the West Bohemia swarm region WB2005. Further, we converted the Pand S-wave velocities to the bulk modulus K and Poisson's ratio ν. The bulk modulus ( 40- 70 GPa) correlates acceptably with the tectonic and geological structure of the area. The anomalously low values of the Poisson's ratio ( 0.15) are typical for the most active focal zones of Nov'y Kostel and Lazy in West Bohemia. © The Authors 2013. Published by Oxford University Press on behalf of The Royal Astronomical Society.
Keywords: Bohemia; Czech Republic; Germany; Vogtland; Earthquakes; Elastic moduli; Poisson ratio; Seismic waves; Seismographs; Shear waves; Velocity; Wave propagation; Body waves; Controlled-source seismologies; Crustal structure; Europe; Seismic tomography; arrival time; body wave; bulk modulus; crustal structure; earthquake hypocenter; earthquake swarm; isotropy; P-wave; Poisson ratio; S-wave; seismic data; seismic source; seismic tomography; seismic velocity; seismic zone; seismology; tectonic setting; three-dimensional modeling; Three dimensional

Timing of deposition and deformation of the Moodies Group (Barberton Greenstone Belt, South Africa): Very-high-resolution of Archaean surface processes - Heubeck, Christoph; Engelhardt, Jonathan; Byerly, Gary R.; Zeh, Armin; Sell, Bryan; Luber, Tim; Lowe, Donald R. (Precambrian Research, 2013)
Thin and largely discontinuous volcanic tuff beds in the alluvial, fluvial, and marginal-marine siliciclastic strata of the Middle Archaean Moodies Group, Barberton Greenstone Belt (BGB), contain rare to abundant zircon. Dating of magmatic zircon grains from five tuff beds and one cross-cutting dike yield ages which span the entire spectrum of BGB history from ca. 3550. Ma to 3215. Ma and show variable degrees of post-depositional alteration until ca. 2500. Ma. The youngest pristine zircon grains in all tuff samples analyzed by CA-ID-TIMS (Chemical-Abrasion Ion-Dissolution Thermal Ion Mass Spectrometry) yield upper intercept and Concordia ages between 3227.6. ±. 0.3 and 3216. ±. 0.3. Ma, and those grains analyzed by LA-SF-ICP-MS (Laser Ablation-Sector Field-Inductively Coupled Plasma-Mass Spectrometry) and SHRIMP (Sensitive High-Resolution Ion Microprobe) yield ages between 3228. ±. 9 and 3214. ±. 9. Ma. Most of these ages are either identical (within error) or significantly older than a CA-ID-TIMS age of 3223.4. ±. 0.3. Ma, obtained from zircon grains of a tuff horizon of the Schoongezicht Formation at the top of the underlying Fig Tree Group. We interpret this age to mark the time of volcanic eruption, whereas the significantly older and overlapping ages of the stratigraphically higher Moodies tuff zircon grains point either to a high degree of magmatic inheritance and/or a detrital contribution from surrounding sedimentary rocks during or after ash-tuff deposition. The minimum age for deposition of Moodies Group sediments and deformation is provided by a LA-ICP-MS zircon U-Pb age of 3219. ±. 9. Ma obtained from an undeformed felsic dike which crosscuts folded Moodies strata. This age overlaps with a precise CA-ID-TIMS U-Pb zircon age of 3216.0. ±. 0.3. Ma obtained from a tuff horizon of the upper Moodies Group. Overall, the new age data collectively imply that the up to 3.7. km-thick, sandstone-dominated Moodies Group was deposited and deformed within <1-14. Ma, and that Moodies strata thus hold the potential to offer a temporal resolution comparable to active- and passive-margin Quaternary strata ( 0.1-1. mm/a). © 2013 Elsevier B.V.
Keywords: Barberton Greenstone Belt; Ficus (angiosperm); alluvial deposit; Archean; deformation; deposition; dike; felsic rock; fluvial deposit; geochronology; sandstone; sedimentary rock; siliciclastic deposit; subsidence; tuff; zircon

Tephrostratigraphic studies on a sediment core from Lake Prespa in the Balkans - Damaschke, M.; Sulpizio, R.; Zanchetta, G.; Wagner, B.; B{ohm, A.; Nowaczyk, N.; Rethemeyer, J.; Hilgers, A. (Climate of the Past, 2013)
A detailed tephrostratigraphic record, which dates back to Marine Isotope Stage (MIS) 5b (ca. 91 kyr), has been established from a 17.76 m long core (Co1215) from Lake Prespa (Macedonia, Albania and Greece). A total of eleven tephra and cryptotephra layers (PT0915-1 to PT0915-11) were identified, using XRF scanning, magnetic susceptibility measurements, and macro- and microscopic inspection of the sediments. The major element composition of glass shards and/or micro-pumice fragments indicates that the tephras and cryptotephras originate from the explosive volcanism of Italy. Eight tephra and cryptotephra layers were correlated with specific volcanic eruptions: the AD 512 eruption of Somma-Vesuvius (1438 cal yr BP), the Mercato eruption of Somma-Vesuvius (8890 ± 90 cal yr BP), the Tufi Biancastri/LN1-LN2 eruption of the Campi Flegrei (14 749 ± 523 cal yr BP and 15 551 ± 621 cal yr BP), the SMP1-e/Y-3 eruption of the Campi Flegrei (30 000-31 000 cal yr BP), the Campanian Ignimbrite/Y-5 eruption of the Campi Flegrei (39 280 ± 110 cal yr BP), the SMP1-a event of Ischia Island (around 44 000 cal yr BP) and the Green Tuff/Y-6 eruption of Pantelleria Island (around 45 000 cal yr BP). One tephra could be attributed to the volcanic activity of Mount Etna, but probably represents an unknown eruption at ca. 60 000 cal yr BP. Cryptotephras PT0915-6 and PT0915-10 remain unclassified so far, but according to the presented age-depth model these would have been deposited around 35 000 and 48 500 cal yr BP, respectively. Some of the tephras and cryptotephras are recognised for the first time in the Balkan region. The tephrostratigraphic work provides important information about ash dispersal and explosion patterns of source volcanoes and can be used to correlate and date geographically distant paleoenvironmental and archaeological archives in the central Mediterranean region. Moreover, the tephrostratigraphic work in combination with radiocarbon and electron spin resonance (ESR) dating is a precondition for paleoclimatic reconstructions inferred from the sediment succession Co1215. © 2013 Author(s).
Keywords: Balkans; Campania [Italy]; Ischia; Italy; Lake Mikri Prespa; Napoli [Campania]; age; archaeology; biostratigraphy; chemical composition; fragmentation; numerical model; paleoenvironment; sediment core; tephrochronology