Radiocarbon chronology of the dsddp core at the deepest floor of the dead sea - Kitagawa, H.; Stein, M.; Goldstein, S.L.; Nakamura, T.; Lazar, B.; Party, DSDDP Scientific (Radiocarbon, 2017)
This study establishes the chronological framework of the sedimentary sequence deposited Dead Sea, ICDP 5017-1, Radiocarbon chronology during the past 50 ka at the deepest part of the Dead Sea (the ICDP 5017-1 site), which was recovered by the Dead Sea Deep Drilling Project (DSDDP) under the auspices of the International Continental Scientific Drilling Program (ICDP). The age-depth model is constructed using 3814C dates of terrestrial plant remains in a composite 150-m-long profile, generated by anchoring 32 marker layers identified in five cores. The sedimentary records at the ICDP 5017-1 site fills gaps in those obtained from the exposed sections at the high margins of the lake, particularly in times of lake-level retreat, and allows for a high-resolution comparison between the lake’s margins and deepest floor. © 2017 by the Arizona Board of Regents on behalf of the University of Arizona.
cited By 27
Keywords: carbon isotope; chronology; Deep Sea Drilling Project; lacustrine environment; lake level; radiocarbon dating; sedimentary sequence; terrestrial environment; Dead Sea

Quantifying the Release of Climate-Active Gases by Large Meteorite Impacts With a Case Study of Chicxulub - Artemieva, N.; Morgan, J.; Party, Expedition 364 Science (Geophysical Research Letters, 2017)
Potentially hazardous asteroids and comets have hit Earth throughout its history, with catastrophic consequences in the case of the Chicxulub impact. Here we reexamine one of the mechanisms that allow an impact to have a global effect–the release of climate-active gases from sedimentary rocks. We use the SOVA hydrocode and model ejected materials for a sufficient time after impact to quantify the volume of gases that reach high enough altitudes ( > 25 km) to have global consequences. We vary impact angle, sediment thickness and porosity, water depth, and shock pressure for devolatilization and present the results in a dimensionless form so that the released gases can be estimated for any impact into a sedimentary target. Using new constraints on the Chicxulub impact angle and target composition, we estimate that 325 ± 130 Gt of sulfur and 425 ± 160 Gt CO2 were ejected and produced severe changes to the global climate. ©2017. American Geophysical Union. All Rights Reserved.
cited By 60

Pyrite in a sulfate-poor Paleoarchean basin was derived predominantly from elemental sulfur: Evidence from 3.2 Ga sediments in the Barberton Greenstone Belt, Kaapvaal Craton - Gali, Aleksandra; Mason, Paul R.D.; Mogoll'on, Jos'e M.; Wolthers, Mari{ette; Vroon, Pieter Z.; Whitehouse, Martin J. (Chemical Geology, 2017)
Multiple sulfur isotope variability in Archean sedimentary rocks provides constraints on the composition of the Earth's earliest atmosphere. The magnitude and sign of mass-independent anomalies reflect not only atmospheric processes, but also transformations due to the Archean marine sulfur cycle prior to preservation into sedimentary pyrite. The processes affecting the Archean marine sulfur cycle and the role of microbial or abiotic redox reactions during pyrite formation remain unclear. Here we combine iron (Fe) and multiple sulfur (S) isotope data in individual pyrite grains with petrographic information and a one-dimensional reactive transport model, to investigate the sources of Fe and S in pyrite formed in a Paleoarchean sedimentary basin. Pyrites were selected from mudstones, sandstones and chert obtained from a drill core in the ca. 3.2 Ga Mapepe and Mendon Formations of the Fig Tree and Onverwacht Groups, respectively, in the Barberton Greenstone Belt, Kaapvaal Craton, South Africa. Pyrite textures and δ56Fe distinguish early-diagenetic pyrite formed with pore-water ferrous iron (disseminated grains with average δ56Fepyrite = 0‰) from late-diagenetic pyrite formed through sulfidation of iron oxide minerals (layered and aggregate forms with average δ56Fepyrite = + 1‰). Mass dependent S isotope variability in pyrite was small (δ34Spyrite ranged from − 1.1 to + 3.3‰) with a correspondingly minor spread in Δ33Spyrite (ranging from + 0.3 to + 2.1‰) and Δ36Spyrite (ranging from − 3.08 to + 0.27‰) that indicates a lack of post-depositional re-working with other distinct sulfur sources. Our combined Fe and S isotope data are most readily explained with pyrite sulfide derived from microbial-reworking of solid elemental S. Iron oxide minerals were necessary to buffer sulfide concentrations and provide favorable conditions for microbial sulfur disproportionation to proceed. The lack of a negative Δ33S signal indicates that pyrite from relatively deep marine diagenetic environments only partially records the products of atmospheric photolysis, consistent with low sulfate concentrations in the Paleoarchean ocean. © 2016
Keywords: Barberton Greenstone Belt; Kaapvaal Craton; Ficus (angiosperm); Earth atmosphere; Iron; Iron oxides; Isotopes; Oxide minerals; Photolysis; Redox reactions; Sedimentary rocks; Sedimentology; Sulfur; Sulfur compounds; Composition of the Earth; Fe isotopes; Greenstone belts; Low sulfate concentrations; Multiple sulfur isotopes; Paleoarchean; Reactive transport modeling; S isotopes; Archean; iron; isotopic fractionation; pyrite; sediment chemistry; sedimentary rock; sulfate; sulfur; sulfur isotope; Pyrites

Progress in the study of paleoclimate change in continental scientific drilling projects - Gao, Yuan; Wang, Chengshan; Huang, Yongjian; Hu, Bin (Earth Science Frontiers, 2017)
Today climate change has caused extensive concern of the whole society. Paleoclimate change studies in geological time (including Quaternary and “Deep Time”), in which continental scientific drilling plays a significant role, provide important references to the current climate change. This paper reviews scientific progresses in the study of paleoclimate change in continental scientific drilling projects. In advantage of the continuous sedimentary records acquired by the continental scientific drilling projects, high-resolution chronostratigraphic framework is established and multiple paleoclimatic proxies are applied. With the aim to decipher the process and mechanism of climate change, progresses have been achieved on paleoclimatic reconstructions on different timescales, detailed studies on rapid climate changes, and precise correlation between marine and terrestrial paleoclimatic records. It is predictable that continental scientific drilling will be more influential in the paleoclimate studies in future, especially in deep-time greenhouse climate studies. © 2017, Editorial Office of Earth Science Frontiers. All right reserved.
Keywords: Greenhouses; Sedimentology; Continental scientific drillings; Greenhouse climates; Paleoclimate studies; Paleoclimates; Paleoclimatic reconstruction; Paleoclimatic record; Rapid climate change; Sedimentary records; Climate change

Preservation and significance of extracellular DNA in ferruginous sediments from Lake Towuti, Indonesia - Vuillemin, Aurèle; Horn, Fabian; Alawi, Mashal; Henny, Cynthia; Wagner, Dirk; Crowe, Sean A.; Kallmeyer, Jens (Frontiers in Microbiology, 2017)
Extracellular DNA is ubiquitous in soil and sediment and constitutes a dominant fraction of environmental DNA in aquatic systems. In theory, extracellular DNA is composed of genomic elements persisting at different degrees of preservation produced by processes occurring on land, in the water column and sediment. Extracellular DNA can be taken up as a nutrient source, excreted or degraded by microorganisms, or adsorbed onto mineral matrices, thus potentially preserving information from past environments. To test whether extracellular DNA records lacustrine conditions, we sequentially extracted extracellular and intracellular DNA from anoxic sediments of ferruginous Lake Towuti, Indonesia. We applied 16S rRNA gene Illumina sequencing on both fractions to discriminate exogenous from endogenous sources of extracellular DNA in the sediment. Environmental sequences exclusively found as extracellular DNA in the sediment originated from multiple sources. For instance, Actinobacteria, Verrucomicrobia, and Acidobacteria derived from soils in the catchment. Limited primary productivity in the water column resulted in few sequences of Cyanobacteria in the oxic photic zone, whereas stratification of the water body mainly led to secondary production by aerobic and anaerobic heterotrophs. Chloroflexi and Planctomycetes, the main degraders of sinking organic matter and planktonic sequences at the water-sediment interface, were preferentially preserved during the initial phase of burial. To trace endogenous sources of extracellular DNA, we used relative abundances of taxa in the intracellular DNA to define which microbial populations grow, decline or persist at low density with sediment depth. Cell lysis became an important additional source of extracellular DNA, gradually covering previous genetic assemblages as other microbial genera became more abundant with depth. The use of extracellular DNA as nutrient by active microorganisms led to selective removal of sequences with lowest GC contents. We conclude that extracellular DNA preserved in shallow lacustrine sediments reflects the initial environmental context, but is gradually modified and thereby shifts from its stratigraphic context. Discrimination of exogenous and endogenous sources of extracellular DNA allows simultaneously addressing in-lake and post-depositional processes. In deeper sediments, the accumulation of resting stages and sequences from cell lysis would require stringent extraction and specific primers if ancient DNA is targeted. © 2017 Vuillemin, Horn, Alawi, Henny, Wagner, Crowe and Kallmeyer.
Keywords: cell DNA; RNA 16S; Acidobacteria; Actinobacteria; Alphaproteobacteria; Article; cell count; Chloroflexi; controlled study; cytolysis; Deltaproteobacteria; DNA base composition; DNA extraction; DNA sequence; high throughput sequencing; hydrothermal vent species; Nitrospirae; nonhuman; phylogenetic tree; phylogeny; Planctomycetes; polymerase chain reaction; population abundance; preservation; sediment; Thaumarchaeota; Thermoplasmatales; Verrucomicrobia

Preliminary description of rocks and alteration in IDDP-2 drill core samples recovered from the Reykjanes geothermal system, Iceland - Zierenberg, Robert A.; Fowler, Andrew P. G.; Fridleifsson, Gudmundur Ó.; Elders, Wilfred A.; Weisenberger, TobiaS. B. (Transactions - Geothermal Resources Council, 2017)
The Iceland Deep Drilling Project (IDDP) well IDDP-2 was drilled to 4,659 m in the seawaterrecharged and basalt-hosted Reykjanes geothermal system in Iceland. Spot drill cores were recovered between drilling depths of 3,648.00 m and 4,657.58 m. Temperature and pressure conditions at the base of IDDP-2 were over 426°C and 340 bar immediately following drilling, exceeding the critical point of seawater (406°C and 298 bar). The IDDP-2 cores are the first samples ever recovered from the supercritical roots of an active basalt-hosted hydrothermal system. We provide some preliminary hand sample descriptions, supplemented where possible by thin section petrography and mineral composition analyses for the IDDP-2 drill cores. The cores recovered between 3,648 m and the bottom of the hole at 4,659 m are from a sheeted dike complex and are generally pervasively altered. Despite the extensive alteration, veining is relatively minor and open space veins are very rare. Veins tend to be discontinuous and anastomosing and lack sharp wall rock contacts. They are interpreted as hydrothermal replacement veins formed in the transition zone between brittle and ductile deformation. Important initial findings include the transition from epidote-actinolite alteration to hornblende hornfels alteration at approximately 3,650 m, and the development of hydrothermal biotite in rocks below ∼4,250 m. Felsic (plagiogranite) segregation veins are not common on the Reykjanes peninsula west of the Hengill volcanic system, but are present in minor amounts in most of the dikes cored below ∼4,300 m. Detailed petrographic and geochemical analysis of the samples is on-going. We have also sampled what appears to be hypersaline supercritical/magmatic brine trapped in pore spaces of porous felsite veins and adjacent wall rock, which manifests as a yellow potassium-iron chloride salt that precipitates on the cut edge of the core as pore fluid evaporates. Some of the core at these depths was stained by hematite that formed on the outer core surface by oxidation of ferrous iron in the formation fluid reacting at elevated temperature with oxygenated surface water used as drilling fluid. Further evidence for supercritical brine is apparent in complex fluid inclusions within quartz that contain multiple solid phases. The drill core samples are of immense scientific value for studying chemical conditions in the supercritical roots of high-enthalpy geothermal resources and submarine hydrothermal systems, with implications for improved understanding of ore-forming processes.
Keywords: Analytical geochemistry; Basalt; Chlorine compounds; Core drilling; Drilling fluids; Drills; Geothermal fields; Geothermal wells; Hematite; Hydraulic structures; Hydrochemistry; Levees; Lithology; Mica; Petrography; Potassium chloride; Recovery; Silicate minerals; Surface waters; Wall rock; Alteration; Drill core; Enhanced geothermal systems; Geothermal systems; Iceland deep drilling projects; Supercritical; Core samples

Periodic 1.5 ka climate variations during MIS 2 in the belt of Southern Hemispheric westerlies - Kliem, Pierre; Baumgarten, Henrike; Gebhardt, Catalina; Hahn, Annette; Ohlendorf, Christian; Zolitschka, Bernd (Quaternary Research (United States), 2017)
Lacustrine sediments retrieved from Laguna Potrok Aike in the framework of the Potrok Aike Maar Lake Sediment Archive Drilling Project (PASADO) offer the possibility to investigate climate variations of the past 51 cal ka BP in Southern Hemispheric midlatitudes, Argentinean Patagonia. This study focuses on short-term cyclicities in the Ca and magnetic susceptibility data sets between 51 and 15 cal ka BP. The record yields a climate pattern with a periodicity of 1.5 ka during Marine Oxygen Isotope Stage 2 (MIS 2) detected in the Southern Hemisphere from 31 to 17 cal ka BP for the first time. MIS 2 is known for constantly cold temperatures, whereas prominent climate variations paced by a 1.5 ka periodicity occurred during MIS 3. Our study documents that minor latitudinal oscillations of the Southern Hemispheric westerlies and the polar easterlies with a 1.5 ka periodicity also took place during MIS 2. However, we assume that because of a major northward displacement of the Southern Hemispheric westerlies, these oscillations did not sufficiently affect the zone of Circumpolar Deep Waters and an increased greenhouse effect by upwelling of CO2-rich deep waters did not occur. This mechanism illustrates why prominent climate events fail to appear during MIS 2. Copyright © University of Washington. Published by Cambridge University Press, 2017.
Keywords: Argentina; Patagonia; Greenhouse effect; Lakes; Magnetic susceptibility; Dansgaard-oeschger events; Frequency Analysis; Laguna potrok aike; Lake sediments; PASADO; Patagonia; climate variation; frequency analysis; lacustrine deposit; marine isotope stage; paleoclimate; Southern Hemisphere; westerly; Sediments

Prediction of the bottom hole geotemperature, formation pressure and formation fracture pressure of the Continental Scientific Drilling of Cretaceous Songliao Basin (SK2) - Qu, Xuejiao; Yang, Liwei; Xue, Xuan; Gao, Youfeng; Wang, Pujun (Earth Science Frontiers, 2017)
The designed depth of SK2 is 6400 m, which is the deepest scientific drilling in the East Asia. Previous studies shows that the Xujiaweizi Fault Depression is located in the high geotemperature area. However the high geotemperature and possible abnormal pressure are the main challenges for continental scientific drilling. Based on a great deal of geological and geophysical data including regional geological survey, petroleum exploration and exploitation and scientific achievements in the Songliao Basin, we predicted the bottom hole temperature, formation pressure and formation fracture pressure of target strata of SK2. According to the relationship between depth and present geotemperatures, geothermal gradients, we predicted the bottom hole geotemperature of SK2 probably range from 238.83℃ to 265.11℃. According to the relationship between depth and formation pressures, and calculated results using DrillWorks, we estimated the formation pressure of Yingcheng Formation, Shahezi Formation and Huoshiling Formation to the bottom of the hole in the range of 30.54-37.72 MPa, 33.22-59.52 MPa, 59.52-67.18 MPa, respectively; and the formation fracture pressure range from 52.35 MPa to 58.62 MPa, from 61.88 MPa to 105.68 MPa, from 104.57 MPa to 118.03 MPa, respectively. © 2017, Editorial Office of Earth Science Frontiers. All right reserved.
Keywords: Forecasting; Geology; Petroleum prospecting; Bottom hole; Bottom hole temperatures; Continental scientific drillings; Cretaceous; Formation pressure; Scientific achievements; Songliao basin; Xujiaweizi Fault Depression; Fracture

Predicting uniaxial compressive strength from empirical relationships between ultrasonic P-wave velocities, porosity, and core measurements in a potential geothermal reservoir, Snake River Plain, Idaho - Kessler, J.A.; Chen, X.; Evans, J.P.; Shervais, J.W. (51st US Rock Mechanics / Geomechanics Symposium 2017, 2017)
Empirical, core-based, predictive correlations for the calculation of uniaxial compressive strength (UCS) were developed from compressive sonic velocity measurements (55 whole core samples) and porosity, density, and unconfined compressive tests (110 whole core samples). The samples were collected at 55 different depths in a 550 m (1800 ft) interval of core from the MH-2 borehole located in southern Idaho, USA. The western Snake River Plain is a known region of high heat flow and the borehole was drilled into a potential geothermal reservoir characterized by artesian flow of high-temperature ( 140°C) fluids from fractured basalt. The UCS values were measured in unconfined compressive tests, density and porosity were measured using a He-pycnometer, and p-wave velocities were measured in a pressure vessel under variable confining pressures. We use correlations between density and p-wave velocity (R2 = 0.91), UCS and porosity (R2 = 0.78), and UCS and p-wave velocity (R2 = 0.79) in a method to calculate calibrated UCS from wireline logs. The impact of this predictive correlation is that UCS can be calculated from as little as a bulk density log when sonic logs and core are not available, greatly increasing the number of wells in which we can obtain a local UCS estimate. © 2017 ARMA, American Rock Mechanics Association.
cited By 0
Keywords: Acoustic wave velocity; Core samples; Geothermal fields; Porosity; Radioactivity logging; Rock mechanics; Seismic waves; Wave propagation; Compressive tests; Empirical relationships; Geothermal reservoir; Predictive correlation; Snake river plains; Ultrasonic P-wave velocity; Uniaxial compressive strength; Variable confining pressures; Compressive strength

Porewater salinity reveals past lake-level changes in Lake Van, the Earth's largest soda lake - Tomonaga, Y.; Brennwald, M.S.; Livingstone, D.M.; Kwiecien, O.; Randlett, M.-E.; Stockhecke, M.; Unwin, K.; Anselmetti, F.S.; Beer, J.; Haug, G.H.; Schubert, C.J.; Sturm, M.; et al. (Scientific Reports, 2017)
In closed-basin lakes, sediment porewater salinity can potentially be used as a conservative tracer to reconstruct past fluctuations in lake level. However, until now, porewater salinity profiles did not allow quantitative estimates of past lake-level changes because, in contrast to the oceans, significant salinity changes (e.g., local concentration minima and maxima) had never been observed in lacustrine sediments. Here we show that the salinity measured in the sediment pore water of Lake Van (Turkey) allows straightforward reconstruction of two major transgressions and a major regression that occurred during the last 250 ka. We observed strong changes in the vertical salinity profiles of the pore water of the uppermost 100 m of the sediments in Lake Van. As the salinity balance of Lake Van is almost at steady-state, these salinity changes indicate major lake-level changes in the past. In line with previous studies on lake terraces and with seismic and sedimentological surveys, we identify two major transgressions of up to +105 m with respect to the current lake level at about 135 ka BP and 248 ka BP starting at the onset of the two previous interglacials (MIS5e and MIS7), and a major regression of about-200 m at about 30 ka BP during the last ice age. © 2017 The Author(s).
cited By 21

Pore structure characterization of the Cretaceous Quantou Formation: Results from microresistivity imaging logs in the second scientific drilling borehole (SK-2 east borehole) Songliao basin, northeast China - Zhao, J.; Zou, C.; Fu, H.; Xiao, L.; Peng, C.; Niu, Y. (Journal of Petroleum Science and Engineering, 2017)
As the main borehole of the China Cretaceous Continental Scientific Drilling Project, the SK-2 east borehole was drilled to obtain in-situ multi-information of geophysics and investigate the paleoclimatic and environmental changes. A study based on continuous geophysical logs facilitates achievement of scientific goals, such as the establishment of the typical petrophysical properties for Songliao basin and other similar basins, analysis of sedimentary environment, resource exploration, geothermal system research, and long-term observation and fluid experiments on deep strata. Both conventional logs and microresistivity imaging logs of the Cretaceous Quantou formation have been acquired. Porosity spectra from microresistivity imaging logs are obtained by using the Archie equation. Based on analysis of porosity spectrum features, we divide the porosity spectra of K1q in the SK-2 east borehole into twelve configurations according to the location and combination of peaks to characterize different pore structure. The porosity spectra of K1q in the SK-2 east borehole are dominated by unimodal distribution indicating more primary porosity. Five layers dominated by unimodal distribution are considered for performing long-term observations and fluid experiments on aspects of depth, thickness or petrophysical properties. By comparing spectrum features, porosity spectrum can be used to reflect the heterogeneity and analyze the pore structure of clastic strata. Layered strata will produce complicated porosity spectra as secondary porosity will. It is better to combine porosity spectra with microresistivity image to study secondary porosity. The decline of the porosity heterogeneity in the SK-2 east borehole is demonstrated by two parameters, φvk and W from porosity spectra, which can indicate the sedimentary environment. Moreover, porosity spectra in clastic strata is favorable for determining lithology and sedimentary environment when combined with microresistivity images. © 2017 Elsevier B.V.
cited By 6
Keywords: Boring; Geophysics; Geothermal fields; Geothermal logging; Lithology; Pore structure; Porosity; Sedimentology; Spectrum analysis; Structural geology; Clastic strata; Continental scientific drillings; Imaging log; Long term observations; Petrophysical properties; Pore structure characterizations; Sedimentary environment; Songliao basin; Well logging; borehole logging; clastic rock; drilling; environmental change; lithology; paleoclimate; porosity; China; Songliao Basin

Pore fluids in Dead Sea sediment core reveal linear response of lake chemistry to global climate changes - Levy, E.J.; Stein, M.; Lazar, B.; Gavrieli, I.; Yechieli, Y.; Sivan, O. (Geology, 2017)
Pore fluids extracted from a 456 m sediment core, recovered within the framework of a multinational and International Continental Scientific Drilling Program (ICDP) co-sponsored effort at the bottom of the terminal Dead Sea, recorded the chemical variations in the deep lake over the past 220 k.y. Mg2+ and Br- were shown to be conservative in the pore fluids, increasing in concentration during interglacial periods, diluting during glacials, and providing excellent proxies for deep lake net water balance changes. Furthermore, the Na/Cl ratio recorded the process of halite precipitation and dissolution induced by these hydrological changes. Mg2+ and Br- records follow a glacialinterglacial pattern, such as observed in atmospheric CO2 concentrations and global sea-surface temperatures, albeit with a phase offset. At the end of the last interglacial (ca. 116 ka), there is a delay in onset of dilution of the deep lake, most likely due to the limnological transition from holomictic to meromictic conditions. The increase in deep lake concentrations at Last Glacial Termination I is delayed as a result of freshwater input into the deep lake during the cooler Younger Dryas period. There is a persistent relationship between precipitation in the watershed and North Atlantic sea-surface temperatures, similar to conditions observed over the past instrumental record. Deviations from the long-term trends occurred during interglacial periods, Marine Isotope Stages MIS 5e and MIS 1, when the deep Dead Sea was significantly diluted, and coincided with Mediterranean sapropel layers S5 and S1. © 2017 The Authors.
cited By 16
Keywords: Atmospheric temperature; Bromine; Carbon dioxide; Climate change; Drilling fluids; Glacial geology; Magnesium; Oceanography; Submarine geophysics; Surface properties; Surface waters; Chemical variations; Continental scientific drillings; Global climate changes; Hydrological changes; Interglacial periods; Last glacial terminations; Marine isotope stages; Sea surface temperature (SST); Lakes; climate variation; Last Glacial; paleoclimate; porewater; precipitation (climatology); sediment core; water budget; water chemistry; Dead Sea

Petrophysical, Geochemical, and Hydrological Evidence for Extensive Fracture-Mediated Fluid and Heat Transport in the Alpine Fault's Hanging-Wall Damage Zone - Townend, John; Sutherland, Rupert; Toy, Virginia G.; Doan, Mai-Linh; C'el'erier, Bernard; Massiot, C'ecile; Coussens, Jamie; Jeppson, Tamara; Janku-Capova, Lucie; Remaud, L'ea; Upton, Phaedra; Schmitt, Douglas R.; et al. (Geochemistry, Geophysics, Geosystems, 2017)
Fault rock assemblages reflect interaction between deformation, stress, temperature, fluid, and chemical regimes on distinct spatial and temporal scales at various positions in the crust. Here we interpret measurements made in the hanging-wall of the Alpine Fault during the second stage of the Deep Fault Drilling Project (DFDP-2). We present observational evidence for extensive fracturing and high hanging-wall hydraulic conductivity (∼10−9 to 10−7 m/s, corresponding to permeability of ∼10−16 to 10−14 m2) extending several hundred meters from the fault's principal slip zone. Mud losses, gas chemistry anomalies, and petrophysical data indicate that a subset of fractures intersected by the borehole are capable of transmitting fluid volumes of several cubic meters on time scales of hours. DFDP-2 observations and other data suggest that this hydrogeologically active portion of the fault zone in the hanging-wall is several kilometers wide in the uppermost crust. This finding is consistent with numerical models of earthquake rupture and off-fault damage. We conclude that the mechanically and hydrogeologically active part of the Alpine Fault is a more dynamic and extensive feature than commonly described in models based on exhumed faults. We propose that the hydrogeologically active damage zone of the Alpine Fault and other large active faults in areas of high topographic relief can be subdivided into an inner zone in which damage is controlled principally by earthquake rupture processes and an outer zone in which damage reflects coseismic shaking, strain accumulation and release on interseismic timescales, and inherited fracturing related to exhumation. © 2017. American Geophysical Union. All Rights Reserved.
Keywords: Earthquakes; Fracture; Geophysics; Groundwater; Hydrogeology; Topography; Transport properties; Damage zones; Earthquake rupture process; Fault zone; Petrophysical datum; Petrophysics; Seismogenesis; Spatial and temporal scale; Strain accumulations; Faulting; coseismic process; earthquake rupture; exhumation; fault zone; heat transfer; hydrogeology; petrochemistry; seismogram; topography; Alpine Fault Zone; New Zealand; South Island

Permeability and seismic velocity and their anisotropy across the Alpine Fault, New Zealand: An insight from laboratory measurements on core from the Deep Fault Drilling Project phase 1 (DFDP-1) - Allen, M.J.; Tatham, D.; Faulkner, D.R.; Mariani, E.; Boulton, C. (Journal of Geophysical Research: Solid Earth, 2017)
The Alpine Fault, a transpressional plate boundary between the Australian and Pacific plates, is known to rupture quasiperiodically with large magnitude earthquakes (Mw 8). The hydraulic and elastic properties of fault zones are thought to vary over the seismic cycle, influencing the nature and style of earthquake rupture and associated processes. We present a suite of laboratory permeability and P (Vp) and S (Vs) wave velocity measurements performed on fault lithologies recovered during the first phase of the Deep Fault Drilling Project (DFDP-1), which sampled principal slip zone (PSZ) gouges, cataclasites, and fractured ultramylonites, with all recovered lithologies overprinted by abundant secondary mineralization, recording enhanced fluid-rock interaction. Core material was tested in three orthogonal directions, orientated relative to the down-core axis and, when present, foliation. Measurements were conducted with pore pressure (H2O) held at 5 MPa over an effective pressure (Peff) range of 5 –105 MPa. Permeabilities and seismic velocities decrease with proximity to the PSZ with permeabilities ranging from 10−17 to 10−21 m2 and Vp and Vs ranging from 4400 to 5900 m/s in the ultramylonites/cataclasites and 3900 to 4200 m/s at the PSZ. In comparison with intact country rock protoliths, the highly variable cataclastic structures and secondary phyllosilicates and carbonates have resulted in an overall reduction in permeability and seismic wave velocity, as well as a reduction in anisotropy within the fault core. These results concur with other similar studies on other mature, tectonic faults in their interseismic period. ©2017. The Authors.
cited By 18
Keywords: deep drilling; elastic property; fault zone; hydraulic property; laboratory method; permeability; seismic anisotropy; seismic velocity; Alpine Fault Zone; New Zealand; South Island

Lake Lisan: The Archive of the Last Glacial Levant's Hydroclimatology - Stein, Mordechai; Goldstein, Steven L. (Quaternary of the Levant: Environments, Climate Change, and Humans, 2017)

Passive seismic imaging of structure discontinuities around the active fault using scattered earthquake waveforms - Zhang, H.; Chang, K. (79th EAGE Conference and Exhibition 2017 - Workshops, 2017)
For seismically active fault with relative dense seismic network, seismic tomography using first arrival times from earthquakes is routinely applied to image fault zone structures. To characterize structure discontinuities around the active fault, seismic scattering imaging using scattered waves can be applied. This technique has been extensively used with active seismic sources, especially in oil/gas industry. However, scattering imaging using waveforms from earthquakes is rare. Here we present the imaging results using scattered SH waves from earthquakes around the SAFOD, California. Near vertical reflectors are clearly imaged around the San Andreas fault (SAF), similar to results obtained using scattered P-P waves. However, for strike-slip focal mechanisms for earthquakes along the SAF, first arrival polarities for P waves are different at different regions. In comparison, SH waves have the same polarities. Because wavelength for P waves is longer than S waves, making the resolution of the imaging result is higher when using scattered S waves. For this study, we found coherent phases (scattered SH waves) after direct SH waves. Overall, the imaging results using different types of waves are bery similar, thus supporting the reliability and usefulness of using passive seismic events to image structure discontinuities.
cited By 0
Keywords: Petroleum industry; Seismic waves; Shear waves; Strike-slip faults; Structural geology; Earthquake waveforms; Image Structures; Oil/gas industry; San Andreas fault; Scattering imaging; Seismic networks; Seismic tomography; Seismically active faults; Earthquakes

Magmatic systems of large continental igneous provinces - Sharkov, E; Bogina, M; Chistyakov, A (Geoscience Frontiers, 2017)

Investigations of continued reservoir triggered seismicity at Koyna, India - Gupta, H.K.; Arora, K.; Rao, N.P.; Roy, S.; Tiwari, V.M.; Patro, P.K.; Satyanarayana, H.V.S.; Shashidhar, D.; Mahato, C.R.; Srinivas, K.N.S.S.S.; Srihari, M.; Satyavani, N.; et al. (Geological Society Special Publication, 2017)
Koyna, located in the Deccan Volcanic Province in western India, is the most significant site of reservoir triggered seismicity (RTS) globally. The largest RTS event of M 6.3 occurred here on December 10,1967. RTS at Koyna has continued. This includes 22 M > 5.0 and thousands of smaller events over the past 50 years. The annual loading and unloading cycles of the Koyna Reservoir and the nearby Warna Reservoir influence RTS. Koyna provides an excellent natural laboratory to comprehend the mechanism of RTS because earthquakes here occur in a small area, mostly at depths of 2-7 km, which are accessible for monitoring. A deep borehole laboratory is therefore planned to study earthquakes in the near-field to understand their genesis, especially in an RTS environment. Initially, several geophysical investigations were carried out to characterize the seismic zone, including 5000 line kilometres of airborne gravity gradiometry and magnetic surveys, high-quality magnetotelluric data from 100 stations, airborne LiDAR surveys over 1064 km2, drilling of 8 boreholes of approximately 1500 m depth and geophysical logging. To improve the earthquake locations a unique network of borehole seismometers was installed in six of these boreholes. These results, along with a pilot borehole drilling plan, are presented here. © 2017 The Author(s). Published by The Geological Society of London.
cited By 61

Large eighteenth –nineteenth century earthquakes in western gulf of corinth with reappraised size and location - Albini, Paola; Rovida, Andrea; Scotti, Oona; Lyon-Caen, H'elène (Bulletin of the Seismological Society of America, 2017)
The area of the western Gulf of Corinth around the city of Aigio (Achaea, northwest Peloponnese, Greece) represents an international pilot site for continuous monitoring and multidisciplinary research on earthquake processes. In the framework of the ANR-SISCOR Corinth Rift Laboratory project (2011 –2014), a thorough reappraisal of the five largest (Mw >6) eighteenth –nineteenth century earthquakes was performed, namely those of 14 May 1748, 23 August 1817, 26 December 1861, 9 September 1888, and 25 August 1889. Written observations of earthquake effects were looked into in their original version and language and were placed in the context from which they originated, to avoid the translations and digests on which previous seismological studies had relied. Earthquake records were traced for 108 different localities, and 143 macroseismic intensities in European Macroseismic Scale 1998 (EMS-98) have been assigned. Earthquake-related geological phenomena have been identified and carefully mapped, to be used as a further constraint of the location and magnitude of the associated earthquakes. Finally, new parameters for the studied earthquakes have been assessed with two separate and independent strategies to quantify epistemic uncertainties. In conclusion, the 1748, 1817, and 1888 earthquakes were located in the area of Aigio; the 1861 earthquake is reckoned to be the largest in the area, with an epicentral location at sea; whereas the 1889 earthquake has been relocated to the northwest in mainland Greece, well outside the Gulf of Corinth. © 2017, Seismological Society of America. All rights reserved.
Keywords: Achaea; Egion; Greece; Gulf of Corinth; Ionian Sea; Mediterranean Sea; Western Greece; Achaea; Geophysics; Location; Uncertainty analysis; Continuous monitoring; Earthquake process; Earthquake records; Epistemic uncertainties; Laboratory project; Macroseismic intensity; Multi-disciplinary research; New parameters; earthquake epicenter; earthquake event; earthquake magnitude; earthquake mechanism; eighteenth century; nineteenth century; paleoseismicity; seismicity; seismology; structural geology; Earthquakes

Linear and non-linear responses of vegetation and soils to glacial-interglacial climate change in a Mediterranean refuge - Holtvoeth, Jens; Vogel, Hendrik; Valsecchi, Verushka; Lindhorst, Katja; Schouten, Stefan; Wagner, Bernd; Wolff, George A. (Scientific Reports, 2017)
The impact of past global climate change on local terrestrial ecosystems and their vegetation and soil organic matter (OM) pools is often non-linear and poorly constrained. To address this, we investigated the response of a temperate habitat influenced by global climate change in a key glacial refuge, Lake Ohrid (Albania, Macedonia). We applied independent geochemical and palynological proxies to a sedimentary archive from the lake over the penultimate glacial-interglacial transition (MIS 6-5) and the following interglacial (MIS 5e-c), targeting lake surface temperature as an indicator of regional climatic development and the supply of pollen and biomarkers from the vegetation and soil OM pools to determine local habitat response. Climate fluctuations strongly influenced the ecosystem, however, lake level controls the extent of terrace surfaces between the shoreline and mountain slopes and hence local vegetation, soil development and OM export to the lake sediments. There were two phases of transgressional soil erosion from terrace surfaces during lake-level rise in the MIS 6-5 transition that led to habitat loss for the locally dominant pine vegetation as the terraces drowned. Our observations confirm that catchment morphology plays a key role in providing refuges with low groundwater depth and stable soils during variable climate. © 2017 The Author(s).

Lithology and stratigraphic interfaces prediction of the Continental Scientific Drilling Project of Cretaceous Songliao Basin (SK2) - Gao, Youfeng; Qu, Xuejiao; Jiang, Lijun; Wang, Shuxue; Wang, Pujun (Earth Science Frontiers, 2017)
The simulated stratigraphic column of SK2 is the main reference for the whole scientific drilling process bases on the experience of SK1. First of all, the depth of the main formation boundaries was predicted according to structural maps, seismic profiles and adjacent wells. Secondly, we predicted the detail lithology of each member or formation, based on regional stratigraphic-lithologic characteristics, geophysical data, and well Songshen3 and other adjacent wells. Finally, the designed coring horizon, contents, oil, gas and water bearing layers, probable drilling failures etc. were integrated into the comprehensive simulated stratigraphic column of SK2. The depth of the main formation boundaries of SK2 is predicted as below: the top of the 2nd member of Nenjiang Formation (T06) is 950 m, the top of Yaojia Formation (T1) is 1245 m, the top of Quantou Formation (T2) is 1680 m, the top of Denglouku Formation (T3) is 2530 m, the top of Yingcheng Formation (T4) is 2965 m, the top of Shahezi Formation (T4-1) is 3320 m, the top of Huoshiling Formation (T4-2) is 5670 m, and the top of basement (T5) is 6240 m. The lithology of main target strata of SK2 are predicted as follows. Yingcheng Formation can be divided into two parts, and the upper part consists mostly of coarse sand, conglomerate, and glutinite, with mudstone as interlayers, and massive tuff, andesite-basalt and rhyolite, dominated in the lower part. The Shahezi Formation is composed mostly of dark mudstone, with sand, siltstone, silty mudstone, and coal streak as interlayers. The lithology of Huoshiling Formation possibly corresponds to regional stratigraphic-lithologic characteristics, and the upper part is mainly composed of tuff, mudstone, and dacite and andesite, while the lower part consists mostly of dark mudstone, with fine-siltstone and coal streak as interlayers. The basement probably composed of conglomerate and permian-carboniferous “metamorphic rock”, which are probably very high diagenesis or very low-grade metamorphism sedimentary rocks. © 2017, Editorial Office of Earth Science Frontiers. All right reserved.
Keywords: Buildings; Lithology; Metamorphic rocks; Sedimentology; Stratigraphy; Well drilling; Continental scientific drillings; Denglouku formations; Low-grade metamorphism; Scientific drilling; Shahezi formations; Songliao basin; Stratigraphic columns; Stratigraphic interfaces; Sedimentary rocks

Location of the pilot borehole for investigations of reservoir triggered seismicity at Koyna, India - Gupta, H.K.; Shashidhar, D.; Mahato, C.R.; Satyanarayana, H.V.S.; Mallika, K.; Rao, N.P.; Maity, B.S.; Navitha, K. (Gondwana Research, 2017)
Artificial water reservoir triggered earthquakes are now known to have occurred at over 120 sites globally. The part played by the reservoirs in triggering is not exactly known due to lack of near field observations of triggered earthquakes. Koyna, located near the west coast of India, where triggered earthquakes have been occurring since 1962 provides an excellent site for near field observations of the target M ≥ 2 earthquakes. A 6 borehole seismic network has been deployed recently in the Koyna region at depths of 981 –1522 m to improve the hypocenter locations. During May –December 2015, a total of 1039 earthquakes of ML ≥ 0.5 were located using the borehole seismic network. The region is also monitored through a dense network of 23 surface broad-band stations. Our analysis indicates a significant improvement in the estimation of absolute locations of earthquakes with errors of the order of ± 300 m, combining both the networks. Based on seismicity, and logistics, a block of 2 × 2 km2 area has been chosen for drilling the first pilot borehole of 3 km depth, where M ≥ 2 earthquakes have been occurring frequently since 2005. © 2016 International Association for Gondwana Research
cited By 20
Keywords: borehole geophysics; borehole logging; broadband data; detection method; drilling; earthquake hypocenter; earthquake magnitude; error analysis; estimation method; reservoir-induced seismicity; site investigation; trigger mechanism; India; Koyna; Maharashtra

Logan medallist 4. Large-scale impact and earth history - Grieve, R.A.F. (Geoscience Canada, 2017)
The current record of large-scale impact on Earth consists of close to 200 impact structures and some 30 impact events recorded in the stratigraphic record, only some of which are related to known structures. It is a preservation sample of a much larger production population, with the impact rate on Earth being higher than that of the moon. This is due to the Earth’s larger physical and gravitational cross-sections, with respect to asteroidal and cometary bodies entering the inner solar system. While terrestrial impact structures have been studied as the only source of ground-truth data on impact as a planetary process, it is becoming increasingly acknowledged that large-scale impact has had its effects on the geologic history of the Earth, itself. As extremely high energy events, impacts redistribute, disrupt and reprocess target lithologies, resulting in topographic, structural and thermal anomalies in the upper crust. This has resulted in many impact structures being the source of natural resources, including some worldclass examples, such as gold and uranium at Vredefort, South Africa, Ni-Cu-PGE sulphides at Sudbury, Canada and hydrocarbons from the Campeche Bank, Mexico. Large-scale impact also has the potential to disrupt the terrestrial biosphere. The most devastating known example is the evidence for the role of impact in the Cretaceous-Paleocene (K-Pg) mass extinction event and the formation of the Chicxulub structure, Mexico. It also likely had a role in other, less dramatic, climatic excursions, such as the Paleocene-Eocene-Thermal Maximum (PETM) event. The impact rate was much higher in early Earth history and, while based on reasoned speculation, it is argued that the early surface of the Hadean Earth was replete with massive impact melt pools, in place of the large multiring basins that formed on the lower gravity moon in the same time-period. These melt pools would differentiate to form more felsic upper lithologies and, thus, are a potential source for Hadean-aged zircons, without invoking more modern geodynamic scenarios. The Earth-moon system is unique in the inner solar system and currently the best working hypothesis for its origin is a planetary-scale impact with the proto-Earth, after core formation at ca. 4.43 Ga. Future large-scale impact is a low probability event but with high consequences and has the potential to create a natural disaster of proportions unequalled by other geologic processes and threaten the extended future of human civilization, itself. © 2017 GAC/AGC®.
cited By 5

Magnetic mineralogical variability along Deccan trap basalt borehole (KBH07), Koyna deep continental drilling program, western Maharashtra, India - Sangode, S.J.; Venkateshwarulu, M.; Mahajan, R.; Randive, V. (Journal of the Geological Society of India, 2017)
A 1248 m long core (KBH 07, 17°18′07″ N; 73°47′28.2″E, 960m above msl) drilled up to basement in the Deccan traps from Koyna region was sampled at ∼10m interval for magnetic mineralogical studies.Analysis of routine rock magnetic parameters (mass specific magnetic susceptibility: χlf, frequency dependence of susceptibility: χfd, susceptibility of anhysteretic remanance: χARM, saturation isothermal remanance: SIRM, remanance coercivty: B(0)CR, SoftIRM, HardIRM, S-Ratio, SIRM/χlf, χARM/χlf) and density (σ, gm/cc) depicted significant higher order temporal variation. The χlf varies between 13 and 309 x 10-8m3/kg and is independent of density variation. The χARM, B(0)CR and S-Ratios indicate majority of SD-PSD ferrimagnets with episodes of MD ferrimagnetic concentration and few hard coercivity components. The giant plagioclase lath bearing (GPB) horizons show highest variability of ferrimagnetic concentration marked by anomalous peaks. Overall the variability of rock magnetic parameters independent of lava flow units suggest that the changeover in magnetic mineral concentration, composition and domain size occur at major episodes in magma composition (e.g., primary source, crustal contamination and fractional crystallization). The studied parameters are therefore examined to mark intervals of (i) magma compositional changes, (ii) zones of oxidative conditions and (iii) rapid/slow cooling intervals demanding detailed petrologic studies. We identified one I order trend, four II order cycles and eight III order cycles for the purpose of correlation. Notable peak in χlf at 650 –700m, the changeover in rock magnetic parameters at ∼930 m and ∼280 m can facilitate marker intervals while several higher order variations can be adopted for high resolution correlation to other boreholes in the region. The complex variation in rock magnetic parameters independent of flow units reflect temporal magnitudes of compositional variability, cooling and emplacement history that needs detailed petro-mineralogical attempts; and the present data is useful for high order inter-core correlations under the deep drilling program. © 2017, Geological Society of India.
cited By 7
Keywords: basalt; borehole; Deccan Traps; deep drilling; magnetic mineral; mineralogy; India; Koyna; Maharashtra

Paleointensity From Subaerial Basaltic Glasses From the Second Hawaii Scientific Drilling Project (HSDP2) Core and Implications for Possible Bias in Data From Lava Flow Interiors - Cai, S.; Tauxe, L.; Cromwell, G. (Journal of Geophysical Research: Solid Earth, 2017)
In this study, we collected samples from subaerial basaltic glassy margins from the second Hawaii Scientific Drilling Project (HSDP2) core. We employed the rigorous “IZZI” method during the paleointensity experiment combined with the stringent “CCRIT” criteria for data selection to obtain 21 robust paleointensity estimates recorded by glassy margins from 20 lava flows. We compared our new results to published paleointensities from the interiors of the lava flows from HSDP2 and found that our data are systematically lower than those from the interiors of the same lava flows. The reasons for the discrepancy in intensity are still unclear, but one possibility that could not be absolutely excluded is the effect of cooling rate on the more slowly cooled lava flow interiors. Although our new data from the glassy margins are lower than those from the lava flow interiors, they are still overall higher than the expected field of the study site calculated from a geocentric axial dipole model with an ancient average field of 42 ZAm2, either because of a long-term local anomaly of the field in Hawaii or an insufficient age distribution of our new data (e.g., missing the time period with low field intensities). ©2017. American Geophysical Union. All Rights Reserved.
Keywords: Hawaii [United States]; United States; basalt; drilling; glass; lava flow

Magnetic records from the Nenjiang Formation of core SK-1s and their implications - Li, Haiyan; Zhou, Tinghong; Zhang, Shihong; Liu, Guanghong; Wu, Huaichun; Yang, Tianshui; Zhao, Kunling (Earth Science Frontiers, 2017)
Rock magnetic records have been achieved from the Nenjiang Formation of the Songke-1 south core (SK-1s) in the Songliao Basin (972.46-1060.24 m). According to the magnetic records, this sequence is divided into three sections, termed A (972.46-979 m), B (979-1025 m) and C (1025-1060.24 m), respectively. Magnetic susceptibility (MS) and remanence of section A are both controlled by magnetite; while MS of sections B and C is controlled by paramagnetic minerals and their remanence is mainly carried by magnetite. Among the three sections, the concentration of magnetite of section A is the most and that of section B is the least; while the magnetite particles of section A are the coarsest and those of section C are the finest. The magnetic records of the Nenjiang Formation from SK-1s has deciphered the information of the uplift of the basin and the paleoclimatic changes of this area, although reductive diagenesis plays an effect on the sediments of sections B and C and thus produces the A/B boundary. On the one hand, the fluctuation of the magnetic parameters have recorded the periodical paleoclimatic changes. On the other hand, the abrupt variation of the magnetic parameters at the B/C boundary may be related to the alteration of detrital provenances resulting from the uplift of the eastern basin, from south-north to east-west. © 2017, Editorial Office of Earth Science Frontiers. All right reserved.
Keywords: Lithology; Magnetic susceptibility; Magnetite; Remanence; Sedimentology; Detrital provenance; Lake level fluctuations; Nenjiang Formation; Reductive diagenesis; Rock magnetism; Songke-1 south core (SK-1s); Magnetism

Microbiological and geochemical survey of Co2-dominated mofette and mineral waters of the Cheb Basin, Czech Republic - Krauze, Patryk; K{ampf, Horst; Horn, Fabian; Liu, Qi; Voropaev, Andrey; Wagner, Dirk; Alawi, Mashal (Frontiers in Microbiology, 2017)
The Cheb Basin (NW Bohemia, Czech Republic) is a shallow, neogene intracontinental basin. It is a non-volcanic region which features frequent earthquake swarms and large-scale diffuse degassing of mantle-derived CO2 at the surface that occurs in the form of CO2-rich mineral springs and wet and dry mofettes. So far, the influence of CO2 degassing onto the microbial communities has been studied for soil environments, but not for aquatic systems. We hypothesized, that deep-trenching CO2 conduits interconnect the subsurface with the surface. This admixture of deep thermal fluids should be reflected in geochemical parameters and in the microbial community compositions. In the present study four mineral water springs and two wet mofettes were investigated through an interdisciplinary survey. The waters were acidic and differed in terms of organic carbon and anion/cation concentrations. Element geochemical and isotope analyses of fluid components were used to verify the origin of the fluids. Prokaryotic communities were characterized through quantitative PCR and Illumina 16S rRNA gene sequencing. Putative chemolithotrophic, anaerobic and microaerophilic organisms connected to sulfur (e.g., Sulfuricurvum, Sulfurimonas) and iron (e.g., Gallionella, Sideroxydans) cycling shaped the core community. Additionally, CO2-influenced waters form an ecosystem containing many taxa that are usually found in marine or terrestrial subsurface ecosystems. Multivariate statistics highlighted the influence of environmental parameters such as pH, Fe2+ concentration and conductivity on species distribution. The hydrochemical and microbiological survey introduces a new perspective on mofettes. Our results support that mofettes are either analogs or rather windows into the deep biosphere and furthermore enable access to deeply buried paleo-sediments. © 2017 Krauze, K{ampf, Horn, Liu, Voropaev, Wagner and Alawi.
Keywords: carbon dioxide; helium; hydrogen; iron; mineral water; organic carbon; Actinobacteria; aquatic environment; Article; chromatography by stationary phase; controlled study; correlation analysis; Czech Republic; earthquake; electrical conductivity parameters; environmental factor; freshwater environment; geochemical analysis; hypoxia; isotope analysis; limit of quantitation; mass spectrometry; microbial community; microbiology; multivariate analysis; nonhuman; Proteobacteria; reverse transcription polymerase chain reaction; sequence analysis; soil analysis

New constraints on the Paleoarchean meteorite bombardment of the Earth – Geochemistry and Re-Os isotope signatures of spherule layers in the BARB5 ICDP drill core from the Barberton Greenstone Belt, South Africa - Schulz, Toni; Koeberl, Christian; Luguet, Ambre; Acken, David; Mohr-Westheide, Tanja; Ozdemir, Seda; Reimold, Wolf Uwe (Geochimica et Cosmochimica Acta, 2017)
Archean spherule layers, resulting from impacts by large extraterrestrial objects, to date represent the only remnants of the early meteorite, asteroid, and comet bombardment of the Earth. Only few Archean impact debris layers have been documented, all of them embedded in the 3.23 –3.47 billion year old successions of the Barberton Greenstone Belt (BGB) in South Africa and the Pilbara Craton in Western Australia. Some of them might be correlated with each other. Given the scarcity of Archean spherule deposits, four spherule layer intersections from the recently recovered BARB5 drill core from the central Barberton Greenstone Belt, analyzed in this study, provide an opportunity to gain new insight into the early terrestrial impact bombardment. Despite being hydrothermally overprinted, siderophile element abundance signatures of spherule-rich samples from the BARB5 drill core, at least in part, retained a meteoritic fingerprint. The impact hypothesis for the generation of the BARB5 spherule layers is supported by correlations between the abundances of moderately (Cr, Co, Ni) and highly siderophile (Re, Os, Ir, Pt, Ru and Pd) elements, whose peak concentrations and interelement ratios are within the range of those for chondrites. Rhenium-Osmium isotope evidence further support the impact hypothesis. Collectively, this study provides evidence for extraterrestrial admixtures ranging between ∼40 and up to 100% to three of the four analyzed BARB5 spherule layers, and a scenario for their genesis involving (i) impact of a chondritic bolide into a sedimentary target, (ii) varying admixtures of meteoritic components to target materials, (iii) spherule formation via condensation in an impact vapor plume, (iv) transportation of the spherules and sedimentation under submarine conditions, followed by (v) moderate post-impact remobilization of transition metals and highly siderophile elements. © 2017 Elsevier Ltd
Keywords: Australia; Barberton Greenstone Belt; Pilbara Block; Western Australia; Archean; Earth; geochemistry; impact; meteorite; Ocean Drilling Program; remobilization; rhenium-osmium dating; siderophile element; spherule

North Atlantic controlled depositional cycles in MIS 5e layered sediments from the deep Dead Sea basin - Palchan, D.; Neugebauer, I.; Amitai, Y.; Waldmann, N.D.; Schwab, M.J.; Dulski, P.; Brauer, A.; Stein, M.; Erel, Y.; Enzel, Y. (Quaternary Research (United States), 2017)
The drilled Inter-Continental Drilling Project core at the deeps of the Dead Sea reveals thick sequences of halite deposits from the last interglacial period, reflecting prevailing arid conditions in the lake's watershed. Here, we examine sequences of intercalating evaporates (halite or gypsum) and fine-detritus laminae and apply petrographic, micro-X-ray fluorescence, and statistical tools to establish in high-temporal resolution the hydroclimatic controls on the sedimentation in the last interglacial Dead Sea. The time series of the thickness of the best-recovered core sections of the layered halite, detritus, and gypsum reveals periodicities of 11, 7-8, and 4-5 yr, pointing to a North Atlantic control and possibly solar influence on the hydrology of the Dead Sea watershed during the regionally arid period of the last interglacial period. Similar periodicities were detected in the last glacial and modern sedimentary sequences of the Dead Sea and other archives of the central Levant, indicating a persistent impact of the solar cycles on regional hydrology, possibly through the effects of the North Atlantic Oscillation. © University of Washington. Published by Cambridge University Press, 2017.
cited By 16
Keywords: Atmospheric pressure; Chloride minerals; Gypsum; Hydrology; Seawater; Sodium chloride; Statistical mechanics; Watersheds; Dead sea; ICDP core; Interglacial; Laminated sediments; Levant; North Atlantic oscillations; Paleoclimates; Solar cycle; Oceanography; deposition; drilling; halite; Last Glacial; Last Interglacial; marine isotope stage; North Atlantic Oscillation; paleoclimate; periodicity; sedimentary sequence; solar cycle; Atlantic Ocean; Atlantic Ocean (North); Dead Sea; Levant; Mediterranean Region

Nucleation process of magnitude 2 repeating earthquakes on the San Andreas Fault predicted by rate-and-state fault models with SAFOD drill core data - Kaneko, Y.; Carpenter, B.M.; Nielsen, S.B. (Geophysical Research Letters, 2017)
Recent laboratory shear-slip experiments conducted on a nominally flat frictional interface reported the intriguing details of a two-phase nucleation of stick-slip motion that precedes the dynamic rupture propagation. This behavior was subsequently reproduced by a physics-based model incorporating laboratory-derived rate-and-state friction laws. However, applying the laboratory and theoretical results to the nucleation of crustal earthquakes remains challenging due to poorly constrained physical and friction properties of fault zone rocks at seismogenic depths. Here we apply the same physics-based model to simulate the nucleation process of crustal earthquakes using unique data acquired during the San Andreas Fault Observatory at Depth (SAFOD) experiment and new and existing measurements of friction properties of SAFOD drill core samples. Using this well-constrained model, we predict what the nucleation phase will look like for magnitude ∼2 repeating earthquakes on segments of the San Andreas Fault at a 2.8 km depth. We find that despite up to 3 orders of magnitude difference in the physical and friction parameters and stress conditions, the behavior of the modeled nucleation is qualitatively similar to that of laboratory earthquakes, with the nucleation consisting of two distinct phases. Our results further suggest that precursory slow slip associated with the earthquake nucleation phase may be observable in the hours before the occurrence of the magnitude ∼2 earthquakes by strain measurements close (a few hundred meters) to the hypocenter, in a position reached by the existing borehole. ©2016. American Geophysical Union. All Rights Reserved.
cited By 7
Keywords: Core drilling; Drills; Faulting; Friction; Geophysics; Laboratories; Nucleation; Numerical models; Phase meters; Plates (structural components); Slip forming; Stick-slip; Strike-slip faults; Tectonics; Tribology; Earthquake nucleation; Friction parameters; Frictional interface; Physics-based modeling; Rate and state friction; Repeating earthquake; Slow rupture front; Two-phase nucleation; Earthquakes; active fault; earthquake hypocenter; earthquake magnitude; earthquake rupture; experimental study; fault zone; friction; laboratory method; nucleation; numerical model; San Andreas Fault

Overview of Neotropical-Caribbean freshwater ostracode fauna (Crustacea, Ostracoda): identifying areas of endemism and assessing biogeographical affinities - Cohuo, Sergio; Macario-Gonz'alez, Laura; P'erez, Liseth; Schwalb, Antje (Hydrobiologia, 2017)
Freshwater ostracodes from the Neotropical-Caribbean region are potentially excellent tools for evolutionary and paleoenvironmental studies but their use is limited, because integrated data in taxonomy, environmental, and geographical preferences of the species at large scale remain unknown. A total of 118 species were recorded in the Neotropical-Caribbean region based on existing literature and results from fieldwork. About 74% of the species are restricted to the region and most of them show limited distributional areas as a consequence of environmental heterogeneity. Based on Parsimony Analysis of Endemicity, five areas of endemism were identified: (1) southern Florida, (2) southern Mexico-northern Central America, (3) Cuba, (4) Lesser Antilles, and (5) northern Venezuela-Aruba-Curacao-Trinidad. The conservation status of these areas was revised and lake ecosystems with endemic taxa were proposed to be included in environmental protection initiatives. Biogeographical analysis showed a strong differentiation between the ostracode faunas of the Neotropical-Caribbean region and the Neotropical-Neogen region. Few exchanges of species were attributed to ecological and geographical barriers such as volcanism and irregular orography. Faunal affinities within the Neotropical-Caribbean region indicated closer relationship between southern Mexico, southern Florida and the Antilles suggesting a common biogeographical history. Middle Central America and Chiapas-Guatemala highlands were discriminated as isolated regions. © 2016, Springer International Publishing Switzerland.
Keywords: Crustacea; Ostracoda

Real-time earthquake monitoring during the second phase of the deep fault drilling project, Alpine fault, New Zealand - Chamberlain, C.J.; Boese, C.M.; Eccles, J.D.; Savage, M.K.; Baratin, L.-M.; Townend, J.; Gulley, A.K.; Jacobs, K.M.; Benson, A.; Taylor-Offord, S.; Thurber, C.; Guo, B.; et al. (Seismological Research Letters, 2017)
The Deep Fault Drilling Project (DFDP) is a multinational scientific drilling effort to study the evolution, structure, and seismogenesis of the Alpine fault, New Zealand, via in situ measurements of fault rock properties. The second phase of drilling (DFDP-2), undertaken in the Whataroa Valley in late 2014, was intended to intersect the Alpine fault at a depth of around 1 km. In conjunction with the drilling and on-site science activities, a real-time seismic monitoring scheme and traffic-light response protocol were established to detect, locate, and if necessary respond to seismicity within 30 km of the drill site. This network was operated around the clock between late August 2014 and early January 2015, and we detected and located 493 earthquakes of ML 0.6-4.2. None of these earthquakes occurred within 3 km of the drill site, and nor did any of the seismicity detected require changes to drilling operations. The monitoring was undertaken using open-source software operated by an international team of 16 seismologists (including eight postgraduate students) working in 7 institutions and 3 countries to provide rapid on- and off-site manual checking and relocating of events. The team's standard response time between detection and final location was less than 30 min under normal background seismicity conditions and up to 1 hr during swarm activity and for low-priority, distant (≥30 km epicentrally from the drill site) earthquakes. This article documents the methodology, infrastructure, protocols, outcomes, and key lessons of this monitoring. © 2017 by the Seismological Society of America.
cited By 2
Keywords: Drills; Faulting; Geophysics; Open source software; Open systems; Rock drilling; Software engineering; Drilling operation; Earthquake monitoring; In-situ measurement; International team; Postgraduate students; Science activities; Scientific drilling; Seismic monitoring; Earthquakes; drilling; earthquake magnitude; earthquake swarm; fault; seismicity; Alpine Fault Zone; New Zealand; South Island; West Coast [South Island]; Whataroa

Utilizing the International Geo Sample Number Concept in Continental Scientific Drilling During ICDP Expedition COSC-1 - Lorenz, Henning; Ulbricht, Damian; Elger, Kirsten; Gorgas, Thomas (Data Science Journal, 2017)
Article: Utilizing the International Geo Sample Number Concept in Continental Scientific Drilling During ICDP Expedition COSC-1

Redox variations in Mauna Kea lavas, the oxygen fugacity of the Hawaiian plume, and the role of volcanic gases in Earth’s oxygenation - Brounce, M.; Stolper, E.; Eiler, J. (Proceedings of the National Academy of Sciences of the United States of America, 2017)
The behavior of C, H, and S in the solid Earth depends on their oxidation states, which are related to oxygen fugacity (fO2). Volcanic degassing is a source of these elements to Earth’s surface; therefore, variations in mantle fO2 may influence the fO2 at Earth’s surface. However, degassing can impact magmatic fO2 before or during eruption, potentially obscuring relationships between the fO2 of the solid Earth and of emitted gases and their impact on surface fO2. We show that low-pressure degassing resulted in reduction of the fO2 of Mauna Kea magmas by more than an order of magnitude. The least degassed magmas from Mauna Kea are more oxidized than midocean ridge basalt (MORB) magmas, suggesting that the upper mantle sources of Hawaiian magmas have higher fO2 than MORB sources. One explanation for this difference is recycling of material from the oxidized surface to the deep mantle, which is then returned to the surface as a component of buoyant plumes. It has been proposed that a decreasing pressure of volcanic eruptions led to the oxygenation of the atmosphere. Extension of our findings via modeling of degassing trends suggests that a decrease in eruption pressure would not produce this effect. If degassing of basalts were responsible for the rise in oxygen, it requires that Archean magmas had at least two orders of magnitude lower fO2 than modern magmas. Estimates of fO2 of Archean magmas are not this low, arguing for alternative explanations for the oxygenation of the atmosphere. © 2017, National Academy of Sciences. All rights reserved.
cited By 88

Timescales of magmatic processes prior to the ∼4.7 ka Agnano-Monte Spina eruption (Campi Flegrei caldera, Southern Italy) based on diffusion chronometry from sanidine phenocrysts - Iovine, Raffaella Silvia; Fedele, Lorenzo; Mazzeo, Fabio Carmine; Arienzo, Ilenia; Cavallo, Andrea; W{orner, Gerhard; Orsi, Giovanni; Civetta, Lucia; D’Antonio, Massimo (Bulletin of Volcanology, 2017)
Barium diffusion chronometry applied to sanidine phenocrysts from the trachytic Agnano-Monte Spina eruption (∼4.7 ka) constrains the time between reactivation and eruption of magma batches in the Campi Flegrei caldera. Backscattered electron imaging and quantitative electron microprobe measurements on 50 sanidine phenocrysts from representative pumice samples document core-to-rim compositional zoning. We focus on compositional breaks near the crystal rims that record magma mixing processes just prior to eruption. Diffusion times were modeled at a magmatic temperature of 930 °C using profiles based on quantitative BaO point analyses, X-ray scans, and grayscale swath profiles, yielding times ≤60 years between mixing and eruption. Such short timescales are consistent with volcanological and geochronological data that indicate that at least six eruptions occurred in the Agnano-San Vito area during few centuries before the Agnano-Monte Spina eruption. Thus, the short diffusion timescales are similar to time intervals between eruptions. Therefore, the rejuvenation time of magma residing in a shallow reservoir after influx of a new magma batch that triggered the eruption, and thus pre-eruption warning times, may be as short as years to a few decades at Campi Flegrei caldera. © 2017, Springer-Verlag Berlin Heidelberg.
Keywords: Campania [Italy]; Campi Flegrei; Italy; Napoli [Campania]; backscatter; caldera; electron probe analysis; geochronology; magmatism; phenocryst; sanidine; timescale; trigger mechanism; volcanic eruption

The fallacy of interpreting SSDS with different types of breccias as seismites amid the multifarious origins of earthquakes: Implications - Shanmugam, G. (Journal of Palaeogeography, 2017)
At present, there are no criteria to distinguish soft-sediment deformation structures (SSDS) formed by earthquakes from SSDS formed by the other 20 triggering mechanisms (see a companion paper in Vol. 5, No. 4 of this journal by Shanmugam, 2016). Even if one believes that earthquakes are the true triggering mechanism of SSDS in a given case, the story is still incomplete. This is because earthquakes (seismic shocks) are induced by a variety of causes: 1) global tectonics and associated faults (i.e., mid-ocean ridges, trenches, and transform faults); 2) meteorite-impact events; 3) volcanic eruptions; 4) post-glacial uplift; 5) tsunami impact; 6) cyclonic impact; 7) landslides (mass-transport deposits); 8) tidal activity; 9) sea-level rise; 10) erosion; and 11) fluid pumping. These different causes are important for developing SSDS. Breccias are an important group of SSDS. Although there are many types of breccias classified on the basis of their origin, five types are discussed here (fault, volcanic, meteorite impact, sedimentary-depositional, sedimentary-collapse). Although different breccia types may resemble each other, distinguishing one type (e.g., meteorite breccias) from the other types (e.g., fault, volcanic, and sedimentary breccias) has important implications. 1) Meteorite breccias are characterized by shock features (e.g., planar deformation features in mineral grains, planar fractures, high-pressure polymorphs, shock melts, etc.), whereas sedimentary-depositional breccias (e.g., debrites) do not. 2) Meteorite breccias imply a confined sediment distribution in the vicinity of craters, whereas sedimentary-depositional breccias imply an unconfined sediment distribution, variable sediment transport, and variable sediment provenance. 3) Meteorite, volcanic, and fault breccias are invariably subjected to diagenesis and hydrothermal mineralization with altered reservoir quality, whereas sedimentary-depositional breccias exhibit primary (unaltered) reservoir quality. And finally, 4) sedimentary-collapse breccias are associated with economic mineralization (e.g., uranium ore), whereas sedimentary-depositional breccias are associated with petroleum reservoirs. Based on this important group of SSDS with breccias, the current practice of interpreting all SSDS as “seismites” is inappropriate. Ending this practice is necessary for enhancing conceptual clarity and for advancing this research domain. © 2016 China University of Petroleum (Beijing)
cited By 15

The Iceland Deep Drilling Project 4.5 km deep well, IDDP-2, in the seawater-recharged Reykjanes geothermal field in SW Iceland has successfully reached its supercritical target - Fridleifsson, G.Ó.; Elders, W.A.; Zierenberg, R.A.; Fowler, A.P.; Weisenberger, T.B.; Hararson, B.S.; Mesfin, K.G. (Scientific Drilling, 2017)
The Iceland Deep Drilling Project research well RN-15/IDDP-2 at Reykjanes, Iceland, reached its target of supercritical conditions at a depth of 4.5 km in January 2017. After only 6 days of heating, the measured bottom hole temperature was 426 °C, and the fluid pressure was 34MPa. The southern tip of the Reykjanes peninsula is the landward extension of the Mid-Atlantic Ridge in Iceland. Reykjanes is unique among Icelandic geothermal systems in that it is recharged by seawater, which has a critical point of 406 °C at 29.8MPa. The geologic setting and fluid characteristics at Reykjanes provide a geochemical analog that allows us to investigate the roots of a mid-ocean ridge submarine black smoker hydrothermal system. Drilling began with deepening an existing 2.5 km deep vertical production well (RN-15) to 3 km depth, followed by inclined drilling directed towards the main upflow zone of the system, for a total slant depth of 4659m ( 4.5 km vertical depth). Total circulation losses of drilling fluid were encountered below 2.5 km, which could not be cured using lost circulation blocking materials or multiple cement jobs. Accordingly, drilling continued to the total depth without return of drill cuttings. Thirteen spot coring attempts were made below 3 km depth. Rocks in the cores are basalts and dolerites with alteration ranging from upper greenschist facies to amphibolite facies, suggesting that formation temperatures at depth exceed 450 °C. High-permeability circulation-fluid loss zones (feed points or feed zones) were detected at multiple depth levels below 3 km depth to bottom. The largest circulation losses (most permeable zones) occurred between the bottom of the casing and 3.4 km depth. Permeable zones encountered below 3.4 km accepted less than 5% of the injected water. Currently, the project is attempting soft stimulation to increase deep permeability. While it is too early to speculate on the energy potential of this well and its economics, the IDDP-2 is a milestone in the development of geothermal resources and the study of hydrothermal systems. It is the first well that successfully encountered supercritical hydrothermal conditions, with potential high-power output, and in which on-going hydrothermal metamorphism at amphibolite facies conditions can be observed. The next step will be to carry out flow testing and fluid sampling to determine the chemical and thermodynamic properties of the formation fluids. © Author(s) 2017.
cited By 62
Keywords: Drilling fluids; Economics; Geothermal energy; Geothermal fields; Geothermal wells; Seawater; Thermodynamic properties; Bottom hole temperatures; Formation temperature; Geothermal resources; Hydrothermal system; Iceland deep drilling projects; Supercritical condition; Supercritical hydrothermal; Total circulation loss; Rhenium compounds

The origin and degassing history of the Earth's atmosphere revealed by Archean xenon - Avice, Guillaume; Marty, Bernard; Burgess, Ray (Nature Communications, 2017)
Xenon (Xe) is an exceptional tracer for investigating the origin and fate of volatile elements on Earth. The initial isotopic composition of atmospheric Xe remains unknown, as do the mechanisms involved in its depletion and isotopic fractionation compared with other reservoirs in the solar system. Here we present high precision analyses of noble gases trapped in fluid inclusions of Archean quartz (Barberton, South Africa) that reveal the isotopic composition of the paleo-atmosphere at ≈3.3 Ga. The Archean atmospheric Xe is mass-dependently fractionated by 12.9±2.4 ‰ u-1 (± 2σ, s.d.) relative to the modern atmosphere. The lower than today 129 Xe excess requires a degassing rate of radiogenic Xe from the mantle higher than at present. The primordial Xe component delivered to the Earth's atmosphere is distinct from Solar or Chondritic Xe but similar to a theoretical component called U-Xe. Comets may have brought this component to the Earth's atmosphere during the last stages of terrestrial accretion. © 2017 The Author(s).
Keywords: Barberton; Mpumalanga; South Africa; argon; chlorine; inert gas; xenon; atmospheric chemistry; degassing; isotopic composition; isotopic fractionation; noble gas; paleoatmosphere; quartz; solar system; tracer; xenon; Archean; Article; astronomy; atmosphere; comparative study; fractionation; irradiation; thermodynamics; thermogenesis; volumetry

The Stratigraphy and Chronology of the Samra Formation - Waldmann, Nicolas (Quaternary of the Levant: Environments, Climate Change, and Humans, 2017)

The structural elements and tectonics of the Lake Van basin (Eastern Anatolia) from multi-channel seismic reflection profiles - Toker, M.; Sengor, A.M.C.; Demirel Schluter, F.; Demirbag, E.; Cukur, D.; Imren, C.; Group, PaleoVan-Working (Journal of African Earth Sciences, 2017)
This study analyzed multi-channel seismic reflection data from Lake Van, Eastern Anatolia, to provide key information on the structural elements, deformational patterns and overall tectonic structure of the Lake Van basin. The seismic data reveal three subbasins (the Tatvan, northern and Ahlat subbasins) separated by structural ridges (the northern and Ahlat ridges). The Tatvan basin is a tilted wedge-block in the west, it is a relatively undeformed and flat-lying deep basin, forming a typical example of strike-slip sedimentation. Seismic sections reveal that the deeper sedimentary sections of the Tatvan basin are locally folded, gently in the south and more intensely further north, suggesting a probable gravitational “wedge-block” instability, oblique to the northern margin. The northern subbasin, bounded by normal oblique faults, forms a basin-margin graben structure that is elongated in a northeast-southwest direction. The east-west trending Ahlat ridge forms a fault-wedged sedimentary ridge and appears to offset by reverse oblique faults forming as a push-up rhomb horst structure. The Ahlat subbasin is a fault-wedged trough fill that is elongated in the west-east direction and appears as a horst-foot graben formed by the normal oblique faults. The northeast-southwest directed northern ridge is a faulted crestal terrace of a sublacustrine basement block. Its step-like morphology, in response to the downfaulting of the Tatvan basin, as well as its backthrusted appearance, indicates the normal oblique nature of the bounding faults. The lacustrine shelf and slope show distinctive stratigraphic features; progradational deltas, submerged fluvial channels, distorted and collapsed beddings and soft sediment deformation structures, characterizing a highly unstable nature of shelf caused by strong oblique faulting and related earthquakes. The faulting caused uplift of the Çarpanak spur zone, together with the northeastern Erek delta, deformation of deltaic structures and subsequently exposing the shelf and slope areas. The exposed areas are evident in the angular unconformity surface of the Çarpanak basement block with the northeastern Erek delta and thinned sediments. The uplift resulted in the asymmetric depositional emplacement of the southeastern delta that is controlled by a series of ramp anticlines/low angle reverse faults. The Deveboynu subbasin and Varis spur zone form wide fault-controlled depressions with thick sediments that are elongated in the north-south direction. These subbasins appear as a small pull-apart boundary formed by normal oblique faults at the western end of the southeastern delta. © 2017 Elsevier Ltd
cited By 19
Keywords: deformation; graben; normal fault; reverse fault; sedimentation; seismic data; seismic reflection; strike-slip fault; tectonic structure; uplift; vertical seismic profile; Lake Van; Turkey

The top of the Olduvai Subchron in a high-resolution magnetostratigraphy from the West Turkana core WTK13, hominin sites and Paleolakes Drilling Project (HSPDP) - Sier, Mark J.; Langereis, Cor G.; Dupont-Nivet, Guillaume; Feibel, Craig S.; Joordens, Josephine C.A.; Lubbe, Jeroen H.J.L.; Beck, Catherine C.; Olago, Daniel; Cohen, Andrew (Quaternary Geochronology, 2017)
One of the major challenges in understanding the evolution of our own species is identifying the role climate change has played in the evolution of hominin species. To clarify the influence of climate, we need long and continuous high-resolution paleoclimate records, preferably obtained from hominin-bearing sediments, that are well-dated by tephro- and magnetostratigraphy and other methods. This is hindered, however, by the fact that fossil-bearing outcrop sediments are often discontinuous, and subject to weathering, which may lead to oxidation and remagnetization. To obtain fresh, unweathered sediments, the Hominin Sites and Paleolakes Drilling Project (HSPDP) collected a ∼216-meter core (WTK13) in 2013 from Early Pleistocene Paleolake Lorenyang deposits in the western Turkana Basin (Kenya). Here, we present the magnetostratigraphy of the WTK13 core, providing a first age model for upcoming HSPDP paleoclimate and paleoenvrionmental studies on the core sediments. Rock magnetic analyses reveal the presence of iron sulfides carrying the remanent magnetizations. To recover polarity orientation from the near-equatorial WTK13 core drilled at 5°N, we developed and successfully applied two independent drill-core reorientation methods taking advantage of (1) the sedimentary fabric as expressed in the Anisotropy of Magnetic Susceptibility (AMS) and (2) the occurrence of a viscous component oriented in the present day field. The reoriented directions reveal a normal to reversed polarity reversal identified as the top of the Olduvai Subchron. From this excellent record, we find no evidence for the Vrica Subchron’ previously reported in the area. We suggest that outcrop-based interpretations supporting the presence of the Vrica Subchron have been affected by the oxidation of iron sulfides initially present in the sediments -as evident in the core record- and by subsequent remagnetization. We discuss the implications of the observed geomagnetic record for human evolution studies. © 2017
Keywords: Kenya; Turkana; core analysis; hominid; human evolution; iron sulfide; magnetic reversal; magnetostratigraphy; Olduvai event; paleolimnology; Pleistocene; remagnetization

Understanding volcanic hazard at the most populated caldera in the world: Campi Flegrei, Southern Italy - De Natale, Giuseppe; Troise, Claudia; Kilburn, Christopher R. J.; Somma, Renato; Moretti, Roberto (Geochemistry, Geophysics, Geosystems, 2017)
Naples and its hinterland in Southern Italy are one of the most urbanized areas in the world under threat from volcanic activity. The region lies within range of three active volcanic centers: Vesuvius, Campi Flegrei, and Ischia. The Campi Flegrei caldera, in particular, has been in unrest for six decades. The unrest followed four centuries of quiescence and has heightened concern about an increased potential for eruption. Innovative modeling and scientific drilling are being used to investigate Campi Flegrei, and the results highlight key directions for better understanding the mechanisms of caldera formation and the roles of magma intrusion and geothermal activity in determining the volcano's behavior. They also provide a framework for evaluating and mitigating the risk from this caldera and other large ones worldwide. © 2017. American Geophysical Union. All Rights Reserved.
Keywords: Volcanoes; Caldera formation; Geothermal activity; Innovative models; Magma intrusion; Scientific drilling; Volcanic activities; Volcanic centers; Volcanic hazards; Hazards

The effect of gradational velocities and anisotropy on fault-zone trapped waves - Gulley, A.K.; Eccles, J.D.; Kaipio, J.P.; Malin, P.E. (Geophysical Journal International, 2017)
Synthetic fault-zone trapped wave (FZTW) dispersion curves and amplitude responses for FL (Love) and FR (Rayleigh) type phases are analysed in transversely isotropic 1-D elastic models. We explore the effects of velocity gradients, anisotropy, source location and mechanism. These experiments suggest: (i) A smooth exponentially decaying velocity model produces a significantly different dispersion curve to that of a three-layer model, with the main difference being that Airy phases are not produced. (ii) The FZTW dispersion and amplitude information of a waveguide with transverse-isotropy depends mostly on the Shear wave velocities in the direction parallel with the fault, particularly if the fault zone to country-rock velocity contrast is small. In this low velocity contrast situation, fully isotropic approximations to a transversely isotropic velocity model can be made. (iii) Fault-aligned fractures and/or bedding in the fault zone that cause transverse-isotropy enhance the amplitude and wave-train length of the FR type FZTW. (iv) Moving the source and/or receiver away from the fault zone removes the higher frequencies first, similar to attenuation. (v) In most physically realistic cases, the radial component of the FR type FZTW is significantly smaller in amplitude than the transverse. © The Authors 2017.
cited By 7
Keywords: Anisotropy; Dispersion (waves); Faulting; Fracture; Guided electromagnetic wave propagation; Numerical models; Shear waves; Velocity; Water waves; Amplitude information; Fault-zone trapped waves; High strain deformation zones; Higher frequencies; Seismic anisotropy; Shear wave velocity; Transverse isotropy; Transversely isotropic; Shear flow; deformation mechanism; fault zone; faulting; fracture zone; numerical model; seismic anisotropy; seismic attenuation; seismic velocity; strain analysis

Utilizing supercritical geothermal systems: a review of past ventures and ongoing research activities - Reinsch, T.; Dobson, P.; Asanuma, H.; Huenges, E.; Poletto, F.; Sanjuan, B. (Geothermal Energy, 2017)
Supercritical geothermal systems are very high-temperature geothermal systems that are located at depths near or below the brittle –ductile transition zone in the crust where the reservoir fluid is assumed to be in the supercritical state, that is for pure water, temperature and pressure are, respectively, in excess of 374 °C and 221 bar. These systems have garnered attention in recent years as a possible type of unconventional geothermal resource due to their very high enthalpy fluids. Supercritical conditions are often found at the roots of volcanic-hosted hydrothermal systems. More than 25 deep wells drilled in geothermal fields such as The Geysers, Salton Sea, and on Hawaii (USA), Kakkonda (Japan), Larderello (Italy), Krafla (Iceland), Los Humeros (Mexico), and Menengai (Kenya) have encountered temperatures in excess of 374 °C, and in some cases have encountered magma. Although fluid entries were documented for some of these wells, it remains an open question if permeability can be maintained at high enthalpy conditions. The IDDP-1 well at Krafla encountered magma, and ended up producing very high enthalpy fluids; however, these fluids were very corrosive and abrasive. Innovative drilling and well completion techniques are therefore needed to deal with the extreme temperatures and aggressive fluid chemistry compositions of these systems. New efforts are underway in Japan (northern Honshu), Italy (Larderello), Iceland (Reykjanes peninsula and Krafla), Mexico (Los Humeros), USA (Newberry), and New Zealand (Taupo Volcanic Zone) to investigate supercritical systems. Here, we review past studies, describe current research efforts, and outline the challenges and potential opportunities that these systems provide for international collaboration to ultimately utilize supercritical geothermal systems as a geothermal energy resource. © 2017, The Author(s).
cited By 114
Keywords: Energy resources; Enthalpy; Geothermal energy; Geothermal wells; International cooperation; Volcanoes; Well completion; Extreme temperatures; Geothermal resources; Geothermal systems; International collaborations; Supercritical condition; Supercritical systems; Taupo Volcanic Zone; Temperature and pressures; Geothermal fields; chemical composition; enthalpy; geothermal system; high temperature; hydrothermal system; permeability; reservoir; transition zone; well completion; California; Geysers; Hawaii [United States]; Honshu; Iceland; Italy; Iwate; Japan; Kakkonda Geothermal Field; Kenya; Krafla; Larderello; Los Humeros; Menengai Volcano; Mexico [North America]; Nakuru; New Zealand; Newberry Volcano; North Island; Oregon; Pisa [Tuscany]; Puebla [Mexico]; Reykjanes Peninsula; Salton Sea; Taupo Volcanic Zone; Tohoku; Tuscany; United States

Integration of multiple soft data sets in MPS thru multinomial logistic regression: a case study of gas hydrates - Rezaee, H.; Marcotte, D. (Stochastic Environmental Research and Risk Assessment, 2017)
A new approach is described to allow conditioning to both hard data (HD) and soft data for a patch- and distance-based multiple-point geostatistical simulation. The multinomial logistic regression is used to quantify the link between HD and soft data. The soft data is converted by the logistic regression classifier into as many probability fields as there are categories. The local category proportions are used and compared to the average category probabilities within the patch. The conditioning to HD is obtained using alternative training images and by imposing large relative weights to HD. The conditioning to soft data is obtained by measuring the probability –proportion patch distance. Both 2D and 3D cases are considered. Synthetic cases show that a stationary TI can generate non-stationary realizations reproducing the HD, keeping the texture indicated by the TI and following the trends identified in probability maps obtained from soft data. A real case study, the Mallik methane-hydrate field, shows perfect reproduction of HD while keeping a good reproduction of the TI texture and probability trends. © 2016, Springer-Verlag Berlin Heidelberg.
cited By 9
Keywords: Facsimile; Gas hydrates; Hydration; Regression analysis; Distance functions; Geostatistical simulation; Logistic regression classifier; Methane hydrates; Multinomial logistic regression; Multiple-point geostatistics; Patch based; Soft data; Probability; computer simulation; data set; gas hydrate; geostatistics; methane; probability; regression analysis

Variability in landscape and lake system responses to glacial and interglacial climates during the Middle Pleistocene based on palynological and geochemical data from Lake El'gygytgyn, Eastern Arctic - Lozhkin, Anatoly V.; Minyuk, Pavel S.; Anderson, Patricia M.; Nedorubova, Ekaterina Yu.; Korzun, Julya V. (Review of Palaeobotany and Palynology, 2017)

Variations of seismic b-value at different stages of the seismic cycle along the North Anatolian Fault Zone in northwestern Turkey - Raub, C.; Mart'inez-Garz'on, P.; Kwiatek, G.; Bohnhoff, M.; Dresen, G. (Tectonophysics, 2017)
We studied spatiotemporal b-value variations along the North Anatolian Fault Zone (NAFZ) in northwestern Turkey with a focus on the combined 1999 Izmit and D{uzce rupture and the eastern Sea of Marmara. We used a local seismicity catalog of the Izmit-D{uzce region covering a time span from 2.5 years prior to the Izmit until 14 months after the D{uzce mainshock and a four-year hypocenter catalog in the eastern Sea of Marmara. We consistently calculated moment magnitudes to ensure a homogeneous dataset and applied strict quality criteria. This allows studying variations of b-values throughout the region and at different stages of the seismic cycle. With a standard gridding technique b-value maps, depth sections and time series were calculated which reveal a very heterogeneous b-value distribution in the study area. The variety of b-value observations cannot be interpreted unambiguously, given that the b-value most likely depends on a combination of fault-zone characteristics like local stress conditions, heterogeneity of the crust and damage distribution. By presenting a comprehensive set of possible interpretations we point out that a biased discussion of the results towards stress or another individual parameter may lead to erroneous conclusions. Furthermore, the applied data discretization scheme influences the appearance of the final b-value distribution leading to potential misinterpretations. © 2017 Elsevier B.V.
cited By 8
Keywords: Geophysics; Physics; B value; B-value analysis; Damage distribution; Data discretization; North Anatolian Fault Zone; Northwestern Turkey; Sea of Marmara; Turkey; Seismology; earthquake catalogue; earthquake hypocenter; earthquake magnitude; earthquake rupture; fault zone; seismicity; spatiotemporal analysis; Anatolia; Sea of Marmara; Turkey

Volcanic-sedimentary succession description of the Lower Cretaceous Yingcheng Formation based on the ICDP scientific drilling borehole in the Songliao Basin (SK-2) - Gao, X.; Gao, Y.; Qu, X.; Li, H.; Chen, T.; Wang, P. (Earth Science Frontiers, 2017)
China Cretaceous Continental Scientific Drilling in the Songliao Basin, called SK2 project, has collected 365.32 m of the lower Cretaceous Yingcheng Formation whose age is estimated as Aptian-Albian. The borehole got a highly continuous core section with recovery of 98.47%, which is the most complete and precise geological records up to now for the stratum of continental non-marine Cretaceous in the world. The diameter of core is 214 mm which is among the largest diameter concerning coring engineering. We first described the volcanic-sedimentary succession in centimeter scale and studied the volcanic and sedimentary facies. Considering the sedimentary and volcanic rocks as a whole sequence, we recognized seventeen rock types from drilling core of the Yingcheng Formation. There are nine types of sedimentary rocks, including conglomerate, coarse sandstone, medium sandstone, fine sandstone, siltstone, silty mudstone, mudstone, breccia tuffaceous sandstone, and breccia-bearing tuffaceous sandstone. There are eight types of volcanic rocks including rhyolite, rhyolitic tuff/pyroclastics/agglomerate, rhyolitic welded tuff, crypto-explosive breccia, andesitic tuff, and tuffite. Sedimentary facies is fan delta dominant which includes five sedimentary microfacies of distributary channels, back swamp between delta, subaqueous distributary channels, subaqueous mouth bar and mudstone of still water. Volcanic facies are explosive facies and effusive facies dominant, which include four volcanic subfacies of air-fall, pyroclastic flow deposits, middle and upper flow subfacies of the effusive one. According to detailed description of the Yingcheng sequence, we first recognized three periodic sedimentary and volcanic cycles in the Yingcheng Formation, which have been numbered sedimentary I-volcanic I, sedimentary II-volcanic II, and sedimentary III-volcanic III in ascending order. This is a new discovery concerning the vertical features of of the Yingcheng Formation. The centimeter scale description on the core sections from the SK2 may provide some other useful information for related researches in the future. © 2017, Editorial Office of Earth Science Frontiers. All right reserved.
cited By 5
Keywords: Boring; Explosives; Rock drilling; Rocks; Sandstone; Sedimentology; Volcanic rocks; Volcanoes; Aptian to Albian; Sedimentary facies; Songliao basin; Volcanic facies; Volcanic-sedimentary succession and cycle; Yingcheng Formation; Sedimentary rocks

VS of the uppermost crust structure of the Campi Flegrei caldera (southern Italy) from ambient noise Rayleigh wave analysis - Costanzo, M.R.; Nunziata, C.; Strollo, R. (Journal of Volcanology and Geothermal Research, 2017)
Shear wave velocities (VS) are defined in the uppermost 1 –2 km of the Campi Flegrei caldera through the non-linear inversion of the group velocity dispersion curves of fundamental-mode Rayleigh waves extracted from ambient noise cross-correlations between two receivers. Noise recordings, three months long, at 12 seismic stations are cross-correlated between all couples of stations. The experiment provided successful results along 54 paths (inter-stations distance), of which 27 sampled a depth > 1 km. VS contour lines are drawn from 0.06 km b.s.l. to 1 km depth b.s.l. and show difference between the offshore (gulf of Pozzuoli and coastline) and the onshore areas. At 0.06 km b.s.l., the gulf of Pozzuoli and the coastline are characterized by VS of 0.3 –0.5 km/s and of 0.5 –0.7 km/s, respectively. Such velocities are typical of Neapolitan pyroclastic soils and fractured or altered tuffs. The inland shows VS in the range 0.7 –0.9 km/s, typical of Neapolitan compact tuffs. Velocities increase with depth and, at 1 km depth b.s.l., velocities lower than 1.5 km/s are still present in the gulf and along the coastline while velocities higher than 1.9 km/s characterize the eastern sector (grossly coincident with the Neapolitan Yellow Tuff caldera rim), the S. Vito plain and the area between Solfatara and SW of Astroni. Such features are much more evident along two cross-sections drawn in the offshore and onshore sectors by integrating our VS models with literature data. Our models join previous noise cross-correlation studies at greater scale at depths of 0.7 –0.8 km, hence the picture of the Campi Flegrei caldera is shown up to a depth of 15 km. VS of about 1.7 km/s, corresponding to compression velocities (VP) of about 3 km/s (computed by using the VP/VS ratio resulted in the inversion), are found at depths of 1.1 km, in the centre of the gulf of Pozzuoli, and at a depth of about 0.7 km b.s.l. onshore. An increment of VS velocity ( 1.9 –2.0 km/s) is locally observed onshore which might be attributed to a layer of tuffs and tuffites interbedded with thin lava beds, according to the correlation of VS with stratigraphies in the deep drillings of S. Vito. © 2017 Elsevier B.V.
Keywords: Campania [Italy]; Campi Flegrei; Italy; Napoli [Campania]; Acoustic noise; Group velocity dispersion; Landforms; Rayleigh waves; Shear waves; Velocity; Cross correlations; Fundamental modes; Group velocity dispersion curve; Neapolitan yellow tuffs; Non linear inversion; Pyroclastic soils; Seismic station; Shear wave velocity; ambient noise; caldera; correlation; crustal structure; drilling; Rayleigh wave; S-wave; seismic velocity; tuff; Shear flow

The environmental and evolutionary history of Lake Ohrid (FYROM/Albania): Interim results from the SCOPSCO deep drilling project - Wagner, Bernd; Wilke, Thomas; Francke, Alexander; Albrecht, Christian; Baumgarten, Henrike; Bertini, Adele; Combourieu-Nebout, Nathalie; Cvetkoska, Aleksandra; D'Addabbo, Michele; Donders, Timme H.; F{oller, Kirstin; Giaccio, Biagio; et al. (Biogeosciences, 2017)
This study reviews and synthesises existing information generated within the SCOPSCO (Scientific Collaboration on Past Speciation Conditions in Lake Ohrid) deep drilling project. The four main aims of the project are to infer (i) the age and origin of Lake Ohrid (Former Yugoslav Republic of Macedonia/Republic of Albania), (ii) its regional seismotectonic history, (iii) volcanic activity and climate change in the central northern Mediterranean region, and (iv) the influence of major geological events on the evolution of its endemic species. The Ohrid basin formed by transtension during the Miocene, opened during the Pliocene and Pleistocene, and the lake established de novo in the still relatively narrow valley between 1.9 and 1.3 Ma. The lake history is recorded in a 584 m long sediment sequence, which was recovered within the framework of the International Continental Scientific Drilling Program (ICDP) from the central part (DEEP site) of the lake in spring 2013. To date, 54 tephra and cryptotephra horizons have been found in the upper 460 m of this sequence. Tephrochronology and tuning biogeochemical proxy data to orbital parameters revealed that the upper 247.8 m represent the last 637 kyr. The multi-proxy data set covering these 637 kyr indicates long-term variability. Some proxies show a change from generally cooler and wetter to drier and warmer glacial and interglacial periods around 300 ka. Short-term environmental change caused, for example, by tephra deposition or the climatic impact of millennial-scale Dansgaard-Oeschger and Heinrich events are superimposed on the long-term trends. Evolutionary studies on the extant fauna indicate that Lake Ohrid was not a refugial area for regional freshwater animals. This differs from the surrounding catchment, where the mountainous setting with relatively high water availability provided a refuge for temperate and montane trees during the relatively cold and dry glacial periods. Although Lake Ohrid experienced significant environmental change over the last 637 kyr, preliminary molecular data from extant microgastropod species do not indicate significant changes in diversification rate during this period. The reasons for this constant rate remain largely unknown, but a possible lack of environmentally induced extinction events in Lake Ohrid and/or the high resilience of the ecosystems may have played a role. © Author(s) 2017.
Keywords: Albania; Lake Ohrid; Macedonia [Southern Europe]; Mediterranean Region; Animalia; catchment; climate variation; data set; deep drilling; environmental change; environmental history; extinction; gastropod; glacial-interglacial cycle; Heinrich event; historical record; lake; Miocene; paleoclimate; Pleistocene; Pliocene; project assessment; proxy climate record; seismotectonics; tephra

The effect of anorthite content and water on quartz-feldspar cotectic compositions in the rhyolitic system and implications for geobarometry - Wilke, S.; Holtz, F.; Neave, D.A.; Almeev, R. (Journal of Petrology, 2017)
The position of the cotectic curve separating quartz and feldspar stability fields in the rhyolite system Qz-Ab-Or(-An-H2O) depends on pressure, making it a potential geobarometer applicable to high-silica volcanic products if melt water contents (H2Omelt) are known. Until recently, the applicability of this geobarometer has been limited because pressure effects can be largely obscured by the effects of nearly ubiquitous normative anorthite (An, CaAl2Si2O8) in rhyolitic melts. In this study, we present new phase equilibria data that allow us to constrain the position of thermal minima and quartz-sanidine-plagioclase triple points on the quartz-feldspar cotectic curves at various pressures and melt normative An contents. Data were derived by conducting crystallization experiments to determine phase relations at the following conditions: 200 MPa, 1·4wt%H2Omelt, 3·5wt% An; 200 MPa, 1·3wt % H2Omelt, 7 wt % An; 500 MPa, 3wt % H2Omelt, 3·5wt % An; 500 MPa, 1·4wt % H2Omelt, 3·5wt % An; 500 MPa, 1·3wt%H2Omelt, 7 wt % An. Using this dataset with published phase equilibria results, we present a geobarometer based on the main parameters influencing cotectic compositions in the rhyolitic system: pressure, H2Omelt and melt An content. Our new geobarometer DERP (DEtermining Rhyolite Pressures) is calibrated to calculate pressures of magma storage from cotectic glass compositions with up to 7wt % normative melt An. DERP is calibrated for any H2Omelt in the pressure range 50-500 MPa. Its application is restricted to high-silica rhyolitic systems saturated with respect to quartz and feldspar(s). DERP was tested against various independent methods for estimating rhyolite pressures available in the literature (with an overall error of less than 100 MPa). Comparing pressures estimated with DERP and rhyolite-MELTS, which are based on the same approach, suggests that rhyolite-MELTS underestimates the effect of An. © The Author 2017. Published by Oxford University Press. All rights reserved.
cited By 27
Keywords: anorthite; crystallization; feldspar; geobarometry; magma; meltwater; petrology; phase equilibrium; quartz; rhyolite

Relationships between lake-level changes and water and salt budgets in the Dead Sea during extreme aridities in the Eastern Mediterranean - Kiro, Y.; Goldstein, S.L.; Garcia-Veigas, J.; Levy, E.; Kushnir, Y.; Stein, M.; Lazar, B. (Earth and Planetary Science Letters, 2017)
Thick halite intervals recovered by the Dead Sea Deep Drilling Project cores show evidence for severely arid climatic conditions in the eastern Mediterranean during the last three interglacials. In particular, the core interval corresponding to the peak of the last interglacial (Marine Isotope Stage 5e or MIS 5e) contains ∼30 m of salt over 85 m of core length, making this the driest known period in that region during the late Quaternary. This study reconstructs Dead Sea lake levels during the salt deposition intervals, based on water and salt budgets derived from the Dead Sea brine composition and the amount of salt in the core. Modern water and salt budgets indicate that halite precipitates only during declining lake levels, while the amount of dissolved Na+ and Cl− accumulates during wetter intervals. Based on the compositions of Dead Sea brines from pore waters and halite fluid inclusions, we estimate that ∼12 –16 cm of halite precipitated per meter of lake-level drop. During periods of halite precipitation, the Mg2+ concentration increases and the Na+/Cl− ratio decreases in the lake. Our calculations indicate major lake-level drops of ∼170 m from lake levels of 320 and 310 m below sea level (mbsl) down to lake levels of ∼490 and ∼480 mbsl, during MIS 5e and the Holocene, respectively. These lake levels are much lower than typical interglacial lake levels of around 400 mbsl. These lake-level drops occurred as a result of major decreases in average fresh water runoff, to ∼40% of the modern value (pre-1964, before major fresh water diversions), reflecting severe droughts during which annual precipitation in Jerusalem was lower than 350 mm/y, compared to ∼600 mm/y today. Nevertheless, even during salt intervals, the changes in halite facies and the occurrence of alternating periods of halite and detritus in the Dead Sea core stratigraphy reflect fluctuations between drier and wetter conditions around our estimated average. The halite intervals include periods that are richer and poorer in halite, indicating (based on the sedimentation rate) that severe dry conditions with water availability as low as ∼20% of the present day, continued for periods of decades to centuries, and fluctuated with wetter conditions that spanned centuries to millennia when water availability was ∼50 –100% of the present day. These conclusions have potential implications for the coming decades, as climate models predict greater aridity in the region. © 2017 Elsevier B.V.
cited By 39
Keywords: Brines; Budget control; Climate change; Climate models; Drops; Drought; Flood control; Isotopes; Lakes; Sea level; Sodium chloride; Stratigraphy; Water; Annual precipitation; Climatic conditions; Dead sea; Eastern Mediterranean; Interglacial; Lake levels; Marine isotope stages; Sedimentation rates; Chloride minerals; aridity; drought; extreme event; halite; interglacial; lake level; marine isotope stage; paleoclimate; Quaternary; salt; water budget; Dead Sea; Mediterranean Region

Seismic facies characterization of the overdeepened glacial tannwald basin - Burschil, T.; Buness, H.; Tanner, D.; Gabriel, G.; Krawczyk, C. (23rd European Meeting of Environmental and Engineering Geophysics, 2017)
A high-resolution P-wave vibroseis reflection survey and PSDM processing are used to image the structure of the Tannwald Basin, a 250 m-deep, distal branch basin of the Rhine Glacier. The basin substratum, the basin base, as well as the basin infill could be identified. The subglacial deposits (e.g. till) can be clearly distinguished from basin fines (e.g. marl, silt and sand). We identified five seismic facies as well as a number of subfacies. Internal features of the basin comprises an allochthonous Molasse block and a system of eskers in section. The interpretation will be used to locate a drill site for the ICDP-project DOVE and provides information for S-wave and multi-component processing.
cited By 2
Keywords: Fertilizers; Seismic waves; Seismology; Shear waves; Drill sites; High resolution; Internal features; Multicomponents; P waves; S-waves; Seismic facies; Vibroseis; Infill drilling

Repeating Marmara Sea earthquakes: Indication for fault creep - Bohnhoff, M.; Wollin, C.; Domigall, D.; K{uperkoch, L.; Mart'inez-Garz'on, P.; Kwiatek, G.; Malin, P.E. (Geophysical Journal International, 2017)
Discriminating between a creeping and a locked status of active faults is of central relevance to characterize potential rupture scenarios of future earthquakes and the associated seismic hazard for nearby population centres. In this respect, highly similar earthquakes that repeatedly activate the same patch of an active fault portion are an important diagnostic tool to identify and possibly even quantify the amount of fault creep. Here, we present a refined hypocentre catalogue for the Marmara region in northwestern Turkey, where a magnitude M up to 7.4 earthquake is expected in the near future. Based on waveform cross-correlation for selected spatial seismicity clusters, we identify two magnitude M 2.8 repeater pairs. These repeaters were identified as being indicative of fault creep based on the selection criteria applied to the waveforms. They are located below the western part of the Marmara section of the North Anatolian Fault Zone and are the largest reported repeaters for the larger Marmara region. While the eastern portion of the Marmara seismic gap has been identified to be locked, only sparse information on the deformation status has been reported for its western part. Our findings indicate that the western Marmara section deforms aseismically to a substantial extent, which reduces the probability for this region to host a nucleation point for the pending Marmara earthquake. This is of relevance, since a nucleation of the Marmara event in the west and subsequent eastward rupture propagation towards the Istanbul metropolitan region would result in a substantially higher seismic hazard and resulting risk than if the earthquake would nucleate in the east and thus propagate westward away from the population centre Istanbul. © The Authors 2017.
cited By 39
Keywords: Creep; Faulting; Geophysics; Hazards; Locks (fasteners); Nucleation; Seismic response; Seismology; Transform faults; Earthquake hazard; Metropolitan regions; North Anatolian Fault Zone; Northwestern Turkey; Nucleation points; Rupture propagation; Selection criteria; Waveform cross correlation; Earthquakes; active fault; creep; earthquake catalogue; earthquake magnitude; earthquake rupture; fault zone; seismic hazard; seismicity; transform fault; Marmara [Turkey]; Sea of Marmara; Turkey

Report on the ICDP workshop DIVE (Drilling the Ivrea-Verbano zonE) - Pistone, Mattia; M{untener, Othmar; Ziberna, Luca; Het'enyi, Gy{orgy; Zanetti, Alberto (Scientific Drilling, 2017)
The Ivrea-Verbano Zone is the most complete, time-integrated crust-upper mantle archive in the world. It is a unique target for assembling data on the deep crust and the Moho transition zone and testing several hypotheses of formation, evolution, and modification of the continental crust through space and time across the Earth. The ICDP workshop Drilling the Ivrea-Verbano zonE (DIVE), held in Baveno, Italy, from 1 to 5 May 2017, focused on the scientific objectives and the technical aspects of drilling and sampling in the Ivrea- Verbano Zone at depth. A total of 47 participants from 9 countries with a wide variety of scientific and/or drilling expertise attended the meeting. Discussion on the proposed targets sharpened the main research lines and led to working groups and the necessary technical details to compile the full drilling proposal. The participants of the workshop concluded that four drilling operations in the Val Sesia and Val d'Ossola crustal sections represent the scientifically most promising solution to achieve the major goals within DIVE to unravel the physico-chemical properties and architecture of the lower continental crust towards the crust-mantle (Moho) transition zone. © Author(s) 2017.
Keywords: Chemical operations; Continental crusts; Drilling operation; Physicochemical property; Scientific objectives; Space and time; Technical aspects; Technical details; Transition zones; Earth (planet)

Rock strength measurements on Archaean basement granitoids recovered from scientific drilling in the active Koyna seismogenic zone, western India - Goswami, D.; Akkiraju, V.V.; Misra, S.; Roy, S.; Singh, S.K.; Sinha, A.; Gupta, H.; Bansal, B.K.; Nayak, S. (Tectonophysics, 2017)
Reservoir triggered earthquakes have been occurring in the Koyna area, western India for the past five decades. Triaxial tests carried out on 181 core samples of Archaean granitoids underlying the Deccan Traps provide valuable constraints on rock strength properties in the Koyna seismogenic zone for the first time. The data include measurements on granite gneiss, granite, migmatitic gneiss and mylonitised granite gneiss obtained from boreholes KBH-3, KBH-4A, KBH-5 and KBH-7 located in the western and eastern margins of the seismic zone. Salient results are as follows. (i) Increase of rock strength with increasing confining pressure allow determination of the linearized failure envelopes from which the cohesive strength and angle of internal friction are calculated. (ii) Variable differential stresses at different depths are the manifestations of deformation partitioning in close association of fault zone(s) or localized fracture zones. (iii) Fractures controlled by naturally developed weak planes such as cleavage and fabric directly affect the rock strength properties, but the majority of failure planes developed during triaxial tests is not consistent with the orientations of pre-existing weak planes. The failure planes may, therefore, represent other planes of weakness induced by ongoing seismic activity. (iv) Stress-strain curves confirm that axial deformation is controlled by the varying intensity of pre-existing shear in the granitoids, viz., mylonite, granite gneiss and migmatitic gneiss. (v) Frequent occurrences of low magnitude earthquakes may be attributed to low and variable rock strength of the granitoids, which, in turn, is modified by successive seismic events. © 2017 Elsevier B.V.
cited By 13
Keywords: Buildings; Deformation; Granite; Infill drilling; Seismographs; Stress-strain curves; Failure criteria; Granitoids; India; Rock strength; Scientific drilling; Seismic zones; Earthquakes; Archean; basement rock; drilling; failure mechanism; granitoid; rock mechanics; seismic zone; seismicity; strength; stress-strain relationship

Seafloor Response to Large Volcanic Activity and Geohazard Implications in Naples Bay, Southern Italy - Violante, Crescenzo; Sacchi, Marco; Spiess, Volkhard; Steinmann, Lena (Offshore Site Investigation Geotechnics 8th International Conference Proceeding, 2017)
In this study, marine geophysical investigations were utilized to recognize, compare and classify seafloor features related to volcanic activity in the Naples Bay, southern Italy. The dataset includes swath bathymetry, side-scan sonar records, as well as single-channel and multichannel reflection seismics. Ground truth was provided by detailed analysis of gravity cores. By integrating these data, large portions of the seafloor were mapped, providing important information for geohazard assessment.

Sedimentology of the Lacustrine Formations in the Dead Sea Basin - Waldmann, Nicolas; Neugebauer, Ina; Palchan, Daniel; Hadzhiivanova, Elitsa; Taha, Nimer; Brauer, Achim; Enzel, Yehouda (Quaternary of the Levant: Environments, Climate Change, and Humans, 2017)

Sedimentology, stratigraphic context, and implications of Miocene intrashelf bottomset deposits, offshore New Jersey - Hodgson, D.M.; Browning, J.V.; Miller, K.G.; Hesselbo, S.P.; Poyatos-Mor'e, M.; Mountain, G.S.; Proust, J.-N. (Geosphere, 2017)
Drilling of intrashelf Miocene clinothems onshore and offshore New Jersey has provided better understanding of their topset and foreset deposits, but the sedimentology and stratigraphy of their bottomset deposits have not been documented in detail. Three coreholes (Sites M27-M29), collected during Integrated Ocean Drilling Program (IODP) Expedition 313, intersect multiple bottomset deposits, and their analysis helps to refine sequence stratigraphic interpretations and process response models for intrashelf clinothems. At Site M29, the most downdip location, chronostratigraphically well-constrained bottomset deposits follow a repeated stratigraphic motif. Coarse-grained glauconitic quartz sand packages abruptly overlie deeply burrowed surfaces. Typically, these packages coarsen then fine upwards and pass upward into bioturbated siltstones. These coarse sand beds are amalgamated and poorly sorted and contain thin-walled shells, benthic foraminifera, and extrabasinal clasts, consistent with an interpretation of debrites. The sedimentology and mounded seismic character of these packages support interpretation as debrite-dominated lobe complexes. Farther updip, at Site M28, the same chronostratigraphic units are amalgamated, with the absence of bioturbated silts pointing to more erosion in proximal locations. Graded sandstones and dune-scale cross-bedding in the younger sequences in Site M28 indicate deposition from turbidity currents and channelization. The sharp base of each package is interpreted as a sequence boundary, with a period of erosion and sediment bypass evidenced by the burrowed surface, and the coarse-grained debritic and turbiditic deposits representing the lowstand systems tract. The overlying fine-grained deposits are interpreted as the combined transgressive and highstand systems tract deposits and contain the deepwater equivalent of the maximum flooding surface. The variety in thickness and grain-size trends in the coarse-grained bottomset packages point to an autogenic control, through compensational stacking of lobes and lobe complexes. However, the large-scale stratigraphic organization of the bottomset deposits and the coarse-grained immature extrabasinal and reworked glauconitic detritus point to external controls, likely a combination of relative sea-level fall and waxing- and-waning cycles of sediment supply. This study demonstrates that large amounts of sediment gravity-flow deposits can be generated in relatively shallow ( 100-200 m deep) and low-gradient ( 1°-4°) clinothems that prograded across a deep continental shelf. This physiography likely led to the dominance of debris flow deposits due to the short transport distance limiting transformation to low-concentration turbidity currents. © 2017 The Authors.
cited By 26
Keywords: Erosion; Ocean currents; Offshore drilling; Sea level; Sediment transport; Sedimentology; Sediments; Stratigraphy; Thin walled structures; Turbidity; Benthic foraminifera; Compensational stacking; Highstand systems tract; Integrated ocean drilling programs; Maximum flooding surfaces; Sediment gravity flow; Sequence-stratigraphic interpretation; Stratigraphic organizations; Deposits; chronostratigraphy; debris flow; Miocene; quartz; sediment transport; sedimentology; New Jersey; United States; Foraminifera

Seismological evidence of fault weakening due to erosion by fluids from observations of intraplate earthquake swarms - Vavryčuk, V'aclav; Hrubcov'a, Pavla (Journal of Geophysical Research: Solid Earth, 2017)
The occurrence and specific properties of earthquake swarms in geothermal areas are usually attributed to a highly fractured rock and/or heterogeneous stress within the rock mass being triggered by magmatic or hydrothermal fluid intrusion. The increase of fluid pressure destabilizes fractures and causes their opening and subsequent shear-tensile rupture. The spreading and evolution of the seismic activity are controlled by fluid flow due to diffusion in a permeable rock (fluid-diffusion model) and/or by redistribution of Coulomb stress (intrusion model). These models, however, are not valid universally. We provide evidence that none of these models is consistent with observations of swarm earthquakes in West Bohemia, Czech Republic. Full seismic moment tensors of microearthquakes in the 2008 swarm in West Bohemia indicate that fracturing at the starting phase of the swarm was not associated with fault openings caused by pressurized fluids but rather with fault compactions. This can physically be explained by a fault-weakening model, when the essential role in the swarm triggering is attributed to degradation of fault strength due to long-lasting chemical and hydrothermal fluid-rock interactions in the focal zone. Since the rock is exposed to circulating hydrothermal, CO2-saturated fluids, the walls of fractures are weakened by dissolving and altering various minerals. The porosity of the fault gauge increases, and the fault weakens. If fault strength lowers to a critical value, the seismicity is triggered. The fractures are compacted during failure, the fault strength recovers, and a new cycle begins. ©2017. American Geophysical Union. All Rights Reserved.
Keywords: Bohemia; Czech Republic; earthquake swarm; erosion; fault; fluid pressure; hydrothermal fluid; intraplate process; microearthquake; moment tensor; seismology

The drilling of RN-15/IDDP-2 research well at Reykjanes In sw Iceland - Stef'ansson, Ari; G'islason, P'or; Sigurdsson, Ómar; Fridleifsson, Gudmundur Ó. (Transactions - Geothermal Resources Council, 2017)

Source and magmatic evolution inferred from geochemical and Sr-O-isotope data on hybrid lavas of Arso, the last eruption at Ischia island (Italy; 1302 AD) - Iovine, Raffaella Silvia; Mazzeo, Fabio Carmine; Arienzo, Ilenia; D'Antonio, Massimo; W{orner, Gerhard; Civetta, Lucia; Pastore, Zeudia; Orsi, Giovanni (Journal of Volcanology and Geothermal Research, 2017)
Geochemical and isotopic (87Sr/86Sr and 18O/16O) data have been acquired on whole rock and separated mineral samples from volcanic products of the 1302 AD Arso eruption, Ischia volcanic island (Gulf of Naples, Southern Italy), to investigate magmatic processes. Our results highlight petrographic and isotopic disequilibria between phenocrysts and their host rocks. Similar disequilibria are observed also for more mafic volcanic rocks from Ischia and in the Phlegraean Volcanic District in general. Moreover, 87Sr/86Sr and 18O/16O values suggest mixing between chemically and isotopically distinct batches of magma, and crystals cargo from an earlier magmatic phase. The radiogenic Sr isotope composition suggests that the mantle source was enriched by subduction-derived sediments. Furthermore, magmas extruded during the Arso eruption were affected by crustal contamination as suggested by high oxygen isotope ratios. Assimilation and fractional crystallization modelling of the Sr-O isotope compositions indicates that not more than 7% of granodioritic rocks from the continental crust have been assimilated by a mantle-derived mafic magma. Hence the recent volcanic activity of Ischia has been fed by distinct batches of magma, variably contaminated by continental crust, that mixed during their ascent towards the surface and remobilized phenocrysts left from earlier magmatic phases. © 2016 Elsevier B.V.
Keywords: Campania [Italy]; Ischia; Italy; Napoli [Campania]; Geochemistry; Isotopes; Minerals; Rock products; Volcanic rocks; Volcanoes; Crustal contamination; Ischia island; Magmatic plumbing system; Mingling/mixing; Stable isotopes; crustal contamination; igneous geochemistry; lava; magmatism; mixing; oxygen isotope; point source; source rock; stable isotope; strontium isotope; volcanic eruption; volcanology; Strontium compounds

Structural characteristics of the Lake Van Basin, eastern Turkey, from high-resolution seismic reflection profiles and multibeam echosounder data: geologic and tectonic implications - Cukur, D.; Krastel, S.; Tomonaga, Y.; Schmincke, H.-U.; Sumita, M.; Meydan, A.F.; Çağatay, M.N.; Toker, M.; Kim, S.-P.; Kong, G.-S.; Horozal, S. (International Journal of Earth Sciences, 2017)
The structural evolution of Lake Van Basin, eastern Turkey, was reconstructed based on seismic reflection profiles through the sedimentary fill as well as from newly acquired multibeam echosounder data. The major sub-basins (Tatvan Basin and Northern Basin) of Lake Van, bound by NE-trending faults with normal components, formed during the past 600 ka probably due to extensional tectonics resulting from lithospheric thinning and mantle upwelling related to the westward escape of Anatolia. Rapid extension and subsidence during early lake formation led to the opening of the two sub-basins. Two major, still active volcanoes (Nemrut and S{uphan) grew close to the lake basins approximately synchronously, their explosive deposits making up >20 % of the drilled upper 220 m of the ca. 550-m-thick sedimentary fill. During basin development, extension and subsidence alternated with compressional periods, particularly between 340 and 290 ka and sometime before 14 ka, when normal fault movements reversed and gentle anticlines formed as a result of inversion. The 14 ka event was accompanied by widespread uplift and erosion along the northeastern margin of the lake, and substantial erosion took place on the crests of the folds. A series of closely spaced eruptions of S{uphan volcano occurred synchronously suggesting a causal relationship. Compression is still prevalent inside and around Lake Van as evidenced by recent faults offsetting the lake floor and by recent devastating earthquakes along their onshore continuations. New, high-resolution bathymetry data from Lake Van reveal the morphology of the Northern Ridge and provide strong evidence for ongoing transpression on a dextral strike-slip fault as documented by the occurrence of several pop-up structures along the ridge. © 2016, Springer-Verlag Berlin Heidelberg.
cited By 21
Keywords: basin evolution; compression; extensional tectonics; mantle upwelling; seismic data; seismic reflection; spectral resolution; volcanism; Lake Van; Turkey

Successful drilling for supercritical geothermal resources at Reykjanes in SW Iceland - Fridleifsson, Gudmundur Ó.; Elders, Wilfred A. (Transactions - Geothermal Resources Council, 2017)
The Iceland Deep Drilling Project (IDDP) passed a significant milestone in January 2017 when its IDDP-2 well penetrated a supercritical reservoir at a depth of 4.5 km. After only 6 days of heating, the temperature measured at the bottom of the well was ∼426°C, with fluid pressure of 340 bars, with indications of permeability at depth. The IDDP is a project of a consortium of Icelandic energy companies, National Energy Authority of Iceland and Statoil, aimed at greatly increasing the production of usable geothermal energy by drilling deep enough to reach the supercritical zone beneath high-temperature geothermal fields. Modeling indicates that, because of the higher enthalpy of supercritical fluid, and more favorable flow properties, a well producing supercritical water could produce an order of magnitude more usable energy than that produced from conventional high-temperature geothermal wells. The IDDP-2 well is located in the Reykjanes geothermal field which lies near the southern tip of the Reykjanes Peninsula, the landward extension of the Mid-Atlantic Ridge. At Reykjanes, some 34 production and injection wells supply a 100 MWe power plant, producing from a < 300°C reservoir at 1 to 2.5 km depth. It is unique among Icelandic geothermal systems because its reservoir is recharged by seawater, which has a critical point of the 406°C at 298 bars. Drilling the IDDP-2 began by using an existing 2.5 km deep production well, RN-15, that was deepened and cased to 3,000 m depth and then angled towards the main upflow zone of the system for a total slant depth of 4,659 m (∼4.5 km vertical depth). Total circulation losses were encountered below 3 km depth which could not be cured by lost circulation materials or by multiple cement jobs. Accordingly, drilling continued blind to total depth, without return of drill cuttings. We attempted 13 core runs below 3 km depth, only 9 of which recovered some core. The cores are basalts and dolerites in a sheeted dike swarm with alteration ranging from lower greenschist facies to lower amphibolite facies, suggesting formation temperatures >450°C, but with low water/rock ratios. A perforated liner was inserted to 4,620 m and the well subsequently logged for temperature, pressure and injectivity. The T-log showed the main permeable zones to be at above 3380 m, with smaller feed zones at 3,820 m, 3,990 m, 4,100, 4,200 m, 4,375 m, and 4,550 m depths. The deeper feed zones accepted ∼5% of the injected water. This year we will attempt to enhance the deeper permeability by massive soft stimulation, and then carry out flow tests to determine the thermodynamic and chemical properties of the fluid produced.
Keywords: Effluent treatment; Geothermal wells; Hydraulic structures; Rhenium compounds; Supercritical fluids; Temperature; Well drilling; Well stimulation; DEEPEGS; Formation temperature; Iceland deep drilling projects; Lost circulation materials; National energy authorities; Reykjanes; Supercritical; Total circulation loss; Geothermal fields

Terrestrial biota and climate during Cretaceous greenhouse in NE China - Wan, Xiaoqiao; Wu, Huaichun; Xi, Dangpeng; Liu, Meiyu; Qin, Zuohuan (Earth Science Frontiers, 2017)
Northeast China offers a unique opportunity to perceive Cretaceous stratigraphy and climate of terrestrial settings. The sediments contain variegated clastic and volcanic rocks, diverse terrestrial fossils, and important coal and oil resources. Four Cretaceous biotas of Jehol, Fuxin, Songhuajiang and Jiayin occurred in ascending order. For scientific purpose, a coring program (SK1) provides significant material for Cretaceous research. The SK1 presents a continuous section of Upper Cretaceous non-marine fossils, magnetochron successions and chronostratigraphic events. These events are integrated with marine events by an X/Y graphic plot between the core data and a global database of GSSP and key reference sections. More precisely, age interpolation based on CA-ID-TIMS U-Pb zircon dates and the calibrated cyclostratigraphy places the end of the Cretaceous Normal Superchon at 83.07±0.15 Ma. This date also serves as an estimate for the Santonian-Campanian stage boundary. It also places the K/Pg boundary within the upper part of the Mingshui Formation. The terrestrial and marine life and the analysis of elemental composition, δ13Corg, biomarkers show that lake water salinity changed along with a Coniacian-Santonian marine incursion. High lake-level coincides with the sea transgression during the time. High salinity resulted in the development of periodic anoxic environments of the basin. One of these times of deposition of organic-rich mud correlates with the magnetochron of C34n/C33r and Coniacian-Santonian planktic foraminifera. This marine flooding correlates with OAE 3 and it is possible that the global oceanic anoxic event may have influenced organic carbon burial in the Songliao Basin for this brief period. The evolution of 4 biotas corresponds to the Cretaceous climate change. We tentatively interpret the terrestrial record to reflect the changes in both global climate and regional basin evolution. © 2017, Editorial Office of Earth Science Frontiers. All right reserved.
Keywords: Carbon; Coal deposits; Lakes; Lead; Organic carbon; Petroleum deposits; Silicate minerals; Stratigraphy; Volcanic rocks; Cretaceous; Elemental compositions; NE China; Oceanic Anoxic Event; Organic carbon burial; Paleoclimates; Planktic foraminifera; Terrestrial biota; Climate change

The Amora Formation, Dead Sea Basin - Torfstein, Adi (Quaternary of the Levant: Environments, Climate Change, and Humans, 2017)

THE CAMPI FLEGREI DEEP DRILLING PROJECT (CFDDP): CALDERA STRUCTURE AND HAZARD - Natale, Giuseppe; Claudia, Troise; Renato, Somma; Perillo, Giovanni (International Journal of Safety and Security Engineering, 2017)
The recent investigation carried out on the west bound of the Naples metropolitan area and inside the Campi Flegrei caldera as part of the Campi Flegrei Deep Drilling Project provided new insight in order to reconstruct the volcano-tectonic evolution of this extremely populated area. Campi Flegrei represents the highest risk volcanic areas in the world, although its volcano-tectonic structure, eruptive history and eruptive style of the largest eruptions are intensely debatedby scientists since several decades. We present here a summary of stratigraphic and geochronological dating (40Ar/39Ar) allowing to define the age of intra-caldera deposits belonging to the two highest magnitude caldera-forming eruptions (i.e. Campania Ignimbrite, 39÷40 ka, and Neapolitan Yellow Tuff, 14.9 ka) and to evaluate the amount of collapse of the eastern sector of the caldera. These results point out: (i) a reduction of the area affected by caldera collapse, which appears to not include the city of Naples; (ii) a small volume of the infilling caldera deposits, particularly for the CI; and (iii) the need for reassessment of the collapse amounts and mechanisms related to larger eruptions. Our results also imply a revaluation of volcanic risk for the eastern caldera area, including the city of Naples. The results of this study point out that large calderas are characterised by complex collapse mechanisms and dynamics, whose understanding needs more robust constraints, which can be obtained from scientific drilling. © 2017 WIT Press,
Keywords: Campania [Italy]; Campi Flegrei; Italy; Napoli [Campania]; Deposits; Geochronology; Hazards; Stratigraphy; Tectonics; Volcanoes; Caldera-forming eruption; Campi Flegrei; Collapse mechanism; Neapolitan yellow tuffs; Scientific drilling; Tectonic evolution; Tectonic structure; Volcanic hazards; caldera; collapse; dating method; geochronology; hazard; metropolitan area; project assessment; reconstruction; tectonic evolution; tectonic structure; volcanic eruption; Infill drilling

The derivation of an anisotropic velocity model from a combined surface and borehole seismic survey in crystalline environment at the COSC-1 borehole, central Sweden - Simon, H.; Krau{s, F.; Giese, R.; Hedin, P.; Juhlin, C. (Geophysical Journal International, 2017)

Interpreting Soft Sediment Deformation and Mass Transport Deposits as Seismites in the Dead Sea Depocenter - Lu, Yin; Waldmann, Nicolas; Ian Alsop, G.; Marco, Shmuel (Journal of Geophysical Research: Solid Earth, 2017)

The variation of paleo-lake environment in the Lower Member 2 of Qingshankou Formation in the Songliao Basin - Cao, Huairen; Hu, Jianfang; Peng, Ping'an; Xi, Dangpeng (Earth Science Frontiers, 2017)
The data of rock-eval and biomarkers in the samples of the Lijiatuozi Section were analyzed for better understanding the paleo-lake environment of the Lower Member 2 of the Qingshankou Formation(K2qn2)in the Songliao Basin. The organic matters (OMs) were mainly originated from aquatic organisms according to plot of hydrogen index (210-773 mg HC/g TOC) and oxygen index (2-188 mg CO2/g TOC) in low maturity source rock. The evolution of paleo-lake environment could be divided into three stages based on geochemical data. In the stage I, low values of gammacerane index and aryl isoprenoid/phenanthrene ratio, corresponding with low ratios of diasterane/sterane and the plot of pristane/phytane and dehydroxyl vitamin-E index, parameters mentioned above all indicated that the lake was considered as being anoxic and brackish water conditions. In the stage II, the occurrence of short time marine incursion was defined by variable contents of 24-n-propyl-cholestanes and 24-i-propyl-cholestanes, leading to semi-deep or deep water environment; seawater intrusion with sea creatures, oxygen, nutrition, organic matter and sulfurous substances, which were helpful with formation of increasing salinity for brackish water and salt water; abundant composition of aryl isoprenoid displayed that stratified lake water was rich in free state of H2S with euphotic zone of anoxia and upward chemocline during this period. However, the lake was dominantly given priority to fresh water to the brackish water deposition with increasing oxygen content at the same time, which suggested that fresh water input increased in the latter stages of stage II. The lake was in high salinity water, anoxia, and the shallow chemocline due to being influenced by semi-arid climate conditions during the sedimentary period of stage III, and turbulent water body was against growth of green sulfur bacteria and preservation of free H2S. © 2017, Editorial Office of Earth Science Frontiers. All right reserved.
Keywords: Aquatic organisms; Bacteria; Biogeochemistry; Biological materials; Biology; Biomarkers; Carbon dioxide; Lakes; Lipids; Organic compounds; Oxygen; Water; Anoxic conditions; Geochemical data; Green sulfur bacteria; Salinity; Semi-arid climate; Songliao basin; Stratified waters; Variable content; Salt water intrusion

Increased sedimentation following the Neolithic Revolution in the Southern Levant - Lu, Yin; Waldmann, Nicolas; Nadel, Dani; Marco, Shmuel (Global and Planetary Change, 2017)

Climatic influence of the latest Antarctic isotope maximum of the last glacial period (AIM4) on Southern Patagonia - Jouve, Guillaume; Lis'e-Pronovost, Agathe; Francus, Pierre; De Coninck, Arnaud S. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2017)

Campanian –Maastrichtian palynomorph from the Sifangtai and Mingshui formations, Songliao Basin, Northeast China: Biostratigraphy and paleoflora - Yoshino, K.; Wan, X.-Q.; Xi, D.-P.; Li, W.; Matsuoka, A. (Palaeoworld, 2017)
We recovered a Campanian –Maastrichtian palynological record in transitional succession from the Sifangtai to Mingshui formations of the Songke Core-1 (North) (SK1 (N)) in the Songliao Basin, Northeast China. These formations are composed mainly of various colored mudstones and sandstones. The lithofacies variation suggests that the paleoenvironment changed from flood plain to lake. Most of the palynomorph assemblages are dominated by gymnosperm pollen, followed by spore of pteridophyte, and angiosperm pollen. On the basis of the first occurrences of marker genera within the succession, we identified four palynomorph interval zones (in ascending order): the Jianghanpollis, Chenopodipollis, Toroisporis, and Betulaceoipollenites interval zones. The first two interval zones are found from flood plain and levee deposits. The third one is recognized from lake basin plain –lake basin slope deposits. The last one is found in delta deposits within lakeshore. We consider that environmental changes are the major factors that formed component of Campanian –Maastrichtian assemblage in the Songliao Basin. In addition, the Jianghanpollis and Chenopodipollis interval zones are assigned to the Campanian, whereas the Toroisporis and Betulaceoipollenites interval zones date as the Maastrichtian. Thus, the Chenopodipollis/Toroisporis zonal boundary approximates the C/M boundary. Triprojectate pollen such as Aquilapollenites is regarded as marker taxa in the study section and other areas within the Aquilapollenites Province during the Campanian –Maastrichtian. However, Wodehouseia spp. have yet been confirmed within the study section, although this genus has appeared in Campanian –Maastrichtian deposits in other areas. This is one of the important clues to understand regional difference of local flora in these ages. © 2016 Elsevier B.V. and Nanjing Institute of Geology and Palaeontology, CAS
cited By 8
Keywords: angiosperm; biostratigraphy; Campanian; core analysis; flora; gymnosperm; lacustrine deposit; levee; lithofacies; lithostratigraphy; Maastrichtian; mudstone; paleoenvironment; palynology; palynomorph; pollen; pteridophyte; sandstone; terrestrial deposit; China; Songliao Basin; Gymnospermae; Magnoliophyta; Pteridophyta

Carbonate and silicate cementation of siliciclastic sediments of the New Jersey shelf (IODP Expedition 313): relation with organic matter diagenesis and submarine groundwater discharge - Pierre, C.; Blanc-Valleron, M.-M.; Boudouma, O.; Lofi, J. (Geo-Marine Letters, 2017)
The New Jersey continental shelf extends 150 km off the shoreline. During IODP Expedition 313, siliciclastic deposits of late Eocene to late Pleistocene age were drilled down to 631, 669 and 755 m below seafloor at sites 27A, 28A and 29A respectively in very shallow waters (33.5 to 36 m depth). Pore water salinities display multilayered brackish-salty-brine units 10 to 170 m thick, where low-salinity water is preferentially stored in fine-grained sediments. The sharp boundaries of these buried aquifers are often marked by cemented layers a few centimetres thick. The mineralogy and scanning electron microscope observations of these layers show two phases of cementation by authigenic minerals: (1) the early carbonate cement is frequently associated with pyrite, and (2) the late silicate cement infills the residual porosity. The isotopic compositions of the carbonate cements vary widely: −2.4 < δ18O ‰ VPDB < +2.8; −15.1 < δ13C ‰ VPDB < +15.6. The δ18O values indicate that the carbonate cements precipitated with pore waters comprising variable mixtures of seawater and 18O-depleted fresh water originating from submarine groundwater discharge. The δ13C values of the carbonate cements are related to organic matter diagenesis, providing 13C-depleted dissolved inorganic carbon during bacterial sulphate reduction and anaerobic oxidation of methane, and 13C-rich dissolved inorganic carbon during methanogenesis. The diagenetic cementation processes included chemical weathering of reactive silicate minerals by the CO2-rich pore waters issued from organic matter diagenesis that released bicarbonate, cations and dissolved silica, which were further precipitated as carbonate and silicate cements. The estimated range of temperature (18±4 °C) during carbonate precipitation is consistent with carbonate cementation at moderate burial depths; however, silicate cementation occurred later during diagenesis at deeper burial depths. © 2017, Springer-Verlag Berlin Heidelberg.
cited By 3
Keywords: Aquifers; Biogeochemistry; Biological materials; Carbon; Carbon dioxide; Carbonation; Cementing (shafts); Discharge (fluid mechanics); Dissolution; Groundwater; Groundwater resources; Hydrogeology; Minerals; Organic compounds; Organic minerals; Scanning electron microscopy; Sedimentology; Silicate minerals; Silicates; Submarines; Water; Weathering; Anaerobic oxidation of methanes; Bacterial sulphate reductions; Carbonate precipitation; Dissolved inorganic carbon; Fine-grained sediment; Pore water salinities; Siliciclastic sediments; Submarine groundwater discharge; Cements; carbonate sediment; cementation; chemical weathering; continental shelf; discharge; groundwater; Ocean Drilling Program; organic matter; silicate mineral; siliciclastic deposit; underwater environment; Atlantic Ocean; New Jersey Shelf; Bacteria (microorganisms)

Cellularly preserved microbial fossils from ∼3.4 Ga deposits of South Africa: A testimony of early appearance of oxygenic life? - Kremer, Barbara; Kaźmierczak, J'ozef (Precambrian Research, 2017)

Chicxulub and the exploration of large peak-ring impact craters through scientific drilling - Kring, D.A.; Claeys, P.; Gulick, S.P.S.; Morgan, J.V.; Collins, G.S.; Bralower, T.; Chenot, E.; Christeson, G.; Cockell, C.; Coolen, M.J.L.; Ferrière, L.; Gebhardt, C.; et al. (GSA Today, 2017)
The Chicxulub crater is the only wellpreserved peak-ring crater on Earth and linked, famously, to the K-T or K-Pg mass extinction event. For the first time, geologists have drilled into the peak ring of that crater in the International Ocean Discovery Program and International Continental Scientific Drilling Program (IODP-ICDP) Expedition 364. The Chicxulub impact event, the environmental calamity it produced, and the paleobiological consequences are among the most captivating topics being discussed in the geologic community. Here we focus attention on the geological processes that shaped the 200-km-wide impact crater responsible for that discussion and the expedition's first year results. Copyright 2017, The Geological Society of America.
cited By 19

Chromium isotope evidence in ejecta deposits for the nature of Paleoproterozoic impactors - Mougel, B'erengère; Moynier, Fr'ed'eric; G{opel, Christa (Earth and Planetary Science Letters, 2017)

Chronologies of Late Quaternary Coral Reefs and Lake Sediments from the Red Sea and Dead Sea Rift Valley - Stein, Mordechai; Lazar, Boaz; Torfstein, Adi; Goldstein, Steven L. (Quaternary of the Levant: Environments, Climate Change, and Humans, 2017)

Contamination Control for Scientific Drilling Operations - Kallmeyer, J. (Advances in Applied Microbiology, 2017)
Drilling is an integral part of subsurface exploration. Because almost all drilling operations require the use of a drill fluid, contamination by infiltration of drill fluid into the recovered core material cannot be avoided. Because it is impossible to maintain sterile conditions during drilling the drill fluid will contain surface microbes and other contaminants. As contamination cannot be avoided, it has to be tracked to identify those parts of the drill core that were not infiltrated by the drill fluid. This is done by the addition of tracer compounds. A great variety of tracers is available, and the choice depends on many factors. This review will first explain the basic principles of drilling before presenting the most common tracers and discussing their strengths and weaknesses. The final part of this review presents a number of key questions that have to be addressed in order to find the right tracer for a particular drilling operation. © 2017 Elsevier Inc.
Keywords: Bacteria; Ecosystem; Extraction and Processing Industry; Geologic Sediments; Humans; fluorescent dye; fluorocarbon; microsphere; tracer; Article; drill; ecological procedures; extended core barrel; gravity; hydraulic piston coring; microbial contamination; nonhuman; rotary drilling; tube; wireline coring; bacterium; chemistry; devices; ecosystem; genetics; growth; development and aging; human; isolation and purification; microbiology; mining; procedures; sediment

Biomarkers in Lake Van sediments reveal dry conditions in eastern Anatolia during 110.000 –10.000 years B.P. - Randlett, M.-E.; Bechtel, A.; Meer, M.T.J.; Peterse, F.; Litt, T.; Pickarski, N.; Kwiecien, O.; Stockhecke, M.; Wehrli, B.; Schubert, C.J. (Geochemistry, Geophysics, Geosystems, 2017)
Lipid biomarkers were analyzed in Lake Van sediments covering the last 600 ka, with a focus on the period between 110 and 10 ka, when a broad maximum in pore water salinity as a relict from the past suggests dry conditions. The occurrence and distribution of biomarkers indicative for terrestrial plants (long-chain n-alkane C29), haptophyte algae (methyl alkenones C37) and halophilic archaea (archaeol) all point toward a dry climate in Lake Van region during this time interval. The hydrogen isotopic composition of C29 n-alkanes (δDC29) and C37 alkenones (δDC37) is enriched between MIS 4 and MIS 2, which is interpreted as a decrease in the regional ratio of precipitation to evaporation. Similarly, the low abundance of the acyclic glycerol dialkyl glycerol tetraether GDGT-0 relative to archaeol, quantified by the Archaeol and Caldarchaeol Ecometric (ACE) is assumed to reflect the presence of halophilic euryarchaeota adapted to high salinity water. The climate around Lake Van appears in phase with the Yammouneh basin 800 km southwest and Lake Urmia 250 km southeast of Lake Van over the last two glacial periods. The results highlight the potential of combining ACE, δDC29, and δDC37 for reconstructing salinity changes and regional precipitation to evaporation ratio from lake sediments. © 2017. American Geophysical Union. All Rights Reserved.
cited By 19
Keywords: Evaporation; Glycerol; Isotopes; Lakes; Paraffins; Sediments; ACE index; Halophilic archaea; Hydrogen isotope; Hydrogen isotopic composition; Lake vans; Long chain n-alkanes; Occurrence and distribution; Pore water salinities; Biomarkers; biomarker; hydrogen isotope; isotopic composition; lacustrine deposit; lipid; paleoclimate; porewater; salinity; Anatolia; Lake Van; Turkey; algae; Euryarchaeota

Contamination Control for Scientific Drilling Operations - Kallmeyer, J. (Advances in Applied Microbiology, 2017)
Drilling is an integral part of subsurface exploration. Because almost all drilling operations require the use of a drill fluid, contamination by infiltration of drill fluid into the recovered core material cannot be avoided. Because it is impossible to maintain sterile conditions during drilling the drill fluid will contain surface microbes and other contaminants. As contamination cannot be avoided, it has to be tracked to identify those parts of the drill core that were not infiltrated by the drill fluid. This is done by the addition of tracer compounds. A great variety of tracers is available, and the choice depends on many factors. This review will first explain the basic principles of drilling before presenting the most common tracers and discussing their strengths and weaknesses. The final part of this review presents a number of key questions that have to be addressed in order to find the right tracer for a particular drilling operation. © 2017 Elsevier Inc.
cited By 10
Keywords: fluorescent dye; fluorocarbon; microsphere; tracer; Article; drill; ecological procedures; extended core barrel; gravity; hydraulic piston coring; microbial contamination; nonhuman; rotary drilling; tube; wireline coring; bacterium; chemistry; devices; ecosystem; genetics; growth; development and aging; human; isolation and purification; microbiology; mining; procedures; sediment; Bacteria; Ecosystem; Extraction and Processing Industry; Geologic Sediments; Humans

Core Spatial Position Restoring of the CCSDSK-2 East Borehole in the Songliao Basin of Northeast China (in Chinese with English abstract); [松辽盆地科学钻探工程松科2井东孔岩心空间归位] - Li, N.; Zou, C.; Peng, C.; Zhao, J.; Niu, Y. (Geological Science and Technology Information, 2017)

Cross-correlation-based detection and characterisation of microseismicity adjacent to the locked, late-interseismic Alpine Fault, South Westland, New Zealand - Chamberlain, C.J.; Boese, C.M.; Townend, J. (Earth and Planetary Science Letters, 2017)
The Alpine Fault is inferred on paleoseismological grounds to produce magnitude 8 earthquakes approximately every 330 yrs and to have last ruptured almost 300 yrs ago in 1717 AD. Despite approximately 90% of its typical interseismic period having elapsed since the last major earthquake, the Alpine Fault exhibits little present-day microseismicity and no geodetic evidence for shallow creep. Determining the mechanical state of the fault ahead of a future earthquake is a key objective of several studies, including the Deep Fault Drilling Project (DFDP). Here we use a network of borehole seismometers installed in conjunction with DFDP to detect and characterise low-magnitude seismicity adjacent to the central section of the Alpine Fault. We employ matched-filter detection techniques, automated cross-correlation phase picking, and singular value decomposition-derived magnitude estimation to construct a high-precision catalogue of 283 earthquakes within 5 km of the fault trace in an otherwise seismically quiet zone. The newly recognised seismicity occurs in non-repeating, spatially and temporally limited sequences, similar to sequences previously documented using standard methods but at significantly lower magnitudes of ML <1.8. These earthquakes are not clustered on a single distinctive structure, and we infer that they are distributed throughout a highly fractured zone surrounding the Alpine Fault. Focal mechanisms computed for 13 earthquakes using manual polarity picks exhibit predominantly strike-slip faulting, consistent with focal mechanisms observed further from the fault. We conclude that the Alpine Fault is locked and accumulating strain throughout the seismogenic zone at this location. © 2016 Elsevier B.V.
cited By 17
Keywords: Fault detection; Locks (fasteners); Matched filters; Seismic waves; Seismographs; Signal detection; Singular value decomposition; Strike-slip faults; Alpine Faults; Earthquake swarms; Inter-seismic periods; Magnitude estimation; Matched filter detections; Microseismicity; South Westland; New Zealand; Strike slip faulting; Earthquakes; detection method; earthquake magnitude; earthquake swarm; fault zone; focal mechanism; seismicity; singular value decomposition; Alpine Fault Zone; New Zealand; South Island

Cyclical Changes in the Pleistocene Climate from an Analysis of Biogenic Silica in a Bottom Sediment Core Sample of Lake Baikal - Dergachev, V.A.; Dmitriev, P.B. (Geomagnetism and Aeronomy, 2017)
An inhomogeneous time series of measurements of the percentage content of biogenic silica in the samples of joint cores BDP-96-1 and BDP-96-2 from the bottom of Lake Baikal drilled at a depth of 321 m under water has been analyzed. The composite depth of cores is 77 m, which covers the Pleistocene Epoch to 1.8 Ma. The time series was reduced to a regular form with a time step of 1 kyr, which allowed 16 distinct quasi-periodic components with periods from 19 to 251 kyr to be revealed in this series at a significance level of their amplitudes exceeding 4σ. For this, the combined spectral periodogram (a modification of the spectral analysis method) was used. Some of the revealed quasi-harmonics are related to the characteristic cyclical oscillations of the Earth’s orbital parameters. Special focus was payed to the temporal change in the parameters of the revealed quasi-harmonic components over the Pleistocene Epoch, which was studied by constructing the spectral density of the analyzed data in the running window of 201 and 701 kyr. © 2017, Pleiades Publishing, Ltd.

Dead Sea Lake Level Changes and Levant Palaeoclimate - Torfstein, Adi; Enzel, Yehouda (Quaternary of the Levant: Environments, Climate Change, and Humans, 2017)

Deep drilling at the Chalco lake: A technical report [Perforaci'on profunda en el lago de Chalco: Reporte t'ecnico] - Lozano-Garc'ia, S.; Brown, E.T.; Ortega, B.; Caballero, M.; Werne, J.; Fawcett, P.J.; Schwalb, A.; Valero-Garc'es, B.L.; Schnurrenberger, D.; O'Grady, R.; Stockhecke, M.; Steinman, B.; et al. (Boletin de la Sociedad Geologica Mexicana, 2017)
This paper presents a short description of the coring operations undertaken to recover the full lacustrine sedimentary sequence from Chalco. Geophysical techniques were used to determine the distribution and thickness of the sediments in order to select the drilling site. Resonance frequencies determined from H/V spectral ratios were used to determine an area where lake sediments reached 300 m thickness. Electromagnetic survey showed two changes in electric resistivity which were related to changes in sediment composition, the first from 100 to 120 m, related to an increase in volcanoclastic sediments and the second from 330 to 400 m related to the presence of a basaltic flows. Three wells were drilled with continuous recovery, reaching depths of 420 m in well A, 310 in B and 520 in C. Samples for geomicrobiological and metagenomics studies were collected during drilling operations. A total of 1152 m of core sediments were recovered reaching a maximum depth of 520 m. Recovery percentages were between 88 and 92 % in the three wells. Magnetic susceptibility analyses in the three sequences show that the first 260 m are mostly lake sediments, between 260 and 300 m sediments are coarser and below 300 m they are mostly volcaniclastic. Analysis of the sedimentary sequence of Lake Chalco that covers the last 300000 years will allow documenting and extending the knowledge of climate variability in area, the paleoenvironmental history, basin closure history, lacustrian system development and volcanic activity recurrence. Studies of the physical properties of this sequence will be important for seismic propagation and basin structure modeling, and also will improve modeling of the subsidence process that this region experiences.
cited By 19

Call for models-A test case for the source inversion validation: The 2014 ML 5.5 Orkney, South Africa, Earthquake - Moyer, Pamela A.; Boettcher, Margaret S.; Ellsworth, William L.; Ogasawara, Hiroshi; Cichowicz, Artur; Birch, Denver; Van Aswegen, Gerhard (Seismological Research Letters, 2017)

Bedrock geology of DFDP-2B, central Alpine Fault, New Zealand - Toy, V.G.; Sutherland, R.; Townend, J.; Allen, M.J.; Becroft, L.; Boles, A.; Boulton, C.; Carpenter, B.; Cooper, A.; Cox, S.C.; Daube, C.; Faulkner, D.R.; et al. (New Zealand Journal of Geology and Geophysics, 2017)
During the second phase of the Alpine Fault, Deep Fault Drilling Project (DFDP) in the Whataroa River, South Westland, New Zealand, bedrock was encountered in the DFDP-2B borehole from 238.5 –893.2 m Measured Depth (MD). Continuous sampling and meso- to microscale characterisation of whole rock cuttings established that, in sequence, the borehole sampled amphibolite facies, Torlesse Composite Terrane-derived schists, protomylonites and mylonites, terminating 200 –400 m above an Alpine Fault Principal Slip Zone (PSZ) with a maximum dip of 62°. The most diagnostic structural features of increasing PSZ proximity were the occurrence of shear bands and reduction in mean quartz grain sizes. A change in composition to greater mica:quartz + feldspar, most markedly below c. 700 m MD, is inferred to result from either heterogeneous sampling or a change in lithology related to alteration. Major oxide variations suggest the fault-proximal Alpine Fault alteration zone, as previously defined in DFDP-1 core, was not sampled. © 2017 The Royal Society of New Zealand.
cited By 22
Keywords: bedrock; cataclasite; core analysis; drilling; fault zone; mylonite; sedimentary sequence; shear band; slip rate; structural geology; Alpine Fault Zone; New Zealand; South Island

Deep in a South African gold mine, scientists drill for the heart of an earthquake - Voosen, P. (Science, 2017)

A new high-resolution pollen sequence at Lake Van, Turkey: Insights into penultimate interglacial-glacial climate change on vegetation history - Pickarski, N.; Litt, T. (Climate of the Past, 2017)
A new detailed pollen and oxygen isotope record of the penultimate interglacial-glacial cycle, corresponding to the marine isotope stage (MIS) 7-6, has been generated from the Ahlat Ridge (AR) sediment core at Lake Van, Turkey. The presented Lake Van pollen record (ca. 250.2-128.8 ka) displays the highest temporal resolution in this region with a mean sampling interval of ĝ1/4 540 years. The integration of all available proxies shows three temperate intervals of high effective soil moisture availability. This is evidenced by the predominance of steppe-forested landscapes (oak steppe-forest) similar to the present interglacial vegetation in this sensitive semiarid region between the Black Sea, the Caspian Sea, and the Mediterranean Sea. The wettest and warmest stage, as indicated by highest temperate tree percentages, can be broadly correlated with MIS 7c, while the amplitude of the tree population maximum during the oldest penultimate interglacial (MIS 7e) appears to be reduced due to warm but drier climatic conditions. The detailed comparison of the penultimate interglacial complex (MIS 7) to the last interglacial (Eemian, MIS 5e) and the current interglacial (Holocene, MIS 1) provides a vivid illustration of possible differences in the successive climatic cycles. Intervening periods of treeless vegetation can be correlated with MIS 7d and 7a, in which open landscapes favor local erosion and detrital sedimentation. The predominance of steppe elements (e.g., Artemisia, Chenopodiaceae) during MIS 7d indicates very dry and cold climatic conditions. In contrast, the occurrence of higher temperate tree percentages (mainly deciduous Quercus) throughout MIS 7b points to relatively humid and mild conditions, which is in agreement with other pollen sequences in southern Europe. Despite the general dominance of dry and cold desert-steppe vegetation during the penultimate glacial (broadly equivalent to MIS 6), this period can be divided into two parts: an early stage (ca. 193-157 ka) with higher oscillations in tree percentages and a later stage (ca. 157-131 ka) with lower tree percentages and subdued oscillations. This subdivision of the penultimate glacial is also seen in other pollen records from southern Europe (e.g., MD01-2444 and I-284; Margari et al., 2010; Roucoux et al., 2011). The occurring vegetation pattern is analogous to the division of MIS 3 and MIS 2 during the last glacial in the same sediment sequence. Furthermore, we are able to identify the MIS 6e event (ca. 179-159 ka) as described in marine pollen records, which reveals clear climate variability due to rapid alternation in the vegetation cover. In comparison with long European pollen archives, speleothem isotope records from the Near East, and global climate parameters (e.g., insolation, atmospheric CO2 content), the new high-resolution Lake Van record presents an improved insight into regional vegetation dynamics and climate variability in the eastern Mediterranean region. © Author(s) 2017.
cited By 26
Keywords: climate variation; core analysis; forest-steppe; glacial-interglacial cycle; marine isotope stage; oxygen isotope; paleoecology; paleoenvironment; palynology; proxy climate record; soil moisture; vegetation history; Black Sea; Caspian Sea; Lake Van; Mediterranean Sea; Turkey; Amaranthaceae; Artemisia; Quercus

Implications of S1 tephra findings in Dead Sea and Tayma palaeolake sediments for marine reservoir age estimation and palaeoclimate synchronisation - Neugebauer, I.; Wulf, S.; Schwab, M.J.; Serb, J.; Plessen, B.; Appelt, O.; Brauer, A. (Quaternary Science Reviews, 2017)
Here we report on the first findings of a cryptotephra in the Holocene lacustrine sediment records of the Dead Sea and Tayma palaeolake (NW Arabian Peninsula). The major element glass composition of this rhyolitic tephra is identical to the distal S1’ tephra layer identified in the Yammoûneh palaeolake (Lebanon), in a marine sediment record from the SE Levantine basin and in the Sodmein Cave archaeological site in Egypt. The S1 tephra corresponds to the early Holocene Dikkartın’ dome eruption of the Erciyes Dağ volcano in central Anatolia (Turkey) and has been dated in the marine record at 8830 ± 140 cal yr BP. We present new age estimates of the S1 tephra based on radiocarbon dating of terrestrial plant remains and pollen concentrates revealing ages of 8939 ± 83 cal yr BP in the Dead Sea sediments and 9041 ± 254 cal yr BP in Tayma. The precise date from the Dead Sea allows refining the early Holocene marine reservoir age in the SE Levantine Sea to ca. 320 ± 50 years. Synchronisation of marine and terrestrial palaeoclimate records in the eastern Mediterranean region using the S1 tephra further suggests a time-transgressive expansion of the early Holocene humid period. © 2017 Elsevier Ltd
cited By 11
Keywords: Plants (botany); Reservoirs (water); Submarine geology; Early Holocene; Eastern Mediterranean; Lake sediments; Marine reservoir age; NW Arabian Peninsula; Palaeoclimate; S1 tephra; Tephrochronology; Sediments; age determination; Holocene; lacustrine deposit; marine environment; marine record; marine sediment; paleoclimate; radiocarbon dating; tephra; tephrochronology; volcano; Anatolia; Arabian Peninsula; Dead Sea; Egypt; Lebanon; Levantine Sea; Mediterranean Region; Mediterranean Sea; Red Sea [(GVR) Egypt]; Saudi Arabia; Sodmein Cave; Tabuk [Saudi Arabia]; Tayma; Turkey

3-D P- And S-wave velocity structure along the central Alpine Fault, South Island, New Zealand - Guo, B.; Thurber, C.H.; Roecker, S.W.; Townend, J.; Rawles, C.; Chamberlain, C.J.; Boese, C.M.; Bannister, S.; Feenstra, J.; Eccles, J.D. (Geophysical Journal International, 2017)
The Deep Fault Drilling Project (DFDP) on the central Alpine Fault, South Island, New Zealand, has motivated a broad range of geophysical and geological studies intended to characterize the fault system in the locality of the drill site at various scales. In order to better understand the structural features of the central Alpine Fault, we have developed 3-D P- and S-wave velocity (VP and VS) models of the region by double-difference tomography using data sets from multiple seismic networks. In previous work, the quality of the S-wave model has been poor due to the small number of available S-wave picks. We have utilized a new high-accuracy automatic S-wave picker to increase the number of usable S-wave arrivals by more than a factor of two, thereby substantially improving the VS model. Compared to previous studies, our new higher-resolution VP model based on more observations shows a clear VP contrast (higher VP on the southeast hanging wall side) at depths of 5-10 km near the DFDP drill sites. With our better resolved VS model, in the same region, we detect a sharply defined high VS body (VS > 3.7 km s-1) within the hanging wall. Our earthquake relocations reveal the presence of clusters within and around low-velocity zones in the hanging wall southeast of the Alpine Fault. Together with the improved earthquake locations, the P- and S-wave tomography results reveal the Alpine Fault to be marked by a velocity contrast throughout most of the study region. The fault dips southeastwards at about 50° from 5 to 15 km depth, as inferred from the velocity structure, seismicity and observations of fault zone guided waves. © 2017 The Authors 2017. Published by Oxford University Press on behalf of The Royal Astronomical Society.
cited By 8
Keywords: Acoustic wave velocity; Drills; Earthquakes; Faulting; Guided electromagnetic wave propagation; Infill drilling; Tomography; Double-difference tomography; Earthquake location; Earthquake relocation; P- and S-wave velocities; South Island; New Zealand; Structural feature; Velocity contrasts; Velocity structure; Shear waves

50 Years of 10 December 1967 M 6.3 Koyna earthquake: Preface - Gupta, H.K. (Journal of the Geological Society of India, 2017)
cited By 6

A ∼6000 yr diatom record of mid- to late Holocene fluctuations in the level of Lago Wiñaymarca, Lake Titicaca (Peru/Bolivia) - Weide, D. Marie; Fritz, Sherilyn C.; Hastorf, Christine A.; Bruno, Maria C.; Baker, Paul A.; Gu'edron, St'ephane; Salenbien, Wout (Quaternary Research (United States), 2017)
A multidecadal-scale lake-level reconstruction for Lago Wiñaymarca, the southern basin of Lake Titicaca, has been generated from diatom species abundance data. These data suggest that 6500 cal yr BP Lago Wiñaymarca was dry, as indicated by a sediment unconformity. At 4400 cal yr BP, the basin began to fill, as indicated by the dominance of shallow epiphytic species. It remained somewhat saline with extensive wetlands and abundant aquatic plants until 3800 cal yr BP, when epiphytic species were replaced by planktic saline-indifferent species, suggesting a saline shallow lake. Wiñaymarca remained a relatively shallow lake that fluctuated on a multidecadal scale until 1250 cal yr BP, when freshwater planktic species increased, suggesting a rise in lake level with a concomitant decrease in salinity. The lake became gradually fresher, dominated by deep, freshwater species from 850 cal yr BP. By 80 cal yr BP, saline-tolerant species were rare, and the lake was dominated by freshwater planktic diatoms, resembling the fresh and deep lake of today. These results reveal a more dynamic and chronologically specific record of lake-level fluctuations and associated ecological conditions that provide important new data for paleoclimatologists and archaeologists, to better understand human-environmental dynamics during the mid- to late Holocene. Copyright © University of Washington. Published by Cambridge University Press, 2017.
Keywords: Bacillariophyta; Phytoplankton; Water; Concomitant decrease; Ecological conditions; Environmental dynamics; Holocenes; Lake level fluctuations; Lake levels; Mid to late Holocene; Tropical Andes; Lakes

A comparison of the use of X-ray and neutron tomographic core scanning techniques for drilling projects: Insights from scanning core recovered during the Alpine Fault Deep Fault Drilling Project - Williams, J.N.; Bevitt, J.J.; Toy, V.G. (Scientific Drilling, 2017)
It is now commonplace for non-destructive X-ray computed tomography (CT) scans to be taken of core recovered during a drilling project. However, other forms of tomographic scanning are available, and these may be particularly useful for core that does not possess significant contrasts in density and/or atomic number to which X-rays are sensitive. Here, we compare CT and neutron tomography (NT) scans of 85mm diameter core recovered during the first phase of the Deep Fault Drilling Project (DFDP-1) through New Zealand's Alpine Fault. For the instruments used in this study, the highest resolution images were collected in the NT scans. This allows clearer imaging of some rock features than in the CT scans. However, we observe that the highly neutron beam attenuating properties of DFDP-1 core diminish the quality of images towards the interior of the core. A comparison is also made of the suitability of these two scanning techniques for a drilling project. We conclude that CT scanning is far more favourable in most circumstances. Nevertheless, it could still be beneficial to take NT scans over limited intervals of suitable core, where varying contrast is desired. © Author(s) 2017.
cited By 3
Keywords: Atoms; Neutrons; Recovery; Scanning; Tomography; Atomic numbers; Drilling projects; Highest resolutions; Neutron tomography; Non destructive; Scanning techniques; Tomographic scanning; X-ray computed tomography; Computerized tomography

A magnetotelluric investigation of the Scandinavian Caledonides in western J{amtland, Sweden, using the COSC borehole logs as prior information - Yan, Ping; Garcia Juanatey, Maria A.; Kalscheuer, Thomas; Juhlin, Christopher; Hedin, Peter; Savvaidis, Alexandros; Lorenz, Henning; K{uck, Jochem (Geophysical Journal International, 2017)
Keywords: inverse theory; Magnetotellurics; Europe; Downhole methods; Continental tectonics

A numerical approach for modelling fault-zone trapped waves - Gulley, A.K.; Kaipio, J.P.; Eccles, J.D.; Malin, P.E. (Geophysical Journal International, 2017)
We develop a computationally efficient approach to compute the waveforms and the dispersion curves for fault-zone trapped waves guided by arbitrary transversely isotropic across-fault velocity models. The approach is based on a Green's function type representation for FL and FR type fault-zone trapped waves. The model can be used for simulation of the waveforms generated by both infinite line sources (2-D) and point sources (3-D). The numerical scheme is based on a high order finite element approximation and, to increase computational efficiency, we make use of absorbing boundary conditions and mass lumping of finite element matrices. © The Authors 2017.
cited By 7
Keywords: Finite element method; Guided electromagnetic wave propagation; Water waves; Absorbing boundary condition; Computationally efficient; Fault-zone trapped waves; Finite element matrices; High-order finite elements; Numerical approximations and analysis; Numerical solution; Seismic anisotropy; Computational efficiency; boundary condition; fault zone; finite element method; Green function; numerical model; seismic anisotropy; transverse isotropy; trapped wave; wave generation; waveform analysis

Attenuation tomography in West Bohemia/Vogtland - Mousavi, S.; Haberland, C.; Hejrani, B.; Korn, M. (Tectonophysics, 2017)
We present a three-dimensional (3-D) P-wave attenuation (Qp) model for the geodynamically active swarm earthquake area of West Bohemia/Vogtland in the Czech/German border region. Path-averaged attenuation t* is calculated from amplitude spectra of time windows around the P-wave arrivals of local earthquakes. Average t/t* value or Qp for stations close to Nov'y Kostel are very low (< 150) compared to that of stations located further away from the focal zone (increases up to 500 within 80 km distance). The SIMUL2000 tomography scheme is used to invert the t* for P-wave attenuation perturbation. Analysis of resolution shows that our model is well-resolved in the vicinity of earthquake swarm hypocenters. The prominent features of the model are located around Nov'y Kostel focal zone and its northern vicinity. Beneath Nov'y Kostel a vertically stretched (down to depth of 11 km) and a highly attenuating body is observed. We believe that this is due to fracturing and high density of cracks inside the weak earthquake swarm zone in conjunction with presence of free gas/fluid. Further north of Nov'y Kostel two highly attenuating bodies are imaged which could represent fluid channels toward the surface. The eastern anomaly shows a good correlation with the fluid accumulation area which was suggested in 9HR seismic profile. © 2016 Elsevier B.V.
cited By 13
Keywords: Seismic waves; Body waves; Earthquake swarms; Europe; Seismic attenuation; Seismic tomography; Earthquakes; amplitude; body wave; earthquake hypocenter; earthquake swarm; P-wave; seismic attenuation; seismic tomography; seismicity; structural geology; Bohemia; Czech Republic; Germany; Vogtland

A simple and inexpensive technique for assessing contamination during drilling operations - Friese, Andr'e; Kallmeyer, Jens; Kitte, Jan Axel; Mart'inez, Ivan Montaño; Bijaksana, Satria; Wagner, Dirk (Limnology and Oceanography: Methods, 2017)
Subsurface exploration relies on drilling. Normally drilling requires a drilling fluid that will infiltrate into the drill core. Drilling fluid contains non-indigenous materials and microbes from the surface, so its presence renders a sample unsuitable for microbiological and many other analyses. Because infiltration cannot be avoided, it is of paramount importance to assess the degree of contamination to identify uncontaminated samples for geomicrobiological investigations. To do this, usually a tracer is mixed into the drilling fluid. In past drilling operations a variety of tracers have been used, each has specific strengths and weaknesses. For microspheres the main problem was the high price, which limited their use to spot checks or drilling operations that require only small amounts of drilling fluid. Here, we present a modified microsphere tracer approach that uses an aqueous fluorescent pigment dispersion with a similar concentration of fluorescent particles as previously used microsphere tracers. However, it costs four orders of magnitude less, allowing for a more liberal use even in large operations. Its applicability for deep drilling campaigns was successfully tested during two drilling campaigns of the International Continental Drilling Program (ICDP) at Lake Towuti, Sulawesi, Indonesia, and Lake Chalco, Mexico. Quantification of the tracer requires only a fluorescence microscope or a flow cytometer. The latter allowing for high-resolution data to be obtained directly on-site within minutes and with minimal effort, decreasing sample processing times substantially relative to traditional tracer methods. This approach offers an inexpensive, rapid, but powerful alternative technique for contamination assessment during drilling campaigns. © 2017 Association for the Sciences of Limnology and Oceanography.

A simple and inexpensive technique for assessing contamination during drilling operations - Friese, A.; Kallmeyer, J.; Kitte, J.A.; Mart'inez, I.M.; Bijaksana, S.; Wagner, D.; Team, ICDP Lake Chalco Drilling Science; Team (Limnology and Oceanography: Methods, 2017)
Subsurface exploration relies on drilling. Normally drilling requires a drilling fluid that will infiltrate into the drill core. Drilling fluid contains non-indigenous materials and microbes from the surface, so its presence renders a sample unsuitable for microbiological and many other analyses. Because infiltration cannot be avoided, it is of paramount importance to assess the degree of contamination to identify uncontaminated samples for geomicrobiological investigations. To do this, usually a tracer is mixed into the drilling fluid. In past drilling operations a variety of tracers have been used, each has specific strengths and weaknesses. For microspheres the main problem was the high price, which limited their use to spot checks or drilling operations that require only small amounts of drilling fluid. Here, we present a modified microsphere tracer approach that uses an aqueous fluorescent pigment dispersion with a similar concentration of fluorescent particles as previously used microsphere tracers. However, it costs four orders of magnitude less, allowing for a more liberal use even in large operations. Its applicability for deep drilling campaigns was successfully tested during two drilling campaigns of the International Continental Drilling Program (ICDP) at Lake Towuti, Sulawesi, Indonesia, and Lake Chalco, Mexico. Quantification of the tracer requires only a fluorescence microscope or a flow cytometer. The latter allowing for high-resolution data to be obtained directly on-site within minutes and with minimal effort, decreasing sample processing times substantially relative to traditional tracer methods. This approach offers an inexpensive, rapid, but powerful alternative technique for contamination assessment during drilling campaigns. © 2017 Association for the Sciences of Limnology and Oceanography.
cited By 18

Active Magmatic Underplating in Western Eger Rift, Central Europe - Hrubcov'a, Pavla; Geissler, Wolfram H.; Br{auer, Karin; Vavryčuk, V'aclav; Tomek, Čestm'ir; K{ampf, Horst (Tectonics, 2017)
The Eger Rift is an active element of the European Cenozoic Rift System associated with intense Cenozoic intraplate alkaline volcanism and system of sedimentary basins. The intracontinental Cheb Basin at its western part displays geodynamic activity with fluid emanations, persistent seismicity, Cenozoic volcanism, and neotectonic crustal movements at the intersections of major intraplate faults. In this paper, we study detailed geometry of the crust/mantle boundary and its possible origin in the western Eger Rift. We review existing seismic and seismological studies, provide new interpretation of the reflection profile 9HR, and supplement it by new results from local seismicity. We identify significant lateral variations of the high-velocity lower crust and relate them to the distribution and chemical status of mantle-derived fluids and to xenolith studies from corresponding depths. New interpretation based on combined seismic and isotope study points to a local-scale magmatic emplacement at the base of the continental crust within a new rift environment. This concept of magmatic underplating is supported by detecting two types of the lower crust: a high-velocity lower crust with pronounced reflectivity and a high-velocity reflection-free lower crust. The character of the underplated material enables to differentiate timing and tectonic setting of two episodes with different times of origin of underplating events. The lower crust with high reflectivity evidences magmatic underplating west of the Eger Rift of the Late Variscan age. The reflection-free lower crust together with a strong reflector at its top at depths of 28 –30 km forms a magma body indicating magmatic underplating of the late Cenozoic (middle and upper Miocene) to recent. Spatial and temporal relations to recent geodynamic processes suggest active magmatic underplating in the intracontinental setting. ©2017. American Geophysical Union. All Rights Reserved.
Keywords: Eger; Heves; Hungary; Alkalinity; Reflection; Seismology; Velocity; Alkaline volcanism; Continental crusts; Eger Rift; Geodynamic process; Lateral variations; Lower crust; Magma bodies; Underplating; crust-mantle boundary; crustal movement; geodynamics; intraplate process; magmatic differentiation; rift zone; seismic reflection; underplating; Geodynamics

Ambient noise tomography of the western Corinth Rift, Greece - Giannopoulos, Dimitrios; Rivet, Diane; Sokos, Efthimios; Deschamps, Anne; Mordret, Aurelien; Lyon-Caen, H'elène; Bernard, Pascal; Paraskevopoulos, Paraskevas; Tselentis, G-Akis (Geophysical Journal International, 2017)
Three years of continuous waveform data recorded at 22 stations from the Corinth Rift Laboratory and the Hellenic Unified Seismological Network are used to perform an ambient noise surface wave tomography of the western Corinth Rift. All available vertical component time-serieswere cross-correlated to extract empirical Rayleigh-wave Green's functions. Group velocity dispersion curves were measured for each station-pair by applying frequency-time analysis and then inverted to build 2-D group velocity maps between 1 and 6 s period. Finally, we locally inverted these velocity maps using a neighbourhood algorithm to assess the 3-D shear-velocity model of the shallow crustal structure of the western Corinth Rift. Across all studied periods the southern coast of the Corinth Gulf is generally imaged as a region of lower velocities compared to the northern coast. At periods up to 3 s, the spatial variation of the group velocities is correlated with the surface geology of the area. Lower velocities are observed in areas where mostly Plio-Quaternary syn-rift sediments are present, such as offshore regions of the rift, the Mornos delta and the largest part of the southern coast. Higher velocities are observed in pre-rift basement structures which are dominated mostly by carbonates. At periods above 3 s, where Rayleigh-waves begin to sense deeper structures below the sediments within the underlying basement, our study highlights the presence of a distinct zone of lower velocities across the southern part of the rift with an elongation in the WNW-ESE direction. The interpretation of this low velocity includes two arguments, the present-day active tectonic regime and the possible involvement of fluids circulation processes at depth within a highly fractured upper crust in the vicinity of the major faults zones. In general, the results demonstrate good agreement with the major geological and tectonic features of the area, as well as with previous local earthquake tomography studies and support the assumption of fluid circulations at depth. This work intends to be the base for further investigations towards the study of the Corinth Rift structure using long-time series of ambient noise data. © The Authors 2017.
Keywords: Corinth Rift; Greece; Gulf of Corinth; Ionian Sea; Mediterranean Sea; Acoustic noise; Buildings; Coastal engineering; Group velocity dispersion; Interferometry; Light velocity; Rayleigh waves; Seismology; Surface waves; Tectonics; Three dimensional computer graphics; Ambient noise tomographies; Continuous waveforms; Crustal structure; Group velocity dispersion curve; Neighbourhood algorithms; Seismic tomography; Shear velocity models; Surface-wave tomography; algorithm; ambient noise; crustal structure; Green function; Rayleigh wave; seismic velocity; seismology; tomography; Shear flow

Application of geochemical logging for palaeoenvironmental research in the Late Cretaceous Qingshankou Formation from the Chinese Continental Scientific Drilling Project-SK-2e, Songliao Basin, NE China - Peng, Cheng; Zou, Changchun; Pan, Li; Niu, Yixiong (Journal of Geophysics and Engineering, 2017)
The Chinese Continental Scientific Drilling Project of the Cretaceous Songliao Basin (CCSD-SK) provides an excellent opportunity to understand the response of terrestrial environments to greenhouse climate change in the Cretaceous. We conducted a palaeoenvironmental study of the Late Cretaceous Qingshankou Formation (K2qn) based on geochemical log data from the SK-2 east borehole. According to the characteristic of Ti mainly from terrigenous minerals, the content of authigenic elements was calculated. Correlation space was proposed to study the variation of the correlation between two log curves along the depth. Palaeoenvironmental proxies were selected from log data to study the evolution of the climate and lake, productivity of the paleolake, and organic matter deposition. The results demonstrate that the productivity of the paleolake was driven by chemical weathering in K2qn, in which the first section of the Qingshankou Formation (K2qn1) has higher productivity than the second and third sections of the Qingshankou Formation (K2qn2+3). The high content of pyrite in several thin layers reveals lake water of high sulfate concentration. This may have been caused by acid rain related to large volcanic activity. In K2qn2+3, several periods of high productivity without the formation of source rocks and high organic matter content were identified. This may show that organic matter deposition was limited by low accommodation space or oxidation environment. Therefore, the preservation condition is suggested as the main controlling factor of organic matter deposition in K2qn. © 2017 Sinopec Geophysical Research Institute.
Keywords: China; Songliao Basin; borehole; Chinese Continental Scientific Drilling Project; Cretaceous; deposition; environmental research; geochemistry; organic matter; paleoenvironment; productivity; proxy climate record; source rock; terrigenous deposit

Architecture and temporal variations of a terrestrial CO2 degassing site using electric resistivity tomography and self-potential - Nickschick, T.; Flechsig, C.; Meinel, C.; Mrlina, J.; K{ampf, H. (International Journal of Earth Sciences, 2017)
The Hartoušov mofette field in NW Bohemia, Czech Republic, is characterized by strong CO2 degassing from the Lithospheric Mantle. In a test survey using electrical resistivity tomography, we observed changes over time in the subsurface structure beneath heavily CO2 degassing spots to depths of about 40 m and compared them to CO2 gas flux and soil gas mappings from previous studies. Changes in the electrical resistivity were measured between September 2012 and October 2013 at irregular intervals and highlight large variations in the resistivity distribution where the CO2 degassing was strongest (56 × 103 g m−2 day−1), indicating a fluid-induced change of properties of the underlying clayey sediments. Positive and negative anomalies in the electric self-potential parallel to the ERTs can be found where CO2 degassing occurs which indicates varying ascent or descent of fluids within these spots. Some degassing spots seem not to be actively degassing continuously over time, which can also be observed by other studies in the same area. We suggest that future gas mappings are accompanied by methods that observe the state of fluid systems at subsurface over time, e.g. electric resistivity tomography and self potential. © 2017, Springer-Verlag Berlin Heidelberg.
cited By 6
Keywords: carbon dioxide; carbon flux; degassing; electrical resistivity; fumarole; mantle structure; mapping; temporal variation; tomography; Bohemia; Cheb Basin; Czech Republic; Karlovarsky

Arctic glacial and interglacial variability throughout the quaternary: Evidence from lake Elgygytgyn, northeastern Russia - Melles, M.; Wennrich, V. (Polarforschung, 2017)
Lake Elgygytgyn in the north-eastern Russian Arctic became the target of extensive international site surveys in the late 1990s, with complex geoscientific fieldwork conducted in 1998, 2000, and 2003. The surveys strongly supported the hypothesis that the lake hosts a nearly continuous sediment record, which is highly sensitive to climatic and environmental changes and covers the time since the lake formation by a meteorite impact some 3.6 Ma ago. These promising findings led to deep drilling operations within the scope of the International Continental Scientific Drilling Program (ICDP) in 2008 and 2009, during which 141 m of permafrost deposits in the catchment, the 318 m thick lake sediment succession in the lake centre, and about 200 m of impact rocks underneath were drilled. Palaeoenvironmental and palaeoclimatological research on the Quaternary part of the lake sediment record revealed that full glacial conditions, with mean annual air temperatures at least 3.3 ±0.9 °C lower than today, first commenced at the Pliocene/ Pleistocene boundary 2.6 Ma ago. They gradually increased in frequency from ca. 2.3 to 1.8 Ma, eventually concurring with all global glacials and several stadials. The interglacials at Lake Elgygytgyn significantly differ in intensity. So-called super interglacials irregularly occurred throughout the Quaternary, including Marine Isotope Stages 11.3 and 31, when mean temperatures of the warmest month and annual precipitation were up to 4-5 °C and 300 mm higher than today, respectively. According to climate modelling these climatic settings cannot in all cases be traced back to orbital forcing or greenhouse gas concentrations. They are, at least partly, the result of other processes and feedbacks in the climate system. A remarkable coincidence of the super interglacials with diatomite layers in the Antarctic ANDRILL 1B record suggests that they were associated with considerable retreats of the West Antarctic Ice Sheet. The ice decay may have caused reductions in Antarctic Bottom Water formation, its transport to the Pacific Ocean, and its upwelling in the north-western Pacific, and potentially increased warm-water intrusions through the Bering Strait into the Arctic Ocean. © Alfred Wegener Institut fur Polar- und Meeresforschung. All rights reserved.
cited By 0
Keywords: climate variation; environmental change; glacial-interglacial cycle; lacustrine deposit; paleoclimate; paleoenvironment; paleolimnology; Quaternary; Chukchi; Elgygytgyn Lake; Russian Federation

Deep drilling reveals puzzling history of campi flegrei caldera - Branscombe, Alexandra (Eos (United States), 2017)

A 1251m-thick Deccan flood basalt pile recovered by scientific drilling in the Koyna region, western India - Mishra, S.; Misra, S.; Vyas, D.; Nikalje, D.; Warhade, A.; Roy, S. (Journal of the Geological Society of India, 2017)
A 1251 m thick succession of Deccan lava flows has been recovered by scientific drilling in the Koyna region, western part of the Deccan Volcanic Province (DVP). Forty-six lava flows, starting with the first flow overlying the granitic basement in the region, have been identified through mesoscopic studies of cores obtained from a 1500 m deep borehole KBH7 in Panchgani village of Patan sub-division. Mesoscopic observations supported by petrographic studies bring out the characteristics of the basaltic pile. The salient findings are as follows. The thickness of Deccan trap in the Panchgani area is 1251.20 m, comprising a succession of 40 simple lava flows and 6 compound lava flows. The contact with the underlying granitic basement occurs over a short span of 90 cm. Infra-trappean sediments are absent. Overall, ∼74% of the basaltic pile is constituted of massive basalt and ∼24% vesicular/amygdaloidal basalt. Red bole horizons are observed in 7 flows. Nine giant plagioclase basalt (GPB) flows are identified in the single vertical section. The long basalt core may serve as a model Deccan trap section for correlation with the flows exposed at the surface in the Koyna and surrounding region and support detailed investigations to constrain the duration of Deccan volcanism. © 2017, Geological Society of India.
cited By 16
Keywords: basement rock; Deccan Traps; drilling; flood basalt; lava flow; petrography; plagioclase; volcanism; volcanology; India; Koyna; Maharashtra

Detection of a new sub-lithospheric discontinuity in Central Europe with S-receiver functions - Kind, Rainer; Handy, Mark R.; Yuan, Xiaohui; Meier, Thomas; K{ampf, Horst; Soomro, Riaz (Tectonophysics, 2017)
We used S-receiver functions (i.e. S-to-P converted signals) to study seismic discontinuities in the upper mantle between the Moho and the 410 km discontinuity beneath central Europe. This was done by using c. 49,000 S-receiver functions from c. 700 permanent and temporary broadband stations made available by the open EIDA Archives. Below Phanerozoic Europe we observed expected discontinuities like the Moho, the lithosphere-asthenosphere boundary (LAB), the Lehmann discontinuity and the 410 km discontinuity with an additional overlying low velocity zone. Below the East European Craton (EEC), we observed the Mid-Lithospheric Discontinuity (MLD) at c. 100 km depth as well as the controversial cratonic LAB at c. 200 km depth. At the boundary of the EEC but still below the Phanerozoic surface, we observed downward velocity reductions below the LAB in the following regions: the North German-Polish Plain at about 200 km depth; the Bohemian Massive, north-west dipping from 200 to 300 km depth; the Pannonian Basin, north-east dipping from 150 to 200 km depth underneath the western Carpathians and the EEC. We named this newly observed structure Sub-Lithospheric Discontinuity (SLD). At the northern edge of the Bohemian Massive, we see a sharp vertical step of about 100 km between the SLD below the Bohemian Massive and the North German-Polish Plain. This step follows the surface trace of the Rheic Suture between the continental Saxo-Thuringian and Rheno-Herzynian zones of the Variscan orogen. A preliminary interpretation of these features is that a prong of the cratonic mantle lithosphere penetrated the Phanerozoic asthenosphere during the continental collision at the western and south-western edges of the EEC. © 2017 Elsevier B.V.
Keywords: Bohemian Massif; East European Craton; Pannonian Basin; Laboratories; Bohemian massifs; East-European craton; Lithosphere-asthenosphere boundary; Lithospheric; Pannonian basin; S-receiver functions; asthenosphere; craton; discontinuity; lithosphere; Moho; seismograph; upper mantle; Structural geology

Grain size-dependent strength of phyllosilicate-rich gouges in the shallow crust: Insights from the SAFOD site - Phillips, N.J.; White, J.C. (Journal of Geophysical Research: Solid Earth, 2017)
The San Andreas Fault Observatory at Depth (SAFOD) drilling project directly sampled a transitional (between creeping and locked) segment of the San Andreas Fault at 2.7 km depth. At the site, changes in strain rate occur between periods of coseismic slip ( >10−7 s−1) and interseismic creep (10−10 s−1) over decadal scales ( 30 years). Microstructural observations of core retrieved from the SAFOD site show throughgoing fractures and gouge-rich cores within the fractures, evidence of predominantly brittle deformation mechanisms. Within the gouge-rich cores, strong phases show evidence of deformation by pressure solution once the grain size is reduced to a critical effective grain size. Models of pressure solution-accommodated creep for quartz-phyllosilicate mixtures indicate that viscous weakening of quartz occurs during the interseismic period once a critical effective grain size of 1 μm is achieved, consistent with microstructural observations. This causes pronounced weakening, as the strength of the mixture is then controlled by the frictional properties of the phyllosilicate phases. These results have pronounced implications for the internal deformation of fault zones in the shallow crust, where at low strain rates, deformation is accommodated by both viscous and brittle deformation mechanisms. As strain rates increase, the critical effective grain size for weakening decreases, localizing deformation into the finest-grained gouges until deformation can no longer be accommodated by viscous processes and purely brittle failure occurs. ©2017. American Geophysical Union. All Rights Reserved.
cited By 5
Keywords: brittle deformation; coseismic process; creep; crust; deformation mechanism; fault gouge; grain size; phyllosilicate; pressure; San Andreas Fault; slip; strain rate; strength

Geoelectrical and electromagnetic methods applied to paleolimnological studies: Two examples from desiccated lakes in the Basin of Mexico - B{ucker, M.; Garc'ia, S.L.; Guerrero, B.O.; Caballero, M.; P'erez, L.; Caballero, L.; Paz, C.P.; S'anchez-Galindo, A.; Villegas, F.J.; Orozco, A.F.; Brown, E.; Werne, J.; et al. (Boletin de la Sociedad Geologica Mexicana, 2017)
Paleolimnological studies require a broad understanding of the geometry and depth of the sedimentary fill of lake basins prior to coring campaigns. Seismic methods are routinely employed for the indirect characterization of lake-bottom sediments. However, the use of seismic methods might occasionally be limited due to surface conditions or poor seismic contrasts between the stratigraphic units, which lead to data quality that is too poor to provide sufficient information for the selection of drill sites. Sources of cultural noise are one of the main reasons why seismic methods fail in study areas near or within large cities, such as Mexico City. Under certain conditions, electrical and electromagnetic methods might be a suitable substitute or complement to seismic exploration, as they respond to different physical properties of the subsurface. To evaluate the applicability of such methods, here we present two recent case studies from the desiccated lakes Chalco and Xochimilco both located in urban areas within the Basin of Mexico where electrical resistivity tomography (ERT), transient electromagnetic (TEM) and magnetotelluric (MT) soundings were conducted for the characterization of lake basement and lacustrine sediments. In both examples, the results of the geophysical exploration contributed valuable stratigraphic information for the following drilling and core recovery, which highlights the potential of electrical and electromagnetic methods in paleolimnological studies.
cited By 9

Geology and in situ stress of the MH-2 borehole, Idaho, USA: Insights into western Snake River Plain structure from geothermal exploration drilling - Kessler, J.A.; Bradbury, K.K.; Evans, J.P.; Pulsipher, M.A.; Shervais, J.W.; Rowe, F.E.; Varriale, J. (Lithosphere, 2017)
Project HOTSPOT, the Snake River Scientific Drilling Project (International Continental Scientific Drilling Program), tested for deep geothermal resources and examined the petrology of volcanic rocks with three drillholes in the central and western Snake River Plain (western USA). The MH-2 drillhole targeted fractured crystalline and hydrothermally altered basalt in the area of the Mountain Home Air Force Base (Idaho) to a total depth of 1821 m. At 1745 m depth the drillhole encountered flowing artesian hydrothermal fluids of at least 150 °C. We integrate geological analyses of core, image log, and borehole geophysical data, and in situ stress analyses to describe the structural environment that produces permeability for artesian flow. The rocks in the lower 540 m of the drillhole consist of basalt flows as much as 30 m thick, altered basalt, and thin sedimentary horizons. The mechanical stratigraphy is defined by nine mechanical horizons that are in three ranges of rock strength on the basis of experimentally determined strength data, core logging, and geophysical log signatures. Hydrothermal alteration products and mineralization in the core are associated with three highly faulted sections; the lowermost section is associated with the zone of flowing thermal water. Shear slip indicators on faults observed in core indicate slip ranging from pure strike slip to normal failure mechanisms in the stronger horizons. The borehole breakouts indicate that the maximum horizontal stress, SH, is oriented 047° ± 7°, and drilling-induced tensile fractures indicate that SH is oriented at 67° ± 21°.The in situ stress orientations exhibit little variation over the depth of the measured interval, but the SH magnitude varies with depth, and is best explained by an oblique normal fault stress regime.The geomechanical model indicates that if pore pressures at depth are elevated above the normal hydrostatic gradient, as observed here, the system has the potential to deform by mixed normal and strike-slip failure. Our observations and interpretations suggest that the MH-2 borehole was drilled into oblique normal faults that intersect a buried 300°-trending fault block masked by the basaltic volcanic complex. These data indicate that the transition from the central to western Snake River Plain is characterized by complex structures developed in response to a transitional stress state related to Snake River Plain and western Basin and Range stress regimes. The western Basin and Range stress and tectonic regime may extend from northern Nevada into western Idaho and may enhance the potential for geothermal resources by creating interconnected fracture and fault-related permeability at depth. © 2017 Geological Society of America.
Keywords: Idaho; Snake River Plain; United States; Air; Basalt; Boreholes; Boring; Clay alteration; Core analysis; Faulting; Fracture; Geology; Geophysics; Geothermal fields; Geothermal prospecting; Horizontal drilling; Rivers; Rock drills; Sedimentary rocks; Software testing; Stratigraphy; Stresses; Strike-slip faults; Structural geology; Volcanic rocks; Volcanoes; Well logging; Continental scientific drillings; Drilling-induced tensile fractures; Geothermal exploration; Hydrostatic gradients; Hydrothermal alterations; Mechanical stratigraphy; Sedimentary horizons; Structural environment; artesian well; borehole geophysics; geological survey; geomechanics; geothermal system; hydrothermal activity; hydrothermal fluid; in situ stress; petrology; strike-slip fault; Fault slips

Geophysical techniques of reservoir monitoring for marine gas hydrate exploitation - He, T.; Lu, H.; Lin, J.; Dong, Y.; He, J. (Earth Science Frontiers, 2017)
Marine gas hydrate is an important resource of clean energy for the future, but its exploitation requires not only the innovation of development techniques but also serious consideration of protection of marine environment. For a timely response to production process, monitoring of the dynamic change of gas hydrate reservoir in real time is a basic requirement for a successful exploitation. However, in previous successful gas hydrate production experiments, either in terrestrial permafrost area (Mallik of Canada and Ignik Sikumi of USA) or on continental slope in deep sea (Nankai Trough of Japan), monitoring was carried out mainly through the instruments installed in the two or three observation wells which were only tens of meters away from the production well, and consequently the monitoring might have covered only a limited area. At the present the monitoring technique for large-scale monitoring of gas hydrate reservoir has not been established worldwide, even systematic discussion and scheme design are absent. Based on the acoustic and electrical responses to the saturation change and granular contact mode of gas hydrate layer, several seismic and electromagnetic exploration methods have been compared to see their feasibility and merits and drawbacks for large-scale monitoring of marine gas hydrate development, and an advanced geophysical monitoring scheme is proposed for the upcoming gas hydrate experimental production in South China Sea and future commercial exploitation. The integrated geophysical monitoring system is comprised of (1) a set of geophysical sensors to be installed in the observation wells, which will continuously collect the key physical parameters as temperature, pressure, electrical resistivity, streaming potential, heat flux, etc.; (2) a high sensitive and endurable full fiber 4-component ocean bottom seismic cable system to record the time lapse variations of reservoir acoustic properties of both compressive and shear waves; (3) a net of multifunctional ocean bottom nodes around the production well to measure the seafloor surface deformation/depression during production, and to directly detect and visually observe possible methane leakage. On a well designed protocol, this monitoring system can quantitatively measure the key geophysical variations associated with gas hydrate dissociation, and the data to be acquired will provide scientific basis for production optimization, environment protection and risk assessment for marine gas hydrate exploitation. © 2017, Editorial Office of Earth Science Frontiers. All right reserved.
cited By 13
Keywords: Acoustic properties; Deformation; Earthquake effects; Electromagnetic prospecting; Gas hydrates; Gases; Geophysics; Heat flux; Hydration; Risk assessment; Seismology; Shear flow; Shear waves; Commercial exploitation; Gas-hydrate production; Geophysical monitoring; MCSEM; Production optimization; Reservoir monitoring; Seafloor deformation; Seismic system; Monitoring

Geothermal Play Fairway Analysis of the Snake River plain: Phase 2 - Shervais, J.W.; Glen, J.M.G.; Nielson, D.L.; Garg, S.; Liberty, L.M.; Siler, D.; Dobson, P.; Gasperikova, E.; Sonnenthal, E.; Neupane, G.; Deangelo, J.; Newell, D.L.; et al. (Transactions - Geothermal Resources Council, 2017)
Play Fairway Analysis (PFA) is a methodology adapted from the petroleum industry that integrates data at the regional or basin scale to define favorable plays for exploration in a systematic fashion. Phase 2 of our Play Fairway Analysis of the Western Snake River Plain (WSRP) province in southern Idaho had three primary goals: first, to fill data gaps in critical areas in order to better define potential prospects, second, to integrate these data into new thermal and structural models, and finally, to infer the location of potential resources and drilling targets that could be validated during Phase 3. Prospects in the WSRP identified as potential target resources for Phase 3 validation include the Mountain Home region close to the Air Force Base, and the Camas Prairie. The Mountain Home region represents a blind geothermal resource in an area of high heat flow and young volcanism. The Camas Prairie is a, structurally controlled resource in an area with indicators of magmatic heat. New geophysical data acquired at these sites includes reflection seismic, gravity and magnetic surveys, and a magnetotelluric field survey. New geochemical data collection focused on the Camas Prairie, and included the aqueous and isotope geochemistry of hot springs, cold springs, and wells (geothermal, groundwater, and irrigation). New field mapping, sampling, and basalt flow chronology was also conducted at Camas Prairie. Integrated results from Phase 1 and 2 studies suggest that the system near the Mountain Home Air Force Base is located at ∼1.5-2.3 km depth, and the structurallycontrolled system at Camas Prairie is shallower, with upper reservoir depths perhaps only ∼0.5-0.7 km.
cited By 5
Keywords: Exploratory geochemistry; Geographic information systems; Geothermal fields; Groundwater; Groundwater geochemistry; Hot springs; Landforms; Military aviation; Petroleum industry; Petroleum prospecting; Risk assessment; Rivers; Surveys; Geothermal Play Fairway Analysis; Geothermal resources; Heat sources; Isotope geochemistry; Potential resources; Potential targets; Reflection seismic; Snake river plains; Geothermal springs

Gold mobility during Palaeoarchaean submarine alteration - Hofmann, Axel; Pitcairn, Iain; Wilson, Allan (Earth and Planetary Science Letters, 2017)

GONAF - The borehole geophysical observatory at the North Anatolian Fault in the eastern Sea of Marmara - Bohnhoff, M.; Dresen, G.; Ceken, U.; Kadirioglu, F.T.; Kartal, R.F.; Kilic, T.; Nurlu, M.; Yanik, K.; Acarel, D.; Bulut, F.; Ito, H.; Johnson, W.; et al. (Scientific Drilling, 2017)
The Marmara section of the North Anatolian Fault Zone (NAFZ) runs under water and is located less than 20 km from the 15-million-person population center of Istanbul in its eastern portion. Based on historical seismicity data, recurrence times forecast an impending magnitude M > 7 earthquake for this region. The permanent GONAF (Geophysical Observatory at the North Anatolian Fault) has been installed around this section to help capture the seismic and strain activity preceding, during, and after such an anticipated event. © Author(s) 2017.
cited By 13
Keywords: Earthquakes; Geophysics; Historical seismicity; Istanbul; North Anatolian Fault; North Anatolian Fault Zone; Population centers; Recurrence time; Sea of Marmara; Under water; Observatories

Granite-gneiss basement below Deccan Traps in the Koyna region, western India: Outcome from scientific drilling - Misra, S.; Bartakke, V.; Athavale, G.; Akkiraju, V.V.; Goswami, D.; Roy, S. (Journal of the Geological Society of India, 2017)
The Koyna region, located in the Deccan Flood Basalt Province of western peninsular India has been experiencing reservoir triggered seismicity since the impoundment of the Shivajisagar water reservoir in 1962. Scientific drilling carried out to 1522 m depth in the vicinity of the seismogenic zone exposed the granitic basement that lay below the Deccan Traps and provided a unique opportunity to study the rock types, petrological characteristics and microstructures. Cores obtained from drilling at four sites considered to be representative of the Koyna region, were studied. The boreholes include KBH-1 (Rasati) in the northern part, KBH-5 (Phansavle) in the western part, KBH-6 (Ukhalu) and KBH-7 (Panchgani) in the eastern part of the region. Each borehole penetrates the entire pile of Deccan basalt and pass through a few hundred metres of the granitic basement. The salient results are as follows: (i) The basement granitoids are dominantly composed of granite-gneiss, granite and migmatitic gneiss, typical of cratonic gneiss exposed in peninsular India. (ii) Petrology and microstructure study confirm the occurrence of strained quartz and unstrained plagioclase feldspars in the basement granitoids. (iii) Localized fault zones within the basement section, with prominent evidences of fault breccia, fault gouge, slicken lines with slickensides and pseudotachylite veins are observed in the individual boreholes. (iv) Anastomosing fracture network within these fault zones are good pathways for water channelization, which is supported by the higher abundances of ferruginous and siliceous secondary precipitations following the fractures. © 2017, Geological Society of India.
cited By 22
Keywords: basalt; basement rock; Deccan Traps; drilling; gneiss; granite; microstructure; petrology; seismic zone; India; Koyna; Maharashtra

Geochemical and microstructural evidence for interseismic changes in fault zone permeability and strength, Alpine Fault, New Zealand - Boulton, C.; Menzies, C.D.; Toy, V.G.; Townend, J.; Sutherland, R. (Geochemistry, Geophysics, Geosystems, 2017)
Oblique dextral motion on the central Alpine Fault in the last circa 5 Ma has exhumed garnet-oligoclase facies mylonitic fault rocks from ∼35 km depth. During exhumation, deformation, accompanied by fluid infiltration, has generated complex lithological variations in fault-related rocks retrieved during Deep Fault Drilling Project (DFDP-1) drilling at Gaunt Creek, South Island, New Zealand. Lithological, geochemical, and mineralogical results reveal that the fault comprises a core of highly comminuted cataclasites and fault gouges bounded by a damage zone containing cataclasites, protocataclasites, and fractured mylonites. The fault core-alteration zone extends ∼20 –30 m from the principal slip zone (PSZ) and is characterized by alteration of primary phases to phyllosilicate minerals. Alteration associated with distinct mineral phases occurred proximal the brittle-to-plastic transition (T ≤ 300 –400°C, 6 –10 km depth) and at shallow depths (T = 20 –150°C, 0 –3 km depth). Within the fault core-alteration zone, fractures have been sealed by precipitation of calcite and phyllosilicates. This sealing has decreased fault normal permeability and increased rock mass competency, potentially promoting interseismic strain buildup. © 2016. American Geophysical Union. All Rights Reserved.
cited By 19
Keywords: Geochemistry; Lithology; Mechanical permeability; Microstructure; Mineralogy; Minerals; Sealing (finishing); Silicates; Alpine Faults; alteration; Fault rock; New zealand; seismic cycle; Rocks; chemical alteration; deformation; fault zone; geochemistry; lithology; microstructure; neotectonics; permeability; seismicity; slip rate; strain rate; Alpine Fault Zone; New Zealand; South Island

High resolution core scan facility at BGRL-MoES, Karad, India - Tiwari, S.; Mishra, S.; Srihariprasad, G.; Vyas, D.; Warhade, A.; Nikalje, D.; Bartakke, V.; Mahesh, B.; Tembhurnikar, P.; Roy, S. (Journal of the Geological Society of India, 2017)
A high-resolution, optical core scan laboratory has been set up at Borehole Geophysics Research Laboratory (BGRL), Ministry of Earth Sciences (MoES), Karad. The facility provides a DMT® CoreScan3 optical core scanner and digital drill core data management system for core logging and analysis since July 2016. High resolution images are being produced in 360° mode for detailed unwrapped full circumference of drill core or plane mode for top surface image of slabbed drill core. Planar images of fractured cores and cuttings are also obtained. Image resolution ranges from 5 pix/mm (∼16 megapixel equivalent) to 40 pix/mm (∼1024 megapixel equivalent) for mapping of ultra high resolution data. The scanned core images are combined to create a digital core library. The facility helps in core sample analysis, structural analysis, textural and grain-size analysis, geotechnical studies, and integration with geophysical log data. © 2017, Geological Society of India.
cited By 3
Keywords: core logging; data management; digital image; grain size; image resolution; mapping; pixel; texture; India; Karad; Maharashtra

High-velocity frictional properties of Alpine Fault rocks: Mechanical data, microstructural analysis, and implications for rupture propagation - Boulton, C.; Yao, L.; Faulkner, D.R.; Townend, J.; Toy, V.G.; Sutherland, R.; Ma, S.; Shimamoto, T. (Journal of Structural Geology, 2017)
The Alpine Fault in New Zealand is a major plate-bounding structure that typically slips in ∼M8 earthquakes every c. 330 years. To investigate the near-surface, high-velocity frictional behavior of surface- and borehole-derived Alpine Fault gouges and cataclasites, twenty-one rotary shear experiments were conducted at 1 MPa normal stress and 1 m/s equivalent slip velocity under both room-dry and water-saturated (wet) conditions. In the room-dry experiments, the peak friction coefficient (μp = τp/σn) of Alpine Fault cataclasites and fault gouges was consistently high (mean μp = 0.67 ± 0.07). In the wet experiments, the fault gouge peak friction coefficients were lower (mean μp = 0.20 ± 0.12) than the cataclasite peak friction coefficients (mean μp = 0.64 ± 0.04). All fault rocks exhibited very low steady-state friction coefficients (μss) (room-dry experiments mean μss = 0.16 ± 0.05; wet experiments mean μss = 0.09 ± 0.04). Of all the experiments performed, six experiments conducted on wet smectite-bearing principal slip zone (PSZ) fault gouges yielded the lowest peak friction coefficients (μp = 0.10 –0.20), the lowest steady-state friction coefficients (μss = 0.03 –0.09), and, commonly, the lowest specific fracture energy values (EG = 0.01 –0.69 MJ/m2). Microstructures produced during room-dry and wet experiments on a smectite-bearing PSZ fault gouge were compared with microstructures in the same material recovered from the Deep Fault Drilling Project (DFDP-1) drill cores. The near-absence of localized shear bands with a strong crystallographic preferred orientation in the natural samples most resembles microstructures formed during wet experiments. Mechanical data and microstructural observations suggest that Alpine Fault ruptures propagate preferentially through water-saturated smectite-bearing fault gouges that exhibit low peak and steady-state friction coefficients. © 2017 The Authors
cited By 35
Keywords: Bearings (machine parts); Core drilling; Data flow analysis; Fracture energy; Friction; Infill drilling; Microstructure; Shear bands; Shear flow; Velocity; Alpine Faults; Crystallographic preferred orientations; Friction coefficients; Frictional properties; High-velocity frictions; Micro-structural observations; Microstructural analysis; Rupture propagation; Fault slips; fault; microstructure; rock mechanics; rupture; shear band; Alpine Fault Zone; New Zealand; South Island

How to choose a right drilling site for the ICDP Cretaceous Continental Scientific Drilling in the Songliao Basin (SK2), Northeast China - Wang, P.; Liu, H.; Ren, Y.; Wan, X.; Wang, S.; Qu, X.; Meng, Q.; Huang, Y.; Huang, Q.; Gao, Y.; Wang, C. (Earth Science Frontiers, 2017)
The Continental Scientific Drilling in the Songliao Basin has been done since 2005, which include the SK1, having finished in 2007, and the SK2 that started drilling in 2014 and is expected to finish in 2017. The purposes of the project are as followings, to drilling through the whole Cretaceous sequence of the Songliao Basin, to obtain continuous high resolution continental geological records by the means of the so-called “2 wells 4 holes drilling procedures”, to research the Cretaceous greenhouse climate changes in order to be better prepared with the challenge caused by the nowadays global warming event. According to the goals above we proposed the rules for the site selection of the SK2 as follows. Firstly, stratigraphic sedimentary records should be continuous. Secondly, sedimentary rocks are preferred, especially the lacustrine fine clastic rocks. Thirdly, thickness of the overburden cap rocks should be as thin as possible. Fourthly, faults should be avoided of. At last, ground conditions should be as good as possible such as roads, electric power, water supply, and so forth. We finally chose the site of SK2 in the Songzhan area where the lacustrine mudstone is well developed in the Xujiaweizi faulted depression of the Songliao Basin. The major target drilling succession is the Lower Cretaceous, namely, Yingcheng, Shahezi, and Huoshiling Formations. The strata under drilling are interbedding sequence of sandstone, siltstone, mudstone and coal, which are intercalated with volcanic rocks and pyroclastic rocks. They are mainly dark rocks of lacustrine facies which reflect the reduced environment. We shall drill through the top boundary (T4) and bottom boundary (T5) of rift fill successions, the boundary between the Upper and Lower Cretaceous, the boundary between Cretaceous and Jurassic (K/J). All these boundaries indicate important geological events which reflect changes of regional tectonics and basin filling styles. With the continuous coring section, we can also obtain some other important geological records with global meanings such as the Cretaceous normal polarity superchron (CNS) and oceanic anoxic event (OAE-1). © 2017, Editorial Office of Earth Science Frontiers. All right reserved.
cited By 24
Keywords: Climate change; Geology; Global warming; Greenhouses; Rocks; Sedimentology; Site selection; Stratigraphy; Tectonics; Volcanic rocks; Water supply; Continental scientific drillings; Greenhouse climates; Oceanic Anoxic Event; Regional tectonics; Sedimentary records; Sedimentary sequence; Songliao basin; Tithonian to Albian; Sedimentary rocks

Iceland drilling project aims to unearth how islands form - Witze, A. (Nature, 2017)
cited By 1
Keywords: hot water; mineral; sea water; biosphere; drilling fluid; microbial community; microorganism; pristine environment; project assessment; sea level change; seafloor; seawater; volcanic eruption; volcanic island; volcanic rock; biosphere; biotechnology; contamination; drill; Iceland; island (geological); nuclear waste; organismal interaction; priority journal; rock; sea level; seashore; Short Survey; volcano; animal; bird; ecosystem; history; microbiology; microflora; physiology; plant; sediment; Atlantic Ocean; Atlantic Ocean (North); Heimaey; Iceland; New Zealand; North Island; Surtsey; Taupo; Waikato; Animals; Birds; Ecosystem; Geologic Sediments; History; 20th Century; History; 21st Century; Iceland; Islands; Microbiota; Plants; Volcanic Eruptions

Image log analysis of in situ stress orientation, breakout growth, and natural geologic structures to 2.5 km depth in central Scandinavian Caledonides: Results from the COSC-1 borehole - Wenning, Quinn C.; Berthet, Th'eo; Ask, Maria; Zappone, Alba; Rosberg, Jan-Erik; Almqvist, Bjarne S. G. (Journal of Geophysical Research: Solid Earth, 2017)
Stress-induced borehole deformation analysis in the Collisional Orogeny in the Scandinavian Caledonide deep scientific borehole establishes in situ stress orientation in a poorly characterized region in central Sweden. Two acoustic televiewer logging campaigns, with more than 1 year between campaigns, provide detailed images along the full length of the 2.5 km deep borehole for breakout, drilling-induced tensile fracture (DITF), and natural occurring structural analysis. Borehole breakouts occur in 13 distinct zones along total length of 22 m, indicating an average maximum horizontal stress, SHmax, orientation of 127° ± 12°. Infrequent DITFs are constrained within one zone from 786 to 787 m depth (SHmax orientation: 121° ± 07°). These SHmax orientations are in agreement with the general trend in Scandinavia and are in accordance with many mechanisms that generate crustal stress (e.g., ridge push, topographic loading, and mantel driven stresses). The unique acquisition of image logs in two successions allows for analysis of time-dependent borehole deformation, indicating that six breakout zones have crept, both along the borehole axis and radially around the borehole. Strong dynamic moduli measured on core samples and an inferred weak in situ stress anisotropy inhibit the formation of breakouts and DITFs. Natural fracture orientation below 800 m is congruent to extensional or hybrid brittle shear failure along the same trend as the current SHmax. Analysis of foliation in the image logs reinforces the interpretation that the discontinuous seismic reflectors with fluctuating dip observed in seismic profiles are due to recumbent folding and boudinage.
_eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2016JB013776
Keywords: breakout growth; elastic properties; foliation and fracture; in situ stress; time dependency

Detrital zircon geochronology of sandstones of the 3.6-3.2 Ga Barberton greenstone belt: No evidence for older continental crust - Drabon, Nadja; Lowe, Donald R.; Byerly, Gary R.; Harrington, Jacob A. (Geology, 2017)

Geochemical evidence of an extraterrestrial component in impact melt breccia from the Paleoproterozoic Dhala impact structure, India - Pati, J.K.; Qu, W.J.; Koeberl, C.; Reimold, W.U.; Chakarvorty, M.; Schmitt, R.T. (Meteoritics and Planetary Science, 2017)
The Paleoproterozoic Dhala structure with an estimated diameter of 11 km is a confirmed complex impact structure located in the central Indian state of Madhya Pradesh in predominantly granitic basement (2.65 Ga), in the northwestern part of the Archean Bundelkhand craton. The target lithology is granitic in composition but includes a variety of meta-supracrustal rock types. The impactites and target rocks are overlain by 1.7 Ga sediments of the Dhala Group and the Vindhyan Supergroup. The area was cored in more than 70 locations and the subsurface lithology shows pseudotachylitic breccia, impact melt breccia, suevite, lithic breccias, and postimpact sediments. Despite extensive erosion, the Dhala structure is well preserved and displays nearly all the diagnostic microscopic shock metamorphic features. This study is aimed at identifying the presence of an impactor component in impact melt rock by analyzing the siderophile element concentrations and rhenium-osmium isotopic compositions of four samples of impactites (three melt breccias and one lithic breccia) and two samples of target rock (a biotite granite and a mafic intrusive rock). The impact melt breccias are of granitic composition. In some samples, the siderophile elements and HREE enrichment observed are comparable to the target rock abundances. The Cr versus Ir concentrations indicate the probable admixture of approximately 0.3 wt.% of an extraterrestrial component to the impact melt breccia. The Re and Os abundances and the 187Os/188Os ratio of 0.133 of one melt breccia specimen confirm the presence of an extraterrestrial component, although the impactor type characterization still remains inconclusive. © The Meteoritical Society, 2017.
cited By 15

Hydrological and temperature change in Arctic Siberia during the intensification of Northern Hemisphere Glaciation - Keisling, B.A.; Castañeda, I.S.; Brigham-Grette, J. (Earth and Planetary Science Letters, 2017)
The Pliocene epoch represents an analog for future climate, with atmospheric carbon dioxide concentrations and continental configurations similar to present. Although the presence of multiple positive feedbacks in polar regions leads to amplified climatic changes, conditions in the Pliocene terrestrial Arctic are poorly characterized. High latitude sedimentary records indicate that dramatic glacial advance and decay occurred in the Pliocene Arctic, with attendant effects on global sea-level. Understanding these deposits and their implications for Earth's future requires developing a sense of climatic evolution across the Pliocene –Pleistocene transition and during the intensification of Northern Hemisphere Glaciation (iNHG) ∼2.7 million yr ago (Ma). Here we reconstruct Arctic terrestrial environmental change from 2.82 –2.41 Ma (Marine Isotope Stages (MIS) G10 –95) using the distribution of branched glycerol dialkyl glycerol tetraethers (brGDGTs) and the isotopic composition of plant leaf waxes (δDwax) in a sedimentary archive from Lake El'gygytgyn, Northeast Russia. Our records reveal changes in proxy behavior across this interval that we attribute to changing boundary conditions, including sea level, sea ice, vegetation and pCO2 during different MISs. We find that brGDGT temperatures and δDwax are decoupled for most of the record, although both show an increasing range of glacial –interglacial variability following iNHG. δDwax is stable from MIS G10 –G4 despite changes in vegetation and temperature, suggesting different sources or pathways for moisture to Lake El'gygytgyn during the Late Pliocene. © 2016 Elsevier B.V.
cited By 13
Keywords: Atmospheric chemistry; Carbon dioxide; Climate change; Glycerol; Isotopes; Lakes; Paraffins; Sea ice; Sea level; Sedimentology; Vegetation; arctic; branched GDGT; Hydrogen isotope; Northern hemisphere glaciations; Palaeoclimate; Pliocene; Glacial geology; alkane; glaciation; hydrogen isotope; hydrological change; Northern Hemisphere; paleoclimate; Pliocene; temperature; Arctic; Chukchi; Elgygytgyn Lake; Russian Federation; Siberia

Fracturing, fluid-rock interaction and mineralisation during the seismic cycle along the Alpine Fault - Williams, J.N.; Toy, V.G.; Smith, S.A.F.; Boulton, C. (Journal of Structural Geology, 2017)
The Alpine Fault has a <50 m wide geochemically distinct hanging-wall alteration zone. Using a combination of petrological and cathodoluminescence (CL) microscopy, Energy Dispersive Spectroscopy and X-ray diffraction, we document the habitat and mineralising phases of macro- and micro-fractures within the alteration zone using samples derived from outcrop and the Deep Fault Drilling Project. Veins predominantly contain calcite, chlorite, K-feldspar or muscovite. Gouge-filled fractures are also observed and reflect filling from mechanical wear and chlorite mineralisation. CL imaging suggests that each calcite vein was opened and sealed in one episode, possibly corresponding to a single seismic cycle. The thermal stability of mineralising phases and their mutually cross-cutting relationships indicates a cyclic history of fracture opening and mineralisation that extends throughout the seismogenic zone. Cataclasites contain intragranular veins that are hosted within quartzofeldspathic clasts, as well as veins that cross-cut clasts and the surrounding matrix. Intragranular calcite veins formed prior to or during cataclasis. Cross-cutting veins are interpreted to have formed by fracturing of relatively indurated cataclasites after near-surface slip localisation within the Alpine Fault's principal slip zone gouges (PSZs). These observations clearly demonstrate that shear strain is most localised in the shallowest part of the seismogenic zone. © 2017 Elsevier Ltd
cited By 20
Keywords: Calcite; Earthquakes; Energy dispersive spectroscopy; Fracture; Mica; Seismographs; Seismology; Shear strain; Thermodynamic stability; X ray diffraction; Alpine Faults; Alteration zones; Drilling projects; Fault structure; Fluid-rock interaction; Mineralisation; Seismogenic zones; Surrounding matrix; Mineralogy; cataclasite; fault zone; fracture; mineralization; seismic method; shear strain; slip; Alpine Fault Zone; New Zealand; South Island

Erosion of Archean continents: The Sm-Nd and Lu-Hf isotopic record of Barberton sedimentary rocks - Garçon, M.; Carlson, R.W.; Shirey, S.B.; Arndt, N.T.; Horan, M.F.; Mock, T.D. (Geochimica et Cosmochimica Acta, 2017)
Knowing the composition, nature and amount of crust at the surface of the early Earth is crucial to understanding the early geodynamics of our planet. Yet our knowledge of the Hadean-Archean crust is far from complete, limited by the poor preservation of Archean terranes, and the fact that less attention has been paid to the sedimentary record that tracks erosion of these ancient remnants. To address this problem and get a more comprehensive view of what an Archean continent may have looked like, we investigated the trace element and Sm-Nd, Lu-Hf isotopic records of Archean metasedimentary rocks from South Africa. We focused our study on sandstone and mudstone from drill core in the Fig Tree Group (3.23 –3.26 Ga) of the Barberton granite-greenstone belt, but also analyzed the 3.4 Ga Buck Reef cherts and still older (3.5 –3.6 Ga) meta-igneous rocks from the Ancient Gneiss Complex, Swaziland. Based on principal component analysis of major and trace element data, the Fig Tree metasedimentary rocks can be classified into three groups: crustal detritus-rich sediments, Si-rich sediments and Ca-, Fe-rich sediments. The detritus-rich sediments have preserved the Sm-Nd and Lu-Hf isotopic signatures of their continental sources, and hence can be used to constrain the composition of crust eroded in the Barberton area in the Paleoarchean period. Based on Sm/Nd ratios, we estimate that this crust was more mafic than today, with an average SiO2 content of 60.5 ± 2 wt.%. This composition is further supported by isotopic mixing calculations suggesting that the sedimentary source area contained equal proportions of mafic-ultramafic and felsic rocks. This implies that the Archean crust exposed to weathering was more mafic than today but does not exclude a more felsic composition at depth. Neodymium and Hf crustal residence ages show that the eroded crust was, on average, ∼300 –400 Ma older than the deposition age of the sediments, which highlights the importance of intracrustal reworking of older crust at ∼3.2 Ga in the Barberton area. The Si-rich sediments have slightly positive εNd (t=3.23Ga) but extremely radiogenic εHf (t=3.23Ga), up to +11. Based on analyses of 3.4 Ga Buck Reef cherts, we suggest that the radiogenic Hf isotopic signature of the Si-rich sediments can be accounted for by the old chert clasts or detrital silicified rock fragments present in the rocks. The latter have extremely high Lu/Hf ratios such that their εHf values would increase dramatically, by about +100 epsilon units every 100 Ma. In the Ca-, Fe-rich sediments, one sample contains carbonate that preserves the typical rare-earth element features of seawater precipitates. The initial Nd isotopic composition of this sample (εNd (t=3.23Ga) = +1.7) is within the range of previous estimates for Archean anoxic seawater. © 2017 Elsevier Ltd
Keywords: South Africa; Ficus (angiosperm); Archean; chert; continental crust; erosion; hafnium; lutetium; mudstone; neodymium isotope; samarium; sandstone; sedimentary rock

Flowing fluid electrical conductivity logging of a deep borehole during and following drilling: estimation of transmissivity, water salinity and hydraulic head of conductive zones; [Diagraphie de la conductivit'e 'electrique des fluides d’un forage profond au cours et après la foration: estimation de la transmissivit'e, de la salinit'e de l’eau et de la charge hydraulique des zones conductrices]; [Condutividade el'etrica em fluido registrada em poço profundo durante e ap'os a perfuração: estimativa da transmissividade, salinidade da 'agua e carga hidr'aulica de zonas condutivas]; [Registro de conductividad el'ectrica en el flujo del fluido de un pozo profundo durante y despu'es de la perforaci'on: estimaci'on de trasmisividad, salinidad del agua y carga hidr'aulica de las zonas conductivas] - Doughty, Christine; Tsang, Chin-Fu; Rosberg, Jan-Erik; Juhlin, Christopher; Dobson, Patrick F.; Birkholzer, Jens T. (Hydrogeology Journal, 2017)

Drilling into seismogenic zones of M2.0 – M5.5 earthquakes from deep South African gold mines (DSeis): establishment of research sites - Ogasawara, H.; Durrheim, R.J.; Yabe, Y.; Ito, T.; Aswegen, G.; Grobbelaar, M.; Funato, A.; Ishida, A.; Mngadi, S.; Manzi, M.S.D.; Ziegler, M.; Ward, A.K.; et al. (ISRM AfriRock - Rock Mechanics for Africa, 2017)
While mining-induced earthquakes in the deep gold mines of South Africa pose a risk to mines, mineworkers, and the public, they also provide an unusual opportunity to study the physics of earthquakes. The source zone of a M5.5 earthquake that occurred near Orkney, South Africa on 5 August 2014 was well-defined by tens of thousands of aftershocks recorded by instruments deployed as part of a Japanese - South African research project. The upper edge of the M5.5 rupture is located several hundred metres below the mining horizon. A proposal to drill into the M5.5 source zone, as well as several other active faults in other deep mines, was approved by the International Continental scientific Drilling Programme (ICDP) in August 2016. Here we describe the scope and objectives of the project, and the selection and preparation of the principal drilling sites. In addition to the studies of earthquake phenomena, some of the holes will be used by geomicrobiologists to investigate deep microbiological activity fuelled by hydrogen released by seismic rupture to address questions about early life on planet Earth. © 2017 International Society for Rock Mechanics. All Rights Reserved.
Keywords: Earth (planet); Earthquakes; Economic geology; Faulting; Gold mines; Rock mechanics; Active fault; African gold mine; Continental scientific drillings; Deep gold mines; Deep-mines; Drilling projects; Microbiological activity; Seismogenic zones; Source zone; South Africa; Infill drilling

Drilling into an active mofette: Pilot-hole study of the impact of CO2-rich mantle-derived fluids on the geo-bio interaction in the western Eger Rift (Czech Republic) - Bussert, R.; K{ampf, H.; Flechsig, C.; Hesse, K.; Nickschick, T.; Liu, Q.; Umlauft, J.; Vylita, T.; Wagner, D.; Wonik, T.; Flores, H.E.; Alawi, M. (Scientific Drilling, 2017)
Microbial life in the continental deep biosphere is closely linked to geodynamic processes, yet this interaction is poorly studied. The Cheb Basin in the western Eger Rift (Czech Republic) is an ideal place for such a study because it displays almost permanent seismic activity along active faults with earthquake swarms up to ML 4.5 and intense degassing of mantle-derived CO2 in conduits that show up at the surface in form of mofettes. We hypothesize that microbial life is significantly accelerated in active fault zones and in CO2 conduits, due to increased fluid and substrate flow. To test this hypothesis, pilot hole HJB-1 was drilled in spring 2016 at the major mofette of the Hartoušov mofette field, after extensive pre-drill surveys to optimize the well location. After drilling through a thin caprock-like structure at 78.5 m, a CO2 blowout occurred indicating a CO2 reservoir in the underlying sandy clay. A pumping test revealed the presence of mineral water dominated by Na+, Ca2+, HCO3-, SO42- (Na-Ca-HCO3-SO4 type) having a temperature of 18.6 °C and a conductivity of 6760 μScm-1. The high content of sulfate (1470 mg L-1) is typical of Carlsbad Spa mineral waters. The hole penetrated about 90 m of Cenozoic sediments and reached a final depth of 108.50m in Palaeozoic schists. Core recovery was about 85 %. The cored sediments are mudstones with minor carbonates, sandstones and lignite coals that were deposited in a lacustrine environment. Deformation structures and alteration features are abundant in the core. Ongoing studies will show if they result from the flow of CO2-rich fluids or not. © Author(s) 2017.
cited By 16
Keywords: Beverages; Calcium; Carbon dioxide; Drilling fluids; Earthquakes; Faulting; Geodynamics; Reservoirs (water); Sodium; Sodium compounds; Sulfur compounds; Water; Cenozoic sediments; Czech Republic; Deformation structure; Earthquake swarms; Geodynamic process; Microbial life; Seismic activity; Well location; Calcium compounds

Effect of an 860-m thick, cold, freshwater aquifer on geothermal potential along the axis of the eastern Snake River Plain, Idaho - Lachmar, T.E.; Freeman, T.G.; Sant, C.J.; Walker, J.R.; Batir, J.F.; Shervais, J.W.; Evans, J.P.; Nielson, D.L.; Blackwell, D.D. (Geothermal Energy, 2017)
A 1912-m exploration corehole was drilled along the axis of the eastern Snake River Plain, Idaho. Two temperature logs run on the corehole display an obvious inflection point at about 960 m. Such behavior is indicative of downward fluid flow in the wellbore. The geothermal gradient above 935 m is 4.5 °C/km, while the gradient is 72 –75 °C/km from 980 to 1440 m. Projecting the higher gradients upward to where they intersect the lower gradient on the temperature logs places the bottom of the cold, freshwater Snake River Plain aquifer, which suppresses the geothermal gradient at this location, at least 860 m below the surface. The average heat flow for the corehole between 983 and 1550 m is 132 mW/m2. Although the maximum bottom-hole temperature extrapolated from a measured time –temperature curve was only 59.3 °C, geothermometers suggest an equilibrium temperature on the order of 125 –140 °C based on a single fluid sample from 1070 m. Furthermore, below 960 m the basalt core shows obvious signs of alteration, including a distinct color change, the formation of smectite clay, and the presence of secondary minerals filling vesicles and fracture zones. This alteration boundary could act as an effective cap or seal for a hot-water geothermal system. © 2017, The Author(s).
cited By 5
Keywords: Aquifers; Basalt; Clay alteration; Flow of fluids; Geothermal fields; Geothermal logging; Rivers; Water; X ray diffraction; Bottom hole temperatures; Corehole; Equilibrium temperatures; Freshwater aquifer; Geothermal gradients; Geothermal potential; Geothermometers; Temperature log; Thermal logging; aquifer; basalt; geothermal system; geothermometry; heat flow; temperature gradient; thermal alteration; X-ray diffraction; Idaho; Snake River Plain; United States; Calluna vulgaris

Effect of graphene and graphene oxide addition on lubricating and friction properties of drilling fluids - Liu, S.Q.; Chen, Z.R.; Meng, Q.N.; Zhou, H.L.; Li, C.; Liu, B.C. (Nanoscience and Nanotechnology Letters, 2017)
This study has examined the potential improvement of the lubricating properties of drilling fluid by adding graphene and graphene oxide (GO). The effects of different concentrations of graphene and GO addition on lubricating properties and friction reduction of drilling fluid have been studied by using an extreme pressure lubrication device and a pin-on-disk tester. In pin-on-disk tests, the pin material was AISI316 steel (casing material) and the disk material was 7075 aluminum alloy (drill pipe material). The pin-on-disk friction and wear tests were carried out under the condition that the pin and disk are immerged in drilling fluid. Results indicated that the lubricating properties of drilling fluid significantly improved by adding appropriate amount of GO materials, while, on the other hand, addition of graphene had limited effect on the lubricating properties of drilling fluid. The lubricating factor of drilling fluid dropped 12.6% by an addition of 0.075 wt% GO. The coefficient of friction between the friction pairs dropped 19.8% by an addition of 0.075 wt% GO. Moreover, the wear volume (WV) of aluminum alloy disc decreased to the minimum value of 0.32 mm3 by an addition of 0.075 wt% GO. On the basis of experimental results, 0.075 wt% GO was added to the oil-based drilling fluids used in an SK-II well, a scientific continental drilling project in the Cretaceous Songliao Basin of Northeast China. Results showed that the lubricating factor of the drilling fluid was reduced by 15.6%, the friction coefficient reduction rate was increased by 24.3% and the aluminum disc wear volume decreased by 20.5%. © 2017 American Scientific Publishers All rights reserved.
cited By 18

Effects of shock pressure and temperature on titanomagnetite from ICDP cores and target rocks of the El’gygytgyn impact structure, Russia - Kontny, A.; Grothaus, L. (Studia Geophysica et Geodaetica, 2017)
The aim of this study was to investigate the effect of meteorite impacts on magnetic properties including magnetic susceptibility and the Verwey transition of Ti-poor titanomagnetite of volcanic rocks from the 3.6 Ma old El’gygytgyn impact structure located in the Okhotsk-Chukotka volcanic belt in north-eastern Russia. The target rocks consist mainly of rhyolite with some andesites, and is a rare example of impact structures within volcanic target rocks on Earth. 27 samples from outside the crater, the crater rim and from the depth interval 316 to 517 m below lake bottom (mblb) of the El’gygytgyn ICDP drilling were studied. A significant decrease of the average specific magnetic susceptibility by around 90% was observed between felsic volcanic rocks from the surface (18.1 × 10-6 m3/kg) and the drill cores from near the crater central uplift (1.9 × 10-6 m3/kg). Ferrimagnetic Fe-Ti oxide assemblages (Verwey transition temperature, TV: -161 to -150°C, Curie temperature, TC: 451 to 581°C), occurring in all studied samples, differ significantly. At the surface titanomaghemite is ubiquitously associated with titanomagnetite. The drill cores lack titanomaghemite, but either show a transformation into titanomagnetite and ilmenite or a strong fragmentation associated with a second TV between -172 and -188°C. Reversible curves of temperature dependence of magnetic susceptibility in the suevite indicate high depositional temperatures of at least 500°C. In the polymict and monomict impact breccia mechanical deformation of titanomagnetite and temperatures of at least 200-350°C related to the shock are suggested from temperature dependent magnetic susceptibility cycling. Lowtemperature oxidation along strongly brecciated grain surfaces in titanomagnetite is suggested to cause the lower TV and we suggest that this phenomenon is related to postimpact hydrothermal activity. The strong magnetic susceptibility decrease at El’gygytgyn is mainly influenced by shock, and post-impact hydrothermalism causes a significant additional depletion. These observations explain why magnetic lows are a ubiquitous phenomenon over impact structures. © 2017, Institute of Geophysics of the ASCR, v.v.i.
cited By 13
Keywords: impact structure; magnetic susceptibility; meteorite; oxidation; pressure effect; temperature effect; titanomagnetite; volcanic rock; Okhotsk-Chukotka Volcanic Belt; Russian Federation

Earthquake-enhanced permeability – evidence from carbon dioxide release following the ML 3.5 earthquake in West Bohemia - Fischer, T.; Matyska, C.; Heinicke, J. (Earth and Planetary Science Letters, 2017)
The West Bohemia/Vogtland region is characterized by earthquake swarm activity and degassing of CO2 of mantle origin. A fast increase of CO2 flow rate was observed 4 days after a ML 3.5 earthquake in May 2014 in the Hartoušov mofette, 9 km from the epicentres. During the subsequent 150 days the flow reached sixfold of the original level, and has been slowly decaying until present. Similar behavior was observed during and after the swarm in 2008 pointing to a fault-valve mechanism in long-term. Here, we present the results of simulation of gas flow in a two dimensional model of Earth's crust composed of a sealing layer at the hypocentre depth which is penetrated by the earthquake fault and releases fluid from a relatively low-permeability lower crust. This simple model is capable of explaining the observations, including the short travel time of the flow pulse from 8 km depth to the surface, long-term flow increase and its subsequent slow decay. Our model is consistent with other analyse of the 2014 aftershocks which attributes their anomalous character to exponentially decreasing external fluid force. Our observations and model hence track the fluid pressure pulse from depth where it was responsible for aftershocks triggering to the surface where a significant long-term increase of CO2 flow started 4 days later. © 2016 Elsevier B.V.
Keywords: Bohemia; Czech Republic; Germany; Vogtland; Carbon dioxide; Faulting; Flow of gases; Structural geology; crustal CO2; Earthquake fault; Earthquake swarms; Enhanced permeability; Fault-valve; Fluid pressure pulse; Low permeability; Two dimensional model; carbon dioxide; degassing; earthquake epicenter; earthquake magnitude; earthquake mechanism; earthquake swarm; lower crust; permeability; trigger mechanism; Earthquakes

Erratum to: Bedrock geology of DFDP-2B, central Alpine Fault, New Zealand (New Zealand Journal of Geology and Geophysics, (2017), 60, 4, (497-518), 10.1080/00288306.2017.1375533) (New Zealand Journal of Geology and Geophysics, 2017)
When this paper was first published online the secondary affiliation for the author Virginia Gail Toy was omitted. The affiliation should have read: Hokkaido University - Earth and Planetary System Science, Department of Natural History Sciences, Graduate School of Sciences, Sapporo, Japan The supplemental data for this paper is also available at http://doi.org/10.5880/ICDP.5052.003. Taylor and Francis apologizes for these errors. © 2017 The Royal Society of New Zealand.
cited By 0

Fifteen years of the Chinese continental scientific drilling program - Xu, Z.; Yang, J.; Wang, C.; An, Z.; Li, H.; Wang, Q.; Su, D. (Scientific Drilling, 2017)
Continental scientific drilling can be regarded as a telescope into the Earth's interior because it provides process insight and uncompromised samples of rocks, fluids, and even sampled from the deep biosphere from the Earth's surface to great depths. As one of the three founding members of the International Continental Scientific Drilling Program (ICDP), ICDP China has made great achievements in many scientific drilling-related research fields. Based on the ICDP participation it attracted global attention of scientists and set up not only the Chinese Continental Scientific Drilling (CCSD) Program in 2001 but also a growing number of ambitious drilling projects in the country. The 5158m deep borehole of the CCSD project at Donghai County in the Sulu ultrahigh-pressure metamorphic terrain demonstrates that large amounts of crustal rocks of the South China Block have been subducted to at least 120 km, followed by rapid uplift. After successful completion of drilling at Donghai, several continental scientific drilling projects were conducted with funding of the Chinese government and partially with support of ICDP, resulting in a total drilling depth of more than 35 000 m. These projects encompass the Continental Environmental Scientific Drilling Program of China, the Scientific Drilling Project of Wenchuan Earthquake Fault Zone, the Continental Scientific Drilling Project of Cretaceous Songliao Basin, and the Program of Selected Continental Scientific Drilling and Experiments. On the occasion of the 20th anniversary of the ICDP and the 15th anniversary of the CCSD Program, this paper reviews the history and major progress of the CCSD Program. © Author(s) 2017.
cited By 2
Keywords: Earthquakes; Metamorphic rocks; Chinese Government; Continental scientific drillings; Drilling projects; Earth' s interior; Scientific drilling; South China block; Ultrahigh-pressure metamorphic; Wenchuan Earthquake; Drilling fluids

Extreme hydrothermal conditions at an active plate-bounding fault - Sutherland, R.; Townend, J.; Toy, V.; Upton, P.; Coussens, J.; Allen, M.; Baratin, L.-M.; Barth, N.; Becroft, L.; Boese, C.; Boles, A.; Boulton, C.; et al. (Nature, 2017)
Temperature and fluid pressure conditions control rock deformation and mineralization on geological faults, and hence the distribution of earthquakes. Typical intraplate continental crust has hydrostatic fluid pressure and a near-surface thermal gradient of 31 ± 15 degrees Celsius per kilometre. At temperatures above 300-450 degrees Celsius, usually found at depths greater than 10-15 kilometres, the intra-crystalline plasticity of quartz and feldspar relieves stress by aseismic creep and earthquakes are infrequent. Hydrothermal conditions control the stability of mineral phases and hence frictional-mechanical processes associated with earthquake rupture cycles, but there are few temperature and fluid pressure data from active plate-bounding faults. Here we report results from a borehole drilled into the upper part of the Alpine Fault, which is late in its cycle of stress accumulation and expected to rupture in a magnitude 8 earthquake in the coming decades. The borehole (depth 893 metres) revealed a pore fluid pressure gradient exceeding 9 ± 1 per cent above hydrostatic levels and an average geothermal gradient of 125 ± 55 degrees Celsius per kilometre within the hanging wall of the fault. These extreme hydrothermal conditions result from rapid fault movement, which transports rock and heat from depth, and topographically driven fluid movement that concentrates heat into valleys. Shear heating may occur within the fault but is not required to explain our observations. Our data and models show that highly anomalous fluid pressure and temperature gradients in the upper part of the seismogenic zone can be created by positive feedbacks between processes of fault slip, rock fracturing and alteration, and landscape development at plate-bounding faults. © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.
cited By 75
Keywords: active fault; deformation; earthquake magnitude; earthquake rupture; fluid dynamics; heating; hydrostatic pressure; hydrothermal activity; hydrothermal system; movement; plate boundary; pressure effect; seismic zone; temperature effect; temperature gradient; topography; Article; earthquake; environmental temperature; heat; heating; hydrostatic pressure; pressure gradient; priority journal; rock; shear stress; topography

Extreme hydrothermal conditions at an active plate-bounding fault - Upton, P.; Coussens, J.; Allen, M.; Baratin, L.-M.; Barth, N.; Becroft, L.; Boles, A.; Broderick, N.G.R.; Janku-Capova, L.; Carpenter, B.M.; C'el'erier, B.; Cooper, A.; et al. (Nature, 2017)
Temperature and fluid pressure conditions control rock deformation and mineralization on geological faults, and hence the distribution of earthquakes. Typical intraplate continental crust has hydrostatic fluid pressure and a near-surface thermal gradient of 31 ± 15 degrees Celsius per kilometre. At temperatures above 300-450 degrees Celsius, usually found at depths greater than 10-15 kilometres, the intra-crystalline plasticity of quartz and feldspar relieves stress by aseismic creep and earthquakes are infrequent. Hydrothermal conditions control the stability of mineral phases and hence frictional-mechanical processes associated with earthquake rupture cycles, but there are few temperature and fluid pressure data from active plate-bounding faults. Here we report results from a borehole drilled into the upper part of the Alpine Fault, which is late in its cycle of stress accumulation and expected to rupture in a magnitude 8 earthquake in the coming decades. The borehole (depth 893 metres) revealed a pore fluid pressure gradient exceeding 9 ± 1 per cent above hydrostatic levels and an average geothermal gradient of 125 ± 55 degrees Celsius per kilometre within the hanging wall of the fault. These extreme hydrothermal conditions result from rapid fault movement, which transports rock and heat from depth, and topographically driven fluid movement that concentrates heat into valleys. Shear heating may occur within the fault but is not required to explain our observations. Our data and models show that highly anomalous fluid pressure and temperature gradients in the upper part of the seismogenic zone can be created by positive feedbacks between processes of fault slip, rock fracturing and alteration, and landscape development at plate-bounding faults. © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.
cited By 75
Keywords: active fault; deformation; earthquake magnitude; earthquake rupture; fluid dynamics; heating; hydrostatic pressure; hydrothermal activity; hydrothermal system; movement; plate boundary; pressure effect; seismic zone; temperature effect; temperature gradient; topography; Article; earthquake; environmental temperature; heat; heating; hydrostatic pressure; pressure gradient; priority journal; rock; shear stress; topography

Feldspar 40Ar/39Ar dating of ICDP PALEOVAN cores - Engelhardt, J.F.; Sudo, M.; Stockhecke, M.; Oberh{ansli, R. (Geochimica et Cosmochimica Acta, 2017)
Volcaniclastic fall deposits in ICDP drilling cores from Lake Van, Turkey, contain sodium-rich sanidine and calcium-rich anorthoclase, which both comprise a variety of textural zoning and inclusions. An age model records the lake's history and is based on climate-stratigraphic correlations, tephrostratigraphy, paleomagnetics, and earlier 40Ar/39Ar analyses (Stockhecke et al., 2014b). Results from total fusion and stepwise heating 40Ar/39Ar analyses presented in this study allow for the comparison of radiometric constraints from texturally diversified feldspar and the multi-proxy lacustrine age model and vice versa. This study has investigated several grain-size fractions of feldspar from 13 volcaniclastic units. The feldspars show textural features that are visible in cathodoluminescence (CL) or back-scattered electron (BSE) images and can be subdivided into three dominant zoning-types: (1) compositional zoning, (2) round pseudo-oscillatory zoning and (3) resorbed and patchy zoning (Ginibre et al., 2004). Round pseudo-oscillatory zoning records a sensitive alternation of Fe and Ca that also reflects resorption processes. This is only visible in CL images. Compositional zoning reflects anticorrelated anorthite and orthoclase contents and is visible in BSE. Eleven inverse isochron ages from total fusion and three from stepwise heating analyses fit the age model. Four experiments resulted in older inverse isochron ages that do not concur with the model within 2σ uncertainties and that deviate from 1 ka to 17 ka minimum. C- and R-type zoning are interpreted as representing growth in magma chamber cupolas, as wall mushes, or in narrow conduits. Persistent compositions of PO-type crystals and abundant surfaces recording dissolution features correspond to formation within a magma chamber. C-type zoning and R-type zoning have revealed an irregular incorporation of melt and fluid inclusions. These two types of zoning in feldspar are interpreted as preferentially contributing either heterogeneously distributed excess 40Ar or inherited 40Ar to the deviating 40Ar/39Ar ages that are discussed in this study. © 2017 Elsevier Ltd
cited By 4
Keywords: argon-argon dating; feldspar; grain size; lacustrine deposit; radiocarbon dating; sediment core; volcaniclastic deposit; Lake Van; Turkey

Fifteen years of the Chinese continental scientific drilling program - Xu, Zhiqin; Yang, Jingsui; Wang, Chengshan; An, ZhiSheng; Li, Haibing; Wang, Qin; Su, Dechen (Scientific Drilling, 2017)
Continental scientific drilling can be regarded as a telescope into the Earth's interior because it provides process insight and uncompromised samples of rocks, fluids, and even sampled from the deep biosphere from the Earth's surface to great depths. As one of the three founding members of the International Continental Scientific Drilling Program (ICDP), ICDP China has made great achievements in many scientific drilling-related research fields. Based on the ICDP participation it attracted global attention of scientists and set up not only the Chinese Continental Scientific Drilling (CCSD) Program in 2001 but also a growing number of ambitious drilling projects in the country. The 5158m deep borehole of the CCSD project at Donghai County in the Sulu ultrahigh-pressure metamorphic terrain demonstrates that large amounts of crustal rocks of the South China Block have been subducted to at least 120 km, followed by rapid uplift. After successful completion of drilling at Donghai, several continental scientific drilling projects were conducted with funding of the Chinese government and partially with support of ICDP, resulting in a total drilling depth of more than 35 000 m. These projects encompass the Continental Environmental Scientific Drilling Program of China, the Scientific Drilling Project of Wenchuan Earthquake Fault Zone, the Continental Scientific Drilling Project of Cretaceous Songliao Basin, and the Program of Selected Continental Scientific Drilling and Experiments. On the occasion of the 20th anniversary of the ICDP and the 15th anniversary of the CCSD Program, this paper reviews the history and major progress of the CCSD Program. © Author(s) 2017.
Keywords: Earthquakes; Metamorphic rocks; Chinese Government; Continental scientific drillings; Drilling projects; Earth' s interior; Scientific drilling; South China block; Ultrahigh-pressure metamorphic; Wenchuan Earthquake; Drilling fluids

Evidence for a chondritic impactor, evaporation-condensation effects and melting of the Precambrian basement beneath the 'target' Deccan basalts at Lonar crater, India - Das Gupta, R.; Banerjee, A.; Goderis, S.; Claeys, P.; Vanhaecke, F.; Chakrabarti, R. (Geochimica et Cosmochimica Acta, 2017)
The ∼1.88 km diameter Lonar impact crater formed ∼570 ka ago and is an almost circular depression hosted entirely in the Poladpur suite of the ∼65 Ma old basalts of the Deccan Traps. To understand the effects of impact cratering on basaltic targets, commonly found on the surfaces of inner Solar System planetary bodies, major and trace element concentrations as well as Nd and Sr isotopic compositions were determined on a suite of selected samples composed of: basalts, a red bole sample, which is a product of basalt alteration, impact breccia, and impact glasses, either in the form of spherules ( <1 mm in diameter) or non-spherical impact glasses ( >1 mm and <1 cm). These data include the first highly siderophile element (HSE) concentrations for the Lonar spherules. The chemical index of alteration (CIA) values for the basalts and impact breccia (36.4 –42.7) are low while the red bole sample shows a high CIA value (55.6 in the acid-leached sample), consistent with its origin by aqueous alteration of the basalts. The Lonar spherules are classified into two main groups based on their CIA values. Most spherules show low CIA values (Group 1: 34.7 –40.5) overlapping with the basalts and impact breccia, while seven spherules show significantly higher CIA values (Group 2: >43.0). The Group 1 spherules are further subdivided into Groups 1a and 1b, with Group 1a spherules showing higher Ni and mostly higher Cr compared to the Group 1b spherules. Iridium and Cr concentrations of the spherules are consistent with the admixture of 1 –8 wt% of a chondritic impactor to the basaltic target rocks. The impactor contribution is most prominent in the Group 1a and Group 2 spherules, which show higher Ni/Co, Ni/Cr and Cr/Co ratios compared to the target basalts. In contrast, the Group 1b spherules show major and trace element compositions that overlap with those of the impact breccia and are characterized by high EFTh (Enrichment Factor for Th defined as the Nb-normalized concentration of Th relative to that of the average basalt) as well as fractionated La/Sm(N), and higher large ion lithophile element (LILE) concentrations compared to the basalts. The relatively more radiogenic Sr and less radiogenic Nd isotopic composition of the impact breccia and non-spherical impact glasses compared to the target basalts are consistent with melting and mixing of the Precambrian basement beneath the Deccan basalt with up to 15 wt% contribution of the basement to these samples. Variations in the moderately siderophile element (MSE) concentration ratios of the impact breccia as well as all the spherules are best explained by contributions from three components – a chondritic impactor, the basaltic target rocks at Lonar and the basement underlying the Deccan basalts. The large variations in concentrations of volatile elements like Zn and Cu and correlated variations of EFCu-EFZn, EFPb-EFZn, EFK-EFZn and EFNa-EFZn, particularly in the Group 1a spherules, are best explained by evaporation-condensation effects during impact. While most spherules, irrespective of their general major and trace element composition, show a loss in volatile elements (e.g., Zn and Cu) relative to the target basalts, some spherules, mainly of Group 1, display enrichments in these elements that are interpreted to reflect the unique preservation of volatile-rich vapour condensates resulting from geochemical fractionation in a vertical direction within the vapour cloud. © 2017 Elsevier Ltd
cited By 13

Environmental implications of salt facies in the Dead Sea - Kiro, Yael; Goldstein, Steven L.; Lazar, Boaz; Stein, Mordechai (GSA Bulletin, 2016)
Thick sequences of salt (halite) have been recovered in a 456-m-long core drilled at the deepest floor of the Dead Sea by the Dead Sea Deep Drilling Project and extending ∼200 k.y. back in time. The salt sequences were precipitated in the ancient lake that occupied the Dead Sea Basin during the last three interglacials during intervals of extreme aridity in the lake’s watershed. The salt layers alternate with “mud” layers that indicate wetter periods in the watershed, when floods transported fine detritus matter to the lake. The salt sources include brine discharge and freshwater runoff that dissolved halite units. Dissolved salts accumulated in the lake during glacials and relatively wet periods when the lake expanded, and precipitated during interglacials when the lake levels dropped.This study establishes for the first time the evaporite facies and sedimentological features of the deep Dead Sea brine during interglacial periods, by using the modern precipitation of halite in the Dead Sea as an analogue for past halite depositional periods as recorded in the drill core. The halite intervals provide a record of facies characterizing a deep-water evaporitic environment. The halite layers consist mainly of two types of crystals: small cumulate crystals containing halite rafts, which indicate precipitation from the surface brine of the lake (epilimnion), and bottom-growth (usually large) halite crystals that precipitated on the lake floor (hypolimnion). The layers of small halite crystals formed during drier periods as compared to the bottom-growth crystals. The bottom-growth halite crystals contain variable quantities of detritus and show mild dissolution structures at the contact between the mud and the halite crystals. These two main types of halite, in combination with “muds” and gypsum, comprise seven categories of salt facies that reflect the hydrological conditions (dry-to-wet), and that display a cyclic (decadal to millennial) pattern along the sampled core intervals. Frequent alternation of these two salt crystal types suggests seasonal changes, whereby the small cumulate crystals were formed during the summer, and the bottom-growth crystals were formed during the winter, when the surface temperatures of the lake were low, and the surface water was less saline and less likely to be saturated with respect to halite. Comparison of the last interglacial halite with the modern halite facies, together with the absence of significant dissolution features within the halite and the cyclic nature of the facies, indicates that the lake was continuously deep ( >100 m) during the last 200 k.y.

Peak-ring structure and kinematics from a multi-disciplinary study of the Schr{odinger impact basin - Kring, D.A.; Kramer, G.Y.; Collins, G.S.; Potter, R.W.K.; Chandnani, M. (Nature Communications, 2016)
The Schr{odinger basin on the lunar farside is â ;1/4320 km in diameter and the best-preserved peak-ring basin of its size in the Earth-Moon system. Here we present spectral and photogeologic analyses of data from the Moon Mineralogy Mapper instrument on the Chandrayaan-1 spacecraft and the Lunar Reconnaissance Orbiter Camera (LROC) on the LRO spacecraft, which indicates the peak ring is composed of anorthositic, noritic and troctolitic lithologies that were juxtaposed by several cross-cutting faults during peak-ring formation. Hydrocode simulations indicate the lithologies were uplifted from depths up to 30 km, representing the crust of the lunar farside. Through combining geological and remote-sensing observations with numerical modelling, we show that a Displaced Structural Uplift model is best for peak rings, including that in the K-T Chicxulub impact crater on Earth. These results may help guide sample selection in lunar sample return missions that are being studied for the multi-Agency International Space Exploration Coordination Group. © The Author(s) 2016.
cited By 33

Petrography and the REE-composition of apatite in the Paleoproterozoic Pilguj{arvi sedimentary Formation, Pechenga Greenstone Belt, Russia - Joosu, Lauri; Lepland, Aivo; Kreitsmann, Timmu; {Upraus, K{art; Roberts, Nick MW; Paiste, P{a{arn; Martin, Adam P; Kirsim{ae, Kalle (Geochimica et Cosmochimica Acta, 2016)

Petrology, geochemistry and fluid inclusion analysis of altered komatiites of the Mendon Formation in the BARB4 drill core, Barberton greenstone belt, South Africa - Farber, K.; Dziggel, A.; Meyer, F.M.; Harris, C. (South African Journal of Geology, 2016)
The 3.33 to 3.26 Ga Mendon Formation in the Palaeoarchaean Barberton greenstone belt, South Africa, forms the uppermost unit of the Onverwacht Group. It is dominated by ultramafic volcanic rocks interbedded with thin layers of cherty sediments that show pervasive alteration, including widespread serpentinisation, silicification and chert and quartz veining. The BARB4 drill core of the ICDP Barberton drilling project exposes a unique section through the Mendon Formation in the Manzimnyama Syncline. The komatiites are pervasively altered to an assemblage comprising quartz, chlorite, carbonate, talc, biotite, and, locally, plagioclase, K-feldspar, muscovite, amphibole, stilpnomelane and ankerite. The overlying sediments are made up of banded iron formations and rare beds of siliciclastic rocks. Though the altered komatiites are pervasively silicified, SiO, contents do not exceed 58 wt.%, and their major and trace element geochemistry is similar to other komatiitic rocks of the Mendon Formation, particularly those of the M2v-member. Quartz veins and, less commonly, quartz-carbonate and quartz-carbonate-plagioclase veins are found throughout the core. Overall, composition and texture of the veins differ from primary and early diagenetic veins found in silicified komatiites elsewhere in the Barberton greenstone belt. In the BARB4 drill core, the veins are generally coarse-grained, and the immediate wall rocks are locally foliated along the vein margins. In addition, the δ18O values of vein quartz range from 14.1 to 15.3%o, significantly lower than the values typically found in veins on the modern seafloor that formed during low temperature hydrothermal seafloor alteration (∼22 to 32%o). Fluid inclusions in vein quartz are homogeneous two-phase (L+V) aqueous inclusions that occur in trans- and intragranular trails and clusters. Intragranular and isolated fluid inclusions have a similar homogenisation temperature (Th) of 130 to 200°C, with most data ranging between 145 and 175°C. Salinities cluster in three different groups of high (20 to 27wt.% NaCl equiv.), medium (10 to 15wt.% NaCl equiv.) and low salinity (0.3 to 1.5wt.% NaCl equiv.). The composition and microthermometric characteristics of the fluid inclusions analysed within the drill core show similarities to those found in quartz veins in silicified komatiites of the Mendon Formation, which are interpreted to have been entrapped during metamorphism. P-T calculations based on fluid inclusion microthermometry reveal conditions of 230 to 400 MPa and 250 to 400°C. Similar conditions of 240 to 270°C have been obtained using oxygen isotope thermometry, assuming a metamorphic fluid with a δ180 value of 6%o. Collectively, the δ18O values, together with the texture and composition of the veins, are interpreted to indicate a metamorphic origin of the veins. The presence of high salinity inclusions indicates the occurrence of a highly saline fluid that locally mixed with the dominant lower salinity fluids. The high salinity might have been derived from fluid circulation through evaporites. © 2016 December Geological Society of South Africa.
Keywords: Barberton Greenstone Belt; banded iron formation; fluid inclusion; greenstone belt; komatiite; metamorphism; petrology; quartz vein; ultramafic rock

Pollen-based paleoenvironmental and paleoclimatic change at Lake Ohrid (south-eastern Europe) during the past 500 ka - Sadori, Laura; Koutsodendris, Andreas; Panagiotopoulos, Konstantinos; Masi, Alessia; Bertini, Adele; Combourieu-Nebout, Nathalie; Francke, Alexander; Kouli, Katerina; Joannin, Sebastien; Mercuri, Anna Maria; Peyron, Odile; Torri, Paola; et al. (Biogeosciences, 2016)
Lake Ohrid is located at the border between FYROM (Former Yugoslavian Republic of Macedonia) and Albania and formed during the latest phases of Alpine orogenesis. It is the deepest, the largest and the oldest tectonic lake in Europe. To better understand the paleoclimatic and paleoenvironmental evolution of Lake Ohrid, deep drilling was carried out in 2013 within the framework of the Scientific Collaboration on Past Speciation Conditions (SCOPSCO) project that was funded by the International Continental Scientific Drilling Program (ICDP). Preliminary results indicate that lacustrine sedimentation of Lake Ohrid started between 1.2 and 1.9 Ma ago. Here we present new pollen data (selected percentage and concentration taxa/groups) of the uppermost ∼ 200 m of the 569 m long DEEP core drilled in the depocentre of Lake Ohrid. The study is the fruit of a cooperative work carried out in several European palynological laboratories. The age model of this part of the core is based on 10 tephra layers and on tuning of biogeochemical proxy data to orbital parameters. According to the age model, the studied sequence covers the last ∼ 500 000 years at a millennial-scale resolution ( ∼ 1.6 ka) and records the major vegetation and climate changes that occurred during the last 12 (13 only pro parte) marine isotope stages (MIS). Our results indicate that there is a general good correspondence between forested/non-forested periods and glacial-interglacial cycles of the marine isotope stratigraphy. The record shows a progressive change from cooler and wetter to warmer and drier interglacial conditions. This shift in temperature and moisture availability is visible also in vegetation during glacial periods. The period corresponding to MIS11 (pollen assemblage zone OD-10, 428-368 ka BP) is dominated by montane trees such as conifers. Mesophilous elements such as deciduous and semi-deciduous oaks dominate forest periods of MIS5 (PASZ OD-3, 129-70 ka BP) and MIS1 (PASZ OD-1, 14 ka BP to present). Moreover, MIS7 (PASZ OD-6, 245-190 ka) shows a very high interglacial variability, with alternating expansions of montane and mesophilous arboreal taxa. Grasslands (open vegetation formations requiring relatively humid conditions) characterize the earlier glacial phases of MIS12 (PASZ OD-12, 488-459 ka), MIS10 (corresponding to the central part of PASZ OD-10, 428-366 ka) and MIS8 (PASZ OD-7, 288-245 ka). Steppes (open vegetation formations typical of dry environments) prevail during MIS6 (OD-5 and OD-4, 190-129 ka) and during MIS4-2 (PASZ OD-2, 70-14 ka). Our palynological results support the notion that Lake Ohrid has been a refugium area for both temperate and montane trees during glacials. Closer comparisons with other long southern European and Near Eastern pollen records will be achieved through ongoing high-resolution studies. © 2016 Author(s).
Keywords: Albania; Lake Ohrid; Macedonia [Southern Europe]; Coniferophyta; Quercus; Alpine orogeny; biogeochemical cycle; biostratigraphy; climate variation; core analysis; deep drilling; interglacial; marine isotope stage; montane forest; paleobotany; paleoclimate; paleoenvironment; palynology; proxy climate record; refugium; tephra; vegetation dynamics

Propidium monoazide treatment to distinguish between live and dead methanogens in pure cultures and environmental samples - Heise, J.; Nega, M.; Alawi, M.; Wagner, D. (Journal of Microbiological Methods, 2016)
In clinical trials investigating human health and in the analysis of microbial communities in cultures and natural environments, it is a substantial challenge to differentiate between living, potentially active communities and dead cells. The DNA-intercalating dye propidium monoazide (PMA) enables the selective masking of DNA from dead, membrane-compromised cells immediately before DNA extraction. In the present study, we evaluated for the first time a PMA treatment for methanogenic archaea in cultures and particle-rich environmental samples. Using microscopic analyses, we confirmed the applicability of the LIVE/DEAD® BacLight™ kit to methanogenic archaea and demonstrated the maintenance of intact cell membranes of methanogens in the presence of PMA. Although strain-specific differences in the efficiency of PMA treatment to methanogenic archaea were observed, we developed an optimal procedure using 130μM PMA and 5min of photo-activation with blue LED light. The results showed that the effectiveness of the PMA treatment strongly depends on the texture of the sediment/soil: silt and clay-rich sediments represent a challenge at all concentrations, whereas successful suppression of DNA from dead cells with compromised membranes was possible for low particle loads of sandy soil (total suspended solids (TSS)≤200mgmL-1). Conclusively, we present two strategies to overcome the problem of insufficient light activation of PMA caused by the turbidity effect (shielding) in particle-rich environmental samples by (i) dilution of the particle-rich sample and (ii) detachment of the cells and the free DNA from the sediment prior to a PMA treatment. Both strategies promise to be usable options for distinguishing living cells and free DNA in complex environmental samples. © 2015 Elsevier B.V.
cited By 25
Keywords: DNA; dye; propidium monoazide; unclassified drug; azide; bacterial DNA; humic substance; intercalating agent; propidium iodide; propidium monoazide; soil; Article; bacterial strain; cell membrane; cell viability; clay rich sediment; controlled study; culture technique; denaturing gradient gel electrophoresis; diagnostic kit; environment; feasibility study; fluorescence; humic substance; led light; light; membrane permeability; methanogenic archaeon; microscopy; nonhuman; particle rich environmental sample; particle size; photoactivation; polymerase chain reaction; priority journal; quantitative analysis; sandy soil; sediment; silt sediment; soil texture; suspended particulate matter; turbidity; analogs and derivatives; analysis; chemistry; classification; drug effects; Euryarchaeota; fluorescence microscopy; genetics; humic substance; isolation and purification; microbial viability; microbiological examination; microbiology; procedures; soil; Azides; Bacteriological Techniques; DNA; Bacterial; Environmental Microbiology; Euryarchaeota; Humic Substances; Intercalating Agents; Microbial Viability; Microscopy; Fluorescence; Polymerase Chain Reaction; Propidium; Soil; Soil Microbiology

Recording of climate and diagenesis through sedimentary DNA and fossil pigments at Laguna Potrok Aike, Argentina - Vuillemin, Aurèle; Ariztegui, Daniel; Leavitt, Peter R.; Bunting, Lynda; Anselmetti, Flavio; Corbella, Hugo; Francus, Pierre; L{ucke, Andreas; Maidana, Nora I.; Ohlendorf, Christian; Sch{abitz, Frank; Wastegård, Stefan; et al. (Biogeosciences, 2016)

(untitled) - Wilke, Thomas; Bocxlaer

Relationship between total organic carbon content and sedimentation rate of the Upper Cretaceous source rocks in Well CCSD-SK-1n Songliao Basin (in Chinese with English abstract); [松辽盆地松科1井上白垩统烃源岩有机碳含量与沉积速率的关系] - Cha, Y.; Wu, X.; Yu, D. (Journal of Palaeogeography, 2016)

Scientific drilling projects in ancient lakes: Integrating geological and biological histories - Wilke, T.; Wagner, B.; Van Bocxlaer, B.; Albrecht, C.; Ariztegui, D.; Delicado, D.; Francke, A.; Harzhauser, M.; Hauffe, T.; Holtvoeth, J.; Just, J.; Leng, M.J.; et al. (Global and Planetary Change, 2016)
Sedimentary sequences in ancient or long-lived lakes can reach several thousands of meters in thickness and often provide an unrivalled perspective of the lake's regional climatic, environmental, and biological history. Over the last few years, deep-drilling projects in ancient lakes became increasingly multi- and interdisciplinary, as, among others, seismological, sedimentological, biogeochemical, climatic, environmental, paleontological, and evolutionary information can be obtained from sediment cores. However, these multi- and interdisciplinary projects pose several challenges. The scientists involved typically approach problems from different scientific perspectives and backgrounds, and setting up the program requires clear communication and the alignment of interests. One of the most challenging tasks, besides the actual drilling operation, is to link diverse datasets with varying resolution, data quality, and age uncertainties to answer interdisciplinary questions synthetically and coherently. These problems are especially relevant when secondary data, i.e., datasets obtained independently of the drilling operation, are incorporated in analyses. Nonetheless, the inclusion of secondary information, such as isotopic data from fossils found in outcrops or genetic data from extant species, may help to achieve synthetic answers. Recent technological and methodological advances in paleolimnology are likely to increase the possibilities of integrating secondary information. Some of the new approaches have started to revolutionize scientific drilling in ancient lakes, but at the same time, they also add a new layer of complexity to the generation and analysis of sediment-core data. The enhanced opportunities presented by new scientific approaches to study the paleolimnological history of these lakes, therefore, come at the expense of higher logistic, communication, and analytical efforts. Here we review types of data that can be obtained in ancient lake drilling projects and the analytical approaches that can be applied to empirically and statistically link diverse datasets to create an integrative perspective on geological and biological data. In doing so, we highlight strengths and potential weaknesses of new methods and analyses, and provide recommendations for future interdisciplinary deep-drilling projects. © 2016 Elsevier B.V.
cited By 24
Keywords: Biology; Geology; Paleolimnology; Analytical approach; Ancient lakes; Deep drilling; Evolutionary biology; Evolutionary information; Interdisciplinary project; Methodology; Sedimentary sequence; Lakes; biological survey; core analysis; data quality; deep drilling; evolutionary biology; fossil record; geological theory; integrated approach; lacustrine environment; outcrop; paleolimnology; technological change

Scientific drilling projects in ancient lakes: Integrating geological and biological histories - Wilke, Thomas; Wagner, Bernd; Van Bocxlaer, Bert; Albrecht, Christian; Ariztegui, Daniel; Delicado, Diana; Francke, Alexander; Harzhauser, Mathias; Hauffe, Torsten; Holtvoeth, Jens; Just, Janna; Leng, Melanie J.; et al. (Global and Planetary Change, 2016)
Sedimentary sequences in ancient or long-lived lakes can reach several thousands of meters in thickness and often provide an unrivalled perspective of the lake's regional climatic, environmental, and biological history. Over the last few years, deep-drilling projects in ancient lakes became increasingly multi- and interdisciplinary, as, among others, seismological, sedimentological, biogeochemical, climatic, environmental, paleontological, and evolutionary information can be obtained from sediment cores. However, these multi- and interdisciplinary projects pose several challenges. The scientists involved typically approach problems from different scientific perspectives and backgrounds, and setting up the program requires clear communication and the alignment of interests. One of the most challenging tasks, besides the actual drilling operation, is to link diverse datasets with varying resolution, data quality, and age uncertainties to answer interdisciplinary questions synthetically and coherently. These problems are especially relevant when secondary data, i.e., datasets obtained independently of the drilling operation, are incorporated in analyses. Nonetheless, the inclusion of secondary information, such as isotopic data from fossils found in outcrops or genetic data from extant species, may help to achieve synthetic answers. Recent technological and methodological advances in paleolimnology are likely to increase the possibilities of integrating secondary information. Some of the new approaches have started to revolutionize scientific drilling in ancient lakes, but at the same time, they also add a new layer of complexity to the generation and analysis of sediment-core data. The enhanced opportunities presented by new scientific approaches to study the paleolimnological history of these lakes, therefore, come at the expense of higher logistic, communication, and analytical efforts. Here we review types of data that can be obtained in ancient lake drilling projects and the analytical approaches that can be applied to empirically and statistically link diverse datasets to create an integrative perspective on geological and biological data. In doing so, we highlight strengths and potential weaknesses of new methods and analyses, and provide recommendations for future interdisciplinary deep-drilling projects. © 2016 Elsevier B.V.
Keywords: Biology; Geology; Paleolimnology; Analytical approach; Ancient lakes; Deep drilling; Evolutionary biology; Evolutionary information; Interdisciplinary project; Methodology; Sedimentary sequence; biological survey; core analysis; data quality; deep drilling; evolutionary biology; fossil record; geological theory; integrated approach; lacustrine environment; outcrop; paleolimnology; technological change; Lakes

Scientific drilling projects in ancient lakes: Integrating geological and biological histories - Wilke, T.; Wagner, B.; Van Bocxlaer, B.; Albrecht, C.; Ariztegui, D.; Delicado, D.; Francke, A.; Harzhauser, M.; Hauffe, T.; Holtvoeth, J.; Just, J.; Leng, M.J.; et al. (Global and Planetary Change, 2016)
Sedimentary sequences in ancient or long-lived lakes can reach several thousands of meters in thickness and often provide an unrivalled perspective of the lake's regional climatic, environmental, and biological history. Over the last few years, deep-drilling projects in ancient lakes became increasingly multi- and interdisciplinary, as, among others, seismological, sedimentological, biogeochemical, climatic, environmental, paleontological, and evolutionary information can be obtained from sediment cores. However, these multi- and interdisciplinary projects pose several challenges. The scientists involved typically approach problems from different scientific perspectives and backgrounds, and setting up the program requires clear communication and the alignment of interests. One of the most challenging tasks, besides the actual drilling operation, is to link diverse datasets with varying resolution, data quality, and age uncertainties to answer interdisciplinary questions synthetically and coherently. These problems are especially relevant when secondary data, i.e., datasets obtained independently of the drilling operation, are incorporated in analyses. Nonetheless, the inclusion of secondary information, such as isotopic data from fossils found in outcrops or genetic data from extant species, may help to achieve synthetic answers. Recent technological and methodological advances in paleolimnology are likely to increase the possibilities of integrating secondary information. Some of the new approaches have started to revolutionize scientific drilling in ancient lakes, but at the same time, they also add a new layer of complexity to the generation and analysis of sediment-core data. The enhanced opportunities presented by new scientific approaches to study the paleolimnological history of these lakes, therefore, come at the expense of higher logistic, communication, and analytical efforts. Here we review types of data that can be obtained in ancient lake drilling projects and the analytical approaches that can be applied to empirically and statistically link diverse datasets to create an integrative perspective on geological and biological data. In doing so, we highlight strengths and potential weaknesses of new methods and analyses, and provide recommendations for future interdisciplinary deep-drilling projects. © 2016 Elsevier B.V.
cited By 29
Keywords: Biology; Geology; Paleolimnology; Analytical approach; Ancient lakes; Deep drilling; Evolutionary biology; Evolutionary information; Interdisciplinary project; Methodology; Sedimentary sequence; Lakes; biological survey; core analysis; data quality; deep drilling; evolutionary biology; fossil record; geological theory; integrated approach; lacustrine environment; outcrop; paleolimnology; technological change

Scientific drilling projects in ancient lakes: Integrating geological and biological histories - Wilke, T.; Wagner, B.; Van Bocxlaer, B.; Albrecht, C.; Ariztegui, D.; Delicado, D.; Francke, A.; Harzhauser, M.; Hauffe, T.; Holtvoeth, J.; Just, J.; Leng, M.J.; et al. (Global and Planetary Change, 2016)
Sedimentary sequences in ancient or long-lived lakes can reach several thousands of meters in thickness and often provide an unrivalled perspective of the lake's regional climatic, environmental, and biological history. Over the last few years, deep-drilling projects in ancient lakes became increasingly multi- and interdisciplinary, as, among others, seismological, sedimentological, biogeochemical, climatic, environmental, paleontological, and evolutionary information can be obtained from sediment cores. However, these multi- and interdisciplinary projects pose several challenges. The scientists involved typically approach problems from different scientific perspectives and backgrounds, and setting up the program requires clear communication and the alignment of interests. One of the most challenging tasks, besides the actual drilling operation, is to link diverse datasets with varying resolution, data quality, and age uncertainties to answer interdisciplinary questions synthetically and coherently. These problems are especially relevant when secondary data, i.e., datasets obtained independently of the drilling operation, are incorporated in analyses. Nonetheless, the inclusion of secondary information, such as isotopic data from fossils found in outcrops or genetic data from extant species, may help to achieve synthetic answers. Recent technological and methodological advances in paleolimnology are likely to increase the possibilities of integrating secondary information. Some of the new approaches have started to revolutionize scientific drilling in ancient lakes, but at the same time, they also add a new layer of complexity to the generation and analysis of sediment-core data. The enhanced opportunities presented by new scientific approaches to study the paleolimnological history of these lakes, therefore, come at the expense of higher logistic, communication, and analytical efforts. Here we review types of data that can be obtained in ancient lake drilling projects and the analytical approaches that can be applied to empirically and statistically link diverse datasets to create an integrative perspective on geological and biological data. In doing so, we highlight strengths and potential weaknesses of new methods and analyses, and provide recommendations for future interdisciplinary deep-drilling projects. © 2016 Elsevier B.V.
cited By 26
Keywords: Biology; Geology; Paleolimnology; Analytical approach; Ancient lakes; Deep drilling; Evolutionary biology; Evolutionary information; Interdisciplinary project; Methodology; Sedimentary sequence; Lakes; biological survey; core analysis; data quality; deep drilling; evolutionary biology; fossil record; geological theory; integrated approach; lacustrine environment; outcrop; paleolimnology; technological change

P-And S-wave seismic imaging of overdeepened alpine valleys - Buness, H.; Burschil, T.; Gabriel, G. (22nd European Meeting of Environmental and Engineering Geophysics, Near Surface Geoscience 2016, 2016)
Overdeepened valleys and basin can be found in glaciated regions worldwide. Due to their geological, ecological, and societal relevance they constitute a relevant geoscientific target. In preparation for an ICDP project (Drilling Overdeepened Alpine Valleys, DOVE), we carried out several reflection seismic surveys using high-resolution P-wave, horizontally pola¬ri¬zed SH-wave, and multi-component (SV-And SH-wave sources, 3-component re¬ceiver) techniques at a test site in the Tannwald basin north of Lake Constance. The first results of the P-And SH-wave reflection profiles are presented here. The seismic sections image well the internal valley structure of the Tannwald Basin; different facies are also distinguishable in the glacial sediments. The combined inter¬pretation of P-wave and SH-wave reflection seismics reveal more details than just one technique on its own by providing complementary information. P-wave seismics show a more coherent image with a higher penetration depth, while SHwave seismics partly resolve more details due to their higher resolution. The combination promises to be an enhanced tool to investigate sedimentary successions in advance of scientific drilling.
cited By 0
Keywords: Geology; Geophysics; Landforms; Seismic waves; Seismology; Coherent images; Glacial sediments; High resolution; Higher resolution; Multicomponents; Reflection seismic; Scientific drilling; Seismic sections; Shear waves

Millennial to orbital-scale variations of drought intensity in the Eastern Mediterranean - Stockhecke, M.; Timmermann, A.; Kipfer, R.; Haug, G.H.; Kwiecien, O.; Friedrich, T.; Menviel, L.; Litt, T.; Pickarski, N.; Anselmetti, F.S. (Quaternary Science Reviews, 2016)
Millennial to orbital-scale rainfall changes in the Mediterranean region and corresponding variations in vegetation patterns were the result of large-scale atmospheric reorganizations. In spite of recent efforts to reconstruct this variability using a range of proxy archives, the underlying physical mechanisms have remained elusive. Through the analysis of a new high-resolution sedimentary section from Lake Van (Turkey) along with climate modeling experiments, we identify massive droughts in the Eastern Mediterranean for the past four glacial cycles, which have a pervasive link with known intervals of enhanced North Atlantic glacial iceberg calving, weaker Atlantic Meridional Overturning Circulation and Dansgaard-Oeschger cold conditions. On orbital timescales, the topographic effect of large Northern Hemisphere ice sheets and periods with minimum insolation seasonality further exacerbated drought intensities by suppressing both summer and winter precipitation. © 2015 Elsevier Ltd.
cited By 68
Keywords: Glacial geology; Lakes; Sea ice; Atlantic meridional overturning circulations; Atmospheric reorganization; Dansgaard-Oeschger variability; Eastern Mediterranean; ICDP PALEOVAN; Insolation seasonality; Lake vans; Milankovitch cycle; Drought; climate change; climate modeling; Dansgaard-Oeschger cycle; drought; ice sheet; iceberg calving; Last Glacial-Interglacial; Mediterranean environment; Northern Hemisphere; paleoclimate; precipitation (climatology); seasonality; sediment analysis; Atlantic Ocean; Atlantic Ocean (North); Lake Van; Turkey

Oxide and diamond nanoparticles modified drilling fluid for deep, complicated drilling conditions - Liu, B.C.; Liu, S.Q.; Chen, Z.R.; Meng, Q.N.; Li, C. (Journal of Nanoscience and Nanotechnology, 2016)
In the context of well drilling and during the process of drilling down and tripping out of drill string, it is the inevitable contact and friction between drill pipe and casing that causes the wear of the drill pipe and casing tube, especially in the case of drilling deep, ultra-deep, and horizontal wells. Compared with steel drill pipe, the wear of aluminum alloy drill pipe appears to be more serious. Nanoparticles as additives in drilling fluids could potentially reduce mechanical friction, greatly enhancing the lubricating properties of drilling fluids and subsequently reducing the drill pipe and casing materials surface losses. Within this study an attempt has been made to improve the lubricating properties of drilling fluid with regard to deep, complicated drilling conditions by adding oxide nanoparticles to the fluid. Spherical alumina (Al2O3), titania (TiO2), silica (SiO8) and diamond nanoparticles were selected as drilling fluid additives. Effects of different types and concentrations of oxide nanoparticle additives on lubricating properties and friction reduction of drilling fluid have been studied by using an extreme pressure lubrication device and a pin-on-disk tester. In pin-on-disk tests, the pin material was AISI316 steel (casing material) and the disk material was 7075 aluminum alloy (drill pipe material). The pin-on-disk friction and wear tests were carried out under the condition that the pin and disk were immerged in drilling fluid. Results indicated that the lubricating properties of waterbased drilling fluid significantly improved upon adding an appropriate amount of SiO2 nanoparticles, meanwhile TiO2, Al2O3 and diamond nanoparticles had limited effects on the lubricating properties of drilling fluid. The LR (lubricating factor reduce rate) of drilling fluid increased to the maximum value of 16.6% at 0.5 wt% SiO2 nanoparticles addition. The WV (wear volume) of aluminum alloy disc decreased to the minimum value of 0.31 mm3 at 0.4 wt% SiO2 nanoparticles addition. On the basis of the above experimental results, 0.4 wt% SiO2 nanoparticles were added to the oil based drilling fluids used in SK-II well drilling, which is a scientific continental drilling project in the Cretaceous Songliao Basin of northeast China. Results showed that the lubricating coefficient of the drilling fluid was reduced by 20.3%, the friction factor reduction rate was increased by 29.7%, and the aluminum disc wear volume decreased by 26.3%. Copyright © 2016 American Scientific Publishers All rights reserved.
cited By 7
Keywords: Alumina; Aluminum alloys; Aluminum oxide; Diamond drilling; Diamonds; Drill pipe; Drill strings; Drilling fluids; Drills; Friction; Horizontal drilling; Horizontal wells; Silica nanoparticles; Titanium dioxide; Tribology; Wear resistance; Diamond nano-particles; Drilling fluid additives; Lubricating properties; Lubrication devices; Oil-based drilling fluid; Pin on disk; Pin on disk friction; Water-based drilling fluid; Oil well drilling

Origin and diversification of Lake Ohrid's endemic acroloxid limpets: the role of geography and ecology - Stelbrink, Bj{orn; Shirokaya, Alena A.; F{oller, Kirstin; Wilke, Thomas; Albrecht, Christian (BMC Evolutionary Biology, 2016)
Background: Ancient Lake Ohrid, located on the Albania-Macedonia border, is the most biodiverse freshwater lake in Europe. However, the processes that gave rise to its extraordinary endemic biodiversity, particularly in the species-rich gastropods, are still poorly understood. A suitable model taxon to study speciation processes in Lake Ohrid is the pulmonate snail genus Acroloxus, which comprises two morphologically distinct and ecologically (vertically) separated endemic species. Using a multilocus phylogenetic framework of Acroloxus limpets from the Euro-Mediterranean subregion, together with molecular-clock and phylogeographic analyses of Ohrid taxa, we aimed to infer their geographic origin and the timing of colonization as well as the role of geography and ecology in intra-lacustrine diversification. Results: In contrast to most other endemic invertebrate groups in Lake Ohrid, the phylogenetic relationships of the endemic Ohrid Acroloxus species indicate that the Balkan region probably did not serve as their ancestral area. The inferred monophyly and estimated divergence times further suggest that these freshwater limpets colonized the lake only once and that the onset of intra-lacustrine diversification coincides with the time when the lake reached deep-water conditions ca 1.3 Mya. However, the difference in vertical distribution of these two ecologically distinct species is not reflected in the phylogeographic pattern observed. Instead, western and eastern populations are genetically more distinct, suggesting a horizontal structure. Conclusions: We conclude that both geography and ecology have played a role in the intra-lacustrine speciation process. Given the distinct morphology (sculptured vs. smooth shell) and ecology (littoral vs. sublittoral), and the timing of intra-lacustrine diversification inferred, we propose that the onset of deep-water conditions initially triggered ecological speciation. Subsequent geographic processes then gave rise to the phylogeographic patterns observed today. However, the generally weak genetic differentiation observed suggests incipient speciation, which might be explained by the comparatively young age of the lake system and thus the relatively recent onset of intra-lacustrine diversification. © 2016 The Author(s).
Keywords: Animals; Biodiversity; DNA; Mitochondrial; Ecosystem; Europe; Genetic Speciation; Lakes; Models; Biological; Phylogeny; Phylogeography; Sequence Analysis; DNA; Snails; Albania; Balkan; Lake Ohrid; Macedonia [Southern Europe]; Turkmenistan; Acroloxidae; Acroloxus; Gastropoda; Invertebrata; Mya; Patellidae; mitochondrial DNA; biodiversity; divergence; endemic species; genetic differentiation; lacustrine environment; molecular ecology; morphology; origin of life; phylogenetics; phylogeny; phylogeography; snail; speciation (biology); vertical distribution; animal; biodiversity; biological model; DNA sequence; ecosystem; Europe; genetics; lake; phylogeny; phylogeography; snail; species differentiation

Northern Mediterranean climate since the Middle Pleistocene: A 637 ka stable isotope record from Lake Ohrid (Albania/Macedonia) - Lacey, J.H.; Leng, M.J.; Francke, A.; Sloane, J.H.; Milodowski, A.; Vogel, H.; Baumgarten, H.; Zanchetta, G.; Wagner, B. (Biogeosciences, 2016)
Lake Ohrid (Macedonia/Albania) is an ancient lake with unique biodiversity and a site of global significance for investigating the influence of climate, geological, and tectonic events on the generation of endemic populations. Here, we present oxygen (δ18O) and carbon (δ13C) isotope data from carbonate over the upper 243 m of a composite core profile recovered as part of the Scientific Collaboration on Past Speciation Conditions in Lake Ohrid (SCOPSCO) project. The investigated sediment succession covers the past ca. 637 ka. Previous studies on short cores from the lake (up to 15 m, < 140 ka) have indicated the total inorganic carbon (TIC) content of sediments to be highly sensitive to climate change over the last glacial-interglacial cycle. Sediments corresponding to warmer periods contain abundant endogenic calcite; however, an overall low TIC content in glacial sediments is punctuated by discrete bands of early diagenetic authigenic siderite. Isotope measurements on endogenic calcite (δ18Oc and δ13Cc) reveal variations both between and within interglacials that suggest the lake has been subject to palaeoenvironmental change on orbital and millennial timescales. We also measured isotope ratios from authigenic siderite (δ18Os and δ13Cs) and, with the oxygen isotope composition of calcite and siderite, reconstruct δ18O of lake water (δ18Olw) over the last 637 ka. Interglacials have higher δ18Olw values when compared to glacial periods most likely due to changes in evaporation, summer temperature, the proportion of winter precipitation (snowfall), and inflow from adjacent Lake Prespa. The isotope stratigraphy suggests Lake Ohrid experienced a period of general stability from marine isotope stage (MIS) 15 to MIS 13, highlighting MIS 14 as a particularly warm glacial. Climate conditions became progressively wetter during MIS 11 and MIS 9. Interglacial periods after MIS 9 are characterised by increasingly evaporated and drier conditions through MIS 7, MIS 5, and the Holocene. Our results provide new evidence for long-term climate change in the northern Mediterranean region, which will form the basis to better understand the influence of major environmental events on biological evolution within Lake Ohrid. © Author(s) 2016.
cited By 31
Keywords: calcite; carbon isotope; climate variation; core analysis; glacial-interglacial cycle; long-term change; marine isotope stage; Mediterranean environment; oxygen isotope; paleoenvironment; reconstruction; siderite; stable isotope; Lake Mikri Prespa; Lake Ohrid

Nondestructive spectroscopic and petrochemical investigations of Paleoarchean spherule layers from the ICDP drill core BARB5, Barberton Mountain Land, South Africa - Fritz, J.; Tagle, R.; Ashworth, L.; Schmitt, R.T.; Hofmann, A.; Luais, B.; Harris, P.D.; Hoehnel, D.; {Ozdemir, S.; Mohr-Westheide, T.; Koeberl, C. (Meteoritics and Planetary Science, 2016)
A Paleoarchean impact spherule-bearing interval of the 763 m long International Continental Scientific Drilling Program (ICDP) drill core BARB5 from the lower Mapepe Formation of the Fig Tree Group, Barberton Mountain Land (South Africa) was investigated using nondestructive analytical techniques. The results of visual observation, infrared (IR) spectroscopic imaging, and micro-X-ray fluorescence (μXRF) of drill cores are presented. Petrographic and sedimentary features, as well as major and trace element compositions of lithologies from the micrometer to kilometer-scale, assisted in the localization and characterization of eight spherule-bearing intervals between 512.6 and 510.5 m depth. The spherule layers occur in a strongly deformed section between 517 and 503 m, and the rocks in the core above and below are clearly less disturbed. The μXRF element maps show that spherule layers have similar petrographic and geochemical characteristics but differences in (1) sorting of two types of spherules and (2) occurrence of primary minerals (Ni-Cr spinel and zircon). We favor a single impact scenario followed by postimpact reworking, and subsequent alteration. The spherule layers are Al2O3-rich and can be distinguished from the Al2O3-poor marine sediments by distinct Al-OH absorption features in the short wave infrared (SWIR) region of the electromagnetic spectrum. Infrared images can cover tens to hundreds of square meters of lithologies and, thus, may be used to search for Al-OH-rich spherule layers in Al2O3-poor sediments, such as Eoarchean metasediments, where the textural characteristics of the spherule layers are obscured by metamorphism. © The Meteoritical Society, 2016.
cited By 14

Nondestructive spectroscopic and petrochemical investigations of Paleoarchean spherule layers from the ICDP drill core BARB5, Barberton Mountain Land, South Africa - Fritz, J{org; Tagle, Roald; Ashworth, Luisa; Schmitt, Ralf Thomas; Hofmann, Axel; Luais, B'eatrice; Harris, Phillip D.; Hoehnel, Desir'ee; Ozdemir, Seda; Mohr-Westheide, Tanja; Koeberl, Christian (Meteoritics and Planetary Science, 2016)
A Paleoarchean impact spherule-bearing interval of the 763 m long International Continental Scientific Drilling Program (ICDP) drill core BARB5 from the lower Mapepe Formation of the Fig Tree Group, Barberton Mountain Land (South Africa) was investigated using nondestructive analytical techniques. The results of visual observation, infrared (IR) spectroscopic imaging, and micro-X-ray fluorescence (μXRF) of drill cores are presented. Petrographic and sedimentary features, as well as major and trace element compositions of lithologies from the micrometer to kilometer-scale, assisted in the localization and characterization of eight spherule-bearing intervals between 512.6 and 510.5 m depth. The spherule layers occur in a strongly deformed section between 517 and 503 m, and the rocks in the core above and below are clearly less disturbed. The μXRF element maps show that spherule layers have similar petrographic and geochemical characteristics but differences in (1) sorting of two types of spherules and (2) occurrence of primary minerals (Ni-Cr spinel and zircon). We favor a single impact scenario followed by postimpact reworking, and subsequent alteration. The spherule layers are Al2O3-rich and can be distinguished from the Al2O3-poor marine sediments by distinct Al-OH absorption features in the short wave infrared (SWIR) region of the electromagnetic spectrum. Infrared images can cover tens to hundreds of square meters of lithologies and, thus, may be used to search for Al-OH-rich spherule layers in Al2O3-poor sediments, such as Eoarchean metasediments, where the textural characteristics of the spherule layers are obscured by metamorphism. © The Meteoritical Society, 2016.

Noble gas composition and 40Ar/39Ar age in eclogites from the main hole of the Chinese Continental Scientific Drilling project - Hopp, Jens; Schwarz, Winfried H.; Trieloff, Mario; Meyer, Hans-Peter; Hanel, Michael; Altherr, Rainer (Contributions to Mineralogy and Petrology, 2016)
We present the first comprehensive noble gas study on eclogites. The four eclogite samples were recovered during the Chinese Continental Scientific Drilling and are from two distinct profile depth sections differing in their degree of interaction with meteoric water, based on their δ18O-values (surface related and of mantle-type). Hence, noble gas analyses offer the potential to further discriminate between shallow (meteoric) and deep (mantle) fluid sources. Noble gas compositions reveal typical crustal fluid compositions, characterized by a variable mixture of atmospheric gases with significant contributions of nucleogenic neon, radiogenic 4He*, radiogenic 40Ar*, fissiogenic 131 –136Xe, and presumably bariogenic 131Xe, but no significant addition of mantle gases. This signature can be also considered to represent one endmember component of eclogitic diamonds. Concentrations of non-radiogenic noble gases are rather low, with depletion of light relative to the heavier noble gases. Eclogites from lower depth which experienced a higher degree of interaction with meteoric water also showed higher contributions of atmospheric gas compared with eclogites recovered from greater depth. This is interpreted to result from interaction with high-salinity fluids during ultrahigh pressure (UHP). It demonstrates that the atmospheric noble gas abundance is a proxy for interaction with surface related fluids. 40Ar/39Ar (inverse) isochron ages of two phengite separates (241.2 ± 0.4 Ma and 275.0 ± 1.8 Ma, 1σ-errors) predate the main phase of UHP metamorphism (ca. 220 Ma). Biotite yields an integrated age of about 1100 Ma. These age values are interpreted to reflect the likely addition of excess 40Ar without any chronological meaning. © 2016, Springer-Verlag Berlin Heidelberg.
Keywords: argon-argon dating; chemical composition; Chinese Continental Scientific Drilling Project; concentration (composition); eclogite; fluid composition; meteoric water; noble gas; ultrahigh pressure metamorphism

Miocene relative sea level on the New Jersey shallow continental shelf and coastal plain derived from one-dimensional backstripping: A case for both eustasy and epeirogeny - Kominz, M.A.; Miller, K.G.; Browning, J.V.; Katz, M.E.; Mountain, G.S. (Geosphere, 2016)
Onshore drilling by Ocean Drilling Program (ODP) Legs 150X and 174AX and offshore drilling by Integrated Ocean Drilling Program (IODP) Expedition 313 provides continuous cores and logs of seismically imaged Lower to Middle Miocene sequences. We input ages and paleodepths of these sequences into one-dimensional backstripping equations, progressively accounting for the effects of compaction, Airy loading, and thermal subsidence. The resulting difference between observed subsidence and theoretical thermal subsidence provide relative sea-level curves that reflect both global average sea level and non-thermal subsidence. In contrast with expectations, backstripping suggests that the relative sea-level maxima in proximal onshore sites were lower than correlative maxima on the shelf. This requires that the onshore New Jersey coastal plain has subsided relative to the shelf, which is consistent with models of relative epeirogeny due to subduction of the Farallon plate. These models predict subsidence of the coastal plain relative to the shelf. Although onshore and offshore sea-level estimates are offset by epeirogeny, the amplitude of million-year-scale Early to Middle Miocene sea-level changes seen at the New Jersey margin is generally 5-20 m and occasionally as great as 50 m. These events are interpreted to represent eustatic variations, because they occur on a shorter time frame than epeirogenic influences. Correction for epeirogenic effects largely reconciles differences between onshore and offshore relative sea-level estimates and suggests that backstripping provides a testable eustatic model for the Early to Middle Miocene.
cited By 26
Keywords: Offshore drilling; Submarine geology; Subsidence; Tectonics; Continental shelves; Integrated ocean drilling programs; Middle Miocene; Ocean drilling programs; Offshore sea level; Onshore drilling; Relative sea level; Sealevel change; Sea level; coastal plain; continental shelf; eustacy; Miocene; Ocean Drilling Program; paleoceanography; New Jersey; United States

Millennial-scale vegetation changes in the north-eastern Russian Arctic during the Pliocene/Pleistocene transition (2.7 –2.5 Ma) inferred from the pollen record of Lake El'gygytgyn - Andreev, A.A.; Tarasov, P.E.; Wennrich, V.; Melles, M. (Quaternary Science Reviews, 2016)
The sediment record of Lake El'gygytgyn (67°30′N, 172°05′E) spans the past 3.6 Ma and provides unique opportunities for qualitative and quantitative reconstructions of the regional paleoenvironmental history of the terrestrial Arctic. Millennial-scale pollen studies of the sediments that accumulated during the Late Pliocene and Early Pleistocene (ca. 2.7 to 2.5 Ma) demonstrate orbitally-driven vegetation and climate changes during this transitional interval. Pollen spectra show a significant vegetation shift at the Pliocene/Pleistocene boundary that is, however, delayed by a few thousand years compared to lacustrine response. About 2.70 –2.68 Ma the vegetation at Lake El'gygytgyn, currently a tundra area was mostly dominated by larch forests with some shrub pine, shrub alder and dwarf birch in understory. During the marine isotope stages G3 and G1, ca. 2.665 –2.647 and 2.625 –2.617 Ma, some spruce trees grew in the local larch-pine forests, pointing to relatively warm climate conditions. At the beginning of the Pleistocene, around 2.588 Ma, a prominent climatic deterioration led to a change from larch-dominated forests to predominantly treeless steppe- and tundra-like habitats. Between ca. 2.56 –2.53 Ma some climate amelioration is reflected by the higher presence of coniferous taxa (mostly pine and larch, but probably also spruce) in the area. After 2.53 Ma a relatively cold and dry climate became dominant again, leading to open steppe-like and shrubby environments followed by climate amelioration between ca. 2.510 and 2.495 Ma, when pollen assemblages show that larch forests with dwarf birch and shrub alder still grew in the lake's vicinity. Increased contents of green algae colonies (Botryococcus) remains and Zygnema cysts around 2.691 –2.689, 2.679 –2.677, 2.601 –2.594, 2.564 –2.545, and 2.532 –2.510 Ma suggest a spread of shallow-water environments most likely due to a lake-level lowering. These events occurred simultaneously with dry climate conditions inferred from broad distribution of steppe habitats with Artemisia and other herbs. © 2016 Elsevier Ltd
cited By 19
Keywords: Algae; Climate change; Ecosystems; Forestry; Vegetation; Early pleistocene; Marine isotope stages; North-easter Russian Arctic; Pliocene; Pollen assemblage; Pollen record; Shallow water environment; Vegetation change; Lakes; climate variation; coniferous tree; fossil record; herb; lacustrine deposit; lake level; marine isotope stage; paleobotany; paleoenvironment; palynology; Pliocene-Pleistocene boundary; shrub; vegetation dynamics; Arctic; Russian Federation; Alnus; Artemisia; Betula nana; Botryococcus; Chlorophyta; Larix; Picea; Zygnema

Mid-Miocene record of large-scale Snake River-type explosive volcanism and associated subsidence on the Yellowstone hotspot track: The Cassia Formation of Idaho, USA - Knott, T.R.; Branney, M.J.; Reichow, M.K.; Finn, D.R.; Coe, R.S.; Storey, M.; Barfod, D.; McCurry, M. (Bulletin of the Geological Society of America, 2016)
The 1.95-km-thick Cassia Formation, defined in the Cassia Hills at the southern margin of the Snake River Plain, Idaho, consists of 12 refined and newly described rhyolitic members, each with distinctive field, geochemical, mineralogical, geochronological, and paleomagnetic characteristics. It records voluminous high-temperature, Snake River-type explosive eruptions between ca. 11.3 Ma and ca. 8.1 Ma that emplaced intensely welded rheomorphic ignimbrites and associated ash-fall layers. One ignimbrite records the ca. 8.1 Ma Castleford Crossing eruption, which was of supereruption magnitude ( 1900 km3). It covers 14,000 km2 and exceeds 1.35 km thickness within a subsided, proximal caldera-like depocenter. Majorand trace-element data define three successive temporal trends toward less-evolved rhyolitic compositions, separated by abrupt returns to more-evolved compositions. These cycles are thought to reflect increasing mantle- derived basaltic intraplating and hybridization of a midcrustal region, coupled with shallower fractionation in upper-crustal magma reservoirs. The onset of each new cycle is thought to record renewed intraplating at an adjacent region of crust, possibly as the North American plate migrated westward over the Yellowstone hotspot. A regional NE-trending monocline, here termed the Cassia monocline, was formed by synvolcanic deformation and subsidence of the intracontinental Snake River basin. Its structural and topographic evolution is reconstructed using thickness variations, offlap relations, and rheomorphic transport indicators in the successive dated ignimbrites. The subsidence is thought to have occurred in response to incremental loading and modification of the crust by the mantle-derived basaltic magmas. During this time, the area also underwent NW-trending faulting related to opening of the western Snake River rift and E-W Basin and Range extension. The large eruptions probably had different source locations, all within the subsiding basin. The proximal Miocene topography was thus in marked contrast to the more elevated present-day Yellowstone plateau. © 2016 Geological Society of America.
cited By 25
Keywords: Explosives; Geochronology; Subsidence; Trace elements; Explosive eruption; Explosive volcanism; Miocene topography; North american plates; Snake river plains; Thickness variation; Transport indicators; Yellowstone hotspot; Rivers; explosive volcanism; geochemistry; geochronology; mineralogy; Miocene; paleomagnetism; rhyolite; subsidence; hot spot; ignimbrite; trace element; volcanology; Idaho; Snake River Plain; United States; Wyoming; Yellowstone Caldera

Microstructures and their implications for faulting processes -Insights from DGLab core samples from the Gulf of Corinth - Janssen, C.; Wenk, H.-R.; Wirth, R.; Morales, L.; Kemnitz, H.; Sulem, J.; Dresen, G. (Journal of Structural Geology, 2016)
We have examined microstructures, mineralogical composition, geochemical alteration, and texture of four selected fault rock samples from the Deep Geodynamical Laboratory (DGLab) Gulf of Corinth project using optical microscopy, cathodoluminescence microscopy (CL), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and synchrotron X-ray diffraction measurements. The fault core is composed of red and gray clayey gouge material and surrounded by a damage zone of brecciated limestones. Pressure solution features, calcite veins and calcite clasts in the breccia and gouge material attest the presence of paleo-fluids and fluid-driven mass transfer during deformation. Differences in CL-colors between the matrix and calcite vein cement and inside the vein cement suggest repeated infiltration of fluids with different composition from various sources (formation water and meteoric water). Twin lamellae densities estimated in calcite veins are used as paleo-piezometer. The deduced differential stress is 140 ± 70 MPa for the older vein generation and appears to be higher than stress for the youngest veins (45 ± 23 MPa). In spite of the relatively small clay content in both samples, newly formed clay minerals have been observed in gray as well as red clayey gouge material. Differences between gray and red clay gouge material are found in fault rock composition, porosity and clay fabric. The proportion of chlorite in the red gouge is significantly less than that in the gray gouge whereas the initial porosity is significantly higher than in the gray gouge material. The detection of a well-oriented clay fabric in red clay gouge samples is unique in comparison to other major fault zones. © 2016 Elsevier Ltd.
Keywords: Gulf of Corinth; Ionian Sea; Mediterranean Sea; Calcite; Cements; Electron microscopy; High resolution transmission electron microscopy; Mass transfer; Microstructure; Porosity; Rocks; Scanning electron microscopy; Stainless steel; Transmission electron microscopy; X ray diffraction; Clay fabrics; Dissolution precipitations; EBSD; Fault rock; Fluid-rock interaction; Gulf of Corinth; Microstructure analysis; core analysis; deformation mechanism; dissolution; fault slip; fault zone; faulting; microstructure; precipitation (chemistry); stress field; water-rock interaction; Structural geology

Microseismic network design in complex 3D velocity models - Wuestefeld, A.; Kaschwich, T.; Iranpour, K. (SEG Technical Program Expanded Abstracts, 2016)
The demand on the versatility of microseismic monitoring networks is increasing rapidly. In early projects, being able to locate any triggers was considered a success. These early successes lead to a better understanding of how to extract value from microseismic results. Operators, regulators, and service providers must work closely together to find the optimum network design to meet various requirements. In this article we discuss three aspects that are of concern in the design phase of modern microseismic monitoring networks: 1) Detection Limits; 2) Location accuracy; 3) Ground-motion hazard. We determine the location error using both conventional phase-picking inversion scheme, and a novel method, based on Point Spread functions, to evaluate the accuracy migration-style location schemes. Using the well-documented example region around the San Andreas Fault Observatory at Depth (SAFOD) located north of Parkfield, California, we present several approaches to these sometimes competing requirements. Modelling these parameters prior to installation of a sensor network, helps to identify the potential challenges to meet the survey objectives and thus appropriate changes to the design can be implemented. We use the detailed velocity model of Thurber et al. (2004) which covers an area of 26.2x21.2km around the SAFOD drill site with a resolution of 200m for both P-and S-wave velocity (Figure 1). We are modelling the performance of several hypothetical sensor networks within the area. To highlight the importance of using the correct velocity model, we then compare these performance predictions with those for a simplistic 1D velocity model, commonly the only available source of velocity for hydraulic fracturing projects. © 2016 SEG.
cited By 0

Microbial sedimentary imprint on the deep Dead Sea sediment - Thomas, C.; Ebert, Y.; Kiro, Y.; Stein, M.; Ariztegui, D. (Depositional Record, 2016)
A study of an International Continental Drilling Program core recovered from the middle of the modern Dead Sea has identified microbial traces within this subsurface hypersaline environment. A comparison with an active microbial mat exhibiting similar evaporative processes characterized iron-sulphur mineralization and exopolymeric substances resulting from microbial activity. Exopolymeric substances were identified in the drilled sediment but unlike other hypersaline environments, it appears that they have a limited effect on the precipitation of calcium carbonate in the sedimentary column. Sulphate reduction, however, plays a role in all types of evaporative facies, leading to the formation of diagenetic iron sulphides in glacial and interglacial intervals. Their synthesis seems to occur under progressive sulphidation that generally stops at greigite because of incomplete sulphate reduction. The latter may be caused by a lack of suitable organic matter in this hypersaline, hence energy-demanding, environment. Pyrite may be found in periods of high lake productivity, when more labile organic matter is available. The carbon and sulphur cycles are thus influenced by microbial activity in the Dead Sea environment and this influence results in diagenetic transformations in the deep sediment. © 2016 The Authors. The Depositional Record published by John Wiley & Sons Ltd on behalf of International Association of Sedimentologists.
cited By 12

Methods for sampling and analysis of attached and planktonic microorganisms in deep granitic rock aquifers - Eriksson, Lena; Edlund, Johanna; Johansson, Linda; Rabe, Lisa; Bengtsson, Andreas; Pedersen, Karsten (SKB report R-16-09 p 61, 2016)

Seawater incursion event in Songliao Basin: New evidence from calcareous nannofossils of SK-1 - Cao, Wenxin; Xi, Dangpeng; Huang, Qinghua; Cheng, Yi; Qu, Haiying; Gao, Lianfeng; Wan, Xiaoqiao (Geological Bulletin of China, 2016)
The Songliao Basin is the largest non-marine oil-bearing basin in China. Due to the absence of sufficient evidence, the hypothesis of seawater incursion(s) into the Songliao Basin remains controversial. Marine fossil materials can provide direct explanations. More recently, a few calcareous nannofossils were discovered from units 1 and 2 of the Nenjiang Formation in drill hole SK-1. In these fossils, some taxa have been positively identified, namely Calculites obscurus, Calculites ovalis, Quadrum sp., and Micula sp. They were distributed in marine environment of the Cretaceous. Based on comparisons of the calcareous nannofossil assemblages from global records, the age of units 1 of the Nenjiang Formation seems to have spanned from the latest Turonian to Maastrichtian. The nannofossils from the Songliao Basin have the marine origin, characterized by common diversity and abundance. The distribution and paleoecology of the calcareous nannofossils as well as the co-existing foraminifera in the SK-1 provide further evidence for seawater incursion events in the Songliao Basin. The authors hold that periodical seawater incursion(s) brought calcareous nannofossils and foraminifera into the Songliao Basin during sedimentation of units 1 and 2 of the Nenjiang Formation, when both lake and sea were at high level. © 2016, Science Press. All right reserved.
Keywords: China; Nen Basin; Songliao Basin; Calculites (nannofossil); Foraminifera; Micula; abundance; Cretaceous; foraminifera; fossil assemblage; geological record; marine environment; nanofossil; paleoecology; seawater; sedimentation; species diversity

Megaspores attributable to Ghoshispora in Late Cretaceous deposits of the Songliao Basin, north-east China: Taxonomic clarification and distribution - Batten, D.J.; Li, J.; Peng, J. (Review of Palaeobotany and Palynology, 2016)
The composite SK-1 borehole drilled in the Songliao Basin, north-east China penetrated non-marine rocks of Late Cretaceous age, some of which yielded assemblages of Ghoshispora. Species of this megaspore genus have palaeoenvironmental and potentially also biostratigraphic significance. Their value as determinants of age is, however, currently limited because many are difficult if not impossible to differentiate as our appraisal of their morphological characters reveals. This review helped to put the specimens recovered from the SK-1 borehole into context and led to the identification of a few of the specimens as Ghoshispora kondinskayae (Srivastava et Binda) Srivastava, G. sp. cf. G. bella (Kondinskaya) subsp. deltoidea Kutluk et al., and G. sp. cf. G. rara (Kondinskaya) Srivastava. Several revealed characters under the scanning electron microscope that differ from those of previously published species: two of these are described as new, namely Ghoshispora zhaoi sp. nov. and G. bulbosa sp. nov. Owing to a lack of sufficient specimens six other morphotypes have had to be identified in open nomenclature as G. sp. A-F. It is likely that the parent plants of all of the species grew in and/or close to standing water. The comparatively large number of very small specimens in association with, and having some of the characters of, the larger representatives of G. zhaoi suggests that a few might be the microspores of this species rather than incompletely developed megaspores. © 2016 Elsevier B.V.
cited By 3
Keywords: biogenic deposit; biostratigraphy; Cretaceous; fern; fossil assemblage; geographical distribution; identification method; morphology; morphotype; nomenclature; paleoenvironment; palynology; scanning electron microscopy; spore; taxonomy; China; Songliao Basin

Scientific drilling projects in ancient lakes: Integrating geological and biological histories - Wilke, Thomas; Van Bocxlaer, Bert; Albrecht, Christian; Ariztegui, Daniel; Delicado, Diana; Francke, Alexander; Harzhauser, Mathias; Hauffe, Torsten; Holtvoeth, Jens; Just, Janna; Levkov, Zlatko; Penkman, Kirsty; et al. (Global and Planetary Change, 2016)
Sedimentary sequences in ancient or long-lived lakes can reach several thousands of meters in thickness and often provide an unrivalled perspective of the lake's regional climatic, environmental, and biological history. Over the last few years, deep-drilling projects in ancient lakes became increasingly multi- and interdisciplinary, as, among others, seismological, sedimentological, biogeochemical, climatic, environmental, paleontological, and evolutionary information can be obtained from sediment cores. However, these multi- and interdisciplinary projects pose several challenges. The scientists involved typically approach problems from different scientific perspectives and backgrounds, and setting up the program requires clear communication and the alignment of interests. One of the most challenging tasks, besides the actual drilling operation, is to link diverse datasets with varying resolution, data quality, and age uncertainties to answer interdisciplinary questions synthetically and coherently. These problems are especially relevant when secondary data, i.e., datasets obtained independently of the drilling operation, are incorporated in analyses. Nonetheless, the inclusion of secondary information, such as isotopic data from fossils found in outcrops or genetic data from extant species, may help to achieve synthetic answers. Recent technological and methodological advances in paleolimnology are likely to increase the possibilities of integrating secondary information. Some of the new approaches have started to revolutionize scientific drilling in ancient lakes, but at the same time, they also add a new layer of complexity to the generation and analysis of sediment-core data. The enhanced opportunities presented by new scientific approaches to study the paleolimnological history of these lakes, therefore, come at the expense of higher logistic, communication, and analytical efforts. Here we review types of data that can be obtained in ancient lake drilling projects and the analytical approaches that can be applied to empirically and statistically link diverse datasets to create an integrative perspective on geological and biological data. In doing so, we highlight strengths and potential weaknesses of new methods and analyses, and provide recommendations for future interdisciplinary deep-drilling projects. © 2016 Elsevier B.V.
Keywords: Biology; Geology; Paleolimnology; Analytical approach; Ancient lakes; Deep drilling; Evolutionary biology; Evolutionary information; Interdisciplinary project; Methodology; Sedimentary sequence; biological survey; core analysis; data quality; deep drilling; evolutionary biology; fossil record; geological theory; integrated approach; lacustrine environment; outcrop; paleolimnology; technological change; Lakes

The Campi Flegrei caldera (Italy): Formation and evolution in interplay with sea-level variations since the Campanian Ignimbrite eruption at 39 ka - Steinmann, Lena; Spiess, Volkhard; Sacchi, Marco (Journal of Volcanology and Geothermal Research, 2016)
To date, the origin of the Campi Flegrei caldera is still under debate and may be related to (1) a single caldera collapse associated with the Neapolitan Yellow Tuff (NYT) eruption, (2) two subsequent caldera collapses associated with the NYT and the preceding Campanian Ignimbrite (CI) eruptions forming a nested-caldera complex, or (3) not related to a caldera collapse after all. Here, we study the submerged portion of the caldera, which has favored a marine depositional setting and, thus, represents an ideal location for the reconstruction of its formation history, utilizing multichannel seismic data. Volcanic deposits and edifices were seismically distinguished from sedimentary successions, and the stratigraphy could be refined and extended back to the Campanian Ignimbrite eruption at 39 ka. High-resolution multichannel reflection seismic data revealed the existence of a nested-caldera complex formed during the CI eruption at 39 ka and the more recent NYT eruption at 15 ka. A ring-fault bounding an inner caldera collapse structure was clearly imaged. It appears that this inner ring-fault was initially activated during the CI caldera collapse and later reactivated during the NYT caldera collapse with different amounts of subsidence. The NYT caldera probably formed during an asymmetrical collapse with a maximum subsidence of 75 m in the offshore portion. The vertical displacement related to the CI caldera collapse may be significantly larger. The submerged caldera depression accommodates post-eruption sediments. Within this high-resolution archive, two major unconformities developed at 8.6 ka and 5 ka, when resurgence-related uplift exceeded the rate of sea-level rise concurrent with the emersion of the La Starza terrace. A previously unknown post-collapse submarine volcanic mound located between Nisida Island and Nisida Bank probably formed between 4.8 and 3.7 ka. Also, the Penta Palummo Bank appears to be constructed of at least two monogenetic volcanic edifices, the Penta Palummo volcano formed at 100 ka and a younger mushroom-shaped unit formed between 39 and 15 ka. The main outcome of this study is a conceptual evolutionary model, providing novel insights on the formation of the Campi Flegrei nested caldera in the course of two large-scale eruptions (CI and NYT) with associated caldera collapses along mutual (i.e. reactivated) faults and subsequent caldera resurgence. As both the genesis and subsurface architecture of the Campi Flegrei caldera are still hotly debated topics in literature, our discoveries can be regarded as a substantial advancement in the understanding of the Campi Flegrei volcanic area. © 2016 Elsevier B.V.
Keywords: Campania [Italy]; Campi Flegrei; Italy; Napoli [Campania]; Basidiomycota; Buildings; Seismic response; Seismic waves; Seismology; Stratigraphy; Subsidence; Volcanoes; Caldera formation; Caldera resurgence; Campi Flegrei; Fault system; Nested calderas; Reflection seismics; caldera; Campanian; collapse; formation mechanism; ignimbrite; landform evolution; sea level change; seismic reflection; volcanic eruption; Sea level

Sedimentary PGE signatures in the Late Triassic ejecta deposits from Japan: Implications for the identification of impactor - Sato, H.; Shirai, N.; Ebihara, M.; Onoue, T.; Kiyokawa, S. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2016)
Positive platinum group element (PGE) concentration and negative Os isotope anomalies reported from a claystone layer in the Upper Triassic bedded chert succession of the Sakahogi section, Mino Belt, central Japan, are thought to have been derived from an impact event. Stratigraphic variations and concentrations of PGE were examined in the Sakahogi section to determine the type of the impactor. Upper Triassic claystone layers, where PGE anomalies have been newly discovered in bedded chert successions in southwest Japan, were also examined. These include (i) the Unuma section in the Inuyama area, Mino Belt; (ii) the Hisuikyo section in the Kamiaso area, Mino Belt; and (iii) the Enoura section in the Tsukumi area, Chichibu Belt. Radiolarian and conodont biostratigraphic data indicate that these claystone layers are of upper-middle Norian age. Reconstruction of bedded chert in these sections suggests that they originate from open-ocean pelagic deep-sea sediments deposited in the Panthalassa Ocean.The relatively flat CI chondrite-normalized patterns of the least mobile PGEs (Ir, Ru, and Rh) and the Ru/Ir ratio determined by linear regression analysis suggest that a chondritic impactor is the source of the PGE anomalies preserved in claystone samples from the study sections. Although Ru/Ir ratios cannot conclusively distinguish chondrites from iron meteorites, the Cr/Ir ratios of the claystone layers range from 104 to 105, clearly indicating contribution from chondritic materials. The chondritic impactor of the suggested size (3.3-7.8km in diameter) implies that a large amount of debris and/or climatically active gasses (e.g., sulfur oxides) would have been released from the impactor, which would have had a marked effect on the environment. © 2015 Elsevier B.V.
cited By 8

The Campi Flegrei Deep Drilling Project (CFDDP): New insight on caldera structure, evolution and hazard implications for the Naples area (Southern Italy) - De Natale, Giuseppe; Troise, Claudia; Mark, Darren; Mormone, Angela; Piochi, Monica; Di Vito, Mauro A.; Isaia, Roberto; Carlino, Stefano; Barra, Diana; Somma, Renato (Geochemistry, Geophysics, Geosystems, 2016)
The 501 m deep hole of the Campi Flegrei Deep Drilling Project, located west of the Naples metropolitan area and inside the Campi Flegrei caldera, gives new insight to reconstruct the volcano-tectonic evolution of this highly populated volcano. It is one of the highest risk volcanic areas in the world, but its tectonic structure, eruptive history, and size of the largest eruptions are intensely debated in the literature. New stratigraphic and 40Ar/39Ar geochronological dating allow us to determine, for the first time, the age of intracaldera deposits belonging to the two highest magnitude caldera-forming eruptions (i.e., Campanian Ignimbrite, CI, 39 ka, and Neapolitan Yellow Tuff, NYT, 14.9 ka) and to estimate the amount of collapse. Tuffs from 439 m of depth yield the first 40Ar/39Ar age of ca. 39 ka within the caldera, consistent with the CI. Volcanic rocks from the NYT were, moreover, detected between 250 and 160 m. Our findings highlight: (i) a reduction of the area affected by caldera collapse, which appears to not include the city of Naples; (ii) a small volume of the infilling caldera deposits, particularly for the CI, and (iii) the need for reassessment of the collapse amounts and mechanisms related to larger eruptions. Our results also imply a revaluation of volcanic risk for the eastern caldera area, including the city of Naples. The results of this study point out that large calderas are characterized by complex collapse mechanisms and dynamics, whose understanding needs more robust constraints, which can be obtained from scientific drilling. © 2016. The Authors.
Keywords: Campania [Italy]; Campi Flegrei; Italy; Naples; Napoli [Campania]; Deposits; Geochronology; Hazards; Stratigraphy; Tectonics; Volcanic rocks; Caldera-forming eruption; Campanian Ignimbrite; Campi Flegrei; Collapse mechanism; Neapolitan yellow tuffs; Scientific drilling; Tectonic structure; Volcanic hazards; argon-argon dating; caldera; deep drilling; geochronology; reconstruction; tectonic evolution; volcanic eruption; Volcanoes

Mass wasting history within Lake Ohrid basin (Albania/Macedonia) over the last 600 ka - Baumgarten, H. (Advances in Natural and Technological Hazards Research, 2016)
Lake Ohrid (LO), a transboundary lake shared by Macedonia and Albania on the Balkan Peninsula, is not only considered to be the oldest lake in Europe ( 2 Ma) but has a long and continuous sedimentary history. An advantage at LO is the availability of hydroacoustic data sets of good quality covering the entire lake basin. The tectonically formed basin is filled with thick undisturbed sediments. However, the overall internal structure of LO is characterized by numerous faults, clinoform structures, and several Mass Transport Deposits (MTDs). By using a seismic chronology model (SCM) correlating seismic reflector packages with Marine Isotope Stages (MIS) we estimate the occurrence of the deepest MTD detected in the southern basin at the transition of MIS9 to MIS8 ( 300 ka) defining the onset of the sliding history in LO that is still ongoing today. In general, MTDs are widespread within the basin but they do cluster at active faults. Two large MTDs occurred in the early MIS7 ( 230 ka, 220 ka) and after a quiesence period of about 70 ka two additional large MTDs have been detected in the late penultimate glacial period MIS6 ( 150 ka, 130 ka). MIS5 seemed to be another quiet period with respect to mass wasting. In the younger sedimentary history mass movement is a common process with several large and mid-sized deposits mapped at all stratigraphic levels. The youngest slide deposits are estimated to occur within the last 2,000 years. The main outcome of this paper is a model for the spatial and temporal distribution of mass wasting for Lake Ohrid. © Springer International Publishing Switzerland 2016.
cited By 2

Wellbore and groundwater temperature distribution eastern Snake River Plain, Idaho: Implications for groundwater flow and geothermal potential - McLing, T.L.; Smith, R.P.; Smith, R.W.; Blackwell, D.D.; Roback, R.C.; Sondrup, A.J. (Journal of Volcanology and Geothermal Research, 2016)
A map of groundwater temperatures from the Eastern Snake River Plain (ESRP) regional aquifer can be used to identify and interpret important features of the aquifer, including aquifer flow direction, aquifer thickness, and potential geothermal anomalies. The ESRP is an area of high heat flow, yet most of this thermal energy fails to reach the surface, due to the heat being swept downgradient by the aquifer to the major spring complexes near Thousand Springs, ID, a distance of 300 km. Nine deep boreholes that fully penetrate the regional aquifer display three common features: (1) high thermal gradients beneath the aquifer, corresponding to high conductive heat flow in low-permeability hydrothermally-altered rocks; (2) isothermal temperature profiles within the aquifer, characteristic of an actively flowing groundwater; and (3) moderate thermal gradients in the vadose zone with values that indicate that over half of the geothermal heat flow is removed by advective transport in the regional aquifer system. This study utilized temperature data from 250 ESRP aquifer wells to evaluate regional aquifer flow direction, aquifer thickness, and potential geothermal anomalies. Because the thermal gradients are typically low in the aquifer, any measurement of groundwater temperature is a reasonable estimate of temperature throughout the aquifer thickness, allowing the construction of a regional aquifer temperature map for the ESRP. Mapped temperatures are used to identify cold thermal plumes associated with recharge from tributary valleys and adjacent uplands, and warm zones associated with geothermal input to the aquifer. Warm zones in the aquifer can have various causes, including local circulation of groundwater through the deep conductively dominated region, slow groundwater movement in low-permeability regions, or localized heat flow from deeper thermal features. © 2015 Elsevier B.V.
cited By 9
Keywords: Aquifers; Boreholes; Geothermal energy; Geothermal heating; Groundwater; Groundwater flow; Heat transfer; Rivers; Temperature distribution; Thermal gradients; Advective transport; Geothermal potential; Ground water movement; Groundwater temperatures; Hydrothermally altered rocks; Isothermal temperature; Snake river plains; Thermal groundwater; Groundwater resources; aquifer; flow modeling; groundwater; heat flow; permeability; temperature profile; tracer; Idaho; Snake River Plain; United States; Calluna vulgaris

Using palynology to re-assess the Dead Sea laminated sediments - Indeed varves? - L'opez-Merino, L.; Leroy, S.A.G.; Eshel, A.; Epshtein, V.; Belmaker, R.; Bookman, R. (Quaternary Science Reviews, 2016)
Lacustrine laminated sediments are often varves representing annual rhythmic deposition. The Dead Sea high-stand laminated sections consist of mm-scale alternating detrital and authigenic aragonite laminae. Previous studies assumed these laminae were varves deposited seasonally. However, this assumption has never been robustly validated. Here we report an examination of the seasonal deposition of detrital-aragonite couplets from two well-known Late Holocene laminated sections at the Ze'elim fan-delta using palynology and grain-size distribution analyses. These analyses are complemented by the study of contemporary flash-flood samples and multivariate statistical analysis. Because transport affects the pollen preservation state, well-preserved (mostly) air-borne transported pollen was analysed separately from badly-preserved pollen and fungal spores, which are more indicative of water transport and reworking from soils. Our results indicate that (i) both detrital and aragonite laminae were deposited during the rainy season; (ii) aragonite laminae have significantly lower reworked and fungal spore concentrations than detrital and flash-flood samples; and (iii) detrital laminae are composed of recycling of local and distal sources, with coarser particles that were initially deposited in the Dead Sea watershed and later transported via run-off to the lake. This is in line with previous carbon balance studies that showed that aragonite precipitation occurs after the massive input of TCO2 associated with run-off episodes. Consequently, at least for the Holocene Ze'elim Formation, laminated sediments cannot be considered as varves. Older Quaternary laminated sequences should be re-evaluated. © 2016 The Authors.
cited By 21
Keywords: Deposition; Floods; Fungi; Grain size and shape; Multivariant analysis; Particle size analysis; Seawater; Sediments; Air borne; Aragonite; Dead sea; Flash flood; Laminated sediments; Reworked pollen; Carbonate minerals; aragonite; carbon balance; flash flood; fungus; Holocene; lacustrine deposit; lamination; palynology; reworking; runoff; spore; varve; watershed; Dead Sea

Using distributions and stable isotopes of n-alkanes to disentangle organic matter contributions to sediments of Laguna Potrok Aike, Argentina - Hockun, Katja; Mollenhauer, Gesine; Ho, Sze Ling; Hefter, Jens; Ohlendorf, Christian; Zolitschka, Bernd; Mayr, Christoph; L{ucke, Andreas; Schefu{s, Enno (Organic Geochemistry, 2016)
When using biomarkers such as n-alkanes as tools for paleo-environmental reconstructions, it is imperative to determine their specific sources for each setting. Toward that goal, we analyzed a set of various potential organic matter (OM) sources such as aquatic and terrestrial plants, dust, and soils from Laguna Potrok Aike (LPA) and surrounding areas in southern Patagonia. We determined chain length distributions and hydrogen (δD) and carbon (δ13C) isotopic compositions of n-alkanes of different OM sources in order to quantify their relative contributions to lake sediments. Our results reveal that the mid-chain n-alkane, n-C23, is predominantly produced by submerged aquatic plants, whereas long-chain n-alkanes (n-C29 –n-C31) are derived from various terrestrial sources. We estimated their relative contributions to the sediment using two approaches, i.e., based on the n-alkane distributions and their δD and δ13C values. Both approaches result in similar estimates of aquatic and terrestrial contributions for mid- and long-chain n-alkanes to the sediment. 62 –73% of the mid-chain n-C23 alkanes originate from aquatic sources while 66 –77% of the long-chain n-alkanes originate from dust and 14 –30% from terrestrial plants. Our study shows that mid-chain n-alkanes such as the n-C23 alkane in LPA are derived mainly from aquatic macrophytes and thus have the potential to record changes in lake-water isotopic composition. In contrast, the n-C29 alkane reflects the isotopic signal of various terrestrial sources from southern Patagonia. © 2016 Elsevier Ltd
Keywords: Argentina; Laguna Potrok Aike; Patagonia; Santa Cruz [Argentina]; Biogeochemistry; Biological materials; Chains; Dust; Isotopes; Lakes; Sediments; Chain length distribution; Environmental reconstruction; ICDP; Isotopic composition; Long chain n-alkanes; n-Alkanes; PASADO; Relative contribution; alkane; biomarker; carbon isotope; hydrogen isotope; isotopic composition; lacustrine deposit; macrophyte; organic matter; paleoenvironment; reconstruction; sediment chemistry; spatial distribution; stable isotope; submerged vegetation; Paraffins

Unusual, basin-scale, fluid –rock interaction in the Palaeoproterozoic Onega basin from Fennoscandia: Preservation in calcite δ18O of an ancient high geothermal gradient - Fallick, A.E.; Melezhik, V.A.; Brasier, A.T.; Prave, A.R. (Precambrian Research, 2016)
A variety of carbonates of different geneses, as indicated by petrography and geochemistry, are found throughout 400 m of the volcano-sedimentary rocks of the Zaonega Formation of Palaeoproterozoic age in the Onega basin of Fennoscandia. Following intensive sampling and analysis of varied calcites from drillcore recovered during the ICDP FAR-DEEP program, we report a highly unusual depth distribution of calcite oxygen isotope values (δ18Ocal). Unprecedentedly for such rocks, the δ18Ocal values over the full depth interval of 400 m are strongly linearly correlated with depth (r2 = 0.9015, n = 178). We propose that this is the result of major oxygen isotope resetting through water –rock interaction with a fluid of relatively constant oxygen isotopic composition (δ18Ow). In this model, the observed linear δ18Ocal-depth relationship is then a consequence of the increase in temperature with depth because of the background geothermal gradient. Minor deviations from the overall linear trend are likely due to bed-scale geological factors including locally high impermeability, and oxygen isotope modification of δ18Ow by comparatively intense water –rock interaction. Were the observed δ18Ocal values to have been reset during the greenschist facies Svecofennian metamorphism which affected the rocks at c. 1800 Ma, the implied geothermal gradient of ∼560 °C km−1 is geologically unreasonable and, accordingly, this hypothesis is ruled out. Rather, the δ18Ocal variation of 5‰ over 400 m implies a near-surface depth for the rocks during fluid interaction, and this is consistent with a surface-derived origin of the infiltrating fluid (δ18Ow ∼−13.6‰ for a surface temperature of 15 °C and geothermal gradient of ∼52 °C km−1). It is speculated that the fluid accessed the carbonates from the basin edge by bed-parallel rather than cross-formational flow. There is an intriguing distribution of Na in the sedimentary rocks of the Zaonega Formation. Sodium is relatively abundant in rocks below a certain depth (the lowermost dolostone at ∼258 m), but rare in shallower sequences. It is argued that this distribution did not originate with the basin-scale fluid –rock interaction documented above, but may rather be the result of evaporite dissolution, and subsequent redistribution of soluble elements during fluid flow associated with the syndepositional emplacement of basin-wide igneous rocks. © 2016 Elsevier B.V.
Keywords: calcite; carbonate; diagenesis; geothermal gradient; oxygen isotope; Proterozoic; water-rock interaction; Arkhangelsk [Russian Federation]; Fennoscandia; Onega Basin; Russian Federation

Two new fossil Cyclotella (K{utzing) Br'ebBisson species from Lake Ohrid, Macedonia/Albania - Tofilovska, Slavica; Cvetkoska, Aleksandra; Jovanovska, Elena; Ognjanova-Rumenova, Nadja; Levkov, Zlatko (Fottea, 2016)
Lake Ohrid is the oldest existing lake in Europe and it is known for its high diversity with around 200 endemic or relict diatom species recognized. In order to understand this phenomenon, a large project on deep drilling was performed and a core with maximum sediment depth of 569 m which spans > 1.2 million years was recovered. Two new species of Cyclotella were discovered in the core samples, which are described here as Cyclotella cavitata sp. nov. and Cyclotella sollevata sp. nov. The species have been studied with light and scanning electron microscopes, their morphological features and their relevance to other members of the genus Cyclotella are discussed. Cyclotella cavitata sp. nov. is characterized by round to elliptical shape; elliptic and tangentially undulate central area with one to three papillae on the elevated side. Central fultoportulae are absent while marginal fultoportulae internally are located on slightly depressed costae, with short tube openings with two satellite pores surrounded by cowlings. Satellite pores are situated circumferentially. Internally the rimoportula is situated in the marginal area with a sessile labium. Cyclotella sollevata sp. nov. is characterized by round valves with convex or concave central area which is uneven, colliculate, with papillae and granules. Central fultoportulae are present with variable number (9-21), internally with short tube openings with two satellite pores, which are surrounded by cowlings; Internally marginal fultoportulae are located on depressed costae and have short tube openings with two satellite pores situated circumferentially, surrounded by cowlings. The rimoportulae are located in the marginal area with a sessile labium variably orientated. Cyclotella sollevata and Cyclotella cavitata have been observed only in the fossil sediments of Lake Ohrid. Comments on the position of rimoportula, used as synapomorphic character to separate Lindavia from Cyclotella sensu lato are provided. © Czech Phycological Society (2016).

Three novel species of bacillariophyta (Diatoms) belonging to aulacoseira and lindavia from the pliocene hadar formation, afar depression of Ethiopia - Mohan, Joseph; Stone, Jeffery R.; Campisano, Christopher J. (Phytotaxa, 2016)
Paleolake Hadar was an expansive lake in the lower Awash Valley of Ethiopia’s Afar Depression that existed periodically through the Late Pliocene. The sedimentary deposits from this ancient lake (Hadar Formation) have broad importance because a significant number of hominin fossils have been recovered from the formation. Samples of the Hadar Formation lacustrine sequence were collected from sediment cores extracted as part of the Hominin Sites and Paleolakes Drilling Project (HSPDP). A paleoecological study of the HSPDP Northern Awash (Hadar Formation) material has unearthed three novel species of Bacillariophyta (diatoms) from diatomites that appear periodically in the cores. The Hadar Formation assemblage represents a newly revealed excerpt from the evolutionary history of freshwater diatoms in East Africa during the Piacenᴢian age (2.59-3.60 Ma). The HSPDP Northern Awash diatom species are compared to previously reported diatoms from Pliocene outcrops, modern and fossil core material from Lake Malawi, and extant species. Here we describe two new species of Aulacoseira and one of Lindavia. Taxonomic treatment of two diatom varieties reported by previous researchers as Melosira are transferred into Aulacoseira herein. © 2016 Magnolia Press.

The water retention curve and relative permeability for gas production from hydrate-bearing sediments: pore-network model simulation - Mahabadi, N.; Dai, S.; Seol, Y.; Sup Yun, T.; Jang, J. (Geochemistry, Geophysics, Geosystems, 2016)
The water retention curve and relative permeability are critical to predict gas and water production from hydrate-bearing sediments. However, values for key parameters that characterize gas and water flows during hydrate dissociation have not been identified due to experimental challenges. This study utilizes the combined techniques of micro-focus X-ray computed tomography (CT) and pore-network model simulation to identify proper values for those key parameters, such as gas entry pressure, residual water saturation, and curve fitting values. Hydrates with various saturation and morphology are realized in the pore-network that was extracted from micron-resolution CT images of sediments recovered from the hydrate deposit at the Mallik site, and then the processes of gas invasion, hydrate dissociation, gas expansion, and gas and water permeability are simulated. Results show that greater hydrate saturation in sediments lead to higher gas entry pressure, higher residual water saturation, and steeper water retention curve. An increase in hydrate saturation decreases gas permeability but has marginal effects on water permeability in sediments with uniformly distributed hydrate. Hydrate morphology has more significant impacts than hydrate saturation on relative permeability. Sediments with heterogeneously distributed hydrate tend to result in lower residual water saturation and higher gas and water permeability. In this sense, the Brooks-Corey model that uses two fitting parameters individually for gas and water permeability properly capture the effect of hydrate saturation and morphology on gas and water flows in hydrate-bearing sediments. © 2016. American Geophysical Union. All Rights Reserved.
cited By 114
Keywords: Computerized tomography; Curve fitting; Dissociation; Flow of water; Gas permeability; Gases; Hydration; Hydraulics; Morphology; Sediments; Brooks-Corey model; Hydrate bearing sediments; Pore-network modeling; Relative permeability; Van Genuchten model; Water retention curve; Gas hydrates; gas hydrate; gas production; hydrocarbon reservoir; numerical model; permeability; porosity; water retention

The Sr-isotopic stratigraphy of the northern limb of the Bushveld Complex, South Africa - Mangwegape, Mpho; Roelofse, Frederick; Mock, Timothy; Carlson, Richard W (Journal of African Earth Sciences, 2016)

The Lawn Hill annulus: An Ordovician meteorite impact into water-saturated dolomite - Darlington, V.; Blenkinsop, T.; Dirks, P.; Salisbury, J.; Tomkins, A. (Meteoritics and Planetary Science, 2016)
The Lawn Hill Impact Structure (LHIS) is located 250 km N of Mt Isa in NW Queensland, Australia, and is marked by a highly deformed dolomite annulus with an outer diameter of 18 km, overlying low metamorphic grade siltstone, sandstone, and shale, along the NE margin of the Georgina Basin. This study provides detailed field observations from sections of the Lawn Hill annulus and adjacent areas that demonstrate a clear link between the deformation of the dolomite and the Lawn Hill impact. 40Ar-39Ar dating of impact-related melt particles provides a time of impact in the Ordovician (472 ± 8 Ma) when the Georgina Basin was an active depocenter. The timing and stratigraphic thickness of the dolomite sequence in the annulus suggest that there was possibly up to 300 m of additional sedimentary rocks on top of the currently exposed Thorntonia Limestone at the time of impact. The exposed annulus is remarkably well preserved, with preservation attributed to postimpact sedimentation. The LHIS has an atypical crater morphology with no central uplift. The heterogeneous target materials at Lawn Hill were probably low-strength, porous, and water-saturated, with all three properties affecting the crater morphology. The water-saturated nature of the carbonate unit at the time of impact is thought to have influenced the highly brecciated nature of the annulus, and restricted melt production. The impact timing raises the possibility that the Lawn Hill structure may be a member of a group of impacts resulting from an asteroid breakup that occurred in the mid-Ordovician (470 ± 6 Ma). © The Meteoritical Society, 2016.
cited By 13

The Hominin Sites and Paleolakes Drilling Project: Inferring the environmental context of human evolution from eastern African rift lake deposits - Cohen, A.; Campisano, C.; Arrowsmith, R.; Asrat, A.; Behrensmeyer, A.K.; Deino, A.; Feibel, C.; Hill, A.; Johnson, R.; Kingston, J.; Lamb, H.; Lowenstein, T.; et al. (Scientific Drilling, 2016)
The role that climate and environmental history may have played in influencing human evolution has been the focus of considerable interest and controversy among paleoanthropologists for decades. Prior attempts to understand the environmental history side of this equation have centered around the study of outcrop sediments and fossils adjacent to where fossil hominins (ancestors or close relatives of modern humans) are found, or from the study of deep sea drill cores. However, outcrop sediments are often highly weathered and thus are unsuitable for some types of paleoclimatic records, and deep sea core records come from long distances away from the actual fossil and stone tool remains. The Hominin Sites and Paleolakes Drilling Project (HSPDP) was developed to address these issues. The project has focused its efforts on the eastern African Rift Valley, where much of the evidence for early hominins has been recovered.We have collected about 2 km of sediment drill core from six basins in Kenya and Ethiopia, in lake deposits immediately adjacent to important fossil hominin and archaeological sites. Collectively these cores cover in time many of the key transitions and critical intervals in human evolutionary history over the last 4 Ma, such as the earliest stone tools, the origin of our own genus Homo, and the earliest anatomically modern Homo sapiens. Here we document the initial field, physical property, and core description results of the 2012-2014 HSPDP coring campaign. © Author(s) 2016.
Keywords: Core drilling; Deposits; Drills; Environmental protection; Lakes; Sediments; Archaeological site; Drilling projects; Environmental contexts; Environmental history; Evolutionary history; Human evolution; Lake deposits; Paleoclimatic record; Deepwater drilling

The fluid budget of a continental plate boundary fault: Quantification from the Alpine Fault, New Zealand - Menzies, C.D.; Teagle, D.A.H.; Niedermann, S.; Cox, S.C.; Craw, D.; Zimmer, M.; Cooper, M.J.; Erzinger, J. (Earth and Planetary Science Letters, 2016)
Fluids play a key role in modifying the chemical and physical properties of fault zones, which may prime them for repeated rupture by the generation of high pore fluid pressures and precipitation of commonly weak, secondary minerals. Fluid flow paths, sources and fluxes, and the permeability evolution of fault zones throughout their seismic cycles remain poorly constrained, despite their importance to understanding fault zone behaviour. Here we use geochemical tracers of fluid-rock exchange to determine budgets for meteoric, metamorphic and mantle fluids on a major compressional tectonic plate boundary.The Alpine Fault marks the transpressional Pacific-Australian plate boundary through South Island, New Zealand and appears to fail in regular (329±68 yrs) large earthquakes (Mw 8) with the most recent event in 1717 AD. Significant convergent motion has formed the Southern Alps and elevated geothermal gradients in the hangingwall, which drive crustal fluid flow. Along the Alpine Fault the Alpine Schist of the Pacific Plate is thrust over radiogenic metasedimentary rocks on the Australian plate. The absence of highly radiogenic (87Sr/86Sr > 0.7200) strontium isotope ratios of hangingwall hot springs and hydrothermal minerals formed at a range of depths in the Alpine Fault damage zone indicates that the fluid flow is restricted to the hangingwall by a cross-fault fluid flow barrier throughout the seismogenic crust. Helium isotope ratios measured in hot springs near to the Alpine Fault (0.15-0.81 RA) indicate the fault is a crustal-scale feature that acts as a conduit for fluids from the mantle. Rock-exchanged oxygen, but meteoric water-like hydrogen isotope signatures of hydrothermal veins indicate that partially rock-exchanged meteoric fluids dominate down to the top of the brittle to ductile transition zone at ∼6 km. Geochemical tracer transport modelling suggests only ∼0.02 to 0.05% of total rainfall west of the Main Divide penetrates to depth, yet this recharge flux is sufficient to overwhelm other fluid contributions. Calculated mantle fluid fluxes of CO2 and H2O (0.2 and 3 to 13 mol/m2/yr respectively) and metamorphic H2O fluxes (4 to 750 mol/m2/yr) are considerably lower than the focused meteoric water discharge flux up the Alpine Fault (4 × 103 to 7 × 104 mol/m2/yr), driven by the >3000 m hydrologic head of the Southern Alps. Meteoric waters are primarily responsible for modifying fault zone permeability during fluid-rock interactions and may facilitate the generation of high pore fluid pressures that could assist episodic earthquake rupture. © 2016 The Authors.
cited By 38
Keywords: Budget control; Carbon dioxide; Earthquakes; Faulting; Flow of fluids; Geochemistry; Geochronology; Geophysics; Helium; Hot springs; Isotopes; Metamorphic rocks; Rocks; Alpine Faults; Fault seal; Fluid fluxes; Helium isotopes; Mantle CO2; Meteoric waters; Transport properties; carbon dioxide; earthquake magnitude; earthquake rupture; fault zone; helium isotope; mantle source; meteoric water; Pacific plate; permeability; plate boundary; Alpine Fault Zone; New Zealand; South Island

The coupled 182W-142Nd record of early terrestrial mantle differentiation - Puchtel, Igor S.; Blichert-Toft, Janne; Touboul, Mathieu; Horan, Mary F.; Walker, Richard J. (Geochemistry, Geophysics, Geosystems, 2016)

Tenoumer impact crater, Mauritania: Impact melt genesis from a lithologically diverse target - Schultze, D.S.; Jourdan, F.; Hecht, L.; Reimold, W.U.; Schmitt, R.-T. (Meteoritics and Planetary Science, 2016)
Impact melt rocks from the 1.9 km diameter, simple bowl-shaped Tenoumer impact crater in Mauritania have been analyzed chemically and petrologically. They are heterogeneous and can be subdivided into three types based on melt matrix color, occurrence of lithic clast components, amount of vesiculation (melt degassing), different proportions of carbonate melt mingled into silicate melt, and bulk rock chemical composition. These heterogeneities have two main causes (1) due to the small size of the impact crater, there was probably no coherent melt pool where a homogeneous mixture of melts, derived from different target lithologies, could be created; and (2) melt rock heterogeneity occurring at the thin section scale is due to fast cooling during and after the dynamic ejection and emplacement process. The overall period of crystal growth from these diverse melts was extremely short, which provides a further indication that complete chemical equilibration of the phases could not be achieved in such short time. Melt mixing processes involved in the generation of impact melts are, thus, recorded in nonequilibrium growth features. Variable mixing processes between chemically different melt phases and the formation of hybrid melts can be observed even at millimeter scales. Due to extreme cooling rates, different mixing and mingling stages are preserved in the varied parageneses of matrix minerals and in the mineral chemistry of microlites. 40Ar39Ar step-heating chronology on specimens from three melt rock samples yielded five concordant inverse isochron ages. The inverse isochron plots show that minute amounts of inherited 40Ar* are present in the system. We calculated a weighted mean age of 1.57 ± 0.14 Ma for these new results. This preferred age represents a refinement from the previous range of 21 ka to 2.5 Ma ages based on K/Ar and fission track dating. © 2016 The Meteoritical Society.
cited By 12

Sedimentological processes and environmental variability at Lake Ohrid (Macedonia, Albania) between 637 ka and the present - Francke, Alexander; Wagner, Bernd; Just, Janna; Leicher, Niklas; Gromig, Raphael; Baumgarten, Henrike; Vogel, Hendrik; Lacey, Jack H.; Sadori, Laura; Wonik, Thomas; Leng, Melanie J.; Zanchetta, Giovanni; et al. (Biogeosciences, 2016)
Lake Ohrid (Macedonia, Albania) is thought to be more than 1.2 million years old and host more than 300 endemic species. As a target of the International Continental scientific Drilling Program (ICDP), a successful deep drilling campaign was carried out within the scope of the Scientific Collaboration on Past Speciation Conditions in Lake Ohrid (SCOPSCO) project in 2013. Here, we present lithological, sedimentological, and (bio-)geochemical data from the upper 247.8 m composite depth of the overall 569 m long DEEP site sediment succession from the central part of the lake. According to an age model, which is based on 11 tephra layers (first-order tie points) and on tuning of bio-geochemical proxy data to orbital parameters (second-order tie points), the analyzed sediment sequence covers the last 637 kyr. The DEEP site sediment succession consists of hemipelagic sediments, which are interspersed by several tephra layers and infrequent, thin (< 5 cm) mass wasting deposits. The hemipelagic sediments can be classified into three different lithotypes. Lithotype 1 and 2 deposits comprise calcareous and slightly calcareous silty clay and are predominantly attributed to interglacial periods with high primary productivity in the lake during summer and reduced mixing during winter. The data suggest that high ion and nutrient concentrations in the lake water promoted calcite precipitation and diatom growth in the epilimnion during MIS15, 13, and 5. Following a strong primary productivity, highest interglacial temperatures can be reported for marine isotope stages (MIS) 11 and 5, whereas MIS15, 13, 9, and 7 were comparably cooler. Lithotype 3 deposits consist of clastic, silty clayey material and predominantly represent glacial periods with low primary productivity during summer and longer and intensified mixing during winter. The data imply that the most severe glacial conditions at Lake Ohrid persisted during MIS16, 12, 10, and 6, whereas somewhat warmer temperatures can be inferred for MIS14, 8, 4, and 2. Interglacial-like conditions occurred during parts of MIS14 and 8. © Author(s) 2016.
Keywords: Albania; Greece; Lake Ohrid; Macedonia [Greece]; Bacillariophyta; calcite; deep drilling; diatom; endemic species; epilimnion; geochemistry; lacustrine environment; lithotype; marine isotope stage; pelagic deposit; precipitation (chemistry); primary production; seasonal variation; silty clay; tephra

Tectonics and cycle system of the Cretaceous Songliao Basin: An inverted active continental margin basin - Wang, P.-J.; Mattern, F.; Didenko, N.A.; Zhu, D.-F.; Singer, B.; Sun, X.-M. (Earth-Science Reviews, 2016)
Recent ICDP drilling and deep basin volcanic exploration of 3000 m below the surface in the Songliao Basin (SB) have highlighted the 3-D delineation of the basin. The integrated new data led us to reevaluate the basin tectonics, for which the basin type, basin evolution and a number of geodynamic aspects have been controversial topics. We outline the position of a main lithospheric scale detachment fault beneath the SB, based on apparent crustal scale displacements, Moho breaks, the thinning of the Moho transition zone beneath the SB and the changing mantle thickness. This fault interpretation is consistent with simple shear as the rift mechanism. Based on a comprehensive analysis of the tectonic setting, underlying crust, structural style, sequence stratigraphy, subsidence history and volcanism, we propose an active continental margin model for the SB which shows some similarities to aulacogens but also notable differences. Situated between two Late Mesozoic active continental margins, the northern/northwestern Mongol-Okhotsk and the eastern Sikhote-Alin orogenic belts, the Cretaceous basin evolved on a pre-Triassic structurally weak basement mosaic. Its development began with regional mega-rifting from 150 to 105 Ma, followed by significant sagging between 105 and 79.1 Ma and ended with regional uplift and basin inversion from 79.1 to 64 Ma. Three regional angular unconformities separate the basin fill into three respective tectono-stratigraphic sequences. (1) The syn-rift stage is characterized by widespread fault-bounded grabens and volcanogenic successions, corresponding upward to the Huoshiling, Shahezi and Yingcheng Formations. (2) The post-rift stage includes the Denglouku, Quantou, Qignshankou, Yaojia and Nenjiang Formations. It is a special feature that the subsidence rate is abnormally high (mean of 103 m/Ma), and that flood basalt erupted along an axial wrench fault zone, associated with several marine intervals from the mid-Turonian to early Campanian (K2qn to K2n), possibly (not certainly) indicating incipient sea floor spreading characterized by Moho breaks along the basin axis in the SB around 88 Ma. Stretching stopped abruptly at approximately 79.1 Ma and was followed by uplift and rapid erosion (-145 m/Ma). (3) Recorded by the Sifangtai and Mingshui Formations the structural inversion stage included a continuous depocenter migration to the northwest. The basin was shrinking to demise as a result of changing subduction parameters of the Pacific subduction zone. In addition to the three tectonic basin cycles, a cyclic basin fill pattern exists with three volcanic basin fill intervals of Huoshiling, Yingcheng, and upper Qingshankou Formations that alternate with sedimentary basin fill intervals of Shahezi, Dengloukou-Quantou, and Yaojia-Nenjiang Formations.When determining the subsidence rates, we observed not only anomalously fast subsidence but also found an intricate link between the subsidence rate and type of basin fill. After each volcanic interval, the subsidence rates increased in a cyclic fashion during the sedimentary intervals. Thus, there is a system of three different types of important, basin-wide geological cycles that controlled the evolution of the SB. The subsidence rate was especially high (up to 199 m/Ma) after the last volcanic episode at 88 Ma. In addition to thermal subsidence and loading by the basin fill as causative processes, we also consider magmatic processes related to asthenospheric upwelling beneath the SB. They involve the roof collapse of shallow, depleted magma chambers, the igneous accretion of initially hot, dense, basic rocks, and lithospheric delamination beneath the SB. The difference in the subsidence rates during the volcanic and sedimentary intervals may in part also have been due to heating-related uplift during the volcanic intervals. The particularly high subsidence during the Late Cretaceous sedimentary cycles was partly increased by transtension. We put forward a general model for active continental margin basins. They are generally similar to aulacogens but display the following differences. In active continental margin basins, rifting depends on the subduction parameters that may cause strong to mild extension in the giant marginal region. The geochemical composition of the volcanic rocks is more calc-alkaline in nature because they are suprasubduction-related. These basins will eventually enter a post-rift sag stage that involves thermal subsidence. However, the basin will still be near an active continental margin, and, thus, some dip- and/or strike-slip faulting may occur coevally, depending on the subduction parameters. Sag cycles in active continental margin basins will likely include volcanism. Basin inversion will after all affect active continental margin basins. Such basins strike parallel to the respective continental margin. Thus, basin inversion by subduction/collision may be more intense than in the case of aulacogens, which do not tend to strike parallel to the continental margin. Basin inversion may also precede a collision due to changing subduction parameters. Subsidence behavior may also differ because many aspects of subsidence may be at work. Subsidence curves in active continental margin basins may be fairly individual. The application of our model only requires settings with the presence of one Pacific margin type. © 2016 The Authors.
cited By 149
Keywords: collision zone; continental margin; detachment fault; Moho; Pacific plate; rift zone; subduction; tectonic evolution; tectonic setting; three-dimensional modeling; transition zone; China; Songliao Basin

Sulphur tales from the early Archean world - Montinaro, A.; Strauss, H. (International Journal of Astrobiology, 2016)
Sedimentary and magmatic rocks and their distinct sulphur isotopic signatures indicate the sources and processes of sulphur cycling, in particular through the analysis of all four stable sulphur isotopes (32S, 33S, 34S and 36S). Research over the past 15 years has substantially advanced our understanding of sulphur cycling on the early Earth, most notably through the discovery of mass-independently fractionated sulphur isotopic signatures. A strong atmospheric influence on the early Archean global sulphur cycle is apparent, much in contrast to the modern world. Diverse microbially driven sulphur cycling is clearly discernible, but its importance for Earth surface environments remains to be quantified. © 2016 Cambridge University Press.
Keywords: Archean; magma; pyrite; sedimentary rock; stable isotope; sulfate; sulfur cycle; sulfur isotope

Structural modeling of the casings in the IDDP-1 well: Load history analysis - Kaldal, G.S.; Jonsson, M.T.; Palsson, H.; Karlsdottir, S.N. (Geothermics, 2016)
Flow testing of IDDP-1, the first Icelandic Deep Drilling Project (IDDP) well drilled in the Krafla geothermal field in Iceland, demonstrated promising results by producing superheated steam. During an unavoidable quenching of the well the innermost casing failed presumably due to tensile stresses caused by thermal contraction. Since the structural integrity of casings is essential for utilization of high temperature geothermal wells, the well has not been discharged again. In this paper, the casings of the well are analyzed structurally with a nonlinear finite-element model. The load history of the casings is followed from installation and through several thermal cycles, but the well was discharged at least six times before it was quenched with cold water. The results show that changes in stiffness due to the presence of casing shoes and changes in casing thickness have an effect on the stress and strain formations in neighboring casings. The results illustrate that during each thermal cycle, the wellbore thermal load is more severe for the production casing than for the external casings that are somewhat protected, provided that cementing in between is adequate. © 2016 Elsevier Ltd.
cited By 14
Keywords: Geothermal fields; Geothermal wells; Shoe manufacture; Structural analysis; Thermal cycling; High temperature; IDDP; Krafla geothermal field; Non-linear finite element model; Production casings; Steel casing; Structural modeling; Thermal contraction; Finite element method; finite element method; geothermal energy; geothermal power; numerical model; structural analysis; Iceland

Strontium and neodymium isotope systematics of target rocks and impactites from the El'gygytgyn impact structure: Linking impactites and target rocks - Wegner, Wencke; Koeberl, Christian (Meteoritics and Planetary Science, 2016)

Stratigraphy, sedimentology and structure of the Jurassic (Callovian to Lower Oxfordian) succession at Castle Hill, Scarborough, North Yorkshire, UK - Powell, John H.; Riding, James B. (Proceedings of the Yorkshire Geological Society, 2016)
Site investigation borehole cores and temporary shaft exposures at the Toll House Pumping Station shaft site, Castle Hill, Scarborough, North Yorkshire, have revealed new data on the Callovian to Lower Oxfordian (Jurassic) succession. The condensed transgressive marine unit, the Lower Callovian Cornbrash Formation, rich in berthierine ooids and abundant shelly fossils, and the attenuated Cayton Clay Formation represent the Early Callovian marine transgression that flooded the low-gradient alluvial plain, which is represented by the underlying Scalby Formation. The Callovian Osgodby Formation (Red Cliff Rock and Langdale members) is an extensively bioturbated, silty sandstone with abundant berthierine-pyrite ooids in the lower part. It was deposited in lower- to upper-shoreface settings. Slow sedimentation rates, with long sediment residence time, resulted in a diverse ichnofauna and a high bioturbation index. Framboidal pyrite ooids in the lower Osgodby Formation sandstones are interpreted as being formed in anoxic lagoons in the nearshore zone; ooids were subsequently swept offshore during storm surge-ebb events. Cold water dinoflagellate cysts of Boreal affinity such as Gonyaulacysta dentata in the lower part of the Oxford Clay Formation indicate an Early Oxfordian age. This is confirmed by the presence of the zonal ammonite species Quenstedoceras mariae and is consistent with a relatively cold, but warming, palaeoclimate at this time. Shaft excavations revealed a new major fault, the Toll House Fault, which is interpreted to be a splay fault bifurcating off the main Castle Hill Fault. Together, the Toll House and Castle Hill faults form the western bounding faults of the Peak Trough, a graben-like structure that extends northwards, offshore.Supplementary material: Supplementary data 1 (Macrofossil identifications from the Toll House shaft) and Supplementary data 2 (List of macropalaeontological specimens from the Toll House Boreholes) are available at https://dx.doi.org/10.6084/m9.figshare.c.3469968. © 2016 The Author(s). Published by The Geological Society of London for the Yorkshire Geological Society. All rights reserved.
Keywords: England; North Yorkshire; Scarborough [North Yorkshire]; United Kingdom; Ammonoidea; Dinophyceae; bioturbation; Callovian; Oxfordian; sandstone; sedimentation rate; sedimentology; storm surge; stratigraphy; transgression

Stochastic exploration and the geologic context of enhanced geothermal system viability on the Snake River Plain, Idaho - Moody, A.; Fairley, J.; Plummer, M. (Special Paper of the Geological Society of America, 2016)
Geothermal energy depends on high subsurface temperature, adequate permeability and fracture volume, and accessible groundwater supply to support heat exchange with surrounding rock. Some regions may have adequate thermal resources but lack the necessary permeability or deep circulating water. Exploitation of such areas for geothermal energy could occur if permeability can be enhanced enough to provide the necessary heat exchange. These improvements to the geothermal reservoir would produce what is termed an enhanced geothermal system (EGS). The Snake River Plain (SRP) in southern Idaho is a geological region with high heat flux ( 110 mW/m2) that has been recommended as an EGS target. In this study, we consider how the geologic and thermal history of the SRP might influence its EGS potential. We describe the fracture distribution (mean = 28.63 fractures/10 m) in a welded tuff core recovered from one of the few deep boreholes located on the SRP and provide a preliminary discussion of the likely geomechanical behavior under in situ stress. Spatial autocorrelation of fracture features is defined with geostatistical techniques and used in a stochastic simulation of possible structures in other welded tuff reservoirs. Autocorrelation scales for the continuous date are on the order of 70 meters with high subsample scale variability (56 m). Results should aid in designing criteria for a hydraulic fracturing plan that would augment the permeability and connectivity of an SRP reservoir's preexisting fracture network. © 2016 The Geological Society of America. All rights reserved.
cited By 0
Keywords: Autocorrelation; Boreholes; Fracture; Geothermal fields; Geothermal wells; Groundwater; Heat exchangers; Heat flux; Hydraulic fracturing; Petroleum reservoir engineering; Stochastic models; Stochastic systems; Welding; Enhanced geothermal systems; Fracture distributions; Geomechanical behavior; Geostatistical techniques; Preexisting fracture; Spatial autocorrelations; Stochastic simulations; Subsurface temperature; Geothermal energy; fracture network; geothermal power; geothermal system; groundwater exploration; heat flux; hydraulic fracturing; permeability; reservoir; surface temperature; Idaho; Idaho; Snake River Plain; United States

Special Collection: Rates and depths of magma ascent on earth: Degassing of hydrous trachytic campi flegrei and phonolitic vesuvius melts: Experimental limitations and chances to study homogeneous bubble nucleation - Preuss, Oliver; Marxer, Holger; Ulmer, Sarah; Johannes, Wolf; Nowak, Marcus (American Mineralogist, 2016)
Melt degassing by bubble nucleation and growth is a driving mechanism of magma ascent. Therefore, decompression experiments with hydrous silicate melts were used to investigate the onset and the dynamics of H2O degassing. Nominally H2O undersaturated trachytic Campi Flegrei and phonolitic Vesuvius melts representative for the magma compositions of the Campi Flegrei volcanic system were decompressed at a super-liquidus temperature of 1050°C from 200 MPa to final pressures (Pfinal) of 100, 75, and 60 MPa using continuous decompression rates of 0.024 and 0.17 MPa/s. Experiments started from either massive glass cylinders or glass powder to demonstrate the infl of the starting material on melt degassing. Glass powder can be used to shorten the equilibration time (teq) prior to decompression for dissolution of H2O in the melt. The decompressed samples were quenched and compared in terms of bubble number density (NV), porosity, and residual H2O content in the melt. Decompression of all glass cylinder samples led to homogeneous bubble nucleation with high NV of ∼105 mm-3. The supersaturation pressures for homogeneous bubble nucleation were estimated to be <76 MPa for the trachytic and <70 MPa for the phonolitic melt. In contrast to glass cylinders, the usage of glass powder equilibrated for 24 h before decompression prevented homogeneous bubble nucleation during decompression. We suggest that trapped air in the powder pore space resulted in the formation of tiny H2O-N2 bubbles throughout the samples prior to decompression. Degassing of these glass powder samples was facilitated by diffusive growth of these pre-existing bubbles and thus did not require signifi H2O supersaturation of the melt. This is evidenced by several orders of magnitude lower NV and lower residual H2O contents at correspondingly higher porosities compared to the glass cylinder samples. However, a signifi extension of teq to 96 h in the glass powder experiments led to degassing results comparable to the glass cylinder samples. This effect is probably due to Ostwald ripening, coalescence, and the ascent of the pre-existing bubbles during the extended teq prior to decompression. The NV of the glass cylinder samples were used to test the applicability of the vesiculation model provided by Toramaru (2006). For the applied decompression rates, the experimental NV are up to 5 orders of magnitude higher than the values predicted by the model. This may be mainly attributed to the usage of the macroscopic surface tension and the total H2O diffusivity in the model to describe the molecular process of bubble nucleation. A signifi increase in modeled NV can be achieved by application of a reduced surface tension in combination with the lower diffusivity of network formers as a limiting parameter for the formation of a bubble nucleus. This study demonstrates that the investigation of homogeneous bubble nucleation necessitates an optimized experimental protocol. We strongly recommend performing experiments with massive glass cylinders as starting material. The timescale of decompression is a limiting parameter and must be short enough to minimize the opportunity for a reduction of NV by bubble coalescence. Considering our comparably high NV, the samples of many previous experimental studies that were used to calibrate models for homogeneous bubble nucleation were probably subject to signifi NV reduction. Newly derived data from optimized experiments will require improved models for homogeneous bubble nucleation during magma ascent. © 2016 by Walter de Gruyter Berlin/Boston.
Keywords: Campania [Italy]; Campi Flegrei; Italy; Napoli [Campania]; Vesuvius; Coalescence; Crystallization; Cylinders (shapes); Degassing; Nucleation; Porosity; Silicates; Supersaturation; Surface tension; Bubble nucleation; Bubble number densities; Campi Flegrei; Decompression experiments; Magma ascents; bubble; decompression; degassing; magma; melt; volcanic glass; Glass

Spatio-temporal trends in normal-fault segmentation recorded by low-temperature thermochronology: Livingstone fault scarp, Malawi Rift, East African Rift System - Mortimer, E.; Kirstein, L.A.; Stuart, F.M.; Strecker, M.R. (Earth and Planetary Science Letters, 2016)
The evolution of through-going normal-fault arrays from initial nucleation to growth and subsequent interaction and mechanical linkage is well documented in many extensional provinces. Over time, these processes lead to predictable spatial and temporal variations in the amount and rate of displacement accumulated along strike of individual fault segments, which should be manifested in the patterns of footwall exhumation. Here, we investigate the along-strike and vertical distribution of low-temperature apatite (U –Th)/He (AHe) cooling ages along the bounding fault system, the Livingstone fault, of the Karonga Basin of the northern Malawi Rift. The fault evolution and linkage from rift initiation to the present day has been previously constrained through investigations of the hanging wall basin fill. The new cooling ages from the footwall of the Livingstone fault can be related to the adjacent depocentre evolution and across a relay zone between two palaeo-fault segments. Our data are complimented by published apatite fission-track (AFT) data and reveal significant variation in rock cooling history along-strike: the centre of the footwall yields younger cooling ages than the former tips of earlier fault segments that are now linked. This suggests that low-temperature thermochronology can detect fault interactions along strike. That these former segment boundaries are preserved within exhumed footwall rocks is a function of the relatively recent linkage of the system. Our study highlights that changes in AHe (and potentially AFT) ages associated with the along-strike displacement profile can occur over relatively short horizontal distances (of a few kilometres). This is fundamentally important in the assessment of the vertical cooling history of footwalls in extensional systems: temporal differences in the rate of tectonically driven exhumation at a given location along fault strike may be of greater importance in controlling changes in rates of vertical exhumation than commonly invoked climatic fluctuations. © 2016 Elsevier B.V.
cited By 20
Keywords: Apatite; Cooling systems; Fission reactions; Geologic models; Phosphate minerals; Tectonics; Temperature; Apatite fission tracks; Climatic fluctuations; Displacement profiles; East African Rift; Normal faults; Spatial and temporal variation; Thermochronology; Vertical distributions; Fault slips; fault scarp; fault zone; footwall; hanging wall; normal fault; segmentation; spatiotemporal analysis; thermochronology; East African Rift