Short Note. the smectite to corrensite transition: X-ray diffraction results from the MH-2B core, western Snake River Plain, Idaho, USA - Walker, J.; Wheeler, J. (Clay Minerals, 2016)
The MH-2B borehole, a part of Project HOTSPOT, was drilled to a depth of 1821 m in late Cenozoic basalts, hyaloclastites and interbedded lake sediments, on the Mountain Home Air Force Base in southern Idaho, USA. Drillers encountered hot water (145°C) under artesian pressure at 1745 m in a narrow zone of highly fractured rock associated with a major sub-surface fault. X-ray diffraction (XRD) analysis identified corrensite (with and without smectite) between 1700 and 1800 m, but only smectite above 1700 m and below 1800 m. This corrensite horizon contains a relatively narrow zone of fracturing and hot artesian water near its centre but for the most part occurs in relatively massive basalt flows. No evidence was found for randomly interstratified chlorite-smectite. © 2016 by Walter de Gruyter Berlin/Boston.
cited By 2
Keywords: X ray diffraction analysis; Air Force Base; Artesian pressure; Corrensite; Hyaloclastites; Lake sediments; Project hotspot; Smectites; Snake river plains; Basalt; artesian well; basalt; borehole breakout; Cenozoic; corrensite; hyaloclastite; hydrothermal alteration; lacustrine deposit; smectite; Idaho; Snake River Plain; United States

Shallow crustal discontinuities inferred from waveforms of microearthquakes: Method and application to KTB Drill Site and West Bohemia Swarm Area - Hrubcov'a, Pavla; Vavryčuk, V'aclav; Bouškov'a, Alena; Bohnhoff, Marco (Journal of Geophysical Research: Solid Earth, 2016)
The waveforms of microearthquakes are of high frequency and complicated. They contain many phases secondarily generated at crustal interfaces and at small-scale inhomogeneities. They are highly sensitive to focal mechanisms and thus very different for each station of local networks. However, with a large number of microearthquakes, the scattered waves present in the waveforms can serve for identifying the prominent crustal discontinuities and for determining their depth. In this paper, we develop a new approach for extracting information on crustal structure from such waveforms and apply it for determining depth and lateral variations of crustal discontinuities. We show that strong dependence of microseismic waveforms on radiation pattern requires good station coverage and knowledge of focal mechanisms of the microearthquakes. Analysis of real observations is supported by waveform modeling and by analysis of radiation patterns of scattered waves. The robustness of the inversion for depth of crustal interfaces is achieved by stacking of a large number of waveforms and by applying a grid search algorithm. The method is demonstrated on two microseismic data sets of different origin: microseismicity induced during the Continental Super-Deep Drilling Project (KTB) 2000 fluid injection experiment and natural seismicity in the West Bohemia swarm region. High-frequency conversions at the KTB site indicate a prominent interface at depths of 2.3-4.1 km consistent with previous interpretations. Geologically, it may represent the contact of granitoids with much faster metabasites underneath. Seismicity in West Bohemia indicates a strong-contrast interface at depths of 3.5-6.0 km. This interface is in agreement with previous profiling and might be related to trapping of fluid emanations ascending from the mantle. ©2016. American Geophysical Union. All Rights Reserved.
Keywords: Bohemian Massif; crustal structure; discontinuity; earthquake swarm; focal mechanism; microearthquake; seismic wave; waveform analysis

Seismicity distribution in conjunction with spatiotemporal variations of coseismic slip and postseismic creep along the combined 1999 Izmit-D{uzce rupture - Bohnhoff, M.; Ickrath, M.; Dresen, G. (Tectonophysics, 2016)
The North Anatolian Fault Zone (NAFZ) in NW Turkey as one of the most active and best studied strike-slip faults provides a unique opportunity to study earthquake related relaxation processes through analyzing co- and postseismic deformation. We study the spatial and temporal distributions of seismicity related to the two consecutive 1999 M > 7 Izmit and D{uzce earthquakes. A high-resolution aftershock catalogue including 10,000 hypocenters extending along the combined rupture zone and extending from prior to the Izmit event to after the D{uzce event is studied. Spatial and temporal distributions of events allow to identify distinct seismically active and inactive fault patches. Their location is related to the co- and postseismic deformation within and below the seismogenic layer, respectively. Four seismically inactive patches extending 30 –50 km along the rupture zone and down to 10 km depth are identified with a systematic spatial shift between them introduced by the D{uzce mainshock. The cumulative distribution of sub-areas hosting coseismic slip, aftershock clusters and postseismic creep shows that the entire upper (seismogenic) and lower (ductile) portions of the crust along the combined Izmit and D{uzce rupture zone are activated between rupture initiation and a two-year postseismic period. This observation was only achieved due to the subsequent occurrence of two adjacent M > 7 strike-slip earthquakes in combination with a distinct local seismic and geodetic monitoring. Our findings suggest that a coseismically introduced lateral and vertical slip deficit is systematically compensated postseismically in both the brittle and ductile portions of the crust. © 2016 Elsevier B.V.
cited By 15
Keywords: Creep; Strike-slip faults; Earthquake dynamics; NW Turkey; Postseismic creeps; Seismic cycle; Seismicity; Seismicity and tectonics; Seismotectonics; Spatial analysis; Earthquakes; coseismic process; creep; earthquake rupture; Kocaeli earthquake 1999; postseismic process; seismicity; seismotectonics; slip rate; spatial analysis; spatial distribution; spatial variation; temporal distribution; temporal variation; Duzce [Turkey]; Izmit; Kocaeli [Turkey]; Turkey

Seismic-wave propagation in shallow layers at the GONAF-tuzla site, Istanbul, Turkey - Raub, Christina; Bohnhoff, Marco; Petrovic, Bojana; Parolai, Stefano; Yanik, Kenan; Kartal, Recai Feyiz; Kiliç, Tuğbay (Bulletin of the Seismological Society of America, 2016)
Using the first dataset available from the downhole Geophysical Observatory of the North Anatolian Fault, we investigated near-surface seismic-wave propagation on the Tuzla Peninsula, Istanbul, Turkey. We selected a dataset of 26 seismograms recorded at Tuzla at sensor depths of 0, 71, 144, 215, and 288 m. To determine near-surface velocities and attenuation structures, the waveforms from all sensors were pairwise deconvolved and stacked. This produced low-noise empirical Green’s functions for each borehole depth interval. From the Green’s functions, we identified reflections from the free surface and a low-velocity layer between ∼90 and ∼140 m depth. The presence of a low-velocity zone was also confirmed by a sonic log run in the borehole. This structure, plus high near-surface P- and S-wave velocities of ∼3600 –4100 and ∼1800 m=s, lead to complex interference effects between upgoing and downgoing waves. As a result, the determination of quality factors (Q) with standard spectral ratio techniques was not possible. Instead, we forward modeled the Green’s functions in the time domain to determine effective Q values and to refine our velocity estimates. The effective QPvalues for the depth intervals of 0 –71, 0 –144, 0 –215, and 0 –288 m were found to be 19, 35, 39, and 42, respectively. For the S waves, we obtained an effective QS of 20 in the depth interval of 0 –288 m. Considering the assumptions made in our modeling approach, it is evident that these effective quality factors are biased by impedance contrasts between our observation points. Our results show that, even after correcting for a free-surface factor of 2, the motion at the surface was found to be 1.7 times greater than that at 71 m depth. Our efforts also illustrate some of the difficulties of dealing with site effects in a strongly heterogeneous subsurface. © 2016, Seismological Society of America. All rights reserved.
Keywords: Istanbul [Turkey]; Turkey; Tuzla [Istanbul]; Seismic waves; Seismology; Shear waves; Time domain analysis; Wave propagation; Well logging; Impedance contrast; Interference effects; Istanbul; Turkey; Low velocity layers; Low velocity zones; North Anatolian Fault; Observation point; P- and S-wave velocities; Green function; North Anatolian Fault; P-wave; S-wave; seismic wave; seismogram; shallow water; wave propagation; wave velocity; Velocity

Seismic imaging in the eastern Scandinavian Caledonides: siting the 2.5 km deep COSC-2 borehole, central Sweden - Juhlin, Christopher; Hedin, Peter; Gee, David G.; Lorenz, Henning; Kalscheuer, Thomas; Yan, Ping (Solid Earth, 2016)

Seismic anisotropy in mid to lower orogenic crust: Insights from laboratory measurements of Vp and Vs in drill core from central Scandinavian Caledonides - Wenning, Quinn C.; Almqvist, Bjarne S. G.; Hedin, Peter; Zappone, Alba (Tectonophysics, 2016)
Recent drilling of the first Collisional Orogeny in the Scandinavian Caledonides scientific borehole (COSC-1) near Åre, Sweden permitted a laboratory investigation of seismic anisotropy on high metamorphic grade and highly deformed core samples. The 2.5km deep borehole crosscuts the amphibolite-grade Lower Seve Nappe and intersects a high-strain shear zone in the lowermost 800m. Measurements of ultrasonic compressional (Vp) and shear (Vs) velocities are conducted at room temperature and pressures ranging from room conditions up to 260MPa on six core sections that represent the most abundant lithologies in the borehole. The core sections consist of two amphibolites, a calc-silicate gneiss, a felsic gneiss, an amphibole-rich gneiss, and a garnet-bearing micaschist from the shear zone. Three mutually perpendicular samples were taken to characterize the anisotropy induced by the clear foliation and lineation. The intrinsic (crack-free velocities) Vp0 and Vs0 in the direction perpendicular to foliation ranges from 5.51 to 6.67km/s and 3.31 to 4.13km/s, respectively. In the direction parallel to foliation the Vp0 and Vs0 ranges from 6.31 to 7.25km/s and 3.53 to 4.35km/s, respectively. Vp anisotropy ranges from 3% in the calc-silicate gneiss to 19% in the micaschist. In the upper crustal seismic reflection survey around the COSC-1 borehole, reflection coefficient analysis suggests that reflectors occur due to impedance contrast between commonly occurring amphibolites and gneisses in the upper 1800m and the micaschists below. When extrapolated to mid-crustal levels the analysis indicates that both rock types can produce reflection coefficients between adjacent lithologies in excess of 0.1. Similarities in lithologies, shear zone thickness, and reflectivity pattern in the Central Scandinavian Caledonides compared to other orogens (e.g., the Himalaya) demonstrate the importance of these measurements as a proxy for in-situ strongly anisotropic shear zones in the middle crust.
Keywords: Shear zone; Seismic anisotropy seismic velocity; Caledonian orogen; Middle crust reflectivity; Deep scientific drilling

Maximum earthquake magnitudes along different sections of the North Anatolian fault zone - Bohnhoff, M.; Mart'inez-Garz'on, P.; Bulut, F.; Stierle, E.; Ben-Zion, Y. (Tectonophysics, 2016)
Constraining the maximum likely magnitude of future earthquakes on continental transform faults has fundamental consequences for the expected seismic hazard. Since the recurrence time for those earthquakes is typically longer than a century, such estimates rely primarily on well-documented historical earthquake catalogs, when available. Here we discuss the maximum observed earthquake magnitudes along different sections of the North Anatolian Fault Zone (NAFZ) in relation to the age of the fault activity, cumulative offset, slip rate and maximum length of coherent fault segments. The findings are based on a newly compiled catalog of historical earthquakes in the region, using the extensive literary sources that exist owing to the long civilization record. We find that the largest M7.8-8.0 earthquakes are exclusively observed along the older eastern part of the NAFZ that also has longer coherent fault segments. In contrast, the maximum observed events on the younger western part where the fault branches into two or more strands are smaller. No first-order relations between maximum magnitudes and fault offset or slip rates are found. The results suggest that the maximum expected earthquake magnitude in the densely populated Marmara-Istanbul region would probably not exceed M7.5. The findings are consistent with available knowledge for the San Andreas Fault and Dead Sea Transform, and can help in estimating hazard potential associated with different sections of large transform faults. © 2016 The Authors.
cited By 67
Keywords: Earthquakes; Hazards; Seismology; Strike-slip faults; Structural geology; Transform faults; Continental transform; Earthquake magnitudes; Fault zone; Historical seismicity; North Anatolian Fault Zone; Fault slips; continental margin; earthquake catalogue; earthquake magnitude; fault zone; hazard assessment; North Anatolian Fault; San Andreas Fault; seismic source; seismicity; seismology; transform fault; Dead Sea; Istanbul [Turkey]; Marmara [Turkey]; Turkey

Treeline dynamics in Siberia under changing climates as inferred from an individual-based model for Larix - Kruse, S.; Wieczorek, M.; Jeltsch, F.; Herzschuh, U. (Ecological Modelling, 2016)
Siberian boreal forests are expected to expand northwards in the course of global warming. However, processes of the treeline ecotone transition, as well astiming and related climate feedbacks are still not understood. Here, we present Larix Vegetation Simulator’ LAVESI, an individual-based spatially-explicit model that can simulate Larix gmelinii (Rupr.) Rupr. stand dynamics in an attempt to improve our understanding about past and future treeline movements under changing climates. The relevant processes (growth, seed production and dispersal, establishment and mortality) are incorporated and adjusted to observation data mainly gained from the literature. Results of a local sensitivity analysis support the robustness of the model's parameterization by giving relatively small sensitivity values. We tested the model by simulating tree stands under modern climate across the whole Taymyr Peninsula, north-central Siberia (c. 64 –80° N; 92 –119° E). We find tree densities similar to observed forests in the northern to mid-treeline areas, but densities are overestimated in the southern parts of the simulated region. Finally, from a temperature-forcing experiment, we detect that the responses of tree stands lag the hypothetical warming by several decades, until the end of 21st century. With our simulation experiments we demonstrate that the newly-developed model captures the dynamics of the Siberian latitudinal treeline. © 2016
cited By 28
Keywords: Climate models; Dynamics; Ecology; Global warming; Sensitivity analysis; Forest change; Individual based model; Larix gmelinii; Local sensitivity analysis; Model description; Sensitivity values; Spatially explicit modeling; Time-lag effect; Forestry; boreal forest; climate change; climate effect; coniferous forest; ecological modeling; ecotone; experimental study; forest ecosystem; global warming; literature review; permafrost; sensitivity analysis; treeline; twenty first century; Krasnoyarsk [Russian Federation]; Russian Federation; Siberia; Taymyr Peninsula; Larix; Larix gmelinii

Locating mofettes using seismic noise records from small dense arrays and matched field processing analysis in the NW Bohemia/Vogtland Region, Czech Republic - Estrella, Hortencia Flores; Umlauft, Josefine; Schmidt, Andreas; Korn, Michael (Near Surface Geophysics, 2016)
The NW Bohemia/Vogtland region is characterized by currently ongoing geodynamic processes within the intracontinental lithospheric mantle. Among others, this activity results in the occurrence of mid-crustal earthquake swarms and CO2 degassing zones called mofettes. These two natural phenomena are related to each other since it is considered that fluid flow and fluid-induced effective stress can trigger earthquake swarms. At the Earth's surface, they appear spatially separated, but their connection could be explained by the existence of pathways within the crust that allow efficient and permanent fluid transport. However, neither the structure nor the position of such pathways has been imaged yet. With this background, we used a matched field processing analysis within the NW Bohemia/Vogtland region to locate mofettes and investigate their characteristics. Considering the CO2 degassing process as a high-frequency noise source, we chose two different test sites: the Doln'i Č'astkov Borehole, which is an artificial mofette that we used to validate the method, and the South Hartoušov mofette field, a natural CO2 degassing area. On both sites, we measured seismic noise in a continuous mode for several hours (7 hours to 9 hours), with a sampling frequency of 250 samples/second, in multiple campaigns using an array of about 60 × 60 m2 with approximately 30 randomly distributed stations. For the matched field processing computation, the phase velocity c(□) of the study area is required, which we obtained from active seismic experiments with vertical hammer-blow as the source. The phase velocity varies between 200 m/s and 420 m/s for Doln'i Č'astkov and between 100 m/s and 280 m/s for South Hartoušov, both in a frequency range of 7 Hz-60 Hz. With the matched field processing analysis at the artificial mofette in Doln'i Č'astkov, we could relocate the noise source successfully. In the South Hartoušov mofette field, we detected one dominant vertically extended noise source, probably a fluid pathway, as well as a small matched field processing maxima at the surface that can be related to a dry mofette. © 2016 European Association of Geoscientists & Engineers.
Keywords: Bohemia; Czech Republic; Germany; Vogtland; array; borehole; degassing; earthquake event; earthquake swarm; effective stress; fluid flow; phase velocity; seismic noise

Assembly processes of gastropod community change with horizontal and vertical zonation in ancient Lake Ohrid: A metacommunity speciation perspective - Hauffe, Torsten; Albrecht, Christian; Wilke, Thomas (Biogeosciences, 2016)
The Balkan Lake Ohrid is the oldest and most diverse freshwater lacustrine system in Europe. However, it remains unclear whether species community composition, as well as the diversification of its endemic taxa, is mainly driven by dispersal limitation, environmental filtering, or species interaction. This calls for a holistic perspective involving both evolutionary processes and ecological dynamics, as provided by the unifying framework of the metacommunity speciation model. The current study used the species-rich model taxon Gastropoda to assess how extant communities in Lake Ohrid are structured by performing process-based metacommunity analyses. Specifically, the study aimed (1) to identifying the relative importance of the three community assembly processes and (2) to test whether the importance of these individual processes changes gradually with lake depth or discontinuously with eco-zone shifts. Based on automated eco-zone detection and processspecific simulation steps, we demonstrated that dispersal limitation had the strongest influence on gastropod community composition. However, it was not the exclusive assembly process, but acted together with the other two processes - environmental filtering and species interaction. The relative importance of the community assembly processes varied both with lake depth and eco-zones, though the processes were better predicted by the latter. This suggests that environmental characteristics have a pronounced effect on shaping gastropod communities via assembly processes. Moreover, the study corroborated the high importance of dispersal limitation for both maintaining species richness in Lake Ohrid (through its impact on community composition) and generating endemic biodiversity (via its influence on diversification processes). However, according to the metacommunity speciation model, the inferred importance of environmental filtering and biotic interaction also suggests a small but significant influence of ecological speciation. These findings contribute to the main goal of the Scientific Collaboration on Past Speciation Conditions in Lake Ohrid (SCOPSCO) deep drilling initiative - inferring the drivers of biotic evolution - and might provide an integrative perspective on biological and limnological dynamics in ancient Lake Ohrid. © Author(s) 2016.
Keywords: Balkan; Lake Ohrid; Turkmenistan; Gastropoda; assembly rule; biodiversity; biozonation; community dynamics; dispersal; ecozone; evolutionary biology; gastropod; holistic approach; lacustrine environment; relative abundance; speciation (biology); species richness

Description of a new fossil diatom genus, Cribrionella gen. nov. (Bacillariophyta) from quaternary sediments of Lake Ohrid - Jovanovska, Elena; Cvetkoska, Aleksandra; Tofilovska, Slavica; Ognjanova-Rumenova, Nadja; Levkov, Zlatko (Phytotaxa, 2016)
A new diatom genus, Cribrionella gen. nov., is described from Quaternary sediments of Lake Ohrid. Cribrionella comprises distinct morphological features, such as: i) presence of submarginal alveoli followed by regularly or irregularly arranged areolae, ii) cribra on external areolar openings, iii) absence of silicate layers on internal areolar openings, but presence of thick and inwardly raised circumferential silica trabeculae, iv) rimoportulae positioned on costae, and v) absence of central fultoportulae. Detailed light and scanning electron microscope analyses were undertaken and used for comparison to morphologically related genera. The typus generis Cribrionella ohridana is compared to species from its morphologically closest genus Cyclotella sensu stricto (e.g., C. atomus, C. delicatula, C. bifacialis). Cribrionella ohridana has not been reported from the extant diatom flora of Lake Ohrid, nor in the nearby Lake Prespa. The discovery of a new genus in Lake Ohrid confirms again the importance of the lake, not only in light of species richness and endemicity, but also in evolutionary history of the family Stephanodiscaceae. © 2016 Magnolia Press.

Des-A-lupane in an East African lake sedimentary record as a new proxy for the stable carbon isotopic composition of C3 plants - Bree, L.G.J.; Rijpstra, W.I.C.; Al-Dhabi, N.A.; Verschuren, D.; Sinninghe Damst'e, J.S.; Leeuw, J.W. (Organic Geochemistry, 2016)
We studied the high-resolution and well-dated 25,000 year sedimentary record of Lake Challa, a deep tropical crater lake in equatorial East Africa, to explore new proxies for paleoenvironmental and paleohydrological change. Sedimentary biomarker analysis revealed the presence of des-A-triterpenoids with oleanane, ursane and lupane carbon skeletons, microbial degradation products of angiosperm plant triterpenoids. Their increased influx from 16,000 years ago corresponds with previously documented changes in the terrestrial vegetation of the Lake Challa basin during postglacial warming, in particular the relative increase in C3/C4 plant ratio inferred from the stable carbon isotopic signature (δ13C) of sedimentary n-alkanes derived from plant leaf waxes. In contrast to this n-alkane δ13C signature, the δ13C of des-A-lupane maintains a constant value of −27.4 ± 1.1‰ across the glacial –interglacial transition. Since des-A-lupane is derived from C3 plants, its δ13C signature is here proposed to represent a novel and independent proxy for the time-variable carbon isotopic composition of local terrestrial C3 plants, which can improve estimates of the C3/C4 plant ratio based on two-end member mixing models of n-alkane δ13C values. © 2016 Elsevier Ltd
cited By 11
Keywords: Biodegradation; Degradation; Isotopes; Lakes; Sedimentology; Vegetation; Carbon isotopic composition; Des-A-lupane; East Africa; Interglacial transitions; Lacustrine sediments; Microbial degradation; Terrestrial vegetation; Triterpenoids; Paraffins; alkane; angiosperm; C3 plant; C4 plant; carbon isotope; isotopic ratio; lacustrine deposit; leaf; microbial activity; paleoenvironment; paleohydrology; Postglacial; reconstruction; stable isotope; terpene; warming; wax; Kilimanjaro [Tanzania]; Lake Challa; Tanzania; Magnoliophyta

Deep Borehole Field Test Research Activities at LBNL. Fuel Cycle Technology. - Dobson, Patrick; Tsang, Chin-Fu; Kneafsey, Timothy; Borglin, Sharon; Piceno, Yvette; Andersen, Gary; Nakagawa, Seiji; Nihei, Kurt; Rutqvist, Jonny; Doughty, Christine; et al. (Lawrence Berkeley National Laboratory (LBNL), 2016)

Damaged beyond repair? Characterising the damage zone of a fault late in its interseismic cycle, the Alpine Fault, New Zealand - Williams, J.N.; Toy, V.G.; Massiot, C.; McNamara, D.D.; Wang, T. (Journal of Structural Geology, 2016)
X-ray computed tomography (CT) scans of drill-core, recovered from the first phase of the Deep Fault Drilling Project (DFDP-1) through New Zealand's Alpine Fault, provide an excellent opportunity to study the damage zone of a plate-bounding continental scale fault, late in its interseismic cycle. Documentation of the intermediate-macro scale damage zone structures observed in the CT images show that there is no increase in the density of these structures towards the fault's principal slip zones (PSZs), at least within the interval sampled, which is 30 m above and below the PSZs. This is in agreement with independent analysis using borehole televiewer data. Instead, we conclude the density of damage zone structures to correspond to lithology. We find that 72% of fractures are fully healed, by a combination of clays, calcite and quartz, with an additional 24% partially healed. This fracture healing is consistent with the Alpine Fault's late interseismic state, and the fact that the interval of damage zone sampled coincides with an alteration zone, an interval of extensive fluid-rock interaction. These fractures do not impose a reduction of P-wave velocity, as measured by wireline methods. Outside the alteration zone there is indirect evidence of less extensive fracture healing. © 2016 Elsevier Ltd
cited By 27
Keywords: Fracture; Lithology; Seismic waves; Wave propagation; Alpine Faults; Continental scale; Damage zones; DFDP; Fluid-rock interaction; Fracture density; Independent analysis; X-ray computed tomography; Computerized tomography; earthquake damage; fault zone; fracture; lithology; P-wave; plate boundary; slip; wave velocity; Alpine Fault Zone; New Zealand; South Island

Crystallization of ikaite and its pseudomorphic transformation into calcite: Raman spectroscopy evidence - S'anchez-Pastor, N.; Oehlerich, Markus; Astilleros, Jos'e Manuel; Kaliwoda, Melanie; Mayr, Christoph C.; Fern'andez-D'iaz, Lurdes; Schmahl, Wolfgang W. (Geochimica et Cosmochimica Acta, 2016)

Constraints on paleofluid sources using the clumped-isotope thermometry of carbonate veins from the SAFOD (San Andreas Fault Observatory at Depth) borehole - Luetkemeyer, P.B.; Kirschner, D.L.; Huntington, K.W.; Chester, J.S.; Chester, F.M.; Evans, J.P. (Tectonophysics, 2016)
The San Andreas Fault Observatory at Depth (SAFOD), near Parkfield, California, is a borehole drilled through two active deforming zones of the San Andreas fault, the Southwest Deforming Zone (SDZ) and the Central Deforming Zone (CDZ). These zones accommodate displacement by seismic slip and aseismic creep. Elevated fluid pressures and fluid –rock interactions have been proposed to explain the low apparent strength and aseismic creep observed, but the origin of the fluids and existence of high fluid pressures remains uncertain. We use clumped-isotope thermometry and δ18O –δ13C compositions of calcite in veins to constrain the origin of paleofluids and compare these results to the isotopic composition of modern-day pore fluids from the SAFOD borehole and nearby areas. We observe that: (1) calcite vein temperatures vary from 81 to 134 °C, which overlaps the current ambient borehole temperatures of 110 –115 °C at sampled depths; (2) vein calcite is not in carbon isotope equilibrium with modern-day pore fluids; (3) the δ18O values of paleofluids close to the SDZ and CDZ, calculated from vein δ18O and temperature data, are not in equilibrium with local modern-day pore waters but approach equilibrium with modern pore waters far from these zones; and (4) syntectonic vein calcite is only in C- and O-isotopic equilibrium with their host rocks within the SDZ and CDZ. Spatial patterns of δ18O and δ13C show little evidence for across-fault fluid-flow. Clumped isotope temperatures are consistent with locally-derived fluid sources, but not with continuous or episodic replenishment of fluids from shallow sedimentary brines or deep fluid sources. Our findings are compatible with flow of meteoric fluids from the southwestern damage zone into the SDZ and CDZ, which would have favored the formation of weak phyllosilicates and contributed to the present day weakness of the two actively deforming zones. © 2016 Elsevier B.V.
cited By 13
Keywords: Calcite; Carbon; Creep; Deformation; Faulting; Fluids; Isotopes; Observatories; Silicates; Strike-slip faults; Thermometers; Water; Borehole temperature; Calcite veins; Clumped isotopes; Fluid-rock interaction; Isotopic composition; SAFOD; San Andreas fault; Syn-tectonic veins; Flow of fluids; borehole geophysics; calcite; carbonate rock; fault zone; fracture flow; hydrogeology; isotopic composition; meteoric water; San Andreas Fault; vein (geology); water-rock interaction; California; Parkfield; United States

Compositional variation within thick (>10 m) flow units of Mauna Kea Volcano cored by the Hawaii Scientific Drilling Project - Huang, S.; Vollinger, M.J.; Frey, F.A.; Rhodes, J.M.; Zhang, Q. (Geochimica et Cosmochimica Acta, 2016)
Geochemical analyses of stratigraphic sequences of lava flows are necessary to understand how a volcano works. Typically one sample from each lava flow is collected and studied with the assumption that this sample is representative of the flow composition. This assumption may not be valid. The thickness of flows ranges from <1 to >100 m. Geochemical heterogeneity in thin flows may be created by interaction with the surficial environment whereas magmatic processes occurring during emplacement may create geochemical heterogeneities in thick flows. The Hawaii Scientific Drilling Project (HSDP) cored ∼3.3 km of basalt erupted at Mauna Kea Volcano. In order to determine geochemical heterogeneities in a flow, multiple samples from four thick (9.3 –98.4 m) HSDP flow units were analyzed for major and trace elements. We found that major element abundances in three submarine flow units are controlled by the varying proportion of olivine, the primary phenocryst phase in these samples. Post-magmatic alteration of a subaerial flow led to loss of SiO2, CaO, Na2O, K2O and P2O5, and as a consequence, contents of immobile elements, such as Fe2O3 and Al2O3, increase. The mobility of SiO2 is important because Mauma Kea shield lavas divide into two groups that differ in SiO2 content. Post-magmatic mobility of SiO2 adds complexity to determining if these groups reflect differences in source or process. The most mobile elements during post-magmatic subaerial and submarine alteration are K and Rb, and Ba, Sr and U were also mobile, but their abundances are not highly correlated with K and Rb. The Ba/Th ratio has been used to document an important role for a plagioclase-rich source component for basalt from the Galapagos, Iceland and Hawaii. Although Ba/Th is anomalously high in Hawaiian basalt, variation in Ba abundance within a single flow shows that it is not a reliable indicator of a deep source component. In contrast, ratios involving elements that are typically immobile, such as La/Nb, La/Th, Nb/Th, Ce/Pb, Sr/Nd, La/Sm, Sm/Yb, Nb/Zr, Nb/Y and La/Yb, are uniform within the units, and they can be used to constrain petrogenetic processes. Nevertheless all elements are mobile under some conditions. For example, a surprising result is that relative to other samples, the uppermost sample collected from subaerial flow Unit 70, less than 1 m below the flow surface, is depleted in P, HREE and Y relative to all other samples from this flow unit. This result is complementary to the P, REE and Y enrichment found in subaerial lava flows from several Hawaiian shields, e.g., Kahoolawe and Koolau Volcanoes. These enrichments require mobilization of REE and followed by deposition a P-rich mineral. © 2016 Elsevier Ltd
cited By 6
Keywords: chemical composition; core analysis; element mobility; enrichment; igneous geochemistry; lava flow; sequence stratigraphy; shield volcano; trace element; volcanic rock; Hawaii [(ISL) Hawaiian Islands]; Hawaii [United States]; Hawaiian Islands; Mauna Kea

Complexity of diatom response to Lateglacial and Holocene climate and environmental change in ancient, deep and oligotrophic Lake Ohrid (Macedonia and Albania) - Zhang, X.S.; Reed, J.M.; Lacey, J.H.; Francke, A.; Leng, M.J.; Levkov, Z.; Wagner, B. (Biogeosciences, 2016)
Lake Ohrid (Macedonia and Albania) is a rare example of a deep, ancient Mediterranean lake and is a key site for palaeoclimate research in the northeastern Mediterranean region. This study conducts the analysis of diatoms as a proxy for Lateglacial and Holocene climate and environmental change in Lake Ohrid at a higher resolution than in previous studies. While Lake Ohrid has the potential to be sensitive to water temperature change, the data demonstrate a highly complex diatom response, probably comprising a direct response to temperature-induced lake productivity in some phases and an indirect response to temperaturerelated lake stratification or mixing and epilimnetic nutrient availability in others. The data also demonstrate the possible influence of physical limnological (e.g. the influence of wind stress on stratification or mixing) and chemical processes (e.g. the influence of catchment dynamics on nutrient input) in mediating the complex response of diatoms. During the Lateglacial (ca. 12 300-11 800 cal yr BP), the low-diversity dominance of hypolimnetic Cyclotella fottii indicates low lake productivity, linked to low water temperature. Although the subsequent slight increase in small, epilimnetic C. minuscula during the earliest Holocene (ca. 11 800-10 600 cal yr BP) suggests climate warming and enhanced stratification, diatom concentration remains as low as during the Lateglacial, suggesting that water temperature increase was muted across this major transition. The early Holocene (ca. 10 600-8200 cal yr BP) is characterised by a sustained increase in epilimnetic taxa, with mesotrophic C. ocellata indicating high water-temperature-induced productivity between ca. 10 600-10 200 cal yr BP and between ca. 9500-8200 cal yr BP and with C. minuscula in response to low nutrient availability in the epilimnion between ca. 10 200-9500 cal yr BP. During the middle Holocene (ca. 8200-2600 cal yr BP), when sedimentological and geochemical proxies provide evidence for maximum Holocene water temperature, anomalously low C. ocellata abundance is probably a response to epilimnetic nutrient limitation, almost mimicking the Lateglacial flora apart from the occurrence of mesotrophic Stephanodiscus transylvanicus in the hypolimnion. During the late Holocene (ca. 2600 cal yr BP-present), high abundance and fluctuating composition of epilimnetic taxa are probably a response more to enhanced anthropogenic nutrient input, particularly nitrogen enrichment, than to climate. Overall, the data indicate that previous assumptions concerning the linearity of diatom response in this deep, ancient lake are invalid, and multi-proxy analysis is essential to improve understanding of palaeolimnological dynamics in future research on the long, Quaternary sequence. © Author(s) 2016.
cited By 9
Keywords: butterfly; diatom; environmental change; epilimnion; Holocene; late glacial; nutrient availability; oligotrophic environment; paleolimnology; perciform; proxy climate record; water temperature; Albania; Lake Ohrid; Macedonia [Southern Europe]; Bacillariophyta; Cyclotella; Cyclotella ocellata; Stephanodiscus

Coeval ages of Australasian, Central American and Western Canadian tektites reveal multiple impacts 790 ka ago - Schwarz, W.H.; Trieloff, M.; Bollinger, K.; Gantert, N.; Fernandes, V.A.; Meyer, H.-P.; Povenmire, H.; Jessberger, E.K.; Guglielmino, M.; Koeberl, C. (Geochimica et Cosmochimica Acta, 2016)
High resolution 40Ar-39Ar step heating dating of australites and indochinites, representing a large area of the Australasian strewn field, and more recently discovered tektite-like glasses from Central America (Belize) and Western Canada, were carried out. Precise plateau ages were obtained in all cases, yielding indistinguishable ages of 789 ± 9 ka for four australites, 783 ± 5 ka for four indochinites, 783 ± 17 ka for one Western Canadian and 769 ± 16 ka for one Belize impact glass. Concerning major elements and REEs, australites and the Western Canadian impact glass are indistinguishable. If the Western Canadian sample was transported by impact ejection and belongs to the Australasian strewn field, this implies extremely far ballistic transport of 9000 km distance, assuming a source crater in southern Asia. The distinct major element and REE composition of the Belize impact glass suggests formation in another separate impact event. We conclude that the Australasian/Western Canadian impact glasses formed 785 ± 7 ka ago in a single event and Belize impact glass in a separate event 769 ± 16 ka ago. The two impact events forming these two strewn fields occurred remarkably closely related in time, i.e., separated by <30 ka. © 2016 Elsevier Ltd.
cited By 27
Keywords: argon-argon dating; impact structure; Quaternary; rare earth element; tektite; Belize [Central America]; Canada

Coesite in suevites from the Chesapeake Bay impact structure - Jackson, J.C.; Horton, Jr.; Chou, I.-M.; Belkin, H.E. (Meteoritics and Planetary Science, 2016)
The occurrence of coesite in suevites from the Chesapeake Bay impact structure is confirmed within a variety of textural domains in situ by Raman spectroscopy for the first time and in mechanically separated grains by X-ray diffraction. Microtextures of coesite identified in situ investigated under transmitted light and by scanning electron microscope reveal coesite as micrometer-sized grains (1-3 μm) within amorphous silica of impact-melt clasts and as submicrometer-sized grains and polycrystalline aggregates within shocked quartz grains. Coesite-bearing quartz grains are present both idiomorphically with original grain margins intact and as highly strained grains that underwent shock-produced plastic deformation. Coesite commonly occurs in plastically deformed quartz grains within domains that appear brown (toasted) in transmitted light and rarely within quartz of spheroidal texture. The coesite likely developed by a mechanism of solid-state transformation from precursor quartz. Raman spectroscopy also showed a series of unidentified peaks associated with shocked quartz grains that likely represent unidentified silica phases, possibly including a moganite-like phase that has not previously been associated with coesite. © 2016 The Meteoritical Society.
cited By 7

Changes in repeating earthquake slip behavior following the 2004 Parkfield main shock from waveform empirical Green's functions finite-source inversion - Kim, A.; Dreger, D.S.; Taira, T.; Nadeau, R.M. (Journal of Geophysical Research: Solid Earth, 2016)
Finite-source inversions are performed using small earthquake waveforms as empirical Green's functions (eGf) to investigate the rupture process of repeating earthquakes along the San Andreas Fault in Parkfield, California. The eGf waveform inversion method is applied to a repeating Mw 2.1 Parkfield earthquake sequence using three-component velocity waveforms recorded by an array of borehole seismometers. The obtained models show a circular slip distribution with a 20 m radius, a 3.0-4.2 cm average slip of the main asperity, and peak displacement of 10.6-13.5 cm. The static stress drop distribution shows that the main asperity has a peak stress drop of 69.5-94.7 MPa. The inversion results support an earlier finding by Dreger et al. (2007) that high-strength asperities exist in the rupture areas of the Mw 2.1 events at Parkfield. In addition, notable temporal peak slip and stress drop reduction was observed after the 2004 Parkfield event while the average value remains constant ( 12 MPa) over time. These events may represent mechanically strong sections of the fault, surrounded by regions that are undergoing continuous deformation (creep), Given repeated loading of the strong asperities, it would be expected that these similar repeating earthquakes should also have very similar slip distributions since surrounding regions are deforming aseismically. There are small differences in the waveforms of these repeating earthquakes, and this could be because of rupture nucleation points not being in exactly the same location within the region of the fault that is capable of stick-slip behavior. Our result indicates that waveform slip inversion is needed to reveal spatial and temporal variations of the stress drop within the rupture area to improve understanding of fault healing and rupture mechanics. ©2016. American Geophysical Union. All Rights Reserved.
cited By 29
Keywords: earthquake magnitude; earthquake prediction; earthquake rupture; fault displacement; Green function; inverse problem; San Andreas Fault; seismograph; stick-slip; stress; wave velocity; California; Parkfield; United States

Changes in dominant moisture sources and the consequences for hydroclimate on the northeastern Tibetan Plateau during the past 32 kyr - Thomas, E.K.; Huang, Y.; Clemens, S.C.; Colman, S.M.; Morrill, C.; Wegener, P.; Zhao, J. (Quaternary Science Reviews, 2016)
Lake Qinghai, located on the northeastern Tibetan Plateau north of the modern maximum summer monsoon extent, is well situated to record northward advances of the summer monsoon. Existing paleoclimate records contain conflicting evidence for the timing of summer monsoon advance into this region: an early arrival pre-Younger Dryas or a late arrival at the beginning of the Holocene. A 30-kyr-long leaf wax hydrogen isotope (n-alkanoic acid, δ2Hwax) record from Lake Qinghai helps to address this discrepancy by elucidating changes in the three main moisture sources in this region: southerly (summer monsoon), northwesterly, and local precipitation. Lake Qinghai δ2Hwax indicates that the arid glacial period was dominated by northwesterly moisture. Extremely arid conditions prevailed from 15 to 14 ka, likely because westerly winds were weakening and the summer monsoon had not yet reached this region. This arid period ended by 13.6 ka when small amounts of summer monsoon precipitation reached Lake Qinghai. Summer monsoon moisture subsequently retreated off of the northeastern Tibetan Plateau during the Younger Dryas and re-advanced in the early Holocene. Summer monsoon precipitation decreased progressively throughout the Holocene in response to decreasing summer insolation, and the modern northwesterly- and local-dominated moisture regime was attained ca. 2.6 ka. Lake Qinghai δ2Hwax demonstrates that the summer monsoon extent was dynamic during the past 30 kyr, responding dramatically to insolation and North Atlantic circulation changes. Moreover, Lake Qinghai δ2Hwax demonstrates that local and northwesterly air masses are important moisture sources to the northeastern Tibetan Plateau, and should be considered when reconstructing past hydroclimate in this region. © 2015 Elsevier Ltd.
cited By 75
Keywords: Incident solar radiation; Isotopes; Lakes; Moisture; Solar radiation; Holocenes; Hydrogen isotope; Monsoon; Tibetan Plateau; Westerlies; Younger Dryas; Atmospheric thermodynamics; Holocene; hydrogen isotope; moisture content; monsoon; paleoclimate; precipitation (climatology); Quaternary; wax; westerly; China; Qinghai; Qinghai Lake; Qinghai-Xizang Plateau

Borehole seismic network at Koyna, India - Shashidhar, D.; Satyanarayana, H.V.S.; Mahato, C.R.; Mallika, K.; Rao, N.P.; Gupta, H.K. (Seismological Research Letters, 2016)
The Koyna region located near the west coast of India has been continuously having artificial water-reservoir-triggered earthquakes since the impoundment of Koyna Dam in 1962. To improve the accuracy of locations of these triggered earthquakes, a unique network of eight borehole seismometers surrounding the seismicity was designed. Five of these have been installed at depths varying from 1134 to 1522 m, well below the Deccan basalt cover. As it is difficult to install the borehole seismometers with desired orientation of the horizontal components, amplitudes of P waves were used to decipher the true orientations after installation. Analysis of data for the period March-June 2015 demonstrated that there is a remarkable increase in the number of earthquakes located with the help of borehole seismometers. Using the existing network of 21 broadband surface seismometers, 184 earthquakes of ML ≥ 0:5 were located; however, with the borehole seismometers, the number of the located events increased to 888 such events. The data also indicate an increase in seismic activity corresponding to the period of increase in the rate of emptying of the Koyna and Warna reservoirs.
cited By 20
Keywords: Geophysics; Reservoirs (water); Seismic waves; Seismographs; Seismology; Analysis of data; Artificial water; P waves; Seismic activity; Seismic networks; Triggered Earthquakes; West coast; Earthquakes; borehole geophysics; earthquake mechanism; P-wave; reservoir impoundment; reservoir-induced seismicity; seismicity; seismograph; trigger mechanism; India; Koyna Dam; Maharashtra

Bimaterial interfaces at the Karadere segment of the North Anatolian Fault, northwestern Turkey - Najdahmadi, B.; Bohnhoff, M.; Ben-Zion, Y. (Journal of Geophysical Research: Solid Earth, 2016)
We image velocity contrast (bimaterial) interfaces along the Karadere Fault of the North Anatolian Fault Zone, toward the eastern part of the 1999 Izmit Mw 7.4 rupture in NW Turkey, using waveforms recorded by a local seismic network. Applying an automatic procedure for identification and picking of fault zone head waves (FZHW) and direct P arrivals, and manually revising the picks through particle motion analysis, we identify two different groups of FZHW as well as fault zone reflected waves (FZRW). The first group of FZHW has a moveout with respect to the direct P arrivals with distance traveled along the fault, indicating a deep bimaterial interface down to the base of the seismogenic crust with an average velocity contrast of 3.4%. The second group of FZHW has a constant time difference from the direct P arrivals and is associated with a shallow local interface bounding a low-velocity damage zone or basin structure that extends to a depth of 4-5 km. While the first group of FZHW exists on the slower crustal block, the second group of FZHW and the FZRW are present generally on both sides of the fault. These phases add to the richness and complexity of the early P waveforms observed at stations close to a large fault. The relatively low velocity contrast across the Karadere Fault compared to values to the west may have helped stopping the Izmit rupture. ©2016. American Geophysical Union. All Rights Reserved.
cited By 26
Keywords: fault zone; North Anatolian Fault; P-wave; wave reflection; waveform analysis; Turkey

Aptian giant explosive volcanic eruptions in the Songliao Basin and northeast Asia: A possible cause for global climate change and OAE-1a - Wang, P.; Chen, C.; Liu, H. (Cretaceous Research, 2016)
Volcanism is a natural climate force that causes variations in temperatures. The Aptian Oceanic Anoxic Event 1a (OAE-1a) was preceded by a prominent negative C-isotope excursion attributed to major volcanism of the Ontong Java plateau (OJP), which presumably resulted in a pCO2 increase and a climatic change. However, the OJP alone may not adequately explain some important isotopic signatures such as the negative strontium-isotope excursion from 125 Ma to 113 Ma that is recorded in the corresponding marine deposits. We present an independent and hitherto undocumented case, the giant Aptian volcanism in the Songliao Basin and northeast Asia (SB-V) on the Cretaceous active continental margin between the Eurasian and the Pacific plates, which covered an area of ca. 2.3 × 106 km2, nearly matching the simultaneous case of the OJP. Intensive strong, explosive volcanic eruptions of the SB-V occurred at 121-109 Ma and introduced a large volume of fine-grained volcanic ash and degassing volatiles into the atmosphere. The Aptian isotopic ratios (87Sr/86Sr, 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb) of marine carbonates from the Mid-Pacific shift in values between their Barremian pre-excursion high values and the negative magmatic values of the SB-V. The transient global cooling at the onset of the OAE-1a coincided with the beginning of the violent acidic eruption of the SB-V (119.9-120.2 Ma). We therefore infer that the SB-V must have played a role in the Aptian global climatic changes and OAE-1a through the heavy fall of volcanic dust and the outgassing of aerosol and greenhouse gases. © 2015 Elsevier Ltd.
cited By 20
Keywords: aerosol; anoxic conditions; Aptian; climate change; explosive volcanism; global change; greenhouse gas; isotopic analysis; volcanic ash; volcanic eruption; China; Northeast Asia; Ontong Java Plateau; Pacific Ocean; Songliao Basin

Differential resilience of ancient sister lakes Ohrid and Prespa to environmental disturbances during the Late Pleistocene - Jovanovska, Elena; Cvetkoska, Aleksandra; Hauffe, Torsten; Levkov, Zlatko; Wagner, Bernd; Sulpizio, Roberto; Francke, Alexander; Albrecht, Christian; Wilke, Thomas (Biogeosciences, 2016)
Ancient lakes, such as lakes Ohrid and Prespa on the Balkan Peninsula, have become model systems for studying the link between geological and biotic evolution. Recently, the scientific deep-drilling project Scientific Collaboration on Past Speciation Conditions in Lake Ohrid (SCOPSCO) was initiated to better understand the environmental, climatic, and limnological evolution of the lake. It revealed that Lake Ohrid experienced a number of environmental disturbances during its ca. 2.0 million year long history. These are comprised of disturbances that lasted over longer periods of time (press events) such as glacial-interglacial cycles and Heinrich events, as well as sudden and short disturbances (pulse events) like the deposition of landslides, earthquakes, and volcanic ash depositions. The latter includes one of the most severe volcanic episodes during the Late Pleistocene: the eruption of the Campanian Ignimbrite (known as Y-5 marine tephra layer) from the Campi Flegrei caldera, dated to 39.6 ± 0.1 thousand years ago. The event is recorded by the deposition of a ca. 15 cm thick tephra layer in sediment cores of lakes Ohrid (DEEP-5045-1) and Prespa (Co1204). Coincidently, this pulse event is superimposed by the Heinrich H4 event, 40.4-38.4 thousand years ago. In the current paper, diatoms were used as proxies to compare the responses of these lakes to the Y-5 (pulse) and the H4 (press) disturbances. Based on stratigraphically constrained incremental sum of squares cluster (CONISS) and unconstrained Partitioning Around Medoids (PAM) analyses, we found little evidence that diatom community compositions in either lake responded to the H4 event. However, the Y-5 influx caused clear and rapid diatom community changes. After the initial response, community compositions in Lake Ohrid and, to a lesser extent, in Lake Prespa slowly returned to their quasi pre-disturbance state. Moreover, there is no evidence for disturbance-related extinction events. The combined evidence from these findings suggests that lakes Ohrid and Prespa likely did not experience regime shifts. It is therefore concluded that both lakes show resilience to environmental disturbance. However, it seems that Lake Ohrid is more resilient than Lake Prespa, as the recovery of diatom communities is more pronounced and its estimated recovery time is only ca. 1100 years vs. ca. 4000 years in Lake Prespa. The reasons for the differential responses remain largely unknown, but differences in geology, lake age, limnology, and intrinsic parameters of the diatom proxies may play an important role. © Author(s) 2016.
Keywords: Balkans; Campania [Italy]; Campi Flegrei; Italy; Lake Mikri Prespa; Lake Ohrid; Napoli [Campania]; Bacillariophyta; Campanian; community composition; diatom; ecosystem resilience; environmental disturbance; glacial-interglacial cycle; Heinrich event; paleoclimate; Pleistocene; sediment core; speciation (biology)

Application of raman spectroscopy and high-precision geochemistry for study of stromatolites - Medvedev, Pavel V; Chazhengina, Svetlana Y; Svetov, Sergey A (Lecture Notes in Earth System Sciences, 2016)
Paleoproterozoic (2.0 –2.2 Ga) stromatolites from drill cores of the ICDP Project FAR DEEP were studied by Raman spectroscopy and inductively coupled plasma mass spectrometry with laser ablation (LA-ICP MS) methods. Morphological features of the studied Paleoproterozoic stromatolites together with identification of synsedimentary carbonaceous matter by Raman spectroscopy are strong argument for biogenic origin of these carbonate buildups. Precision geochemical analysis of the stromatolite laminae composition links to sedimentary settings and environmental conditions of the microbialite formation. © 2016, Springer International Publishing Switzerland.
cited By 1
Keywords: carbonate sediment; environmental conditions; geochemistry; inductively coupled plasma method; microbialite; Proterozoic; Raman spectroscopy; stromatolite; Baltic Shield; East European Craton

Application of Crust 1 10k ultra-deep scientific drilling rig in Songliao Basin Drilling Project (CCSD-SKII) - Sun, Y.; Zhang, F.; Wang, Q.; Gao, K. (Journal of Petroleum Science and Engineering, 2016)
This paper presents the earth science program SinoProbe in China, especially the deep continental scientific drilling equipment: Crust 1 10k ultra-deep scientific drilling rig and 4 indigenous key equipment: Topdrive system, Pipe handler, Hydraulic catwalk and Iron roughneck. These equipment can save auxiliary time, improve drilling efficiency and reduce labor intensity. Components and technical parameters were also introduced. Crust 1 was deployed to drill through the Cretaceous continental strata of continental scientific drilling well: Songliao Basin Drilling Project (CCSD-SKII), which is the deepest scientific drilling program in China. Casing program was also introduced in this paper. Automated equipment performs a critical function in CCSD-SKII, the application can provide experience for furthermore scientific drilling program with designed well depth over 10,000 m in China. © 2016 Elsevier B.V..
cited By 17
Keywords: Application programs; Auxiliary equipment; Drilling rigs; Equipment; Hydraulic machinery; Catwalk; Crust 1; Drilling projects; Iron roughneck; Topdrive; Ultra-deep drilling; Drilling equipment; Chinese Continental Scientific Drilling Project; Cretaceous; drilling; drilling rig; hydrocarbon exploration; China; Songliao Basin

Analysis of velocity dispersion using full-waveform multichannel sonic logging data: A case study - Sun, L.F.; Milkereit, B.; Tisato, N. (Geophysical Prospecting, 2016)
Seismic attenuation and velocity dispersion are potentially able to reveal the rock physical properties of the subsurface. Conventionally, a frequency-independent quality factor (Q) is measured. This Q is equivalent to the total velocity dispersion in a seismic record and is inadequate for analysing the attenuation mechanism or rock physical properties. Here a new method is proposed to extract the velocity dispersion curves so that more attributes can be obtained from full-waveform multichannel sonic logging data, especially the critical frequency (fc) if it is within the bandwidth of the data. This method first decomposes the seismic data into a series of frequency components, computes the semblance of each frequency component for different velocity values, cross-correlates the semblance matrices of adjacent frequency components to get the velocity gradients, and finally integrates to obtain a velocity dispersion curve. Results of this method are of satisfactory accuracy and robustness. This method is applied to the data acquired in Mallik 5L-38 gas hydrate research well in Mackenzie Delta, Northwest Territories, Canada. The observed P-wave velocity dispersion compares well with the geological setting. In the gas hydrate zone (about 900 m –1100 m), high concentration of gas hydrate causes very strong velocity dispersion and a distinct fc at about 15 kHz, likely due to strong scattering of centimetre-scale inclusions of gas hydrate; concurrently, water flow in connected cracks in some ranges of this zone adds a large part of velocity dispersion and a dimmer fc at about 9.5 kHz. Immediate underneath the gas hydrate zone, abundant free water in weakly laminated sediments causes quite strong velocity dispersion and an fc at about 6.5 kHz. Velocity dispersion is mild and without an obvious fc in sediments above the gas hydrate zone. © 2016 European Association of Geoscientists & Engineers
cited By 4
Keywords: Acoustic logging; Flow of water; Gas hydrates; Gases; Hydration; Physical properties; Seismic waves; Seismology; Velocity; Wave propagation; Critical frequencies; Frequency components; Frequency independent; Geological setting; Laminated sediments; Rock physical properties; Seismic attenuation; Velocity dispersion; Dispersion (waves); data acquisition; gas hydrate; logging (geophysics); P-wave; Q factor; rock property; seismic attenuation; seismic velocity; wave dispersion; waveform analysis; Canada; Mackenzie Delta; Northwest Territories

Analysis of 6-year fluid electric conductivity logs to evaluate the hydraulic structure of the deep drill hole at Outokumpu, Finland - Sharma, Prabhakar; Tsang, Chin-Fu; Kukkonen, Ilmo T.; Niemi, Auli (International Journal of Earth Sciences, 2016)
Over the last two decades, the flowing fluid electric conductivity (FFEC) logging method has been applied in boreholes in the well-testing mode to evaluate the transmissivity, hydraulic head, and formation water electrical conductivity as a function of depth with a resolution of about 10 –20 cm. FFEC profiles along the borehole are obtained under both shut-in and pumping conditions in a logging procedure that lasts only 3 or 4 days. A method for analyzing these FFEC logs has been developed and successfully employed to obtain formation parameters in a number of field studies. The present paper concerns the analysis of a unique set of FFEC logs that were taken from a deep borehole reaching down to 2.5 km at Outokumpu, Finland, over a 6-year time period. The borehole intersects paleoproterozoic metasedimentary, granitoid, and ophiolite-derived rocks. After the well was drilled, completed, and cleaned up, FFEC logs were obtained after 7, 433, 597, 948, and 2036 days. In analyzing these five profiles, we discovered the need to account for salinity diffusion from water in the formation to the borehole. Analysis results include the identification of 15 hydraulically conducting zones along the borehole, the calculation of flow rates associated with these 15 zones, as well as the estimation of the variation of formation water electrical conductivity as a function of depth. The calculated flow rates were used to obtain the tentative hydraulic conductivity values at these 15 depth levels. © 2015, Springer-Verlag Berlin Heidelberg.
Keywords: Finland; Outokumpu; Pohjois-Karjala; borehole logging; deep drilling; diffusion; electrical conductivity; formation water; hydraulic conductivity; hydraulic structure; monitoring; salinity; well logging

All together now: an international palynological team documents vegetation and climate changes during the last 500 kyr at Lake Ohrid (SE Europe) - Bertini, Adele; Sadori, Laura; Combourieu-Nebout, Nathalie; Donders, Timme H.; Kouli, Katerina; Koutsodendris, Andreas; Joannin, Sebastien; Masi, Alessia; Mercuri, Anna Maria; Panagiotopoulos, Konstantinos; Peyron, Odile; Sinopoli, Gaia; et al. (Alpine and Mediterranean Quaternary, 2016)
Lake Ohrid (Balkan peninsula) is the oldest European extant lake and one of the deepest and largest. Such a unique, terrestrial natural archive is especially relevant for both paleoenvironmental and paleoclimatic reconstructions but also for genetic studies. In the frame of the International Continental Scientific Drilling Program (ICDP), a 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 the summary of palynological analyses carried out in the upper 200 m of the overall 569 m long DEEP site sediment succession from the central part of the lake. These studies, performed by an international palynological team, document the main floristic, vegetation and climate changes during the last ca 500 kyr, at a millennial-scale resolution ( 1.6 kyr). The continuous sediment infill permitted to trace multiple non-forested/ forested phases as a response to Glacial/Interglacial cycles as well as to sub-Milankovitch climate changes. The pollen record, corresponding with marine isotope stages MIS 13 to MIS 1, points to a progressive change from cooler and wetter to warmer and drier interglacials. New palynological studies are underway to reconstruct vegetational and climatic conditions over older intervals as well as to obtain high resolution data for some key intervals such as MIS 5-6, MIS 11-12, MIS 35-42. The complete record of changes in flora composition and vegetation during both glacials and interglacials will furnish indispensable insights for understanding the role of refugia, ecosystem resilience and maintenance of terrestrial biodiversity in the Mediterranean area.

Aligning and synchronization of MIS5 proxy records from Lake Ohrid (FYROM) with independently dated Mediterranean archives: Implications for DEEP core chronology - Zanchetta, Giovanni; Regattieri, Eleonora; Giaccio, Biagio; Wagner, Bernd; Sulpizio, Roberto; Francke, Alex; Vogel, Hendrik; Sadori, Laura; Masi, Alessia; Sinopoli, Gaia; Lacey, Jack H.; Leng, Melanie J.; et al. (Biogeosciences, 2016)
The DEEP site sediment sequence obtained during the ICDP SCOPSCO project at Lake Ohrid was dated using tephrostratigraphic information, cyclostratigraphy, and orbital tuning through the marine isotope stages (MIS) 15-1. Although this approach is suitable for the generation of a general chronological framework of the long succession, it is insufficient to resolve more detailed palaeoclimatological questions, such as leads and lags of climate events between marine and terrestrial records or between different regions. Here, we demonstrate how the use of different tie points can affect cyclostratigraphy and orbital tuning for the period between ca. 140 and 70 ka and how the results can be correlated with directly/indirectly radiometrically dated Mediterranean marine and continental proxy records. The alternative age model presented here shows consistent differences with that initially proposed by Francke et al. (2015) for the same interval, in particular at the level of the MIS6-5e transition. According to this new age model, different proxies from the DEEP site sediment record support an increase of temperatures between glacial to interglacial conditions, which is almost synchronous with a rapid increase in sea surface temperature observed in the western Mediterranean. The results show how a detailed study of independent chronological tie points is important to align different records and to highlight asynchronisms of climate events. Moreover, Francke et al. (2016) have incorporated the new chronology proposed for tephra OH-DP-0499 in the final DEEP age model. This has reduced substantially the chronological discrepancies between the DEEP site age model and the model proposed here for the last glacial-interglacial transition. © 2016 Author(s).
Keywords: Lake Ohrid; Mediterranean Sea; age determination; cyclostratigraphy; glacial-interglacial cycle; marine isotope stage; marine record; Ocean Drilling Program; paleoclimate; proxy climate record; radiometric method; tephra; tephrochronology

Aftershocks triggered by fluid intrusion: Evidence for the aftershock sequence occurred 2014 in West Bohemia/Vogtland - Hainzl, S.; Fischer, T.; Čerm'akov'a, H.; Bachura, M.; Vlček, J. (Journal of Geophysical Research: Solid Earth, 2016)
The West Bohemia/Vogtland region, central Europe, is well known for its repeating swarm activity. However, the latest activity in 2014, although spatially overlapping with previous swarm activity, consisted of three classical aftershock sequences triggered by ML3.5, 4.4, and 3.5 events. To decode the apparent system change from swarm-type to mainshock-aftershock characteristics, we have analyzed the details of the major ML4.4 sequence based on focal mechanisms and relocated earthquake data. Our analysis shows that the mainshock occurred with rotated mechanism in a step over region of the fault plane, unfavorably oriented to the regional stress field. Most of its intense aftershock activity occurred in-plane with classical characteristics such as (i) the maximum magnitude of the aftershocks is significantly less than the mainshock magnitude and (ii) the decay can be well fitted by the Omori-Utsu law. However, the absolute number of aftershocks and the fitted Omori-Utsu c and p parameters are much larger than for typical sequences. By means of the epidemic-type aftershock sequence model, we show that an additional aseismic source with an exponentially decaying strength triggered a large fraction of the aftershocks. Corresponding pore pressure simulations with an exponentially decreasing flow rate of the fluid source show a good agreement with the observed spatial migration front of the aftershocks extending approximately with log(t). Thus, we conclude that the mainshock opened fluid pathways from a finite fluid source into the fault plane explaining the unusual high rate of aftershocks, the migration patterns, and the exponential decrease of the aseismic signal. ©2016. American Geophysical Union. All Rights Reserved.
Keywords: Bohemia; Czech Republic; Germany; Vogtland; aftershock; earthquake magnitude; earthquake swarm; fault plane; focal mechanism; stress field

Advanced seismic imaging techniques characterize the Alpine Fault at Whataroa (New Zealand) - Lay, V.; Buske, S.; Lukacs, A.; Gorman, A.R.; Bannister, S.; Schmitt, D.R. (Journal of Geophysical Research: Solid Earth, 2016)
The plate-bounding Alpine Fault in New Zealand is an 850 km long transpressive continental fault zone that is late in its earthquake cycle. We have acquired and processed reflection seismic data to image the subsurface around the main drill site of the Deep Fault Drilling Project (DFDP-2). The resulting velocity models and seismic images of the upper 5 km show complex subsurface structures around the Alpine Fault zone. The most prominent feature is a strong reflector at depths of 1.5 –2.2 km with an apparent dip of 48° to the southeast below the DFDP-2 borehole, which we assume to be the main trace of the Alpine Fault. Above the main reflector, parallel reflectors suggest the presence of a ∼600 m wide damage zone. Additionally, subparallel reflectors are imaged that we interpret as secondary branches of the main fault zone. Conjugate faults imaged by the data show the complexity of the subsurface. The derived P wave velocity model reveals a 300 –600 m thick sedimentary layer with velocities of ∼2.3 km/s above a schist basement with velocities of 4.5 –5.5 km/s. A low-velocity layer can be observed within the basement at 0.8 –2 km depth. A small-scale low-velocity anomaly appears at the top of the basement that can be correlated to the fault zone. The results provide a reliable basis for a seismic characterization of the DFDP-2 drill site that can be used for further structural and geological investigations of the architecture of the Alpine Fault in this area. ©2016. American Geophysical Union. All Rights Reserved.
cited By 16
Keywords: fault zone; P-wave; prestack migration; seismic data; seismic reflection; seismic tomography; seismic velocity; structural geology; transpression; Alpine Fault Zone; New Zealand; South Island; West Coast [South Island]; Whataroa

A progressively wetter climate in southern East Africa over the past 1.3 million years - Johnson, T.C.; Werne, J.P.; Brown, E.T.; Abbott, A.; Berke, M.; Steinman, B.A.; Halbur, J.; Contreras, S.; Grosshuesch, S.; Deino, A.; Scholz, C.A.; Lyons, R.P.; et al. (Nature, 2016)
African climate is generally considered to have evolved towards progressively drier conditions over the past few million years, with increased variability as glacial-interglacial change intensified worldwide. Palaeoclimate records derived mainly from northern Africa exhibit a 100,000-year (eccentricity) cycle overprinted on a pronounced 20,000-year (precession) beat, driven by orbital forcing of summer insolation, global ice volume and long-lived atmospheric greenhouse gases. Here we present a 1.3-million-year-long climate history from the Lake Malawi basin (10°-14° S in eastern Africa), which displays strong 100,000-year (eccentricity) cycles of temperature and rainfall following the Mid-Pleistocene Transition around 900,000 years ago. Interglacial periods were relatively warm and moist, while ice ages were cool and dry. The Malawi record shows limited evidence for precessional variability, which we attribute to the opposing effects of austral summer insolation and the temporal/spatial pattern of sea surface temperature in the Indian Ocean. The temperature history of the Malawi basin, at least for the past 500,000 years, strongly resembles past changes in atmospheric carbon dioxide and terrigenous dust flux in the tropical Pacific Ocean, but not in global ice volume. Climate in this sector of eastern Africa (unlike northern Africa) evolved from a predominantly arid environment with high-frequency variability to generally wetter conditions with more prolonged wet and dry intervals. © 2016 Macmillan Publishers Limited, part of Springer Nature.
cited By 67
Keywords: carbon dioxide; rain; alkane; calcium; carbon dioxide; dust; ice; rain; wax; arid environment; carbon dioxide; climate conditions; glacial-interglacial cycle; global climate; greenhouse gas; insolation; orbital forcing; paleoclimate; proxy climate record; sea surface temperature; spatiotemporal analysis; terrigenous deposit; Article; climate; climate change; Indian Ocean; interglacial; lake sediment; Malawi; Northern Hemisphere; paleoclimate; priority journal; sea surface temperature; summer; sunlight; thermoregulation; Africa; analysis; atmosphere; chemistry; desert climate; dust; history; lake; plant; plant leaf; season; temperature; East Africa; East African Lakes; Indian Ocean; Lake Malawi; Pacific Ocean; Africa; Eastern; Alkanes; Atmosphere; Calcium; Carbon Dioxide; Climate; Desert Climate; Dust; History; Ancient; Ice; Indian Ocean; Lakes; Malawi; Plant Leaves; Plants; Rain; Seasons; Temperature; Waxes

A microphysical interpretation of rate- and state-dependent friction for fault gouge - Ikari, M.J.; Carpenter, B.M.; Marone, C. (Geochemistry, Geophysics, Geosystems, 2016)
The evolution of fault strength during the seismic cycle plays a key role in the mode of fault slip, nature of earthquake stress drop, and earthquake nucleation. Laboratory-based rate- and state-dependent friction (RSF) laws can describe changes in fault strength during slip, but the connections between fault strength and the mechanisms that dictate the mode of failure, from aseismic creep to earthquake rupture, remain poorly understood. The empirical nature of RSF laws remains a drawback to their application in nature. Here we analyze an extensive data set of friction constitutive parameters with the goal of illuminating the microphysical processes controlling RSF. We document robust relationships between: (1) the initial value of sliding (or kinetic) friction, (2) RSF parameters, and (3) the time rates of frictional strengthening (aging). We derive a microphysical model based on asperity contact mechanics and show that these relationships are dictated by: (1) an activation energy that controls the rate of asperity growth by plastic creep, and (2) an inverse relationship between material hardness and the activation volume of plastic deformation. Collectively, our results illuminate the physics expressed by the RSF parameters, and which describe the absolute value of frictional strength and its dependence on time and slip rate. Moreover, we demonstrate that seismogenic fault behavior may be dictated by the interplay between grain properties and ambient conditions controlling the local shear strength of grain-scale asperity contacts. © 2016. American Geophysical Union. All Rights Reserved.
cited By 64
Keywords: Activation energy; Chemical activation; Creep; Deformation; Earthquakes; Faulting; Friction; Geophysics; Shear strength; Tribology; Ambient conditions; Constitutive parameters; Earthquake nucleation; Frictional strength; Inverse relationship; Microphysical models; Microphysical process; Seismogenic faults; Fault slips; asperity; creep; earthquake mechanism; earthquake rupture; fault gouge; fault slip; fault zone; plastic deformation; shear strength; tectonic evolution; tectonic setting

A high-resolution mid-Pleistocene temperature record from Arctic Lake El'gygytgyn: A 50 kyr super interglacial from MIS 33 to MIS 31? - Wet, G.A.; Castañeda, I.S.; DeConto, R.M.; Brigham-Grette, J. (Earth and Planetary Science Letters, 2016)
Previous periods of extreme warmth in Earth's history are of great interest in light of current and predicted anthropogenic warming. Numerous so called super interglacial intervals, with summer temperatures significantly warmer than today, have been identified in the 3.6 million year (Ma) sediment record from Lake El'gygytgyn, northeast Russia. To date, however, a high-resolution paleotemperature reconstruction from any of these super interglacials is lacking. Here we present a paleotemperature reconstruction based on branched glycerol dialkyl glycerol tetraethers (brGDGTs) from Marine Isotope Stages (MIS) 35 to MIS 29, including super interglacial MIS 31. To investigate this period in detail, samples were analyzed with an unprecedented average sample resolution of 500 yrs from MIS 33 to MIS 30. Our results suggest the entire period currently defined as MIS 33-31 ( 1114-1062 kyr BP) was characterized by generally warm and highly variable conditions at the lake, at times out of phase with Northern Hemisphere summer insolation, and that cold glacial conditions during MIS 32 lasted only a few thousand years. Close similarities are seen with coeval records from high southern latitudes, supporting the suggestion that the interval from MIS 33 to MIS 31 was an exceptionally long interglacial (Teitler et al., 2015). Based on brGDGT temperatures from Lake El'gygytgyn (this study and unpublished results), warming in the western Arctic during MIS 31 was matched only by MIS 11 during the Pleistocene. © 2016 Elsevier B.V.
cited By 22
Keywords: Glacial geology; Glycerol; Isotopes; Arctic; Branched GDGT; Marine isotope stages; Paleoclimatology; Super interglacial; Lakes; interglacial; marine isotope stage; Northern Hemisphere; paleoclimate; paleotemperature; Pleistocene; Arctic; Chukchi; Elgygytgyn Lake; Russian Federation

Late Cretaceous marine fossils and seawater incursion events in the Songliao Basin, NE China - Xi, D.; Cao, W.; Huang, Q.; Do Carmo, D.A.; Li, S.; Jing, X.; Tu, Y.; Jia, J.; Qu, H.; Zhao, J.; Wan, X. (Cretaceous Research, 2016)
The Songliao Basin is the largest non-marine oil-bearing basin in China. Because of the absence of substantial evidence, the hypothesis of seawater incursion events into the Songliao Basin remains controversial. The presence of marine fossils could provide direct proof to support this supposition. Here, we report new discoveries of foraminifera, calcareous nannofossils, brackish dinoflagellates, and other marine and brackish-water fossils to support the suggestion of seawater incursion events in the Songliao Basin. Relatively abundant benthic and planktonic foraminifera, calcareous nannofossils, marine and brackish-water dinoflagellates, fish, and bivalves have been discovered in Members 1 and 2 of the Nenjiang Formation, a few foraminifera and brackish-water dinoflagellates have been found in the lower Qingshankou Formation, and just a few brackish-water bivalves have been found in the uppermost Qingshankou Fm. Based on the presence of marine molecular fossils and other evidence, we suggest that relatively large seawater incursion events occurred during the sedimentation of the lower Nenjiang Fm., relatively smaller seawater incursions occurred during the deposition of the lower Qingshankou Fm., and possibly a very small seawater incursion occurred during the sedimentation of the uppermost Qingshankou Fm. These seawater incursion events in the Songliao Basin were controlled by regional tectonic activity, evolution of the palaeo Songliao Lake, and global sea level change. These periodic seawater incursions brought marine biota into the palaeo Songliao Lake. © 2015 Elsevier Ltd.
cited By 40
Keywords: biostratigraphy; bivalve; Cretaceous; dinoflagellate; fish; foraminifera; lacustrine environment; nanofossil; paleoenvironment; seawater; China; Songliao Basin; Bivalvia; Dinophyceae; Foraminifera

3D reflection seismic imaging at the 2.5km deep COSC-1 scientific borehole, central Scandinavian Caledonides - Hedin, Peter; Almqvist, Bjarne; Berthet, Th'eo; Juhlin, Christopher; Simon, Helge; Giese, R{udiger; Krau{s, Felix; Rosberg, Jan-Erik; Alm, Per-Gunnar (Tectonophysics, 2016)

15 Years of Hardship and Struggle History and the Prospects for the Future of the Chinese Continental Scientific Drilling Program(CCSD):In Memory of the 15 Year Anniversary of CCSD and 20 Year Anniversary of ICDP (in Chinese with English abstract);[中国大陆科学钻探的过去、现在和未来––纪念中国大陆科学钻探实施15周年、国际大陆科学钻探委员会成立20周年] - Xu, Z.; Yang, W.; Yang, J.; An, Z.; Wang, C.; Li, H.; Liu, J.; Su, D.; He, B.; Wang, D.; Zhang, W.; Zhang, X. (Acta Geologica Sinica, 2016)

Design of electro-hydraulic control and auxiliary monitoring system of coring winch for drilling of 6000 m (in Chinese with English abstract);[6000m用取心绞车电液控制及辅助监测系统设计] - Hu, Y.; Yu, X.; Zhang, H.; Zhu, X.; Xiang, M. (Mining & Processing Equipment, 2016)

A 400-ka tephrochronological framework for Central America from Lake Pet'en Itz'a (Guatemala) sediments - Kutterolf, S.; Schindlbeck, J.C.; Anselmetti, F.S.; Ariztegui, D.; Brenner, M.; Curtis, J.; Schmid, D.; Hodell, D.A.; Mueller, A.; P'erez, L.; P'erez, W.; Schwalb, A.; et al. (Quaternary Science Reviews, 2016)
Lake Pet'en Itz'a, northern Guatemala, lies within a hydrologically closed basin in the south-central area of the Yucat'an Peninsula, and was drilled under the auspices of the International Continental Scientific Drilling Program (ICDP) in 2006. At 16°55′N latitude, the lake is ideally located for study of past climate and environmental conditions in the Neotropical lowlands. Because of its great depth (>160 m), Lake Pet'en Itz'a has a record of continuous sediment accumulation that extends well into the late Pleistocene. A key obstacle to obtaining long climate records from the region is the difficulty of establishing a robust chronology beyond ∼40 ka, the limit of 14C dating. Tephra layers within the Lake Pet'en Itz'a sediments, however, enable development of age/depth relations beyond 40 ka. Ash beds from large-magnitude, Pleistocene-to-Holocene silicic eruptions of caldera volcanoes along the Central American Volcanic Arc (CAVA) were found throughout drill cores collected from Lake Pet'en Itz'a. These ash beds were used to establish a robust chronology extending back 400 ka. We used major- and trace-element glass composition to establish 12 well-constrained correlations between the lacustrine tephra layers in Lake Pet'en Itz'a sediments and dated deposits at the CAVA source volcanoes, and with their marine equivalents in eastern Pacific Ocean sediments. The data also enabled revision of eight previous determinations of erupted volumes and masses, and initial estimates for another four eruptions, as well as the designation of source areas for 14 previously unknown eruptions. The new and revised sedimentation rates for the older sediment successions identify the interglacial of MIS5a between 84 and 72 ka, followed by a stadial between 72 and 59 ka that corresponds to MIS4. We modified the age models for the Lake Pet'en Itz'a sediment sequences, extended the paleoclimate and paleoecological record for this Neotropical region to ∼400 ka, and determined the magnitude and timing of CAVA eruptions. © 2016 Elsevier Ltd
Keywords: Guatemala [Central America]; Lake Peten Itza; Pacific Ocean; Pacific Ocean (East); Peten; Yucatan Peninsula; Sediments; Trace elements; Volcanoes; CAVA; Explosive volcanism; ICDP; Paleoclimates; Tephrochronology; caldera; drilling; explosive volcanism; island arc; lowland environment; Neotropical Region; paleoclimate; Pleistocene; sediment analysis; sedimentation; tephrochronology; volcanic eruption; Lakes

Drilling fluid technology applied in a large hole of the second spudding of the scientific drilling well in the Songliao basin (in Chinese with English abstract); [松辽盆地大陆科钻二开段大井眼钻井液技术] - Zheng, W.; Wu, X.; Huang, Y.; Wang, W.; Wu, D.; Huang, H. (Geology and Exploration, 2016)

Grain size of Lake Qinghai sediments: Implications for riverine input and Holocene monsoon variability - Liu, Xingxing; Vandenberghe, Jef; An, ZhiSheng; Li, Ying; Jin, Zhangdong; Dong, Jibao; Sun, Youbin (Palaeogeography, Palaeoclimatology, Palaeoecology, 2016)
Grain-size compositions of lake sediments can provide direct information on changes in transporting mechanism and sedimentary environment. Various grain-size parameters have been employed to reconstruct hydrological conditions within the lake and dust influx from outside the lake. Here we present the grain-size results of a 5-m core retrieved from Lake Qinghai, northeastern Tibetan Plateau in order to address the links between Holocene depositional process and climatic change. Our results indicate that two parameters (skewness and grain-size ratio of 8-50/2-8 μm) are sensitive to hydrodynamic changes in Lake Qinghai, which are further linked to the strength of the Asian summer monsoon. Variations of these two parameters reveal that summer monsoon intensity weakened gradually from early to late Holocene, superimposed by persistent centennial variability with dominant periods at 0.35, 0.23 and 0.12 kyr. Comparison of grain-size variations with solar activities and North Atlantic cooling events reveals that solar forcing likely plays an important role in driving centennial monsoon variability. © 2016 Elsevier B.V.
Keywords: Atlantic Ocean; Atlantic Ocean (North); China; Qinghai; Qinghai Lake; climate change; depositional environment; grain size; Holocene; hydrodynamics; lacustrine deposit; monsoon; reconstruction; solar activity

Earthquake impact on iron isotope signatures recorded in mineral spring water - Schuessler, Jan A.; K{ampf, Horst; Koch, Ulrich; Alawi, Mashal (Journal of Geophysical Research: Solid Earth, 2016)
We investigated the iron isotope signatures of dissolved Fe in the water of the Wettinquelle mineral spring (Bad Brambach, Germany) by time series sampling covering seismically active periods related to tectonic activity near the Eger Rift system in central Europe. Our objective was to test whether Fe isotopes trace earthquake-induced abiotic and biotic changes in the fluid/rock interaction of the deep, fissured, granitic aquifer. We found that the dissolved Fe isotope signatures in spring water are distinct from the granitic source signature (δ56Fe = +0.09‰). Particularly, we discovered that water δ56Fe values are remarkably stable (−0.01 ± 0.11‰, 2SD, n = 4) before and during a strong seismic swarm period in 2000 (local magnitudes ML > 3), while O2 and H2 concentrations in water decrease and dissolved Fe content increases. Later, recurring events of lower δ56Fe values down to −0.3‰ are observed in the period from 2001 to 2003 with intermittent seismic events (1 < ML < 3.2). The observations indicate a time lag between tectonic forcing and Fe isotope response. The role of abiotic fluid/rock interaction and Fe-utilizing bacteria identified in the mineral spring water on Fe isotope fractionation is discussed. We explain recurring changes toward isotopically lighter values by a combination of Fe dissolution from deep granite and admixture of isotopically light Fe generated by a complex combination of abiotic and biotic processes operating in the aquifer when disturbed by swarm earthquakes events. We propose a conceptual model scenario of earthquake-triggered changes in biogeochemical processes. ©2016. American Geophysical Union. All Rights Reserved.
Keywords: Central Europe; Germany; aquifer; biochemistry; earthquake swarm; iron; isotopic fractionation; spring water; time series analysis

Large-displacement, hydrothermal frictional properties of DFDP-1 fault rocks, Alpine Fault, New Zealand: Implications for deep rupture propagation - Niemeijer, A.R.; Boulton, C.; Toy, V.G.; Townend, J.; Sutherland, R. (Journal of Geophysical Research: Solid Earth, 2016)
The Alpine Fault, New Zealand, is a major plate-bounding fault that accommodates 65-75% of the total relative motion between the Australian and Pacific plates. Here we present data on the hydrothermal frictional properties of Alpine Fault rocks that surround the principal slip zones (PSZ) of the Alpine Fault and those comprising the PSZ itself. The samples were retrieved from relatively shallow depths during phase 1 of the Deep Fault Drilling Project (DFDP-1) at Gaunt Creek. Simulated fault gouges were sheared at temperatures of 25, 150, 300, 450, and 600°C in order to determine the friction coefficient as well as the velocity dependence of friction. Friction remains more or less constant with changes in temperature, but a transition from velocity-strengthening behavior to velocity-weakening behavior occurs at a temperature of T = 150°C. The transition depends on the absolute value of sliding velocity as well as temperature, with the velocity-weakening region restricted to higher velocity for higher temperatures. Friction was substantially lower for low-velocity shearing (V < 0.3 μm/s) at 600°C, but no transition to normal stress independence was observed. In the framework of rate-and-state friction, earthquake nucleation is most likely at an intermediate temperature of T = 300°C. The velocity-strengthening nature of the Alpine Fault rocks at higher temperatures may pose a barrier for rupture propagation to deeper levels, limiting the possible depth extent of large earthquakes. Our results highlight the importance of strain rate in controlling frictional behavior under conditions spanning the classical brittle-plastic transition for quartzofeldspathic compositions. ©2016. The Authors.
cited By 34
Keywords: earthquake rupture; fault; fault displacement; fault gouge; friction; hydrothermal system; plate tectonics; strain rate; Alpine Fault Zone; New Zealand; South Island

Integration of geophysical data for deep exploration in the kylylahti cu-mining area, eastern Finland - Heinonen, S.; Kontinen, A.; Sorjonen-Ward, P.; Aatos, S. (EAGE/DGG Workshop on Deep Mineral Exploration 2016: Chasing Both Land and Sea Deposits, 2016)
The Kylylahti copper mine is located in the Outokumpu Cu-Co-Zn-Ni ore district in eastern Finland. We used high resolution reflection seismic profiles imaging the subsurface structures down to depth of 5 km and ZTEM (Z-axis Tipper Electromagnetic) inversion results revealing deep conductivity anomalies to study the deep exploration potential of the Kylylahti area. Regional interpretation of these deep penetrating data suggest that peridotite body of Kylylahti has substantial down plunge extend towards south and underneath the current mine. Additionally to regional interpretation, we have interpolated the densities measured in laboratory from drill-core samples to create a 3D-subsurface density distribution grid and compared it with the seismic reflection data. Overall correlation of reflectivity and density patterns is excellent: high density values correlate particularly well with high amplitude reflections while no prominent reflectivity is observed in the areas where density is uniformly low. The combination of reflectivity and interpolated density distribution suggest that the high density rock units possibly hosting the sulfide ore occur in a steeply dipping feature continuing northwest from the Kylylahti mine along the seismic profile. Results of this study highlight the deep exploration potential of the rock volumes below currently drilled depths in the Kylylahti area.
Keywords: Cobalt alloys; Copper alloys; Copper mines; Core drilling; Deposits; Infill drilling; Potassium alloys; Reflection; Seismic waves; Seismology; Sulfur compounds; Zinc alloys; Conductivity anomalies; Density distributions; Exploration potential; High resolution reflection seismic; Inversion results; Seismic reflection data; Subsurface density; Subsurface structures; Mineral exploration

Improved end-member characterisation of modern organic matter pools in the Ohrid Basin (Albania, Macedonia) and evaluation of new palaeoenvironmental proxies - Holtvoeth, J.; Rushworth, D.; Copsey, H.; Imeri, A.; Cara, M.; Vogel, H.; Wagner, T.; Wolff, G.A. (Biogeosciences, 2016)
We present elemental, lipid biomarker and, in the supplement, compound-specific isotope (δ13C, δ2H) data for soils and leaf litter collected in the catchment of Lake Ohrid (Albania, Macedonia), as well as macrophytes, particulate organic matter and sediments from the lake itself. Lake Ohrid provides an outstanding archive of continental environmental change of at least 1.2 million years and the purpose of our study is to ground truth organic geochemical proxies that we developed in order to study past changes in the terrestrial biome. We show that soils dominate the lipid signal of the lake sediments rather than the vegetation or aquatic biomass. There is a strong imprint of suberin monomers on the composition of total lipid extracts and chain-length distributions of n-alkanoic acids, n-alcohols, ω-hydroxy acids and α, ω-dicarboxylic acids. Our end-member survey identifies that ratios of mid-chain length suberin-derived to long-chain length cuticular-derived alkyl compounds as well as their average chain length distributions can be used as new molecular proxies of organic matter sources to the lake. We tested these for the 8.2 ka event, a pronounced and widespread Holocene climate fluctuation. In SE Europe climate became drier and cooler in response to the event, as is clearly recognisable in the carbonate and organic carbon records of Lake Ohrid sediments. Our new proxies indicate biome modification in response to hydrological changes, identifying two phases of increased soil organic matter (OM) supply, first from soils with moderately degraded OM and then from more degraded soils. Our study demonstrates that geochemical fingerprinting of terrestrial OM should focus on the main lipid sources, rather than the living biomass. Both can exhibit climate-controlled variability, but are generally not identical. © Author(s) 2016.
Keywords: Albania; Lake Ohrid; Macedonia [Southern Europe]; biomarker; biome; catchment; climate effect; environmental change; geochemistry; Holocene; inorganic carbon; leaf litter; paleoenvironment; sediment analysis; soil organic matter; vegetation history

Implications of structural inheritance in oblique rift zones for basin compartmentalization: Nkhata Basin, Malawi Rift (EARS) - Mortimer, E.J.; Paton, D.A.; Scholz, C.A.; Strecker, M.R. (Marine and Petroleum Geology, 2016)
The Cenozoic East African Rift System (EARS) is an exceptional example of active continental extension, providing opportunities for furthering our understanding of hydrocarbon plays within rifts. It is divided into structurally distinct western and eastern branches. The western branch comprises deep rift basins separated by transfer zones, commonly localised onto pre-existing structures, offering good regional scale hydrocarbon traps. At a basin-scale, local discrete inherited structures might also play an important role on fault localisation and hydrocarbon distribution. Here, we consider the evolution of the Central basin of the Malawi Rift, in particular the influence of pre-existing structural fabrics.Integrating basin-scale multichannel 2D, and high resolution seismic datasets we constrain the border, Mlowe-Nkhata, fault system (MNF) to the west of the basin and smaller Mbamba fault (MF) to the east and document their evolution. Intra basin structures define a series of horsts, which initiated as convergent transfers, along the basin axis. The horsts are offset along a NE-SW striking transfer fault parallel to and along strike of the onshore Karoo (Permo-Triassic) Ruhuhu graben. Discrete pre-existing structures probably determined its location and, oriented obliquely to the extension orientation it accommodated predominantly strike-slip deformation, with more slowly accrued dip-slip.To the north of this transfer fault, the overall basin architecture is asymmetric, thickening to the west throughout; while to the south, an initially symmetric graben architecture became increasingly asymmetric in sediment distribution as strain localised onto the western MNF. The presence of the axial horst increasingly focussed sediment supply to the west. As the transfer fault increased its displacement, so this axial supply was interrupted, effectively starving the south-east while ponding sediments between the western horst margin and the transfer fault. This asymmetric bathymetry and partitioned sedimentation continues to the present-day, overprinting the early basin symmetry and configuration. Sediments deposited earlier become increasingly dissected and fault juxtapositions changed at a small (10-100 m) scale. The observed influence of basin-scale transfer faults on sediment dispersal and fault compartmentalization due to pre-existing structures oblique to the extension orientation is relevant to analogous exploration settings. © 2016 Elsevier Ltd.
cited By 21
Keywords: Geologic models; Hydrocarbons; Sediments; Strike-slip faults; East African Rift; Existing structure; High resolution seismic; Hydrocarbon distribution; Normal faults; Sediment distribution; Strike-slip deformation; Structural inheritance; Fault slips; basin evolution; compartmentalization; deformation; extensional tectonics; hydrocarbon; normal fault; rift zone; sediment transport; strike-slip fault; East African Rift

Impact processes, permafrost dynamics, and climate and environmental variability in the terrestrial Arctic as inferred from the unique 3.6 Myr record of Lake El'gygytgyn, Far East Russia – A review - Wennrich, V.; Andreev, A.A.; Tarasov, P.E.; Fedorov, G.; Zhao, W.; Gebhardt, C.A.; Meyer-Jacob, C.; Snyder, J.A.; Nowaczyk, N.R.; Schwamborn, G.; Chapligin, B.; Anderson, P.M.; et al. (Quaternary Science Reviews, 2016)
Lake El'gygytgyn in Far East Russia is a 3.6 Myr old impact crater lake. Located in an area that has never been affected by Cenozoic glaciations nor desiccation, the unique sediment record of the lake represents the longest continuous sediment archive of the terrestrial Arctic. The surrounding crater is the only impact structure on Earth developed in mostly acid volcanic rocks. Recent studies on the impactite, permafrost, and sediment sequences recovered within the framework of the ICDP “El'gygytgyn Drilling Project” and multiple pre-site surveys yielded new insight into the bedrock origin and cratering processes as well as permafrost dynamics and the climate and environmental history of the terrestrial Arctic back to the mid-Pliocene. Results from the impact rock section recovered during the deep drilling clearly confirm the impact genesis of the El'gygytgyn crater, but indicate an only very reduced fallback impactite sequence without larger coherent melt bodies. Isotope and element data of impact melt samples indicate a F-type asteroid of mixed composition or an ordinary chondrite as the likely impactor. The impact event caused a long-lasting hydrothermal activity in the crater that is assumed to have persisted for c. 300 kyr. Geochemical and microbial analyses of the permafrost core indicate a subaquatic formation of the lower part during lake-level highstand, but a subaerial genesis of the upper part after a lake-level drop after the Allerød. The isotope signal and ion compositions of ground ice is overprinted by several thaw-freeze cycles due to variations in the talik underneath the lake. Modeling results suggest a modern permafrost thickness in the crater of c. 340 m, and further confirm a pervasive character of the talik below Lake El'gygytgyn. The lake sediment sequences shed new leight into the Pliocene and Pleistocene climate and environmental evolution of the Arctic. During the mid-Pliocene, significantly warmer and wetter climatic conditions in western Beringia than today enabled dense boreal forests to grow around Lake El'gygytgyn and, in combination with a higher nutrient flux into the lake, promoted primary production. The exceptional warmth during the mid-Pliocene is in accordance with other marine and terrestrial records from the Arctic and indicates a period of enhanced “Arctic amplification”. The favourable conditions during the mid-Pliocene were repeatedly interrupted by climate deteriorations, e.g., during Marine Isotope Stage (MIS) M2, when pollen data and sediment proxies indicate a major cooling and the onset of local permafrost around the lake. A gradual vegetation change after c. 3.0 Ma points to the onset of a long-term cooling trend during the Late Pliocene that culminated in major temperature drops, first during MIS G6, and later during MIS 104. These cold events coincide with the onset of an intensified Northern Hemisphere (NH) glaciation and the largest extent of the Cordilleran Ice Sheet, respectively. After the Pliocene/Pleistocene transition, local vegetation and primary production in Lake El'gygtygyn experienced a major change from relatively uniform conditions to a high-amplitude glacial-to-interglacial cyclicity that fluctuated on a dominant 41 kyr obliquity band, but changed to a 100 kyr eccentricity dominance during the Middle Pleistocene transition (MPT) at c. 1.2 –0.6 Ma. Periods of exceptional warming in the Pleistocene record of Lake El'gygytgyn with dense boreal forests around and peaks of primary production in the lake are assigned to so-called “super-interglacial” periods. The occurrence of these super-interglacials well corresponds to collapses of the West Antarctic Ice Sheet (WAIS) recorded in ice-free periods in the ANDRILL core, which suggests strong intrahemispheric teleconnections presumably driven by changes in the thermocline ocean circulation. © 2016 Elsevier Ltd
cited By 23
Keywords: Amplification; Climate change; Drops; Dynamics; Fluorine; Forestry; Glacial geology; Glaciers; Ice; Isotopes; Permafrost; Rock drilling; Sediments; Structural geology; Vegetation; Volcanic rocks; Environmental evolution; Environmental variability; ICDP; Interglacial cyclicity; Interglacials; Mid-Pliocene; Pliocene; West antarctic ice sheets; Lakes; arctic environment; Beringia; climate variation; Cordilleran Ice Sheet; crater lake; environmental change; glacial-interglacial cycle; historical ecology; isotopic analysis; marine isotope stage; nutrient dynamics; paleoenvironment; permafrost; Pliocene-Pleistocene boundary; vegetation dynamics; warming; Chukchi; Elgygytgyn Lake; Russian Federation

Hydrothermal frictional strengths of rock and mineral samples relevant to the creeping section of the San Andreas Fault - Moore, D.E.; Lockner, D.A.; Hickman, S. (Journal of Structural Geology, 2016)
We compare frictional strengths in the temperature range 25-250 °C of fault gouge from SAFOD (CDZ and SDZ) with quartzofeldspathic wall rocks typical of the central creeping section of the San Andreas Fault (Great Valley sequence and Franciscan Complex). The Great Valley and Franciscan samples have coefficients of friction, μ > 0.35 at all experimental conditions. Strength is unchanged between 25° and 150 °C, but μ increases at higher temperatures, exceeding 0.50 at 250 °C. Both samples are velocity strengthening at room temperature but show velocity-weakening behavior beginning at 150 °C and stick-slip motion at 250 °C. These rocks, therefore, have the potential for unstable seismic slip at depth. The CDZ gouge, with a high saponite content, is weak (μ = 0.09-0.17) and velocity strengthening in all experiments, and μ decreases at temperatures above 150 °C. Behavior of the SDZ is intermediate between the CDZ and wall rocks: μ < 0.2 and does not vary with temperature. Although saponite is probably not stable at depths greater than 3 km, substitution of the frictionally similar minerals talc and Mg-rich chlorite for saponite at higher temperatures could potentially extend the range of low strength and stable slip down to the base of the seismogenic zone. © 2016.
cited By 25
Keywords: Landforms; Rocks; Slip forming; Stick-slip; Strike-slip faults; Franciscan Complex; Frictional strength; Great Valley sequence; SAFOD; San Andreas fault; Saponite; Minerals; creep; fault gouge; friction; rock; San Andreas Fault; saponite; seismic zone; slip; strength; strike-slip fault; temperature; California; Central Valley [California]; United States

Hydrologic testing during drilling: application of the flowing fluid electrical conductivity (FFEC) logging method to drilling of a deep borehole - Tsang, Chin-Fu; Rosberg, Jan-Erik; Sharma, Prabhakar; Berthet, Th'eo; Juhlin, Christopher; Niemi, Auli (Hydrogeology Journal, 2016)
Drilling of a deep borehole does not normally allow for hydrologic testing during the drilling period. It is only done when drilling experiences a large loss (or high return) of drilling fluid due to penetration of a large-transmissivity zone. The paper proposes the possibility of conducting flowing fluid electrical conductivity (FFEC) logging during the drilling period, with negligible impact on the drilling schedule, yet providing important information on depth locations of both high- and low-transmissivity zones and their hydraulic properties. The information can be used to guide downhole fluid sampling and post-drilling detailed testing of the borehole. The method has been applied to the drilling of a 2,500-m borehole at Åre, central Sweden, firstly when the drilling reached 1,600 m, and then when the drilling reached the target depth of 2,500 m. Results unveil eight hydraulically active zones from 300 m down to borehole bottom, with depths determined to within the order of a meter. Further, the first set of data allows the estimation of hydraulic transmissivity values of the six hydraulically conductive zones found from 300 to 1,600 m, which are very low and range over one order of magnitude.

Hydrogen utilization potential in subsurface sediments - Adhikari, R.R.; Glombitza, C.; Nickel, J.C.; Anderson, C.H.; Dunlea, A.G.; Spivack, A.J.; Murray, R.W.; D'Hondt, S.; Kallmeyer, J. (Frontiers in Microbiology, 2016)
Subsurface microbial communities undertake many terminal electron-accepting processes, often simultaneously. Using a tritium-based assay, we measured the potential hydrogen oxidation catalyzed by hydrogenase enzymes in several subsurface sedimentary environments (Lake Van, Barents Sea, Equatorial Pacific, and Gulf of Mexico) with different predominant electron-acceptors. Hydrogenases constitute a diverse family of enzymes expressed by microorganisms that utilize molecular hydrogen as a metabolic substrate, product, or intermediate. The assay reveals the potential for utilizing molecular hydrogen and allows qualitative detection of microbial activity irrespective of the predominant electron-accepting process. Because the method only requires samples frozen immediately after recovery, the assay can be used for identifying microbial activity in subsurface ecosystems without the need to preserve live material. We measured potential hydrogen oxidation rates in all samples from multiple depths at several sites that collectively span a wide range of environmental conditions and biogeochemical zones. Potential activity normalized to total cell abundance ranges over five orders of magnitude and varies, dependent upon the predominant terminal electron acceptor. Lowest per-cell potential rates characterize the zone of nitrate reduction and highest per-cell potential rates occur in the methanogenic zone. Possible reasons for this relationship to predominant electron acceptor include (i) increasing importance of fermentation in successively deeper biogeochemical zones and (ii) adaptation of H2ases to successively higher concentrations of H2 in successively deeper zones. © 2016 Adhikari, Glombitza, Nickel, Anderson, Dunlea, Spivack, Murray, D'Hondt and Kallmeyer.
cited By 14
Keywords: hydrogen; hydrogenase; iron; manganese; sulfate; Article; ecosystem; enzyme assay; Gulf of Mexico; metabolic activity assay; microbial activity; microbial community; nonhuman; Pacific Ocean; radioactivity; sediment; temperature; Turkey (republic); water analysis

Hydroclimatic variability in the Levant during the early last glacial ( ∼ 117-75 ka) derived from micro-facies analyses of deep Dead Sea sediments - Neugebauer, I.; Schwab, M.J.; Waldmann, N.D.; Tjallingii, R.; Frank, U.; Hadzhiivanova, E.; Naumann, R.; Taha, N.; Agnon, A.; Enzel, Y.; Brauer, A. (Climate of the Past, 2016)
The new sediment record from the deep Dead Sea basin (ICDP core 5017-1) provides a unique archive for hydroclimatic variability in the Levant. Here, we present highresolution sediment facies analysis and elemental composition by micro-X-ray fluorescence (ìXRF) scanning of core 5017-1 to trace lake levels and responses of the regional hydroclimatology during the time interval from ca. 117 to 75 ka, i.e. the transition between the last interglacial and the onset of the last glaciation. We distinguished six major micro-facies types and interpreted these and their alterations in the core in terms of relative lake level changes. The two end-member facies for highest and lowest lake levels are (a) up to several metres thick, greenish sediments of alternating aragonite and detrital marl laminae (aad) and (b) thick halite facies, respectively. Intermediate lake levels are characterised by detrital marls with varying amounts of aragonite, gypsum or halite, reflecting lower-amplitude, shorter-term variability. Two intervals of pronounced lake level drops occurred at ∼110-1085 and ∼93-87±7 ka. They likely coincide with stadial conditions in the central Mediterranean (Melisey I and II pollen zones in Monticchio) and low global sea levels during Marine Isotope Stage (MIS) 5d and 5b. However, our data do not support the current hypothesis of an almost complete desiccation of the Dead Sea during the earlier of these lake level low stands based on a recovered gravel layer. Based on new petrographic analyses, we propose that, although it was a low stand, this well-sorted gravel layer may be a vestige of a thick turbidite that has been washed out during drilling rather than an in situ beach deposit. Two intervals of higher lake stands at ∼108-93±6 and ∼87-75±7 ka correspond to interstadial conditions in the central Mediterranean, i.e. pollen zones St. Germain I and II in Monticchio, and Greenland interstadials (GI) 24C23 and 21 in Greenland, as well as to sapropels S4 and S3 in the Mediterranean Sea. These apparent correlations suggest a close link of the climate in the Levant to North Atlantic and Mediterranean climates during the time of the build-up of Northern Hemisphere ice shields in the early last glacial period. © 2016 Author(s).
cited By 28
Keywords: climate variation; core analysis; deep-sea sediment; interstadial; lake level; Last Glacial; last glaciation; Last Interglacial; marine isotope stage; marl; microfacies; Northern Hemisphere; petrography; sapropel; turbidite; Arctic; Atlantic Ocean; Atlantic Ocean (North); Dead Sea; Greenland; Levant; Mediterranean Region; Mediterranean Sea

High-precision U-Pb geochronologic constraints on the Late Cretaceous terrestrial cyclostratigraphy and geomagnetic polarity from the Songliao Basin, Northeast China - Wang, T.; Ramezani, J.; Wang, C.; Wu, H.; He, H.; Bowring, S.A. (Earth and Planetary Science Letters, 2016)
The Cretaceous continental sedimentary records are essential to our understanding of how the terrestrial geologic and ecologic systems responded to past climate fluctuations under greenhouse conditions and our ability to forecast climate change in the future. The Songliao Basin of Northeast China preserves a near-complete, predominantly lacustrine, Cretaceous succession, with sedimentary cyclicity that has been tied to Milankocitch forcing of the climate. Over 900 meters of drill-core recovered from the Upper Cretaceous (Turonian to Campanian) of the Songliao Basin has provided a unique opportunity for detailed analyses of its depositional and paleoenvironmental records through integrated and high-resolution cyclostratigraphic, magnetostratigraphic and geochronologic investigations.Here we report high-precision U-Pb zircon dates (CA-ID-TIMS method) from four interbedded bentonites from the drill-core that offer substantial improvements in accuracy, and a ten-fold enhancement in precision, compared to the previous U-Pb SIMS geochronology, and allow a critical evaluation of the Songliao astrochronological time scale. The results indicate appreciable deviations of the astrochronologic model from the absolute radioisotope geochronology, which more likely reflect cyclostratigraphic tuning inaccuracies and omitted cycles due to depositional hiatuses, rather than suspected limitations of astronomical models applied to distant geologic time.Age interpolation based on our new high-resolution geochronologic framework and the calibrated cyclostratigraphy places the end of the Cretaceous Normal Superchon (C34n-C33r chron boundary) in the Songliao Basin at 83.07. ±. 0.15 Ma. This date also serves as a new and improved estimate for the global Santonian-Campanian stage boundary. © 2016 Elsevier B.V.
cited By 65
Keywords: Climate change; Core drilling; Deposition; Drills; Geologic models; Geomagnetism; Sedimentology; Silicate minerals; China; Cyclostratigraphy; Magnetostratigraphy; Santonian-Campanian boundary; Songliao basin; U-Pb geochronology; Geochronology; Cretaceous; cyclostratigraphy; geochronology; magnetic reversal; magnetostratigraphy; uranium-lead dating; China; Songliao Basin

High elevation of Jiaolai Basin during the Late Cretaceous: Implication for the coastal mountains along the East Asian margin - Zhang, L.; Wang, C.; Cao, K.; Wang, Q.; Tan, J.; Gao, Y. (Earth and Planetary Science Letters, 2016)
A large body of evidence suggests that there were extensive coastal mountains along the East Asian margin during the Late Cretaceous. However, current knowledge of the paleo-mountains – the period, range, and elevation – is limited. Therefore, direct paleoaltimetry is needed to validate and evaluate the paleo-mountains in East Asia. Our study area is Jiaolai Basin, which is located at the East Asian continental margin. We estimate the paleoelevation of Jiaolai Basin during the Late Cretaceous using carbonate clumped isotope paleothermometry. After correcting for seasonal preference, latitudinal difference, and secular climate change, we conclude that the paleoelevation of Jiaolai Basin was almost certainly ≥2.0 km at ∼80 Ma. Combined with the evidence from stratigraphy, paleogeography, and paleoclimatology, our results suggest that the existence of coastal mountains along East Asia during the Late Cretaceous is likely and the model of Okhotomorsk –East Asia collision is preferred. © 2016 Elsevier B.V.
cited By 66
Keywords: Climate change; Isotopes; Stratigraphy; Clumped isotopes; coastal mountains; East Asia; Jiaolai Basin; Late cretaceous; Paleoelevation; Landforms; continental margin; Cretaceous; elevation; paleoclimate; paleogeography; stratigraphy; China; Jiaolai Basin; Shandong

Heat flow pattern at the Chicxulub impact crater, northern Yucatan, Mexico - Espinosa-Cardeña, J.M.; Campos-Enr'iquez, J.O.; Unsworth, M. (Journal of Volcanology and Geothermal Research, 2016)
Along an east-west profile crossing the Chicxulub impact structure in northern Yucat'an, M'exico, Curie depths were obtained from statistical-spectral analysis of a grid of aeromagnetic data (256 km wide and 600 km long). These depths were corrected for flight height and depth to the sea floor to determine the geothermal gradient, assuming a temperature of 580 °C for the Curie temperature. Heat flow was then calculated from the geothermal gradients using a value of 2.67 W/m-for the mean crustal thermal conductivity. The results show a conspicuous heat flow high above on the impact basin. In this location, the heat flow is 80 mW/m2 approximately. Available offshore estimates of the depth to the crustal magnetic source bases, on the northern Yucat'an platform, and onshore heat flow determination on 8 shallow bore holes, and in a 1511 m deep one, support the existence of this major high heat flow anomaly associated with the impact crater. This high heat flow might be related to the impact through: (1) an uplift of the crystalline basement rocks in the center of the crater; and (2) impact induced radioactive element concentration into the crust below the impact structure. Higher thermal conductivities at the lower crust might also play a key role. Available seismological and thermal property data are compatible with these mechanisms. © 2016 Elsevier B.V.
cited By 4

Gyrosigma peisonis var. major var. nov., a new variety of Gyrosigma peisonis (Bacillariophyta) from Lake Qinghai, China - Peng, Yumei; Rioual, Patrick; Jin, Zhangdong; Sterrenburg, Frithjof A. S. (Phytotaxa, 2016)
The morphology and ultrastructure of Gyrosigma peisonis var. major var. nov., a new variety of Gyrosigma peisonis found in Lake Qinghai (China), are described here on the basis of light and scanning electron microscopy. Most of the morphological features of this new variety are identical to those of the nominal variety Gyrosigma peisonis var. peisonis, but the variety major differs in its distinctly larger cell size and its higher value for the longitudinal/transverse stria density ratio, however. The seasonal variation of this taxon, which was investigated by a sediment-trap study is also discussed. © 2016 Magnolia Press.

Laboratory observations of time-dependent frictional strengthening and stress relaxation in natural and synthetic fault gouges - Carpenter, B.M.; Ikari, M.J.; Marone, C. (Journal of Geophysical Research: Solid Earth, 2016)
Interseismic recovery of fault strength (healing) following earthquake failure is a fundamental requirement of the seismic cycle and likely plays a key role in determining the stability and slip behavior of tectonic faults. We report on laboratory measurements of time- and slip-dependent frictional strengthening for natural and synthetic gouges to evaluate the role of mineralogy in frictional strengthening. We performed slide-hold-slide (SHS) shearing experiments on nine natural fault gouges and eight synthetic gouges at conditions of 20 MPa normal stress, 100% relative humidity (RH), large shear strain ( 15), and room temperature. Phyllosilicate-rich rocks show the lowest rates of frictional strengthening. Samples rich in quartz and feldspar exhibit intermediate rates of frictional strengthening, and calcite-rich gouges show the largest values. Our results show that (1) the rates of frictional strengthening and creep relaxation scale with frictional strength, (2) phyllosilicate-rich fault gouges have low strength and healing characteristics that promote stable, aseismic creep, (3) most natural fault gouges exhibit intermediate rates of frictional strengthening, consistent with a broad range of fault slip behaviors, and (4) calcite-rich fault rocks show the highest rates of frictional strengthening, low values of dilation upon reshear, and high frictional strengths, all of which would promote seismogenic behavior. ©2016. American Geophysical Union. All Rights Reserved.
cited By 67
Keywords: earthquake event; fault; fault gouge; friction; mineralogy; observational method; relative humidity; slip; stress

Glacial legacies on interglacial vegetation at the Pliocene-Pleistocene transition in NE Asia - Herzschuh, U.; Birks, H.J.B.; Laepple, T.; Andreev, A.; Melles, M.; Brigham-Grette, J. (Nature Communications, 2016)
Broad-scale climate control of vegetation is widely assumed. Vegetation-climate lags are generally thought to have lasted no more than a few centuries. Here our palaeoecological study challenges this concept over glacial-interglacial timescales. Through multivariate analyses of pollen assemblages from Lake El'gygytgyn, Russian Far East and other data we show that interglacial vegetation during the Plio-Pleistocene transition mainly reflects conditions of the preceding glacial instead of contemporary interglacial climate. Vegetation-climate disequilibrium may persist for several millennia, related to the combined effects of permafrost persistence, distant glacial refugia and fire. In contrast, no effects from the preceding interglacial on glacial vegetation are detected. We propose that disequilibrium was stronger during the Plio-Pleistocene transition than during the Mid-Pliocene Warm Period when, in addition to climate, herbivory was important. By analogy to the past, we suggest today's widespread larch ecosystem on permafrost is not in climate equilibrium. Vegetation-based reconstructions of interglacial climates used to assess atmospheric CO 2-Temperature relationships may thus yield misleading simulations of past global climate sensitivity.
cited By 53
Keywords: atmospheric gas; climate change; detection method; disequilibrium; glacier dynamics; historical record; interglacial; paleoclimate; paleoecology; paleoenvironment; permafrost; Pliocene; Pliocene-Pleistocene boundary; reconstruction; vegetation dynamics; ecosystem; Far East; global climate; herbivory; interglacial; Larix; multivariate analysis; permafrost; Pleistocene; Pliocene; refugium; vegetation; Chukchi; Elgygytgyn Lake; Far East; Russian Far East; Russian Federation; Larix

Environmental control on the occurrence of high-coercivity magnetic minerals and formation of iron sulfides in a 640ka sediment sequence from Lake Ohrid (Balkans) - Just, J.; Nowaczyk, N.R.; Sagnotti, L.; Francke, A.; Vogel, H.; Lacey, J.H.; Wagner, B. (Biogeosciences, 2016)
The bulk magnetic mineral record from Lake Ohrid, spanning the past 637 kyr, reflects large-scale shifts in hydrological conditions, and, superimposed, a strong signal of environmental conditions on glacial-interglacial and millennial timescales. A shift in the formation of early di-agenetic ferrimagnetic iron sulfides to siderites is observed around 320 ka. This change is probably associated with variable availability of sulfide in the pore water. We propose that sulfate concentrations were significantly higher before ∼ 320 ka, due to either a higher sulfate flux or lower dilution of lake sulfate due to a smaller water volume. Diagenetic iron minerals appear more abundant during glacials, which are generally characterized by higher Fe/Ca ratios in the sediments. While in the lower part of the core the ferrimagnetic sulfide signal overprints the primary detrital magnetic signal, the upper part of the core is dominated by variable proportions of high- to low-coercivity iron oxides. Glacial sediments are characterized by high concentration of high-coercivity magnetic minerals (hematite, goethite), which relate to enhanced erosion of soils that had formed during preceding interglacials. Superimposed on the glacial-interglacial behavior are millennial-scale oscillations in the magnetic mineral composition that parallel variations in summer insolation. Like the processes on glacial-interglacial timescales, low summer insolation and a retreat in vegetation resulted in enhanced erosion of soil material. Our study highlights that rock-magnetic studies, in concert with geochemical and sedimentological investigations, provide a multi-level contribution to environmental reconstructions, since the magnetic properties can mirror both environmental conditions on land and intra-lake processes. © Author(s) 2016.
cited By 18
Keywords: concentration (composition); dilution; environmental conditions; glacial deposit; iron oxide; iron sulfide; magnetic mineral; sediment chemistry; siderite; sulfate; timescale; Balkans; Lake Ohrid

Geomicrobiological features of ferruginous sediments from lake Towuti, Indonesia - Vuillemin, Aurèle; Friese, Andr'e; Alawi, Mashal; Henny, Cynthia; Nomosatryo, Sulung; Wagner, Dirk; Crowe, Sean A.; Kallmeyer, Jens (Frontiers in Microbiology, 2016)
Lake Towuti is a tectonic basin, surrounded by ultramafic rocks. Lateritic soils form through weathering and deliver abundant iron (oxy)hydroxides but very little sulfate to the lake and its sediment. To characterize the sediment biogeochemistry, we collected cores at three sites with increasing water depth and decreasing bottom water oxygen concentrations. Microbial cell densities were highest at the shallow site-a feature we attribute to the availability of labile organic matter (OM) and the higher abundance of electron acceptors due to oxic bottom water conditions. At the two other sites, OM degradation and reduction processes below the oxycline led to partial electron acceptor depletion. Genetic information preserved in the sediment as extracellular DNA (eDNA) provided information on aerobic and anaerobic heterotrophs related to Nitrospirae, Chloroflexi, and Thermoplasmatales. These taxa apparently played a significant role in the degradation of sinking OM. However, eDNA concentrations rapidly decreased with core depth. Despite very low sulfate concentrations, sulfate-reducing bacteria were present and viable in sediments at all three sites, as confirmed by measurement of potential sulfate reduction rates. Microbial community fingerprinting supported the presence of taxa related to Deltaproteobacteria and Firmicutes with demonstrated capacity for iron and sulfate reduction. Concomitantly, sequences of Ruminococcaceae, Clostridiales, and Methanomicrobiales indicated potential for fermentative hydrogen and methane production. Such first insights into ferruginous sediments showed that microbial populations perform successive metabolisms related to sulfur, iron, and methane. In theory, iron reduction could reoxidize reduced sulfur compounds and desorb OM from iron minerals to allow remineralization to methane. Overall, we found that biogeochemical processes in the sediments can be linked to redox differences in the bottom waters of the three sites, like oxidant concentrations and the supply of labile OM. At the scale of the lacustrine record, our geomicrobiological study should provide a means to link the extant subsurface biosphere to past environments. © 2016 Vuillemin, Friese, Alawi, Henny, Nomosatryo, Wagner, Crowe and Kallmeyer.
Keywords: organic matter; organic nitrogen; oxidizing agent; anoxia; Article; atomic absorption spectrometry; biogeochemistry; biosphere; Chloroflexi; Clostridiales; controlled study; Deltaproteobacteria; denaturing gradient gel electrophoresis; Firmicutes; fluorescent lighting; gene sequence; ion chromatography; lake sediment; Methanomicrobiales; microbial community; Nitrospirae; nonhuman; nucleic acid analysis; oxidation reduction reaction; oxygen concentration; phylogeny; polymerase chain reaction; Ruminococcaceae; sulfate reducing bacterium; Thermoplasmatales; total organic carbon

Ecology of cladocera species from central America based on subfossil assemblages - Wojew'odka, Marta; Zawisza, Edyta; Cohuo, Sergio; Macario-Gonz'alez, Laura; Schwalb, Antje; Zawiska, Izabela; P'erez, Liseth (Advances in Oceanography and Limnology, 2016)
Cladocera species composition was analyzed in surface sediments of 29 lakes in Central America (Guatemala, El Salvador and Honduras). The material studied was collected with an Ekman grab in autumn 2013 from lakes located in lowland, highland and mountain regions. The study revealed high variability in qualitative and quantitative composition of subfossil Cladocera. A total of 31 Cladocera species (5 planktonic and 26 littoral) were identified, as well as 4 morphotypes that could not be identified (NRR 1-4). Planktonic Bosminidae and Daphniidae were the most abundant families. Daphniidae were restricted to water bodies in mountain regions, whereas Bosminidae were widely distributed in lakes with different abiotic conditions. Moreover, Bosminidae species also occurred in highly mineralized waters (> 900 μS cm –1). The great majority of the identified Cladocera species belonged to the littoral family Chydoridae. Chydorus cf. sphaericus was the most common species (found in 20 lakes), which probably reflects its tolerance to a wide spectrum of habitat conditions. Cluster analysis discriminated 6 groups of Cladocera species with a high correlation level within groups (≥0.8), which showed different types of correlation with lake characteristics and environmental variables. Canonical correspondence analysis (CCA) showed that altitude and secondly water electrical conductivity were the most important drivers of Cladocera species composition in the region studied. Furthermore, CCA analysis indicated lowland lakes with low water transparency were also characterized by peculiar species assemblages. © 2016, Page Press Publications. All rights reserved.
Keywords: El Salvador [Central America]; Guatemala [Central America]; Honduras; Bosminidae; Chydoridae; Chydorus sphaericus; Cladocera; Daphniidae; cluster analysis; crustacean; fossil assemblage; lacustrine deposit; morphotype; paleoecology; paleontology; plankton

Electrolyte effects on surface chemistry of basaltic glass in the initial stages of dissolution - Dultz, S.; Behrens, H.; Helsch, G.; Deubener, J. (Chemical Geology, 2016)
For an understanding of the effect of solution composition on the dissolution rate of basaltic glass detailed knowledge of surface chemistry is important. Here the zeta potential (ζ) as a characteristic parameter of the magnitude of surface charge at the solid-liquid interface was used to determine ionic effects on surface chemistry in initial stages of basaltic glass dissolution. In a systematic approach powdered synthetic basaltic glass was dispersed in solutions of different cations (NO3- salts of Na+, K+, Mg2+, Ca2+, Ba2+, Zn2+, and Al3+) and anions (Na+ salts of F-, Cl-, I-, NO3-, SO42-, C2O42-, HPO42-), each in concentrations of 0.1, 0.5, 1.0, 2.5, and 5.0 mmol/L. ζ was traced in time sequences up to 12,000 h at ideally circumneutral pH. Ion affinities to glass surfaces were characterized by sorption isotherms. A change of glass chemical composition by the formation of altered layers was determined by depth profiling using secondary neutral mass spectrometry (SNMS). The dissolution of the glass was quantified by the amount of Si released after 4000 h.A marked decrease of ζ in deionized water within the first 3 h reaction time is assigned to the desorption of alkali and alkaline earth metal cations from the glass surface and formation of negatively charged SiO- sites. The addition of anions resulted in stronger negative initial ζ values in comparison with the experiment in deionized H2O indicating marked anion adsorption on surface sites, most obvious for F-, C2O42- and HPO42-. The initial ζ was increased upon the addition of divalent cations indicating neutralization of negatively charged surface sites. Over time a striking shift from negative to positive ζ was obtained, most markedly for Ca2+ and Zn2+. The addition of trivalent Al3+ resulted directly in positive ζ indicating a strong adsorption on glass surfaces. With the progress of the experiment the sign of ζ reversed to negative values again. The reason for charge reversal is not fully understood and might be related with cation adsorption exceeding the negative surface charge and a concentration of Fe oxides at the glass surface. After an 2000 h reaction time ζ adjusted for most electrolyte additions to slightly negative ζ until the end of the experiment, indicating that a final state in the composition of surface sites was reached. The presence of monovalent Na+ and K+ in solution suppressed Si release from the glass, whereas it is accelerated by bivalent cations. It appears that the neutralization of deprotonated ≡Si-O- sites by monovalent cations - their preferential binding is also indicated by chemical analysis - favors polymerization resulting in slower Si release. Upon the addition of Al3+ it is likely that ≡Si-O-Al-O-Si≡ bonds are formed, which can suppress Si release. The presence of F-, C2O42-, and HPO42- clearly enhances glass dissolution, most probably by increasing the coordination of network forming cations, hereby weakening bonds. The observed generation of positive ζ on basaltic glass surfaces is remarkable, and can improve in natural systems the adsorption capability of the basaltic glass surface for negatively charged compounds from pore solution, anions, dissolved organic matter and also bacterial cell walls. © 2016 Elsevier B.V.
cited By 9
Keywords: Adsorption; Alkalinity; Aluminum; Basalt; Binding sites; Biological materials; Calcium; Cell membranes; Chemical analysis; Deionized water; Depth profiling; Dissolution; Electrolytes; Geochemistry; Ions; Mass spectrometry; Negative ions; Phase interfaces; Positive ions; Salts; Silicon; Surface chemistry; Zeta potential; Zinc; Alkaline Earth metal cations; Basaltic glass; Charge reversal; Dissolved organic matters; Electrolyte effect; Negative surface charges; Negatively charged surfaces; Secondary neutral mass spectrometry; Glass; concentration (composition); dissolution; electrolyte; experimental study; igneous geochemistry; silicon; Bacteria (microorganisms)

Elemental changes and alteration recorded by basaltic drill core samples recovered from in situ temperatures up to 345°C in the active, seawater-recharged Reykjanes geothermal system, Iceland - Fowler, A.P.G.; Zierenberg, R.A. (Geochemistry, Geophysics, Geosystems, 2016)
Hydrothermal activity results in element exchanges between seawater and oceanic crust that contribute to many aspects of ocean chemistry; therefore, improving knowledge of the associated chemical processes is of global significance. Hydrothermally altered basaltic drill core samples from the seawater-recharged Reykjanes geothermal system in Iceland record elemental gains and losses similar to those observed in samples of hydrothermally altered oceanic crust. At Reykjanes, rocks originally emplaced on the seafloor were buried by continued volcanism and subsided to the current depths (>2250 m below surface). These rocks integrate temperature-dependent elemental gains and losses from multiple stages of hydrothermal alteration that correspond to chemical exchanges observed in rocks from different crustal levels of submarine hydrothermal systems. Specifically, these lithologies have gained U, Mg, Zn, and Pb and have lost K, Rb, Ba, Cu, and light rare earth elements (La through Eu). Alteration and elemental gains and losses in lithologies emplaced on the seafloor can only be explained by a complex multistage hydrothermal alteration history. Reykjanes dolerite intrusions record alteration similar to that reported for the sheeted dike section of several examples of oceanic crust. Specifically, Reykjanes dolerites have lost K, Rb, Ba, and Pb, and gained Cu. The Reykjanes drill core samples provide a unique analog for seawater-oceanic crust reactions actively occurring at high temperatures (275 –345°C) beneath a seafloor hydrothermal system. © 2016. American Geophysical Union. All Rights Reserved.
cited By 9
Keywords: Clay alteration; Core drilling; Core samples; Drills; Europium compounds; Geothermal fields; Hydraulic structures; Hydrochemistry; Lithology; Magnesium; Rubidium; Seawater; Uranium; Drill core; Hydrothermal alterations; ICDP; Oceanic crust; Reykjanes; Europium; emplacement; geothermal system; hydrothermal alteration; hydrothermal system; lithology; oceanic crust; recharge; seawater; temperature effect; volcanism; Iceland

Elevated time-dependent strengthening rates observed in San Andreas Fault drilling samples - Ikari, M.J.; Carpenter, B.M.; Kopf, A.J. (Earth and Planetary Science Letters, 2016)
The central San Andreas Fault in California is known as a creeping fault, however recent studies have shown that it may be accumulating a slip deficit and thus its seismogenic potential should be seriously considered. We conducted laboratory friction experiments measuring time-dependent frictional strengthening (healing) on fault zone and wall rock samples recovered during drilling at the San Andreas Fault Observatory at Depth (SAFOD), located near the southern edge of the creeping section and in the direct vicinity of three repeating microearthquake clusters. We find that for hold times of up to 3000 s, frictional healing follows a log-linear dependence on hold time and that the healing rate is very low for a sample of the actively shearing fault core, consistent with previous results. However, considering longer hold times up to ∼350,000 s, the healing rate accelerates such that the data for all samples are better described by a power law relation. In general, samples having a higher content of phyllosilicate minerals exhibit low log-linear healing rates, and the notably clay-rich fault zone sample also exhibits strong power-law healing when longer hold times are included. Our data suggest that weak faults, such as the creeping section of the San Andreas Fault, can accumulate interseismic shear stress more rapidly than expected from previous friction data. Using the power-law dependence of frictional healing on hold time, calculations of recurrence interval and stress drop based on our data accurately match observations of discrete creep events and repeating Mw=2 earthquakes on the San Andreas Fault. © 2016 Elsevier B.V.
cited By 15
Keywords: Clay minerals; Earthquakes; Friction; Rock drilling; Shear stress; Strike-slip faults; Tribology; Creeping faults; Friction experiments; Linear dependence; Power law relation; Power-law dependences; Recurrence intervals; SAFOD; San Andreas fault; Structural geology; drilling; earthquake recurrence; fault zone; friction; microearthquake; recurrence interval; San Andreas Fault; California; United States

Ecosystem regimes and responses in a coupled ancient lake system from MIS 5b to present: The diatom record of lakes Ohrid and Prespa - Cvetkoska, A.; Jovanovska, E.; Francke, A.; Tofilovska, S.; Vogel, H.; Levkov, Z.; Donders, T.H.; Wagner, B.; Wagner-Cremer, F. (Biogeosciences, 2016)
We reconstruct the aquatic ecosystem interactions since the last interglacial period in the oldest, most diverse, hydrologically connected European lake system, by using palaeolimnological diatom and selected geochemistry data from Lake Ohrid DEEP site core and equivalent data from Lake Prespa core, Co1215. Driven by climate forcing, the lakes experienced two adaptive cycles during the last 92 ka: interglacial and interstadial and glacial cycle. The shortterm ecosystems reorganizations, e.g. regime shifts within these cycles substantially differ between the lakes, as evident from the inferred amplitudes of variation. The deeper Lake Ohrid shifted between ultra oligo- and oligotrophic regimes in contrast to the much shallower Lake Prespa, which shifted from a deeper, (oligo-) mesotrophic to a shallower, eutrophic lake and vice versa. Due to the high level of ecosystem stability (e.g. trophic state, lake level), Lake Ohrid appears relatively resistant to external forcing, such as climate and environmental change. Recovering in a relatively short time from major climate change, Lake Prespa is a resilient ecosystem. At the DEEP site, the decoupling between the lakes' response to climate change is marked in the prolonged and gradual changes during the MIS 5/4 and 2/1 transitions. These response differences and the lakes' different physical and chemical properties may limit the influence of Lake Prespa on Lake Ohrid. Regime shifts of Lake Ohrid due to potential hydrological change in Lake Prespa are not evident in the data presented here. Moreover, a complete collapse of the ecosystems functionality and loss of their diatom communities did not happen in either lake for the period presented in the study. © 2016 Author(s).
cited By 21
Keywords: aquatic ecosystem; climate change; climate forcing; diatom; ecosystem resilience; fossil record; hydrological change; lacustrine environment; Last Interglacial; microbial community; micropaleontology; paleoclimate; paleoecology; paleolimnology; physicochemical property; reconstruction; Lake Mikri Prespa; Lake Ohrid; Bacillariophyta

Experimental constraints on the relationship between clay abundance, clay fabric, and frictional behavior for the Central Deforming Zone of the San Andreas Fault - Wojatschke, J.; Scuderi, M.M.; Warr, L.N.; Carpenter, B.M.; Saffer, D.; Marone, C. (Geochemistry, Geophysics, Geosystems, 2016)
The presence of smectite (saponite) in fault gouge from the Central Deforming Zone of the San Andreas Fault at Parkfield, CA has been linked to low mechanical strength and aseismic slip. However, the precise relationship between clay mineral structure, fabric development, fault strength, and the stability of frictional sliding is not well understood. We address these questions through the integration of laboratory friction tests and FIB-SEM analysis of fault rock recovered from the San Andreas Fault Observatory at Depth (SAFOD) borehole. Intact fault rock was compared with experimentally sheared fault gouge and different proportions of either quartz clasts or SAFOD clasts extracted from the sample. Nano-textural measurements show the development of localized clay particle alignment along shear folia developed within synthetic gouges; such slip planes have multiples of random distribution (MRD) values of 3.0 –4.9. The MRD values measured are higher than previous estimates (MRD 1.5) that show lower degrees of shear localization and clay alignment averaged over larger volumes. The intact fault rock exhibits less well-developed nano-clay fabrics than the experimentally sheared materials, and MRD values decrease with smectite content. We show that the abundance, strength, and shape of clasts all influence fabric evolution via strain localization: quartz clasts yield more strongly developed clay fabrics than serpentine-dominated SAFOD clasts. Our results suggest that (1) both clay abundance and the development of nano-scale fabrics play a role in fault zone weakening and (2) aseismic creep is promoted by slip along clay shears with >20 wt % smectite content and MRD values ≥2.7. © 2016. American Geophysical Union. All Rights Reserved.
cited By 11
Keywords: Clay minerals; Deformation; Friction; Nanotechnology; Quartz; Serpentine; Silicate minerals; Strike-slip faults; Structural geology; Tectonics; Different proportions; Fabric development; Fault zone; Frictional behavior; Frictional sliding; Random distribution; Shear localizations; Strain localizations; Fault slips; clay mineral; deformation; experimental study; fault gouge; fault zone; friction; petrofabric; San Andreas Fault; slip; California; Parkfield; United States

Fe-Ti-V-(P) resources in the upper zone of the Bushveld complex, South Africa - Fischer, LA; Yuan, Q (Papers and Proceedings of the Royal Society of Tasmania, 2016)

First tephrostratigraphic results of the DEEP site record from Lake Ohrid (Macedonia and Albania) - Leicher, N.; Zanchetta, G.; Sulpizio, R.; Giaccio, B.; Wagner, B.; Nomade, S.; Francke, A.; Del Carlo, P. (Biogeosciences, 2016)
A tephrostratigraphic record covering the Marine Isotope Stages (MIS) 1-15 was established for the DEEP site record of Lake Ohrid (Macedonia and Albania). Major element analyses (energy dispersive spectroscopy (EDS) and wavelength-dispersive spectroscopy (WDS)) were carried out on juvenile fragments extracted from 12 tephra layers (OH-DP-0115 to OH-DP-2060). The geochemical analyses of the glass shards of all of these layers suggest an origin in the Italian volcanic provinces. They include the Y-3 (OH-DP-0115, 26.68-29.42 ka cal BP), the Campanian Ignimbrite-Y-5 (OH-DP-0169, 39.6±0.1 ka), and the X- 6 (OH-DP-0404, 109±2 ka) from the Campanian volcanoes, the P-11 of Pantelleria (OH-DP-0499, 133.5±2 ka), the Vico B (OH-DP-0617, 162±6 ka) from the Vico volcano, the Pozzolane Rosse (OH-DP-1817, 457±2 ka) and the Tufo di Bagni Albule (OH-DP-2060, 527±2 ka) from the Colli Albani volcanic district, and the Fall A (OH-DP- 2010, 496±3 ka) from the Sabatini volcanic field. Furthermore, a comparison of the Ohrid record with tephrostratigraphic records of mid-distal archives related to the Mediterranean area allowed the recognition of the equivalents of other less known tephra layers, such as the TM24a-POP2 (OH-DP-0404, 102±2 ka) recognized in the Lago Grande di Monticchio and the Sulmona Basin, the CF-V5-PRAD3225 (OH-DP-0624, ca. 163±22 ka) identified in the Campo Felice Basin and the Adriatic Sea, the SC5 (OH-DP-1955, 493.1±10.9 ka) recognized in the Mercure Basin, and the A11/12 (OH-DP-2017, 511±6 ka) sampled at the Acerno Basin, whose specific volcanic sources are still poorly constrained. Additionally, one cryptotephra (OH-DP-0027) was identified by correlation of the potassium X-ray flourescence (XRF) intensities from the DEEP site with those from a short core of a previous study from Lake Ohrid. In these cores, a maximum in potassium is caused by glass shards, which were correlated with the Mercato tephra (8.43-8.63 ka cal BP) from Somma-Vesuvius. The tephrostratigraphic work presented here allows, for the first time, the extension of a consistent part of the Middle Pleistocene tephrostratigraphy of Italian volcanoes as far as the Balkans. The establishment of the tephrostratigraphic framework for the Lake Ohrid record provides important, independent tie points for the age-depth model of the DEEP site sequence, which is a prerequisite for palaeoclimatic and palaeoenvironmental reconstructions. Furthermore, this age-depth model will help to improve and re-evaluate the chronology of other, both undated and dated tephra layers from other records. Thus, the Lake Ohrid record may potentially become the template for the central Mediterranean tephrostratigraphy, especially for the hitherto poorly known and explored lower Middle Pleistocene period. © 2016 Author(s).
cited By 61
Keywords: biostratigraphy; Campanian; geochemical method; marine environment; paleoclimate; paleoenvironment; Pleistocene; tephra; tephrochronology; volcanic soil; Abruzzi; Adriatic Sea; Alban Hills; Albania; Apennines; Balkans; Basilicata; Campania [Italy]; Italy; L' Aquila; Lago Grande di Monticchio; Lake Ohrid; Lazio; Macedonia [Southern Europe]; Mediterranean Sea; Mount Somma; Napoli [Campania]; Potenza; Sulmona Basin; Vesuvius; Vico

Flowing fluid electrical conductivity logging of a deep borehole during and following drilling: estimation of transmissivity, water salinity and hydraulic head of conductive zones - Doughty, Christine; Tsang, Chin-Fu; Rosberg, Jan-Erik; Juhlin, Christopher; Dobson, Patrick F.; Birkholzer, Jens T. (Hydrogeology Journal, 2016)
Flowing fluid electrical conductivity (FFEC) logging is a hydrogeologic testing method that is usually conducted in an existing borehole. However, for the 2,500-m deep COSC-1 borehole, drilled at Åre, central Sweden, it was done within the drilling period during a scheduled 1-day break, thus having a negligible impact on the drilling schedule, yet providing important information on depths of hydraulically conductive zones and their transmissivities and salinities. This paper presents a reanalysis of this set of data together with a new FFEC logging data set obtained soon after drilling was completed, also over a period of 1 day, but with a different pumping rate and water-level drawdown. Their joint analysis not only results in better estimates of transmissivity and salinity in the conducting fractures intercepted by the borehole, but also yields the hydraulic head values of these fractures, an important piece of information for the understanding of hydraulic structure of the subsurface. Two additional FFEC logging tests were done about 1 year later, and are used to confirm and refine this analysis. Results show that from 250 to 2,000 m depths, there are seven distinct hydraulically conductive zones with different hydraulic heads and low transmissivity values. For the final test, conducted with a much smaller water-level drawdown, inflow ceased from some of the conductive zones, confirming that their hydraulic heads are below the hydraulic head measured in the wellbore under non-pumped conditions. The challenges accompanying 1-day FFEC logging are summarized, along with lessons learned in addressing them.

Gas Production from Methane Hydrate: A Laboratory Simulation of the Multistage Depressurization Test in Mallik, Northwest Territories, Canada - Heeschen, K.U.; Abendroth, S.; Priegnitz, M.; Spangenberg, E.; Thaler, J.; Schicks, J.M. (Energy and Fuels, 2016)
Gas hydrate production is still in the test phase. It is only now that numerical models are being developed to describe data and production scenarios. Laboratory experiments are carried out to test the rationale of the conceptual models and deliver input data. Major experimental challenges include (I) the simulation of a natural three-phase system of sand-hydrate-liquid with known and high hydrate saturations and (II) the simulation of transport behavior as deduced from field data. The large-scale reservoir simulator (LARS; 210 L sample) at the GFZ has met these challenges and allowed for the first simulation of the gas production test from permafrost hydrates at the Mallik drill site (Canada) via multistage depressurization. At the starting position, hydrate saturation was as high as 90%, formed from dissolved methane only. Whereas gas hydrate dissociation determined the flow patterns in the early pressure stages, the importance of different transport behaviors increased at lower pressure stages and increasing water content. Gas flow patterns as observed in Mallik were recorded. While the conceptual model for the experimental data does agree with the model proposed for Mallik at moderate and low gas production, it is different at high gas production rates. © 2016 American Chemical Society.
cited By 73
Keywords: Flow of gases; Flow patterns; Gases; Hydration; Methane; Gas production test; Gas-hydrate production; Hydrate dissociation; Laboratory experiments; Laboratory simulation; Reservoir simulator; Three phase system; Transport behavior; Gas hydrates

Geological record of meltwater events at Qinghai Lake, China from the past 40 ka - Zhou, Weijian; Liu, Taibei; Wang, Hao; An, ZhiSheng; Cheng, Peng; Zhu, Yizhi; Burr, G.S. (Quaternary Science Reviews, 2016)
We report here on a previously unpublished sediment core from Qinghai Lake, China, that preserves a continuous record of sedimentation for the past 40 ka. A striking feature of the record is a set of distinct meltwater events recorded at 35, 19 and 14 ka respectively. These events are manifest as distinct pulses of relatively old organic radiocarbon in the sediments. We interpret these as a signal of glacial melting in the Qinghai Lake watershed. The meltwater signals are closely correlated to temperature and precipitation records associated with deglaciation. The events at 19 ka and 14 ka correspond to well-established high latitude Melt Water Pulse (MWP) events during Marine Isotope Stage (MIS) 2, and the 35 ka event corresponds to a period of pervasive high lake levels in western China during late MIS 3. We interpret these anomalous dates as the result of relatively old carbon that was destabilized by the glaciers, and released into the lake as the glaciers melted. The data indicate that this process takes thousands of years. We expect that the approach employed here to identify these events is generally applicable to any lake system with a significant glacial meltwater component. © 2016 Elsevier Ltd
Keywords: China; Qinghai; Qinghai Lake; Carbon; Glacial geology; Organic carbon; Carbon effects; Lacustrine record; Meltwater event; Radiocarbon dating; Total Organic Carbon; core analysis; deglaciation; lacustrine environment; marine isotope stage; meltwater; precipitation assessment; radiocarbon dating; sedimentation; total organic carbon; watershed; Lakes

General design of geophysical logging of the CCSD-SK-2 East Borehole in the Songliao Basin of Northeast China - Zou, Changchun; Xiao, Liang; Niu, Yixiong; Hou, Jie; Peng, Cheng (Earth Science Frontiers, 2016)
CCSD-SK-2 East Borehole is the main borehole of China Continental Scientific Drilling Project in Songliao Basin, which is designed to reach a depth of 6400 m to penetrate Cretaceous strata. Its implementation is important for the research of the Cretaceous sedimentary environment and climate, for the achievement of new breakthroughs in oil and gas exploration, for the enhancement of the deep-drilling level and geophysical logging techniques, etc. Based on the scientific objectives and tasks of this project, combined with the design of drilling engineering and the characteristics of well conditions, the authors carried out the logging design of CCSD-SK-2 East-Borehole,intending to adopt the most advanced equipment to acquire log data. The adopted logging suits include comprehensive logging in openhole and cement-evaluation logging in cased hole. Based on the situation of drilling times and programs, eight times of comprehensive logging and five times of cement-evaluation logging are designed respectively, and comprehensive logging suits in different drilling times are different; taking into account the challenge of high temperature under the depth of 4500 m, logging items are designed including both required and selected ones. This logging design not only seeks to completely acquire all kinds of log data, but also conduces to flexibly deal with complex conditions of the borehole, which would be beneficial to the achievement of scientific goals. © 2016, Editorial Office of Earth Science Frontiers. All right reserved.
Keywords: Cements; Deep oil well drilling; Density measurement (specific gravity); Geophysics; Oil well drilling; Oil well drilling equipment; Petroleum prospecting; Well logging; Continental scientific drillings; Cretaceous; Drilling engineering; Geophysical logging; Oil and gas exploration; Scientific objectives; Sedimentary environment; Songliao basin; Boring

Experimental investigation of the effect of Ca, Fe and Ti on cotectic compositions of the rhyolitic system - Wilke, S{oren; Klahn, Carolin; Bolte, Torsten; Almeev, Renat; Holtz, François (European Journal of Mineralogy, 2015)
The effect of the normative anorthite content on the position of cotectic curves in the Qz –Ab –Or –An system has been investigated at 200 MPa and a water activity of 0.5. To simulate compositions as close as possible to those of natural high-silica rhyolites, all investigated compositions also contained 1 wt% FeO and 0.2 wt% TiO2. The position of the cotectic curves was deduced from crystallization experiments carried out between 790 and 850°C and using fourteen starting glass compositions containing 3 wt% H2O. The liquidus phase of the different starting materials was used to constrain the primary fields of quartz, plagioclase and sanidine. The compositions of residual melts coexisting with solid phases were used to define the position of cotectic curves. Compared to the haplogranite system, the eutectic point is shifted away from the Ab apex, and its composition is estimated to be Qz42Ab21Or37 when projected onto the haplogranite system. The implications for the estimation of the depth of magma storage conditions are discussed on the basis of an example from the Snake River Plain high-silica rhyolites.

Rock-magnetic proxies of wind intensity and dust since 51,200 cal BP from lacustrine sediments of Laguna Potrok Aike, southeastern Patagonia - Lis'e-Pronovost, Agathe; St-Onge, Guillaume; Gogorza, Claudia; Haberzettl, Torsten; Jouve, Guillaume; Ohlendorf, Christian; Gebhardt, Catalina; Zolitschka, Bernd (Earth and Planetary Science Letters, 2015)
The sedimentary archive from Laguna Potrok Aike is the only continuous record reaching back to the last Glacial period in continental southeastern Patagonia. Located in the path of the Southern Hemisphere westerly winds and in the source region of dust deposited in Antarctica during Glacial periods, southern Patagonia is a vantage point to reconstruct past changes in aeolian activity. Here we use high-resolution rock-magnetic and physical grain size data from site 2 of the International Continental scientific Drilling Program (ICDP) Potrok Aike maar lake Sediment Archive Drilling prOject (PASADO) in order to develop magnetic proxies of dust and wind intensity at 52°S since 51,200 cal BP. Rock-magnetic analysis indicates the magnetic mineral assemblage is dominated by detrital magnetite. Based on the estimated flux of magnetite to the lake and comparison with distal dust records from the Southern Ocean and Antarctica, kLF is interpreted as a dust indicator in the dust source of southern Patagonia at the millennial time scale, when ferrimagnetic grain size and coercivity influence are minimal. Comparison to physical grain-size data indicates that the median destructive field of isothermal remanent magnetization (MDFIRM) mostly reflects medium to coarse magnetite bearing silts typically transported by winds for short-term suspension. Comparison with wind-intensity proxies from the Southern Hemisphere during the last Glacial period and with regional records from Patagonia since the last deglaciation including marine, lacustrine and peat bog sediments as well as speleothems reveals similar variability with MDFIRM up to the centennial time scale. MDFIRM is interpreted as a wind-intensity proxy independent of moisture changes for southeastern Patagonia, with stronger winds capable of transporting coarser magnetite bearing silts to the lake. © 2014 Elsevier B.V.
Keywords: Argentina; Laguna Potrok Aike; Santa Cruz [Argentina]; Dust; Glacial geology; Grain size and shape; Infill drilling; Lakes; Lithology; Magnetism; Magnetite; Minerals; Rocks; Salinity measurement; Silt; Wind; Lake sediments; PASADO; Rock magnetism; Westerly winds; Wind intensity; dust; grain size; lacustrine deposit; Last Glacial; magnetic property; magnetite; remanent magnetization; rock property; Southern Hemisphere; westerly; wind field; Sediments

Rock magnetic and AMS fabrics characterization of suevitic breccias from the Cretaceous-Paleogene Chicxulub impact crater - Delgadillo-Peralta, M.; Urrutia-Fucugauchi, J.; P'erez-Cruz, L.; Velasco-Villarreal, M. (Revista Mexicana de Ciencias Geologicas, 2015)
Results of a paleomagnetic and magnetic fabrics study of the basal suevitic breccias in the Chicxulub impact crater, Yucat'an platform, Gulf of Mexico are presented. The breccias were cored in the Yaxcopoil-1 borehole, which is located at about 62 km radial distance from the crater center. The impactite sequence in the Yaxcopoil-1 borehole is 100 m thick and formed by six subunits with distinct petrographic and geochemical characteristics. Here we investigate the basal subunit interpreted as: a ground surge in the transient cavity, a melt breccia with clastic material, or an excavation flow from the ejecta curtain interacting with the ejecta plume collapse. Characterization of the magnetic fabrics using rock magnetics and anisotropy of magnetic susceptibility (AMS) are used to investigate on the emplacement mechanism of the suevites. Magnetic hysteresis and k-T curves show that the magnetic mineralogy is dominated by low-Ti titanomagnetites and magnetite. The AMS fabrics record mixtures of oblate and prolate ellipsoids and principal susceptibility axial distributions with relatively high angular scatter, related to turbulent high temperature conditions during ejecta emplacement. Magnetic fabric parameters and principal susceptibility axial distributions correlate with modal composition, relative contents and orientation of melt particles. Results are interpreted in terms of an emplacement mode as an early excavation flow that incorporated ground surge components.
cited By 3

San Andreas fault zone velocity structure at SAFOD at core, log, and seismic scales - Jeppson, T.N.; Tobin, H.J. (Journal of Geophysical Research: Solid Earth, 2015)
The San Andreas Fault (SAF), like other mature brittle faults, exhibits a zone of low seismic velocity hypothesized to result from fluid pressure effects and/or development of a damage zone. To address the relative contributions of these mechanisms in developing low-velocity zones, we measured P and S wave velocities ultrasonically at elevated confining and pore pressures on core samples from the San Andreas Fault Observatory at Depth (SAFOD). We compared those data to wireline and seismic-scale velocities to examine the scale dependence of acoustic properties of the fault core and damage zone. Average laboratory P and S wave velocities of the fault gouge at estimated in situ conditions are 3.1 and 1.5 km/s, respectively, consistent with the sonic log from the same intervals. These data show that fault core has intrinsically low velocity, even if no anomalous pore pressure is assumed, due to alteration and mechanical damage. In contrast, laboratory average P and S wave velocities for the damage zone are 4.7 and 2.5 km/s, up to 41% greater than the sonic log in the damage zone. This scale dependence indicates that stress conditions or macroscale features dominate the damage zone's acoustic properties, although velocity dispersion could play a role. Because no pressure anomaly was detected while drilling the SAFOD borehole, we infer that damage at a scale larger than core samples controls the elastic properties of the broader damage zone. This result bolsters other independent lines of evidence that the SAF does not contain major pore fluid overpressure at SAFOD. ©2015. American Geophysical Union. All Rights Reserved.
cited By 19
Keywords: acoustic property; elastic modulus; fault zone; laboratory method; P-wave; S-wave; San Andreas Fault; seismic velocity; ultrasonics; velocity structure; wave velocity

Remnants of early Archean impact deposits on earth: Search for a meteoritic component in the BARB5 and CT3 drill cores (Barberton Greenstone Belt, South Africa) - Koeberl, Christian; Schulz, Toni; Reimold, W. Uwe (Procedia Engineering, 2015)
The first 2.5 billion years of the terrestrial impact history are not documented by any impact structures. Only a few spherule layers of impact origin are known, most of them of late Archean to early Proterozoic age. In the Barberton Greenstone Belt (South Africa), several spherule horizons (layers S1 to S4, possibly up to S8, with ages between ∼3.5 and ∼3.2 Ga) are amongst the oldest deposits from large bolide impacts onto Earth. Impact evidence is limited to (highly) elevated siderophile element contents and Cr isotopic compositions. Other isotope tools, such as the 187Re-188Os radionuclide system in combination with high-precision concentration data for siderophile elements, might be useful to confirm the propositions regarding the presence of meteoritic components made so far. Two recently recovered drill cores from the central and northern Barberton area (CT3 and BARB5) with as many as 18 spherule layer intersections of Paleoarchean age (some of which may be due to tectonic duplication, some might correlate with the S2 to S4 layers) provide an outstanding opportunity to gain new insight into the early impact bombardment of Earth. We present new mineralogical, chemical, and 187Re-188Os isotope data on CT3 and BARB5 drill core samples. Spherules in most layers exhibit undeformed shapes and include vesicles. Sulfides frequently are present in both matrix and spherules. Osmium data reveal a trend between the spherule-free horizons (intercalating the spherule layers) and spherule-matrix aggregates. Whereas the former typically exhibit elevated 187Os/188Os ratios of up to ∼1.2 and low Os and Ir concentrations below several hundred ppt, spherule-matrix aggregates tend to be less radiogenic (down to subchondritic present day 187Os/188Os ratios) with Os and Ir concentrations as high as in chondrites. Chromium-Ir correlations for CT3 and BARB5 samples mirror earlier results on S1 to S4 layers and can be interpreted in favor of an impact origin of the here investigated spherule horizons. © 2015 The Authors.
Keywords: Aggregates; Core drilling; Deposits; Drills; Iridium; Isotopes; Meteorites; Osmium; Archean; Greenstone belts; Highly siderophile elements; Osmium isotopes; spherules; Matrix algebra

Rapid reactivation of deep subsurface microbes in the presence of c-1 compounds - Rajala, Pauliina; Bomberg, Malin; Kiet{av{ainen, Riikka; Kukkonen, Ilmo; Ahonen, Lasse; Nyyss{onen, Mari; It{avaara, Merja (Microorganisms, 2015)
Microorganisms in the deep biosphere are believed to conduct little metabolic activity due to low nutrient availability in these environments. However, destructive penetration to long-isolated bedrock environments during construction of underground waste repositories can lead to increased nutrient availability and potentially affect the long-term stability of the repository systems, Here, we studied how microorganisms present in fracture fluid from a depth of 500 m in Outokumpu, Finland, respond to simple carbon compounds (C-1 compounds) in the presence or absence of sulphate as an electron acceptor. C-1 compounds such as methane and methanol are important intermediates in the deep subsurface carbon cycle, and electron acceptors such as sulphate are critical components of oxidation processes. Fracture fluid samples were incubated in vitro with either methane or methanol in the presence or absence of sulphate as an electron acceptor. Metabolic response was measured by staining the microbial cells with fluorescent dyes that indicate metabolic activity and transcriptional response with RT-qPCR. Our results show that deep subsurface microbes exist in dormant states but rapidly reactivate their transcription and respiration systems in the presence of C-1 substrates, particularly methane. Microbial activity was further enhanced by the addition of sulphate as an electron acceptor. Sulphate-and nitrate-reducing microbes were particularly responsive to the addition of C-1 compounds and sulphate. These taxa are common in deep biosphere environments and may be affected by conditions disturbed by bedrock intrusion, as from drilling and excavation for long-term storage of hazardous waste. © 2015 by the authors; licensee MDPI, Basel, Switzerland.

Quaternary climate change and Heinrich events in the southern Balkans: Lake Prespa diatom palaeolimnology from the last interglacial to present - Cvetkoska, A.; Levkov, Z.; Reed, J.M.; Wagner, B.; Panagiotopoulos, K.; Leng, M.J.; Lacey, J.H. (Journal of Paleolimnology, 2015)
Lake Prespa, in the Balkans, contains an important palaeo-archive in a key location for understanding Quaternary climate variability in the transition between Mediterranean and central European climate zones. Previous palaeoenvironmental research on sediment cores indicates that the lake is highly sensitive to climate change and that diatoms are likely to be strong palaeohydrological proxies. Here, we present new results from diatom analysis of a ca. 91 ka sequence, core Co1215, which spans the time from the end of the last interglacial to the present. Fluctuations in the diatom data were driven primarily by changes in lake level, as a function of shifts in moisture availability. Warmer interglacial (MIS 5, MIS 1) and interstadial (MIS 3) phases exhibit higher lake levels in spite of enhanced evaporative concentration, underlining the importance of changes in precipitation regimes over time. Low lake levels during glacial phases indicate extreme aridity, common to all Mediterranean lakes. Evidence for fluctuations in trophic status is linked, in part, to lake-level change, but also reflects nutrient enrichment from catchment processes. MIS 5a is characterized by the highest lake productivity in the sequence, but low lake levels, which are ascribed primarily to very low precipitation. On a suborbital timescale, the diatoms provide evidence for correlation to the millennial-scale variability recorded in the Greenland oxygen isotope records and clearly reflect the impact of the Heinrich H6, H5 and H3 –1 ice-rafting events, suggesting the dominant influence of North Atlantic forcing in this region. Although the highest-amplitude shift in the diatom assemblages occurs during the time of H4 (40 –38 ka), it may be superimposed upon the impact of the 39.28 cal ka BP Campanian Ignimbrite volcanic eruption. Diatoms from Lake Prespa core Co1215 display the first strong evidence for the impact of Italian volcanic activity on lacustrine biota in this region. Results emphasize the complexity of diatom response thresholds in different studies across the region. In the case of Lake Prespa, the results highlight the important role of precipitation for maintaining the hydrological balance of the lake, and indirectly, its biodiversity. © 2014, Springer Science+Business Media Dordrecht.
cited By 14

Seawater incursion events in a cretaceous paleo-lake revealed by specific marine biological markers - Hu, J.F.; Peng, P.A.; Liu, M.Y.; Xi, D.P.; Song, J.Z.; Wan, X.Q.; Wang, C.S. (Scientific Reports, 2015)
Many large paleo-lakes in North China were formed after the Triassic Era. Seawater incursion events (SWIEs) in these lakes have been extensively discussed in the literature, yet lack reliable methodology and solid evidence, which are essential for reconstructing and confirming SWIEs. The present study employs specific marine biological markers (24-n-propyl and 24-isopropyl cholestanes) to trace SWIEs in a dated core taken from the Songliao Basin (SLB). Two SWIEs were identified. The first SWIE from 91.37 to 89.00 Ma, was continuous and variable but not strong, while the second SWIE from 84.72 to 83.72 Ma was episodic and strong. SWIEs caused high total organic carbon (TOC) and negative δ13Corg values in the sediments, which were interpreted as an indication of high productivity in the lake, due to the enhancement of nutrient supplies as well as high levels of aqueous CO2, due to the mixing of alkaline seawater and acidic lake water. The SWIEs in SLB were controlled by regional tectonic activity and eustatic variation. Movement direction changes of the Izanagi/Kula Plate in 90 Ma and 84 Ma created faults and triggered SWIEs. A high sea level, from 90 to 84 Ma, also facilitated the occurrence of SWIEs in SLB.
cited By 51
Keywords: biological marker; carbon; sea water; China; lake; Biomarkers; Carbon; China; Lakes; Seawater

Quantifying closed-basin lake temperature and hydrology by inversion of oxygen isotope and trace element paleoclimate records - Ibarra, D.E.; Chamberlain, C.P. (American Journal of Science, 2015)
Lake systems are important paleoclimate archives that preserve ecosystem and hydrologic responses to critical periods in Earth history, such as carbon cycle perturbations and glacial-interglacial cycles. Geochemical measurements of biogenic carbonate (for example, δ18O, δ13C, 87Sr/86Sr, [Li], [U], [Sr], and [Mg]) are indicators of hydrologic variability in lake systems throughout the geologic record. In this study, we present a new closed-basin lake modeling approach, HyBIM (the Hydrologic Balance Inverse Model) that employs a system of total differential equations and uses the measured δ18O, Sr/Ca, and Mg/Ca of biogenic carbonate to determine changes in temperature, runoff, and lake evaporation. Using equally-spaced time steps, these equations are simultaneously solved to constrain the hydrologic parameters of the lake as recorded in biogenic carbonate. We use a Monte Carlo approach to account for uncertainty in the input parameters, such as δ18O temperature relationships, partition coefficient uncertainty, and watershed solute chemistry. For illustrative purposes, we apply the model to two ostracod valve datasets covering different timescales: (1) the Cretaceous Songliao Basin, northeast China, and (2) Holocene Lake Miragoane, Haiti. Modern water measurements of water isotopes and cation concentrations from each location are required as model inputs. We compare our modeling results with author interpretations and geologic observations. The modeling approach presented in this study can be applied to other closed-basin lake records, can be modified for other calcifying species (for example, gastropods or mollusks) or with calibration to inorganic lacustrine carbonate. In addition, this approach holds promise for extension with additional proxy measurements (that is, δD, U/Ca or Li/Ca) and changing source area on tectonic timescales using proxies that reflect changing source lithology (that is, Sr and Pb isotopes). Future incorporation of age model uncertainty in the Monte Carlo approach will also provide utility by quantifying temporal uncertainty on the hydrologic response recorded by lake sediments.
cited By 9
Keywords: lacustrine deposit; lake water; oxygen isotope; paleoclimate; paleohydrology; trace element; water chemistry; water quality; water temperature; Gastropoda; Mollusca; Ostracoda

Progress of reactive iron burial in the marine and terrestrial sediments with its implications to the genesis of source rock in Songliao Basin (in Chinese with English abstract);[海陆相活性铁埋藏研究进展及其对松辽盆地烃源岩成因的启示] - Huang, Y.; Wang, C. (Chinese Journal of Nature, 2015)

Present and future of subsurface biosphere studies in lacustrine sediments through scientific drilling - Ariztegui, D.; Thomas, C.; Vuillemin, A. (International Journal of Earth Sciences, 2015)
Recently, the discovery of active microbial life in deep-sea sediments has triggered a rapid development of the field known as the “deep biosphere.” Geomicrobiological investigations in lacustrine basins have also shown a substantial microbial impact on lake sediments similar to that described for the marine record. Although only 30 % of the lake sites drilled by the International Continental Drilling Program (ICDP) have included microbial investigations, these lakes cover a relatively wide range of salinities (from 0.15 to 33.8 %), pH (from 6.0 to 9.8) and environmental conditions (from very arid to humid subtropical conditions). Here, we analyze results of very recent ICDP lake sites including subsurface biosphere research from southern Patagonia (Laguna Potrok Aike) to the Levantine area (Dead Sea) as well as the East Anatolian high plateau (Lake Van) and Macedonia (Lake Ohrid). These various settings allow the examination of the impact of contrasting environments on microbial activity and their subsequent role during early diagenesis. Furthermore, they permit the identification of biosignatures of former microbial activity recorded in the sediments as well as investigating the impact of microbes in biogeochemical cycles. One of the general outcomes of these preliminary investigations is data to support the hypothesis that microbes react to climatically driven environmental changes that have a direct impact on their subsurface distribution and diversity. This is clear at conspicuous levels associated with well-known climatic periods such as the Medieval Climatic Anomaly or the Little Ice Age. Although more research is needed, this relationship between prevailing microbial assemblages and different climatic settings appears to dominate the lacustrine sites studied until to date. © 2015, The Author(s).
cited By 18
Keywords: biosphere; deep-sea sediment; diagenesis; drilling; environmental change; genomics; geological record; geomicrobiology; lacustrine deposit; microbial activity; paleoclimate; sedimentary basin; Argentina; Dead Sea; Laguna Potrok Aike; Lake Ohrid; Lake Van; Levantine Sea; Mediterranean Sea; Patagonia; Santa Cruz [Argentina]; Turkey

Present and future of subsurface biosphere studies in lacustrine sediments through scientific drilling - Ariztegui, Daniel; Thomas, Camille; Vuillemin, Aurèle (International Journal of Earth Sciences, 2015)

Operational report about phase 1 of the Collisional Orogeny in the Scandinavian Caledonides scientific drilling project (COSC-1) - Lorenz, H.; Rosberg, J. E.; Juhlin, C.; Bjelm, L.; Almquist, B.; Berthet, T.; Conze, R.; Gee, D.; Klonowska, I.; Pascal, C.; Pedersen, K.; Roberts, N.; et al. (2015)
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Present and future of subsurface biosphere studies in lacustrine sediments through scientific drilling - Ariztegui, Daniel; Thomas, Camille; Vuillemin, Aurèle (International Journal of Earth Sciences, 2015)
Recently, the discovery of active microbial life in deep-sea sediments has triggered a rapid development of the field known as the “deep biosphere.” Geomicrobiological investigations in lacustrine basins have also shown a substantial microbial impact on lake sediments similar to that described for the marine record. Although only 30 % of the lake sites drilled by the International Continental Drilling Program (ICDP) have included microbial investigations, these lakes cover a relatively wide range of salinities (from 0.15 to 33.8 %), pH (from 6.0 to 9.8) and environmental conditions (from very arid to humid subtropical conditions). Here, we analyze results of very recent ICDP lake sites including subsurface biosphere research from southern Patagonia (Laguna Potrok Aike) to the Levantine area (Dead Sea) as well as the East Anatolian high plateau (Lake Van) and Macedonia (Lake Ohrid). These various settings allow the examination of the impact of contrasting environments on microbial activity and their subsequent role during early diagenesis. Furthermore, they permit the identification of biosignatures of former microbial activity recorded in the sediments as well as investigating the impact of microbes in biogeochemical cycles. One of the general outcomes of these preliminary investigations is data to support the hypothesis that microbes react to climatically driven environmental changes that have a direct impact on their subsurface distribution and diversity. This is clear at conspicuous levels associated with well-known climatic periods such as the Medieval Climatic Anomaly or the Little Ice Age. Although more research is needed, this relationship between prevailing microbial assemblages and different climatic settings appears to dominate the lacustrine sites studied until to date. © 2015, The Author(s).
Keywords: Argentina; Dead Sea; Laguna Potrok Aike; Lake Ohrid; Lake Van; Levantine Sea; Mediterranean Sea; Patagonia; Santa Cruz [Argentina]; Turkey; biosphere; deep-sea sediment; diagenesis; drilling; environmental change; genomics; geological record; geomicrobiology; lacustrine deposit; microbial activity; paleoclimate; sedimentary basin

Platinum group elements in proximal impactites of the bukit bunuh impact structure, Malaysia - Quek, L.X.; Ghani, A.A.; Badruldin, M.H.; Saidin, M.; Harith, Z.Z.T.; Roselee, M.H. (Current Science, 2015)
The Bukit Bunuh in Malaysia has recently been identified as an impact structure after the discovery of possible impact-melt-like rocks and impact breccias from this area. The impact event is believed to have occurred around 1.34-1.84 Ma. Twelve impact-related rocks from this suspected impact structure were analysed in the present study for platinum group of element (PGE) content. The sample population includes proximal impactites (two impact-melt rocks and three impact breccias) and possible impact-related rocks (four mylonites) and basement granite (three in number). The results showed no observable clear distinction between the impactites and basement granite. Compared to other asteroid impact sites in the world, the impactites and impact-related rocks in the Bukit Bunuh structure clearly contain a lower concentration of PGEs. Even though previous studies reported possible evidences of shock metamorphism in the Bukit Bunuh structure and electrical resistivity survey favoured the presence of asteroid impact structure in this area as well, the absence of a clear projectile signature in our study on PGE hinders further discussion on the existence and nature of the impact. We suggest that the absence of any PGE signature in the Bukit Bunuh impactites could be indicative either of (1) an achondrite projectile, or (2) an oblique impact or (3) the presence of a volatile-rich layer.
cited By 0

Petrography and composition of Martian regolith breccia meteorite Northwest Africa 7475 - Wittmann, A.; Korotev, R.L.; Jolliff, B.L.; Irving, A.J.; Moser, D.E.; Barker, I.; Rumble, D. (Meteoritics and Planetary Science, 2015)
The Northwest Africa (NWA) 7475 meteorite is one of the several stones of paired regolith breccias from Mars based on petrography, oxygen isotope, mineral compositions, and bulk rock compositions. Its inventory of lithic clasts is dominated by vitrophyre impact melts that were emplaced while they were still molten. Other clast types include crystallized impact melt rocks, evolved plutonic rocks, possible basalts, contact metamorphosed rocks, and siltstones. Impact spherules and vitrophyre shards record airborne transport, and accreted dust rims were sintered on most clasts, presumably during residence in an ejecta plume. The clast assemblage records at least three impact events, one that formed an impact melt sheet on Mars ≤4.4 Ga ago, a second that assembled NWA 7475 from impactites associated with the impact melt sheet at 1.7-1.4 Ga, and a third that launched NWA 7475 from Mars 5 Ma ago. Mildly shocked pyroxene and plagioclase constrain shock metamorphic conditions during launch to >5 and <15 GPa. The mild postshock-heating that resulted from these shock pressures would have been insufficient to sterilize this water-bearing lithology during launch. Magnetite, maghemite, and pyrite are likely products of secondary alteration on Mars. Textural relationships suggest that calcium-carbonate and goethite are probably of terrestrial origin, yet trace element chemistry indicates relatively low terrestrial alteration. Comparison of Mars Odyssey gamma-ray spectrometer data with the Fe and Th abundances of NWA 7475 points to a provenance in the ancient southern highlands of Mars. Gratteri crater, with an age of 5 Ma and an apparent diameter of 6.9 km, marks one possible launch site of NWA 7475. © The Meteoritical Society, 2015.
cited By 76

Peralkaline felsic magmatism at the Nemrut volcano, Turkey: impact of volcanism on the evolution of Lake Van (Anatolia) IV - Macdonald, R.; Sumita, M.; Schmincke, H.-U.; Bagi'nski, B.; White, J.C.; Ilnicki, S.S. (Contributions to Mineralogy and Petrology, 2015)
Nemrut volcano, adjacent to Lake Van (Turkey), is one of the most important peralkaline silicic centres in the world, where magmatism for 570,000 years has been dominated by peralkaline trachytes and rhyolites. Using onshore and Lake Van drill site tephra samples, we document the phenocryst and glass matrix compositions, confirming a complete spectrum from very rare mafic to dominantly silicic magmas. Magma mixing has been common and, along with the multi-lineage nature of the magmas, indicates that Nemrut has been a very open system where, nevertheless, compositionally zoned caps developed during periods of relative eruptive quiescence. Geothermometry suggests that the intermediate-silicic magmas evolved in an upper crustal magma reservoir at temperatures between 1100 and 750 °C, at fO2 close to the FMQ buffer. The silicic magmas either were halogen poor or exsolved a halogen-rich phase prior to or during eruption. An unusual Pb-rich phase, with up to 98.78 wt% PbO, is interpreted as having exsolved from the intermediate-rhyolitic magmas. © 2015, The Author(s).
cited By 18
Keywords: felsic rock; geothermometry; glass; magmatism; peralkaline rock; phenocryst; rhyolite; tephra; trachyte; Bitlis; Lake Van; Nemrut; Turkey; Trachytes

Paleoarchean sulfur cycling: Multiple sulfur isotope constraints from the Barberton Greenstone Belt, South Africa - Montinaro, Alice; Strauss, Harald; Mason, Paul R.D.; Roerdink, Desiree; M{unker, Carsten; Schwarz-Schampera, Ulrich; Arndt, Nicholas T.; Farquhar, James; Beukes, Nicolas J.; Gutzmer, Jens; Peters, Marc (Precambrian Research, 2015)
Mass-dependent and mass-independent sulfur isotope fractionation archived in volcanic and sedimentary rocks from the Barberton Greenstone Belt (3550-3215. Ma), South Africa, provide constraints for sulfur cycling on the early Earth. Four different sample suites were studied: komatiites and tholeiites, barite, massive and disseminated sulfide ores, and non-mineralized black shales.Variable but generally slightly positive δ34S values between -0.7 and +5.2‰, negative δ33S values between -0.50 and -0.09‰, and a negative correlation between δ34S and δ33S as well as between δ33S and δ36S for komatiites and tholeiites from the Komati Formation and from the Weltevreden Formation are outside the expected range of unfractionated juvenile sulfur. Instead, results suggest alteration of oceanic crustal rock sulfur through interactions with fluids that most likely derived their sulfur from seawater.Barite from the Mapepe Formation displays positive δ34S values between +3.1 and +8.1‰ and negative δ33S values between -0.77 and -0.34‰. The mass-independent sulfur isotope fractionation indicates an atmospheric sulfur source, notably photolytic sulfate, whereas the positive δ34S values suggest bacterial sulfate reduction of the marine sulfate reservoir.Non-mineralized black shale samples from the presumed stratigraphic equivalent of the Mapepe Formation show positive δ34S values between 0.0 and +1.3‰ and positive δ33S values between +0.59 and +2.45‰. These results are interpreted to result from the reduction of photolytic elemental sulfur, carrying a positive δ33S signature.Positive δ34S values ranging from +0.7 to +3.5‰ and slightly negative δ33S values between -0.17 and -0.12‰ characterize massive and disseminated sulfides from the Bien Venue Prospect. Results suggest unfractionated juvenile magmatic sulfur source as the primary sulfur source, but a contribution from recycled seawater sulfate, which would be indicative of submarine hydrothermal activity, cannot be ruled out.Massive and disseminated sulfides from the M'hlati prospect are distinctly different from massive and disseminated sulfide from the Bien Venue Prospect. They show negative δ34S values between -1.2 and -0.1‰ and positive δ33S values between +2.66 and +3.17‰, thus, displaying a sizeable mass-independent sulfur isotopic fractionation. Again, these samples clearly exhibit the incorporation of an atmospheric MIF-S signal. The source of sulfur for these samples has positive δ33S values, suggesting a connection with photolytic elemental sulfur.In conclusion, the sulfur isotope signatures in Paleoarchean rocks from the Barberton Greenstone Belt are diverse and indicate the incorporation of different sources of sulfur. For komatiites and tholeiites, barite and massive and possibly also disseminated sulfides from Bien Venue, multiple sulfur isotopes are related to ambient seawater sulfate and its photolytic origin, while massive and disseminated sulfides from M'hlati and non-mineralized black shales are related to a second (photolytic elemental sulfur) end member. © 2015 Elsevier B.V.
Keywords: Barberton Greenstone Belt; Bacteria (microorganisms); Archean; black shale; hydrochemistry; isotopic fractionation; komatiite; oceanic crust; paleoceanography; reduction; seawater; sulfate; sulfur isotope

Otolith microchemistry of modern versus well-dated ancient naked carp Gymnocypris przewalskii: Implication for water evolution of Lake Qinghai - Zhou, Ling; Jin, Zhangdong; Wang, Chia-Hui; Li, Fuchun; Wang, Yujiao; Wang, Xulong; Zhang, Fei; Chen, Liumei; Du, Jinhua (Journal of Asian Earth Sciences, 2015)
There is ongoing debate over how the water level and composition of the water in Lake Qinghai changed in the past and might change in future. This study of the microchemistry of otoliths from ancient naked carp explores the chemistry of a relict lake isolated from Lake Qinghai during the Little Ice Age (LIA). A close correlation between the ages measured on fish bone and otoliths by AMS-14C, and by optically stimulated luminescence on overlying sediments, confirms a high water level in Lake Qinghai before 680-300years ago. The contrasting compositions of the ancient otoliths relative to modern otoliths and waters indicate that the relict lake became enriched in 18O, Mg, Li, B and to a lesser extent Ba, but depleted in 13C, owing to strong evaporation, authigenic carbonates precipitation, (micro-)organism activity, and less fresh water input after it was isolated. If there were long-term fresh water input, however, a reverse trend might occur. The most important observation is that, because the waters have been supersaturated with respect to carbonates, authigenic carbonate precipitation would result in low but consistent Sr/Ca ratios in the lakes, as recorded by both the ancient and modern otoliths. The geochemical records of ancient versus modern biogenic carbonates provide insights into the long-term hydroclimatic evolution processes of an inland water body. © 2015 Elsevier Ltd.

Nucleation process of an M2 earthquake in a deep gold mine in South Africa inferred from on-fault foreshock activity - Yabe, Y.; Nakatani, M.; Naoi, M.; Philipp, J.; Watanabe, T.; Katsura, T.; Kawakata, H.; Georg, D.; Ogasawara, H. (Journal of Geophysical Research: Solid Earth, 2015)
Using a network of sensitive high-frequency acoustic emission sensors, we observed foreshock activity of an Mw 2.2 earthquake (main shock) in a deep gold mine in South Africa. Foreshock activity, which selectively occurred on a part of the rupture plane of the forthcoming main shock, lasted for at least 6 months until the main shock. Rock samples recovered from the main shock source region showed evidence of ancient hydrothermal alteration on the main shock rupture plane, suggesting that the foreshock activity occurred on a preexisting weakness. The foreshocks during 3 months before the main shock were concentrated in three clusters (F1-F3), which we interpret as representing localized preslip at multiple sites. While the location of mining area, the source of stress perturbations, changed with time, the locations of foreshock clusters did not change, suggesting that the preslip patches were controlled by strength heterogeneity rather than stress distribution. Activity over the entire foreshock area was generally constant, but the largest cluster (F2) showed accelerated activity starting at least 7 days before the main shock, while mining stress did not increase in this period. The main shock initiated at a point close to F1, away from F2. All the six foreshocks during the final 41 h occurred in F1 and F2 and in-between. These suggest that in the last stage of the preparation process of the main shock, preslip patches interacted with each other through the stress concentration ahead of the expanding preslip patch (F2), which should be the only driving force of the preparation process under the constant external load. ©2015. American Geophysical Union. All Rights Reserved.
cited By 22
Keywords: acoustic emission; earthquake magnitude; earthquake rupture; fault; foreshock; gold mine; hydrothermal alteration; mining-induced seismicity; nucleation; South Africa

Multiple Palaeoproterozoic carbon burial episodes and excursions - Martin, Adam P; Prave, AR; Condon, DJ; Lepland, Aivo; Fallick, Anthony E; Romashkin, AE; Medvedev, PV; Rychanchik, DV (Earth and Planetary Science Letters, 2015)

Morphologic and structural mapping of the central uplift of Betiocrater, Thaumasia Planum, Mars - Nuhn, A.M.; Tornabene, L.L.; Osinski, G.R.; McEwen, A.S. (Special Paper of the Geological Society of America, 2015)
The 31.7-km-diameter Betio crater (23.15°S, 281.38°E), located within the Hesperian-aged Ridged Plains material in Thaumasia Planum, Mars, contains a wellpreserved asymmetrical central floor pit ( 10.8 km NW-SE and 8.8 km NE-SW in diameter) covering an area of 67 km2 that exposes discrete megablocks of layered bedrock and preserves a variety of impact-generated deposits. High-resolution images taken by the Mars Reconnaissance Orbiter (MRO) are combined with other data sets to study and map the morphology and structure of the central floor pit. The excellent bedrock exposure of the floor pit enables the comparison of mapped structures with observations from terrestrial craters. Our mapping of the central uplift has revealed a variety of faults, folds (likely radial transpression ridges), and many breccia dikes, in addition to different types of impactites (e.g., breccias, impact melt deposits, and uplifted bedrock [i.e., parautochthonous bedrock]). Through structural mapping, we show that the central portion of the central uplift is characterized by smaller ( 60- 300 m in diameter) blocks with high dips of 45°-85°, and the outer sections of the floor pit have larger (>800 m in diameter) blocks with shallow dip angles of 5°-15°. Our work shows that extensive brittle deformation and brecciation increase toward the center of the crater and particularly in the SW sector of the central pit. There is also an overall decrease in block size toward the center of the crater. © 2015 The Geological Society of America. All rights reserved.
cited By 4

Mineralogy and petrology of the Paleocene Clayton and Porters Creek Formations, Missouri, USA: Influence of Cretaceous-Paleogene impact debris and diagenesis - Larsen, D.; Ashe, D.J.; Gustavson, J. (Special Paper of the Geological Society of America, 2015)
The origin of clays and clay minerals in the Paleocene Clayton (CF) and Porters Creek (PCF) Formations within the Mississippi embayment of central North America has been debated for more than 50 years. X-ray diffraction and petrographic analysis of samples of the CF and PCF from a mine in southeastern Missouri are used to evaluate contributions from Cretaceous-Paleogene (K-Pg) impact debris and the role of sediment diagenesis in the fine-grained sediment. Expandable clay minerals increase in abundance relative to illite and kaolinite above the K-Pg unconformity in the CF and PCF, and include dioctahedral smectite, vermiculite, and minor mixed-layered clay components, along with trioctahedral smectitic clays in the CF and lowermost PCF. Additional diagenetic phases include clinoptilolite (in the CF and lower PCF), pyrite, siderite, and opal CT (mainly in the PCF). The results of the petrographic analysis show no evidence for volcanic ash contributing directly to the sediment in the PCF. The detrital silicate minerals are mainly quartz, muscovite, biotite, and metamorphic minerals, consistent with an ancestral Appalachian Mountains source rather than volcanic ash or a Cretaceous western interior sediment source. The illite, kaolinite, dioctahedral smectite, and ordered illite-smectite mixed-layered clays are present in varying quantities in Cretaceous through Paleogene marine and nonmarine mudstones from the Mississippi embayment, and appear to be detrital in origin. Trioctahedral smectite and clinoptilolite in the CF and lowermost PCF are argued to derive from alteration of glassy impact debris; clasts in the basal CF contain microtektites replaced by trioctahedral smectitic mixed-layered clay with randomly interstratified illite. The X-ray diffraction characteristics of the vermiculite in the PCF indicate a hydroxyl-interlayered aluminous variety that is argued to have a diagenetic origin, formed by clay mineral reactions under variably anoxic conditions in the PCF sediments during early diagenesis. Throughout the CF and PCF, pyrite precipitated under reducing conditions during diagenesis, locally along with siderite replacement of micritic carbonate. In addition, opal-CT precipitated as a result of silicate reactions and dissolution of diatoms under alkaline conditions and replaced matrix and calcitic microfossils throughout much of the upper PCF. © 2015 The Geological Society of America. All rights reserved.
cited By 0

Mineralogical, geochemical and isotopic features of tuffs from the CFDDP drill hole: Hydrothermal activity in the eastern side of the Campi Flegrei volcano (southern Italy) - Mormone, A.; Troise, C.; Piochi, M.; Balassone, G.; Joachimski, M.; De Natale, G. (Journal of Volcanology and Geothermal Research, 2015)
A 506. m drill-hole has been recently drilled in the framework of the Campi Flegrei Deep Drilling Project (CFDDP) and the International Continental Scientific Drilling Program (ICDP) with the intention of coring the subsurface in the eastern sector of the Campi Flegrei caldera. The borehole, located in the western district of the Neapolitan city (Bagnoli Plain) 3. km to the east of the most active volcanic area and about 5. m above sea level, is now targeted for monitoring purposes.This paper reports the results obtained from the analysis of two short cores collected at depths of -443 and -506m below the ground level. The cores sampled two pre-caldera tuffs. Observations performed by optical and scanning electron microscopy, energy dispersive spectroscopy and powder X-ray diffraction were used to achieve data on the primary lithology, both primary and secondary mineralogical assemblages, and the relationship between texture and secondary mineralization. Sr isotope ratios were determined on selected primary feldspars, whereas δ13C and δ18O analyses were performed on carbonates from veins and filled-voids in tuffs.Our results provide information on the hydrothermal system in the eastern sector of the caldera that was not among the goals in the previous drilling programs. Secondary mineralization suggests a saline hydrothermal environment characterized by fluids that progressively evolved from boiling toward more alkaline and cooler conditions. A paleo-temperature of ca. 160. °C has been inferred from authigenic mineral occurrences and calculated on the basis of equilibria between cored calcites and fluids presently emitted at the surface, by using carbon and oxygen isotope data. The temperature measured at the bottom of the drilling is about 80. °C. © 2014 The Authors.
Keywords: Bagnoli; Campania [Italy]; Campi Flegrei; Italy; Naples; Napoli [Campania]; C (programming language); Core samples; Drills; Energy dispersive spectroscopy; Geothermal fields; Isotopes; Lithology; Mineralogy; Rock drills; Scanning electron microscopy; Sea level; Strontium; Volcanoes; X ray diffraction; Authigenic minerals; Campi Flegrei; Carbon and oxygen isotopes; Continental scientific drillings; Hydrothermal activity; Hydrothermal environment; Pilot holes; Powder X ray diffraction; borehole; caldera; deep drilling; geothermal system; hydrothermal activity; hydrothermal system; isotopic ratio; mineralization; strontium isotope; temperature; tuff; Boreholes

Mid-latitude terrestrial climate of East Asia linked to global climate in the Late Cretaceous - Gao, Y.; Ibarra, D.E.; Wang, C.; Caves, J.K.; Chamberlain, C.P.; Graham, S.A.; Wu, H. (Geology, 2015)
The Late Cretaceous (late Campanian to Maastrichtian) was characterized by a variable greenhouse climate, with evidence for cooling and/or glaciation and warming events. Most of these climatic signals are derived from marine records, and knowledge of the terrestrial climate, especially in the mid-latitudes, is limited due to fragmentary geological records on continents. Here we report mid-latitude terrestrial stable oxygen and carbon isotope data from pedogenic carbonates in the nearly continuous Late Cretaceous age SK-1 core drilled in the Songliao Basin, northeastern China. Our data indicate a punctuated, mid-latitude terrestrial climate in the Late Cretaceous. We interpret the negative excursion of pedogenic carbonate δ18O in the early Maastrichtian to be the result of decreasing temperature and/or strengthened westerlies during global cooling and possible glaciation, providing valuable mid-latitude terrestrial evidence for this event. The negative δ13C isotopic excursion ca. 66 Ma is modeled as higher primary productivity caused by increasing temperature and precipitation in response to a warming climate in the latest Cretaceous. Our continuous stable isotopic records in the Songliao Basin are in accordance with previously published global Late Cretaceous records of climate variability from marine and terrestrial regions, and demonstrate the sensitivity of mid-latitude terrestrial climate in a greenhouse world. © 2015 Geological Society of America.
cited By 66
Keywords: Greenhouses; Isotopes; Temperature; Carbon isotopes; Climate variability; Climatic signals; Greenhouse climates; Increasing temperatures; Pedogenic carbonates; Primary productivity; Warming climate; Glacial geology; carbon isotope; carbonate; climate variation; Cretaceous; global climate; midlatitude environment; oxygen isotope; paleoclimate; stable isotope; China; Far East; Songliao Basin

Micromechanisms of creep in clay-rich gouge from the Central Deforming Zone of the San Andreas Fault - French, M.E.; Chester, F.M.; Chester, J.S. (Journal of Geophysical Research: Solid Earth, 2015)
We report the strength and constitutive behavior of gouge sampled from the Central Deforming Zone (CDZ) of the San Andreas Fault. Layers of flaked CDZ gouge were sheared in the triaxial saw cut configuration using the stress relaxation technique to measure the gouge strength over 4 orders of magnitude in shear strain rate and at rates as low as 5 × 10-10s-1 and within an order of magnitude of in situ rates. Deformation conditions correspond to the in situ effective normal stress (100 MPa) and temperature (65 to 120C) at the sampling depth of 2.7 km. Gouge was sheared dry and with brine pore fluid at 25 MPa pore pressure. Dry gouge is stronger and more rate strengthening than brine-saturated gouge. Brine-saturated CDZ gouge strengthens with increasing strain rate and decreasing temperature, and the dependencies of strength on strain rate and temperature increase at rates below ∼5 × 10-9s-1. At strain rates greater than ∼5 × 10-9s-1, the rate dependence is consistent with previous studies on the CDZ gouge conducted at even higher rates. The increase in rate dependence below ∼5 × 10-9s-1 indicates a change in the rate-controlling deformation mechanism. The magnitude of the friction rate dependence parameter, a, and the temperature sensitivity of a are consistent with crystal plasticity of the phyllosilicates. We hypothesize a micromechanical model for the CDZ gouge whereby a transition from fracture and delamination-accommodated frictional flow to crystal plasticity-accommodated frictional flow occurs with decreasing strain rate. © 2015. American Geophysical Union. All Rights Reserved.
cited By 35
Keywords: clay; creep; deformation mechanism; fault gouge; fault zone; micromechanics; microstructure; San Andreas Fault; strain rate; stress field; California; San Andreas; United States

Seismic imaging of the geodynamic activity at the western Eger rift in central Europe - Mullick, N.; Buske, S.; Hrubcov'a, P.; Ruzek, B.; Shapiro, S.; Wigger, P.; Fischer, T. (Tectonophysics, 2015)
The western Eger rift at the Czech-German border in central Europe is an important geodynamically active area within the European Cenzoic rift system (ECRS) in the forelands of the Alps. Along with two other active areas of the ECRS, the French Massif Central and the east and west Eifel volcanic fields, it is characterized by numerous CO2-rich fluid emission points and frequent micro-seismicity. Existence of a plume(s) is indicated in the upper mantle which may be responsible for these observations. Here we reprocess a pre-existing deep seismic reflection profile '9HR' and interpret the subsurface structures as mapped by seismic reflectivity with previous findings, mainly from seismological and geochemical studies, to investigate the geodynamic activity in the subsurface. We find prominent hints of pathways which may allow magmatic fluids originating in the upper mantle to rise through the crust and cause the observed fluid emanations and earthquake activity. © 2015 Elsevier B.V.
Keywords: Alps; Bohemian Massif; Eger; Eifel; France; Germany; Heves; Hungary; Massif Central; Rhineland-Palatinate; Earthquakes; Bohemian massifs; Crustal fluids; Deep seismic reflection profiles; Earthquake activity; Eger rift; Rift systems; Seismic reflectivity; Subsurface structures; Cenozoic; earthquake swarm; geodynamics; rift zone; seismic reflection; seismicity; seismology; upper mantle; Geodynamics

Sedimentary and tectonic evolution of Lake Ohrid (Macedonia/Albania) - Lindhorst, Katja; Krastel, S.; Reicherter, K.; Stipp, M.; Wagner, B.; Schwenk, T. (Basin Research, 2015)
Lake Ohrid, located on the Balkan Peninsula within the Dinaride-Albanide-Hellenide mountain belt, is a tectonically active graben within the South Balkan Extensional Regime (SBER). Interpretation of multichannel seismic cross sections and bathymetric data reveals that Lake Ohrid formed during two main phases of deformation: (1) a transtensional phase which opened a pull-apart basin, and (2) an extensional phase which led to the present geometry of Lake Ohrid. After the initial opening, a symmetrical graben formed during the Late Miocene, bounded by major normal faults on each side in a pull-apart type basin. The early-stage geometry of the basin has a typical rhomboidal shape restricted by two sets of major normal faults. Thick undisturbed sediments are present today at the site where the acoustic basement is deepest, illustrating that Lake Ohrid is a potential target for drilling a long and continuous sediment core for studying environmental changes within the Mediterranean region. Neotectonic activity since the Pliocene takes place along the roughly N-S-striking Eastern and Western Major Boundary Normal Faults that are partly exposed at the present lake floor. The tectono-sedimentary structure of the basin is divided into three main seismic units overlying the acoustic basement associated with fluvial deposits and lacustrine sediments. A seismic facies analysis reveals a prominent cyclic pattern of high- and low-amplitude reflectors. We correlate this facies cyclicity with vegetation changes within the surrounding area that are associated with glacial/interglacial cycles. A clear correlation is possible back to ca. 450 kyrs. Extrapolation of average sedimentation rates for the above mentioned period results in age estimate of ca. 2 Myrs for the oldest sediments in Lake Ohrid. © 2014 The Authors.
Keywords: Albania; Lake Ohrid; Macedonia [Southern Europe]; facies analysis; neotectonics; normal fault; sedimentary structure; sedimentation rate; tectonic evolution

The distribution of polycyclic aromatic hydrocarbons (PAHs) in sediments from Upper Cretaceous Nenjiang Formation of Songliao Basin and its paleoclimate significance - Cao, XX; Li, Y; Wang, L; Yin, Q; Song, ZG; Zhao, DF (Geochimica, 2015)

Seismic imaging through the volcanic rocks of the Snake River Plain: Insights from Project Hotspot - Liberty, L.M.; Shervais, J.W. (Geophysical Prospecting, 2015)
Hotspot: The Snake River Geothermal Drilling Project was undertaken to better understand geothermal systems across the Snake River Plain volcanic province. A series of surface and borehole seismic profiles were obtained to provide insights into volcanic stratigraphy and test the capabilities of engineering-scale seismic imaging in such terranes. The Kimberly site drilled through 1.9 km of mostly rhyolite, with thin sedimentary interbeds in the upper part of the section. The Kimama site drilled through 1.9 km of mostly basalt with sedimentary interbeds at ∼200 m depth and 1700 m depth. The Mountain Home site contained numerous sediment and volcanic rock layers. Downhole and surface vibroseis seismic results suggest sedimentary interbeds at depth correspond with low-velocity, high-temperature zones that relate to reflections on seismic profiles. Our results suggest that eruption flow volumes can be estimated and flow boundaries can be imaged with surface seismic methods using relatively high-fold and wide-angle coverage. High-frequency attenuation is observed at all sites, and this deficit may be countered by acquisition design and a focus on signal processing steps. Separation of surface and body waves was obtained by muting, and the potential for large static effects was identified and addressed in processing. An accurate velocity model and lithology contacts derived from borehole information improved the confidence of our seismic interpretations. © 2015 European Association of Geoscientists & Engineers.
cited By 3
Keywords: Boreholes; Geothermal fields; Geothermal wells; Infill drilling; Lithology; Rivers; Sedimentology; Seismic waves; Seismology; Signal processing; Stratigraphy; Volcanoes; Geothermal; Geothermal drilling; Geothermal systems; High frequency attenuation; High temperature zones; Seismic imaging; Seismic interpretation; Snake river plains; Volcanic rocks; body wave; borehole; data interpretation; geothermal system; imaging method; seismology; signal processing; volcanic rock; Idaho; Snake River Plain; United States

The organic geochemical evidences for the lake water stratification in Lower Nenjiang Formation, Songliao Basin - Liu, Meiyu; Hu, Jianfang; Xiaoqiao, Wan (Journal of Lake Sciences, 2015)

Zero-Offset VSP in the COSC-1 borehole - Krau{s, Felix; Simon, Helge; Giese, R{udiger; Hedin, Peter; Juhlin, Christopher; Lorenz, Henning (Geophysical Research Abstracts, 2015)
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When was the Earth's conveyor belt set in motion? - Puchtel, Igor S. (American Mineralogist, 2015)
The start of plate tectonics on Earth is one of the most controversial issues in modern geology, with proposed timings covering almost the entire history of our planet. On page 2387 of this issue (vol. 100, 2015), Blichert-Toft and co-authors report Sm-Nd and Lu-Hf isotopic and lithophile trace element data for early Archean komatiites from the Barberton Greenstone Belt (GB) in South Africa, and argue for the onset of plate tectonics on Earth as early as 3.5 Ga. The studied komatiites show a large decoupling of the two isotopic systems and lithophile trace element signatures that are most consistent with deep-water, pelagic sediments being present in the lower-mantle source of these lavas. Their conclusions have far-reaching implications for advancing our understanding of how the Earth system operated in the distant geological past. © Walter de Gruyter Berlin/Boston 2015.
Keywords: Barberton Greenstone Belt; Belt conveyors; Binary alloys; Earth (planet); Isotopes; Lutetium alloys; Neodymium alloys; Samarium alloys; Tectonics; Trace elements; Barberton; Conveyor belts; Element signatures; Greenstone belts; Hf isotope; Isotopic systems; Pelagic sediments; subduction; greenstone belt; hafnium; isotopic analysis; komatiite; lutetium; neodymium; plate tectonics; samarium-neodymium dating; subduction; Hafnium alloys

Volatiles in magmas related to the Campanian Ignimbrite eruption: Experiments vs. natural findings - Fanara, Sara; Botcharnikov, Roman E.; Palladino, Danilo M.; Adams, Franziska; Buddensieck, Julia; Mulch, Andreas; Behrens, Harald (American Mineralogist, 2015)
The solubility of H2O- and CO2-bearing fluids in trachytic and trachybasaltic melts from erupted magmas of the Campi Flegrei Volcanic District has been investigated experimentally at 1100 and 1200 °C, respectively, and at 100, 200, 300, 400, and 500 MPa. The solubility of H2O in the investigated melts varies between 3.48 ± 0.07 wt% at 100 MPa to 10.76 ± 0.12 wt% at 500 MPa in trachytic melts and from 3.49 ± 0.07 wt% at 100 MPa to 9.10 ± 0.11 wt% at 500 MPa in trachybasaltic melts. The content of dissolved CO2 in melts coexisting with the most CO2-rich fluid phase increases from 281 ± 24 ppm at 100 MPa to 2710 ± 99 ppm at 500 MPa in trachyte, and from 727 ± 102 ppm at 100 MPa to 3565 ± 111 ppm at 500 MPa in trachybasalt. Natural samples from the Campanian Ignimbrite eruption (trachyte) and from the Solchiaro eruption (trachybasalt) were collected around the city of Naples and on Procida Island. Deuterium/hydrogen (D/H) ratios were analyzed in natural pumices pre-heated at different temperatures to remove water adsorbed and/or imprinted by glass alteration processes. It has been determined that heating of the glass to 350 °C efficiently removes most of secondary water and the remaining concentrations represent primary magmatic water preserved in the erupted material. Hydrogen isotope composition (with δD values ranging between -70‰ and -110‰) and its correlation with bulk water content in selected pumice samples of the Campanian Ignimbrite eruption are consistent with isotopic fractionation between magmatic fluid and melt during degassing of erupting magma. Hence, the H2O and CO2 contents in natural glasses from pumice samples are considered as minimum estimates on volatile concentrations in the melt just prior to the eruption or at the fragmentation event. The water contents in natural glasses vary from 0.83 ± 0.07 to 3.74 ± 0.06 wt% for trachytes from the Campanian Ignimbrite eruption and from 1.96 ± 0.06 to 3.47 ± 0.07 wt% for trachybasalts from the Solchiaro eruption. The CO2 contents vary from 78 ± 120 ppm CO2 to 1743 ± 274 ppm for trachytes from the Campanian Ignimbrite eruption and from 240 ± 293 to 1213 ± 250 ppm for trachybasalts from the Solchiaro eruption. A combination of natural and experimental data provides minimum pressure estimates for the storage and ascent conditions of magmas. The Campanian Ignimbrite magma could have been stored or ponded during its rising path at two different levels: a deeper one corresponding to depth of about 8 to 15 km and a shallower one at about 1 to 8 km. Trachybasalts from Solchiaro erupted from the deepest level of about 11 km with a storage or ponding level at around 2 to 8 km depth. Although an uncertainty of at least a kilometer has to be considered in estimating storage or ponding depths, these estimates point to significantly deeper magmatic sources for both eruptions as those considered previously. © 2015 by Walter de Gruyter Berlin/Boston.
Keywords: Campania [Italy]; Campi Flegrei; Italy; Napoli [Campania]; Trachytes; Carbon dioxide process; Digital storage; Glass; Isotopes; Ponding; Solubility; Storage (materials); Uncertainty analysis; Volcanoes; Water; Campanian Ignimbrite; Hydrogen isotope; Solchiaro eruption; trachybasalt; trachyte; Volcanic district; Campanian; carbon dioxide; hydrogen isotope; ignimbrite; isotopic fractionation; magma chemistry; solubility; trachyte; volatile substance; volcanic eruption; water content; Carbon dioxide

Vegetation and environmental changes during the last interglacial in eastern Anatolia (Turkey): A new high-resolution pollen record from Lake Van - Pickarski, N.; Kwiecien, O.; Djamali, M.; Litt, T. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2015)
A high-resolution multi-proxy record from Lake Van, eastern Anatolia, derived from a lacustrine sequence cored at the 357m deep Ahlat Ridge (AR), allows a comprehensive view of paleoclimate and environmental history in the continental Near East during the last interglacial (LI). We combined paleovegetation (pollen), stable oxygen isotope (δ18Obulk) and XRF data from the same sedimentary sequence, showing distinct variations during the period from 135 to 110ka ago leading into and out of full interglacial conditions. The last interglacial plateau, as defined by the presence of thermophilous steppe-forest communities, lasted ca. 13.5ka, from 129.1-115.6ka BP.The detailed palynological sequence at Lake Van documents a vegetation succession with several climatic phases: (I) the Pistacia zone (ca. 131.2-129.1. ka BP) indicates summer dryness and mild winter conditions during the initial warming, (II) the Quercus-. Ulmus zone (ca. 129.1-127.2. ka BP) occurred during warm and humid climate conditions with enhanced evaporation, (III) the Carpinus zone (ca. 127.2-124.1. ka BP) suggest increasingly cooler and wetter conditions, and (IV) the expansion of Pinus at . 124.1. ka BP marks the onset of a colder/drier environment that extended into the interval of global ice growth. Pollen data suggest migration of thermophilous trees from refugial areas at the beginning of the last interglacial. Analogous to the current interglacial, the migration documents a time lag between the onset of climatic amelioration and the establishment of an oak steppe-forest, spanning 2.1. ka. Hence, the major difference between the last interglacial compared to the current interglacial (Holocene) is the abundance of Pinus as well as the decrease of deciduous broad-leaved trees, indicating higher continentality during the last interglacial. Finally, our results demonstrate intra-interglacial variability in the low mid-latitudes and suggest a close connection with the high-frequency climate variability recorded in Greenland ice cores. © 2015 Elsevier B.V.
cited By 39
Keywords: abundance; climate conditions; climate variation; community structure; coniferous tree; data set; deciduous tree; environmental change; environmental history; lacustrine deposit; Last Interglacial; oxygen isotope; paleoecology; palynology; pollen; proxy climate record; resolution; stable isotope; steppe; succession; temperature effect; vegetation structure; X-ray fluorescence; Anatolia; Arctic; Greenland; Greenland Ice Sheet; Lake Van; Turkey; Carpinus; Pistacia; Quercus; Ulmus

Variation of magnetic properties in sediments from Lake Towuti, Indonesia, and its paleoclimatic significance - Tamuntuan, Gerald; Bijaksana, Satria; King, John; Russell, James; Fauzi, Umar; Maryunani, Khoiril; Aufa, Nurul; Safiuddin, La Ode (Palaeogeography, Palaeoclimatology, Palaeoecology, 2015)
We investigated the mineral-magnetic behavior of sediments from Lake Towuti located in the Eastern Sulawesi Ophiolite belt, Indonesia. Rock magnetic analysis supplemented by X-ray diffraction and scanning electron microscopy analysis were performed on sediment core TOW10-9B from the north basin of Lake Towuti to give insights on the environmental and sedimentary processes controlling the magnetic properties of the sediment and its paleoclimatic significance. The results show that the core has three distinct zones of varying magnetic properties. Careful examination demonstrates that these zones correspond to varying levels of iron oxide dissolution and magnetite precipitation that are climatically and environmentally dependent. The magnetically strongest zone is characterized by weak iron oxide dissolution and intense magnetite precipitation, likely driven by changes in the stratification and/or water level of the lake during dry conditions in Marine Isotope Stage 2 (MIS2) period, whereas the two magnetically weaker zones are characterized by signs of dissolution and correspond to relatively wet conditions, respectively, during Marine Isotope Stage 3 (MIS3) and the Holocene. Although our data show that major changes in concentration dependent parameters, such as magnetic susceptibility and saturation isothermal remanent magnetization (SIRM), in Lake Towuti sediment correlate with changes in regional rainfall, many of the concentration changes are more strongly affected by in situ chemical processes than by changes in erosion and terrestrial sediment supply. These findings urge caution in the interpretation of magnetic mineral concentration profiles as indicators of clastic sediment inputs. © 2014 Elsevier B.V.
Keywords: Greater Sunda Islands; Lake Towuti; Malili Lakes; South Sulawesi; Sulawesi; Sunda Isles; clastic sediment; core analysis; depositional environment; dissolution; Holocene; lacustrine deposit; magnetic mineral; magnetic property; marine isotope stage; ophiolite; paleoclimate; sediment property

Trans-Amazon Drilling Project (TADP): Origins and evolution of the forests, climate, and hydrology of the South American tropics - Baker, P.A.; Fritz, S.C.; Silva, C.G.; Rigsby, C.A.; Absy, M.L.; Almeida, R.P.; Caputo, M.; Chiessi, C.M.; Cruz, F.W.; Dick, C.W.; Feakins, S.J.; Figueiredo, J.; et al. (Scientific Drilling, 2015)
This article presents the scientific rationale for an ambitious ICDP drilling project to continuously sample Late Cretaceous to modern sediment in four different sedimentary basins that transect the equatorial Amazon of Brazil, from the Andean foreland to the Atlantic Ocean. The goals of this project are to document the evolution of plant biodiversity in the Amazon forests and to relate biotic diversification to changes in the physical environment, including climate, tectonism, and the surface landscape. These goals require long sedimentary records from each of the major sedimentary basins across the heart of the Brazilian Amazon, which can only be obtained by drilling because of the scarcity of Cenozoic outcrops. The proposed drilling will provide the first long, nearly continuous regional records of the Cenozoic history of the forests, their plant diversity, and the associated changes in climate and environment. It also will address fundamental questions about landscape evolution, including the history of Andean uplift and erosion as recorded in Andean foreland basins and the development of west-to-east hydrologic continuity between the Andes, the Amazon lowlands, and the equatorial Atlantic. Because many modern rivers of the Amazon basin flow along the major axes of the old sedimentary basins, we plan to locate drill sites on the margin of large rivers and to access the targeted drill sites by navigation along these rivers. © Author(s) 2015.
cited By 9
Keywords: Biodiversity; Drills; Plants (botany); Rivers; Sedimentology; Settling tanks; Brazilian Amazon; Cenozoic history; Drilling projects; Landscape evolutions; Physical environments; Plant diversity; Sedimentary basin; Sedimentary records; Forestry

Tourmaline B-isotopes as tracers of fluid sources in silicified Palaeoarchaean oceanic crust of the Mendon Formation, Barberton greenstone belt, South Africa - Farber, Katja; Dziggel, Annika; Trumbull, Robert B.; Meyer, F. Michael; Wiedenbeck, Michael (Chemical Geology, 2015)
Pervasive silicification is a common phenomenon in Early Archaean volcano-sedimentary sequences, reflecting the interaction between Si-rich fluids and the Archaean oceanic crust. In the Palaeoarchaean Barberton greenstone belt, South Africa, the silicified zones locally contain abundant tourmaline. In order to constrain the source of fluids responsible for the alteration, six tourmaline-bearing samples from the 3.3. Ga Mendon Formation were investigated by in-situ analyses of mineral chemistry and boron isotopes. The samples comprise a silicified, finely laminated sedimentary chert and five highly altered and silicified komatiites. Electron microprobe analysis (EMPA) indicates that tourmaline is mostly dravitic, with one sample between dravite and Mg-foitite. Tourmaline has a weakly-developed patchy colour- and chemical zonation, with variations in Al, Fe and Mg composition. Some samples show strong zoning in Cr-concentration with Cr enrichment in the core, and locally the high-Cr domains are at contacts with other Cr-rich phases such as magnesiochromite and chromian muscovite (fuchsite).Overall, the boron isotope composition (δ11B) ranges from -20.7 to +10.2‰. Two groups of tourmaline are distinguished based on the variation in δ11B ratios within single samples: 1) those with small (<4‰) range in δ11B values (spinifex-textured komatiites and silicified sediment), and 2) those with a large range in δ11B values of up to 18‰ (brecciated and foliated samples). Positive boron isotope values (+6 to +10‰) are found in one spinifex-textured komatiite and are interpreted as being derived from seawater interacting with Archaean oceanic crust in shallow hydrothermal systems. The intermediate boron isotope values (-5 to -8‰) found in all other samples are similar to MORB and may represent boron derived from the Archaean oceanic crust. The rare and exceptionally light boron isotope values (-10 to -21‰) were found in rims of group 2 tourmaline. These values cannot be produced by fractionation alone, and point to the presence of another fluid source. The source of the light boron has yet to be identified, but possible candidates are remobilized boron either derived from granitic crust or from marine evaporites that precipitated from seawater enriched in 10B. In any case, the isotopically light boron appears to have been present during seafloor hydrothermal alteration and deposition of the Mendon Formation at ca. 3.3Ga. © 2015 Elsevier B.V.
Keywords: Barberton Greenstone Belt; Chemical analysis; Clay alteration; Electron probe microanalysis; Isotopes; Magnesium; Mica; Microanalysis; Seawater; Secondary ion mass spectrometry; Sedimentology; Silicate minerals; Zoning; Boron isotopes; Greenstone belts; Hydrothermal alterations; Hydrothermal system; Marine evaporites; Mendon Formation; Tourmaline; Volcano-sedimentary sequences; Archean; boron isotope; concentration (composition); evaporite; hydrothermal alteration; igneous geochemistry; isotopic composition; isotopic fractionation; komatiite; oceanic crust; tourmaline; tracer; Boron

Time-lapse characterization of hydrothermal seawater and microbial interactions with basaltic tephra at Surtsey Volcano - Jackson, M.D.; Gudmundsson, M.T.; Bach, W.; Cappelletti, P.; Coleman, N.J.; Ivarsson, M.; J'onasson, K.; Jørgensen, S.L.; Marteinsson, V.; McPhie, J.; Moore, J.G.; Nielson, D.; et al. (Scientific Drilling, 2015)
A new International Continental Drilling Program (ICDP) project will drill through the 50-year-old edifice of Surtsey Volcano, the youngest of the Vestmannaeyjar Islands along the south coast of Iceland, to perform interdisciplinary time-lapse investigations of hydrothermal and microbial interactions with basaltic tephra. The volcano, created in 1963-1967 by submarine and subaerial basaltic eruptions, was first drilled in 1979. In October 2014, a workshop funded by the ICDP convened 24 scientists from 10 countries for 3 and a half days on Heimaey Island to develop scientific objectives, site the drill holes, and organize logistical support. Representatives of the Surtsey Research Society and Environment Agency of Iceland also participated. Scientific themes focus on further determinations of the structure and eruptive processes of the type locality of Surtseyan volcanism, descriptions of changes in fluid geochemistry and microbial colonization of the subterrestrial deposits since drilling 35 years ago, and monitoring the evolution of hydrothermal and biological processes within the tephra deposits far into the future through the installation of a Surtsey subsurface observatory. The tephra deposits provide a geologic analog for developing specialty concretes with pyroclastic rock and evaluating their long-term performance under diverse hydrothermal conditions. Abstracts of research projects are posted at http://surtsey. icdp-online.org. © Author(s) 2015.
cited By 12
Keywords: Biology; Deposits; Drills; Volcanoes; Basaltic eruptions; Environment Agency; Hydrothermal conditions; Logistical support; Long term performance; Microbial colonization; Microbial interactions; Scientific objectives; Basalt

Thermomagnetic measurements of ICDP Core 5045-1, Lake Ohrid - Just, Janna; Nowaczyk, Norbert R; Francke, Alexander; Sagnotti, Leonardo; Wagner, Bernd (PANGAEA, 2015)

Thermal and trace-element anomalies in the eastern snake river plain aquifer: Toward a conceptual model of the EGS resource - Welhan, J.A. (Transactions - Geothermal Resources Council, 2015)
Data on temperature and chemistry of thermally-influenced ground water in the eastern Snake River Plain aquifer were examined to determine how such information could be used to inform on heat transport from the hot rhyolitic rocks that underlie the aquifer. The U.S. Geological Survey's NWIS database reveals the existence of several thermally-influenced areas located near the margins of the aquifer, where ground water temperatures are associated with distinctive water chemistry. The associated enrichments in F, Li and B in these waters are diagnostic of water-rock chemical reactions with felsic rocks under thermal conditions. The chemistry of thermal waters sampled in a deep borehole drilled into rhyodacite and welded tuff beneath the Idaho National Laboratory (INL) to a depth of 3.2 km bears the geochemical fingerprint of such interaction with hot felsic rock. Based on an analysis of temperature data in a thermal anomaly located in the central ESRP aquifer south of the INL, an estimate of the thermal water flux through the base of the aquifer, derived via a two-component mixing model, is incompatible with core-scale data on hydraulic conductivity (K) of the rhyolite. This suggests that advective heat transport from the rhyolite is not spatially uniform but focused in localized, high-K preferential flow paths within the rhyolite and mineralized basalts that overlie the rhyolite. This interpretation is consistent with data on the fracture-flow characteristics of rhyolitic basement and sheds new light on the spatial distribution of thermally influenced ground water near the margins of the ESRP aquifer in the area of the INL.
cited By 0
Keywords: Aquifers; Fluorine; Geothermal fields; Granite; Groundwater; Groundwater flow; Groundwater resources; Heat transfer; Rocks; Trace elements; Chemical tracers; Conceptual model; ESRP; Rhyolite; Thermal waters; Hydrochemistry

The rheological behaviour of fracture-filling cherts: Example of Barite Valley dikes, Barberton Greenstone Belt, South Africa - Ledevin, M.; Arndt, N.; Davaille, A.; Ledevin, R.; Simionovici, A. (Solid Earth, 2015)
In the Barberton Greenstone Belt, South Africa, a 100-250 m thick complex of carbonaceous chert dikes marks the transition from the Mendon Formation to the Mapepe Formation (3260 Ma). The sub-vertical-to vertical position of the fractures, the abundance of highly shattered zones with poorly rotated angular fragments and common jigsaw fit, radial structures, and multiple injection features point to repetitive hydraulic fracturing that released overpressured fluids trapped within the shallow crust. The chemical and isotopic compositions of the chert favour a model whereby seawater-derived fluids circulated at low temperature (< 100-150 °C) within the shallow crust. From the microscopic structure of the chert, the injected material was a slurry of abundant clay-sized, rounded particles of silica, carbonaceous matter and minor clay minerals, all suspended in a siliceous colloidal solution. The dike geometry and characteristics of the slurry concur on that the chert was viscoelastic, and most probably thixotropic at the time of injection: the penetration of black chert into extremely fine fractures is evidence for low viscosity at the time of injection and the suspension of large country rock fragments in the chert matrix provides evidence of high viscosity soon thereafter. We explain the rheology by the particulate and colloidal structure of the slurry, and by the characteristic of silica suspensions to form cohesive 3-D networks through gelation. Our results provide valuable information about the compositions, physical characteristics and rheological properties of the fluids that circulated through Archean volcano-sedimentary sequences, which is an additional step to understand conditions on the floor of Archean oceans, the habitat of early life.
Keywords: Barberton Greenstone Belt; Complex networks; Fracture; Fracturing fluids; Gelation; Hydraulic fracturing; Hydraulic structures; Levees; Silica; Temperature; Viscosity; Colloidal structures; Isotopic composition; Microscopic structures; Multiple injections; Physical characteristics; Rheological behaviour; Rheological property; Volcano-sedimentary sequences; Archean; chert; dike; fracture; greenstone belt; isotopic composition; rheology; viscosity; Suspensions (fluids)

The R'eunion Subchron vegetation and climate history of the northeastern Russian Arctic inferred from the Lake El'gygytgyn pollen record - Zhao, W.W.; Andreev, A.A.; Wennrich, V.; Tarasov, P.E.; Anderson, P.; Lozhkin, A.V.; Melles, M. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2015)
The 318-m-thick sediment record from Lake El'gygytgyn provides unique opportunities for a detailed examination of environmental changes during the R'eunion Subchron polarity reversal event (2.1384-2.1216. Myr. BP) in the northeastern Russian Arctic. The paper describes vegetation and climate fluctuations between . 2.15 and 2.10. Myr. BP as inferred from palynological data. Biome reconstructions indicate that throughout this interval the tundra (TUND) biome generally has higher affinity scores as compared to cold steppe (STEP) or cold deciduous forest (CLDE). An exception is the climatic optimum between . 2.139 and 2.131. Myr. BP, coinciding with Marine Isotope Stage 81 (approximately the R'eunion Subchron), when the CLDE biome has the highest scores. Landscape-openness indices suggest that more closed vegetation characterized most of the interval between 2.146 and 2.127. Myr. BP, when deciduous forest and shrubs expanded in the regional vegetation and climate was relatively warm and wet. Peaks in green algal colonies (Botryococcus) and Zygnema-type spores . 2.150-2.146, . 2.131-2.123, and . 2.112-2.102. Myr. BP indicate expansions of shallow-water habitats and lowered lake levels. Comparisons with biome reconstructions from other interglacial intervals at Lake El'gygytgyn suggest that precession-related summer insolation intensity and obliquity-related duration of summer daylight are major controls on the onset of interglaciations, whereas obliquity probably plays a more significant role on vegetation succession at northern high latitudes during the Pleistocene. © 2015 Elsevier B.V.
cited By 11
Keywords: biome; climate variation; environmental change; interglacial; lake ecosystem; paleoclimate; paleoecology; paleoenvironment; palynology; Pleistocene; regional pattern; succession; vegetation history; deciduous forest; green alga; marine isotope stage; orbital forcing; precession; reconstruction; steppe; Chukchi; Elgygytgyn Lake; Mascarene Islands; Reunion; Russian Federation; Arctic

The palynological record from Coniacian to lower Campanian continental sequences in the Songliao Basin, northeastern China and its implications for palaeoclimate - Ji, L.; Zhang, M.; Song, Z. (Cretaceous Research, 2015)
A palynological record recovered from successions of Coniacian to early Campanian age (89.1-83.5Ma) was obtained from the lacustrine sequences of the SK-I south core (SK-Is) in the Songliao Basin, northeastern China. The palynoflora is dominated by bisaccate gymnosperm pollen, followed by spores of pteridophytes, and just minor amounts of angiosperm pollen. Based on the relative abundance of the different spore and pollen taxa through the core, the succession was subdivided into three palynological assemblages. The results indicate two opposite trends for climate change, a minor warming trend (from 89.1 to 85.7Ma) followed by a rapid cooling trend (85.7-83.5Ma). The first warming trend reached its maximum at 85.7Ma, which is inconsistent with results from the marine realm (which instead show a minor cooling trend based on several proxy records). However, the second cooling phase is consistent with global changes from various and abundant palaeoclimate proxies from marine deposits. We interpret the climatic changes within the studied interval (89.1-83.5Ma) as a consequence of the shifting climate from a hot/super greenhouse to a temperate greenhouse. © 2015 Elsevier Ltd.
cited By 12
Keywords: Campanian; climate variation; Coniacian; flora; geological record; paleoclimate; palynology; proxy climate record; sequence stratigraphy; temperate environment; China; Songliao Basin; Gymnospermae; Magnoliophyta; Pteridophyta

The derivation of an anisotropic velocity model from a combined surface and borehole seismic survey at the COSC-1 borehole, central Sweden - Simon, Helge; Krau{s, Felix; Hedin, Peter; Giese, R{udiger; Juhlin, Christopher (American Geophysical Union, 2015)
The project COSC (Collisional Orogeny in the Scandinavian Caledonides) focuses on the mid Paleozoic Caledonide Orogen in Scandinavia in order to better understand orogenic processes, from the past and in recent active mountain belts. The Scandinavian Caledonides provide a well preserved example of a Paleozoic continent-continent collision, where the surface geology in combination with geophysical data provide control of the geometry of the Caledonian structure. In 2014 the COSC-1 borehole was successfully drilled through the Seve Nappe Complex (SNC) to ~ 2.5 km depth near the town of Åre (central Sweden). Subsequently a major seismic survey was conducted in and around the COSC-1 borehole which comprised both seismic reflection and transmission experiments. This will allow extrapolation of results from core analysis and downhole logging to the structures around the borehole. The survey consisted of three simultaneous experiments: 1) a high-resolution zero-offset Vertical Seismic Profile (VSP), 2) a multi-azimuthal walkaway VSP in combination with three long offset surface receiver lines, and 3) a limited 3D seismic survey. In this study data from the multi-azimuthal walkaway VSP experiment and the long offset surface lines were used to derive a detailed velocity model around the borehole from the inversion of first arrival traveltimes. The P-wave velocity profile at the borehole obtained by this tomography approach correlates in general with sonic velocities measured during borehole logging and with interval velocities calculated from the zero-offset VSP data, however the absolute values are always significantly higher. This is probably due to the presence of significant seismic anisotropy in the SNC which has also been observed in ultrasonic lab measurements. The obtained anisotropic velocity model serves as the basis for the ongoing application of imaging approaches like pre-stack depth migration techniques.
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Seismic tomography reveals a mid-crustal intrusive body, fluid pathways and their relation to the earthquake swarms in West Bohemia/Vogtland - Mousavi, Sima; Bauer, Klaus; Korn, Michael; Hejrani, Babak (Geophysical Journal International, 2015)
The region of West Bohemia/Vogtland in the Czech-German border area is well known for the repeated occurrence of earthquake swarms, CO2 emanations and mofette fields. We present a local earthquake tomography study undertaken to image the Vp and Vp/Vs structure in the broader area of earthquake swarm activity. In comparison with previous investigations, more details of the near-surface geology, potential fluid pathways and features around and below the swarm focal zone could be revealed. In the uppermost crust, for the first time the Cheb basin and the Bubl'ak/Hartoušov mofette fields were imaged as distinct anomalies of Vp and Vp/Vs. The well-pronounced low-Vp anomaly of the Cheb basin is not continuing into the Eger rift indicating a particular role of the basin within the rift system. A steep channel of increased Vp/Vs is interpreted as the pathway for fluids ascending from the earthquake swarm focal zone up to the Bubl'ak/Hartoušov mofette fields. As a new feature, a mid-crustal body of high Vp and increased Vp/Vs is revealed just below and north of the earthquake swarm focal zone. It may represent a solidified intrusive body which emplaced prior or during the formation of the rift system. We speculate that enhanced fluid flow into the focal zone and triggering of earthquakes could be driven by the presence of the intrusive body if cooling is not fully completed. We consider the assumed intrusive structure as a heterogeneity leading to higher stress particularly at the junction of the rift system with the basin and prominent fault structures. This may additionally contribute to the triggering of earthquakes. © The Authors 2015.
Keywords: Germany; Vogtland; Flow of fluids; Seismographs; Body waves; Earthquake swarms; Europe; Fault structure; Fluid pathways; Near-surface geology; Seismic tomography; Seismicity and tectonics; body wave; earthquake swarm; seismic tomography; seismic velocity; seismicity; tectonics; Earthquakes

The Cretaceous Songliao Basin: Dynamic background from volcanic rift to interior sag basin. - Wang, P.; Zhao, R.; Meng, Q.; Qu, X.; Zhu, D.; Gao, Y. (Earth Science Frontiers, 2015)
On the basis of the new results of the CCSD (China Cretaceous Continental Scientific Drilling) and the integrated information concerning tectonic basin classification and 3-D description of the Songliao Basin (SB), we reevaluate the type, tectonic evolution, and geodynamics of the SB according to systematical analysis of tectonic setting and basin fillings. The SB is on the northeast marginal zone of Mongolia-North China Plate. It is united with the Siberian Plate by the Mongolia-Okhotsk suture belt to the north, and connected with the Pacific Plate by Sikhote-Alin accretionary belt to the east. The vertical filling successions of the SB can be subdivided into three tectono-stratigraphic units by two regional unconformities which are on the top boundaries of the Yingcheng (K1y) (ca. 110 Ma) and Nenjiang (K2n) (ca. 79.1 Ma) Formations, respectively. The three tectono-stratigraphic units are block faulting (Huoshiling to Yingcheng Formations), interior sag (Denglouku to Nenjiang Formations), and structural inversion (Sifangtai to Yi'an Formations) sequences. The block faulting sequence is a kind of volcanic rift basin, and the latter two all belong to the type of interior sag basin. In the block faulting period (150-110 Ma), syn-rift volcanogenic successions were formed under the impact of regional extension that may be caused by the Plate reorganization from two sides, the northern and eastern active continental margins. The post-rift basin fills (110-79.1 Ma) may result from the superimposed subsidence of both post volcanic thermal declining and regional strike-slip pull-apart effect. Widespread and thick source rocks deposited because of the high rate and under-compensation of sedimentation in this period. In the structural inversion period (79.1-40 Ma), depocenter of the SB migrated northwestward, and the basin was shrinking to demise. This was a result of the regional compression that should be caused by the Pacific Plate subduction under the eastern margin of the Eurasian Plate in the Mid-Cretaceous to the Middle Eocene. ©, 2015, The Editorial Office of Earth Science Frontiers. All right reserved.
cited By 37
Keywords: Classification (of information); Faulting; Geodynamics; Stratigraphy; Volcanoes; Continental scientific drillings; Integrated informations; North China; Songliao basin; Stratigraphic units; Systematical analysis; Tectonic evolution; Volcanic rifts; Plates (structural components)

The China continental scientific drilling project: CCSD-1 well drilling engineering and construction - Wang, Da; Zhang, Wei; Zhang, Xiaoxi; Zhao, Guolong; Zuo, Ruqiang; Ni, Jialu; Yang, Gansheng; Jia, Jun; Yang, Kaihua; Zhu, Yongyi; et al. (Springer Geology, 2015)
cited By 0

The carbon isotopic composition of individual biomarkers in lacustrine source rocks from Songliao Basin and its biogeochemical implication - Li, WANG; Xinxing, CAO; Yan, LI; et al. (Geochimica, 2015)

The Blacktail Creek Tuff: an analytical and experimental study of rhyolites from the Heise volcanic field, Yellowstone hotspot system - Bolte, T.; Holtz, F.; Almeev, R.; Nash, B. (Contributions to Mineralogy and Petrology, 2015)
The magma storage conditions of the 6.62 Ma Blacktail Creek Tuff eruption, belonging to the Heise volcanic field (6.62 –4.45 Ma old) of the Yellowstone hotspot system, have been investigated by combining thermobarometric and experimental approaches. The results from different geothermometers (e.g., Fe –Ti oxides, feldspar pairs, apatite and zircon solubility, and Ti in quartz) indicate a pre-eruptive temperature in the range 825 –875 °C. The temperature estimated using two-pyroxene pairs varies in a range of 810 –950 °C, but the pyroxenes are probably not in equilibrium with each other, and the analytical results of melt inclusion in pyroxenes indicate a complex history for clinopyroxene, which hosts two compositionally different inclusion types. One natural Blacktail Creek Tuff rock sample has been used to determine experimentally the equilibrium phase assemblages in the pressure range 100 –500 MPa and a water activity range 0.1 –1.0. The experiments have been performed at fluid-present conditions, with a fluid phase composed of H2O and CO2, as well as at fluid-absent conditions. The stability of the quartzo-feldspathic phases is similar in both types of experiments, but the presence of mafic minerals such as biotite and clinopyroxene is strongly dependent on the experimental approach. Possible explanations are given for this discrepancy which may have strong impacts on the choice of appropriate experimental approaches for the determination of magma storage conditions. The comparison of the composition of natural phases and of experimentally synthesized phases confirms magma storage temperatures of 845 –875 °C. Melt water contents of 1.5 –2.5 wt% H2O are required to reproduce the natural Blacktail Creek Tuff mineral assemblage at these temperatures. Using the Ti-in-quartz barometer and the Qz –Ab –Or proportions of natural matrix glasses, coexisting with quartz, plagioclase and sanidine, the depth of magma storage is estimated to be in a pressure range between 130 and 250 MPa. © 2015, Springer-Verlag Berlin Heidelberg.
cited By 28
Keywords: clinopyroxene; hot spot; melt inclusion; meltwater; plagioclase; quartz; rhyolite; sanidine; temperature; Idaho; Snake River Plain; United States; Yellowstone Volcanic Plateau; Gymnocephalus cernuus

Tephrostratigraphy and depositional environment of young (<2.94 Ma) Hadar Formation deposits at Ledi-Geraru, Afar, Ethiopia - DiMaggio, Erin N.; Arrowsmith, J Ram'on; Campisano, Christopher J.; Johnson, Roy; Deino, Alan L.; Warren, Mark; Fisseha, Shimeles; Cohen, Andrew S. (Journal of African Earth Sciences, 2015)
The Pliocene Hadar Formation, exposed throughout the lower Awash Valley, Ethiopia, chronicles the evolution and paleoenvironmental context of early hominins. Deposition of the Hadar Formation continued until at least 2.94 Ma, but what transpired in the Hadar Basin after this time remains poorly documented due to an erosional event that truncated the formation throughout much of the valley. Here we present geologic mapping and stratigraphic analysis of a 26 m-thick section of sedimentary rocks and tephras exposed in the Ledi-Geraru project area in the region of Gulfaytu. The section contains Hadar Formation strata younger than 2.94 Ma, and sediments that we interpret are Busidima Formation in age, <2.7 Ma. We use this record to place additional constraints on depositional environments and the tectonic and paleogeomorphic history of the region. The lower 20 m of section contains lacustrine deposits that conformably overly a 2.94 Ma marker bed (BKT-2U) that previously served as the uppermost dated tephra in the Hadar Formation. We identified seven post-BKT-2U tephras; three were analyzed for glass chemistry, and one yielded an 40Ar/39Ar age of 2.931 ± 0.017 Ma (1σ). Based on these analyses, the newly mapped deposits at Gulfaytu extend the top of the Hadar Formation, representing ca. 20 kyr of post-BKT-2 sedimentation. The Hadar Basin remained depositional following the BKT-2 eruptions, and paleolake Hadar was present at Gulfaytu at this time. An erosional surface marked by a conglomerate truncates the Hadar strata suggesting that the Gulfaytu region was also was influenced by significant changes to basin architecture well-documented elsewhere in the lower Awash Valley. In addition, geophysical models suggest that central Ledi Geraru hosts a thick subsurface lacustrine sedimentary record within the Hadar Basin. The results of this paper provide the outcrop and near surface characterization for the Hominin Sites and Paleolakes Drilling Project (HSPDP) effort at Gulfaytu. © 2015 Elsevier Ltd.
Keywords: Afar; depositional environment; geological mapping; hominid; lithostratigraphy; paleoenvironment; Pliocene; tephra; tephrochronology

Tectonic stress and renewed uplift at Campi Flegrei caldera, southern Italy: New insights from caldera drilling - Carlino, Stefano; Kilburn, Christopher R.J.; Tramelli, Anna; Troise, Claudia; Somma, Renato; De Natale, Giuseppe (Earth and Planetary Science Letters, 2015)
Keywords: Campania [Italy]; Campi Flegrei; Italy; Napoli [Campania]; Drilling; Risk assessment; Stresses; Borehole measurements; Caldera unrest; Campi Flegrei; Extensional stress; Improved forecast; Leak-off tests; Principal stress; Volcanic eruptions; caldera; deep drilling; geoaccumulation; stress field; structural geology; tectonic evolution; tectonic setting; uplift; volcanic eruption; volcanology; Volcanoes

Surirella prespanensis sp. nov. and Surirella hinziae sp. nov., two new diatom (bacillariophyceae) species from ancient lake prespa (macedonia/albania/greece) - Cvetkoska, Aleksandra; Hamilton, Paul B.; Levkov, Zlatko (Fottea, 2015)
Surirella is a polyphyletic and highly diverse diatom genus with more than 500 species described worldwide. Within a study of its diversity and distribution in the Republic of Macedonia, ancient Lake Prespa has been investigated, as “sister” to Lake Ohrid and part of a unique lake system with extraordinary age, biodiversity and number of endemic species. During the study, two new Surirella species have been identified and their LM and SEM based formal descriptions and differential diagnoses are provided herein. Surirella prespanensis sp. nov. has been observed in the contemporary and the fossil diatom flora of the lake. It can be distinguished from other similar taxa by its valve outline, size, shape of the median ridge and the presence of silica grooves along the raphe. Surirella hinziae sp. nov. is known only from the fossil diatom flora of Lake Prespa and can be recognized by its valve outline, size, shape of the median ridge and the presence of helictoglossa-like processes. © Czech Phycological Society (2015).

Strontium and oxygen isotopic profiles through 3km of hydrothermally altered oceanic crust in the Reykjanes Geothermal System, Iceland - Marks, N.; Zierenberg, R.A.; Schiffman, P. (Chemical Geology, 2015)
The Iceland Deep Drilling Program well RN-17 was drilled 3km into a section of hydrothermally altered basaltic crust in the Reykjanes geothermal system in Iceland. The system is located on the landward extension of the Mid-Atlantic Ridge, and the circulating hydrothermal fluid is modified seawater, making Reykjanes a useful analog for mid-oceanic ridge hydrothermal systems. We have determined whole-rock Sr and O isotope compositions, and Sr isotope compositions of epidote grains from the RN-17 cuttings and RN-17B core. Whole rock oxygen isotope ratios range from -0.13 to 3.61‰ V-SMOW, and are isotopically lighter than fresh MORB (5.8±0.2‰). The concentrations of Sr in the altered basalt range from well below to well above concentrations in fresh rock, and appear to be strongly correlated with the dominant alteration mineralogy. Whole rock Sr isotope ratios ranged from 0.70329 in the least altered crystalline basalt, to 0.70609 in the most altered hyaloclastite samples; there is no correlation with depth. Sr isotope ratios in epidote grains measured by laser ablation MC-ICP-MS ranged from 0.70360 to 0.70731. Three depth intervals, at 1000m, 1350m, and 1650m depth, have distinctive isotopic signatures, where 87Sr/86Sr ratios are elevated (mean value>0.7050) relative to background levels (mean altered basalt value 0.7042). These areas are proximal to geothermal feed zones, and the 1350m interval directly overlies the transition from dominantly extrusive to dominantly intrusive lithologies. Oxygen isotope measurements yield integrated water/rock ratios of 0.4 to 4.3, and suggest that hydrothermal fluids must have formerly had a component of meteoric water. Strontium isotopic measurements provide a more sensitive indication of seawater interaction and require significant exchange with seawater strontium. Both isotopic systems indicate that the greenschist-altered basalts were in equilibrium with hydrothermal fluids at a relatively high mean water/rock (Wt.) ratio ranging from about 0.5 to 4. These ratios are higher than estimates from ODP Hole 504B and IODP Hole 1256D, but are consistent with values inferred from vent fluids from 21° and 13°N on the East Pacific Rise (Albarède et al., 1981; Michard et al., 1984; Alt et al., 1996; Harris et al., 2015). © 2015 Elsevier B.V.
cited By 18
Keywords: Aluminum; Basalt; Crystalline rocks; Geothermal fields; Isotopes; Laser ablation; Minerals; Oxygen; Rocks; Seawater; Silicate minerals; Alteration; Geothermal; Hydrothermal; Icelands; Oxygen isotopes; Reykjanes; Strontium isotopes; Strontium; concentration (composition); geothermal system; hydrothermal alteration; hydrothermal fluid; hydrothermal vent; isotopic composition; mid-ocean ridge basalt; oceanic crust; oxygen isotope; strontium isotope; East Pacific Rise; Iceland; Pacific Ocean; Reykjanes Peninsula

Spatial uniformity in the mineralogical and geochemical compositions of surface sediments in Lake Qinghai and their controlling factors - Chen, Liu-Mei; Jin, Zhangdong; Wan, Dejun; Zhang, Fei (Limnology, 2015)
To advance the understanding of the spatial variability of sediment composition and its controlling factors in a large hydrologically closed lake, the spatial distributions in the mineralogy and geochemistry of 18 surface sediment samples along three transects across the deepest part of Lake Qinghai on the northeastern Tibetan Plateau were investigated. The data show (1) that the surface lake sediments are almost the same in the XRD patterns, (2) that the sediments do not have considerable changes in geochemical compositions along three transects and (3) that the standard deviations of the lake sediments are low in grain size, elemental abundances, δ13C and δ18O values of carbonates, and total organic carbon and nitrogen, with the exception of one sample (QH-11) from the westernmost part of the northern sub-basin. These characteristics indicate that the spatial variability of the surface sediment across Lake Qinghai is very low in geochemical and silicate mineralogical compositions, with limited differences in the chemical composition of carbonates associated with river water dilution. Sample QH-11 has anomalously high levels of MgO, a high carbonate content, and positive δ13C and δ18O values in bulk and fine-grained carbonates, probably because of the effect of calcareous tufa. Spatial uniformity in the mineralogical and geochemical compositions of surface sediments in Lake Qinghai can be attributed to the flat topography of the lakebed and stable sediment provenances, the latter dominated by dust deposition and authigenic carbonates. The spatial uniformity and dominance of dust and authigenic aragonite of surface sediments across Lake Qinghai provide a potential record of the hydroclimate in the past, which is associated with changes in the Westerlies and the summer monsoons. © 2015, The Japanese Society of Limnology.

Some observations facing the interpretation of Waqf as Suwwan structure, SE desert of Jordan, as an impact crater - Abed, A.M.; Amireh, B.S.; Al Zghoul, K. (Arabian Journal of Geosciences, 2015)
Twenty-seven samples from Waqf as Suwwan structure in the southeastern desert of Jordan were analyzed for their petrography, mineralogy, and geochemistry. All three types of analysis failed to show any evidence supporting the structure as an impact crater, but they cannot be used as an evidence discrediting the structure as an impact crater. This is because of the presence of shatter cones and rare shock metamorphic features. Shatter cones are well established in the Waqf as Suwwan structures and are accepted internationally as a criterion for impact craters. Shock metamorphic features reported in previous works are extremely rare and atypical. Planar features (PFs) were reported in one single quartz grain taken from a 30-m-thick Kurnub sandstone horizon. They are also reported from one single loose chert nodule, despite the extremely abundant bedded and loose chert within the structure. The PFs in the chert nodule are questioned because they are possibly due to diagenesis. More important is the complete absence of any type of breccias, lithic, melt, or suevitic and ejecta within and around the structure. The deep erosion of the crater used by advocates cannot stand for rigorous discussion on the amount of erosion in the desert environment in southeastern Jordan. Given the exact age of the cratering event is not yet known, and an approximate long-term rate of erosion of 1 m/Ma breccias and ejecta should be present in and/or around the structure. © 2014, Saudi Society for Geosciences.
cited By 3

Snake river plain play fairway analysis - Phase 1 report - Shervais, J.W.; Glen, J.M.; Liberty, L.M.; Dobson, P.; Gasperikova, E.; Sonnenthal, E.; Visser, C.; Nielson, D.; Garg, S.; Evans, J.P.; Siler, D.; Deangelo, J.; et al. (Transactions - Geothermal Resources Council, 2015)
The Snake River volcanic province (SRP) overlies a thermal anomaly that extends deep into the mantle; it represents one of the highest heat flow provinces in North America. Our goals for this Phase 1 study are to: (1) adapt the methodology of Play Fairway Analysis for geothermal exploration to create a formal basis for its application to geothermal systems, (2) assemble relevant data for the SRP from publicly available and private sources, and (3) build a geothermal play fairway model for the SRP and identify the most promising plays, using software tools that are standard in the petroleum industry. The success of play fairway analysis in geothermal exploration depends critically on defining a systematic methodology that is grounded in theory (as developed within the petroleum industry over the last two decades) and within the geologic and hydrologic framework of real geothermal systems. Our preliminary assessment of the data suggests that important undiscovered geothermal resources may be located in several areas of the SRP, including the western SRP (associated with buried lineaments defined by gravity or magnetic anomalies, and capped by extensive deposits of lacustrine sediment), at lineament intersections in the central SRP (along the Banbury-Hagerman trend N W of Twin Falls, and along the northern margin of the Mt Bennett Hills-Camas Prairie area), and along the margins of the eastern SRP. Additional high temperature resources are likely associated with rhyolite domes and crypto-domes in the eastern SRP, but are masked by shallow groundwater flow leading to low upper crustal heat flow values. These blind resources may be exploitable with existing deep drilling technology. Groundwater modeling planned for later phases of the PFA project will address whether temperatures at viable producing depths are sufficient to support electricity production. © Copyright (2015) by Geothermal Resources Council All rights reserved.
cited By 3
Keywords: Application programs; Domes; Geothermal fields; Geothermal wells; Groundwater; Groundwater flow; Groundwater resources; Heat transfer; Petroleum industry; Petroleum prospecting; Rivers; Structural geology; Electricity production; Geothermal exploration; Groundwater modeling; Idaho; Play fairway analysis; Preliminary assessment; Snake river plains; Systematic methodology; Geothermal prospecting

Snake river plain - Malde, H.E. (The Quaternary of the U.S., 2015)
The vast lowland, known as the Snake River Plain, that stretches across southern Idaho is a Pliocene structural trough filled with a complex sequence of basaltic lava and intercalated detrital deposits more than a kilometer in thickness, much of which is of Quaternary age. The trough at the western end is outlined by a northwest-trending graben 50 km broad, the site of a basin fill of lake and stream deposits rich in molluscan and vertebrate fossils. The eastern plain, on the other hand, a monotonous tract of lava diversified only by numerous subdued volcanic vents, is structurally more like a downwarp. Canyon cutting in the western basin to a depth of 150-300 m gives excellent exposures of the Quaternary deposits and their physiographic relations. A widespread unit of Blancan provincial age at least 600 m thick, characterized by moderately faulted fine-grained sedimentary facies indicative of adjoining environments of lakes, river channels, and swampy flood plains, is beveled by undeformed lower Pleistocene sand and gravel 180-250 m above the present Snake River. A subsequent canyon 250 m deep was filled in middle Pleistocene time by lava flows and by sediments trapped in lakes behind lava dams. These deposits were then beveled by pediment gravel 170 m above the river. Entrenchment of the present Snake River canyon, regarded as a late Pleistocene event, coincided with eruption of the surface lava flows in the eastern plain, which apparently forced the Snake River into its course along the southern margin. Two gravel terraces 120 m and 60 m above the river, which were built between lava eruptions as cutting progressed, include abundant constituents from glaciated mountains in central Idaho and possibly represent glacial outwash. Still younger gravel on the canyon floor, distinguished by enormous boulders heaped in huge bars as much as 90 m high, is attributed to catastrophic overflow of Lake Bonneville about 30,000 years ago. © 1965, by Princeton University Press. All Rights Reserved.
cited By 9

Shear behavior of DFDP-1 borehole samples from the Alpine Fault, New Zealand, under a wide range of experimental conditions - Ikari, M.J.; Tr{utner, S.; Carpenter, B.M.; Kopf, A.J. (International Journal of Earth Sciences, 2015)
The Alpine Fault is a major plate-boundary fault zone that poses a major seismic hazard in southern New Zealand. The initial stage of the Deep Fault Drilling Project has provided sample material from the major lithological constituents of the Alpine Fault from two pilot boreholes. We use laboratory shearing experiments to show that the friction coefficient µ of fault-related rocks and their precursors varies between 0.38 and 0.80 depending on the lithology, presence of pore fluid, effective normal stress, and temperature. Under conditions appropriate for several kilometers depth on the Alpine Fault (100 MPa, 160 °C, fluid-saturated), a gouge sample located very near to the principal slip zone exhibits µ = 0.67, which is high compared with other major fault zones targeted by scientific drilling, and suggests the capacity for large shear stresses at depth. A consistent observation is that every major lithological unit tested exhibits positive and negative values of friction velocity dependence. Critical nucleation patch lengths estimated using representative values of the friction velocity-dependent parameter a−b and the critical slip distance Dc, combined with previously documented elastic properties of the wall rock, may be as low as 3 m. This small value, consistent with a seismic moment Mo = 4 × 1010 for an Mw = 1 earthquake, suggests that events of this size or larger are expected to occur as ordinary earthquakes and that slow or transient slip events are unlikely in the approximate depth range of 3 –7 km. © 2015, The Author(s).
cited By 13
Keywords: borehole; drilling; fault zone; friction; seismic hazard; seismic moment; shear stress; slip rate; Alpine Fault Zone; New Zealand; South Island

Microbial abundance in lacustrine sediments: a case study from Lake Van, Turkey - Kallmeyer, J.; Grewe, S.; Glombitza, C.; Kitte, J.A. (International Journal of Earth Sciences, 2015)
The ICDP “PaleoVan” drilling campaign at Lake Van, Turkey, provided a long (>100 m) record of lacustrine subsurface sedimentary microbial cell abundance. After the ICDP campaign at Potrok Aike, Argentina, this is only the second time deep lacustrine cell counts have been documented. Two sites were cored and revealed a strikingly similar cell distribution despite differences in organic matter content and microbial activity. Although shifted towards higher values, cell counts from Lake Potrok Aike, Argentina, reveal very similar distribution patterns with depth. The lacustrine cell count data are significantly different from published marine records; the most probable cause is differences in sedimentary organic matter composition with marine sediments containing a higher fraction of labile organic matter. Previous studies showed that microbial activity and abundance increase centimetres to metres around geologic interfaces. The finely laminated Lake Van sediment allowed studying this phenomenon on the microscale. We sampled at the scale of individual laminae, and in some depth intervals, we found large differences in microbial abundance between the different laminae. This small-scale heterogeneity is normally overlooked due to much larger sampling intervals that integrate over several centimetres. However, not all laminated intervals exhibit such large differences in microbial abundance, and some non-laminated horizons show large variability on the millimetre scale as well. The reasons for such contrasting observations remain elusive, but indicate that heterogeneity of microbial abundance in subsurface sediments has not been taken into account sufficiently. These findings have implications not just for microbiological studies but for geochemistry as well, as the large differences in microbial abundance clearly show that there are distinct microhabitats that deviate considerably from the surrounding layers. © 2015, The Author(s).
cited By 9
Keywords: biosphere; lacustrine deposit; microbial activity; microbial community; microbial ecology; relative abundance; Lake Van; Turkey

Mediterranean climate since the Middle Pleistocene: A 640 ka stable isotope record from Lake Ohrid (Albania/Macedonia) - Lacey, J.H.; Leng, M.J.; Francke, A.; Sloane, H.J.; Milodowski, A.; Vogel, H.; Baumgarten, H.; Wagner, B. (Biogeosciences Discussions, 2015)
Lake Ohrid (Macedonia/Albania) is an ancient lake with a 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 on carbonate from the upper ca. 248 m of sediment cores recovered as part of the Scientific Collaboration on Past Speciation Conditions in Lake Ohrid (SCOPSCO) project, covering the past 640 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, comprising abundant endogenic calcite through interglacials and being almost absent in glacials, apart from 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 hydroclimate fluctuations on orbital and millennial timescales. We also measured isotopes on authigenic siderite (δ18Os and δ13Cs) and, with the δ18OCc and δ18Os, reconstruct δ18O of lakewater (δ18Olw) through the 640 ka. Overall, glacials have lower δ18Olw when compared to interglacials, most likely due to cooler summer temperatures, a higher proportion of winter precipitation (snowfall), and a reduced inflow from adjacent Lake Prespa. The isotope stratigraphy suggests Lake Ohrid experienced a period of general stability through Marine Isotope Stage (MIS) 15 to MIS 13, highlighting MIS 14 as a particularly warm glacial, and was isotopically freshest during MIS 9. After MIS 9, the variability between glacial and interglacial δ18Olw is enhanced and the lake became increasingly evaporated through to present day with MIS 5 having the highest average δ18Olw. 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 the lake. © Author(s) 2015.
Keywords: Lake Mikri Prespa; Lake Ohrid; Mediterranean Region; biodiversity; calcite; carbon isotope; endemic species; glacial-interglacial cycle; lacustrine deposit; lake water; Mediterranean environment; oxygen isotope; Pleistocene; population structure; sediment core; siderite; stable isotope; temperature effect

Magma mixing enhanced by bubble segregation - Wiesmaier, S.; Morgavi, D.; Renggli, C.J.; Perugini, D.; De Campos, C.P.; Hess, K.-U.; Ertel-Ingrisch, W.; Lavall'ee, Y.; Dingwell, D.B. (Solid Earth, 2015)
In order to explore the materials' complexity induced by bubbles rising through mixing magmas, bubble-advection experiments have been performed, employing natural silicate melts at magmatic temperatures. A cylinder of basaltic glass was placed below a cylinder of rhyolitic glass. Upon melting, bubbles formed from interstitial air. During the course of the experimental runs, those bubbles rose via buoyancy forces into the rhyolitic melt, thereby entraining tails of basaltic liquid. In the experimental run products, these plume-like filaments of advected basalt within rhyolite were clearly visible and were characterised by microCT and high-resolution EMP analyses. The entrained filaments of mafic material have been hybridised. Their post-experimental compositions range from the originally basaltic composition through andesitic to rhyolitic composition. Rheological modelling of the compositions of these hybridised filaments yield viscosities up to 2 orders of magnitude lower than that of the host rhyolitic liquid. Importantly, such lowered viscosities inside the filaments implies that rising bubbles can ascend more efficiently through pre-existing filaments that have been generated by earlier ascending bubbles. MicroCT imaging of the run products provides textural confirmation of the phenomenon of bubbles trailing one another through filaments. This phenomenon enhances the relevance of bubble advection in magma mixing scenarios, implying as it does so, an acceleration of bubble ascent due to the decreased viscous resistance facing bubbles inside filaments and yielding enhanced mass flux of mafic melt into felsic melt via entrainment. In magma mixing events involving melts of high volatile content, bubbles may be an essential catalyst for magma mixing. Moreover, the reduced viscosity contrast within filaments implies repeated replenishment of filaments with fresh end-member melt. As a result, complex compositional gradients and therefore diffusion systematics can be expected at the filament-host melt interface, due to the repetitive nature of the process. However, previously magmatic filaments were tacitly assumed to be of single-pulse origin. Consequently, the potential for multi-pulse filaments has to be considered in outcrop analyses. As compositional profiles alone may remain ambiguous for constraining the origin of filaments, and as 3-D visual evidence demonstrates that filaments may have experienced multiple bubbles passages even when featuring standard diffusion gradients, therefore, the calculation of diffusive timescales may be inadequate for constraining timescales in cases where bubbles have played an essential role in magma mixing. Data analysis employing concentration variance relaxation in natural samples can distinguish conventional single-pulse filaments from advection via multiple bubble ascent advection in natural samples, raising the prospect of yet another powerful application of this novel petrological tool. © 2015 Author(s).
cited By 15
Keywords: Advection; Basalt; Cylinders (shapes); Glass; Mixing; Silicates; Viscosity; Compositional gradients; Diffusion gradients; Magmatic temperatures; Orders of magnitude; Reduced viscosity; Rheological modelling; Viscous resistance; Volatile contents; Computerized tomography; advection; bubble; chemical alteration; chemical composition; entrainment; experimental study; igneous geochemistry; magma assimilation; mixing; rhyolite; silicate melt

Constant diversification rates of endemic gastropods in ancient Lake Ohrid: Ecosystem resilience likely buffers environmental fluctuations - F{oller, K.; Stelbrink, B.; Hauffe, T.; Albrecht, C.; Wilke, T. (Biogeosciences, 2015)
Ancient lakes represent key ecosystems for endemic freshwater species. This high endemic biodiversity has been shown to be mainly the result of intra-lacustrine diversification. Whereas the principle role of this mode of diversification is generally acknowledged, actual diversification rates in ancient lakes remain little understood. At least four types are conceivable. Diversification rates may be constant over time, they may fluctuate, rates may be higher in the initial phase of diversification, or there may be a pronounced lag phase between colonization and subsequent diversification. As understanding the tempo of diversification in ancient lake environments may help reveal the underlying processes that drive speciation and extinction, we here use the Balkan Lake Ohrid as a model system and the largest species flock in the lake, the non-pyrgulinid Hydrobiidae, as a model taxon to study changes in diversification rates over time together with the respective drivers. Based on phylogenetic, molecular-clock, lineage-through-time plot, and diversification-rate analyses we found that this potentially monophyletic group is comparatively old and that it most likely evolved with a constant diversification rate. Preliminary data of the SCOPSCO (Scientific Collaboration On Past Speciation Conditions in Lake Ohrid) deep-drilling program do indicate signatures of severe environmental/climatic perturbations in Lake Ohrid. However, so far there is no evidence for the occurrence of catastrophic environmental events. We therefore propose that the constant diversification rate observed in endemic gastropods has been caused by two factors: (i) a potential lack of catastrophic environmental events in Lake Ohrid and/or (ii) a probably high ecosystem resilience, buffering environmental changes. Parameters potentially contributing to the lake's high ecosystem resilience are its distinct bathymetry, ongoing tectonic activities, and karst hydrology. The current study not only contributes to one of the overall goals of the SCOPSCO deep-drilling program - inferring the driving forces for biotic evolution in Lake Ohrid. It might also enhance our understanding of how ecosystem resilience, in general, may promote relatively constant diversification rates in isolated ecosystems. However, we encourage future studies testing hypotheses about the lack of catastrophic events in Lake Ohrid. These studies should be based on high-resolution data for the entire geological history of the lake, and they should potentially involve information from the sediment fossil record, not only for gastropods but also for other groups with a high share of endemic taxa. © 2015 Author(s).
Keywords: Lake Ohrid; Gastropoda; Hydrobiidae; biodiversity; catastrophic event; ecosystem resilience; endemic species; evolution; gastropod; lake ecosystem; phylogeny

Drilling fluid technique for special drilling technology in SK-2 Well - Wenlong, ZHENG; Xiaoming, Wu; Yongyi, ZHU; Wenshi, Wang; Linsheng, ZHANG; Jie, Xu (石油钻采工艺, 2015)

Downhole geophysical observatories: best installation practices and a case history from Turkey - Prevedel, B.; Bulut, F.; Bohnhoff, M.; Raub, C.; Kartal, R.F.; Alver, F.; Malin, P.E. (International Journal of Earth Sciences, 2015)
Downhole sensors of different types and in various environments provide substantial benefit to signal quality. They also add the depth dimension to measurements performed at the Earths’ surface. Sensor types that particularly benefit from downhole installation due to the absence of near-surface noise include piezometers, seismometers, strainmeters, thermometers, and tiltmeters. Likewise, geochemical and environmental measurements in a borehole help eliminate near-surface weathering and cultural effects. Installations from a few hundred meter deep to a few kilometer deep dramatically reduce surface noise levels–the latter noticeably also reduces the hypocentral distance for shallow microearthquakes. The laying out of a borehole network is always a compromise of local boundary conditions and the involved drilling costs. The installation depth and procedure for a long-term downhole observatory can range from time limited installations, with a retrieval option, to permanently cemented sensors. Permanently cemented sensors have proven to be long-term stable with non-deteriorating coupling and borehole integrity. However, each type needs to be carefully selected and planned according to the research aims. A convenient case study is provided by a new installation of downhole seismometers along the shoreline of the eastern Marmara Sea in Turkey. These stations are being integrated into the regional net for monitoring the North Anatolian Fault Zone. Here we discuss its design, installation, and first results. We conclude that, despite the logistical challenges and installation costs, the superior quality of downhole data puts this technique at the forefront of applied and fundamental research. © 2015, The Author(s).
cited By 12
Keywords: earthquake hypocenter; earthquake mechanism; fault zone; microearthquake; North Anatolian Fault; piezometer; seismic noise; seismograph; Sea of Marmara; Turkey

Dinosaur climate probed - Qiu, J. (Science, 2015)
cited By 0
Keywords: biostratigraphy; climate variation; dinosaur; fossil record; Jurassic; paleoenvironment; skeleton; taphonomy; biota; climate; Cretaceous; dinosaur; geological time; greenhouse effect; Jurassic; lake sediment; Maastrichtian; mass extinction; nonhuman; Paleocene; priority journal; Short Survey; temperature; animal; China; climate; greenhouse effect; lake; sediment; species extinction; temperature; Dinosauria; Animals; China; Climate; Dinosaurs; Extinction; Biological; Geologic Sediments; Global Warming; Greenhouse Effect; Lakes; Temperature

Diatoms as indicators of hydrological and climatic changes in Laguna Potrok Aike (Patagonia) since the Late Pleistocene - Recasens, Cristina; Ariztegui, Daniel; Maidana, Nora I.; Zolitschka, Bernd (Palaeogeography, Palaeoclimatology, Palaeoecology, 2015)
Southern South America is a key site to study climate variability in the Southern Hemisphere, allowing for a wide variety of climatic archives. Recently, several investigations using lacustrine sediments have provided an enormous amount of information to reconstruct past environmental changes. In the framework of the Potrok Aike Maar Lake Sediment Archive Drilling Project (PASADO) more than 500. m of sediment cores were retrieved from the center of this lake.This contribution is centered in the diatom record of a core covering over the last 50. cal. ka BP. Nine statistically significant zones were determined based on changes in the assemblages of more than 200 species of diatoms, showing changes in productivity throughout time. Although it appears that the presence of mass waste events may have triggered some peaks in productivity, large fluctuations in diatom abundance and changes in species assemblages coincide with distinctive Antarctic warm events, A2 and A1, described for Antarctic ice cores at around 44.5 and 38.5 kyr BP respectively (Blunier and Brook, 2001). Furthermore, a smaller diatom peak may account for the A3 event compatible with a new OSL-based chronological model. Up to now they have only been described for Antarctica, but the fact that these events are recorded in southern Patagonia indicates their magnitude and importance for climate in the Southern Hemisphere. © 2014 Elsevier B.V.
Keywords: Argentina; Laguna Potrok Aike; Patagonia; Santa Cruz [Argentina]; Bacillariophyta; bioindicator; climate variation; diatom; hydrological change; lacustrine deposit; maar; paleoclimate; Pleistocene; Southern Hemisphere

Diagenetic and paleoenvironmental controls on late cretaceous clay minerals in the Songliao basin, Northeast China - Gao, Y.; Wang, C.; Liu, Z.; Du, X.; Ibarra, D.E. (Clays and Clay Minerals, 2015)
Sedimentary and diagenetic processes control the distribution of clay minerals in sedimentary basins, although these processes have seldom been studied continuously in continental sedimentary basins. The Songliao Basin, northeast China, is a large continental, petroleum-bearing basin, and provides a unique study site to understand the sedimentary and diagenetic processes that influence clay assemblages. In this paper, the clay mineralogy of a 2500 m-thick Late Cretaceous (late Turonian to Maastrichtian) terrestrial sedimentary succession (SK-1s and SK-1n cores), retrieved by the International Continental Scientific Drilling Program in the Songliao Basin, was examined. The objective was to determine the diagenetic and paleoenvironmental variations that controlled the formation of clay mineral assemblages, and to determine the thermal and paleoenvironmental evolution of the basin. The results from both cores show that illite is ubiquitous through the succession, smectite is frequently encountered in the upper strata, and ordered mixed-layer illite-smectite (I-S), chlorite, and kaolinite are abundant in the lower strata. Burial diagenesis is the primary control on the observed decrease of smectite and increasing illite, I-S, and chlorite with depth. Observations of clay-mineral diagenesis are used to reconstruct the paleotemperatures and maximum burial depths to which the sediments were subjected. The lowermost sediments could have reached a maximum burial of 1000 m deeper than today and temperatures 50ºC higher than today in the latest Cretaceous. The transition of smectite to I-S in the SK-1 cores and the inferred paleotemperatures provide new constraints for basin modeling of oil maturation at elevated temperatures in the Songliao Basin. Authigenic kaolinite and smectite are enriched in sandstones with respect to the coeval mudstones from the SK-1n core, as a result of early diagenesis with the participation of primary aluminosilicates and pore fluids. In the upper part of both SK-1 cores, variations in smectite and illite were controlled primarily by paleoenvironmental changes. Increases in smectite and decreases in illite from the late Campanian to Maastrichtian are interpreted as resulting from increasing humidity, a conclusion consistent with previous paleoenvironmental interpretations. © 2015, Clays and Clay Minerals. All rights reserved.
cited By 16
Keywords: Kaolinite; Minerals; Petroleum deposits; Process control; Sedimentology; Settling tanks; China; Diagenesis; Late cretaceous; Paleo-environment; Songliao basin; Thermal evolution; Clay minerals; aluminosilicate; Campanian; diagenesis; kaolinite; Maastrichtian; paleoenvironment; sedimentary basin; smectite; China; Songliao Basin

Detailed analysis of spatiotemporal variations of the stress field orientation along the Izmit-D{uzce rupture in NW Turkey from inversion of first-motion polarity data - Ickrath, M.; Bohnhoff, M.; Dresen, G.; Mart'inez-Garz'on, P.; Bulut, F.; Kwiatek, G.; Germer, O. (Geophysical Journal International, 2015)
We investigate spatiotemporal variations of the crustal stress field orientation along the rupture zones of the 1999 August Izmit Mw 7.4 and November D{uzce Mw 7.1 earthquakes at the North Anatolian Fault zone (NAFZ) in NW Turkey. Our primary focus is to elaborate on the relation between the state of the crustal stress field and distinct seismotectonic features as well as variations of coseismic slip within the seismogenic layer of the crust. To achieve this, we compile an extensive data base of hypocentres and first-motion polarities including a newly derived local hypocentre catalogue extending from 2 yr prior (1997) to 2 yr after (2001) the Izmit and D{uzce main shocks. This combined data set allows studying spatial and temporal variations of stress field orientation along distinct fault segments for the pre- and post-seimic phase of the two large earthquakes in detail. Furthermore, the occurrence of two M > 7 earthquakes in rapid succession gives the unique opportunity to analyse the 87-d-long 'inter-seismic phase' between them. We use the MOTSI (first MOTion polarity Stress Inversion) procedure directly inverting first-motion polarities to study the stress field evolution of nine distinct segments. In particular, this allows to determine the stress tensor also for the pre- and post-seismic phases when no stable single-event focal mechanisms can be determined. We observe significantly different stress field orientations along the combined 200-km-long rupture in accordance with lateral variations of coseismic slip and seismotectonic setting. Distinct vertical linear segments of the NAFZ show either pure-strike slip behaviour or transtensional and normal faulting if located near pull-apart basins. Pull-apart structures such as the Akyazi and D{uzce basins show a predominant normal faulting behaviour along the NAFZ and reflect clearly different characteristic from neighbouring strike-slip segments. Substantial lateral stress field heterogeneity following the two main shocks is observed that declines with time towards the post-seismic period that rather reflects the regional right-lateral strike-slip stress field. © The Authors 2015. Published by Oxford University Press on behalf of The Royal Astronomical Society. All rights reserved.
cited By 14
Keywords: Earthquake effects; Earthquakes; Faulting; Geophysics; Seismology; Stresses; Strike-slip faults; Earthquake dynamics; Earthquake source observations; North Anatolian Fault Zone; Seismicity and tectonics; Seismotectonic settings; Spatial and temporal variation; Spatio-temporal variation; Stress-field orientation; Fault slips; coseismic process; earthquake catalogue; earthquake rupture; focal mechanism; inverse problem; Kocaeli earthquake 1999; seismic data; seismic source; seismicity; spatiotemporal analysis; stress field; tectonics; Anatolia; Turkey

Depositional modes and lake-level variability at Lake Towuti, Indonesia, during the past 29 kyr BP - Russell, James M.; Cahyarini, Sri Yudawati; Bijaksana, Satria; Wattrus, Nigel; Rethemeyer, Janet (Journal of Paleolimnology, 2015)
Lake Towuti (2.5°S, 121.5°E) is a long-lived, tectonic lake located on the Island of Sulawesi, Indonesia, and in the center of the Indo-Pacific warm pool (IPWP). Lake Towuti is connected with upstream lakes Matano and Mahalona through the Mahalona River, which constitutes the largest inlet to the lake. The Mahalona River Delta is prograding into Lake Towuti’s deep northern basin thus exerting significant control on depositional processes in the basin. We combine high-resolution seismic reflection and sedimentological datasets from a 19.8-m-long sediment piston core from the distal edge of this delta to characterize fluctuations in deltaic sedimentation during the past 29 kyr BP and their relation to climatic change. Our datasets reveal that, in the present, sedimentation is strongly influenced by deposition of laterally transported sediments sourced from the Mahalona River Delta. Variations in the amount of laterally transported sediments, as expressed by coarse fraction amounts in pelagic muds and turbidite recurrence rates and cumulative thicknesses, are primarily a function of lake-level induced delta slope instability and delta progradation into the basin. We infer lowest lake-levels between 29 and 16, a gradual lake level rise between 16 and 11, and high lake-levels between 11 and 0 kyr BP. Periods of highest turbidite deposition, 26 to 24 and 18 to 16 kyr BP coincide with Heinrich events 2 and 1, respectively. Our lake-level reconstruction therefore supports previous observations based on geochemical hydroclimate proxies of a very dry last glacial and a wet Holocene in the region, and provides new evidence of millennial-scale variations in moisture balance in the IPWP. © 2015, Springer Science+Business Media Dordrecht.
Keywords: Greater Sunda Islands; Lake Mahalona; Lake Matano; Lake Towuti; Malili Lakes; South Sulawesi; Sulawesi; Sulawesi; Sunda Isles; climate change; deltaic sedimentation; depositional environment; Heinrich event; Holocene; lacustrine deposit; Last Glacial; pool; reconstruction; sedimentology; turbidity

Dead Sea drawdown and monsoonal impacts in the Levant during the last interglacial - Torfstein, A.; Goldstein, S.L.; Kushnir, Y.; Enzel, Y.; Haug, G.; Stein, M. (Earth and Planetary Science Letters, 2015)
Sediment cores recovered by the Dead Sea Deep Drilling Project (DSDDP) from the deepest basin of the hypersaline, terminal Dead Sea (lake floor at 725 m below mean sea level) reveal the detailed climate history of the lake's watershed during the last interglacial period (Marine Isotope Stage 5; MIS5). The results document both a more intense aridity during MIS5 than during the Holocene, and the moderating impacts derived from the intense MIS5e African Monsoon. Early MIS5e ( 133-128 ka) was dominated by hyperarid conditions in the Eastern Mediterranean-Levant, indicated by thick halite deposition triggered by a lake-level drop. Halite deposition was interrupted however, during the MIS5e peak ( 128-122 ka) by sequences of flood deposits, which are coeval with the timing of the intense precession-forced African monsoon that generated Mediterranean sapropel S5. A subsequent weakening of this humidity source triggered extreme aridity in the Dead Sea watershed and resulting in the biggest known lake level drawdown in its history, reflected by the deposition of thick salt layers, and a capping pebble layer corresponding to a hiatus at 116-110 ka. The DSDDP core provides the first evidence for a direct association of the African monsoon with mid subtropical latitude climate systems effecting the Dead Sea watershed. Combined with coeval deposition of Arabia and southern Negev speleothems, Arava travertines, and calcification of Red Sea corals, the evidence points to a climatically wet corridor that could have facilitated homo sapiens migration out of Africa during the MIS5e peak. The hyperaridity documented during MIS5e may provide an important analogue for future warming of arid regions of the Eastern Mediterranean-Levant. © 2014 Elsevier B.V.All rights reserved.
cited By 95
Keywords: Arid regions; Atmospheric thermodynamics; Biomineralization; Deposition; Glacial geology; Isotopes; Lakes; Sea level; Seawater; Watersheds; African monsoons; Dead sea; Last interglacial; Levant; Paleoclimates; Sapropel; Chloride minerals; aridity; deposition; drawdown; flood deposit; Holocene; humidity; Last Interglacial; monsoon; paleoclimate; sapropel; Dead Sea; Levant; Mediterranean Region; Mediterranean Sea; Mediterranean Sea (East); Anthozoa; Homo sapiens

Cyclostratigraphic studies of sediments from Lake Van (Turkey) based on their uranium contents obtained from downhole logging and paleoclimatic implications - Baumgarten, H.; Wonik, T. (International Journal of Earth Sciences, 2015)
A deep drilling campaign was performed at Lake Van (Turkey) to enhance the understanding of the paleoenvironmental conditions of the Middle East. Cores were collected, and the sediments are mainly composed of clayey silts and tephra deposits. Spectral gamma ray data were acquired (0 –210 m below lake floor), and the uranium data were used for cyclostratigraphic studies to estimate the sedimentation rates and the time of deposition. Detection and analysis of climate cycles require continuous sedimentation and cannot be applied to these sediments which include numerous tephra layers. Therefore, these layers were removed, and a synthetic log was created (cumulative thickness of the tephra ≈50 m; remaining lacustrine sediments ≈160 m). High amplitudes were detected and correlated to Milankovi cycles. Their evolution was analyzed using the sliding window technique. The sedimentation rates varied from 22 to 33 cm/ka in the upper section. The sediments between the lake floor and a depth of 210 m were deposited over a period of 587 ka. Our results agree with core interpretations (e.g., correlation of total organic carbon with marine isotope stages) which suggest a time span of deposition of 600 ka. High-frequency cycles were detected and correlated with interstadials from the North Greenland δ18O record for the past 75 ka. The two datasets agreed closely. We conclude that climate signals, even on sub-Milankovi scale, are imprinted in uranium of these sediments, and cyclostratigraphic methods are applicable if event layers are subtracted from the sediment record. © 2014, The Author(s).
cited By 12
Keywords: cyclostratigraphy; lacustrine deposit; logging (geophysics); Milankovitch cycle; paleoclimate; paleoenvironment; Quaternary; sediment core; sedimentation rate; tephra; uranium; Arctic; Greenland; Lake Van; Middle East; Turkey

Cretaceous-Paleogene Boundary Clays from Spain and New Zealand: Arsenic Anomalies - Premovi, P.I. (Open Geosciences, 2015)
Remarkably high arsenic (As) contents have been reported in numerous Cretaceous-Paleogene boundary (KPB) clays worldwide including those from Spain (at Caravaca and Agost) and New (N.) Zealand (at Woodside Creek). Two interpretations have been offered to explain this anomaly. The first one suggests that this As was generated by the combustion of fossil fuels (such as crude oil, coal or oil shales) near the Chicxulub impact site and the second interpretation proposes the post-impact combustion of the global biomass at the KPB. Both types of combustion were presumably triggered by the Chicxulub impactor. This report shows that the estimated surface densities of As in Spain and N. Zealand strongly contradict the fossil fuel hydrocarbons/biomass hypotheses. In addition, we also show that previously reported global abundances of As at KPB are greatly overestimated. The high abundances of iron (Fe) in the ejecta layers from Spain and N. Zealand lead us to a working hypothesis that a major fraction of their anomalous As was adsorbed from seawater by the Fe-oxides. These oxides were mainly derived of Fe from the vaporized carbonaceous chondrite impactor. These were originally deposited on the local (topographically high) oxic soils in Spain and N. Zealand and then laterally transported to the KPB sites by the impactinduced surface waters. © 2015 Pavle I. Premovi 2015.
cited By 2

COSC-1 operational report - Operational data sets - Lorenz, H.; Rosberg, J.-E.; Juhlin, Christopher; Bjelm, L.; Almqvist, B.S.G.; Berthet, T.; Conze, R.; Gee, D. G.; Klonowska, I.; Pascal, C.; Pedersen, K.; Roberts, N.; et al. (GFZ German Research Centre for Geosciences, 2015)
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COSC-1 - drilling of a subduction-related allochthon in the Palaeozoic Caledonide orogen of Scandinavia - Lorenz, Henning; Rosberg, J.-E.; Juhlin, C.; Bjelm, L.; Almqvist, B. S. G.; Berthet, T.; Conze, R.; Gee, D. G.; Klonowska, I.; Pascal, C.; Pedersen, K.; Roberts, N. M. W.; et al. (Scientific Drilling, 2015)
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Continuous 1.3-million-year record of East African hydroclimate, and implications for patterns of evolution and biodiversity - Lyons, R.P.; Scholz, C.A.; Cohen, A.S.; King, J.W.; Brown, E.T.; Ivory, S.J.; Johnson, T.C.; Deino, A.L.; Reinthal, P.N.; McGlue, M.M.; Blome, M.W. (Proceedings of the National Academy of Sciences of the United States of America, 2015)
The transport of moisture in the tropics is a critical process for the global energy budget and on geologic timescales, has markedly influenced continental landscapes, migratory pathways, and biological evolution. Here we present a continuous, first-of-its-kind 1.3-My record of continental hydroclimate and lake-level variability derived from drill core data from Lake Malawi, East Africa (9-15° S). Over the Quaternary, we observe dramatic shifts in effective moisture, resulting in large-scale changes in one of the world's largest lakes and most diverse freshwater ecosystems. Results show evidence for 24 lake level drops of more than 200 m during the Late Quaternary, including 15 lowstands when water levels were more than 400 m lower than modern. A dramatic shift is observed at the Mid-Pleistocene Transition (MPT), consistent with far-field climate forcing, which separates vastly different hydroclimate regimes before and after ∼800,000 years ago. Before 800 ka, lake levels were lower, indicating a climate drier than today, and water levels changed frequently. Following the MPT high-amplitude lake level variations dominate the record. From 800 to 100 ka, a deep, often overfilled lake occupied the basin, indicating a wetter climate, but these highstands were interrupted by prolonged intervals of extreme drought. Periods of high lake level are observed during times of high eccentricity. The extreme hydroclimate variability exerted a profound influence on the Lake Malawi endemic cichlid fish species flock; the geographically extensive habitat reconfiguration provided novel ecological opportunities, enabling new populations to differentiate rapidly to distinct species.
cited By 86
Keywords: water; Article; atmospheric moisture; biodiversity; catchment; cichlid; climate change; clinical effectiveness; East African; freshwater environment; hydroclimate; lake; Middle Pleistocene; molecular evolution; nonhuman; paleoclimate; priority journal; species diversity; tropic climate; Africa; animal; climate; ecosystem; evolution; history; paleontology; time factor; Africa; Eastern; Animals; Biodiversity; Biological Evolution; Cichlids; Climate; Climate Change; Ecosystem; History; Ancient; Lakes; Paleontology; Time Factors

Composition, Alteration, and Texture of Fault-Related Rocks from Safod Core and Surface Outcrop Analogs: Evidence for Deformation Processes and Fluid-Rock Interactions - Bradbury, K.K.; Davis, C.R.; Shervais, J.W.; Janecke, S.U.; Evans, J.P. (Pure and Applied Geophysics, 2015)
We examine the fine-scale variations in mineralogical composition, geochemical alteration, and texture of the fault-related rocks from the Phase 3 whole-rock core sampled between 3,187.4 and 3,301.4 m measured depth within the San Andreas Fault Observatory at Depth (SAFOD) borehole near Parkfield, California. This work provides insight into the physical and chemical properties, structural architecture, and fluid-rock interactions associated with the actively deforming traces of the San Andreas Fault zone at depth. Exhumed outcrops within the SAF system comprised of serpentinite-bearing protolith are examined for comparison at San Simeon, Goat Rock State Park, and Nelson Creek, California. In the Phase 3 SAFOD drillcore samples, the fault-related rocks consist of multiple juxtaposed lenses of sheared, foliated siltstone and shale with block-in-matrix fabric, black cataclasite to ultracataclasite, and sheared serpentinite-bearing, finely foliated fault gouge. Meters-wide zones of sheared rock and fault gouge correlate to the sites of active borehole casing deformation and are characterized by scaly clay fabric with multiple discrete slip surfaces or anastomosing shear zones that surround conglobulated or rounded clasts of compacted clay and/or serpentinite. The fine gouge matrix is composed of Mg-rich clays and serpentine minerals (saponite ± palygorskite, and lizardite ± chrysotile). Whole-rock geochemistry data show increases in Fe-, Mg-, Ni-, and Cr-oxides and hydroxides, Fe-sulfides, and C-rich material, with a total organic content of >1 % locally in the fault-related rocks. The faults sampled in the field are composed of meters-thick zones of cohesive to non-cohesive, serpentinite-bearing foliated clay gouge and black fine-grained fault rock derived from sheared Franciscan Formation or serpentinized Coast Range Ophiolite. X-ray diffraction of outcrop samples shows that the foliated clay gouge is composed primarily of saponite and serpentinite, with localized increases in Ni- and Cr-oxides and C-rich material over several meters. Mesoscopic and microscopic textures and deformation mechanisms interpreted from the outcrop sites are remarkably similar to those observed in the SAFOD core. Micro-scale to meso-scale fabrics observed in the SAFOD core exhibit textural characteristics that are common in deformed serpentinites and are often attributed to aseismic deformation with episodic seismic slip. The mineralogy and whole-rock geochemistry results indicate that the fault zone experienced transient fluid –rock interactions with fluids of varying chemical composition, including evidence for highly reducing, hydrocarbon-bearing fluids. © 2014, Springer Basel.
cited By 23
Keywords: Deformation; Geochemistry; Kaolinite; Lithology; Minerals; Nickel; Oil bearing formations; Petroleum deposits; Serpentine; Silicate minerals; Strike-slip faults; Structural geology; Sulfide minerals; Textures; X ray diffraction; Coast range ophiolites; Fluid-rock interaction; Mineralogical compositions; Physical and chemical properties; Structural architecture; Textural characteristic; Total organic contents; Whole-rock geochemistries; Rocks; chemical composition; deformation mechanism; fault zone; hydrochemistry; mineralization; protolith; San Andreas Fault; saponite; serpentinite; water-rock interaction; California; Parkfield; San Simeon; United States; Capra hircus

Earth science: Deadly combination - Duncan, R. (Nature, 2015)
New evidence suggests that seismic waves from the Chicxulub meteorite impact doubled the eruption rate of lavas on the opposite side of the planet - a combination that led to the mass extinction at the end of the Cretaceous period. © 2015 Macmillan Publishers Limited. All rights reserved.
cited By 0

CO2 degassing in the Hartoušov mofette area, western Eger Rift, imaged by CO2 mapping and geoelectrical and gravity surveys - Nickschick, Tobias; K{ampf, Horst; Flechsig, Christina; Mrlina, Jan; Heinicke, Jens (International Journal of Earth Sciences, 2015)
Strong, subcontinental mantle-dominated CO2 degassing occurs in the Hartoušov and Bubl'ak mofette fields in the western Eger Rift. The combination of CO2 gas flux and soil gas measurements as well as gravity and geoelectric surveys provides insight into the surface and subsurface of this unique mofette area. CO2 soil gas and gas flux measurements reveal that large amounts of carbon dioxide are released via channels with diameters below 1 m. Carbon dioxide emissions of several tens and up to more than 100 kg day−1 are ejected via these small seeps. Measurements with small spacings are necessary to account for the point like, focused gas discharge in the lesser degassing surrounding. We estimate that between 23 and 97 tons of CO2 are released over an area of about 350,000 m2 each day in the Hartoušov mofette field. The application of widely used geostatistical tools leads to estimations of the CO2 discharge with very high standard deviations due to the strong positive skewness of the data distribution. Geophysical investigations via electrical resistivity tomography and gravity measurements were carried out over areas of strong seepage and reveal distinct anomalies in the subsurface below mofettes, indicating rock and sediment alterations and/or sediment transport by pressurised, ascending CO2 and water mobilised by it. This study reveals that the gas emanations only occur west of a morphological step which is related to a N –S-oriented fault zone, the Počatky-Plesn'a fault zone. The results of CO2 mapping and the geophysical studies can track the course of this fault zone in this area. Our results fit into a tectonic model in which the mofette fields are in the centres of two independent pull-apart basin-like structures. We hypothesise that the sinistral strike-slip movement of the Počatky-Plesn'a fault zone leads to a pull-apart basin-like opening, at which the strong, mantle-derived CO2 degassing occurs nowadays. Since the Hartoušov and Bubl'ak mofette fields only illustrate examples along the N –S-striking Počatky-Plesn'a fault zone, its role and other N –S-striking faults’ roles of the Regensburg –Leipzig –Rostock zone for upper mantle degassing might have been underestimated previously. © 2015, Springer-Verlag Berlin Heidelberg.
Keywords: Cheb Basin; Czech Republic; Karlovarsky; carbon dioxide; carbon emission; carbon flux; degassing; electrical method; electrical resistivity; gravity survey

Clay mineral formation and fabric development in the DFDP-1B borehole, central Alpine Fault, New Zealand - Schleicher, A.M.; Sutherland, R.; Townend, J.; Toy, V.G.; Van Der Pluijm, B.A. (New Zealand Journal of Geology and Geophysics, 2015)
Clay minerals are increasingly recognised as important controls on the state and mechanical behaviour of fault systems in the upper crust. Samples retrieved by shallow drilling from two principal slip zones within the central Alpine Fault, South Island, New Zealand, offer an excellent opportunity to investigate clay formation and fluid-rock interaction in an active fault zone. Two shallow boreholes, DFDP-1A (100.6 m deep) and DFDP-1B (151.4 m) were drilled in Phase 1 of the Deep Fault Drilling Project (DFDP-1) in 2011. We provide a mineralogical and textural analysis of clays in fault gouge extracted from the Alpine Fault. Newly formed smectitic clays are observed solely in the narrow zones of fault gouge in drill core, indicating that localised mineral reactions are restricted to the fault zone. The weak preferred orientation of the clay minerals in the fault gouge indicates minimal strain-driven modification of rock fabrics. While limited in extent, our results support observations from surface outcrops and faults systems elsewhere regarding the key role of clays in fault zones and emphasise the need for future, deeper drilling into the Alpine Fault in order to understand correlative mineralogies and fabrics as a function of higher temperature and pressure conditions. © 2015 The Royal Society of New Zealand.
cited By 26
Keywords: active fault; borehole; clay mineral; fault gouge; fault zone; mineralogy; smectite; water-rock interaction; Alpine Fault Zone; New Zealand; South Island

Characterizing clay mineralogy in Lake Towuti, Indonesia, with reflectance spectroscopy - Weber, Andrea K.; Russell, James M.; Goudge, Timothy A.; Salvatore, Mark R.; Mustard, John F.; Bijaksana, Satria (Journal of Paleolimnology, 2015)
We tested the use of visible to near-infrared (VNIR) reflectance spectroscopy to characterize the relative abundances of clay minerals in sediments from Lake Towuti, a large tectonic lake in Sulawesi, Indonesia. We measured VNIR spectra of lake and river sediments from Lake Towuti and its catchment to identify clay minerals, fit major VNIR absorption features with a modified Gaussian model to estimate relative abundances of these minerals, and compared these absorptions to the samples’ chemistry to test the utility of VNIR spectroscopy to characterize sediment compositional variations. We found that major absorptions are caused by vibrations of Al –OH in kaolinite (2.21 μm), Fe –OH in nontronite (2.29 μm), Mg –OH in saponite and serpentine (2.31 μm), and Mg –OH in serpentine (2.34 μm). This was confirmed with X-ray diffraction data. The correlations between absorption band areas for Fe –OH, Al –OH, and Mg –OH vibrations and Fe, Al and Mg concentrations, respectively, are statistically significant, varying between r = 0.51 and r = 0.90, and spatial variations in inferred clay mineralogy within the lake are consistent with variations in the geology of the catchment. We conclude that VNIR spectroscopy is an effective way to characterize the clay mineralogy of lake sediments, and can be used to investigate changes in mineral inputs to lake deposits. © 2015, Springer Science+Business Media Dordrecht.
Keywords: Greater Sunda Islands; Lake Towuti; Malili Lakes; South Sulawesi; Sulawesi; Sulawesi; Sunda Isles; clay mineral; fluvial deposit; lacustrine deposit; paleolimnology; relative abundance; spatial variation; spectroscopy

Changes in hot spring temperature and hydrogeology of the Alpine Fault hanging wall, New Zealand, induced by distal South Island earthquakes - Cox, S.C.; Menzies, C.D.; Sutherland, R.; Denys, P.H.; Chamberlain, C.; Teagle, D.A.H. (Geofluids, 2015)
Thermal springs in the Southern Alps, New Zealand, originate through penetration of fluids into a thermal anomaly generated by rapid uplift and exhumation on the Alpine Fault. Copland hot spring (43.629S, 169.946E) is one of the most vigorously flowing, hottest of the springs, discharging strongly effervescent CO2-rich 56-58°C water at 6 ± 1 l sec-1. Shaking from the Mw7.8 Dusky Sound (Fiordland) 2009 and Mw7.1 Darfield (Canterbury) 2010 earthquakes, 350 and 180 km from the spring, respectively, resulted in a characteristic approximately 1°C delayed cooling over 5 days. A decrease in conductivity and increase in pH were measured following the Mw7.1 Darfield earthquake. Earthquake-induced decreases in Cl, Li, B, Na, K, Sr and Ba concentrations and an increase in SO4 concentration reflect higher proportions of shallow-circulating meteoric fluid mixing in the subsurface. Shaking at amplitudes of approximately 0.5% g Peak Ground Acceleration (PGA) and/or 0.05-0.10 MPa dynamic stress influences Copland hot spring temperature, which did not respond during the Mw6.3 Christchurch 2011 aftershock or other minor earthquakes. Such thresholds should be exceeded every 1-10 years in the central Southern Alps. The characteristic cooling response at low shaking intensities (MM III-IV) and seismic energy densities (approximately 10-1 J m-3) from intermediate-field distances was independent of variations in spectral frequency, without the need for post-seismic recovery. Observed temperature and fluid chemistry responses are inferred to reflect subtle changes in the fracture permeability of schist mountains adjacent to the spring. Permanent 10-7-10-6 strains recorded by cGPS reflect opening or generation of fractures, allowing greater quantities of relatively cool near-surface groundwater to mix with upwelling hot water. Active deformation, tectonic and topographic stress in the Alpine Fault hanging wall, where orographic rainfall, uplift and erosion are extreme, make the Southern Alps hydrothermal system particularly susceptible to earthquake-induced transient permeability. © 2014 The Authors Geofluids Published by John Wiley & Sons Ltd.
cited By 60
Keywords: earthquake; exhumation; fluid flow; geothermal system; hanging wall; hydrogeology; permeability; temperature anomaly; thermal spring; uplift; Alpine Fault Zone; New Zealand; South Island; Southern Alps

Carbonate deposition in the Palaeoproterozoic Onega basin from Fennoscandia: a spotlight on the transition from the Lomagundi-Jatuli to Shunga events - Melezhik, Victor A; Fallick, Anthony E; Brasier, Alexander T; Lepland, Aivo (Earth-Science Reviews, 2015)
Several deep drillholes were made in the Onega palaeobasin by the Fennoscandian Arctic Russia-Drilling Early Earth Project (FAR-DEEP) of the International Continental Scientific Drilling Program (ICDP). These provided fresh core material documenting the Lomagundi-Jatuli Isotopic Event (LJIE), its termination, and the start of the Shunga Event (SHE) of an enhanced accumulation of organic matter. The cored section represents the most complete known record of the end of the LJIE.The late phase of the LJIE, recorded in FAR-DEEP Core 11A, is represented by the upper part of the Tulomozero Formation (TF), a 300-m-thick unit composed of variegated dolostones, siltstones and shales. Accumulated under oxic conditions on a shallow-water carbonate platform, the TF hosts the earliest known thick formations of halite and massive anhydrite. Low-temperature greenschist facies metamorphism caused partial recrystallisation of the rocks; however, a primary carbonate phase, the dolomite, exhibits a negligible degree of post-depositional alteration of the carbon isotope system. The dataset of 46 bulk-carbonate analyses of carbon and oxygen isotopes yielded δ13Ccarb ranging between +6.8 and +11.8‰, and revealed a positive excursion from +8 to +11.8‰ followed by a decline to +8‰ towards the top of the 300-m-thick succession.The cored part of the overlying Zaonega Formation (ZF) recovered in holes 12AB and 13A is an 800-m-thick unit composed of mixed siliciclastic-carbonate facies with numerous mafic lava flows and tuff beds intruded by gabbro sills. The formation represents an unprecedented episode of enhanced accumulation of organic-rich rocks and preserves the earliest known supergiant, petrified oilfield, all typifying the SHE. The sedimentological, petrographic, geochemical and C- and O-isotopic study of over 800m of core throughout the ZF suggests that the initial carbonate deposition occurred in a lacustrine environment, then rapidly proceeding through a lagoonal setting to a rifted deepwater shelf, and finally to a carbonate platform. Both the deepwater shelf and the platformal settings are marked by organic-rich environments. The primary dolomite was potentially exposed to syn- and post-depositional hydrothermal/metasomatic alterations, organic matter diagenesis, metamorphic mineral reactions, CO2 degassing, and finally a low-temperature, post-metamorphic calcitisation resulting in overall large fluctuations of δ13Ccarb between -22 and +8‰. The dataset of over 413 bulk-carbonate analyses of carbon and oxygen isotopes, screened petrographically and geochemically against post-depositional alteration, revealed 28 least-altered samples within three stratigraphic intervals, suggesting multiple positive and negative δ13Ccarb excursions throughout over 1000m of stratigraphy. A shift from +5 to +9‰ followed by a drop to near zero values marks the lower part of the ZF. A δ13Ccarb decline from +8‰ to below zero in the middle and upper part of the ZF defines the end of the LJIE. A subsequent prominent negative excursion down to -6‰ does not show convincing isotopic evidence for influence of methanogenesis, and hence appears to be of primary depositional origin. An erratic positive excursion in the uppermost part of the drilled section indicates return of δ13Ccarb to a near normal marine value. © 2015 Elsevier B.V.
cited By 26
Keywords: bitumen; carbon isotope; carbonate platform; depositional environment; dolomite; lithostratigraphy; organic matter; Proterozoic; sediment core; Arkhangelsk [Russian Federation]; Fennoscandia; Onega Basin; Russian Federation

An innovative optical and chemical drill core scanner - Sj{oqvist, A. S. L.; Arthursson, M.; Lundstr{om, A.; Calder'on Estrada, E.; Inerfeldt, A.; Lorenz, H. (Scientific Drilling, 2015)
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Age-depth model of the past 630 kyr for Lake Ohrid (FYROM/Albania) based on cyclostratigraphic analysis of downhole gamma ray data - Baumgarten, H.; Wonik, T.; Tanner, D.C.; Francke, A.; Wagner, B.; Zanchetta, G.; Sulpizio, R.; Giaccio, B.; Nomade, S. (Biogeosciences, 2015)
Gamma ray (GR) fluctuations and potassium (K) values from downhole logging data obtained in the sediments of Lake Ohrid from 0 to 240 m below lake floor (b.l.f). correlate with fluctuations in δ18O values from the global benthic isotope stack LR04 (Lisiecki and Raymo, 2005). GR and K values are considered a reliable proxy to depict glacial-interglacial cycles, with high clastic input during cold and/or drier periods and high carbonate precipitation during warm and/or humid periods at Lake Ohrid. Spectral analysis was applied to investigate the climate signal and evolution over the length of the borehole. Linking downhole logging data with orbital cycles was used to estimate sedimentation rates and the effect of compaction was compensated for. Sedimentation rates increase on average by 14 % after decompaction of the sediment layers and the mean sedimentation rates shift from 45 cm kyr-1 between 0 and 110 m to 30 cm kyr-1 from 110 to 240 m b.l.f. Tuning of minima and maxima of gamma ray and potassium values versus LR04 extrema, in combination with eight independent tephrostratigraphical tie points, allows establishing of a robust age model for the downhole logging data over the past 630 kyr. © Author(s) 2015.
Keywords: Lake Ohrid; age determination; benthos; carbonate; climate signal; cyclostratigraphy; gamma ray radiation; glacial-interglacial cycle; lacustrine deposit; oxygen isotope; potassium; precipitation (chemistry); sedimentation rate

Accelerating Neoproterozoic research through scientific drilling - Condon, D.J.; Boggiani, P.; Fike, D.; Halverson, G.P.; Kasemann, S.; Knoll, A.H.; Macdonald, F.A.; Prave, A.R.; Zhu, M. (Scientific Drilling, 2015)
cited By 5
Keywords: Energy resources; Mechanical engineering; Neoproterozoic; Scientific drilling; Drilling

Abrupt climate and vegetation variability of eastern Anatolia during the last glacial - Pickarski, N.; Kwiecien, O.; Langgut, D.; Litt, T. (Climate of the Past, 2015)
Detailed analyses of the Lake Van pollen, Ca / K ratio, and stable oxygen isotope record allow the identification of millennial-scale vegetation and environmental changes in eastern Anatolia throughout the last glacial (∼ 111.5-11.7 ka BP). The climate of the last glacial was cold and dry, indicated by low arboreal pollen (AP) levels. The driest and coldest period corresponds to Marine Isotope Stage (MIS) 2 (∼ 28-14.5 ka BP), which was dominated by highest values of xerophytic steppe vegetation. Our high-resolution multi-proxy record shows rapid expansions and contractions of tree populations that reflect variability in temperature and moisture availability. These rapid vegetation and environmental changes can be related to the stadial-interstadial pattern of Dansgaard-Oeschger (DO) events as recorded in the Greenland ice cores. Periods of reduced moisture availability were characterized by enhanced occurrence of xerophytic species and high terrigenous input from the Lake Van catchment area. Furthermore, the comparison with the marine realm reveals that the complex atmosphere-ocean interaction can be explained by the strength and position of the westerlies, which are responsible for the supply of humidity in eastern Anatolia. Influenced by the diverse topography of the Lake Van catchment, more pronounced DO interstadials (e.g., DO 19, 17-16, 14, 12 and 8) show the strongest expansion of temperate species within the last glacial. However, Heinrich events (HE), characterized by highest concentrations of ice-rafted debris (IRD) in marine sediments, cannot be separated from other DO stadials based on the vegetation composition in eastern Anatolia. In addition, this work is a first attempt to establish a continuous microscopic charcoal record for the last glacial in the Near East. It documents an immediate response to millennial-scale climate and environmental variability and enables us to shed light on the history of fire activity during the last glacial. © Author(s) 2015.
cited By 41
Keywords: carbon isotope; catchment; charcoal; climate variation; concentration (composition); Dansgaard-Oeschger cycle; GRIP; humidity; marine sediment; moisture; proxy climate record; stable isotope; Anatolia; Arctic; Greenland; Greenland Ice Sheet; Lake Van; Turkey

A History of Exploration for and Discovery of Finland's Ore Deposits - Haapala, I.; Papunen, H. (Mineral Deposits of Finland, 2015)
Historically documented mining in Finland started in the 1530s when the area formed part of Sweden. The post of commissioner of mines was founded in 1638. The Swedish government activated mineral exploration in Finland in the seventeenth century and, during the Age of Utility, in the eighteenth century. Numerous small iron, copper, and lead occurrences were found, as well as the larger Orij{arvi copper deposit. During 1809-1917 when Finland was a Grand Duchy within the Russian Empire, exploration was reorganized and strengthened. New, generally small iron deposits were discovered to supply iron works. Deposits found in the Pitk{aranta area were mined for copper, tin, zinc, and iron. The Geological Survey of Finland was established in 1885. The large and rich Outokumpu copper deposit was discovered in 1910 as a result of scientific exploration by Otto Tr{ustedt of the Geological Survey. Since then, boulder tracing (later also till geochemistry), geophysical measurements, and diamond drilling have been the standard exploration methods. After Finland declared independence in 1917, mineral exploration was considered important for the development of domestic industry. In 1921 the Geological Survey discovered the nickel-copper ore field of Petsamo, and by the end of the 1930s, several other deposits, including the Otanm{aki iron-titanium-vanadium deposit, were discovered. After the Second World War, the Geological Survey was reorganized and strengthened, and in the following decades it discovered numerous important ore deposits, including the Vihanti zinc-copper deposit (1951) and the Kemi chromium deposit (1960). The state-owned mining companies Outokumpu Oy and Rautaruukki Oy established their own exploration departments in the 1950s. Outokumpu Oy discovered the Kotalahti (1956), Vammala, and Kylm{akoski nickel-copper deposits, the Pyh{asalmi copper-zinc deposit (1958), the Vuonos (1965) and Kylylahti (1984) Outokumpu-type deposits, and several gold deposits. Otanm{aki Oy/Rautaruukki Oy discovered several iron deposits in Lapland, as well as the large apatite-rich Sokli carbonatite complex. Rautaruukki Oy terminated their exploration activities in 1985 and Outokumpu Oy in 2003. Finnish private companies also carried out successful mineral exploration. After becoming a member of the European Union in 1995, the role of international mining and exploration companies has strongly increased in Finland, the main interest being in precious metal deposits. © 2015 Elsevier Inc. All rights reserved.
Keywords: Copper nickel deposits; Copper zinc deposits; Deposits; Diamond drilling; Economic geology; Geological surveys; History; Iron deposits; Military operations; Mineral exploration; Mineral industry; Natural resources exploration; Nickel; Nickel deposits; Ore deposits; Ores; Phosphate minerals; Tin deposits; Titanium deposits; Vanadium deposits; Domestic industries; Exploration company; Exploration methods; Finland; Geophysical measurements; Outokumpu Oy; Rautaruukki Oy; Scientific exploration; Gold deposits

A high-resolution Late Glacial to Holocene record of environmental change in the Mediterranean from Lake Ohrid (Macedonia/Albania) - Lacey, Jack H.; Francke, Alexander; Leng, Melanie J.; Vane, Christopher H.; Wagner, Bernd (International Journal of Earth Sciences, 2015)
Lake Ohrid (Macedonia/Albania) is the oldest extant lake in Europe and exhibits an outstanding degree of endemic biodiversity. Here, we provide new high-resolution stable isotope and geochemical data from a 10 m core (Co1262) through the Late Glacial to Holocene and discuss past climate and lake hydrology (TIC, δ13Ccalcite, δ18Ocalcite) as well as the terrestrial and aquatic vegetation response to climate (TOC, TOC/N, δ13Corganic, Rock Eval pyrolysis). The data identifies 3 main zones: (1) the Late Glacial –Holocene transition represented by low TIC and TOC contents, (2) the early to mid-Holocene characterised by high TOC and increasing TOC/N and (3) the Late Holocene –Present which shows a marked decrease in TIC and TOC. In general, an overall trend of increasing δ18Ocalcite from 9 ka to present suggests progressive aridification through the Holocene, consistent with previous records from Lake Ohrid and the wider Mediterranean region. Several proxies show commensurate excursions that imply the impact of short-term climate oscillations, such as the 8.2 ka event and the Little Ice Age. This is the best-dated and highest resolution archive of past Late Glacial and Holocene climate from Lake Ohrid and confirms the overriding influence of the North Atlantic in the north-eastern Mediterranean. The data presented set the context for the International Continental scientific Drilling Program Scientific Collaboration On Past Speciation Conditions in Lake Ohrid project cores recovered in spring –summer 2013, potentially dating back into the Lower Pleistocene, and will act as a recent calibration to reconstruct climate and hydrology over the entire lake history. © 2014, Springer-Verlag Berlin Heidelberg.
Keywords: Albania; Lake Ohrid; Macedonia [Southern Europe]; Mediterranean Region; climate oscillation; environmental change; geochemistry; Holocene; late glacial; paleoclimate; paleoenvironment; paleolimnology; sediment core; stable isotope

A GCM comparison of Pleistocene super-interglacial periods in relation to Lake El'gygytgyn, NE Arctic Russia - Coletti, A.J.; DeConto, R.M.; Brigham-Grette, J.; Melles, M. (Climate of the Past, 2015)
Until now, the lack of time-continuous, terrestrial paleoenvironmental data from the Pleistocene Arctic has made model simulations of past interglacials difficult to assess. Here, we compare climate simulations of four warm interglacials at Marine Isotope Stages (MISs) 1 (9 ka), 5e (127 ka), 11c (409 ka) and 31 (1072 ka) with new proxy climate data recovered from Lake El'gygytgyn, NE Russia. Climate reconstructions of the mean temperature of the warmest month (MTWM) indicate conditions up to 0.4, 2.1, 0.5 and 3.1 °C warmer than today during MIS 1, 5e, 11c and 31, respectively. While the climate model captures much of the observed warming during each interglacial, largely in response to boreal summer (JJA) orbital forcing, the extraordinary warmth of MIS 11c compared to the other interglacials in the Lake El'gygytgyn temperature proxy reconstructions remains difficult to explain. To deconvolve the contribution of multiple influences on interglacial warming at Lake El'gygytgyn, we isolated the influence of vegetation, sea ice and circum-Arctic land ice feedbacks on the modeled climate of the Beringian interior. Simulations accounting for climate-vegetation-land-surface feedbacks during all four interglacials show expanding boreal forest cover with increasing summer insolation intensity. A deglaciated Greenland is shown to have a minimal effect on northeast Asian temperature during the warmth of stages 11c and 31 (Melles et al., 2012). A prescribed enhancement of oceanic heat transport into the Arctic Ocean does have some effect on Lake El'gygytgyn's regional climate, but the exceptional warmth of MIS l1c remains enigmatic compared to the modest orbital and greenhouse gas forcing during that interglacial. © Author(s) 2015.
cited By 14
Keywords: boreal forest; climate forcing; climate modeling; greenhouse gas; heat transfer; lake ecosystem; land surface; marine isotope stage; paleoclimate; paleoenvironment; Pleistocene; proxy climate record; Arctic Ocean; Chukchi; Elgygytgyn Lake; Russian Federation; Russian Federation

Low resistivity and permeability in actively deforming shear zones on the San Andreas Fault at SAFOD - Morrow, C.; Lockner, D.A.; Hickman, S. (Journal of Geophysical Research: Solid Earth, 2015)
The San Andreas Fault Observatory at Depth (SAFOD) scientific drill hole near Parkfield, California, crosses the San Andreas Fault at a depth of 2.7 km. Downhole measurements and analysis of core retrieved from Phase 3 drilling reveal two narrow, actively deforming zones of smectite-clay gouge within a roughly 200 m wide fault damage zone of sandstones, siltstones, and mudstones. Here we report electrical resistivity and permeability measurements on core samples from all of these structural units at effective confining pressures up to 120 MPa. Electrical resistivity ( 10 Ω-m) and permeability (10-21 to 10-22 m2) in the actively deforming zones were 1 to 2 orders of magnitude lower than the surrounding damage zone material, consistent with broader-scale observations from the downhole resistivity and seismic velocity logs. The higher porosity of the clay gouge, 2 to 8 times greater than that in the damage zone rocks, along with surface conduction were the principal factors contributing to the observed low resistivities. The high percentage of fine-grained clay in the deforming zones also greatly reduced permeability to values low enough to create a barrier to fluid flow across the fault. Together, resistivity and permeability data can be used to assess the hydrogeologic characteristics of the fault, key to understanding fault structure and strength. The low resistivities and strength measurements of the SAFOD core are consistent with observations of low resistivity clays that are often found in the principal slip zones of other active faults making resistivity logs a valuable tool for identifying these zones. © Published 2015. This article is a U.S. Government work and is in the public domain in the USA.
cited By 8
Keywords: active fault; deformation; electrical resistivity; fault gouge; permeability; porosity; San Andreas Fault; sediment core; shear zone; California; Parkfield; United States

Drilling through the largest magma chamber on Earth: Bushveld Igneous complex Drilling Project (BICDP) - Trumbull, RB; Ashwal, LD; Webb, SJ; Veksler, IV (Scientific Drilling, 2015)

Compound-specific carbon isotope study on the hydrocarbon biomarkers in lacustrine source rocks from Songliao Basin - Wang, L.; Song, Z.; Cao, X.; Li, Y. (Organic Geochemistry, 2015)
Stable carbon isotopic composition of organic matter (δ13Corg) and compound-specific δ13C values of biomarkers from 15 lacustrine source rocks were analyzed to identify the original paleoenvironment and source organisms. The δ13C values of hopanes (δ13Chop) ranged from -68.7‰ to -32‰ and exhibit strongly 13C-depleted values in the lower part of Member 1 of the Nenjiang Formation (K2n1, up to -68.7‰), suggesting an origin from predominantly methanotrophic bacteria. 13C-enriched δ13CGa values and significantly 13C-depleted δ13Chop in K2n1, which coincide with water stratification and an intermittent anoxic photic zone, represents a shallow chemocline. The presence of an intermittent anoxic photic zone, which means that the anoxia expanded into the euphotic zone, is beneficial for OM preservation and results in high values of TOC and HI in this section. However, the absence of gammacerane and 13C-enrichment of δ13Chop in Member 2 of Nenjiang Formation (K2n2) reflect a deeper chemocline, corresponding to relatively oxidizing conditions and low values of TOC and HI. Moreover, the negative correlation of TOC vs δ13Corg and HI vs δ13Corg reflects the control of OM formation by sedimentary environments rather than productivity in the water column. Thus, the depth of the chemocline not only controls the abundance of OM but also affects the development of the microbial community, such as chemoautotrophic bacteria in the deep chemocline and chemoautotrophic and methanotrophic bacteria in the shallow chemocline. Moreover, δ13CGa and δ13C values for 4-methyl steranes are related to water salinity, with a higher salinity accompanied by 13C-enrichment in gammacerane and 4-methyl steranes. © 2015 Elsevier Ltd.
cited By 16
Keywords: Bacteria; Gallium; Isotopes; Carbon isotopes; Chemocline; Nenjiang Formation; Paleo-environment; Upper Cretaceous; Biomarkers; anoxic conditions; carbon isotope; chemoautotrophy; Cretaceous; economic geology; hydrocarbon; isotopic composition; lacustrine environment; microbial community; paleoenvironment; source rock; stratification; China; Nen Basin; Songliao Basin

Environmental change and human occupation of southern Ethiopia and northern Kenya during the last 20,000 years - Foerster, V.; Vogelsang, R.; Junginger, A.; Asrat, A.; Lamb, H.F.; Schaebitz, F.; Trauth, M.H. (Quaternary Science Reviews, 2015)
Our understanding of the impact of climate-driven environmental change on prehistoric human populations is hampered by the scarcity of continuous paleoenvironmental records in the vicinity of archaeological sites. Here we compare a continuous paleoclimatic record of the last 20 ka before present from the Chew Bahir basin, southwest Ethiopia, with the available archaeological record of human presence in the region. The correlation of this record with orbitally-driven insolation variations suggests a complex nonlinear response of the environment to climate forcing, reflected in several long-term and short-term transitions between wet and dry conditions, resulting in abrupt changes between favorable and unfavorable living conditions for humans. Correlating the archaeological record in the surrounding region of the Chew Bahir basin, presumably including montane and lake-marginal refugia for human populations, with our climate record suggests a complex interplay between humans and their environment during the last 20 ka. The result may contribute to our understanding of how a dynamic environment may have impacted the adaptation and dispersal of early humans in eastern Africa. © 2015 Elsevier Ltd.
cited By 42
Keywords: Geology; Natural sciences; Adaption; Archeology; Chew Bahir; Foragers; Humid periods; Hunter-gatherers; Migration; Paleoclimates; Pastoralism; Push factor; Climate change; adaptation; archaeological evidence; climate forcing; climate variation; environmental change; historical time (human history); migration; paleoclimate; paleoenvironment; pastoralism; Africa; Ethiopia; Kenya

High resolution continuous sedimentary records of Upper Cretaceous obtained from the continental drilling (SK-1) borehole in Songliao Basin: Sifangtai and Mingshui Formations - Wang, G.; Cheng, R.; Wang, P.; Gao, Y.; Wang, C.; Ren, Y.; Huang, Q. (Geoscience Frontiers, 2015)
The Sifangtai and Mingshui formations were continuously cored in the SK-1n borehole (China Cretaceous Continental Scientific Drilling-SongKe1-the north borehole). The core is 767.96 m long, and the recovery is 94.7%. The ages of the formations range from middle Campanian to Danian. The sequence and process of lithology-lithofacies and cyclic stratigraphy were described in detail. Eight litho-types compose the Sifangtai Formation, and 15 litho-types compose the Mingshui Formation. Deposition was predominantly in meandering river and lacustrine environments, including 10 microfacies in the Sifangtai Formation and 15 microfacies in the Mingshui Formation. The complete sequence is composed of 535 m-scale cycles (sixth-order cycle), 152 fifth-order cycles, 42 fourth-order cycles and five third-order cycles. The centimeter-scale description of the section revealed some previously unknown horizons such as a special type of mudstone, marl, volcanic ash and favorable sand reservoirs in the formations. The new-found evidence is very important for the interpretation of the evolution of the basin, conditions such as lake oxic events, the K/Pg boundary, tectonism in the late sag basin stage, and the reservoir-cap rock assemblages in the shallow stratigraphy. © 2015 China University of Geosciences (Beijing) and Peking University.
cited By 14
Keywords: age determination; basin evolution; borehole; Campanian; Danian; drilling; facies analysis; geological record; lithofacies; lithology; sedimentary structure; stratigraphy; tectonic setting; China; Songliao Basin

Lateglacial and Holocene climatic changes in south-eastern Patagonia inferred from carbonate isotope records of Laguna Potrok Aike (Argentina) - Oehlerich, M.; Mayr, C.; Gussone, N.; Hahn, A.; H{olzl, S.; L{ucke, A.; Ohlendorf, C.; Rummel, S.; Teichert, B.M.A.; Zolitschka, B. (Quaternary Science Reviews, 2015)
First results of strontium, calcium, carbon and oxygen isotope analyses of bulk carbonates from a 106m long sediment record of Laguna Potrok Aike, located in southern Patagonia are presented. Morphological and isotopic investigations of μm-sized carbonate crystals in the sediment reveal an endogenic origin for the entire Holocene. During this time period the calcium carbonate record of Laguna Potrok Aike turned out to be most likely ikaite-derived. As ikaite precipitation in nature has only been observed in a narrow temperature window between 0 and 7°C, the respective carbonate oxygen isotope ratios serve as a proxy of hydrological variations rather than of palaeotemperatures. We suggest that oxygen isotope ratios are sensitive to changes of the lake water balance induced by intensity variations of the Southern Hemisphere Westerlies and discuss the role of this wind belt as a driver for climate change in southern South America. In combination with other proxy records the evolution of westerly wind intensities is reconstructed. Our data suggest that weak SHW prevailed during the Lateglacial and the early Holocene, interrupted by an interval with strengthened Westerlies between 13.4 and 11.3kacalBP. Wind strength increased at 9.2kacalBP and significantly intensified until 7.0kacalBP. Subsequently, the wind intensity diminished and stabilised to conditions similar to present day after a period of reduced evaporation during the Little Ice Age. Strontium isotopes (87Sr/86Sr ratio) were identified as a potential lake-level indicator and point to a lowering from overflow conditions during the Glacial ( 17kacalBP) to lowest lake levels around 8kacalBP. Thereafter the strontium isotope curve resembles the lake-level curve which is stepwise rising until the Little Ice Age. The variability of the Ca isotope composition of the sediment reflects changes in the Ca budget of the lake, indicating higher degrees of Ca utilisation during the period with lowest lake level. © 2015 Elsevier Ltd.
Keywords: Argentina; Laguna Potrok Aike; Patagonia; Santa Cruz [Argentina]; Budget control; Calcite; Calcium; Calcium carbonate; Carbon; Carbonation; Climate change; Glacial geology; Isotopes; Lakes; Oxygen; Sediments; Calcium isotopes; Carbon isotopes; ICDP; Ikaite; Lake sediments; Oxygen isotopes; PASADO; Southern south america; Strontium isotopes; carbonate; climate variation; evaporation; Holocene; ikaite; isotopic composition; lacustrine deposit; late glacial; oxygen isotope; paleoclimate; paleotemperature; proxy climate record; strontium isotope; westerly; Strontium

Episodes of environmental stability versus instability in Late Cenozoic lake records of Eastern Africa - Trauth, Martin H.; Bergner, Andreas G.N.; Foerster, Verena; Junginger, Annett; Maslin, Mark A.; Schaebitz, Frank (Journal of Human Evolution, 2015)

Late Glacial and Early Holocene cyclic changes in paleowind conditions and lake levels inferred from diatom assemblage shifts in Laguna Potrok Aike sediments (southern Patagonia, Argentina) - Zimmermann, Claudia; Jouve, Guillaume; Pienitz, Reinhard; Francus, Pierre; Maidana, Nora I. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2015)

Lake Qinghai sediment geochemistry linked to hydroclimate variability since the last glacial - Jin, Z.; An, Z.; Yu, J.; Li, F.; Zhang, F. (Quaternary Science Reviews, 2015)
Geochemistry of basin sediments from semi-arid regions is valuable to understand past hydroclimatic changes. Here, we investigate the links of sedimentary geochemistry (Rb, Sr, Ca/Zr, TOC, and %CaCO3), carbonate mineralogy and ostracod shell δ18O of Lake Qinghai, a basin proximal to major dust production centers at mid-latitudes of the Northern Hemisphere, to changes in depositional conditions and hydroclimate during the past 32ka. Surface lacustrine sediments are characterized by low-Rb, high-Sr, low-Rb/Sr, high-%CaCO3 and high-Ca/Zr values, in contrast to the chemical compositions of eolian loess (high-Rb, low-Sr, high-Rb/Sr, low-%CaCO3, and low-Ca/Zr). A direct comparison of soluble Ca and Sr in two short cores with instrumental water discharge data suggests that lacustrine precipitates in Lake Qinghai are dominated by authigenic aragonite formed under Ca2+-limited water conditions, and that the accumulation rate of aragonite dominantly depends on solute fluxes into the lake during the rainy seasons (late May to September). Our high-resolution down-core records show that sediments during the last glacial ( 32-19.8ka) had high-Rb, low-Sr, low-%CaCO3, and low-Ca/Zr, indicating eolian dust (loess) accumulation in a desiccated basin under dry glacial conditions, further supported by grain size and pollen results. This type of sedimentation was maintained during the last deglacial ( 19.8-11.5ka), but interrupted by episodic lacustrine precipitates with high-Sr, high-%CaCO3, high-Ca/Zr, and low-Rb. At 11.5ka, sedimentary Rb/Sr, Ca/Zr, %CaCO3 and TOC show dramatic and permanent changes, implying an abrupt shift in the atmospheric circulation at the onset of the Holocene in the Lake Qinghai region. Lacustrine precipitates have persisted throughout the Holocene with a maximum during the early to mid-Holocene ( 10.5-8.0ka). Since 8.0ka, the gradual and significant decreases in aragonite and Sr accumulations in tandem with increasing dust deposit and more positive ostracod δ18O may be linked to a weakening of Asian summer monsoons during the mid-to-late Holocene. Overall, our records appear to show a high sensitivity of sediment development and geochemistry in Lake Qinghai to the regional hydroclimate changes since the last glacial. © 2015 Elsevier Ltd.
cited By 74
Keywords: Animals; Arid regions; Calcium; Carbonate minerals; Dust; Geochemistry; Glacial geology; Lakes; Minerals; Precipitates; Rubidium; Sedimentology; Asian dust; Hydroclimate; Lake Qinghai; Lake waters; Sediment geochemistries; Sediments; aragonite; calcium carbonate; chemical composition; climate variation; eolian process; lacustrine deposit; Last Glacial; Northern Hemisphere; ostracod; paleoclimate; sediment chemistry; semiarid region; shell; China; Qinghai; Qinghai Lake; Ostracoda

Laboratory study on ultra high temperature water base mud - Xu, Jie; Wu, Xiaoming; Zhu, Yongyi; Chikhotkin, V.F.; Xu, Mingbiao; Wu, Chuan; Zheng, Wenlong (Drilling Fluid and Completion Fluid, 2015)
A high temperature water base drilling fluid was formulated with sodium bentonite and attapulgite, and a high temperature water-in-oil stabilizer, MG-H2 which is synthesized through emulsion polymerization. Laboratory evaluation of the drilling fluid showed that, after aging at 240 °C, the drilling fluid still retained satisfactory rheology and filtration properties. It had good inhibitive capacity and was resistant to contamination caused by the introduction of 10% clay, or a combination of 5% NaCl and 1% CaCl2. It also had good lubricity at high temperature. The formulation of this high temperature drilling fluid lays the foundation for the formulation of an ultra-high temperature drilling fluid, say, 260 °C, for the drilling of the Well Songke-2.

Joint Inversion of Seismic and Magnetotelluric Data in the Parkfield Region of California Using the Normalized Cross-Gradient Constraint - Bennington, N.L.; Zhang, H.; Bedrosian, P.A. (Pure and Applied Geophysics, 2015)
We present jointly inverted models of P-wave velocity (Vp) and electrical resistivity for a two-dimensional profile centered on the San Andreas Fault Observatory at Depth (SAFOD). Significant structural similarity between main features of the separately inverted Vp and resistivity models is exploited by carrying out a joint inversion of the two datasets using the normalized cross-gradient constraint. This constraint favors structurally similar Vp and resistivity images that adequately fit the seismic and magnetotelluric (MT) datasets. The new inversion code, tomoDDMT, merges the seismic inversion code tomoDD and the forward modeling and sensitivity kernel subroutines of the MT inversion code OCCAM2DMT. TomoDDMT is tested on a synthetic dataset and demonstrates the code’s ability to more accurately resolve features of the input synthetic structure relative to the separately inverted resistivity and velocity models. Using tomoDDMT, we are able to resolve a number of key issues raised during drilling at SAFOD. We are able to infer the distribution of several geologic units including the Salinian granitoids, the Great Valley sequence, and the Franciscan Formation. The distribution and transport of fluids at both shallow and great depths is also examined. Low values of velocity/resistivity attributed to a feature known as the Eastern Conductor (EC) can be explained in two ways: the EC is a brine-filled, high porosity region, or this region is composed largely of clay-rich shales of the Franciscan. The Eastern Wall, which lies immediately adjacent to the EC, is unlikely to be a fluid pathway into the San Andreas Fault’s seismogenic zone due to its observed higher resistivity and velocity values. © 2014, Springer Basel.
cited By 41
Keywords: Codes (symbols); Magnetotellurics; Seismic waves; Seismographs; Strike-slip faults; Tectonics; Transport properties; Velocity; Wave propagation; Inverse theory; Joint inversion; Magnetotelluric data; Resistivity images; Seismic tomography; Sensitivity kernels; Structural similarity; Two-dimensional profiles; Seismology; data inversion; data set; electrical resistivity; gradient analysis; inverse analysis; magnetotelluric method; San Andreas Fault; seismic data; seismic tomography; seismic zone; velocity structure

Investigations related to scientific deep drilling to study reservoir-triggered earthquakes at Koyna, India - Gupta, H.; Purnachandra Rao, N.; Roy, S.; Arora, K.; Tiwari, V.M.; Patro, P.K.; Satyanarayana, H.V.S.; Shashidhar, D.; Mallika, K.; Akkiraju, V.V.; Goswami, D.; Vyas, D.; et al. (International Journal of Earth Sciences, 2015)
Artificial water reservoir-triggered earthquakes have continued at Koyna in the Deccan Traps province, India, since the impoundment of the Shivaji Sagar reservoir in 1962. Existing models, to comprehend the genesis of triggered earthquakes, suffer from lack of observations in the near field. To investigate further, scientific deep drilling and setting up a fault zone observatory at depth of 5 –7 km is planned in the Koyna area. Prior to undertaking deep drilling, an exploratory phase of investigations has been launched to constrain subsurface geology, structure and heat flow regime in the area that provide critical inputs for the design of the deep borehole observatory. Two core boreholes drilled to depths of 1,522 and 1,196 m have penetrated the Deccan Traps and sampled the granitic basement in the region for the first time. Studies on cores provide new and direct information regarding the thickness of the Deccan Traps, the absence of infra-Trappean sediments and the nature of the underlying basement rocks. Temperatures estimated at a depth of 6 km in the area, made on the basis of heat flow and thermal properties data sets, do not exceed 150 °C. Low-elevation airborne gravity gradient and magnetic data sets covering 5,012 line km, together with high-quality magnetotelluric data at 100 stations, provide both regional information about the thickness of the Deccan Traps and the occurrence of localized density heterogeneities and anomalous conductive zones in the vicinity of the hypocentral zone. Acquisition of airborne LiDAR data to obtain a high-resolution topographic model of the region has been completed over an area of 1,064 km2 centred on the Koyna seismic zone. Seismometers have been deployed in the granitic basement inside two boreholes and are planned in another set of six boreholes to obtain accurate hypocentral locations and constrain the disposition of fault zones. © 2014, Springer-Verlag Berlin Heidelberg.
cited By 69
Keywords: borehole; deep drilling; earthquake; earthquake hypocenter; fault zone; heat flow; lidar; reservoir; seismic zone; seismicity; trigger mechanism; Deccan; India; Koyna; Maharashtra; Calluna vulgaris

Investigating uncertainties in empirical green’s function analysis of earthquake source parameters - Abercrombie, R.E. (Journal of Geophysical Research: Solid Earth, 2015)
I use a well-recorded earthquake sequence to investigate the uncertainties of earthquake stress drops calculated using an empirical Green’s function (EGF) approach. The earthquakes in the largest (M 2.1) repeating sequence targeted by the San Andreas Observatory at Depth (SAFOD), Parkfield, California, are recorded by multiple borehole stations and have simple sources, well-constrained stress drops, and abundant smaller earthquakes to use as EGFs. I perform three tests to estimate quantitatively the likely uncertainties to arise in less optimal settings. I use EGF earthquakes with a range of cross-correlation values and separation distances fromthe main earthquakes. The stress dropmeasurements decrease by a factor of 3 as the quality of the EGF assumption decreases; a good EGF must be located within approximately one source dimension of the large earthquake, with high cross correlation. I subsample the large number ofmeasurements for the main earthquakes to investigate the expected stress drop uncertainties in studies where fewer stations or EGFs are available. If only one measurement is available, the uncertainties are likely to be at least 50%. The uncertainties decrease to <20% with five ormore measurements; usingmultiple EGFs is a good alternative to multiple stations. To investigate the effects of limited frequency bandwidth, I recalculate the corner frequencies after progressively decimating the sample rate. Decreasing the high-frequency limit of the bandwidth decreases the estimate of the corner frequency (and stress drop). The corner frequency may be underestimated if it is within a factor of 3 of the maximum frequency of the signal. © 2015. American Geophysical Union. All Rights Reserved.
cited By 109

Integrated geophysical and geological methods to investigate the inner and outer structures of the Quaternary M'ytina maar (W-Bohemia, Czech Republic) - Flechsig, Christina; Heinicke, Jens; Mrlina, Jan; K{ampf, Horst; Nickschick, Tobias; Schmidt, Alina; Bayer, Tom'aš; G{unther, Thomas; R{ucker, Carsten; Seidel, Elisabeth; Seidl, Michal (International Journal of Earth Sciences, 2015)
The M'ytina maar is the first known Quaternary maar in the Bohemian Massif. Based on the results of Mrlina et al. (J Volcanol Geother Res 182:97 –112, 2009), a multiparametric geophysical (electrical resistivity tomography, gravimetry, magnetometry, seismics) and geological/petrochemical research study had been carried out. The interpretation of the data has provided new information about the inner structure of the volcanic complex: (1) specification of the depth of post-volcanic sedimentary fill (up to 100 m) and (2) magnetic and resistivity signs of one (or two) hidden volcanic structures interpreted as intrusions or remains of a scoria cone. The findings at the outer structure of the maar incorporate the (1) evidence of circular fracture zones outside the maar, (2) detection and distribution of volcanic ejecta and tephra-fall deposits at the surface, and (3) indications from electrical resistivity tomography and gravity data in the area between the M'ytina maar and Železn'a hůrka scoria cone, interpreted as a palaeovalley, filled by volcaniclastic rocks, and aligned along the strike line (NW –SE) of the Tachov fault zone. These findings are valuable contributions to extend the knowledge about structure of maar volcanoes in general. Because of ongoing active magmatic processes in the north-east part of the Cheb Basin (ca. 15 –30 km north of the investigation area), the M'ytina maar-diatreme volcano and surroundings is a suitable key area for research directed to reconstruction of the palaeovolcanic evolution and assessment of possible future hazard potential in the Bohemian Massif. © 2015, Springer-Verlag Berlin Heidelberg.
Keywords: Bohemian Massif; Cheb Basin; Czech Republic; Karlovarsky; geological survey; geophysical survey; maar; Quaternary; reconstruction; volcanism

Initial seismic observations from a deep borehole drilled into the Canadian Shield in northeast Alberta - Chan, Judith; Schmitt, Douglas R. (International Journal of Earth Sciences, 2015)
The availability of a deep borehole in northeastern Alberta provides an unprecedented opportunity to study the in situ metamorphic craton rocks. This borehole reaches a depth of 2.4 km, with 1.8 km in the crystalline rocks, and is the only known borehole allowing access into the deeper rocks of the metamorphic Canadian Shield. In 2011, a zero-offset vertical seismic profile (VSP) was acquired to assist in the interpretation of seismic reflection data and geophysical logs. Three sets of upgoing tube waves interpreted from the raw profile correspond to the small-scale fluctuations in the borehole diameters and fracture zone in the crystalline rocks. A comparison between sonic log velocities and VSP velocities reveals a zone with increased velocity that could be due to the change in rock composition and texture in the basement rocks. The final processed profile is used to generate corridor stacks for differentiating between primary reflections and multiples in the seismic reflection profile. Analysis of the zero-offset VSP verifies existing log interpretation on the presence of fractures and the possible lithological changes in the metamorphic rocks of the Canadian Shield. © 2014, The Author(s).
Keywords: Alberta; Canada; Canadian Shield; borehole; craton; metamorphic rock; seismic reflection; seismic velocity; vertical seismic profile

Impact of paleoclimate on the distribution of microbial communities in the subsurface sediment of the Dead Sea - Thomas, C.; Ionescu, D.; Ariztegui, D.; team, The (Geobiology, 2015)
A long sedimentary core has been recently retrieved from the Dead Sea Basin (DSB) within the framework of the ICDP-sponsored Dead Sea Deep Drilling Project. Contrasting climatic intervals were evident by distinctive lithological facies such as laminated aragonitic muds and evaporites. A geomicrobiological investigation was conducted in representative sediments of this core. To identify the microbial assemblages present in the sediments and their evolution with changing depositional environments through time, the diversity of the 16S rRNA gene was analyzed in gypsum, aragonitic laminae, and halite samples. The subsurface microbial community was largely dominated by the Euryarchaeota phylum (Archaea). Within the latter, Halobacteriaceae members were ubiquitous, probably favored by their 'high salt-in' osmotic adaptation which also makes them one of the rare inhabitants of the modern Dead Sea. Bacterial community members were scarce, emphasizing that the 'low salt-in' strategy is less suitable in this environment. Substantial differences in assemblages are observed between aragonitic sediments and gypsum-halite ones, independently of the depth and salinity. The aragonite sample, deposited during humid periods when the lake was stratified, consists mostly of the archaeal MSBL1 and bacterial KB1 Candidate Divisions. This consortium probably relies on compatible solutes supplied from the lake by halotolerant species present in these more favorable periods. In contrast, members of the Halobacteriaceae were the sole habitants of the gypsum-halite sediments which result from a holomictic lake. Although the biomass is low, these variations in the observed subsurface microbial populations appear to be controlled by biological conditions in the water column at the time of sedimentation, and subsequently by the presence or absence of stratification and dilution in the lake. As the latter are controlled by climatic changes, our data suggest a relationship between local lacustrine subsurface microbial assemblages and large-scale climatic variations over the Dead Sea Basin. © 2015 John Wiley & Sons Ltd.
cited By 14
Keywords: climate variation; halite; lacustrine deposit; lithology; microbial community; paleoclimate; salinity; sediment core; sedimentation rate; Dead Sea; Archaea; Bacteria (microorganisms); Euryarchaeota; Halobacteriaceae; archaeal DNA; RNA 16S; salt water; archaeon; classification; climate; DNA sequence; Euryarchaeota; genetics; isolation and purification; Israel; Jordan; microbiology; molecular genetics; phylogeny; sediment; Archaea; Climate; DNA; Archaeal; Euryarchaeota; Geologic Sediments; Israel; Jordan; Molecular Sequence Data; Phylogeny; RNA; Ribosomal; 16S; Saline Waters; Sequence Analysis; DNA

Hydrological connectivity and mixing of Lake Towuti, Indonesia in response to paleoclimatic changes over the last 60,000 years - Costa, K.M.; Russell, J.M.; Vogel, H.; Bijaksana, S. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2015)
The Indo-Pacific Warm Pool (IPWP) is an important driver of global climate, but its response to and involvement in paleoclimate change is poorly constrained. We generated a new record of sediment geochemistry from Lake Towuti (2.5°S, 121.5°E), Indonesia, located in the heart of the IPWP, to investigate changes in hydrological connectivity with upstream lakes and the extent of lake mixing and oxygenation during paleoclimate changes over the last 60,000. years BP (60. ka). Lake Towuti is located at the downstream end of the Malili Lakes, a chain of large, ancient, and biologically diverse tectonic lakes occupying a geologically heterogeneous terrain in central Sulawesi, Indonesia. Major and trace element data from river and lake sediments suggest no changes in sediment provenance during the Last Glacial Maximum (LGM), indicating that some of the Malili Lakes remained hydrologically open despite a regionally drier climate. However, samples from the LGM are uniformly less enriched in trace elements than samples from the Holocene and Marine Isotope Stage 3 (MIS3), which suggests a decrease in weathering intensity during the LGM, likely in response to decreased precipitation and temperature. Changes in Fe and other redox-sensitive trace element concentrations indicate changes in water column oxygenation, with the highest oxygen availability occurring during the LGM (15-35. ka) likely due to more frequent and/or deeper mixing of Lake Towuti's water column. The glacial-interglacial trend in lake oxygenation corresponds with changes in regional precipitation and associated changes in the seasonal cycle. The high degree of faunal endemism in these lakes may be related to changes in the lake geochemistry associated with glacial-interglacial environmental variability driven by changing inputs and redox variability. © 2014 Elsevier B.V.
Keywords: Greater Sunda Islands; Lake Towuti; Malili Lakes; South Sulawesi; Sulawesi; Sunda Isles; climate variation; connectivity; glacial-interglacial cycle; mixing; oxygenation; paleoclimate; paleolimnology; provenance; seasonal variation; trace element

Interpretation of s waves generated by near-surface chemical explosions at SAFOD - Pollitz, F.F.; Ellsworth, W.; Rubinstein, J. (Bulletin of the Seismological Society of America, 2015)
A series of near-surface chemical explosions conducted at the San Andreas Fault Observatory at Depth (SAFOD) were recorded by high-frequency downhole receiver arrays in separate experiments in November 2003 and May 2005. The 2003 experiment involved 100 kg shots detonated along a 46-km-long line (Hole –Ryberg line) centered on SAFOD and recorded by 32 three-component geophones in the pilot hole between 0.8 and 2.0 km depth. The 2005 experiment involved 36 kg shots detonated at Parkfield Area Seismic Observatory (PASO) stations (at 1 –8 km offset) recorded by 80 three-component geophones in the main hole between the surface and 2.4 km depth. These data sample the downgoing seismic wavefield and constrain the shallow velocity and attenuation structure, as well as the first-order characteristics of the source. Using forward modeling on a velocity structure designed for the near field, both observed P- and S-wave energy for the PASO shots are identified with the travel times expected for direct and/or reflected phases. Larger-offset recordings from shots along the Hole –Ryberg line reveal substantial SVand SH energy, especially southwest of SAFOD from the source as indicated by P-to-S amplitude ratios. The generated SV energy is interpreted to arise chiefly from P-to-S conversions at subhorizontal discontinuities. This provides a simple mechanism for often-observed low P-to-S amplitude ratios from nuclear explosions in the far field, as originating from strong near-field wave conversions. © 2015, Seismological Society of America. All rights reserved.
cited By 0
Keywords: Explosions; Nuclear explosions; Observatories; Seismology; Strike-slip faults; Wave energy conversion; Amplitude ratios; Downhole receivers; Forward modeling; High frequency HF; Reflected phasis; San Andreas fault; Seismic wavefields; Velocity structure; Shear waves; explosion; geophone; S-wave; seismic discrimination; seismic velocity; wave generation; California; Parkfield; United States

Exogenic Dynamics, Cratering, and Surface Ages - Werner, S.C.; Ivanov, B.A. (Treatise on Geophysics: Second Edition, 2015)
Impact craters on terrestrial planets are key to studying planetary geology and geophysics as well as the planetary evolution remaining as geologic features at a planet's surface. To best use the cratering record history and interpret the planetary evolution, one needs to combine a wide set of processes and parameters. This chapter reviews impact cratering processes, estimates of average impact velocities, and impact probabilities for terrestrial planets. The basics of the impact crater scaling are outlined at an up-to-date level, describing the correlation of a measured impact crater diameter and the mass and size of a body that created the impact structure. Scaling laws for large impact craters are compared with the results of the direct numerical modeling of impact cratering.The accumulation rate for impact craters on terrestrial planets is univocally considered to be constant (within a factor of 2) during the youngest 3. Ga of the solar system history, while crater-forming projectile flux evolution for the very earliest phase is debated and relates to the preferred solar system evolution concept. The intermediate flux is constrained by observations from the Earth's Moon. Different cratering chronology models are described. Measuring the number of accumulated craters at predefined sizes in a geologically outlined area of interest, one can estimate the relative and model absolute ages of the visible surface, assuming older surfaces accumulate larger number of craters. Possible challenges for this technique and the interpretation of measured size-frequency distributions of impact craters are discussed, including secondary cratering, atmospheric breakup, geologic activity, and target properties, which all modify the cratering record. © 2015 Elsevier B.V. All rights reserved.
cited By 26

Hf and Nd isotope systematics of early Archean komatiites from surface sampling and ICDP drilling in the Barberton Greenstone Belt, South Africa - Blichert-Toft, Janne; Arndt, Nicholas T.; Wilson, Allan; Coetzee, Grace (American Mineralogist, 2015)
To constrain the origin of komatiites from the Barberton Greenstone Belt, South Africa, we measured 147Sm-143Nd and 176Lu-176Hf compositions for 18 komatiites from core obtained during the International Continental Drilling Program in the Komati Formation of the Barberton Belt, as well as 33 komatiites from surface outcrops of the Komati, Hooggenoeg, and Weltevreden Formations, these latter for purposes of comparison between core and surface samples. Magmatic clinopyroxene from surface samples near the drill site was also analyzed. For the Lu-Hf isotope system, the Komati Formation core and surface samples including the clinopyroxene define a linear array whose slope corresponds to an age of 3426 ± 16 Ma (MSWD = 118; εHf(T) = +2.2), which is slightly younger than the accepted age of the rocks (3.48 Ga). The Sm-Nd isotope data for the same set of samples likewise fall along a linear array also yielding a younger age of 3339 ± 12 Ma (MSWD = 42; εNd(T) = +2.8). The high MSWD for both isotope systems indicate substantial scatter at variance with normal magmatic processes, likely implying element mobility disturbing even these relatively robust isotopic systems shortly after eruption of the lavas. The average initial εNd and εHf of the core samples at 3.48 Ga are +0.45 and +1.4, respectively, in overall accordance with the positive errorchron intercepts and a depleted mantle source at 3.5 Ga. In contrast, the clinopyroxene and their host rocks have strongly positive εHf(T) of about +5 and negative εNd(T) of about -2. Given the overall scatter of the whole-rock data, the most robust constraint on the composition of the komatiite source comes from the clinopyroxene. Their positive εHf(T) is in line with, though somewhat higher than other results from komatiites from the Komati Formation, but their negative εNd(T) is unexpected in that it indicates a source with long-term low Sm/Nd, which is at odds with its long-term high Lu/Hf. This signature is also found in the trace element compositions of some of the komatiites, such as moderately enriched LREE, negative Hf anomalies, and low Hf/Sm ratios. The origin of these features is uncertain but one possibility is that the discordance between the Hf and Nd isotope systems reflects the presence of deepsea sediments in the source of some of the Barberton komatiites. The possible presence of a surface component in an ancient deep mantle source has wide-ranging implications for mantle-crust interaction and dynamics in the early Earth and for constraining a minimum age for the onset of plate tectonics. © Walter de Gruyter Berlin/Boston 2015.
Keywords: Barberton Greenstone Belt; Binary alloys; Core samples; Gallium alloys; Hafnium; Infill drilling; Isotopes; Lutetium alloys; Neodymium; Samarium alloys; Trace elements; chert; Clinopyroxenes; Deep sea sediment; Greenstone belts; Hf isotope; International Continental Drilling Program; Invited Centennial article; Komatiites; Sm-Nd isotope; Archean; chert; clinopyroxene; deep-sea sediment; drilling; hafnium; isotopic composition; komatiite; neodymium; research program; Neodymium alloys

Geophysical studies of the upper crust of the central Swedish Caledonides in relation to the COSC scientific drilling project - Hedin, Peter (Uppsala University, 2015)
The Collisional Orogeny in the Scandinavian Caledonides (COSC) project aims to provide a deeper understanding of mountain belt dynamics through scientific deep drilling in the central parts of the ...

Geochemical studies of impact breccias and country rocks from the El'gygytgyn impact structure, Russia - Raschke, U.; Schmitt, R.T.; Mcdonald, I.; Reimold, W.U.; Mader, D.; Koeberl, C. (Meteoritics and Planetary Science, 2015)
The complex impact structure El'gygytgyn (age 3.6 Ma, diameter 18 km) in northeastern Russia was formed in 88 Ma old volcanic target rocks of the Ochotsk-Chukotsky Volcanic Belt (OCVB). In 2009, El'gygytgyn was the target of a drilling project of the International Continental Scientific Drilling Program (ICDP), and in summer 2011 it was investigated further by a Russian-German expedition. Drill core material and surface samples, including volcanic target rocks and impactites, have been investigated by various geochemical techniques in order to improve the record of trace element characteristics for these lithologies and to attempt to detect and constrain a possible meteoritic component. The bedrock units of the ICDP drill core reflect the felsic volcanics that are predominant in the crater vicinity. The overlying suevites comprise a mixture of all currently known target lithologies, dominated by felsic rocks but lacking a discernable meteoritic component based on platinum group element abundances. The reworked suevite, directly overlain by lake sediments, is not only comparatively enriched in shocked minerals and impact glass spherules, but also contains the highest concentrations of Os, Ir, Ru, and Rh compared to other El'gygytgyn impactites. This is-to a lesser extent-the result of admixture of a mafic component, but more likely the signature of a chondritic meteoritic component. However, the highly siderophile element contribution from target material akin to the mafic blocks of the ICDP drill core to the impactites remains poorly constrained. © The Meteoritical Society, 2015.
cited By 3

Further quantifying the fluxes and contributions of sources to modern sediment in Lake Qinghai, NE Tibetan Plateau - Wan, Dejun; Jin, Zhangdong; Zhang, Fei; Chen, Hongyun; Chen, Liumei; Song, Lei; Song, Chao (Limnology, 2015)
Faithfully tracing sources of sediment and then quantifying the flux of each source are the first-order basis for reconstructing paleoclimate and paleoenvironment using lake sediments. The budget of various sources contributing to lake sediment in Lake Qinghai, the largest lake on the Tibetan Plateau, is controversial. In the previous study, the flux of the dust deposition to the modern lake sediment was obtained through 2-year observations, but estimations of other sources have some uncertainties due to inadequate data. In this study our new estimations for the modern Lake Qinghai sediment using new measured data show (1) that contribution (22.1 ± 5.2 %) of the fluvial particulate matter is of second significance, only about one-third of the dust deposition, to the modern lake sediment, when its quick deposition near river mouths is not considered, (2) that lacustrine organisms contribute only 5.2 ± 1.1 % of the sediment, but account for 70 % of the organic matter in sediment, and (3) that authigenic carbonates contribute 21.0 ± 8.6 % of the sediment and 63.6 % of the total carbonates in the lake sediment, respectively, which is due to a direct precipitation of both Ca2+ and Mg2+ in the modern Ca2+-limited lake. These quantifications are instructive to understand the particulate fluxes to sediment pools in Lake Qinghai under the present conditions and to reconstruct paleoclimate and paleoenvironment via physical and geochemical proxies using past sediments. © 2014, The Japanese Society of Limnology.

From mantle roots to surface eruptions: Cenozoic and Mesozoic continental basaltic magmatism - K{ampf, Horst; N'emeth, Karoly; Puziewicz, Jacek; Mrlina, Jan; Geissler, Wolfram H. (International Journal of Earth Sciences, 2015)

Frictional properties of the active San Andreas Fault at SAFOD: Implications for fault strength and slip behavior - Carpenter, B.M.; Saffer, D.M.; Marone, C. (Journal of Geophysical Research: Solid Earth, 2015)
We present results from a comprehensive laboratory study of the frictional strength and constitutive properties for all three active strands of the San Andreas Fault penetrated in the San Andreas Observatory at Depth (SAFOD). The SAFOD borehole penetrated the Southwest Deforming Zone (SDZ), the Central Deforming Zone (CDZ), both of which are actively creeping, and the Northeast Boundary Fault (NBF). Our results include measurements of the frictional properties of cuttings and core samples recovered at depths of 2.7 km. We find that materials from the two actively creeping faults exhibit low frictional strengths (μ = 0.1), velocity-strengthening friction behavior, and near-zero or negative rates of frictional healing. Our experimental data set shows that the center of the CDZ is the weakest section of the San Andreas Fault, with μ = 0.10. Fault weakness is highly localized and likely caused by abundant magnesium-rich clays. In contrast, serpentine from within the SDZ, and wall rock of both the SDZ and CDZ, exhibits velocity-weakening friction behavior and positive healing rates, consistent with nearby repeating microearthquakes. Finally, we document higher friction coefficients (μ > 0.4) and complex rate-dependent behavior for samples recovered across the NBF. In total, our data provide an integrated view of fault behavior for the three active fault strands encountered at SAFOD and offer a consistent explanation for observations of creep and microearthquakes along weak fault zones within a strong crust. ©2015. American Geophysical Union. All Rights Reserved.
cited By 64
Keywords: active fault; creep; fault slip; fault zone; friction; microearthquake; San Andreas Fault; California; San Andreas; United States

Erratum to Orogenic paleofluid flow recorded by discordant detrital zircons in the Caledonian foreland basin of northern Greenland [Lithosphere, 7, 2, (2015), 138-143] DOI: 10.1130/L420.1 - Morris, G.A.; Kirkland, C.L.; Pease, V. (Lithosphere, 2015)
cited By 0
Keywords: Caledonian orogeny; detrital deposit; foreland basin; geochronology; lithosphere; lithostratigraphy; orogenic belt; zircon; Arctic; Greenland

Fluid inclusion analysis of silicified Palaeoarchaean oceanic crust - A record of Archaean seawater? - Farber, Katja; Dziggel, Annika; Meyer, F. Michael; Prochaska, Walter; Hofmann, Axel; Harris, Chris (Precambrian Research, 2015)
In recent years, the role of Archaean seawater and hydrothermal fluid in the extensive silicification of Palaeoarchaean volcano-sedimentary successions has been a matter of considerable debate. In an attempt to constrain the conditions of silica precipitation, and the sources and chemical composition of the interacting fluids, we used fluid inclusion microthermometry, bulk crush-leach and oxygen isotope analyses of chert and quartz veins in silicified komatiites and sediments from the Barberton greenstone belt, South Africa. Chert vein margins consist of microcrystalline quartz and carbonaceous matter, whereas the vein centres are often filled with macrocrystalline quartz that contains abundant fluid inclusions.Oxygen isotope ratios of vein chert and macrocrystalline quartz vary from 18 to 21‰, with the macrocrystalline quartz having slightly higher δ18O values (0.7±0.3‰). The data are consistent with silica precipitation during low-temperature (≤100°C) hydrothermal processes on the Archaean seafloor. Macrocrystalline quartz contains homogeneous 2-phase (L+V) inclusions at room temperature with a relatively constant vapour fraction. The inclusions have a salinity of 3-11wt.% NaCl equiv. and homogenisation temperatures (Th) of 150-200°C. Whereas some of the inclusions form intragranular fluid inclusion clusters that appear to be primary, other inclusions form transgranular fluid inclusion trails and are clearly secondary. Both types of inclusions share the same microthermometric characteristics, indicating that fluid entrapment occurred during a later metamorphic event and not near the seafloor. The event likely coincided with regional deformation and metamorphism at 3.23Ga. Chlorite thermometry from vein host rocks reveals peak conditions of 257±31°C. In conjunction with microthermometry, the data correspond to a crustal depth of 3-6km. A secondary origin of fluid inclusions is also consistent with the Cl/Br, Na/Cl and Na/K ratios of the macrocrystalline veins, which are similar to those found in metamorphic quartz veins. The fluid inclusions thus do not provide information on the conditions and temperatures during chert formation. While the fluids potentially carry the geochemical signature of modified Archaean seawater (i.e. hydrothermal fluid), characterised by low Cl/Br and Na/K ratios, and low Mg-contents, the fluid composition was likely modified during regional metamorphism. © 2015 Elsevier B.V.
Keywords: Barberton Greenstone Belt; Archean; chert; deformation mechanism; fluid inclusion; hydrothermal alteration; hydrothermal fluid; isotopic ratio; oceanic crust; oxygen isotope; paleoceanography; quartz vein; seawater; silicification

Fault Zone Guided Wave generation on the locked, late interseismic Alpine Fault, New Zealand - Eccles, J.D.; Gulley, A.K.; Malin, P.E.; Boese, C.M.; Townend, J.; Sutherland, R. (Geophysical Research Letters, 2015)
Fault Zone Guided Waves (FZGWs) have been observed for the first time within New Zealand's transpressional continental plate boundary, the Alpine Fault, which is late in its typical seismic cycle. Ongoing study of these phases provides the opportunity to monitor interseismic conditions in the fault zone. Distinctive dispersive seismic codas ( 7-35Hz) have been recorded on shallow borehole seismometers installed within 20m of the principal slip zone. Near the central Alpine Fault, known for low background seismicity, FZGW-generating microseismic events are located beyond the catchment-scale partitioning of the fault indicating lateral connectivity of the low-velocity zone immediately below the near-surface segmentation. Initial modeling of the low-velocity zone indicates a waveguide width of 60-200m with a 10-40% reduction in S wave velocity, similar to that inferred for the fault core of other mature plate boundary faults such as the San Andreas and North Anatolian Faults. © 2015. American Geophysical Union. All Rights Reserved.
cited By 28
Keywords: Catchments; Guided electromagnetic wave propagation; Seismology; Shear waves; Alpine Faults; Drilling projects; Fault zone; Low velocity zones; Microseismic events; North Anatolian Fault; Shallow boreholes; Waveguide widths; Faulting; catchment; fault zone; plate boundary; S-wave; segmentation; seismograph; seismology; slip; slip rate; Anatolia; California; New Zealand; San Andreas; Turkey; United States

Fault rock lithologies and architecture of the central Alpine fault, New Zealand, revealed by DFDP-1 drilling - Toy, V.G.; Boulton, C.J.; Sutherland, R.; Townend, J.; Norris, R.J.; Little, T.A.; Prior, D.J.; Mariani, E.; Faulkner, D.; Menzies, C.D.; Scott, H.; Carpenter, B.M. (Lithosphere, 2015)
The first phase of the Deep Fault Drilling Project (DFDP-1) yielded a continuous lithological transect through fault rock surrounding the Alpine fault (South Island, New Zealand). This allowed micrometer-to decimeter-scale variations in fault rock lithology and structure to be delineated on either side of two principal slip zones intersected by DFDP-1A and DFDP-1B. Here, we provide a comprehensive analysis of fault rock lithologies within 70 m of the Alpine fault based on analysis of hand specimens and detailed petrographic and petrologic analysis. The sequence of fault rock lithologies is consistent with that inferred previously from outcrop observations, but the continuous section afforded by DFDP-1 permits new insight into the spatial and genetic relationships between different lithologies and structures. We identify principal slip zone gouge, and cataclasite-series rocks, formed by multiple increments of shear deformation at up to coseismic slip rates. A 20-30-m-thick package of these rocks (including the principal slip zone) forms the fault core, which has accommodated most of the brittle shear displacement. This deformation has overprinted ultramylonites deformed mostly by grain-size-insensitive dislocation creep. Outside the fault core, ultramylonites contain low-displacement brittle fractures that are part of the fault damage zone. Fault rocks presently found in the hanging wall of the Alpine fault are inferred to have been derived from protoliths on both sides of the present-day principal slip zone, specifically the hanging-wall Alpine Schist and footwall Greenland Group. This implies that, at seismogenic depths, the Alpine fault is either a single zone of focused brittle shear that moves laterally over time, or it consists of multiple strands. Ultramylonites, cataclasites, and fault gouge represent distinct zones into which deformation has localized, but within the brittle regime, particularly, it is not clear whether this localization accompanies reductions in pressure and temperature during exhumation or whether it occurs throughout the seismogenic regime. These two contrasting possibilities should be a focus of future studies of fault zone architecture. © 2015 Geological Society of America.
cited By 65
Keywords: Brittle fracture; Creep; Lithology; Rock drilling; Rocks; Comprehensive analysis; Fault zone architecture; Genetic relationships; Grain size insensitive dislocation creeps; Pressure and temperature; Seismogenic regimes; Shear displacement; South Island; New Zealand; Structural geology; alpine environment; cataclasite; deep drilling; fault zone; lithology; outcrop; petrography; Alpine Fault Zone; New Zealand; South Island

Evidence of extensive carbonate mounds and sublacustrine channels in shallow waters of Lake Van, eastern Turkey, based on high-resolution chirp subbottom profiler and multibeam echosounder data - Cukur, D.; Krastel, S.; Çağatay, M.N.; Damcı, E.; Meydan, A.F.; Kim, S.-P. (Geo-Marine Letters, 2015)
In Lake Van of eastern Turkey, the fourth largest soda lake in the world, high-resolution subbottom profiles and bathymetric data acquired in 2004 and 2012 revealed several hundreds of topographic mounds in shallow waters (<130 m) off the historical town of Adilcevaz in the northern lake sector. These structures are characterized by strong top reflections of transparent internal character, and are 10 –300 m wide and 0.5 –20 m high. Consistent with previous work, they are interpreted as carbonate mounds formed by precipitation from CO2-rich groundwater discharge into the highly alkaline lake. Their age remains to be determined but their alignment along faults suggests tectonic control on their growth. Several sublacustrine channel networks were observed on the eastern shelf of the lake, which connects with onshore rivers. The channels are up to 500 m wide and 20 m deep, and plausibly were formed by fluvial processes during the major lake level drop reported to have occurred by 14 ka in earlier publications. Erosion is common on the channel walls flanked by levees. The channels are presently inactive or abandoned. At a water depth of 100 m, they all merge into a single larger channel; this channel has a sinuous course initially trending southwestward and then northwestward at a water depth of 130 m. Numerous closely spaced small channels ( 10 –200 m wide, 1 –10 m deep) are also seen on the eastern lacustrine shelf, interpreted as denditric and parallel channel systems formed during lake level fall terminating at 14 ka. Bathymetric data provide evidence of numerous sublacustrine canyons on the western slope of the lake’s northern basin, most likely remnants of relict rivers formed during this lowstand. © 2015, Springer-Verlag Berlin Heidelberg.
cited By 18
Keywords: Bathymetry; Channel flow; Groundwater; Hydrographic surveys; Bathymetric data; Carbonate mounds; Chirp sub bottoms; Ground water discharge; Multibeam echo sounder; Parallel channel; Sub-bottom profiles; Tectonic control; Lakes; carbonate platform; fluvial process; lacustrine environment; levee; multibeam sonar; profiler; shallow water; Lake Van; Turkey

Evolution of fluid-rock interaction in the Reykjanes geothermal system, Iceland: Evidence from Iceland Deep Drilling Project core RN-17B - Fowler, A.P.G.; Zierenberg, R.A.; Schiffman, P.; Marks, N.; Frileifsson, G.O. (Journal of Volcanology and Geothermal Research, 2015)
We describe the lithology and present spatially resolved geochemical analyses of samples from the hydrothermally altered Iceland Deep Drilling Project (IDDP) drill core RN-17B. The 9.3m long RN-17B core was collected from the seawater-dominated Reykjanes geothermal system, located on the Reykjanes Peninsula, Iceland. The nature of fluids and the location of the Reykjanes geothermal system make it a useful analog for seafloor hydrothermal processes, although there are important differences. The recovery of drill core from the Reykjanes geothermal system, as opposed to drill cuttings, has provided the opportunity to investigate evolving geothermal conditions by utilizing in-situ geochemical techniques in the context of observed paragenetic and spatial relationships of alteration minerals. The RN-17B core was returned from a vertical depth of 2560m and an in-situ temperature of 345°C. The primary lithologies are basaltic in composition and include hyaloclastite breccia, fine-grained volcanic sandstone, lithic breccia, and crystalline basalt. Primary igneous phases have been entirely pseudomorphed by calcic plagioclase+magnesium hornblende+chlorite+titanite+albitized plagioclase+vein epidote and sulfides. Despite the extensive hydrothermal metasomatism, original textures including hyaloclastite glass shards, lithic clasts, chilled margins, and shell-fragment molds are superbly preserved. Multi-collector LA-ICP-MS strontium isotope ratio (87Sr/86Sr) measurements of vein epidote from the core are consistent with seawater as the dominant recharge fluid. Epidote-hosted fluid inclusion homogenization temperature and freezing point depression measurements suggest that the RN-17B core records cooling through the two-phase boundary for seawater over time to current in-situ measured temperatures. Electron microprobe analyses of hydrothermal hornblende and hydrothermal plagioclase confirm that while alteration is of amphibolite-grade, it is in disequilibrium and the extent of alteration is dependent upon protolith type and water/rock ratio. Alteration in the RN-17B core bares many similarities to that of Type II basalts observed in Mid-Atlantic Ridge samples. © 2015 Elsevier B.V.
cited By 15
Keywords: Analytical geochemistry; Basalt; Core drilling; Drills; Electron probe microanalysis; Feldspar; Geochemistry; Geothermal fields; Isotopes; Lithology; Microanalysis; Mineralogy; Rock drilling; Rocks; Seawater; Silicate minerals; Strontium; Drill core; Epidote; Geothermal; Hydrothermal alterations; Icelands; Reykjanes; Core samples; deep drilling; epidote; geochemistry; geothermal system; hydrothermal alteration; lithology; paragenesis; seawater; Iceland; Reykjanes Peninsula

Evidences for centennial dry periods at 3300 and 2800 cal. yr BP from micro-facies analyses of the Dead Sea sediments - Neugebauer, I.; Brauer, A.; Schwab, M.J.; Dulski, P.; Frank, U.; Hadzhiivanova, E.; Kitagawa, H.; Litt, T.; Schiebel, V.; Taha, N.; Waldmann, N.D. (Holocene, 2015)
Laminated lake sediments from the Dead Sea basin provide high-resolution records of climatic variability in the eastern Mediterranean region, which is especially sensitive to changing climatic conditions. In this study, we aim on detailed reconstruction of climatic fluctuations and related changes in the frequency of flood and dust deposition events at ca. 3300 and especially at 2800 cal. yr BP from high-resolution sediment records of the Dead Sea basin. A ca. 4-m-thick, mostly varved sediment section from the western margin of the Dead Sea (DSEn – Ein Gedi profile) was analysed and correlated to the new International Continental Scientific Drilling Program (ICDP) Dead Sea Deep Drilling Project core 5017-1 from the deep basin. To detect even single event layers, we applied a multi-proxy approach of high-resolution microscopic thin section analyses, micro-X-ray fluorescence (µ-XRF) element scanning and magnetic susceptibility measurements, supported by grain size data and palynological analyses. Based on radiocarbon and varve dating, two pronounced dry periods were detected at 3500 –3300 and 3000 –2400 cal. yr BP which are differently expressed in the sediment records. In the shallow-water core (DSEn), the older dry period is characterised by a thick sand deposit, whereas the sedimentological change at 2800 cal. yr BP is less pronounced and characterised mainly by an enhanced frequency of coarse detrital layers interpreted as erosion events. In the 5017-1 deep-basin core, both dry periods are depicted by halite deposits. The onset of the younger dry period coincides with the Homeric Grand Solar Minimum at ca. 2800 cal. yr BP. Our results suggest that during this period, the Dead Sea region experienced an overall dry climate, superimposed by an increased occurrence of flash floods caused by a change in synoptic weather patterns. © The Author(s) 2015.
cited By 43
Keywords: dust; extreme event; flash flood; Holocene; lacustrine deposit; marine sediment; microfacies; paleoclimate; palynology; temporal period; varve; Dead Sea; Mediterranean Region

The snake geothermal drilling project. Innovative approaches to geothermal exploration - Shervais, John W.; Evans, James P.; Liberty, Lee M.; Blackwell, David D. (Report to Department of Energy Geothermal Technology Office, 2014)

New thermal data and challenges of heat flow variations evaluation for basin petroleum exploration - Popov, Yu.; Popov, E.; Miklashevskiy, D.; Korobkov, D. (Society of Petroleum Engineers - International Petroleum Technology Conference 2014, IPTC 2014 - Innovation and Collaboration: Keys to Affordable Energy, 2014)
The present work summarizes the results of analysis of unique experimental data on vertical heat flow variations in different geological structures obtained from 15 scientific supper-deep and deep boreholes drilled to the depths of 1600-12 262 m within Russian and ICDP programs. The new workflow was applied for the heat flow estimation which is based on (1) precise and detailed thermal conductivity measurements on more than 30 000 cores with the new emerging technologies, (2) usage of more than 100 equilibrium and non-equilibrium temperature logs, and (3) determination of conductive heat flow component within 20-100 m intervals along every borehole studied. The data on conductive heat flow variations provides an estimate of vertical variations in the convective heat flow component. The latter reflects the information on variations in reservoir and formation properties and heat- and mass transfer processes in reservoirs and formations. It was established that a conductive component of the heat flow varies between 70 and 100% for the boreholes studied with essential (up to 100%) increase in heat flow within upper depth intervals of 2-4 km in some cases. Terrestrial heat flow values established from the measurements in deep and super-deep boreholes exceed the previous experimental heat flow estimates by 30...130% depending on a region of drilling. During the previous estimates the heat flow values were obtained from the measurements in shallow boreholes and heat flow was determined from averaging temperature gradient and thermal conductivity along boreholes. The established heat flow variations play an important role in the improvement of reliability of basin and petroleum system modeling and prediction of temperatures below the borehole depths. The use of calibrated heat flow distributions is shown to increase the confidence of such studies. Copyright © 2014, International Petroleum Technology Conference.
cited By 1