Total organic carbon isotopes: A novel proxy of lake level from Lake Qinghai in the Qinghai-Tibet Plateau, China - Liu, Weiguo; Li, Xiangzhong; An, ZhiSheng; Xu, Liming (Chemical Geology, 2013)
The isotopic compositions of total organic carbon (TOC) in lakes have been widely used to interpret paleoclimatic changes and the depositional environments of lake sediments. However, the main factors that affect the carbon isotopes of TOC (source of organic material, water condition and others) may vary in different lake sediment records, which have limited the applicability of organic carbon isotopes in explaining biogeochemical and environmental changes in lakes. In this study, the organic carbon isotopic compositions of aquatic plants and surface sediments from Lake Qinghai and the living terrestrial plants and surface soils around the lake were systematically investigated to identify the sources of TOC in the sediments and the significance of the organic carbon isotopes of sedimentary TOC. We found that the aquatic plants in the deep water areas (>10m) were primarily dominated by Cladophora, but submerged plants (Potamogeton and Ruppia L.) are the dominant species in shallow water (<10m). The Cladophora have negative δ13Corg values (-33.6‰ to -28.6‰) that are caused by C3-like photosynthesis, but the submerged plants have enriched δ13Corg values (-17.8‰ to -15.4‰) that are caused by C4-like photosynthesis. In addition, the δ13Corg values of Cladophora become more negative with increasing water depth because of the slow photosynthetic rate caused by the weak light intensity at depth. The isotopic data indicate that the carbon isotopes of organic material in the surface sediments are primarily controlled by the types of aquatic plant and that the δ13Corg values of TOC can be used to indicate the variation of the water depth (lake level). The organic carbon isotopic data from the 1F core showed that the water was shallow (<10m) because of intense evaporation related to high temperatures even though precipitation sharply increased in the warm period during the early-mid Holocene. The lake level reached its maximum level at 3ka. © 2013 Elsevier B.V.
Keywords: China; Qinghai; Qinghai Lake; Qinghai-Xizang Plateau; Cladophora; Potamogeton; Ruppia; Carbon; Isotopes; Organic carbon; Photosynthesis; Sedimentology; Slow light; Surficial sediments; Carbon isotopic composition; Depositional environment; Isotopic composition; Lake levels; Lake Qinghai; Lake-sediment records; Qinghai Tibet plateau; Total Organic Carbon; carbon isotope; environmental change; green alga; isotopic composition; lacustrine deposit; lake level; precipitation (chemistry); sediment chemistry; total organic carbon; water depth; Lakes

Towards a late Quaternary tephrochronological framework for the southernmost part of South America - the Laguna Potrok Aike tephra record - Wastegård, S.; Veres, D.; Kliem, P.; Hahn, A.; Ohlendorf, C.; Zolitschka, B. (Quaternary Science Reviews, 2013)
A total of 18 tephra samples have been analysed from the composite sediment sequence from Site 2 of the Laguna Potrok Aike ICDP expedition 5022 from southern Patagonia, Argentina, which extends back to ca 51kacalBP. Analyses of the volcanic glass show that all layers but one are rhyolitic in composition, with SiO2 contents ranging between ca 74.5 and 78wt% and suggest an origin in the Austral Andean Volcanic Zone (AVZ; 49-55°S). Nonetheless, two main data clusters occur, one group with K2O contents between ca 1.5 and 2.0wt%, indicating an origin in the Mt. Burney volcanic area, and one group with K2O contents between ca 2.7 and 3.9wt%, tentatively correlated with Viedma/Lautaro and the Aguilera volcanoes in the northern part of the AVZ. The early Holocene Tephra, MB1 and the late Pleistocene Reclus R1 tephra occur in the upper part of the sequence. Periods with significant tephra deposition occurred between ca 51-44kacalBP, and ca 31-25kacalBP, with a decrease in tephra layer frequency between these two periods. © 2012 Elsevier Ltd.
Keywords: Argentina; Laguna Potrok Aike; Santa Cruz [Argentina]; Geology; Natural sciences; Chronology; ICDP-project PASADO; Mt. Burney; Pleistocene; Tephra; Volcanic; community composition; oxide; Quaternary; sediment analysis; tephrochronology; volcanic eruption; Volcanoes

Tracking lateral δ13Ccarb variation in the Paleoproterozoic Pechenga Greenstone Belt, the north eastern Fennoscandian Shield - Salminen, Paula E; Karhu, Juha A; Melezhik, Victor A (Precambrian Research, 2013)

Tracking lateral δ13Ccarb variation in the Paleoproterozoic Pechenga Greenstone Belt, the north eastern Fennoscandian Shield - Salminen, Paula E.; Karhu, Juha A.; Melezhik, Victor A. (Precambrian Research, 2013)

Understanding past climatic and hydrological variability in the mediterranean from Lake Prespa sediment isotope and geochemical record over the last glacial cycle - Leng, Melanie J.; Wagner, Bernd; Boehm, Anne; Panagiotopoulos, Konstantinos; Vane, Christopher H.; Snelling, Andrea; Haidon, Cheryl; Woodley, Ewan; Vogel, Hendrik; Zanchetta, Gianni; Baneschi, Ilaria (Quaternary Science Reviews, 2013)
Here we present stable isotope and geochemical data from Lake Prespa (Macedonia/Albania border) over the Last Glacial cycle (Marine Isotope Stages 5e1) and discuss past lake hydrology and climate (TIC, oxygen and carbon isotopes), as well as responses to climate of terrestrial and aquatic vegetation (TOC, Rock Eval pyrolysis, carbon isotopes, pollen). The Lake Prespa sediments broadly fall into 5 zones based on their sedimentology, geochemistry, palynology and the existing chronology. The Glacial sediments suggest low supply of carbon to the lake, but high summer productivity; intermittent siderite layers suggest that although the lake was likely to have mixed regularly leading to enhanced oxidation of organic matter, there must have been within sediment reducing conditions and methanogenesis. MIS 5 and 1 sediments suggest much more productivity, higher rates of organic material preservation possibly due to more limited mixing with longer periods of oxygen-depleted bottom waters. We also calculated lakewater d18O from siderite (authigenic/Glacial) and calcite (endogenic/Holocene) and show much lower lakewater d18O values in the Glacial when compared to the Holocene, suggesting the lake was less evaporative in the Glacial, probably as a consequence of cooler summers and longer winter ice cover. In the Holocene the oxygen isotope data suggests general humidity, with just 2 marked arid phases, features observed in other Eastern and Central Mediterranean lakes. © 2012 Elsevier Ltd.
Keywords: Albania; Lake Mikri Prespa; Macedonia [Southern Europe]; Geochemistry; Glacial geology; Iron ores; Isotopes; Oxygen; Productivity; Pyrolysis; Sediments; Central Mediterranean; Hydrological variability; Late quaternary; Marine isotope stages; Mediterranean; Reducing conditions; Rock-Eval pyrolysis; Stable isotopes; bottom water; climate effect; hydrological change; lacustrine deposit; lake water; Last Glacial; marine isotope stage; Mediterranean environment; methanogenesis; oxidation; oxygen isotope; paleoclimate; paleoecology; paleohydrology; palynology; preservation; pyrolysis; stable isotope; Lakes

Vegetation responses to interglacial warming in the Arctic: examples from Lake El'gygytgyn, Far East Russian Arctic - Lozhkin, A. V.; Anderson, P. M. (Climate of the Past, 2013)
Preliminary analyses of Lake El'gygytgyn sediment indicate a wide range of ecosystem responses to warmer than present climates. While palynological work describing all interglacial vegetation is ongoing, sufficient data exist to compare recent warm events (the postglacial thermal maximum, PGTM, and marine isotope stage, MIS5) with super interglaciations (MIS11, MIS31). Palynological assemblages associated with these climatic optima suggest two types of vegetation responses: one dominated by deciduous taxa (PGTM, MIS5) and the second by evergreen conifers (MIS11, MIS31). MIS11 forests show a similarity to modern Picea-Larix-Betula-Alnus forests of Siberia. While dark coniferous forest also characterizes MIS31, the pollen taxa show an affinity to the boreal forest of the lower Amur valley (southern Russian Far East). Despite vegetation differences during these thermal maxima, all glacial-interglacial transitions are alike, being dominated by deciduous woody taxa. Initially Betula shrub tundra established and was replaced by tundra with tree-sized shrubs (PGTM), Betula woodland (MIS5), or Betula-Larix (MIS11, MIS31) forest. The consistent occurrence of deciduous forest and/or high shrub tundra before the incidence of maximum warmth underscores the importance of this biome for modeling efforts. The El'gygytgyn data also suggest a possible elimination or massive reduction of Arctic plant communities under extreme warm-earth scenarios. © Author(s) 2013.
cited By 25
Keywords: arctic environment; community response; coniferous tree; deciduous tree; dominance; evergreen tree; glacial-interglacial cycle; interglacial; lacustrine deposit; marine isotope stage; paleoecology; palynology; plant community; shrub; tundra; vegetation structure; warming; Arctic; Chukchi; Elgygytgyn Lake; Russian Federation

Velocity ratio variations in the source region of earthquake swarms in NW bohemia obtained from arrival time double-differences - Dahm, Torsten; Fischer, Tom'aš (Geophysical Journal International, 2013)
Crustal earthquake swarms are an expression of intensive cracking and rock damaging over periods of days, weeks or month in a small source region in the crust. They are caused by longer lasting stress changes in the source region. Often, the localized stressing of the crust is associated with fluid or gas migration, possibly in combination with pre-existing zones of weaknesses. However, verifying and quantifying localized fluid movement at depth remains difficult since the area affected is small and geophysical prospecting methods often cannot reach the required resolution. We apply a simple and robust method to estimate the velocity ratio between compressional (P) and shear (S) waves (vP/vS-ratio) in the source region of an earthquake swarm. The vP/vP-ratio may be unusual small if the swarm is related to gas in a porous or fractured rock. The method uses arrival time difference between P and S waves observed at surface seismic stations, and the associated double differences between pairs of earthquakes. An advantage is that earthquake locations are not required and the method seems lesser dependent on unknown velocity variations in the crust outside the source region. It is, thus, suited for monitoring purposes. Applications comprise three natural, mid-crustal (8-10 km) earthquake swarms between 1997 and 2008 from the NW-Bohemia swarm region. We resolve a strong temporal decrease of vP/vP before and during the main activity of the swarm, and a recovery of vP/vP to background levels at the end of the swarms. The anomalies are interpreted in terms of the Biot-Gassman equations, assuming the presence of oversaturated fluids degassing during the beginning phase of the swarm activity. © The Authors 2013. Published by Oxford University Press on behalf of The Royal Astronomical Society.
Keywords: Bohemia; Czech Republic; Geophysical prospecting; Shear flow; Tomography; Transport properties; Velocity; Crustal earthquakes; Double differences; Earthquake location; Earthquake source observations; Earthquake swarms; Monitoring purpose; Velocity variations; Volcano seismology; anomaly; arrival time; earthquake swarm; P-wave; S-wave; seismic source; seismic tomography; seismic velocity; seismology; Earthquakes

Water diffusion in potassium-rich phonolitic and trachytic melts - Fanara, Sara; Behrens, Harald; Zhang, Youxue (Chemical Geology, 2013)
Water diffusivity was investigated in phonolitic and trachytic melts containing up to 6wt.% of dissolved water at temperatures between 1373K and 1673K for running time of 108 to 1186s using the diffusion couple technique. The experiments were performed in an internally heated gas pressure vessel (IHPV) at pressures of 0.2 or 0.3GPa and in a piston cylinder apparatus (PCA) at pressures between 0.5 and 2.5GPa. A newly developed rapid heating and rapid quench device was used for short term experiments in the IHPV. Concentration profiles of hydrous species (OH groups and H2O molecules) and total water (bulk water concentration as sum of OH and H2O molecules) were measured along the cylindrical axis of the diffusion sample using IR micro-spectroscopy. The IR spectroscopic technique was calibrated using a set of samples with bulk water contents measured by Karl-Fischer titration. Electron microprobe traverses show no significant change in relative proportions of anhydrous components along H2O profiles, indicating that our data can be treated as effective binary diffusion between H2O and the rest of the silicate melt.Bulk water diffusivity was derived from profiles of total water using a modified Boltzmann-Matano method as well as using fittings assuming a functional relationship between the total water diffusivity (DH2Ot) and the total water concentration (CH2Ot). The fitting of the profiles indicates that for phonolitic melt the water diffusivity is roughly proportional to water content. The following formulation was derived for the prediction of total water diffusivity (m2/s) as a function of T (K) in the T-range of 1373 to 1673K and CH2Ot:logDH2Ot=-7.11-2.07logCH2Ot-4827-4620logCH2OtT.The experimental data are reproduced by this relationship with a standard deviation of 0.07. log units. Water diffusivity in trachytic melts is similar at the same conditions. A pressure effect on water diffusivity could not be resolved in the range 0.2 to 2.5. GPa for phonolitic or trachytic melts. © 2012 Elsevier B.V.
Keywords: Experiments; Infrared spectroscopy; Molecules; Pressure effects; Silicates; Water content; Boltzmann-Matano method; Diffusion couple technique; Functional relationship; Phonolite; Piston-cylinder apparatus; Spectroscopic technique; Trachyte; Water diffusion; concentration (composition); diffusivity; infrared spectroscopy; phonolite; potassium; silicate melt; trachyte; water content; Diffusion in liquids

Why has the Nazca plate slowed since the Neogene? - Quinteros, J.; Sobolev, S.V. (Geology, 2013)
The classic example of the not-well-understood rapid change of tectonic plate motion is the increase and then decrease of the convergence rate between the Nazca and South America plates during the past 25-20 m.y. that coincided with the growth of the Andes Mountains. Currently, the decrease in convergence rate is explained either by the increasing load of the Andes or by the appearance of fl at slab segments beneath South America. Here, we present an alternative view based on a thermomechanical self-consistent (gravity driven) model of Nazca plate subduction. We explain the changes in the convergence rate as a natural consequence of the Nazca plate penetration into the transition zone and lower mantle after long-term oblique subduction of the Farallon plate. The model is consistent with seismic tomographic images of the Nazca plate beneath South America. Our model also shows that the presence of the Andes does not signifi cantly affect the convergence rate between the Nazca and South America plates. © 2012 Geological Society of America.
cited By 53
Keywords: Convergence rates; Lower mantle; Natural consequences; Nazca plate; Neo genes; Oblique subduction; Seismic tomographic images; South America; Tectonic plates; Thermo-mechanical; Transition zones; View-based; Geology; Tomography; Nazca plate; Neogene; plate motion; seismic tomography; subduction zone; transition zone; Andes

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

Temporal variation of b value associated with M 4 earthquakes in the reservoir-triggered seismic environment of the Koyna-Warna region, Western India - Mallika, K.; Gupta, H.; Shashidhar, D.; Rao, N.P.; Yadav, A.; Rohilla, S.; Satyanarayana, H.V.S.; Srinagesh, D. (Journal of Seismology, 2013)
It is generally found that the b values associated with reservoir-triggered seismicity (RTS) are higher than the regional b values in the frequency magnitude relation of earthquakes. In the present study, temporal and spatial variation of b value is investigated using a catalog of 3,000 earthquakes from August 2005 through December 2010 for the Koyna-Warna region in Western India, which is a classical site of RTS globally. It is an isolated (30 × 20 km2) zone of seismicity where earthquakes of up to M 5 are found to occur during phases of loading and unloading of the Koyna and Warna reservoirs situated 25 km apart. For the Warna region, it is found that low b values of 0. 6-0. 9 are associated with earthquakes of M 4 during the loading phase. The percentage correlation of the occurrence of an M ≥ 4 earthquake with a low b value outside the 1σ or 2σ level is as high as 78 %. A drastic drop in the b value of about 50 % being reported for an RTS site may be an important precursory parameter for short-term earthquake forecast in the future. © 2012 Springer Science+Business Media B.V.
cited By 21
Keywords: earthquake event; earthquake magnitude; earthquake precursor; earthquake prediction; earthquake trigger; loading; reservoir-induced seismicity; seismic isolation; temporal variation; unloading; India; Koyna; Maharashtra; Warna

Ries crater and suevite revisited-Observations and modeling Part II: Modeling - Artemieva, N.A.; W{unnemann, K.; Krien, F.; Reimold, W.U.; St{offler, D. (Meteoritics and Planetary Science, 2013)
We present the results of numerical modeling of the formation of the Ries crater utilizing the two hydrocodes SOVA and iSALE. These standard models allow us to reproduce crater shape, size, and morphology, and composition and extension of the continuous ejecta blanket. Some of these results cannot, however, be readily reconciled with observations: the impact plume above the crater consists mainly of molten and vaporized sedimentary rocks, containing very little material in comparison with the ejecta curtain; at the end of the modification stage, the crater floor is covered by a thick layer of impact melt with a total volume of 6-11 km3; the thickness of true fallback material from the plume inside the crater does not exceed a couple of meters; ejecta from all stratigraphic units of the target are transported ballistically; no separation of sedimentary and crystalline rocks-as observed between suevites and Bunte Breccia at Ries-is noted. We also present numerical results quantifying the existing geological hypotheses of Ries ejecta emplacement from an impact plume, by melt flow, or by a pyroclastic density current. The results show that none of these mechanisms is consistent with physical constraints and/or observations. Finally, we suggest a new hypothesis of suevite formation and emplacement by postimpact interaction of hot impact melt with water or volatile-rich sedimentary rocks. © The Meteoritical Society, 2013.
cited By 77

Shock experiments up to 30 GPa and their consequences on microstructures and magnetic properties in pyrrhotite - Mang, C.; Kontny, A.; Fritz, J.; Schneider, R. (Geochemistry, Geophysics, Geosystems, 2013)
Shock experiments with pressures ranging from 3 to 30 GPa have been conducted on a mixed assemblage of hexagonal and monoclinic pyrrhotite. All samples were studied with respect to their particular shock-induced microstructures and magnetic properties at high and low temperatures. Up to 8 GPa, microstructures in shocked pyrrhotite are characterized by mechanical deformation producing a damage of the crystal structure. At pressures of 20 GPa and upward, amorphization and mechanical twinning are the dominant structural features induced by shock. Within the lower-pressure range coercivity, saturation isothermal remanent magnetization and coercivity of remanence increase with shock pressures, in agreement with more single-domain (SD)-like behavior. Simultaneously, the λ-peak of hexagonal pyrrhotite decreases and the 34 K transition of monoclinic pyrrhotite broadens and is depressed. Magnetic hardening is triggered by grain-size reduction, but also by the formation of SD within discrete multidomain grains. Planar deformation features subdivide such multidomain grains into lath-shaped domains with average sizes lying in the SD range. The planar deformation features disappear at 20 GPa and irregular, nanometer-sized amorphous domains occur instead. Pressure release from 30 GPa finally triggers partial melting of pyrrhotite. The sharp interfaces between molten and crystalline pyrrhotite document a rapid change of thermal conditions. Within molten pyrrhotite, quenched iron crystals occur. The presence of native iron strongly influences the magnetic properties, depending on the particular amount in the studied sample and likely affects the magnetic properties of impact lithologies on Earth and extraterrestrial material. ©2013. American Geophysical Union. All Rights Reserved.
cited By 21
Keywords: Coercive force; Experiments; Magnetic properties; Microstructure; Coercivity of remanence; Extraterrestrial material; Grain-size reduction; Mechanical deformation; Mechanical twinning; pyrrhotite; Saturation isothermal remanent magnetizations; shock; Iron ores; crystal structure; deformation; experimental study; grain size; lithology; magnetic property; microstructure; pyrrhotite; remanent magnetization; temperature effect

Rock magnetic properties, magnetic susceptibility, and organic geochemistry comparison in core LZ1029-7 Lake El'gygytgyn, Russia Far East - Murdock, K. J.; Wilkie, K.; Brown, L. L. (Climate of the Past, 2013)

Rock magnetic records of the Qingshankou Formation of SK-1 south borehole in Songliao Basin, Northeast China, and their paleoclimate implications - Li, H.; Zhang, S.; Wu, H.; Zhao, K.; Yang, T.; Zhao, L. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2013)
The south borehole (SK-1s) of the China Cretaceous Continental Scientific Drilling project (Songke 1) penetrated the Late Cretaceous lacustrine sediments in the central depression of the Songliao Basin, Northeast China, in order to reveal the terrestrial records of the Cretaceous climate changes. High-resolution rock magnetic records were obtained on the Qingshankou Formation (K2qn) of SK-1s. The results indicate that detrital magnetite is the main remanence-carrier of the K2qn Formation; while both magnetite and paramagnetic minerals, including clay minerals and pyrite, dominantly contribute to magnetic susceptibility. Although reductive diagenesis may have more or less effect on the magnetic signals of the K2qn Formation, they recorded ancient lake-level changes well, resulting both from the tectonic development of the basin and from the Milankovitch astronomical paleoclimatic changes. The first-order vertical trends of the rock magnetic records were controlled by the shallowing-upwards of the lake-level, caused by the tectonic uplift of the basin. The short-term variations of the rock magnetic records were controlled by the lake-level periodical drift, caused by the fluctuations of the rainfall of the catchment area of the basin, which were controlled by astronomical orbital forcing. In addition, the magnetic records also distinguished two most anoxic periods during the lacustrine anoxic event 1 (LAE1): the sections of 1758-1761m and 1769-1771.5m, which may suggest the two most active periods of surface productivity of the lake. © 2013 Elsevier B.V.
cited By 8
Keywords: borehole; climate variation; Cretaceous; detrital deposit; diagenesis; lacustrine deposit; lake level; magnetic field; magnetic mineral; magnetic susceptibility; magnetite; Milankovitch cycle; orbital forcing; paleoclimate; pyrite; remanent magnetization; uplift; China; Songliao Basin

Rock varnish evidence for a Younger Dryas wet period in the Dead Sea basin - Liu, T.; Broecker, W.S.; Stein, M. (Geophysical Research Letters, 2013)
Rock varnish from 14.6 to 13.2 ka recessional shorelines of late glacial Lake Lisan and fan delta surfaces between 280 and 365 m bmsl (meters below mean sea level) along the western margins of the Dead Sea contains replicable layering patterns, characterized by a low Mn and Ba orange/yellow surface layer and a high Mn and Ba dark basal layer. The deposition of the dark basal layers immediately after the lake recession represents a wet period coinciding with the Younger Dryas (YD) cooling (12.9-11.6 ka), manifesting the influence of midlatitude westerly winds in the eastern Mediterranean-central Levant (EM-CL). In contrast, varnish from the distal base of fan deltas contains only orange/yellow surface layers, diagnostic of the Holocene relatively dry climate. The absence of the dark basal layers in the varnish further indicates a YD high stand at ∼365 m bmsl and a lake level rise of at least 100 m from its Bølling-Ållerød lowstand. This rise stands in contrast to the abrupt drop of the lake level during the Heinrich (H1) cold event, illustrating the opposite response of the EM-CL climate to changes in the North Atlantic climate. The YD wet event most likely reflects a southward shift of the Atlantic meridional overturning circulation-modulated midlatitude westerly wind belt in the EM-CL region. © 2013 American Geophysical Union. All Rights Reserved.
cited By 22
Keywords: Dead sea; Dead sea basins; Mean sea level; North Atlantic; Rock varnishes; Surface layers; wet event; Younger Dryas; Lakes; Manganese; Sea level; Varnish; Climate change; belt; depositional environment; glacial environment; Holocene; meridional circulation; shoreline; surface layer; Dead Sea

SAFOD Brittle Microstructure and Mechanics Knowledge Base (BM2KB) - Babaie, H.A.; Broda Cindi, M.; Hadizadeh, J.; Kumar, A. (Computers and Geosciences, 2013)
Scientific drilling near Parkfield, California has established the San Andreas Fault Observatory at Depth (SAFOD), which provides the solid earth community with short range geophysical and fault zone material data. The BM2KB ontology was developed in order to formalize the knowledge about brittle microstructures in the fault rocks sampled from the SAFOD cores. A knowledge base, instantiated from this domain ontology, stores and presents the observed microstructural and analytical data with respect to implications for brittle deformation and mechanics of faulting. These data can be searched on the knowledge base's Web interface by selecting a set of terms (classes, properties) from different drop-down lists that are dynamically populated from the ontology. In addition to this general search, a query can also be conducted to view data contributed by a specific investigator. A search by sample is done using the EarthScope SAFOD Core Viewer that allows a user to locate samples on high resolution images of core sections belonging to different runs and holes.The class hierarchy of the BM2KB ontology was initially designed using the Unified Modeling Language (UML), which was used as a visual guide to develop the ontology in OWL applying the Prot'eg'e ontology editor. Various Semantic Web technologies such as the RDF, RDFS, and OWL ontology languages, SPARQL query language, and Pellet reasoning engine, were used to develop the ontology. An interactive Web application interface was developed through Jena, a java based framework, with AJAX technology, jsp pages, and java servlets, and deployed via an Apache tomcat server. The interface allows the registered user to submit data related to their research on a sample of the SAFOD core. The submitted data, after initial review by the knowledge base administrator, are added to the extensible knowledge base and become available in subsequent queries to all types of users. The interface facilitates inference capabilities in the ontology, supports SPARQL queries, allows for modifications based on successive discoveries, and provides an accessible knowledge base on the Web. © 2013 Elsevier Ltd.
cited By 2
Keywords: Apache Tomcat server; High resolution image; Interactive web applications; OWL; RDF; SAFOD core; San Andreas fault; Semantic Web technology; Knowledge based systems; Microstructure; Query languages; Strike-slip faults; Unified Modeling Language; Core samples; brittle deformation; brittle medium; drilling; faulting; knowledge; microstructure; San Andreas Fault

Scientific drilling and related research in the Samail ophiolite, Sultanate of Oman - Kelemen, Peter; Al Rajhi, Ali; Godard, Marguerite; Ildefonse, Benoit; K{opke, J{urgen; MacLeod, Chris; Manning, Craig; Michibayashi, Katsu; Nasir, Sobhi; Shock, Everett; et al. (Scientific Drilling, 2013)

Sea-level control of new jersey margin architecture: Palynological evidence from integrated ocean drilling program expedition 313 - McCarthy, F.M.; Katz, M.E.; Kotthoff, U.; Browning, J.V.; Miller, K.G.; Zanatta, R.; Williams, R.H.; Drljepan, M.; Hesselbo, S.P.; Bjerrum, C.J.; Mountain, G.S. (Geosphere, 2013)
Integrated Ocean Drilling Program Expedition 313 recovered Miocene sequences at Holes M0027A and M0029A on the New Jersey shallow shelf that contain a characteristic acid-resistant organic component. The palynofacies within each sequence refl ects variations in terrigenous versus authigenic fl ux through the Miocene that are associated with sea-level change. Very high ratios of terrigenous versus marine palynomorphs and of oxidation-resistant versus susceptible dinocysts are associated with seismic sequence boundaries, consistent with their interpretation as sequence-bounding unconformities generated at times of low sea level. Comparison of palynological distance from shoreline estimates with paleodepth estimates derived from foraminiferal data allows relative sea level to be reconstructed at both sites. Ages assigned using dinocyst biostratigraphy are consistent with other chronostratigraphic indicators allowing sequence boundaries to be correlated with Miocene oxygen isotope (Mi) events. Paleoclimatic evidence from the pollen record supports the global climate changes seen in the oxygen isotope data. Although chronological control is relatively crude, Milankovitch-scale periodicity is suggested for parasequences visible in thick sequences deposited in relatively deep water where substantial accommodation existed, such as during the early Langhian at Site 29 (Middle Miocene Climatic Optimum). Palyno logical analysis thus supports the long-held hypothesis that glacioeustasy is a dominant process controlling the architecture of continental margins.
cited By 27
Keywords: Continental margin; Global climate changes; Integrated ocean drilling programs; Organic components; Oxidation resistant; Relative sea level; Sea-level control; Sequence-bounding unconformities; Isotopes; Oxygen; Submarine geology; Sea level; biostratigraphy; chronostratigraphy; continental shelf; glacioeustacy; Miocene; Ocean Drilling Program; palynology; sea level change; sequence boundary; sequence stratigraphy; Atlantic Ocean; New Jersey Margin; New Jersey Shelf

Sedimentary evolution of Lake Van (Eastern Turkey) reconstructed from high-resolution seismic investigations - Cukur, D.; Krastel, S.; Demirel-Schl{uter, F.; Demirbag, E.; Imren, C.; Toker, M. (International Journal of Earth Sciences, 2013)
This paper presents results of a multi-channel seismic reflection survey at Lake Van and provides constraints on the sedimentary evolution of the lake. The geophysical data of the lake confirm the existence of three physiographic provinces: a shelf, a slope, and a deep, relatively flat basin. The most prominent features identified on the shelf and slope are clinoforms, submerged channels, as well as closely spaced lake floor depressions, reflecting a highly variable lake-level history. The morphological depressions are interpreted as resulting from subaquatic erosion by channelized, sediment-laden currents into horizontally bedded fan sediments. Submerged channels on the eastern shelf are interpreted as meandering-slope channels, probably as a consequence of a lake-level fall that exposed the shelf area. Clinoforms on the Eastern fan may represent relict deltas formed during stationary or slightly rising lake-level intervals. Merging subsurface imaging interpretation with morphological studies of exposed sediments reveals lake-level fluctuations of several hundreds of meters during the past ca. 550 ka. The lake has three prominent basins (Tatvan, Deveboynu, and the Northern basin) separated by basement ridges (e. g., the Northern ridge). The seismic units in the Tatvan and Northern basins are dominated by alternations of well-stratified and chaotic reflections, while the Deveboynu basin subsurface consists mainly of chaotic units. The chaotic seismic facies are interpreted as mass-flow deposits, probably triggered by earthquakes and/or rapid lake-level fluctuations. The moderate-to-high-amplitude, well-stratified facies seen in the deeper parts of the basins are interpreted as lacustrine deposits intercalated with tephra layers. The occurrence of a clinoform in the deepest part of the lake suggests a major flooding stage of Lake Van more than 400 ka ago. Seismic profiles from the deepest part of the lake basin show remarkably uniform and continuous stratigraphic units without any major erosional feature following the flooding event, indicating that the lake was never completely dry afterward and therefore significantly older than previously suggested. © 2012 Springer-Verlag.
cited By 39
Keywords: erosion; lacustrine deposit; lake level; sedimentary sequence; seismic reflection; tephra; Lake Van; Turkey

Seismic and well-log inference of gas-hydrate accumulations on Richards Island, Northwest Territories, Canada - Bellefleur, G.; Riedel, M.; Brent, T. (Leading Edge, 2013)
The Mackenzie Delta in Canada's Northwest Territories hosts many permafrost-related gas-hydrate accumulations that were indirectly discovered or inferred from conventional hydrocarbon exploration programs. In particular, gas-hydrate intervals characterized with high saturation show high resistivity and high P-and S-wave velocity on well-log data, are typically found in sand-rich horizons. The acoustic impedance contrast between nonhydrate and hydrate-bearing sediments usually produces strong amplitude reflections on seismic data. Such a signature was previously observed onshore at Mallik, Northwestern Territories (Collett et al., 1999), on the North Slope of Alaska (Collett et al., 2011). Here, we use 2D and 3D seismic reflection data acquired by industry on Richards Island to map and characterize gas-hydrate accumulations beneath a thick permafrost area of the Mackenzie Delta (Figure 1). Specifically, we show new seismic evidences of gas-hydrate accumulations above the Ya Ya and Umiak conventional gas fields. © 2013 by The Society of Exploration Geophysicists.
cited By 0
Keywords: Acoustic impedance; Gases; Hydration; Permafrost; Petroleum prospecting; Seismic prospecting; Seismic waves; Seismology; Shear waves; Wave propagation; Well logging; Conventional hydrocarbons; High resistivity; Hydrate accumulations; Hydrate bearing sediments; North Slope of Alaska; P- and S-wave velocities; Permafrost area; Seismic evidence; Gas hydrates; detection method; gas hydrate; hydrocarbon exploration; permafrost; S-wave; seismic data; seismic reflection; well logging; Alaska; Canada; Mackenzie Delta; North Slope; Northwest Territories; Northwest Territories; Richards Island; United States

Seismic evidence of shallow gas from Lake Van, eastern Turkey - Cukur, D.; Krastel, S.; Tomonaga, Y.; Çağatay, M.N.; Meydan, A.F. (Marine and Petroleum Geology, 2013)
Analysis of multi-channel seismic reflection and chirp data from Lake Van (eastern Turkey) reveals various shallow gas indicators including seismic chimneys, enhanced reflections, bright spots, mud volcanoes, pockmarks, and acoustic blanking. The enhanced reflections, suggesting the presence of free gas, are most dominant and observed at more than 200 locations. They are characterized by very-high amplitude reflections and occur in both deep and shallow sedimentary sections. Some enhanced reflections are accompanied by very subtle seafloor expressions such as mounds, which may suggest active venting activity. Seismic chimneys or columnar zones of amplitude blanking have been observed in much of the surveyed area. Seismic chimneys in the study area cannot be associated with any known faults that would act as migration pathways for deep fluids. This suggests that the observed structures in Lake Van sediments allow the preferential emission of gases which might be for a large share of biogenic origin. The acoustic blanking, characterized by transparent or chaotic seismic facies, is seen in the eastern part of the lake. The lakeward edge of the acoustic blanking largely coincides with the 100m water depth contour, indicating that (past) changes of the hydrostatic pressure may be responsible for the distribution of these anomalies. Mound-like features, interpreted as mud volcanoes, occur in a few locations. The presence of these features may suggest active gas emission. Very strong amplitude anomalies or bright spots with negative polarity, indicating gas-charged zones, are also seen in a number of locations. Pockmarks are observed only in the northeastern part of the study area. The scarce occurrence of pockmarks in the study area might be ascribed to a higher permeability of the lake sediments or to the absence of the substrate/reservoir providing the critical mass of gases necessary to produce such features. Turbidites, tephra layers, and deltaic deposits have the potential to provide ideal conditions to allow the sediments to act as a gas reservoir. © 2013 Elsevier Ltd.
cited By 24
Keywords: Bright spots; Enhanced reflections; Lake vans; Pockmarks; Shallow gas; Chimneys; Hydrostatic pressure; Lakes; Sediments; Seismology; Volcanoes; Gases; deltaic deposit; facies analysis; hydrocarbon reservoir; hydrostatic pressure; lacustrine deposit; mud volcano; permeability; pockmark; seismic reflection; tephra; turbidite; venting; Lake Van; Turkey

Shock experiments up to 30 GPa and their consequences on microstructures and magnetic properties in pyrrhotite - Mang, C.; Kontny, A.; Fritz, J.; Schneider, R. (Geochemistry, Geophysics, Geosystems, 2013)
Shock experiments with pressures ranging from 3 to 30 GPa have been conducted on a mixed assemblage of hexagonal and monoclinic pyrrhotite. All samples were studied with respect to their particular shock-induced microstructures and magnetic properties at high and low temperatures. Up to 8 GPa, microstructures in shocked pyrrhotite are characterized by mechanical deformation producing a damage of the crystal structure. At pressures of 20 GPa and upward, amorphization and mechanical twinning are the dominant structural features induced by shock. Within the lower-pressure range coercivity, saturation isothermal remanent magnetization and coercivity of remanence increase with shock pressures, in agreement with more single-domain (SD)-like behavior. Simultaneously, the λ-peak of hexagonal pyrrhotite decreases and the 34 K transition of monoclinic pyrrhotite broadens and is depressed. Magnetic hardening is triggered by grain-size reduction, but also by the formation of SD within discrete multidomain grains. Planar deformation features subdivide such multidomain grains into lath-shaped domains with average sizes lying in the SD range. The planar deformation features disappear at 20 GPa and irregular, nanometer-sized amorphous domains occur instead. Pressure release from 30 GPa finally triggers partial melting of pyrrhotite. The sharp interfaces between molten and crystalline pyrrhotite document a rapid change of thermal conditions. Within molten pyrrhotite, quenched iron crystals occur. The presence of native iron strongly influences the magnetic properties, depending on the particular amount in the studied sample and likely affects the magnetic properties of impact lithologies on Earth and extraterrestrial material. ©2013. American Geophysical Union. All Rights Reserved.
cited By 21

Synoptic climatology and recent climate trends at Lake El'gygytgyn - Nolan, M.; Cassano, E. N.; Cassano, J. J. (Climate of the Past, 2013)
We developed a synoptic climatology for Lake El'gygytgyn, Chukotka Russia, and explored modern climate trends affecting air temperatures there to aid in paleoclimate reconstructions of a 3.6 million-year-old sediment core taken from the lake. Our self-organized mapping (SOM) approach identified 35 synoptic weather patterns, based on sea level pressure, that span the range of synoptic patterns influencing the study domain over the 1961-2009 NCEP/NCAR analysis period. We found strong seasonality in modern weather patterns, with summer weather primarily characterized by weak low pressure systems over the Arctic Ocean or Siberia and winter weather primarily characterized by strong high pressure over the Arctic Ocean and strong low pressure in the Pacific Ocean. In general, the primary source of variation in air temperatures came from the dominant patterns in each season, which we identify in the text, and nearly all of the dominant weather patterns here have shown increasing temperatures. We found that nearly all of the warming in mean annual temperature over the past 50 yr (about 3°C) occurred during sub-freezing conditions on either side of summer (that is, spring and fall). Here we found that the most summer-like weather patterns (low pressures to the north) in the shoulder seasons were responsible for much of the change. Finally, we compared the warmest 15 yr of the record (1995-2009) to the coolest (1961-1975) and found that changes in thermodynamics of weather were about 3 to 300 times more important than changes in frequency of weather patterns in controlling temperature variations during spring and fall, respectively. That is, in the modern record, general warming (local or advected) is more important by orders of magnitude than changes in storm tracks in controlling air temperature at Lake El'gygytgyn. We conclude with a discussion of how these results may be relevant to the paleoclimate reconstruction efforts and how this relevancy could be tested further. © Author(s) 2013.
cited By 9
Keywords: air temperature; climate change; dominance; freezing; low pressure; paleoclimate; seasonality; sediment core; synoptic meteorology; temperature inversion; thermodynamics; Chukchi; Elgygytgyn Lake; Russian Federation

Source mechanisms of the 2000 earthquake swarm in the West Bohemia/Vogtland region (Central Europe) - Hor'alek, Josef; Š'ilen'y, Jan (Geophysical Journal International, 2013)
An earthquake swarm of magnitudes up to ML = 3.2 occurred in the region of West Bohemia/Vogtland (border area between Czech Republic and Germany) in autumn 2000. This swarmconsisted of nine episodic phases and lasted 4 months. We retrieved source mechanisms of 102 earthquakes with magnitudes between ML = 1.6 and 3.2 applying inversion of the peak amplitudes of direct P and SH waves, which were determined from ground motion seismograms. The investigated events cover the whole swarm activity in both time and space. We use data from permanent stations of seismic network WEBNET and from temporal stations, which were deployed in the epicentral area during the swarm; the number of stations varied from 7 to 18. The unconstrained moment tensor (MT) expression of the mechanism, which describes a general system of dipoles, that is both double-couple (DC) and non-DC sources, was applied. MTs of each earthquake were estimated by inversion of three different sets of data: P-wave amplitudes only, P- and SH-wave amplitudes and P-wave amplitudes along with the SH-wave amplitudes from a priori selected four 'base' WEBNET stations, the respective MT solutions are nearly identical for each event investigated. The resultant mechanisms of all events are dominantly DCs with only insignificant non-DC components mostly not exceeding 10 per cent. We checked reliability of the MTs in jackknife trials eliminating some data; we simulated the mislocation of hypocentre or contaminated the P- and SH-wave amplitudes by accidental errors. These tests proved stable and well constrained MT solutions. The massive dominance of the DC in all investigated events implies that the 2000 swarmconsisted of a large number of pure shears along a fault plane. The focal mechanisms indicate both oblique-normal and oblique-thrust faulting, however, the oblique-normal faulting prevails. The predominant strikes and dips of the oblique-normal events fit well the geometry of the main fault plane Nov'y Kostel (NK) and also match the strike, dip and rake of the largest ML =4.6 earthquake of a strong swarm in 1985/86. On the contrary, the 2000 source mechanisms differ substantially from those of the 1997-swarm (which took place in two fault segments at the edge of the main NK fault plane) in both the faulting and the content of non-DC components. Further, we found that the scalar seismic moment M0 is related to the local magnitude ML used by WEBNET as M0 ∝ 101.12ML, which differs from the scaling law using moment magnitude Mw, that is M0 ∝ 101.5 ML. © The Authors 2013.
Keywords: Bohemia; Czech Republic; Germany; Vogtland; Faulting; Seismic waves; Shear waves; Accidental error; Dynamics and mechanics of faulting; Earthquake source observations; Earthquake swarms; Fracture and flows; Intra-plate process; Moment magnitudes; Source mechanisms; data inversion; earthquake magnitude; earthquake swarm; faulting; focal mechanism; ground motion; intraplate process; moment tensor; P-wave; SH-wave; source parameters; Earthquakes

Source parameters of earthquakes in the reservoir-triggered seismic (RTS) zone of Koyna-Warna, Western India - Yadav, A.; Shashidhar, D.; Mallika, K.; Rao, N.P.; Rohilla, S.; Satyanarayana, H.V.S.; Srinagesh, D.; Gupta, H. (Natural Hazards, 2013)
New empirical relations are derived for source parameters of the Koyna-Warna reservoir-triggered seismic zone in Western India using spectral analysis of 38 local earthquakes in the magnitude range ML 3.5-5.2. The data come from a seismic network operated by the CSIR-National Geophysical Research Institute, India, during March 2005 to April 2012 in this region. The source parameters viz. seismic moment, source radius, corner frequency and stress drop for the various events lie in the range of 1013-1016 Nm, 0.1-0.4 km, 2.9-9.4 Hz and 3-26 MPa, respectively. Linear relationships are obtained among the seismic moment (M0), local magnitude (ML), moment magnitude (Mw), corner frequency (fc) and stress drop (Δσ). The stress drops in the Koyna-Warna region are found to increase with magnitude as well as focal depths of earthquakes. Interestingly, accurate depths derived from moment tensor inversion of earthquake waveforms show a strong correlation with the stress drops, seemingly characteristic of the Koyna-Warna region. © 2013 Springer Science+Business Media Dordrecht.
cited By 13
Keywords: earthquake event; earthquake magnitude; earthquake trigger; focal mechanism; reservoir-induced seismicity; seismic moment; seismic zone; source parameters; spectral analysis; stress analysis; waveform analysis; India

Spatial and temporal variability in sedimentological and geochemical properties of sediments from an anoxic crater lake in West Africa: Implications for paleoenvironmental reconstructions - Shanahan, Timothy M.; McKay, Nicholas; Overpeck, Jonathan T.; Peck, John A.; Scholz, Christopher; Heil, Clifford W.; King, John (Palaeogeography, Palaeoclimatology, Palaeoecology, 2013)
The physical, inorganic and organic geochemical and stable isotopic characteristics of lacustrine sediments can provide valuable insights into past environmental changes, provided that the environmental controls on these characteristics are well understood. In the present study, a set of 155 modern vegetation, catchment soil, river sediments and lake surface sediment samples are used to characterize the spatial patterns of TOC, TN, C/N ratios, stable isotope, major element, and particle size distributions within Lake Bosumtwi, a meromictic crater lake in West Africa. Spatial variations in sediment characteristics are strongly correlated with depth and distance from shore, reflecting the dominant influence of lake level on the relative proportions of littoral and pelagic depositional systems and their impact on the physical and geochemical properties of lacustrine sediments. This is supported by a principal component analysis, which indicates that 65% of the variance in the dataset is explained by depth-related variability in the sedimentary components. Variations in sedimentary organic matter reflect the combined influences of productivity, preservation and the relative proportions of aquatic and terrestrial organic matter sources. Grain size and Si content are dominantly influenced by the delivery of clastic materials from the watershed to the lake, whereas Fe and Ca appear to be most strongly influenced by the delivery of reduced metals and nutrients from the anoxic hypolimnion to the surface. With the exception of grain size, all of the sediment parameters record synchronous century-scale variability over the past 2.5ka, consistent with independent evidence for changes in lake level. However, the magnitude of changes in sediment characteristics differs, reflecting different sensitivities to water depth, particularly in the deepest part of the lake basin where the sediment cores were collected. However, even the parameters with the most linear and strongly significant relationships with depth (e.g., TOC, TN) significantly overestimate the magnitude of lake level changes, suggesting that these parameters may be best suited to qualitative paleolake level reconstructions. Over the last 2 centuries, changes in C/N and δ13C became decoupled from the other geochemical proxies and the inferred rise in lake level. We hypothesize that this reflects the influence of anthropogenic land use change on the composition of terrestrial organic matter sources contributing to the lake. This result highlights the potential difficulties in reconstructing past environmental changes from indirect proxy measurements when those proxies may be subject to multiple varying controls. © 2013 Elsevier B.V.
Keywords: Ashanti; Ghana; Lake Bosumtwi; West Africa; correlation; data set; environmental change; geochemical survey; lake ecosystem; land use change; organic matter; paleoenvironment; parameterization; pelagic deposit; principal component analysis; spatiotemporal analysis; stable isotope

Stable isotope values (δ18o & δ13c) of multiple ostracode species in a large neotropical lake as indicators of past changes in hydrology - P'erez, Liseth; Curtis, Jason; Brenner, Mark; Hodell, David; Escobar, Jaime; Lozano, Socorro; Schwal, Antje (Quaternary Science Reviews, 2013)
Modern lake hydrodynamics, ostracode species autecology, stable isotopes (δ18O and δ13C) of multiple ostracode species, ostracode taphonomy and sediment geochemistry were studied to improve interpretation of the late Pleistoceneeearly Holocene ( 24-10 ka) stable isotope record of ostracodes in sediment core PI-6 from Lago Pet'en Itz'a, northern Guatemala. Oxygen and carbon stable isotopes in modern and fossil species assemblages of Lago Pet'en Itz'a were used as indicators of changes in the balance between evaporation and precipitation, past lake level and carbon source. Ostracode taphonomy was used to detect past periods of strong currents, high-energy environments, and possible partial or full mixing of the lake. The modern lake water isotopic composition displays clear seasonal differences that are independent of lake level fluctuations. Modern benthic species displayed lower δ18O and δ13C values than nektobenthic species, with differences of 3.0‰ and 5.3‰, respectively. Valves of nektobenthic species display higher values of d13C because these ostracodes live in shallower environments among abundant algae and aquatic plants, where productivity is high. The benthic species Limnocythere opesta Brehm, 1939 displayed the smallest average offset from d18O water (0.3‰) and the largest offset from δ13CDIC values (4.1‰) among studied ostracode species. Nektobenthic species Heterocypris punctata Keyser, 1975 displayed the smallest difference relative to the δ13CDIC values (0.1‰). Late Pleistoceneeearly Holocene climate conditions and water levels in Lago Pet'en Itz'a can be summarized as follows: 1) high lake levels and cold conditions (Last Glacial Maximum [LGM], 24-19 ka), 2) fluctuating lake levels and cold conditions (Heinrich Stadial 1 [HS1], 19-15 ka), 3) high lake levels and warm and wetter conditions (Bølling-Allerød [BA], 15-13 ka), 4) low lake levels and dry conditions (Younger Dryas [YD], 13-11.5 ka) and 5) high lake levels and warm and wetter conditions (early Holocene, 11.5-10.0 ka). Average lake level fluctuation in Lago Pet'en Itz'a during the late Pleistoceneeearly Holocene was as much as 25 m. Ostracode analyses suggest that the LGM was characterized by relatively low d18O (4.7 to 6.0 &), and d13C values (7.1 to 6.4‰) in ostracode valves, high inferred water depths and high percentages of broken adult and juvenile valves (>66%), suggesting a high-energy environment, strong currents, partial to full mixing, downslope transport, colder water temperatures and wetter conditions. An increase in the relative abundance of the benthic species L. opesta and higher numbers of broken valves suggest heavy precipitation events during the LGM ( 23.7, 21.7, 20.8 and 20.1 ka). HS1 was predominantly dry, but we identified times when lake levels were slightly higher, at the onset of the deglacial and a brief period ( 17-16 ka) between HS1b and HS1a. All studied climate proxies indicate wetter and warmer conditions and lake system stability during the BA. Lake levels dropped during the YD and gradually increased during the Preboreal and early Holocene. We demonstrate that modern and fossil ostracode isotopic signatures, species assemblages and taphonomy can be used together with physical and geochemical variables in Lago Pet'en Itz'a sediments to make high-resolution inferences about late Pleistoceneeearly Holocene environmental changes in the lowland Neotropics. © 2012 Elsevier Ltd.
Keywords: Guatemala [Central America]; Lake Peten Itza; Peten; algae; Heterocypris punctata; Limnocythere; Ostracoda; Climate change; Fluid dynamics; Geochemistry; Hydrodynamics; Isotopes; Mixing; Sediments; System stability; Water levels; Autecology; Environmental change; Holocenes; Lake level changes; Neotropics; Ostracoda; Stable isotopes; abundance; autecology; benthos; fossil assemblage; fossil record; hydrodynamics; isotopic composition; lake level; Neotropical Region; ostracod; oxygen isotope; paleoecology; paleohydrology; paleolimnology; Pleistocene-Holocene boundary; seasonal variation; sediment core; stable isotope; taphonomy; Younger Dryas; Lakes

Stable isotopic evidence for climate and basin evolution of the Late Cretaceous Songliao basin, China - Chamberlain, C.P.; Wan, X.; Graham, S.A.; Carroll, A.R.; Doebbert, A.C.; Sageman, B.B.; Blisniuk, P.; Kent-Corson, M.L.; Wang, Z.; Chengshan, W. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2013)
Because of the need to understand the links and feedbacks of the carbon cycle during times of global greenhouse conditions numerous studies have focused on the Cretaceous climate. Much of what we know about this warm period in Earth's history comes from the study of ocean sediments recovered from both ocean drill cores and marine sediments exposed at the Earth's surface. In contrast, there are few studies of Cretaceous terrestrial sediments. The Songliao basin located in northeast China offers a unique opportunity to understand Cretaceous paleoclimate of terrestrial settings because it contains a nearly complete record of lacustrine sediments deposited throughout the Cretaceous and there is an active drilling program to recover core from this paleolake. We present carbon, oxygen and strontium isotopic data from ostracods collected from two drill cores (SK-1 (N) and SK-1 (S)) that cover a time interval that extends from the Turonian through the Maastrichtian. These data record robust isotopic trends with numerous carbon and oxygen isotope shifts that are both rapid and long-term. We tentatively interpret this record to reflect changes in both global climate and regional basin evolution. In the Turonian and Coniacian Qingshankou Formation we observe several carbon isotope shifts that appear to be correlative to marine isotopic records based upon timing and magnitude of the isotopic changes. We suggest that the carbon isotope record in the Songliao basin reflect the decrease in carbon isotope ratios following the strong positive excursion at the Cenomanian/Turonian boundary, a positive isotope excursion in the late Turonian, and the negative isotope shift that occurs at the Turonian/Coniacian boundary. Upward in the section, however, the marine and Songliao isotopic records diverge as sediment sources shift from the southwest, east and north to more northerly. Strontium isotopes record the change in source region as they increase markedly between the Coniacian/Santonian Yaojia and Santonian/Campanian Nenjiang Formations. As this is the first isotopic record of the Songliao basin we are cautious about many of our interpretations of these isotopic data. Yet it is clear that with tighter age constraints and focused sampling centered on many of the isotope excursions presented here will allow for a deeper understanding of the terrestrial response to changing climate and the hydrologic response to basin evolution. © 2012 Elsevier B.V.
cited By 90
Keywords: basin evolution; Campanian; carbon isotope; Cenomanian-Turonian boundary; Coniacian; hydrological response; Maastrichtian; marine isotope stage; ostracod; oxygen isotope; paleoclimate; Santonian; stable isotope; strontium isotope; China; Nen Basin; Songliao Basin; Coniacian; Ostracoda

Statistical classifi cation of log response as an indicator of facies variation during changes in sea level: Integrated Ocean Drilling Program Expedition 313 - Inwood, J.; Lofi, J.; Davies, S.; Basile, C.; Bjerum, C.; Mountain, G.; Proust, J.; Otsuka, H.; Valppu, H. (Geosphere, 2013)
In this study, a novel application of a statistical approach is utilized for analysis of downhole logging data from Miocene-aged siliciclastic shelf sediments on the New Jersey Margin (eastern USA). A multivariate iterative nonhierarchical cluster analysis (INCA) of spectral gamma-ray logs from Integrated Ocean Drilling Program (IODP) Expedition 313 enables lithology within this siliciclastic succession to be inferred and, through comparison with the 1311 m of recovered core, a continuous assessment of depositional sequences is constructed. Signifi cant changes in INCA clusters corroborate most key stratigraphic surfaces interpreted from the core, and this result has particular value for surface recognition in intervals of poor core recovery. This analysis contributes to the evaluation of sequence stratigraphic models of large-scale clinoform complexes that predict depositional environments, sediment composition, and stratal geometries in response to sea-level changes. The novel approach of combining statistical analysis with detailed lithostratigraphic and seismic refl ection data sets will be of interest to any scientists working with downhole logs, especially spectral gamma-ray data, and also provides a reference for the strengths and weaknesses of multi component analysis applied to continental margin lithofacies. The method presented here is appropriate for evaluating successions elsewhere and also has value for hydrocarbon exploration where sequence stratigraphy is a fundamental tool. © 2013 Geological Society of America.
cited By 12
Keywords: cluster analysis; continental margin; core logging; depositional environment; depositional sequence; hydrocarbon exploration; lithofacies; lithology; lithostratigraphy; Miocene; Ocean Drilling Program; sea level change; sediment chemistry; sequence stratigraphy; shelf sediment; siliciclastic deposit; Atlantic Ocean; New Jersey Margin

Stress rotation and recovery in conjunction with the 1999 Izmit Mw 7.4 earthquake - Ickrath, M.; Bohnhoff, M.; Bulut, F.; Dresen, G. (Geophysical Journal International, 2013)
Local rotations of the stress field might serve as an indicator to characterize the physical status of individual fault segments during the seismic cycle. In this study we focus on the pre-, 2-month aftershock- and post-seismic phase of the 1999 Mw7.4 Izmit earthquake in northwestern Turkey. Using a compilation of focal mechanism data we investigate spatiotemporal changes of the stress field orientations and find distinct variations along individual fault segments. Whereas the regional stress field prior to the Izmit earthquake and following the 2-month aftershock sequence reflects a stable strike-slip regime, the early aftershock period is dominated by EW-extension below the Akyazi Basin. During the 2-month aftershock period we find significant changes from strike-slip to normal-faulting during the main shock following by a systematic backrotation to the pre-main shock stress regime. This backrotation commences first in the Akyazi Plain hosting a co-seismic slip deficit of ≤3m and propagates then further to the east towards the Karadere and D{uzce faults where the D{uzce Mw 7.1 main shock nucleated 87 d later. Our results confirm that spatiotemporal stress field rotations are a useful indicator for variations of the seismotectonic setting during the seismic cycle. © The Authors 2013. Published by Oxford University Press on behalf of The Royal Astronomical Society.
cited By 19
Keywords: Earthquake dynamics; Regional stress field; Seismic cycle; Seismicity and tectonics; Seismotectonic settings; Spatial analysis; Spatio-temporal changes; Stress-field orientation; Fault slips; Stresses; Transform faults; Earthquakes; aftershock; coseismic process; focal mechanism; Kocaeli earthquake 1999; normal fault; seismicity; seismotectonics; spatial analysis; stress field; strike-slip fault; transform fault; Akyazi; Sakarya; Turkey

Structural Preconditions of West Bohemia Earthquake Swarms - Novotn'y, M.; Špič'ak, A.; Weinlich, F.H. (Surveys in Geophysics, 2013)
The West Bohemia and adjacent Vogtland are well known for quasi-periodical earthquake swarms persisting for centuries. The seismogenic area near Nov'y Kostel involved about 90 % of overall earthquake activity clustered here in space and time. The latest major earthquake swarm took place in August-September 2011. In 1994 and 1997, two minor earthquake swarms appeared in another location, near Lazy. Recently, the depth-recursive tomography yielded a velocity image with an improved resolution along the CEL09 refraction profile passing between these swarm areas. The resolution, achieved in the velocity image and its agreement with the inverse gravity modeling along the collateral 9HR reflection profile, enabled us to reveal the key structural background of these West Bohemia earthquake swarms. The CEL09 velocity image detected two deeply rooted high-velocity bodies adjacent to the Nov'y Kostel and Lazy focal zones. They correspond to two Variscan mafic intrusions influenced by the SE inclined slab of Saxothuringian crust that subducted beneath the Tepl'a-Barrandian terrane in the Devonian era. In their uppermost SE inclined parts, they roof both focal zones. The high P-wave velocities of 6,100-6,200 m/s, detected in both roofing caps, indicate their relative compactness and impermeability. The focal domains themselves are located in the almost gradient-free zones with the swarm foci spread near the axial planes of profound velocity depressions. The lower velocities of 5,950-6,050 m/s, observed in the upper parts of focal zones, are indicative of less compact rock complexes corrugated and tectonically disturbed by the SE bordering magma ascents. The high-velocity/high-density caps obviously seal the swarm focal domains because almost no magmatic fluids of mantle origin occur in the Nov'y Kostel and Lazy seismogenic areas of the West Bohemia/Vogtland territory, otherwise rich in the mantle-derived fluids. This supports the hypothesis of the fluid triggering of earthquake swarms. The sealed focal domains retain ascending magmatic fluids until their critical pressure and volumes accumulated cause rock micro-fractures perceived as single earthquake bursts. During a swarm period, the focal depths of these sequential events become shallower while their magnitudes grow. We assume that coalescence of the induced micro-fractures forms temporary permeability zones in the final swarm phase and the accumulated fluids release into the overburden via the adjacent fault systems. The fluid release usually occurs after the shallowest events with the strongest magnitudes ML > 3. The seasonal summer declines of hydrostatic pressure in the Cheb Basin aquifer system seem to facilitate and trigger the fluid escape as happened for the 2000, 2008, and 2011 earthquake swarms. The temporary fluid release, known as the valve-fault action, influences the surface aquifer systems in various manners. In particular, we found three quantities, the strain, mantle-derived 3He content in CO2 surface sources and ground water levels, which display a 3-5 months decline before and then a similar restoration after each peak earthquake during the swarm activities. The revealed structure features are particularly important since the main Nov'y Kostel earthquake swarm area is proposed as a site for the ICDP project, 'Eger Rift Drilling'. © 2013 Springer Science+Business Media Dordrecht.
cited By 3
Keywords: Aquifers; Faulting; Groundwater resources; Hydrostatic pressure; Image enhancement; Inverse problems; Refraction; Roofs; Seismic waves; Structure (composition); Tomography; Velocity; Water levels; 9hr reflection profiles; Bohemian massifs; CEL09 refraction profiles; Earthquake swarms; Gravity model; Saxothuringian; Earthquakes; earthquake magnitude; earthquake mechanism; earthquake swarm; gravity field; Hercynian orogeny; hydrostatic pressure; inverse analysis; refraction; slab; subduction; tomography; Bohemian Massif; Cheb Basin; Czech Republic; Germany; Karlovarsky; Vogtland

Sulfate reduction controlled by organic matter availability in deep sediment cores from the saline, alkaline lake van (Eastern Anatolia, Turkey) - Glombitza, C.; Stockhecke, M.; Schubert, C.J.; Vetter, A.; Kallmeyer, J. (Frontiers in Microbiology, 2013)
As part of the International Continental Drilling Program deep lake drilling project PaleoVan, we investigated sulfate reduction (SR) in deep sediment cores of the saline, alkaline (salinity 21.4%, alkalinity 155 m mEq-1, pH 9.81) Lake Van, Turkey. The cores were retrieved in the Northern Basin (NB) and at Ahlat Ridge (AR) and reached a maximum depth of 220 m. Additionally, 65-75 cm long gravity cores were taken at both sites. SR rates (SRR) were low (≥22 nmol cm-3 day-1) compared to lakes with higher salinity and alkalinity, indicating that salinity and alkalinity are not limiting SR in Lake Van. Both sites differ significantly in rates and depth distribution of SR. In NB, SRR are up to 10 times higher than at AR. SR could be detected down to 19 mblf (meters below lake floor) at NB and down to 13 mblf at AR. Although SRR were lower at AR than at NB, organic matter (OM) concentrations were higher. In contrast, dissolved OM in the pore water at AR contained more macromolecular OM and less low molecular weight OM. We thus suggest, that OM content alone cannot be used to infer microbial activity at Lake Van but that quality of OM has an important impact as well. These differences suggest that biogeochemical processes in lacustrine sediments are reacting very sensitively to small variations in geological, physical, or chemical parameters over relatively short distances. © 2013 Glombitza, Stockhecke, Schubert, Vetter and Kallmeyer.
cited By 37
Keywords: organic matter; sulfate; alkalinity; article; biogeochemical cycling; biosphere; carbon nitrogen ratio; ion pair chromatography; lake ecosystem; limit of quantitation; macromolecule; mathematical model; microbial activity; nonhuman; particle resuspension; pH measurement; reduction; reduction kinetics; relative density; salinity; sedimentology; sulfate reduction; total organic carbon; water sampling

Sustainable development of the Lake Baikal Region: a model territory for the world - Koptyug, Valentin A; Uppenbrink, Martin (Springer Science & Business Media, 2013)

Magnetostratigraphic determination of the age of ancient Lake Qinghai, and record of the East Asian monsoon since 4.63 Ma - Fu, Chaofeng; An, ZhiSheng; Qiang, Xiaoke; Bloemendal, Jan; Song, YouGui; Chang, Hong (Geology, 2013)
Lake Qinghai, in North China, is the largest interior plateau lake in Central Asia, and is sensitive to climate change and the environmental effects of Tibetan Plateau uplift. We have obtained an almost continuous 626 m long sediment core from an in-filled part of the southern lake basin, which documents both the age of the origin of the lake and the evolution of the East Asian monsoon during the Late Cenozoic. High-resolution magnetostratigraphy provides a chronology back to ca. 5.1 Ma. Analysis of lithofacies and depositional environments reveal that the change from eolian to lacustrine facies occurred at ca. 4.63 Ma, corresponding to a shift from an arid or semi-arid to a more humid climate, which resulted in the origin of Lake Qinghai. Changes in sediment lithology and mean grain size indicate that the lake level fluctuated considerably, superimposed on a long-term trend from higher to lower levels in response to variations in the East Asian Monsoon. This archive is a significant additional source of information on regional and global environmental change, complementing the existing records from north China, which are mainly based on analysis of loess deposits. © 2013 Geological Society of America.
Keywords: China; Qinghai; Qinghai Lake; Qinghai-Xizang Plateau; Climate change; Geochronology; Lithology; Sediments; Tectonics; Depositional environment; East Asian monsoon; Global environmental change; High resolution; Long-term trend; Magnetostratigraphy; Mean-grain size; Tibetan Plateau; age determination; Cenozoic; chronology; climate variation; depositional environment; environmental change; grain size; lithofacies; lithology; loess; magnetostratigraphy; monsoon; paleoclimate; sediment core; Lakes

Late Cretaceous (Campanian) provenance change in the Songliao Basin, NE China: Evidence from detrital zircon U-Pb ages from the Yaojia and Nenjiang Formations - Zhao, B.; Wang, C.; Wang, X.; Feng, Z. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2013)
In order to define the provenance change across the nonconformable boundary between the second and the third members of the Upper Cretaceous Nenjiang Formation (Campanian) in the north-central area of the Songliao Basin, two sandstone samples above (sample a-1 from the fourth member of the Nenjiang) and below (sample z-1 from the first member of the Yaojia Formation) the nonconformity were collected from core holes. U-Pb dating was performed on detrital zircons separated from the three sandstone samples. Detrital zircons from sample a-1 have dominant age populations of 100-110. Ma, 190-220. Ma, and . 1800. Ma, and sample z-1 has dominant ages of 130-150. Ma and . 350. Ma. This paper demonstrates that the provenance of the fourth member of the Nenjiang Formation is significantly different from the first member of the Coniacian Yaojia Formation. The provenance above the nonconformity became much more complex and the eastern source increased significantly, while the western source sharply declined. The main source areas of the fourth member of the Nenjiang Formation are mainly the Zhangguangcai Range, the eastern Lesser Xiang'an Range and the southeast of Songliao Basin. The dominant provenance of the first member of the Yaojia Formation is the northern, the central and the southern Great Xing'an Range. According to the depositional ages and combining the latest seismic stratigraphic profiles in the Songliao Basin, the tectonic inversion of the eastern Songliao Basin began between 73. Ma and 87. Ma, which differs from the previous age of 73. Ma. © 2012 Elsevier B.V.
cited By 43
Keywords: Campanian; detrital deposit; provenance; seismic stratigraphy; tectonic evolution; unconformity; uranium-lead dating; zircon; China; Da Hinggan Mountains; Heilongjiang; Nen Basin; Songliao Basin; Xiao Hinggan Mountains; Coniacian

Luminescence dating of the PASADO core 5022-1D from Laguna Potrok Aike (Argentina) using IRSL signals from feldspar - Buylaert, J.-P.; Murray, A.S.; Sohbati, R.; Ohlendorf, C.; Thiel, C.; Wastegård, S.; Zolitschka, B. (Quaternary Science Reviews, 2013)
We have measured and tested a luminescence chronology for the PASADO core 5022-1D from the maar lake of Laguna Potrok Aike. Because of unsuitable quartz OSL characteristics, sand-sized K-feldspar extracts were chosen as a dosimeter and the dose was measured using a post-IR IRSL (pIRIR290) measurement protocol. Using this approach we were able to access a stable signal and thus avoid the ubiquitous problem of feldspar signal instability. Extensive laboratory tests show that the chosen pIRIR290 protocol is applicable to these samples. We also developed a new criterion based on known relative bleaching rates of the conventional IRSL signal (IR50) and the pIRIR290 signal and the relationship between resulting equivalent doses; this is used to identify and reject poorly bleached samples. Eighteen samples out of 47 were rejected based on this criterion, without reference to absolute doses or stratigraphy; the resulting age-depth profile is self-consistent, increases smoothly with depth and is in agreement with independent age control based on volcanic ash layers (Recl'us, Mt Burney and Hudson tephras) at the top and middle of the core. Our new luminescence chronology suggests that the 5022-1D core reaches back to 65ka at 96m below lake floor. © 2013 Elsevier Ltd.
Keywords: Argentina; Laguna Potrok Aike; Santa Cruz [Argentina]; Bleaching; Cleaning; Feldspar; Lakes; Quartz; Stratigraphy; ICDP-project PASADO; Independent age control; K-feldspar; Laguna potrok aike; Luminescence dating; Measurement protocol; Post-IR IRSL; Signal instabilities; bleaching; chronology; feldspar; luminescence dating; signal; volcanic ash; Luminescence

Composition and origin of rhyolite melt intersected by drilling in the Krafla geothermal field, Iceland - Zierenberg, R.A.; Schiffman, P.; Barfod, G.H.; Lesher, C.E.; Marks, N.E.; Lowenstern, J.B.; Mortensen, A.K.; Pope, E.C.; Bird, D.K.; Reed, M.H.; Fridleifsson, G.Ó.; Elders, W.A. (Contributions to Mineralogy and Petrology, 2013)
The Iceland Deep Drilling Project Well 1 was designed as a 4- to 5-km-deep exploration well with the goal of intercepting supercritical hydrothermal fluids in the Krafla geothermal field, Iceland. The well unexpectedly drilled into a high-silica (76.5 % SiO2) rhyolite melt at approximately 2.1 km. Some of the melt vesiculated while extruding into the drill hole, but most of the recovered cuttings are quenched sparsely phyric, vesicle-poor glass. The phenocryst assemblage is comprised of titanomagnetite, plagioclase, augite, and pigeonite. Compositional zoning in plagioclase and exsolution lamellae in augite and pigeonite record changing crystallization conditions as the melt migrated to its present depth of emplacement. The in situ temperature of the melt is estimated to be between 850 and 920 °C based on two-pyroxene geothermometry and modeling of the crystallization sequence. Volatile content of the glass indicated partial degassing at an in situ pressure that is above hydrostatic ( 16 MPa) and below lithostatic ( 55 MPa). The major element and minor element composition of the melt are consistent with an origin by partial melting of hydrothermally altered basaltic crust at depth, similar to rhyolite erupted within the Krafla Caldera. Chondrite-normalized REE concentrations show strong light REE enrichment and relative flat patterns with negative Eu anomaly. Strontium isotope values (0.70328) are consistent with mantle-derived melt, but oxygen and hydrogen isotope values are depleted (3.1 and -118 ‰, respectively) relative to mantle values. The hydrogen isotope values overlap those of hydrothermal epidote from rocks altered by the meteoric-water-recharged Krafla geothermal system. The rhyolite melt was emplaced into and has reacted with a felsic intrusive suite that has nearly identical composition. The felsite is composed of quartz, alkali feldspar, plagioclase, titanomagnetite, and augite. Emplacement of the rhyolite magma has resulted in partial melting of the felsite, accompanied locally by partial assimilation. The interstitial melt in the felsite has similar normalized SiO2 content as the rhyolite melt but is distinguished by higher K2O and lower CaO and plots near the minimum melt composition in the granite system. Augite in the partially melted felsite has re-equilibrated to more calcic metamorphic compositions. Rare quenched glass fragments containing glomeroporphyritic crystals derived from the felsite show textural evidence for resorption of alkali feldspar and quartz. The glass in these fragments is enriched in SiO2 relative to the rhyolite melt or the interstitial felsite melt, consistent with the textural evidence for quartz dissolution. The quenching of these melts by drilling fluids at in situ conditions preserves details of the melt-wall rock interaction that would not be readily observed in rocks that had completely crystallized. However, these processes may be recognizable by a combination of textural analysis and in situ analytical techniques that document compositional heterogeneity due to partial melting and local assimilation. © 2012 Springer-Verlag.
cited By 51
Keywords: augite; basalt; chemical composition; deep drilling; emplacement; geothermal system; hydrogen isotope; hydrothermal fluid; partial melting; phenocryst; pigeonite; plagioclase; rare earth element; rhyolite; stable isotope; strontium isotope; titanomagnetite; zoning; Iceland; Krafla

Carbon-isotope stratigraphy from terrestrial organic matter through the monterey event, Miocene, New Jersey margin (IODP Expedition 313) - Fang, L.; Bjerrum, C.J.; Hesselbo, S.P.; Kotthoff, U.; McCarthy, F.M.G.; Huang, B.; Ditchfield, P.W. (Geosphere, 2013)
The stratigraphic utility of carbon-isotope values from terrestrial organic matter is explored for Miocene siliciclastic sediments of the shallow shelf, New Jersey margin, USA (Integrated Ocean Drilling Program [IODP] Expedition 313). These shallow marine strata, rich in terrestrial organic matter, provide a record of deposition equivalent to the Monterey event, a prolonged interval of time characterized by relatively positive carbon-isotope values recorded from foraminiferal carbonate in numerous oceanic settings. Coherent stratigraphic trends and short-term isotopic excursions are observed consistently in palynological preparation residues, concentrated woody phytoclasts, and individually picked woody phytoclasts obtained from the New Jersey sediments. A bulk organic matter curve shows somewhat different stratigraphic trends but, when corrected for mixing of marine-terrestrial components on the basis of measured C/N ratios, a high degree of conformity with the woody phytoclast record is observed. However, assuming that the correlations based on strontium-isotope values and biostratigraphy are correct, the carbon-isotope record from the New Jersey margin contrasts with that previously documented from oceanic settings (i.e., lack of positive excursion of carbonisotope values in terrestrial organic matter through the Langhian Stage). Factors that may potentially bias local terrestrial carbonisotope records include reworking from older deposits, degradation and diagenesis, as well as environmental factors affecting vegetation in the sediment source areas. These possible factors are assessed on the basis of pyrolysis data, scanning electron microscope observations, and comparison to palynological indices of environmental change. Some evidence is found for localized degradation and/or reworking of older woody phytoclasts, but where such processes have occurred they do not readily explain the observed carbon-isotope values. It is concluded that the overall carbon-isotope signature for the exchangeable carbon reservoir is distorted, to the extent that the Monterey event excursion is not easily identifiable. The most likely explanation is that phytoclast reworking has indeed occurred in clinoform toe-ofslope facies, but the reason for the resulting relatively heavy carbon-isotope values in the Burdigalian remains obscure. © 2013 Geological Society of America.
cited By 8
Keywords: carbon isotope; deposition; environmental factor; Miocene; mixing; organic matter; palynology; pyrolysis; shelf sediment; siliciclastic deposit; stratigraphy; strontium isotope; New Jersey; United States

Characterisation and isotopic evolution of saline waters of the Outokumpu Deep Drill Hole, Finland - Implications for water origin and deep terrestrial biosphere - Kiet{av{ainen, Riikka; Ahonen, Lasse; Kukkonen, Ilmo T.; Hendriksson, Nina; Nyyss{onen, Mari; It{avaara, Merja (Applied Geochemistry, 2013)

Chronology of Lake El'gygytgyn sediments – a combined magnetostratigraphic, palaeoclimatic and orbital tuning study based on multi-parameter analyses - Nowaczyk, N. R.; Haltia, E. M.; Ulbricht, D.; Wennrich, V.; Sauerbrey, M. A.; Rosen, P.; Vogel, H.; Francke, A.; Meyer-Jacob, C.; Andreev, A. A.; Lozhkin, A. V. (Climate of the Past, 2013)

Chronology of Lake El’gygytgyn sediments – A combined magnetostratigraphic, palaeoclimatic and orbital tuning study based on multi-parameter analyses - Nowaczyk, N.R.; Haltia, E.M.; Ulbricht, D.; Wennrich, V.; Sauerbrey, M.A.; Rosen, P.; Vogel, H.; Francke, A.; Meyer-Jacob, C.; Andreev, A.A.; Lozhkin, A.V. (Climate of the Past, 2013)
A 318-metre-long sedimentary profile drilled by the International Continental Scientific Drilling Program (ICDP) at Site 5011-1 in Lake El’gygytgyn, Far East Russian Arctic, has been analysed for its sedimentologic response to global climate modes by chronostratigraphic methods. The 12 km wide lake is sited off-centre in an 18 km large crater that was created by the impact of a meteorite 3.58 Ma ago. Since then sediments have been continuously deposited. For establishing their chronology, major reversals of the earth’s magnetic field provided initial tie points for the age model, confirming that the impact occurred in the earliest geomagnetic Gauss chron. Various stratigraphic parameters, reflecting redox conditions at the lake floor and climatic conditions in the catchment were tuned synchronously to Northern Hemisphere insolation variations and the marine oxygen isotope stack, respectively. Thus, a robust age model comprising more than 600 tie points could be defined. It could be shown that deposition of sediments in Lake El’gygytgyn occurred in concert with global climatic cycles. The upper ∼ 160 m of sediments represent the past 3.3 Ma, equivalent to sedimentation rates of 4 to 5 cm ka−1, whereas the lower 160 m represent just the first 0.3 Ma after the impact, equivalent to sedimentation rates in the order of 45 cm ka−1. This study also provides orbitally tuned ages for a total of 8 tephras deposited in Lake El’gygytgyn. © Author(s) 2013.
cited By 53

Chronology of the terrestrial Upper Cretaceous in the Songliao Basin, northeast Asia - Deng, C.L.; He, H.Y.; Pan, Y.X.; Zhu, R.X. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2013)
The Cretaceous was a period of great environmental, biological and geodynamical change, but a paucity of an accurate time frame for continental strata has prevented our understanding of the terrestrial processes and the integration of marine and terrestrial records. Here we present an integrated chronology for the terrestrial Upper Cretaceous in East Asia based on new high-resolution magnetostratigraphic results and previously published SIMS U-Pb zircon analyses of the Cretaceous Continental Scientific Drilling borehole sequence from the Songliao Basin in northeast China (hereafter termed CCSD-SK-I), which consists of a sedimentary sequence from the upper Quantou Formation (K2q) to the Mingshui Formation (K2m). Correlation to the geomagnetic polarity timescale was achieved by combining magnetostratigraphic and SIMS U-Pb zircon geochronologic data, and lithostratigraphy. Our correlation suggests that the CCSD-SK-I sedimentary sequence spans from the upper chron C34n to chron C29r. The age of the sedimentary sequence from the upper Quantou Formation (K2q) to the Mingshui Formation (K2m) in the Songliao Basin can thus be constrained to an interval from the Turonian to the Maastrichtian ages. In addition, our correlation puts the Cretaceous-Paleogene boundary in the upper part of Member 2 of the Mingshui Formation (K2m2). The constructed comprehensive chronology allows the precise correlation of the terrestrial Upper Cretaceous of the Songliao Basin to marine strata as well as other continental sequences. © 2012 Elsevier B.V.
cited By 116
Keywords: borehole; Cretaceous-Tertiary boundary; drilling; geochronology; geodynamics; geological record; geomagnetic field; lithostratigraphy; Maastrichtian; magnetostratigraphy; sedimentary sequence; stratigraphic correlation; Turonian; uranium-lead dating; China; Songliao Basin

Clay mineralogy of the middle Mingshui Formation (upper Campanian to lower Maastrichtian) from the SKIn borehole in the Songliao Basin, NE China: Implications for palaeoclimate and provenance - Gao, Y.; Wang, C.; Liu, Z.; Zhao, B.; Zhang, X. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2013)
Clay mineralogy of a 60. m thick section of the middle Mingshui Formation (upper Campanian to lower Maastrichtian) from the SKIn borehole (Songliao Basin in NE China) has been studied to assess the palaeoclimate and provenance. The sedimentary succession is composed of shore to shallow lacustrine mudstones and siltstones in the lower part, and meandering fluvial sandstone-mudstone sequences in the upper part. The clay mineral assemblage is characterized by the predominance of smectitic minerals, with some exceptions of illite-rich layers, and trace amounts of kaolinite and chlorite. The high smectite content (>. 90% on average) in lacustrine sediments could source from erosion of smetitic soils and volcanic materials in source areas. The Lesser Xing'an-Zhangguangcai Range was the potential provenance area for the sediments, with volcanic activity occurring at . 70. Ma, when the temperate semi-humid palaeoclimate was favorable for the clay formation. Smectite presented in meandering fluvial sandstones is of early diagenetic origin, formed by hydrolysis and alteration of primary minerals after deposition. Illite in overbank deposits is interpreted as a result of erosion of granitic rocks and sorting in sedimentation processes. The clay mineralogy of the studied strata contains information on palaeoclimate and provenance, although early diagenetic processes may have influenced the mineralogical composition in some intervals of sandstones. © 2012 Elsevier B.V.
cited By 27
Keywords: Campanian; diagenesis; hydrolysis; illite; kaolinite; lacustrine deposit; Maastrichtian; mudstone; paleoclimate; provenance; siltstone; smectite; China; Heilongjiang; Xiao Hinggan Mountains

Climate induced changes as registered in inorganic and organic sediment components from Laguna Potrok Aike (Argentina) during the past 51ka - Hahn, A.; Kliem, P.; Ohlendorf, C.; Zolitschka, B. (Quaternary Science Reviews, 2013)
Total organic carbon, total inorganic carbon, biogenic silica content and total organic carbon/total nitrogen ratios of the Laguna Potrok Aike lacustrine sediment record are used to reconstruct the environmental history of south-east Patagonia during the past 51ka in high resolution. High lake level conditions are assumed to have prevailed during the Last Glacial, as sediments are carbonate-free. Increased runoff linked to permafrost and reduced evaporation due to colder temperatures and reduced influence of Southern Hemispheric Westerlies (SHW) may have caused these high lake levels with lake productivity being low and organic matter mainly of algal or cyanobacterial origin. Aquatic moss growth and diatom blooms occurred synchronously with southern hemispheric glacial warming events such as the Antarctic A-events, the postglacial warming following the LGM and the Younger Dryas chronozone. During these times, a combination of warmer climatic conditions with related thawing permafrost could have increased the allochthonous input of nutrients and in combination with warmer surface waters increased aquatic moss growth and diatom production. The SHW were not observed to affect southern Patagonia during the Last Glacial. The Holocene presents a completely different lacustrine system because (a) permafrost no longer inhibits infiltration nor emits meltwater pulses and (b) the positioning of the SHW over the investigated area gives rise to strong and dry winds. Under these conditions total organic carbon, total organic carbon/total nitrogen ratios and biogenic silica cease to be first order productivity indicators. On the one hand, the biogenic silica is influenced by dissolution of diatoms due to higher salinity and pH of the lake water under evaporative stress characterizing low lake levels. On the other hand, total organic carbon and total organic carbon/total nitrogen profiles are influenced by reworked macrophytes from freshly exposed lake level terraces during lowstands. Total inorganic carbon remains the most reliable proxy for climatic variations during the Holocene as high precipitation of carbonates can be linked to low lake levels and high autochthonous production. The onset of inorganic carbon precipitation has been associated with the southward shift of the SHW over the latitudes of Laguna Potrok Aike. The refined age-depth model of this record suggests that this shift occurred around 9.4cal.kaBP. © 2012 Elsevier Ltd.
Keywords: Argentina; Laguna Potrok Aike; Patagonia; Santa Cruz [Argentina]; algae; Bacillariophyta; Bryophyta; Cyanobacteria; Biogeochemistry; Biological materials; Carbonates; Fourier transform infrared spectroscopy; Glacial geology; Lakes; Nitrogen; Permafrost; Phytoplankton; Sediments; Silica; Argentina; Biogenic silica; Diffuse reflectance fourier transform infrared; ICDP project PASADO; Lake levels; Patagonia; Primary productivity; algal bloom; allochthon; carbon; carbonate; climate change; climate conditions; FTIR spectroscopy; global warming; growth rate; infiltration; latitude; moss; paleoenvironment; permafrost; primary production; proxy climate record; reconstruction; sediment analysis; silica; Southern Hemisphere; surface water; temperature effect; Organic carbon

Climatic variability during the last interglacial inferred from geochemical proxies in the Lake El'gygytgyn sediment record - Cunningham, L.; Vogel, H.; Nowaczyk, N.; Wennrich, V.; Juschus, O.; Persson, P.; Rosen, P. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2013)
The Last Interglacial Period (LIP) is often regarded as a good analogue for potential climatic conditions under predicted global warming scenarios. Despite this, there is still debate over the nature, duration and frequency of climatic changes during this period. One particularly contentious issue has been the apparent evidence of climatic instability identified in many marine cores but seemingly lacking from many terrestrial archives, especially within the Arctic, a key region for global climate change research. In this paper, geochemical records from Lake El'gygytgyn, north-eastern Russia, are used to infer past climatic changes during the LIP from within the high Arctic. With a sampling resolution of . 20- . 90. years, these records offer the potential for detailed, high-resolution palaeoclimate reconstruction. This study shows that the LIP commenced in central Chukotka . 129. thousand years ago (ka), with the warmest climatic conditions occurring between . 128 and 127. ka before being interrupted by a short-lived cold reversal. Mild climatic conditions then persisted until . 122. ka when a marked reduction in the sedimentation rate suggests a decrease in precipitation. A further climatic deterioration at . 118. ka marks the return to glacial conditions. This study highlights the value of incorporating several geochemical proxies when inferring past climatic conditions, thus providing the potential to identify signals related to environmental change within the catchment. We also demonstrate the importance of considering how changes in sedimentation rate influence proxy records, in order to develop robust palaeoenvironmental reconstructions. © 2013 Elsevier B.V.
cited By 8
Keywords: climate variation; geochemical method; global warming; Last Interglacial; marine record; paleoenvironment; paleolimnology; primary production; reconstruction; sediment core; sedimentation rate; Chukchi; Elgygytgyn Lake; Russian Federation

CO2 discharge in an active, non-volcanic continental rift area (Czech Republic): Characterisation (δ13C, 3He/4He) and quantification of diffuse and vent CO2 emissions - K{ampf, Horst; Br{auer, Karin; Schumann, Jens; Hahne, Kai; Strauch, Gerhard (Chemical Geology, 2013)
In the western Eger Rift (ER) area along the Počatky-Plesn'a fault zone (PPZ) CO2 degassing occurs predominantly within two mofette fields Bubl'ak and Hartoušov. We studied 27 wet mofettes belonging to these mofette fields for gas emission rates repeatedly between 2007 and 2009 and selected mofettes for gas composition and isotope ratios (δ13C, 3He/4He). Detailed ground mapping along the PPZ provided further two separated diffuse degassing structures (DDS) within the mofette fields Hartoušov and Bubl'ak. The DDS Hartoušov was studied in detail by measurements of 682 CO2 soil gas concentrations, 762 CO2 soil gas fluxes (max. 10 grid spacing) and partly by analyses of isotope ratios (13C/12C, 3He/4He) of soil gas. At the DDS Hartoušov the total CO2 soil flux yielded 1.559tm-2d-1 in spring 2009 and the CO2 emission rate at the wet mofettes of Hartoušov mofette field yielded 0.62td-1. The total CO2 discharge of the 27 wet mofettes was 3.75t d-1.At sites with high CO2 soil flux, the portion of mantle-derived helium is in the same range as the releasing at wet mofettes; both cover the signature of the subcontinental mantle. Also, the δ13C values analysed in the gas releasing from wet mofettes and those analysed in soil gas are nearly the same. Taking in account a biogenic soil CO2 flux of 25gm-2d-1 as background, the mantle-derived CO2 flux yielded approximately 1566tm-2d-1. As a result of the CO2 flux mapping of the DDS Hartoušov, it could be proved that 97.4% of the released soil CO2 (1.518tm-2d-1) stems from sites with CO2 fluxes higher than 500gm-2d-1-pointing to dominantly fault-related CO2 release.At the central mofette Bubl'ak (B2), the gas emission rate was determined for the first time in 1993. Measurements repeated between 2007 and 2009 showed a clear increase in the gas emission rate of more than 40%, correlating well with the increase of the 3He/4He ratios from 5Ra to approximately 6Ra between 1993 and 2008 at this location (Br{auer et al., 2009).The Bubl'ak mofette field is characterised by the highest CO2 emission rate along the PPZ, and in combination with the helium isotope signature of the European subcontinental mantle, this area was identified as a deep-reaching fluid injection zone. © 2012 Elsevier B.V.
Keywords: Czech Republic; Degassing; Gas emissions; Geologic models; Helium; Isotopes; Particulate emissions; Radium; Soils; C values; Continental rift; Czech Republic; Diffuse degassing; Eger Rift; Emission rates; Fault zone; Fluid injections; Gas compositions; Gas emission rates; Gas releasing; Grid-spacings; Ground mapping; Helium isotopes; Isotope ratio; Measurements of; Soil CO; Soil flux; Soil gas; Soil gas concentration; Subcontinental mantle; Total CO; carbon dioxide; carbon emission; carbon flux; degassing; diffusion; fluid injection; helium isotope; isotopic analysis; isotopic composition; isotopic ratio; rifting; soil gas; Carbon dioxide

Constraining clay hydration state and its role in active fault systems - Schleicher, A.M.; Hofmann, H. (Geochemistry, Geophysics, Geosystems, 2013)
To understand the role of hydrated clay minerals in active fault systems, a humidity chamber connected to an X-ray diffractometer was used to determine the adsorption of water onto and/or into the crystal structure of smectite. This new type of analysis was carried out under specific temperature and humidity conditions, using powdered clay size fractions (< 2 μm) of rock samples from the San Andreas Fault (USA) and the Nankai Trough (Japan). Pressure cannot be controlled, but does not significantly affect clay swelling at shallow conditions. Air-dried samples show a discrete smectite phase that swells after traditional ethylene glycolation to an interlayer distance of 1.5 and 1.7 nm. Using the humidity chamber, however, the samples show a shorter interlayer distance, between 1.09 and 1.54 nm. Based on our analysis, we show that (i) ethylene glycol overestimates the size of the interlayer space, and therefore water content, so is a crude maximum only; (ii) interlayer swelling occurs in smectite clay minerals at all temperatures between 25 and 95°C; and (iii) particle orientation increases with increasing humidity, indicating a higher mobility of smectite from interlayer hydration. Detailed characterization of the hydration state of smectite under original conditions is critical for understanding of clay-fluid interaction, the mechanical behavior during fault displacements, and fluid budgets at depth. We propose that humidity chamber experiments should be the new standard procedure to constrain swelling characteristics of natural and synthetic clay minerals. © 2013. American Geophysical Union. All Rights Reserved.
cited By 18
Keywords: Clay minerals; Ethylene; Ethylene glycol; Particle size analysis; Strike-slip faults; Tectonics; clay-hydration; Humidity chambers; NanTroSEIZE; SAFOD; Smectites; Hydration; active fault; adsorption; crystal structure; displacement; experimental mineralogy; humidity; hydration; San Andreas Fault; smectite; swelling; temperature effect; water; water content; Japan; Nankai Trough; Pacific Ocean; United States

Can alteration experiments on impact melts from El'gygytgyn and volcanic glasses shed new light on the formation of the Martian surface? - Hellevang, H.; Dypvik, H.; Kalleson, E.; Pittarello, L.; Koeberl, C. (Meteoritics and Planetary Science, 2013)
This investigation involved three specimens: an altered felsic sample of impactite from the ICDP El'gygytgyn drill core D1c, and two reference volcanics from Iceland, namely a rhyolitic glass and a basaltic glass. The goal of this work was to better understand the alteration of impact melt and volcanic glass, and to apply the results to an investigation of alteration processes below the surface of Mars. Hydrothermal batch alteration experiments with the El'gygytgyn sample showed formation of various silica phases such as cristobalite, opal, and quartz. According to geochemical modeling, zeolites were also expected, but zeolite minerals already present in the impactite prior to the experiment may have masked possible experimental zeolite growth. Basaltic glass was altered to smectite, talc, and opal. The accompanying numerical modeling gave results that were similar or comparable to the laboratory experiments. Rhyolitic glass was kinetically more stable than basaltic glass, and showed only minor formation of calcite and feldspar during the 3-week experiment. The study showed that closed-system isochemical alteration of both siliceous and mafic glasses and melts results in the formation of smectites and zeolites. Therefore, to link alteration features on Mars to specific physical conditions, the exact identity of the mineral phases present in surface rocks must be known. Moreover, our simulations on closed-system isochemical alteration showed that the fraction of zeolites and silica formed relative to smectite depends on the source mineral altered. Therefore, fractions of these mineral groups present in the Martian soil may be used to better predict source rock characteristics. © The Meteoritical Society, 2013.
cited By 9

Continental Scientific Drilling Project of Cretaceous Songliao Basin: Scientific objectives and drilling technology - Feng, Z.; Wang, C.; Graham, S.; Koeberl, C.; Dong, H.; Huang, Y.; Gao, Y. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2013)
The Continental Scientific Drilling Project at the Cretaceous-age Songliao Basin is a drilling initiative under the framework of the International Continental Scientific Drilling Program, to recover a nearly complete Cretaceous terrestrial sedimentary record in the Songliao Basin, northeastern China. The recovered cores will provide unique opportunities for the geosciences community to advance the understanding of climate change in the Cretaceous greenhouse world, and provide a documentation of geological events relevant to the carbon cycle during this time period.This drilling project will address significant geological questions, such as the identification of important stratigraphic boundaries and the marine-terrestrial correlations of stratigraphy, the reasons for the biotic response to the terrestrial environmental changes, the terrestrial response to the Cretaceous oceanic anoxic events, the formation of terrestrial petroleum source rocks, and the mechanisms for the Cretaceous magnetic Normal Superchron (CNS).In the first stage of this drilling project, the SKI drilling, rock cores of 2485.89. m in total length were recovered and the recovery ratio reached 96.46%. A series of drilling and coring technologies including regular, confined, directional, and sealed coring, were utilized to ensure a higher recovery ratio for the core, and will be described at the end of this paper. Well loggings were conducted right after coring. Core handling and storage were arranged in such a way that the scientific research was conducted on half of each core, whereas the other half of each core was preserved for long-term storage. The upcoming second stage, the SKII drilling, will combine with data from the existing SKI to provide complete high-resolution climate records of the terrestrial environment for the whole Cretaceous time period. © 2012 Elsevier B.V.
cited By 46
Keywords: carbon cycle; climate variation; Cretaceous; drilling; geological record; proxy climate record; sedimentary basin; sedimentary sequence; source rock; stratigraphic boundary; stratigraphic correlation; timescale; China; Songliao Basin

Continuous mapping of p wave velocity dispersion - A useful tool for reservoir characterization - Sun, L.F.; Campbell, A.; Milkereit, B. (75th European Association of Geoscientists and Engineers Conference and Exhibition 2013 Incorporating SPE EUROPEC 2013: Changing Frontiers, 2013)
For reservoir rocks, P wave velocity dispersion may provide a potential link to rock physical properties. This requires continuous measurement of P wave velocity in a broad frequency band to determine the critical frequency of the attenuation mechanism. In this study, we measure P wave velocity dispersion continuously in sonic frequency range using broadband full-waveform multi-channel sonic logging data with the beam-forming and cross-correlation techniques. Results of the field data from 5L-38 Mallik gas hydrate research well have demonstrated the robustness of this method. The profile of P wave velocity dispersion matches very well with geological settings. The gas hydrate zones show very strong P wave velocity dispersion and a pronounced critical frequency around 15 kHz; weakly-laminated sediments also have strong P wave velocity dispersion with critical frequency lower than 5 kHz; P wave velocity dispersion in consolidated sediments is mild and gradual. In addition, the total magnitude of P wave velocity dispersion is positively correlated to resistivity and gas hydrate saturation. Therefore, continuous P wave velocity dispersion mapping can be a promising tool for reservoir characterization. Copyright © (2012) by the European Association of Geoscientists & Engineers All rights reserved.
cited By 2
Keywords: Acoustic logging; Acoustic wave velocity; Dispersion (waves); Gas hydrates; Hydration; Mapping; Wave propagation; Continuous mappings; Continuous measurements; Critical frequencies; Cross correlation techniques; Gas hydrate saturations; Laminated sediments; Reservoir characterization; Rock physical properties; Seismic waves

Contrast experiment about dissolution of feldspar in different freshwater diagenetic systems - Mei-gui, XU; Shao-nan, ZHANG; Mei-yan, FU; Xiao-cong, FAN (Geoscience, 2013)

Controls on seasonal variations of silicate weathering and CO2 consumption in two river catchments on the NE Tibetan Plateau - Zhang, Fei; Jin, Zhangdong; Li, Fuchun; Yu, Jinmin; Xiao, Jun (Journal of Asian Earth Sciences, 2013)
Water samples from the Buha and Shaliu Rivers, located on the semi-arid northeastern Tibetan Plateau, were collected weekly over a one year period. The major ionic compositions of water samples were measured and the daily contents of suspended particulate material (SPM) were monitored in both rivers in order to investigate the influence of lithology, climate and physical erosion on seasonal silicate weathering. In the Shaliu River, weathering of trace amounts of calcite contributes more than 50% of the Ca2+ and HCO3- to the river water. Through high-resolution variations of Ca2+ concentrations and elemental ratios, the signal of carbonate precipitation is captured at the end of monsoon in this river. The measured physical erosion rate is only 8.7-16.0mm/kyr in this semi-arid region, which is 2-3 orders of magnitude lower than that in the Himalaya and nearby regions.In contrast with several orders of magnitude in seasonal variations of silicate weathering rates in both catchments, the distinct lithology between the catchments only leads to a 15 times difference of annual net CO2 consumption. The correlation analysis shows that seasonal silicate weathering is strongly dependent on water discharge in the semi-arid area. The most important observation is that, unrecognized by the previous studies, both physical erosion rate and air temperature exhibit two distinct trends with silicate weathering rates (and net CO2 consumption) during the years. The two trends might suggest that temperature plays a more important role on the CO2 consumption rate before the mid-monsoon under a condition of low water discharge than that after the monsoon with a high water discharge. During the period before the mid-monsoon, the relationship between temperature and silicate weathering rate exhibits higher activation energy than after the mid-monsoon, suggesting a greater dissolution of uneasily weatherable minerals from groundwater, frozen soil, and/or dust input. The relationship between erosion and weathering during the period before the mid-monsoon indicates a faster increase of silicate weathering rate, because freezing erosion produces large amount of high surface area minerals. © 2012 Elsevier Ltd.
Keywords: Buha River; China; Qinghai; Qinghai-Xizang Plateau; Shaliu River; carbon dioxide; climate effect; erosion; ionic composition; lithology; river water; seasonal variation; silicate; suspended particulate matter; weathering

Corrigendum to “Impact of volcanism on the evolution of Lake Van II: Temporal evolution of explosive volcanism of Nemrut Volcano (eastern Anatolia) during the past ca. 0.4 Ma” [J. Volcanol. Geotherm. Res. 253 (2013), 15 –34] (S0377027312003587) (10.1016/j.jvolgeores.2012.12.009)) - Sumita, M.; Schmincke, H.-U. (Journal of Volcanology and Geothermal Research, 2013)
1 Corrections in Table 1 and Fig. 10 The attached Table 2 and Fig. 10 should replace the original Table 1 and Fig. 10. 1.1 Correction details in Table 2 1.2 Correction details in Fig. 10 2 Corrections in the text body The corrections in Table 2 necessitate the following slight changes in the text body (pages 22 –29) 4.1.8. (page 23): Replace “Pantelleritic rhyolite” with “Comenditic rhyolite”. 4.1.20. (page 27): Replace “Trachyte” with “Comenditic rhyolite”. 4.1.21. (page 28): Replace “Pantelleritic rhyolite” with “Comenditic rhyolite”. 4.2.3. (page 28): Replace “Comenditic rhyolite” with “Comenditic rhyolite to trachyte”. 4.2.4. (page 28): Replace “Pantelleritic rhyolite” with “Comenditic rhyolite”. 4.2.6. (page 29): Replace “Trachyte” with “Comenditic rhyolite”. © 2013 Elsevier B.V.
cited By 19

Coupled molybdenum, iron and uranium stable isotopes as oceanic paleoredox proxies during the Paleoproterozoic Shunga Event - Asael, Dan; Tissot, François LH; Reinhard, Christopher T; Rouxel, Olivier; Dauphas, Nicolas; Lyons, Timothy W; Ponzevera, Emmanuel; Liorzou, C'eline; Ch'eron, Sandrine (Chemical Geology, 2013)

Cretaceous paleogeography and paleoclimate and the setting of SKI borehole sites in Songliao Basin, northeast China - Wang, C.; Feng, Z.; Zhang, L.; Huang, Y.; Cao, K.; Wang, P.; Zhao, B. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2013)
As a paradigm of greenhouse climate in Earth's history, the Cretaceous provides significant rock records of global climate changes under conditions of greenhouse climate. The Songliao Basin, among the longest duration (85-90m.y.) of continental sedimentary basins, provides an excellent opportunity to recover a nearly complete Cretaceous terrestrial sedimentary record. Extensive lake deposits, ten-kilometers deep and covering an area of 260,000km2 of the Songliao Basin, provide unique, detailed records that can be tied to the global stratigraphic time scale, thereby improving our understanding of the continental paleoclimate and ecological system. The two coreholes at SKIs and SKIn sites were drilled into this basin and completed with a total length of 2485.89m of recovered core that spanned the complete middle-to-Upper Cretaceous strata in the basin. The unique geological setting of long-term continuous subsidence within the largest Cretaceous landmass in the world - makes the Cretaceous Songliao Basin of northeastern China an ideal place to study Cretaceous climate change on the continent. This paper reviews the literature on the paleogeography and paleoclimate of the northern East Asia and the Songliao Basin during the Cretaceous. Based on the climatologically sensitive deposits, oxygen isotope studies, and paleontology, the climate during the Cretaceous in the Songliao Basin was temperate and humid with relatively abundant rainfall. During the period, significant changes - four cooling, three warming, and three semiarid events - are generally consistent with the oxygen isotope data from East Asia, and the four cooling events, in Berriasian-Valanginian, Aptian-Albian, early Santonian, and Campanian-Maastrichtian, may be related to potential glaciations in Cretaceous. © 2012 Elsevier B.V.
cited By 202
Keywords: Albian; Aptian; Berriasian; borehole; cooling; geological record; glaciation; lacustrine deposit; literature review; oxygen isotope; paleoclimate; paleogeography; paleontology; sedimentary basin; subsidence; timescale; Valanginian; China; Songliao Basin

Crustal anisotropy in the eastern Sea of Marmara region in Northwestern Turkey - Eken, T.; Bohnhoff, M.; Bulut, F.; Can, B.; Aktar, M. (Bulletin of the Seismological Society of America, 2013)
The North Anatolia Fault Zone (NAFZ) is a transform zone 1600 km in length representing the plate boundary between the westward moving Anatolian Plate and stable Eurasia. Almost the entire fault zone has failed during the last century except for the Sea of Marmara section, which is located in direct vicinity to the city of Istanbul. In this study, we investigate the crustal anisotropy along the eastern Marmara section of the NAFZ based on shear-wave splitting. We measure seismic anisotropy parameters, namely, the fast polarization direction (PD) and time delay (TD), by analyzing local seismicity recorded at selected seismographs operated throughout the eastern Sea of Marmara region. Our shear-wave splitting (SWS) observations indicate a predominant northwest-southeast-oriented PD, which is subparallel to both the orientation of the regional SHmax in northwest Turkey and the local NAFZ strike along the Princes' Islands segment. Toward the south, at the Armutlu Peninsula, we find a different PD pattern reflecting local fault strikes, SHmax as well as strain asymmetry between different crustal blocks across the fault zone. Applying strict quality criteria enables us to identify robust, preferred fast PDs, which suggests that initially observed PD heterogeneities are sometimes caused by second-order effects in the data rather than by varying PDs. Comparing TD and hypocentral depth distribution, we find the depth extent of the anisotropy is confined to the uppermost 10-km depth of crust. We combine our SWS results with those from previous studies conducted along the San Andreas fault (SAF) and NAFZ in order to investigate the relation of angular deviations of the PDs from regional SHmax and local fault strikes with fault-zone distance. We find that fast PDs are mainly controlled by the local fault structure in close proximity to a fault zone (5 and 10 km) while they are controlled by crustal stress at off-fault locations (5 and 10 km).
cited By 23
Keywords: Angular deviations; Crustal anisotropy; Hypocentral depth; Northwestern Turkey; Polarization direction; Second order effect; Seismic anisotropy; Shear wave splitting; Shear waves; Strike-slip faults; Anisotropy; anisotropy; crustal structure; fault zone; North Anatolian Fault; plate boundary; San Andreas Fault; seismicity; wave splitting; Istanbul [Istanbul (PRV)]; Istanbul [Turkey]; Sea of Marmara; Turkey

Cymbella gravida sp. nov. A new lacustrine taxon from Santa Cruz, Argentina - Recasens, Cristina; Maidana, Nora I. (Diatom Research, 2013)

Carbon isotopic composition of isoprenoid tetraether in surface sediments of Lake Qinghai and surrounding soils - Lu, Hongxuan; Liu, Weiguo; Wang, Huanye; Zhang, Chuanlun L. (Organic Geochemistry, 2013)
Isoprenoid GDGTs (iGDGTs), along with their constituent biphytanyl moieties, are biomarkers for archaea. In order to obtain more information on identifying the carbon source and potential carbon assimilation pathway of archaea in surface sediments of Lake Qinghai and the surrounding soils, the stable carbon isotopic composition of iGDGT-derived biphytanes as well as its relationship with δ13C values of total organic carbon (TOC) and dissolved inorganic carbon (DIC) was investigated. The δ13C values of iGDGT-derived biphytanes ranged from -42.7‰ to -20.3‰. For example, the values for acyclic biphytanes (BP-0), the most abundant, varied from -25.0‰ to -22.1‰ in offshore sediments, -30.5‰ to -25.4‰ in surrounding soils and -42.7‰ to -32.0‰ in nearshore sediments. The wider variation than that of δ13CTOC (-26.9‰ to -25.1‰) in offshore sediments and that in surrounding soils indicated that δ13C values of BP-0 may be a sensitive indicator for examining the depositional environments between terrestrial and lacustrine systems. With average δ13C values of -23.6‰, crenarchaeol-derived biphytanes (BP-cren) in offshore sediments were enriched in 13C (ca. 3.6‰) relative to TOC. In addition, the carbon isotopic fractionation between BP-cren and DIC was -21.3‰, consistent with that reported for marine Thaumarchaeota. The enrichment in 13C relative to TOC and the similar carbon isotopic fractionation indicated that Thaumarchaeota in offshore sediments of Qinghai Lake are autotrophic. With average δ13C values of -29.2‰, BP-cren in surrounding soils was depleted by 0.9‰ to 12.8‰ in 13C relative to DIC. The quite large scatter in carbon isotopic fractionation between BP-cren and DIC indicated that the biomass of soil Thaumarchaeota originated from inorganic and organic carbon sources, suggesting a mixotrophic lifestyle. © 2013 Elsevier Ltd.
Keywords: China; Qinghai; Qinghai Lake; Isotopes; Lakes; Lipids; Microorganisms; Organic carbon; Sedimentology; Soils; Surficial sediments; Carbon assimilation; Carbon isotopic composition; Depositional environment; Dissolved inorganic carbon; Isotopic fractionations; Lacustrine systems; Sensitive indicator; Total Organic Carbon; biomarker; biomass; carbon isotope; depositional environment; eukaryote; isoprenoid; isotopic composition; lacustrine deposit; sediment pollution; soil pollution; Carbon

Branched and isoprenoid tetraether (BIT) index traces water content along two marsh-soil transects surrounding Lake Qinghai: Implications for paleo-humidity variation - Wang, Huanye; Liu, Weiguo; Zhang, Chuanlun L.; Liu, Zhonghui; He, Yuxin (Organic Geochemistry, 2013)
The BIT index represents the relative abundances of branched glycerol dialkyl glycerol tetraethers (bGDGTs) and the isoprenoid GDGT, crenarchaeol. While bGDGTs are produced mainly by soil (anaerobic) bacteria, crenarchaeol is known to be a biomarker for aerobic ammonia oxidation by chemolithoautotrophic Thaumarchaeota, particularly in the open ocean or lakes. Thus, the index in marine and lacustrine settings has been widely used as a proxy for soil input. Here, we have investigated GDGT distribution along two transects extending from the lake shore marsh to upland soils on the NE Qinghai-Tibetan plateau. The results show that soil water content (SWC) correlates positively with concentration of bGDGTs and negatively with concentration of crenarchaeol; consequently, there is a significant positive correlation between SWC and the BIT index. Our study highlights a new potential application of BIT as a humidity proxy in loess/soil and peat deposits. © 2013 Elsevier Ltd.
Keywords: China; Qinghai; Qinghai Lake; Qinghai-Xizang Plateau; Aerobic bacteria; Glycerol; Lipids; Soil moisture; Wetlands; Aerobic ammonia oxidations; Chemolithoautotrophic; Lake Qinghai; Positive correlations; Qinghai-Tibetan plateau; Relative abundance; Soil water content; Upland soil; bacterium; biomarker; humidity; isoprenoid; loess; marsh; open ocean; paleolimnology; peat soil; relative abundance; shore (nonmarine); soil water; upland region; water content; Lakes

DeepCHALLA: Two glacial cycles of climate and ecosystem dynamics from equatorial East Africa - Verschuren, D.; Olagod, D.O.; Rucina, S.M.; Odhengo, P.O. (Scientific Drilling, 2013)
cited By 8

A pollen-based biome reconstruction over the last 3.562 million years in the Far East Russian Arctic – New insights into climate – vegetation relationships at the regional scale - Tarasov, P.E.; Andreev, A.A.; Anderson, P.M.; Lozhkin, A.V.; Leipe, C.; Haltia, E.; Nowaczyk, N.R.; Wennrich, V.; Brigham-Grette, J.; Melles, M. (Climate of the Past, 2013)
The recent and fossil pollen data obtained under the frame of the multi-disciplinary international El'gygytgyn Drilling Project represent a unique archive, which allows the testing of a range of pollen-based reconstruction approaches and the deciphering of changes in the regional vegetation and climate. In the current study we provide details of the biome reconstruction method applied to the late Pliocene and Quaternary pollen records from Lake El'gygytgyn. All terrestrial pollen taxa identified in the spectra from Lake El'gygytgyn were assigned to major vegetation types (biomes), which today occur near the lake and in the broader region of eastern and northern Asia and, thus, could be potentially present in this region during the past. When applied to the pollen spectra from the middle Pleistocene to present, the method suggests (1) a predominance of tundra during the Holocene, (2) a short interval during the marine isotope stage (MIS) 5.5 interglacial distinguished by cold deciduous forest, and (3) long phases of taiga dominance during MIS 31 and, particularly, MIS 11.3. These two latter interglacials seem to be some of the longest and warmest intervals in the study region within the past million years. During the late Pliocene-early Pleistocene interval (i.e., ∼3.562-2.200 Ma), there is good correspondence between the millennial-scale vegetation changes documented in the Lake El'gygytgyn record and the alternation of cold and warm marine isotope stages, which reflect changes in the global ice volume and sea level. The biome reconstruction demonstrates changes in the regional vegetation from generally warmer/wetter environments of the earlier (i.e., Pliocene) interval towards colder/drier environments of the Pleistocene. The reconstruction indicates that the taxon-rich cool mixed and cool conifer forest biomes are mostly characteristic of the time prior to MIS G16, whereas the tundra biome becomes a prominent feature starting from MIS G6. These results consistently indicate that the study region supported significant tree populations during most of the interval prior to ∼2.730 Ma. The cold- and drought-tolerant steppe biome first appears in the reconstruction ∼3.298 Ma during the tundra-dominated MIS M2, whereas the tundra biome initially occurs between ∼3.379 and ∼3.378 Ma within MIS MG4. Prior to ∼2.800 Ma, several other cold stages during this generally warm Pliocene interval were characterized by the tundra biome. © Author(s) 2013. CC Attribution 3.0 License.
cited By 66
Keywords: biome; climate variation; cold tolerance; deciduous forest; drought stress; fossil assemblage; Holocene; interglacial; palynology; Pliocene; reconstruction; vegetation history; Arctic; Chukchi; Elgygytgyn Lake; Russian Far East; Russian Federation

5.1 FAR-DEEP core archive and database - Lepland, Aivo; Mesli, Melanie; Conze, Ronald; Fabian, Karl; Fallick, Anthony E; Kump, LR (Reading the Archive of Earth’s Oxygenation, 2013)

6.1 The imandra/varzuga Greenstone Belt - Melezhik, Victor A; Prave, Anthony R; Lepland, Aivo; Hanski, Eero J; Romashkin, Alexander E; Rychanchik, Dmitry V; Luo, Zhen-Yu; Sharkov, Evgenii V; Bogina, Maria M; Brasier, Alex T; et al. (Reading the Archive of Earth’s Oxygenation, 2013)

7.10 Chemical Characteristics of Sediments and Seawater - Kump, Lee R; Kuznetsov, Anton B; Gorokhov, Igor M; Melezhik, Victor A; Farkaš, Juraj; Chakrabarti, Ramananda; Jacobsen, Stein B; Reinhard, Christopher T; Lyons, Timothy W; Rouxel, Olivier; et al. (Reading the Archive of Earth’s Oxygenation: Volume 3: Global Events and the Fennoscandian Arctic Russia-Drilling Early Earth Project, 2013)

A 350 ka record of climate change from Lake El'gygytgyn, Far East Russian Arctic: refining the pattern of climate modes by means of cluster analysis - Frank, U.; Nowaczyk, N. R.; Minyuk, P.; Vogel, H.; Rosen, P.; Melles, M. (Climate of the Past, 2013)
Rock magnetic, biochemical and inorganic records of the sediment cores PG1351 and Lz1024 from Lake El'gygytgyn, Chukotka peninsula, Far East Russian Arctic, were subject to a hierarchical agglomerative cluster analysis in order to refine and extend the pattern of climate modes as defined by Melles et al. (2007). Cluster analysis of the data obtained from both cores yielded similar results, differentiating clearly between the four climate modes warm, peak warm, cold and dry, and cold and moist. In addition, two transitional phases were identified, representing the early stages of a cold phase and slightly colder conditions during a warm phase. The statistical approach can thus be used to resolve gradual changes in the sedimentary units as an indicator of available oxygen in the hypolimnion in greater detail. Based upon cluster analyses on core Lz1024, the published succession of climate modes in core PG1351, covering the last 250 ka, was modified and extended back to 350 ka. Comparison to the marine oxygen isotope (δ18O) stack LR04 (Lisiecki and Raymo, 2005) and the summer insolation at 67.5 °N, with the extended Lake El'gygytgyn parameter records of magnetic susceptibility (κLF), total organic carbon content (TOC) and the chemical index of alteration (CIA; Minyuk et al., 2007), revealed that all stages back to marine isotope stage (MIS) 10 and most of the substages are clearly reflected in the pattern derived from the cluster analysis. © Author(s) 2013.
cited By 10
Keywords: climate change; climate modeling; cluster analysis; hierarchical system; oxygen isotope; sediment core; statistical analysis; Arctic Ocean; Chukchi; Elgygytgyn Lake; Far East; Russian Federation

A biomarker record of Lake El'gygytgyn, Far East Russian arctic: Investigating sources of organic matter and carbon cycling during marine isotope stages 1-3 - Holland, A.R.; Petsch, S.T.; Castañeda, I.S.; Wilkie, K.M.; Burns, S.J.; Brigham-Grette, J. (Climate of the Past, 2013)
Arctic paleoenvironmental archives serve as sensitive recorders of past climate change. Lake El'gygytgyn (Far East Russian Arctic) is a high-latitude crater impact lake that contains a continuous sediment record influenced by neither glaciation nor glacial erosion since the time of impact 3.58 Ma ago. Prior research on sediments collected from Lake El'gygytgyn suggest times of permanent ice cover and anoxia corresponding to global glacial intervals, during which the sediments are laminated and are characterized by the co-occurrence of high total organic carbon, microscopic magnetite grains that show etching and dissolution, and negative excursions in bulk sediment organic matter carbon isotope (δ13C) values. Here we investigate the abundance and carbon isotopic composition of lipid biomarkers recovered from Lake El'gygytgyn sediments spanning marine isotope stages 1-3 to identify key sources of organic matter (OM) to lake sediments, to establish which OM sources drive the negative δ13C excursion exhibited by bulk sediment OM, and to explore if there are molecular and isotopic signatures of anoxia in the lake during glaciation. We find that during marine isotope stages 1-3, direct evidence for water column anoxia is lacking. A ∼4 ‰ negative excursion in bulk sediment δ13C values during the Local Last Glacial Maximum (LLGM) is accompanied by more protracted, higher magnitude negative excursions in n-alkanoic acid and n-alkanol δ13C values that begin 20 kyr in advance of the LLGM. In contrast, n-alkanes and the C30 n-alkanoic acid do not exhibit a negative δ13C excursion at this time. Our results indicate that the C24, C26 and C28 n-alkanoic acids do not derive entirely from terrestrial OM sources, while the C30 n-alkanoic acid at Lake El'gygytgyn is a robust indicator of terrestrial OM contributions. Overall, our results strongly support the presence of a nutrient-poor water column, which is mostly isolated from atmospheric carbon dioxide during glaciation at Lake El'gygytgyn. © 2013 Author(s).
cited By 15
Keywords: anoxic conditions; biomarker; carbon cycle; carbon isotope; climate change; glaciation; isotopic analysis; isotopic composition; lacustrine deposit; Last Glacial Maximum; marine environment; organic carbon; organic matter; paleoenvironment; sediment chemistry; water column; Chukchi; Elgygytgyn Lake; Russian Federation

A biomarker record of Lake El'gygytgyn, Far East Russian Arctic: investigating sources of organic matter and carbon cycling during marine isotope stages 1 –3 - Holland, A. R.; Petsch, S. T.; Castaneda, I. S.; Wilkie, K. M.; Burns, S. J.; Brigham-Grette, J. (Climate of the Past, 2013)

A biomarker study of depositional paleoenvironments and source inputs for the massive formation of Upper Cretaceous lacustrine source rocks in the Songliao Basin, China - Song, Z.; Qin, Y.; George, S.C.; Wang, L.; Guo, J.; Feng, Z. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2013)
The abundance and composition of total organic carbon, aliphatic and aromatic hydrocarbons including biomarkers, and the δ13C composition of total organic matter and individual compounds in core samples of the Nenjiang Formation from the SK-1 borehole of the Songliao Basin provide information on the paleoenvironmental conditions of lacustrine sediments formed during the Upper Cretaceous. The distribution of n-alkanes, and their δ13C composition, and 4-methylsteranes and dinosteranes in the first member of the Nenjiang Formation (K2n1) indicate that the organic matter largely originated from algal organisms and is dominated by types I and II kerogen. The occurrence of gammacerane, aryl isoprenoids isorenieratane and low pristane/phytane and diasterane/sterane ratios further suggest a salinity stratified water column associated with anoxic bottom waters, as well as possible photic zone oxygen depletion conditions during major source rock deposition of the K2n1. The organic geochemical data also indicate significantly different depositional environments for the second member of the Nenjiang Formation (K2n2) sediments, which are interpreted to have been deposited under a uniform salinity (non-stratified) oxic water column. Consequently, although the organic matter in the K2n2 sediments was largely derived from algal and bacterial sources, the kerogen types are dominantly IIb and III due to the oxidative degradation of organic matter, combined with a gradual increase in land-plant input. Furthermore, the occurrence and shift of two saw-toothed distribution patterns of the δ13C composition of C29 to C33 n-alkanes, with W and M patterns being isotopically heavy odd- and even-numbered alkanes, respectively, is suggestive of organic input shift or an unknown mechanism of carbon uptake or isotopic fractionation. In particular, the heavy even carbon numbered high molecular weight n-alkanes is rare and needs further investigation. © 2012 Elsevier B.V.
cited By 55
Keywords: biomarker; carbon isotope; core analysis; Cretaceous; depositional environment; isotopic fractionation; kerogen; lacustrine deposit; lacustrine environment; organic matter; paleoenvironment; source rock; water column; China; Nen Basin; Songliao Basin; algae; Bacteria (microorganisms); Embryophyta

A late glacial to holocene record of environmental change from Lake Dojran (Macedonia, Greece) - Francke, A.; Wagner, B.; Leng, M.J.; Rethemeyer, J. (Climate of the Past, 2013)

A plan for a 5 km-deep borehole at Reykjanes, Iceland, into the root zone of a black smoker on land - Fridleifsson, G.Ó.; Elders, W.A.; Bignall, G. (Scientific Drilling, 2013)
A summary workshop report describing the progress made so far by the Iceland Deep Drilling Project (IDDP) is presented below. The report provides recommendations concerning technical aspects related to deep drilling, and invites international participation in both the engineering and the scientific activities of the next phase of the IDDP. No issues were identified at the workshop that should rule out attempting the drilling, sampling and testing of the proposed IDDP-2 well. Although technically challenging, the consensus of the workshop was that the drilling of such a hot deep well, and producing potentially hostile fluids, is possible but requires careful contingency planning. The future well will be explored for supercritical fluid and/or superheated steam beneath the current production zone of the Reykjanes geothermal field in SW Iceland. This deep borehole will provide the first opportunity worldwide to directly investigate the root zone of a magma-hydrothermal system which is likely to be similar to those beneath the black smokers on the worldencircling mid-ocean rift systems. © Author(s) 2013.
cited By 9
Keywords: Contingency planning; Current production; Deep boreholes; Deep drilling; Iceland deep drilling projects; Scientific activity; Superheated steam; Technical aspects; Drilling fluids; Effluent treatment; Geothermal fields; Supercritical fluids; Boring

A pollen-based biome reconstruction over the last 3.562 million years in the Far East Russian Arctic – new insights into climate –vegetation relationships at the regional scale - Tarasov, P. E.; Andreev, A. A.; Anderson, P. M.; Lozhkin, A. V.; Leipe, C.; Haltia, E.; Nowaczyk, N. R.; Wennrich, V.; Brigham-Grette, J.; Melles, M. (Climate of the Past, 2013)

Authigenic, detrital and diagenetic minerals in the Laguna Potrok Aike sediment sequence - Nuttin, L.; Francus, P.; Preda, M.; Ghaleb, B.; Hillaire-Marcel, C. (Quaternary Science Reviews, 2013)
The 100m-long Laguna Potrok Aike sediment sequence yielded a record spanning the Last Glacial period to the Holocene. This paper presents and discusses two aspects of the mineralogy of the lake. The first aspect is based on a semi-quantitative X-ray diffraction analysis of bulk and clay mineralogical assemblages. Minor mineralogical changes are observed throughout the glacial section suggesting relatively uniform sediment sources. The transition into the Holocene is characterized by increasing fluxes of endogenic calcite thought to relate to lower lake levels. The second aspect is based on analysis of uranium-series disequilibria in diagenetic vivianite from the glacial section. U-series ages were expected to yield minimum ages for the host-sediment. Unfortunately, very little authigenic U is present in vivianite grains. The low primary productivity of the lake and thus low organic carbon fluxes might have prevented the development of strong redox gradients at the water-sediment interface and thus reduced diagenetic U-uptake into the sediment. One vivianite sample, at a 56.9m composite depth, yielded enough authigenic uranium to calculate a 230Th-age of 29.4±5.9ka (±2σ). This age is younger than the one indicated by the radiocarbon chronology. It is thus concluded that a relatively late diagenetic evolution of the U-Th system characterizes the recovered vivianite minerals. The authigenic U displays a very high excess in 234U (over 238U) with an activity ratio of 4.58±0.58 (±2σ). It suggests that it originates from the transfer of highly fractionated U from surrounding detrital minerals through very low U-content pore waters. © 2012 Elsevier Ltd.
Keywords: Argentina; Laguna Potrok Aike; Santa Cruz [Argentina]; Clay; Crystallography; Glacial geology; Lakes; Mineralogy; Sedimentology; Sediments; Uranium; X ray diffraction analysis; Argentina; ICDP-PASADO; Late quaternary; Paleoclimates; Vivianite; XRD; authigenesis; calcite; carbon flux; geochronology; Holocene; Last Glacial Maximum; mineral; mineralogy; primary production; radiocarbon dating; redox potential; vivianite; X-ray diffraction; Phosphate minerals

A two-steps stochastic inversion to estimate gas hydrate grades at the mallik field - Dubreuil-Boisclair, C.; Gloaguen, E.; Bellefleur, G.; Marcotte, D. (75th EAGE Conference and Exhibition Incorporating SPE EUROPEC 2013, 2013)
In the last decades, permafrost gas hydrates have beneficiated from an increasing attention among researchers and industries around the world. However, little work has been done on characterizing this resource at the reservoir scale. In this study, we used cutting edge stochastic inversion software and we developed a cascade stochastic Bayesian algorithm to simulate the gas hydrate grade (product of porosity and gas hydrate saturation) on a 3D seismic cube at the Mallik field, in the Mackenzie Delta, Canada. Firstly, the 3D seismic data are stochastically inverted for acoustic impedance leading to multiple high-resolution AI realizations conditioned to the seismic and the well-log data from wells 2L- and 5L-38. Secondly, a petrophysical inversion is performed in a stochastic Bayesian framework using gas hydrate grade logs as hard data, and randomly selected AI scenarios as secondary data. For the later inversion, an in-situ petrophysical relationship linking gas hydrate grades to acoustic impedance is built using upscaled well data. The results are thus multiple 3D gas hydrate grade realizations conditioned to all available data, and reflecting a great part of the model uncertainty. These models allow calculating the total gas volume with its associated uncertainty for the studied region.
cited By 0
Keywords: Acoustic impedance; Acoustic logging; Gases; Hydration; Petrophysics; Seismology; Stochastic systems; Uncertainty analysis; 3D seismic data; Bayesian algorithms; Bayesian frameworks; Gas hydrate saturations; High resolution; Model uncertainties; Petrophysical relationship; Secondary datum; Gas hydrates

A unique find of the earliest multicellular algae in the Lower Proterozoic (2.45 Ga) of the Kola Peninsula - Rozanov, A Yu; Astafieva, MM (Doklady Biological Sciences, 2013)

Age models for long lacustrine sediment records using multiple dating approaches - An example from Lake Bosumtwi, Ghana - Shanahan, Timothy M.; Peck, John A.; McKay, Nicholas; Heil, Clifford W.; King, John; Forman, Steven L.; Hoffmann, Dirk L.; Richards, David A.; Overpeck, Jonathan T.; Scholz, Christopher (Quaternary Geochronology, 2013)
The continuous 300-m long drill cores obtained from Lake Bosumtwi, Ghana represent one of the longest, continuous lacustrine sequences obtained from an extant lake, and contain an unprecedented record of late Quaternary climate change in West Africa. However, one of the main challenges associated with generating long paleoclimate time series from terrestrial records such as this is the development of accurate age-depth relationships because unlike marine records, lacustrine sequences cannot be tuned to global ice volume records via δ18O stratigraphy. The Lake Bosumtwi record thus offers an excellent case study for examining the potential and the challenges associated with different geochronological techniques in lacustrine systems. In the present study, we use a combination of radiocarbon, optically stimulated luminescence and U-series dating and paleomagnetic excursions to generate a chronology for the upper ca. 150 ka of sedimentation at Lake Bosumtwi and employ a Bayesian approach to generate a continuous age-depth relationship. The resultant chronology is then used to test the effectiveness of tuning of an environmental magnetic proxy for dust against a well-dated record of high latitude dust. Our approach highlights the advantages of using multiple dating approaches, and the dangers of relying on too few age constraints when dating long sedimentary sequences. However, the excellent agreement between the different approaches over most of the record suggest that well-constrained age-depth models for long sedimentary sequences can be produced using this combination of approaches. Furthermore, our data provide support for extending the chronology beyond the limit of radiocarbon, U-series and OSL in the future using paleomagnetic excursions/reversals and tuning against well-dated high latitude paleoclimate records. © 2012 Elsevier B.V.
Keywords: Ashanti; Ghana; Lake Bosumtwi; Bayesian analysis; chronology; climate variation; lacustrine deposit; paleoclimate; paleomagnetism; radiocarbon dating; sedimentary sequence; sedimentation; time series; uranium series dating

Amplified bioproductivity during Transition IV (332 000-342 000 yr ago): Evidence from the geochemical record of Lake El'gygytgyn - Cunningham, L.; Vogel, H.; Wennrich, V.; Juschus, O.; Nowaczyk, N.; Rosen, P. (Climate of the Past, 2013)
To date, terrestrial archives of long-term climatic change within the Arctic have widely been restricted to ice cores from Greenland and, more recently, sediments from Lake El'gygytgyn in northeast Arctic Russia. Sediments from this lake contain a paleoclimate record of glacialinterglacial cycles during the last three million years. Lowresolution studies at this lake have suggested that changes observed during Transition IV (the transition from marine isotope stage (MIS) 10 to MIS 9) are of greater amplitude than any observed since. In this study, geochemical parameters are used to infer past climatic conditions thus providing the first high-resolution analyses of Transition IV from a terrestrial Arctic setting. These results demonstrate that a significant shift in climate was subsequently followed by a rapid increase in biogenic silica (BSi) production. Following this sharp increase, bioproductivity remained high, but variable, for over a thousand years. This study reveals differences in the timing and magnitude of change within the ratio of silica to titanium (Si/Ti) and BSi records that would not be apparent in lower resolution studies. This has significant implications for the increasingly common use of Si/Ti data as an alternative to traditional BSi measurements. © Author(s) 2013.
cited By 9
Keywords: climate change; data acquisition; geochemical cycle; ice core; lacustrine environment; marine isotope stage; paleoclimate; record; silica; titanium; Arctic; Chukchi; Elgygytgyn Lake; Greenland; Russian Federation

Amplified bioproductivity during Transition IV (332 000 –342 000 yr ago): evidence from the geochemical record of Lake El'gygytgyn - Cunningham, L.; Vogel, H.; Wennrich, V.; Juschus, O.; Nowaczyk, N.; Rosen, P. (Climate of the Past, 2013)

An earthquake gap south of Istanbul - Bohnhoff, M.; Bulut, F.; Dresen, G.; Malin, P.E.; Eken, T.; Aktar, M. (Nature Communications, 2013)
Over the last century the North Anatolian Fault Zone in Turkey has produced a remarkable sequence of large earthquakes. These events have now left an earthquake gap south of Istanbul and beneath the Marmara Sea, a gap that has not been filled for 250 years. Here we investigate the nature of the eastern end of this gap using microearthquakes recorded by seismographs primarily on the Princes Islands offshore Istanbul. This segment lies at the western terminus of the 1999 Mw7.4 Izmit earthquake. Starting from there, we identify a 30-km-long fault patch that is entirely aseismic down to a depth of 10 km. Our evidence indicates that this patch is locked and is therefore a potential nucleation point for another Marmara segment earthquake - a potential that has significant natural hazards implications for the roughly 13 million Istanbul residents immediately to its north. © 2013 Macmillan Publishers Limited. All rights reserved.
cited By 94
Keywords: active fault; earthquake event; fault zone; Kocaeli earthquake 1999; microearthquake; nucleation; seismic hazard; seismograph; article; biological accident; correlation analysis; earthquake; Turkey (republic); Earthquakes; Geography; Humans; Islands; Oceans and Seas; Turkey; Istanbul [Turkey]; Sea of Marmara; Turkey

Assessing the ratio of archaeol to caldarchaeol as a salinity proxy in highland lakes on the northeastern Qinghai-Tibetan Plateau - Wang, Huanye; Liu, Weiguo; Zhang, Chuanlun L.; Jiang, Hongchen; Dong, Hailiang; Lu, Hongxuan; Wang, Jinxiang (Organic Geochemistry, 2013)
The ratio of archaeol to caldarchaeol (the ACE index) has been proposed recently as an index for paleosalinity reconstruction and is based principally on archaeal core lipids (CLs) from coastal salt pans (Turich, C., Freeman, K.H., 2011. Archaeal lipids record paleosalinity in hypersaline systems. Organic Geochemistry 42, 1147-1157). We have examined possible relationships between salinity and ACE in both CLs and intact polar lipids (IPLs) from suspended particulate matter (SPM) and surface sediments of lakes and surrounding soils on the northeastern Qinghai-Tibetan Plateau. Our results showed that ACE values were positively correlated with salinity in all samples; however, CL ACE values were systematically higher than IPL ACE values, probably due to different degradation kinetics of intact polar (IP) archaeol and IP caldarchaeol. On the other hand, surface sediment ACE values from both CLs and IPLs were lower than SPM ACE values, probably due to enhanced production of caldarchaeol relative to archaeol in the sediment. Our results demonstrate that the ACE proxy reflects changes in salinity in diverse environments on the Qinghai-Tibetan Plateau, which is promising for paleosalinity reconstruction; however, caution should be used when applying the salinity proxy before we have a better understanding of degradation kinetics of archaeal IPLs and in situ production of caldarchaeol and archaeol in sediments. © 2012 Elsevier Ltd.
Keywords: China; Qinghai-Xizang Plateau; Archaea; Degradation; Lakes; Lipids; Sedimentology; Surficial sediments; Archaeal; Degradation kinetics; Hypersaline; In-situ production; Northeastern Qinghai-Tibetan Plateau; Organic geochemistry; Polar lipids; Qinghai-Tibetan plateau; Surface sediments; Surrounding soils; Suspended particulate matters; correlation; dehydration; in situ measurement; in situ test; lake water; lipid; organic geochemistry; paleosalinity; saline lake; sampling; upland region; Salinity measurement

Astrochronology of the Early Turonian-Early Campanian terrestrial succession in the Songliao Basin, northeastern China and its implication for long-period behavior of the Solar System - Wu, H.; Zhang, S.; Jiang, G.; Hinnov, L.; Yang, T.; Li, H.; Wan, X.; Wang, C. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2013)
The first complete Early Turonian-Early Campanian lacustrine succession has been recovered from the SK-I south (SK-Is) borehole in the Songliao Basin (SLB), northeastern China. We conducted a detailed cyclostratigraphic study of natural gamma-ray (GR) log, thorium (Th) log, and magnetic susceptibility (MS) data from this core. Spectral analysis of the upper Quantou Formation (K2q3+4), Qingshankou Formation (K2qn), Yaojia Formation (K2y), and lower Nenjiang Formation (K2n1+2) reveals a hierarchy of meter- to decameter-scale cycling in the data. The wavelength ratios of the cycles in these stratigraphic units are 20:5:2:1, corresponding with those of Milankovitch cycle periods of 405kyr (long eccentricity):100kyr (short eccentricity):37kyr (obliquity):20kyr (precession), indicating astronomical control on sedimentation. An astronomical time scale (ATS) was established by tuning interpreted 405kyr cycles to a 405kyr orbital eccentricity target curve, and to four SIMS U-Pb zircon radioisotope ages. This 'absolute' ATS provides precise numerical ages for stratigraphic boundaries, biozones, geological and geophysical events, and serves as a basis for correlation of strata and events between marine and terrestrial systems. The ages of the C33r/C34n geomagnetic polarity boundary in K2n2 and three short reversal events in K2y are estimated as 83.633Ma, 84.819-84.862Ma, 84.982-85.092Ma and 85.240-85.629Ma, respectively. Long-period amplitude modulations in the obliquity and eccentricity bands of the 405-kyr-tuned GR-Th series provide strong evidence that long-period orbital forcing influenced climate change and depositional processes in the SLB. The extracted amplitude modulations provide evidence that the orbits of Earth and Mars were not in secular resonance, and were undergoing chaotic interactions during this time, although the modulations do not match those of recent astronomical models. © 2012 Elsevier B.V.
cited By 122
Keywords: amplitude; astronomy; astrophysics; borehole; Campanian; cyclostratigraphy; eccentricity; geomagnetic field; lacustrine environment; magnetic susceptibility; Milankovitch cycle; orbital forcing; paleoenvironment; secular variation; solar system; spectral analysis; stratigraphic correlation; timescale; Turonian; uranium-lead dating; China; Nen Basin; Songliao Basin

Lithostratigraphy of the impactite and bedrock section of ICDP drill core D1c from the El'gygytgyn impact crater, Russia - Raschke, U.; Reimold, W.U.; Zaag, P.T.; Pittarello, L.; Koeberl, C. (Meteoritics and Planetary Science, 2013)
In 2008/2009, the International Continental Scientific Drilling Program (ICDP) obtained drill cores from the El'gygytgyn impact structure located on the Chukotka Peninsula (Russia). These cores provide the most complete geological section ever obtained from an impact structure in siliceous volcanic rock. The lithostratigraphy comprises a thick sequence of lacustrine sediments overlying impact breccias and deformed target rock. The interval from 316 m (below lake floor-blf) to the end of the core at 517 m depth can be subdivided into four lithological sequences. At 316 m depth, the first mesoscopic clasts of shocked target rock occur in lacustrine sediments. The growing abundance of target rock clasts with increasing depth and corresponding decrease of lacustrine sediment components indicate the extent of this transition zone to 328 m depth. It constitutes a zone of mixed reworked impact breccia and lacustrine sediments. Volcanic clasts in this reworked suevite section show all stages of shock metamorphism, up to melting. The underlying unit (328-390 m depth) represents a suevite package, a polymict impact breccia, with considerable evidence of shock deformation in a wide variety of volcanic clasts. This includes fragments with quartz that exhibit planar fractures and planar deformation features (PDF). In addition, at three depths, several centimeter-sized clasts with shatter cones were detected. Due to microanalytical identification of relatively rare, microscopic impact melt particles in the matrix of this breccia, this material can be confidently labeled a suevite. Also in this sequence, three unshocked, <1 m thick intersections of volcanic blocks occur at 333.83, 351.52, and 383.00 m depths. The upper bedrock unit begins at 390.74 m depth, has a thickness of 30.15 m, and represents a sequence of different volcanic rocks-an upper part with basaltic composition from 390.74 to 391.79 m depth overlying a lower, rhyodacitic part from 391.79 to 420.27 m depth. This (parautochthonous) basement unit is only very weakly affected by the impact: only one shocked quartz grain with two sets of PDF was recorded at 391.33 m depth. The lower bedrock unit (420.89-517.09 m depth [end of core]) is a brittly deformed, rather homogeneous welded ignimbrite that in part can be considered a cataclasite. The top three meters of this section are sheared, which could represent pre-impact tectonic deformation. A 54 cm thick injection of polymict impact breccia occurs at 471.42-471.96 m depth. © The Meteoritical Society, 2013.
cited By 21

Autecology of the extant ostracod fauna of Lake Ohrid and adjacent waters - A key to paleoenvironmental reconstruction - Lorenschat, Julia; Schwalb, Antje (Belgian Journal of Zoology, 2013)
Understanding the ecology of bioindicators such as ostracods is essential in order to reconstruct past environmental and climate change from analysis of fossil assemblages preserved in lake sediment cores. Knowledge of the ecology of ancient Lake Ohrid's ostracod fauna is very limited and open to debate. In advance of the Ohrid ICDP-Drilling project, which has potential to generate high-resolution long-term paleoenvironmental data of global importance in paleoclimate research, we sampled Lake Ohrid and a wide range of habitat types in its surroundings to assess 1) the composition of ostracod assemblages in lakes, springs, streams, and shortlived seasonal water bodies, 2) the geographical distribution of ostracods, and 3) the ecological characteristics of individual ostracod species. In total, 40 species were collected alive, and seven species were preserved as valves and empty carapaces. Of the 40 ostracod species, twelve were endemic to Lake Ohrid. The most common genus in the lake was Candona, represented by 13 living species, followed by Paralimnocythere, represented by fve living species. The most frequent species was Cypria obliqua. species with distinct distributions included Heterocypris incongruens, Candonopsis kingsleii, and Cypria lacustris. The most common species in shallow, fooded areas was H. incongruens, and the most prominent species in ditches was C. kingsleii. C. lacustris was widely distributed in channels, springs, lakes, and rivers. statistical analyses were performed on a Lake Ohrid dataset, comprising the subset of samples from Lake Ohrid alone, and an entire dataset comprising all samples collected. The unweighted pair group mean average (UPGMA) clustering was mainly controlled by species-specifc depth preferences. Canonical Correspondence Analysis (CCA) with forward selection identifed water depth, water temperature, and pH as variables that best explained the ostracod distribution in Lake Ohrid. The lack of signifcance of conductivity and dissolved oxygen in CCA of Ohrid data highlight the uniformity across the lake of the well-mixed waters. In the entire area, CCA revealed that ostracod distribution was best explained by water depth, salinity, conductivity, pH, and dissolved oxygen. salinity was probably selected by CCA due to the presence of Eucypris virens and Bradleystrandesia reticulata in short-lived seasonal water bodies. Water depth is an important, although indirect, infuence on ostracod species distribution, which is probably associated with other factors such as sediment texture and food supply. some species appeared to be indicators for multiple environmental variables, such as lake level and water temperature.
Keywords: Lake Ohrid; autecology; endemism; fossil assemblage; geographical distribution; lacustrine deposit; lake water; multivariate analysis; ostracod; paleoclimate; paleoenvironment; reconstruction; sediment core; water temperature

Dating the termination of the Palaeoproterozoic Lomagundi-Jatuli carbon isotopic event in the North Transfennoscandian Greenstone Belt - Martin, Adam P; Condon, DJ; Prave, Anthony R; Melezhik, Victor A; Lepland, Aivo; Fallick, Anthony E (Precambrian Research, 2013)
Existing radio-isotopic age constraints indicate that the global Palaeoproterozoic Lomagundi-Jatuli large, positive carbonate carbon isotopic excursion, with δ13C values >+5‰, occurred between 2.2 and 2.06Ga. In the North Transfennoscandian Greenstone Belt of the Kola Peninsula, NW Russia, northern Norway and Finland, the Lomagundi-Jatuli Event is recorded in the carbonate rocks of the Umba and Kuetsj{arvi Sedimentary Formations in the Imandra-Varzuga and Pechenga greenstone belts. In both areas, thick mafic volcanic units (Umba and Kuetsj{arvi Volcanic Formations) overlie the carbon isotopic excursion-bearing sedimentary units. Overlying and younger sedimentary units contain carbonate rocks with δ13C values typically ranging between c. -1 and +3‰, signalling the termination of the Lomagundi-Jatuli excursion.Two new U-Pb ID-TIMS (isotope-dilution thermal ionisation mass spectrometry) zircon dates constrain this termination in both successions. The lower unit of the Il'mozero Sedimentary Formation is a cross- and parallel-bedded volcaniclastic greywacke derived largely from erosion of the underlying Umba Volcanic Formation. It has yielded detrital zircons with 207Pb/206Pb dates as young as 2055.5±2.3Ma, which is a maximum age for deposition and is inferred to date part of the underlying Umba volcanics. In Pechenga, the Kolosjoki Sedimentary Formation was intersected by a drill hole obtained by the ICDP (International Continental Scientific Drilling Program)-supported FAR-DEEP (Fennoscandian Arctic Russia-Drilling Early Earth Project) drilling programme. Zircons from a mafic fine tuff in this drill core have yielded a 207Pb/206Pb age of 2056.6±0.8Ma. This age is interpreted as an eruption age contemporaneous with sedimentation. The new age determinations overlap each other within uncertainty, and is within error of previously published detrital zircon ages of 2058±2Ma from the Kolosjoki Sedimentary Formation and 2049±28Ma from the Kuetsj{arvi Volcanic Formation. Combined, these indicate that the Lomagundi-Jatuli excursion terminated across Fennoscandia by 2056.6±0.8Ma and may correlate with similar termination ages in Fennoscandia and the Transvaal, South Africa. © 2012.
cited By 40
Keywords: carbon isotope; carbonate rock; deposition; geochronology; greenstone belt; Proterozoic; radionuclide; sedimentation; uranium-lead dating; zircon; Fennoscandia; Finland; Kola Peninsula; Murmansk [Russian Federation]; Norway; Russian Federation; South Africa; Transvaal

Atmospheric simulations of southern South America's climate since the Last Glacial maximum - Pollock, Edward W.; Bush, Andrew B.G. (Quaternary Science Reviews, 2013)

Destructive and non-destructive density determination: Method comparison and evaluation from the Laguna Potrok Aike sedimentary record - Fortin, David; Gebhardt, Andrea Catalina; Hahn, Annette; Kliem, Pierre; Lis'e-Pronovost, Agathe; Roychowdhury, Rajarshi; Labrie, Jacques; St-Onge, Guillaume (Quaternary Science Reviews, 2013)
Density measurements play a central role in the characterization of sediment profiles. When working with long records (>100m), such as those routinely obtained within the frame of the International Continental Scientific Drilling Program, several methods can be used, all of them varying in resolution, time-cost efficiency and source of errors within the measurements. This paper compares two relatively new non-destructive densitometric methods, CT-Scanning and the coherent/incoherent ratio from an Itrax XRF core Scanner, to data acquired from a Multi-sensor core logger Gamma Ray Attenuation Porosity Evaluator (MSCL Grape) and discrete measurements of dry bulk density, wet bulk density and water content. Quality assessment of density measurements is performed at low and high resolution along the Laguna Potrok Aike (LPA) composite sequence. Giving its resolution (0.4mm in our study), its high signal to noise ratio, we conclude that CT-Scan provides a precise, fast and cost-efficient way to determine density variation of long sedimentary record. Although more noisy that the CT-Scan measurements, coherent/incoherent ratio from the XRF core scanner also provides a high-resolution, reliable continuous measure of density variability of the sediment profile. The MSCL Grape density measurements provide actual density data and have the significant advantage to be completely non-destructive since the acquisition is performed on full cores prior to opening. However, the quality MSCL Grape density measurements can potentially be reduced by the presence of voids within the sediment core tubes and the dry and bulk density measurements suffers from sampling challenges and are time-consuming. © 2012 Elsevier Ltd.
Keywords: Argentina; Laguna Potrok Aike; Santa Cruz [Argentina]; Vitaceae; Density measurement (specific gravity); Fruits; Gamma rays; Scanning; Sedimentology; Sediments; Bulk density measurement; Continental scientific drillings; CT-scan; Density variabilities; High signal-to-noise ratio; ICDP-project PASADO; Sediment densities; XRF; bulk density; cost-benefit analysis; measurement method; resolution; sampling; sediment core; signal-to-noise ratio; X-ray fluorescence; Computerized tomography

Impact-generated hydrothermal systems on Earth and Mars - Osinski, G.R.; Tornabene, L.L.; Banerjee, N.R.; Cockell, C.S.; Flemming, R.; Izawa, M.R.M.; McCutcheon, J.; Parnell, J.; Preston, L.J.; Pickersgill, A.E.; Pontefract, A.; Sapers, H.M.; et al. (Icarus, 2013)
It has long been suggested that hydrothermal systems might have provided habitats for the origin and evolution of early life on Earth, and possibly other planets such as Mars. In this contribution we show that most impact events that result in the formation of complex impact craters (i.e., >2-4 and >5-10. km diameter on Earth and Mars, respectively) are potentially capable of generating a hydrothermal system. Consideration of the impact cratering record on Earth suggests that the presence of an impact crater lake is critical for determining the longevity and size of the hydrothermal system. We show that there are six main locations within and around impact craters on Earth where impact-generated hydrothermal deposits can form: (1) crater-fill impact melt rocks and melt-bearing breccias; (2) interior of central uplifts; (3) outer margin of central uplifts; (4) impact ejecta deposits; (5) crater rim region; and (6) post-impact crater lake sediments. We suggest that these six locations are applicable to Mars as well. Evidence for impact-generated hydrothermal alteration ranges from discrete vugs and veins to pervasive alteration depending on the setting and nature of the system. A variety of hydrothermal minerals have been documented in terrestrial impact structures and these can be grouped into three broad categories: (1) hydrothermally-altered target-rock assemblages; (2) primary hydrothermal minerals precipitated from solutions; and (3) secondary assemblages formed by the alteration of primary hydrothermal minerals. Target lithology and the origin of the hydrothermal fluids strongly influences the hydrothermal mineral assemblages formed in these post-impact hydrothermal systems. There is a growing body of evidence for impact-generated hydrothermal activity on Mars; although further detailed studies using high-resolution imagery and multispectral information are required. Such studies have only been done in detail for a handful of martian craters. The best example so far is from Toro Crater (Marzo, G.A., Davila, A.F., Tornabene, L.L., Dohm, J.M., Fairèn, A.G., Gross, C., Kneissl, T., Bishop, J.L., Roush, T.L., Mckay, C.P. [2010]. Icarus 208, 667-683). We also present new evidence for impact-generated hydrothermal deposits within an unnamed ∼32-km diameter crater ∼350. km away from Toro and within the larger Holden Crater. Synthesizing observations of impact craters on Earth and Mars, we suggest that if there was life on Mars early in its history, then hydrothermal deposits associated with impact craters may provide the best, and most numerous, opportunities for finding preserved evidence for life on Mars. Moreover, hydrothermally altered and precipitated rocks can provide nutrients and habitats for life long after hydrothermal activity has ceased. © 2012 Elsevier Inc.
cited By 178

Granitic basement below Deccan Traps Unearthed by drilling in the Koyna seismic zone, Western India - Roy, Sukanta; Rao, N. P.; Akkiraju, Vyasulu V.; Goswami, Deepjyoti; Sen, Mrinal; Bansal, B. K.; Nayak, Shailesh (Journal of the Geological Society of India, 2013)

High-latitude environmental change during MIS 9 and 11: biogeochemical evidence from Lake El'gygytgyn, Far East Russia - D'Anjou, R. M.; Wei, J. H.; Castaneda, I. S.; Brigham-Grette, J.; Petsch, S. T.; Finkelstein, D. B. (Climate of the Past, 2013)
Marine isotope stages (MIS) 11 has been proposed as an analog for the present interglacial; however, terrestrial records of this time period are rare. Sediments from Lake El'gygytgyn (67 300 N, 172 50 E) in Far East Russia contain a 3.56 Ma record of climate variability from the Arctic. Here, we present the first terrestrial Arctic reconstruction of environmental and climatic changes from MIS 8 through 12 (289 to 464 ka) using organic geochemical proxies. Terrestrial vegetation changes, as revealed by plant leaf wax (n-alkane) indices and concentrations of arborinol (a biomarker for trees), show increased tree cover around the lake during interglacial periods, with higher concentrations observed during MIS 11 as compared to MIS 9. A similar pattern is also observed in records of aquatic productivity revealed by molecular indicators from dinoflagellates (dinosterol), eustigmatophyte algae (long-chain (C28-C32) 1, 15 n-alkyl diols) in addition to short-chain n-alkanes, where aquatic productivity is highest during MIS 11. Changes recorded in these molecular proxies show a similar structure to relative temperature variability as recorded by the MBT/CBT (Methylation of Branched Tetraether/Cyclization of Branched Tetraether) paleothermometer, based on branched glycerol dialkyl glycerol tetraethers (GDGTs). Additionally, relative MBT/CBT temperature changes generally track pollen and diatom 18O temperature estimates, compiled by other studies, which suggest glacial-interglacial temperature changes of 9 to 12 C. These records of environmental and climatic change indicate Arctic sensitivity to external forcings such as orbital variability and atmospheric greenhouse gas concentrations. Overall, this study indicates that organic geochemical analyses of the Lake El'gygytgyn sediment archive can provide critical insight into the response of lake ecosystems and their sensitivity in high latitude regions. © Author(s) 2013.
cited By 20
Keywords: alga; biogeochemical cycle; biomarker; climate change; environmental change; greenhouse gas; interglacial; lacustrine deposit; latitude; marine isotope stage; temperature effect; vegetation; Arctic; Chukchi; Elgygytgyn Lake; Far East; Russian Federation

High-resolution fault image from accurate locations and focal mechanisms of the 2008 swarm earthquakes in West Bohemia, Czech Republic - Vavryčuk, V'aclav; Bouchaala, Fateh; Fischer, Tom'aš (Tectonophysics, 2013)
We have analyzed 463 micro-earthquakes in the magnitude range from 0.5 to 3.8 that occurred during the 2008 earthquake swarm in West Bohemia, Czech Republic, in order to screen the detailed structure of the focal zone situated at depths between 7 and 11. km. The double-difference location method was applied to records of 22 local seismic stations with an epicentral distance of less than 25. km in order to retrieve highly accurate locations of hypocenters with an accuracy of less than 20. m. The hypocenters are well-clustered and distinctly map the system of activated faults. The fault system has a complex geometry being composed of several fault segments with different orientations. Some of the segments intersect each other. The orientations of the segments coincide well with the focal mechanisms. We have introduced and evaluated the so-called fault instability of the individual fault segments. The fault instability ranges from 0 (most stable faults) to 1 (most unstable faults) and measures the susceptibility of the fault to be activated under specified stress. In the West Bohemia focal zone, two fault segments are optimally oriented with respect to the tectonic stress being characterized by an instability value higher than 0.9. Tractions on these fault segments are concentrated in the Mohr's diagram in the area of validity of the Mohr-Coulomb failure criterion and the associated micro-earthquakes are mainly shear. The other fault segments are slightly misoriented with instability values between 0.7 and 0.9, and the shear traction is significantly lower. These earthquakes are probably more tensile and activated most likely by the local redistribution of Coulomb stress during swarm activity. © 2013 Elsevier B.V.
Keywords: Bohemia; Czech Republic; Earthquakes; Stability; Earthquake location; Failure criteria; Fault friction; Focal mechanism; Tectonic stress; Coulomb criterion; earthquake event; earthquake hypocenter; earthquake magnitude; focal mechanism; image resolution; microearthquake; Faulting

High-resolution paleomagnetic secular variations and relative paleointensity since the Late Pleistocene in southern South America - Lis'e-Pronovost, Agathe; St-Onge, Guillaume; Gogorza, Claudia; Haberzettl, Torsten; Preda, Michel; Kliem, Pierre; Zolitschka, Bernd (Quaternary Science Reviews, 2013)
Paleomagnetic inclination, declination and relative paleointensity were reconstructed from the sediments of Laguna Potrok Aike in the framework of the International Continental scientific Drilling Program (ICDP) Potrok Aike maar lake Sediment Archive Drilling prOject (PASADO). Here we present the u-channel-based full vector paleomagnetic field reconstruction since 51.2ka cal BP. The relative paleointensity proxy (RPI) was built by normalising the natural remanent magnetisation with the anhysteretic remanent magnetisation using the average ratio at 4 demagnetisation steps part of the ChRM interval (NRM/ARM10-40mT). A grain size influence on the RPI was removed using a correction based on the linear relationship between the RPI and the median destructive field of the natural remanent magnetisation (MDFNRM). The new record is compared with other lacustrine and marine records and stacks from the mid- to high-latitudes of the Southern Hemisphere, revealing consistent millennial-scale variability, the identification of the Laschamp and possibly the Mono Lake geomagnetic excursions, and a direction swing possibly associated to the Hilina Pali excursion at 20ka cal BP. Nonetheless, a global-scale comparison with other high-resolution records located on the opposite side of the Earth and with various dipole field references hint at a different behaviour of the geomagnetic field around southern South America at 46ka cal BP. © 2012 Elsevier Ltd.
Keywords: Argentina; Laguna Potrok Aike; Santa Cruz [Argentina]; South America; Lakes; Magnetization; Sedimentology; ICDP-project PASADO; Laguna potrok aike; Paleomagnetism; Relative paleointensity; Secular variation; Southern Hemisphere; geomagnetism; grain size; lacustrine deposit; paleomagnetism; Pleistocene; proxy climate record; reconstruction; resolution; secular variation; Southern Hemisphere; Geomagnetism

High-temperature thermomagnetic properties of vivianite nodules, Lake El'gygytgyn, Northeast Russia - Minyuk, P. S.; Subbotnikova, T. V.; Brown, L. L.; Murdock, K. J. (Climate of the Past, 2013)

Identity and typification of Diploneis ostracodarum, Diploneis budayana and Diploneis praeclara (Bacillariophyta) - Jovanovska, Elena; Buczk'o, Krisztina; Ognjanova-Rumenova, Nadja G.; Nakov, Teofil; Levkov, Zlatko (Phytotaxa, 2013)
A lectotype and isolectotype for Navicula budayana Pantocsek = Diploneis budayana (Pantocsek) Hustedt, Navicula ostracodarum Pantocsek = Diploneis ostracodarum (Pantocsek) Jovanovska, Nakov & Levkov and Navicula praeclara Pantocsek = Diploneis praeclara (Pantocsek) Cleve-Euler from K{opecz, Neogene fossil deposits in Romania have been made. Typification for each species was based on Pantocsek's original images and material deposited at the Hungarian Natural History Museum (BP). Unfortunately, the type slides for Diploneis budayana, D. ostracodarum and D. praeclara were lost or destroyed during the course of World War II. Therefore, authentic material from the type locality K{opecz at BP was used to designate the lectotypes for these three species. Detailed LM and SEM observations have been assigned for each taxon, in order to ascertain the variation in valve morphology. Taxonomic descriptions and comments are made for each species. Typification of taxa described by Pantocsek would potentially affect further stratigraphic, comparative or molecular phylogenetic work not just for Tertiary floras but for Recent floras as well. In particular, studies concerning comparisons of these species between localities, such as Lake Ohrid, will greatly benefit from this work. The outcome of such studies will shed light on the evolutionary and biogeographic history of diatoms in the context of geologic events on the Balkan Peninsula. © 2013 Magnolia Press.

Ikaite precipitation in a lacustrine environment - implications for palaeoclimatic studies using carbonates from Laguna Potrok Aike (Patagonia, Argentina) - Oehlerich, Markus; Mayr, Christoph; Griesshaber, Erika; L{ucke, Andreas; Oeckler, Oliver M.; Ohlendorf, Christian; Schmahl, Wolfgang W.; Zolitschka, Bernd (Quaternary Science Reviews, 2013)
The monoclinic mineral ikaite (CaCO3 · 6H2O) and its pseudomorphs are potentially important archives for palaeoenvironmental reconstructions. Natural ikaite occurs in a small temperature range near freezing point and is reported mainly from marine and only rarely from continental aquatic environments. Ikaite transforms to more stable anhydrous forms of CaCO3 after an increase in temperature or when exposed to atmospheric conditions. The knowledge about conditions for natural ikaite formation, its stable isotope fractionation factors and isotopic changes during transformation to calcite is very restricted. Here, for the first time, primary precipitation of idiomorphic ikaite and its calcite pseudomorphs are reported from a subsaline lake, Laguna Potrok Aike, in southern Argentina. The calculated stable oxygen isotope fractionation factor between lake water and ikaite-derived calcite (αPAI=1.0324 at a temperature of 4.1°C) is close to but differs from that of primarily inorganically precipitated calcite. Pseudomorphs after ikaite rapidly disintegrate into calcite powder that is indistinguishable from μm-sized calcite crystals in the sediment record of Laguna Potrok Aike suggesting an ikaite origin of sedimentary calcites. Therefore, the Holocene carbonates of Laguna Potrok Aike have the potential to serve as a recorder of past hydrological variation. © 2012 Elsevier Ltd.
Keywords: Argentina; Laguna Potrok Aike; Santa Cruz [Argentina]; Calcium carbonate; Isotopes; Lakes; Lasers; Minerals; Oxygen; Sedimentary rocks; Aquatic environments; Atmospheric conditions; ICDP project PASADO; Oxygen isotope fractionations; Palaeoenvironmental reconstruction; Stable isotope fractionations; Stable isotopes; Stable oxygen isotopes; calcite; calcium carbonate; freezing; Holocene; ikaite; isotopic fractionation; lacustrine deposit; lacustrine environment; marine environment; oxygen isotope; paleoenvironment; precipitation (chemistry); reconstruction; sediment chemistry; stable isotope; temperature effect; Calcite

Impact of volcanism on the evolution of Lake Van I: Evolution of explosive volcanism of Nemrut Volcano (eastern Anatolia) during the past >400,000 years - Sumita, M.; Schmincke, H.-U. (Bulletin of Volcanology, 2013)
The historically active Nemrut Volcano (2,948 m asl) (Eastern Anatolia), rising close to the western shore of huge alkaline Lake Van, has been the source of intense Plinian eruptions for >530,000 years (drilled lake sediments). About 40 widespread, newly recognized trachytic and less common rhyolitic fallout tephras and ca. 12 interbedded ignimbrites, sourced in Nemrut Volcano, are documented in stratigraphic traverses throughout an area of >6,000 km2 mostly west of Lake Van. Phenocrysts in the moderately peralkaline trachytes and rarer large-volume comenditic rhyolites comprise anorthoclase, hedenbergite-augite, fayalite and, especially in trachytic units, augite, minor aenigmatite, apatite and quartz, and rare chevkinite and zircon. Dacitic to rhyolitic tephras from nearby calcalkalic S{uphan Volcano (4,058 m asl), locally interbedded with Nemrut tephras, are characterized by disequilibrium phenocryst assemblages (biotite, augitic clinopyroxene and hypersthene, minor olivine, common crystal clots and/or, in some deposits, amphibole). The magma volume (DRE) of the largest Nemrut tephra sheet (AP-1) described in detail may exceed 30 km3. Extreme facies and systematic compositional changes are documented in the ca. 30 ka Nemrut Formation (NF) deposits formed from one large and complex eruption (thick rhyolitic fallout overlain by ignimbrite, welded agglutinate, overbank surge deposits, and final more mafic fallout deposits). Common evidence of magma mixing in Nemrut ignimbrites reflects eruption from compositionally zoned magma reservoirs. Several young Çekmece Formation trachytes overlying ca. 30 ka old NF deposits and the late trachytes of the NF deposits show compositional affinities to tephra from S{uphan Volcano possibly due to temporary influx of S{uphan magmas into the Nemrut system following the evacuation of >10 km3 magma (DRE) during the caldera-forming NF eruption. Axes of large fallout fans are dominantly SW-NE but W-E in the younger sheets resembling the direction of the present dominant wind field. Growth of Nemrut volcanic edifice and its peripheral domes since before 0.5 Ma in the hinge area between the Van and Muş tectonic basins is likely to have been the major factor in isolating Lake Van basin thus initiating the origin and subsequent alkaline evolution of the lake. This alkalinity was later significantly controlled by climate forcing. Internal forcing mechanisms (volcanic and geodynamic) may also have contributed to major lake level changes in addition to climate forcing. © 2013 Springer-Verlag Berlin Heidelberg.
cited By 49
Keywords: basin evolution; ignimbrite; lithostratigraphy; peralkaline rock; phenocryst; plinian eruption; rhyolite; tephra; trachyte; volcanic eruption; volcanism; Bitlis; Lake Van; Nemrut; Turkey; Plinia; Trachytes

Impact of volcanism on the evolution of Lake Van II: Temporal evolution of explosive volcanism of Nemrut Volcano (eastern Anatolia) during the past ca. 0.4Ma - Sumita, M.; Schmincke, H.-U. (Journal of Volcanology and Geothermal Research, 2013)
Thirty-two new single crystal ages document 400. 000. years of widespread explosive volcanism of historically active Nemrut Volcano towering over huge alkaline Lake Van (Eastern Anatolia). The dated deposits were selected to monitor the volcanic and compositional evolution of Nemrut Volcano through time and thus to provide a rigorous temporal framework for the tephra record of the PaleoVan Drilling Project. Tephra samples were taken from large-volume deposits or those that occur in medial to distal localities, well-exposed stratigraphic sections or from the initial phase of an eruptive sequence. Mainly fallout deposits were chosen because most ignimbrites show more complex and corroded feldspar populations owing to compositional zoning and magma mixing. Moreover, fallout deposits held the promise to be more clearly identifiable with-and correlatable to->. 300 tephra layers in the PaleoVan drill cores, even though commonly in amounts marginal or insufficient in thickness to allow well-supported single crystal dating. The crystals dated are dominantly anorthoclase, the main phenocryst phase in the trachytic to rhyolitic, slightly to strongly peralkaline Nemrut magmas. Ages obtained so far range from ca. 400. ka to ca. 30. ka for Nemrut Volcano. The causes of significant changes in the frequency, volume and composition of tephra layers per unit time are discussed in terms of external (erosion, climate changes, geodynamic factors) and internal forcing (changes in magma supply and composition and incubation periods preceding large volume rhyolitic eruptions). For example, the low frequency of tephra layers deposited prior to ca. 200. ka may be due to low explosive activity, severe erosion between MIS 9 and MIS 11, or both. Nevertheless, the overall frequency of explosive eruptions appears to have increased during the past ca. 200. ka. We also recognize a slight peak in explosive eruptions during warm periods (e.g. MIS 5 and MIS 7) and speculate on lithospheric unloading triggering increased partial melting or magma reservoir unloading following massive glacier melting. The ages of 5 dated ignimbrites span ca. 250. 000. years suggesting that Nemrut Volcano went through a polycyclic evolution with multiple caldera collapses and major pyroclastic flow eruptions, the oldest dated so far as 265. ka. The widely held view of the impressive Nemrut Caldera now dated to have formed at ca. 30. ka, as the main paroxysmal event during the evolution of the volcano is no longer tenable. Distinct and coherent compositional characteristics, especially in trace element concentrations, characterize several groups of trachytic tephras. We speculate that the growth of Nemrut Volcano caused the isolation of the Lake Van basin. On account of their mineralogical (anorthoclase, hedenbergite, fayalite, aenigmatite) and alkalic chemical compositions and large volume, dated Nemrut fallout tephras are likely to represent excellent markers in lakes and other sites of paleoclimatological or archeological interest in neighboring countries to the northeast of Lake Van as far as the Caspian Sea in what may be called the East Anatolian Tephra Province. © 2012 Elsevier B.V.
cited By 51
Keywords: Alkalinity; Climate change; Deposits; Erosion; Explosives; Fallout; Feldspar; Feldspar deposits; Lakes; Melting; Reservoirs (water); Single crystals; Stratigraphy; Submarine geophysics; Trace elements; Unloading; Chemical compositions; Compositional characteristics; Compositional evolution; Compositional zoning; East Anatolian Tephra Province; Explosive volcanism; Lake vans; Trace element concentrations; Volcanoes; argon-argon dating; explosive volcanism; ignimbrite; marine isotope stage; pyroclastic flow; temporal evolution; tephra; volcanic eruption; Bitlis; Lake Van; Nemrut; Turkey

Insights into early Earth from Barberton komatiites: Evidence from lithophile isotope and trace element systematics - Puchtel, I.S.; Blichert-Toft, J.; Touboul, M.; Walker, R.J.; Byerly, G.R.; Nisbet, E.G.; Anhaeusser, C.R. (Geochimica et Cosmochimica Acta, 2013)

Geomicrobiological investigations in subsaline maar lake sediments over the last 1500 years - Vuillemin, Aurèle; Ariztegui, Daniel (Quaternary Science Reviews, 2013)
Living microorganisms inhabit every environment of the biosphere but only in the last decades their importance governing biochemical cycles in deep sediments has been widely recognized. Most investigations have been accomplished in the marine realm whereas there is a clear paucity of comparable studies in lacustrine sediments. One of the main challenges is to define geomicrobiological proxies that can be used to identify different microbial signals in the sediments. Laguna Potrok Aike, a maar lake located in Southeastern Patagonia, has an annually not stratifying cold water column with temperatures ranging between 4 and 10°C, and most probably an anoxic water/sediment interface. These unusual features make it a peculiar and interesting site for geomicrobiological studies. Living microbial activity within the sediments was inspected by the first time in a sedimentary core retrieved during an ICDP-sponsored drilling operation. The main goals to study this cold subsaline environment were to characterize the living microbial consortium; to detect early diagenetic signals triggered by active microbes; and to investigate plausible links between climate and microbial populations. Results from a meter long gravity core suggest that microbial activity in lacustrine sediments can be sustained deeper than previously thought due to their adaptation to both changing temperature and oxygen availability. A multi-proxy study of the same core allowed defining past water column conditions and further microbial reworking of the organic fraction within the sediments. Methane content shows a gradual increase with depth as a result of the fermentation of methylated substrates, first methanogenic pathway to take place in the shallow subsurface of freshwater and subsaline environments. Statistical analyses of DGGE microbial diversity profiles indicate four clusters for Bacteria reflecting layered communities linked to the oxidant type whereas three clusters characterize Archaea communities that can be linked to both denitrifiers and methanogens. Independent sedimentary and biological proxies suggest that organic matter production and/or preservation have been lower during the Medieval Climate Anomaly (MCA) coinciding with a low microbial colonization of the sediments. Conversely, a reversed trend with higher organic matter content and substantial microbial activity characterizes the sediments deposited during the Little Ice Age (LIA). Thus, the initial sediments deposited during distinctive time intervals under contrasting environmental conditions have to be taken into account to understand their impact on the development of microbial communities throughout the sediments and their further imprint on early diagenetic signals. © 2012 Elsevier Ltd.
Keywords: Argentina; Laguna Potrok Aike; Patagonia; Santa Cruz [Argentina]; Bacteria (microorganisms); Bacteria; Biogeochemistry; Biological materials; Deposits; Lakes; Methanation; Methane; Organic compounds; Sedimentology; DGGE; Early diagenesis; Laguna potrok aike; LIA; MCA; Methane production; Microbial activities; PASADO; Patagonia; Subsaline; bacterium; biosphere; colonization; community structure; environmental conditions; fermentation; lacustrine deposit; Little Ice Age; maar; methane; microorganism; organic matter; oxygen; population structure; salinity; sediment core; species diversity; temperature effect; water column; Sediments

Isotopic systematics of the early Mauna Kea shield phase and insight into the deep mantle beneath the Pacific Ocean - Nobre Silva, Inês G.; Weis, Dominique; Scoates, James S. (Geochemistry, Geophysics, Geosystems, 2013)
The 3500 m deep Hawai'i Scientific Drilling Project core provides a 680 kyr record of the magmatic history and source components of Mauna Kea volcano. We report high-precision Pb-Sr-Nd isotopic compositions of 40 basalts from the last 408 m of the final drilling phase (HSDP2-B and HSDP2-C) and show that these lowermost basalts represent the early shield stage of Mauna Kea's growth history. Two sample groups are distinguished based on their isotopic variability compared to the rest of the core. Over a depth interval of 210 m (3098.2-3308.2 mbsl), the basalts show very restricted isotopic variation and represent sampling of a relatively homogeneous source. Samples from the bottom 192 m record the largest range of 206Pb/204Pb and 208Pb/204Pb in the core, reflecting the greater isotopic variability of the earlier stages of volcanism compared to subsequent stages. The heterogeneity of Mauna Kea lavas is explained by mixing variable proportions of four distinct components intrinsic to the Hawaiian mantle plume. One of these components, Kea, is a prevalent and long-lived composition within the Hawaiian plume, whereas the other three components are involved at different stages of the volcano's history and contribute to the short-term isotopic variability of Mauna Kea. The compositional similarity of the Kea component to C and to the super-chondritic bulk-silicate Earth suggests that Kea may be part of the primitive mantle of a non-chondritic Earth. Other Pacific oceanic island basalts share Kea-like compositions, indicating that the Kea component is a common, widespread composition within the Pacific deep mantle. ©2013. American Geophysical Union. All Rights Reserved.
Keywords: Hawaii [(ISL) Hawaiian Islands]; Hawaii [United States]; Hawaiian Islands; Mauna Kea; Pacific Ocean; United States; Basalt; Core samples; Lead; Silicates; Strontium; Thermal plumes; Volcanoes; HSDP2; Mantle heterogeneity; Mantle plume; Mauna keas; Ocean island basalts; Pb-Sr-Nd isotope systematics; isotopic composition; mantle chemistry; mantle plume; mantle source; Ocean Drilling Program; ocean island basalt; volcanism; Isotopes

Kolosjoki Sedimentary Formation: A record in the aftermath of the Paleoproterozoic global positive δ13C excursion in sedimentary carbonates - Salminen, Paula E; Karhu, Juha A; Melezhik, Victor A (Chemical Geology, 2013)

Kolosjoki Sedimentary Formation: A record in the aftermath of the Paleoproterozoic global positive δ13C excursion in sedimentary carbonates - Salminen, Paula E.; Karhu, Juha A.; Melezhik, Victor A. (Chemical Geology, 2013)

Late Cretaceous climate changes recorded in Eastern Asian lacustrine deposits and North American Epieric sea strata - Wang, C.; Scott, R.W.; Wan, X.; Graham, S.A.; Huang, Y.; Wang, P.; Wu, H.; Dean, W.E.; Zhang, L. (Earth-Science Reviews, 2013)
Cretaceous climate data of the long-lived Cretaceous Songliao Basin (SB) in eastern Asia is correlated and compared with the Western Interior Seaway (WIS) on the northern American plate, in order to understand better the dynamics of the Earth's past 'greenhouse' climates. Nearly continuous Late Cretaceous terrestrial deposition in the Songliao Basin is represented by two cores totaling 2431m in length. The Turonian-Maastrichtian age of the section is based on integrated stratigraphy, and is comparable in age with Upper Cretaceous strata in the WIS. Being consistent with global trends, the dynamic Late Cretaceous climates of both the SB and WIS gradually cooled from the warmest Albian-Cenomanian time to the end of the Maastrichtian with several intervening warm periods as did the global climate. However regional differences existed, the Songliao Basin climate was humid to semi-humid, warm temperate-subtropical and the Western Interior Seaway was in the humid, warm temperate zone and experienced only moderate climatic changes. The shifts of oxygen isotope data in the Songliao Basin were frequent and abrupt, whereas WIS records more gradual change affected mainly by fresh-water runoff mixing with southern Tethyan and northern Arctic waters. Sedimentary cycles of eccentricity, obliquity and precession bands are recorded in both the SB and WIS basins. The sedimentary cycles in the WIS and SB are interpreted to be related to variations of the wet/dry runoff cycles, which indicate that orbital forcing played an important role in global climate change in Late Cretaceous. The most favorable condition for organic carbon burial in both the SB and WIS basin was bottom water anoxia regardless of the cause of the anoxia. But the organic carbon burial rate was usually much higher in the Songliao Lake than in the WI epeiric sea suggesting that giant lakes may serve as important sinks of atmospheric CO2. In both basins organic-rich deposits formed during a rise in water level and incursion of saline waters. The integration of paleoclimate data from Cretaceous marine deposits and terrestrial sedimentary record will promote our understanding of the Cretaceous 'greenhouse' climate change and may provide insights for a future greenhouse world. © 2013 Elsevier B.V.
cited By 100
Keywords: Albian; carbon sink; Cenomanian; climate variation; Cretaceous; deposition; eccentricity; global climate; greenhouse effect; lacustrine deposit; Maastrichtian; organic carbon; oxygen isotope; paleoclimate; runoff; sediment core; stratabound deposit; stratigraphy; Turonian; water level; China; Songliao Basin

Late Cretaceous stratigraphy, Songliao Basin, NE China: SK1 cores - Wan, X.; Zhao, J.; Scott, R.W.; Wang, P.; Feng, Z.; Huang, Q.; Xi, D. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2013)
The Songliao Basin is the largest Cretaceous oil and gas-producing lacustrine basin in China, with its greatest aerial extent in the middle Cretaceous. A coring program (SK1) has to date yielded 2485.89m of continuous core (96.46% recovery) and provides significant material for Cretaceous research. The sequence of the core consists mainly of lacustrine sandstone, dark grey mudstone, shale and oil-shale. The Upper Cretaceous stratigraphic section has been subdivided into the Quantou, Qingshankou, Yaojia, Nenjiang, Sifangtai and Mingshui formations in ascending order. Late Cretaceous microfossils are diverse and abundant. A detailed biostratigraphic study has subdivided the sequence into high precision biozones: 21 ostracode assemblages, 10 phytoplankton assemblages, 7 palynological zones and 4 charophyta assemblages, respectively. In addition, marine foraminifera were first discovered from the basin. Three 206Pb/238U ages and one 40Ar/39Ar age were analysed. Ten local magnetozones have been recognised in the SK1 (North), and two magnetozones have been indicated in the SK1 (South). Based on biostratigraphy, high-resolution magnetostratigraphy and SIMS U-Pb zircon analyses, the SK1 stratigraphy is correlated with Upper Cretaceous stages in the International Geologic Time Scale. The upper part of the Quantou Formation is the lower Turonian; the Qingshankou Formation is the upper Turonian-lower Coniacian; the Yaojia Formation is from the upper Coniacian to middle Santonian; the Nenjiang Formation is the upper Santonian to middle Campanian; the Sifangtai Formation is limited to the upper Campanian; and the Mingshui Formation is the uppermost Campanian to Maastrichtian. It is likely that the upper part of the Mingshui Formation belongs to the Paleocene, and the K/Pg boundary is within the Member 2 of the Mingshui Formation around the depth of 328m by new micropalaeontologic and magnetostratigraphic data. © 2012 Elsevier B.V.
cited By 143
Keywords: biostratigraphy; biozonation; Campanian; charophyte; chronostratigraphy; Coniacian; core analysis; Cretaceous-Tertiary boundary; foraminifera; gas production; hydrocarbon reserve; hydrocarbon reservoir; lacustrine deposit; Maastrichtian; magnetostratigraphy; marine environment; microfossil; micropaleontology; mudstone; oil production; oil shale; ostracod; palynology; phytoplankton; sandstone; Santonian; stratigraphic correlation; timescale; Turonian; uranium-lead dating; China; Songliao Basin; Charales; Coniacian; Foraminifera; Ostracoda

Late Cretaceous–early Paleogene charophytes from Songliao Basin, North China: SK1 (N) Core - Li, Sha; Zhang, YY; Qu, HY; Wang, MY; Wan, XQ; Sinica, Acta Micropalaeontologica; et al. (Acta Micropalaeontologica Sinica, 2013)

Late-interseismic state of a continental plate-bounding fault: Petrophysical results from DFDP-1 wireline logging and core analysis, Alpine Fault, New Zealand - Townend, J.; Sutherland, R.; Toy, V.G.; Eccles, J.D.; Boulton, C.; Cox, S.C.; McNamara, D. (Geochemistry, Geophysics, Geosystems, 2013)
We present a geophysical characterization at 0.1-100 m scales of a major plate-bounding continental fault in a late-interseismic state. The Alpine Fault produces MW∼8 earthquakes every 200-400 years and last ruptured in 1717 AD. Wireline geophysical logs and rock cores extending from one side of the Alpine Fault to the other were acquired in two boreholes drilled in 2011 at Gaunt Creek during the first phase of the Deep Fault Drilling Project (DFDP-1). These data document ambient conditions under which the next Alpine Fault earthquake will occur. Principal component analysis of the wireline logging data reveals that >80% of the variance is accounted for by electrical, acoustic, and natural gamma properties, and preliminary multivariate classification enables the lithologies of sections of missing core to be reconstructed from geophysical measurements. The fault zone exhibits systematic variations in properties consistent with common processes of progressive alteration and comminution near the principal slip zone, superimposed on different protolith compositions. Our observations imply that the fault zone has the opposite sense of elastic asymmetry at 0.1-100 m scales to that of the crustal-scale orogen imaged by remote geophysical methods. On the basis of the fault-zone scale asymmetry, the bimaterial interface model of preferred earthquake rupture directions implies a northeastward direction of preferred Alpine Fault rupture. On-going characterization of the structural and hydraulic architecture of the Alpine Fault will improve our understanding of the relationship between in situ conditions, earthquake rupture processes, and the hazards posed by future earthquakes. © 2013. American Geophysical Union. All Rights Reserved.
cited By 47
Keywords: Earthquakes; Electric properties; Geophysics; Grinding (comminution); Plates (structural components); Principal component analysis; Rock drilling; Structural geology; Well logging; Alpine Faults; DFDP-1; Earthquake cycles; Fault zone structures; Wireline logging; Faulting; core analysis; deep drilling; earthquake rupture; fault zone; principal component analysis; seismicity; well logging; Alpine Fault Zone; New Zealand; South Island

Lithology, radiocarbon chronology and sedimentological interpretation of the lacustrine record from Laguna Potrok Aike, southern Patagonia - Kliem, Pierre; Enters, Dirk; Hahn, Annette; Ohlendorf, Christian; Lis'e-Pronovost, Agathe; St-Onge, Guillaume; Wastegård, Stefan; Zolitschka, Bernd (Quaternary Science Reviews, 2013)
The 106m long composite profile from site 2 of ICDP expedition 5022 (PASADO) at Laguna Potrok Aike documents a distinct change in sedimentation patterns from pelagic sediments at the top to dominating mass movement deposits at its base. The main lithological units correspond to the Holocene, to the Lateglacial and to the last glacial period and can be interpreted as the result of distinct environmental variations. Overflow conditions might have been achieved during the last glacial period, while signs of desiccation are absent in the studied sediment record. Altogether, 58 radiocarbon dates were used to establish a consistent age-depth model by applying the mixed-effect regression procedure which results in a basal age of 51.2cal.kaBP. Radiocarbon dates show a considerable increase in scatter with depth which is related to the high amount of reworking. Validation of the obtained chronology was achieved with geomagnetic relative paleointensity data and tephra correlation. © 2012 Elsevier Ltd.
Keywords: Argentina; Laguna Potrok Aike; Patagonia; Santa Cruz [Argentina]; Deposits; Geomagnetism; Salinity measurement; Sedimentology; Sediments; Argentina; Holocenes; ICDP-project PASADO; Lake level fluctuations; Late Pleistocene; Mass movement; Mixed-effect regression; Patagonia; climate variation; data set; geochronology; glacial environment; Holocene; lacustrine deposit; Last Glacial; lithology; mass movement; numerical model; radiocarbon dating; sedimentation; tephrochronology; Lithology

Detailed insight into Arctic climatic variability during MIS 11c at Lake El'gygytgyn, NE Russia - Vogel, H.; Meyer-Jacob, C.; Melles, M.; Brigham-Grette, J.; Andreev, A. A.; Wennrich, V.; Tarasov, P. E.; Rosen, P. (Climate of the Past, 2013)
Here we present a detailed multi-proxy record of the climate and environmental evolution at Lake El'gygytgyn, Far East Russian Arctic during the period 430-395 ka covering the marine isotope stage (MIS) 12/11 transition and the thermal maximum of super interglacial MIS 11c. The MIS 12/11 transition at Lake El'gygytgyn is characterized by initial warming followed by a cold reversal implying similarities to the last deglaciation. The thermal maximum of MIS 11c is characterized by full and remarkably stable interglacial conditions with mean temperatures of the warmest month (MTWM) ranging between ca. 10-15 C; annual precipitation (PANN) ranging between ca. 300-600 mm; strong in-lake productivity coinciding with dark coniferous forests in the catchment; annual disintegration of the lake ice cover; and full mixis of the water column. Such conditions persisted, according to our age model, for ca. 27 ± 8 kyr between ca. 425-398 ka. The Lake El'gygytgyn record closely resembles the climate pattern recorded in Lake Baikal (SE Siberia) sediments and Antarctic ice cores, implying interhemispheric climate connectivity during MIS 11c. © 2013. CC Attribution 3.0 License.
cited By 27
Keywords: climate modeling; climate variation; ice core; ice cover; interglacial; isotopic analysis; lake evolution; Chukchi; Elgygytgyn Lake; Russian Federation

Geophysical characterization of the Chicxulub impact crater - Gulick, S.P.S.; Christeson, G.L.; Barton, P.J.; Grieve, R.A.F.; Morgan, J.V.; Urrutia-Fucugauchi, J. (Reviews of Geophysics, 2013)
Geophysical data indicate that the 65.5 million years ago Chicxulub impact structure is a multi-ring basin, with three sets of semicontinuous, arcuate ring faults and a topographic peak ring (PR). Slump blocks define a terrace zone, which steps down from the inner rim into the annular trough. Fault blocks underlie the PR, which exhibits variable relief, due to target asymmetries. The central structural uplift is >10 km, and the Moho is displaced by 1-2 km. The working hypothesis for the formation of Chicxulub is: a 50 km radius transient cavity, lined with melt and impact breccia, formed within 10 s of the impact, and within minutes, weakened rebounding crust rose kilometers above the surface, the transient crater rim underwent localized deformation and collapsed into large slump blocks, resulting in a inner rim at 70-85 km radius, and outer ring faults at 70-130 km radius. The overheightened structural uplift collapsed outward, buried the inner slump blocks, and formed the PR. Most of the impact melt was ultimately emplaced as a coherent <3 km thick melt sheet within the central basin that shallows within the inner regions of the PR. Smaller pockets of melt flowed into the annular trough. Subsequently, slope collapse, ejecta, ground surge, and tsunami waves infilled the annular trough and annular basin with sediments up to 3 km and 900 m thick, respectively. Testing this working hypothesis requires direct observation of the impactites, within and adjacent to the PR and central basin. Key PointsA review of all geophysical data imaging ChicxulubSummary of the key features of the impact structureAn assessment of the relative timing of impact processes © 2013. American Geophysical Union. All Rights Reserved.
cited By 62

Interactions between rhyolitic and basaltic melts unraveled by chaotic mixing experiments - Morgavi, D.; Perugini, D.; De Campos, C.P.; Ertl-Ingrisch, W.; Lavall'ee, Y.; Morgan, L.; Dingwell, D.B. (Chemical Geology, 2013)
Magma mixing may operate at any stage in the evolution of a magmatic system. The development of mixing is strongly controlled by fluid dynamics and its understanding requires a comprehensive physico-chemical approach in order to identify and interpret its occurrence in nature. Here, we experimentally study the physical and chemical interplays during the mixing of basaltic and rhyolitic natural melts from the Snake River Plains, USA. In particular, we present the results of the first high-temperature mixing experiments performed under controlled chaotic dynamic conditions, providing a new methodological approach to constrain the complexities of the mixing process between natural silicate melts.The mixing process is initially governed by the dynamics of stretching and folding of the melts, producing alternating flow bands. These bands increase the contact area between the end-members, which subsequently enhance chemical exchanges and thus contribute to the generation of regions with variable degrees of hybridization. We quantified the mobility of major and trace elements across contact areas, and analyzed the concentration variance decay induced by chemical diffusion. The analysis shows that elements diffuse with different efficiencies as the chemical gradient evolves and therefore, the achievement of hybrid compositions contrasts between elements. The approach introduced in this study can, in principle, be applied to mixing trends observed in nature in order to estimate the time-scales and degree of magma mixing evidenced across volcanic rocks/deposits. © 2012 Elsevier B.V.
cited By 38
Keywords: Chemical diffusion; Chemical gradients; Element mobility; Hybrid melts; Major and trace elements; Methodological approach; Mixing experiments; Snake river plains; Chemical analysis; Diffusion in solids; Experiments; Silicates; Mixing; basalt; concentration (composition); diffusion; experimental study; fluid dynamics; mixing; mobility; physicochemical property; rhyolite; silicate melt; Idaho; Snake River Plain; United States

Geomaterials Under Extreme Loading: The Natural Case - Lambert, P.; Trumel, H. (Materials under Extreme Loadings: Application to Penetration and Impact, 2013)
cited By 0

Environmental/climate change in the Cretaceous greenhouse world: Records from Terrestrial scientific drilling of Songliao Basin and adjacent areas of China - Wang, C. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2013)
cited By 29

Geochemistry and geochronology of the jim sage volcanic suite, southern idaho: Implications for snake river plain magmatism and its role in the history of basin and range extension - Konstantinou, A.; Valley, J.; Strickland, A.; Miller, E.L.; Fisher, C.; Vervoort, J.; Wooden, J. (Geosphere, 2013)
The Jim Sage volcanic suite (JSVS) exposed in the Jim Sage and Cotterel Mountains of southern Idaho (USA) consists of two volcanic members composed of 240 km3 of Miocene rhyolite lavas separated by an interval of lacustrine sediments. It is capped by rheomorphic ignimbrite and as much as 100 m of basaltic lava fl ows probably derived from the central Snake River Plain (SRP) province to the north. The occurrence of volcanic vents in the JSVS links the lava fl ows to their local eruptive centers, while the adjacent Albion-Raft River-Grouse Creek metamorphic core complex exposes 3000 km2 of once deep-seated rocks that offer constraints on the composition of the potential crustal sources of these rhyolites. U-Pb zircon ages from the rhyolite lavas of the JSVS range from 9.5 to 8.2 Ma. The Miocene basalt of the Cotterel Mountains has an 87Sr/86Sri composition of 0.7066-0.7075 and εNd(i) = -3.7, and the rhyolite lavas of the JSVS have 87Sr/86Sri = 0.7114-0.7135 and εNd(i) values that range from -6.7 to -7.1. Zircon from the rhyolites of the JSVS range in δ18Ozr (Vienna standard mean ocean water, VSMOW) from -0.5‰ to 5.7‰ and have εHf(i) values ranging from -0.8 to -6.8. Based on geochronology, whole-rock major elements, trace elements, isotopes (Sr and Nd), and in situ zircon O and Hf isotopic compositions, we infer that the JSVS is genetically related to the central SRP province. The eruption of the low-δ18O rhyolites of the JSVS, outside of the main topographic extent of the SRP province (without the large calderas inferred for the SRP rhyolites) implies that there might be an alternative mechanism for the formation of the low-δ18O signature other than the proposed assimilation of hydrothermally altered caldera blocks. One suggestion is that the north to south propagation of SRP-type low-δ18O rhyolitic melt along the Albion fault led to off-axis magmatism. Another possibility is that there was prior and widespread (across a region wider than the SRP) hydrothermal alteration of the crust related to its earlier magmatic and faulting history. The eruption of SRP-type lavas in the hanging wall of an evolving metamorphic core complex helps us outline the role of the SRP magmatic province in the extensional evolution of the northeastern Basin and Range. The lavas of the JSVS imply the addition of basalt, related to the SRP hotspot, to the crust beneath the Raft River Basin that provided a heat source for crustal melting and weakening of the deep crust; this led to a vertical component of crustal fl ow and doming during extension, after the eruption of the 9.5-8.2 Ma JSVS rhyolites. This younger than 8.2 Ma component of vertical motion during faulting of the Miocene stratifi ed sequence of the Raft River Basin and the rotation of the Albion fault to shallower angles collectively resulted in the subhorizontal detachment structure imaged seismically beneath the Raft River Basin. © 2013 Geological Society of America.
cited By 15
Keywords: Hydrothermal alterations; Isotopic composition; Lacustrine sediments; Metamorphic core complex; Off-axis magmatism; Snake river plains; Standard mean ocean waters; Vertical component; Basalt; Faulting; Geochronology; Hafnium; Isotopes; Lead; Neodymium; Rivers; Strontium; Volcanoes; Watersheds; Zircon; Granite; basalt; basin evolution; caldera; detachment fault; faulting; geochronology; hafnium; hydrothermal alteration; igneous geochemistry; ignimbrite; isotopic composition; lacustrine deposit; lava flow; magmatism; Miocene; oxygen isotope; range expansion; rhyolite; uranium-lead dating; volcanic eruption; zircon; Idaho; Raft River; Snake River Plain; United States; Tetraonidae

Diversity and distribution of taxa in the genus Eunotia Ehrenberg (Bacillariophyta) in Macedonia - Pavlov, Aleksandar; Levkov, Zlatko (Phytotaxa, 2013)
Within the past few decades Eunotia (Bacillariophyceae) has been confirmed as one of the most species rich diatom genera. The remarkable diversity of this genus has been well documented for the tropical region of South America, and its wide distribution comprehensively demonstrated for North America and Canada, Europe, East and Southeast Asia, as well as the Subantarctic region. Till present day only twenty eight taxa of Eunotia have been reported for Macedonia, mainly from the various aquatic habitats of different mountains. The main focus of the present study is the diversity, taxonomy and general distribution of taxa belonging to Eunotia in Macedonian mountain regions. The area investigated covers most of the mountains in the western, south-western, southern, central and eastern part. In total 53 taxa have been observed, among which six are described as new species (Eunotia atomus, E. fabaeformis, E. mariovensis, E. pseudominor, E. scardica and E. stojanovskii). The morphological features, as observed by light microscopy (LM), are comprehensively described for each taxon. The ultrastructure of the valve, as observed by scanning electron microscopy (SEM), is additionally described for most of the taxa. The general distributional pattern, locality, altitude and substrate preference, for every taxon is also included. The distinctive characters between similar taxa are discussed and taxonomical notes are as well provided. © 2013 Magnolia Press.

Dynamic diatom response to changing climate 0-1.2Ma at Lake El'gygytgyn, Far East Russian Arctic - Snyder, J.A.; Cherepanova, M.V.; Bryan, A. (Climate of the Past, 2013)
The Lake El'gygytgyn sediment record contains an abundant diatom flora through most intervals of the lake's history, providing a means to create and test hypotheses concerning the lake's response to changing climates. The 0-1.2 Ma core interval is characterized by shifts in the dominant planktonic genera and events of exceptional concentration and diversity. Warm interglacial intervals have enhanced concentration and diversity of the plankton. This response is most extreme during exceptional events corresponding to marine isotope stages (MIS) 11 and 31. Diatom concentration and diversity also increase during some cold intervals (e.g., MIS 2), suggesting conditions of lake circulation and nutrient cycling promoting diatom production during these events. Short intervals of low plankton concentration accompanied by shifts in the dominant genus of the lake suggest conditions during certain cold events generate a severe impact on plankton production. The absence of these events during extended intervals of low summer insolation variability suggests a muted cold-event response of the lake system linked to regional climate. © Author(s) 2013.
cited By 15
Keywords: climate variation; diatom; dominance; interglacial; nutrient cycling; paleoclimate; paleoenvironment; physiological response; primary production; regional climate; species diversity; Chukchi; Elgygytgyn Lake; Russian Federation

Dynamic diatom response to changing climate 0 –1.2 Ma at Lake El'gygytgyn, Far East Russian Arctic - Snyder, J. A.; Cherepanova, M. V.; Bryan, A. (Climate of the Past, 2013)

Earth's earliest global glaciation? Carbonate geochemistry and geochronology of the Polisarka Sedimentary Formation, Kola Peninsula, Russia - Brasier, AT; Martin, AP; Melezhik, VA; Prave, AR; Condon, DJ; Fallick, AE (Precambrian Research, 2013)
As part of the International Continental Scientific Drilling Program's Fennoscandian Arctic Russia-Drilling Early Earth Project (ICDP FAR-DEEP), Palaeoproterozoic diamictic and associated rocks were targeted and recovered in Hole 3A on the Kola Peninsula of NW Russia. In addition to the diamictites, carbonate sedimentary rocks and volcanic ash layers (all metamorphosed to greenschist grade) were encountered. Sedimentology and geochemistry suggest deposition of the diamictites in an open-marine aragonite-precipitating environment. Sampling of the core and of outcrops from the same geographical area yielded a number of zircons for analyses, the majority of which were inherited. However a tuff at 20.01m core depth yielded zircons dated at 2434±1.2Ma (±6.6Myr including decay constant uncertainties) that we interpret as a magmatic age. These data, combined with dates from underlying intrusions, indicate deposition of the Polisarka Sedimentary Formation diamictites and underlying carbonates during an interval of time from ca. 2430 to 2440Ma. The carbonate rocks, which likely originally included aragonitic limestones, were deposited mostly in a deep-water setting (i.e. at least below storm wave base) and occur below the diamictite. They record two inorganic carbon δ13C excursions, from values of ca. 0‰ to minima of ca. -5.4‰, as the contact with the overlying diamictite is approached. The older (stratigraphically lower) excursion occurs about 9m below the base of the diamictic units and the younger one at 1m below. Throughout that interval, Mg/Ca ratios correlate strongly with δ13C (n=38, r=0.85), and combined with petrographic observations, this indicates that the first (stratigraphically lower) excursion was modified by secondary alteration and the second is recorded in resedimented dolostone clasts. It is tempting to speculate that these dolostone clasts were deposited in penecontemporaneous shallow-marine waters, and that their low δ13C values might reflect input of oxidised atmospheric methane to the ocean surface (and therefore the cause of the glaciation); the dolostones were subsequently resedimented into the deeper marine settings. However this must be left as a hypothesis to be tested when further age-constrained contemporaneous pre-glacial carbonate sections are found. © 2013 Elsevier B.V.
cited By 27
Keywords: aragonite; carbon isotope; carbonate rock; deposition; diamictite; dolostone; geochemistry; geochronology; glaciation; inorganic carbon; methane; outcrop; oxidation; Proterozoic; sedimentology; tuff; volcanic ash; Kola Peninsula; Murmansk [Russian Federation]; Russian Federation

Eger Rift ICDP: An observatory for study of non-volcanic, mid-crustal earthquake swarms and accompanying phenomena - Dahm, T.; Hrubcov'a, P.; Fischer, T.; Hor'alek, J.; Korn, M.; Wagner, D. (Scientific Drilling, 2013)
cited By 17

El'gygytgyn impact crater, Chukotka, Arctic Russia: Impact cratering aspects of the 2009 ICDP drilling project - Koeberl, C.; Pittarello, L.; Reimold, W.U.; Raschke, U.; Brigham-Grette, J.; Melles, M.; Minyuk, P. (Meteoritics and Planetary Science, 2013)
The El'gygytgyn impact structure in Chukutka, Arctic Russia, is the only impact crater currently known on Earth that was formed in mostly acid volcanic rocks (mainly of rhyolitic, with some andesitic and dacitic, compositions). In addition, because of its depth, it has provided an excellent sediment trap that records paleoclimatic information for the 3.6 Myr since its formation. For these two main reasons, because of the importance for impact and paleoclimate research, El'gygytgyn was the subject of an International Continental Scientific Drilling Program (ICDP) drilling project in 2009. During this project, which, due to its logistical and financial challenges, took almost a decade to come to fruition, a total of 642.3 m of drill core was recovered at two sites, from four holes. The obtained material included sedimentary and impactite rocks. In terms of impactites, which were recovered from 316.08 to 517.30 m depth below lake bottom (mblb), three main parts of that core segment were identified: from 316 to 390 mblb polymict lithic impact breccia, mostly suevite, with volcanic and impact melt clasts that locally contain shocked minerals, in a fine-grained clastic matrix; from 385 to 423 mblb, a brecciated sequence of volcanic rocks including both felsic and mafic (basalt) members; and from 423 to 517 mblb, a greenish rhyodacitic ignimbrite (mostly monomict breccia). The uppermost impactite (316-328 mblb) contains lacustrine sediment mixed with impact-affected components. Over the whole length of the impactite core, the abundance of shock features decreases rapidly from the top to the bottom of the studied core section. The distinction between original volcanic melt fragments and those that formed later as the result of the impact event posed major problems in the study of these rocks. The sequence that contains fairly unambiguous evidence of impact melt (which is not very abundant anyway, usually less than a few volume%) is only about 75 m thick. The reason for this rather thin fallback impactite sequence may be the location of the drill core on an elevated part of the central uplift. A general lack of large coherent melt bodies is evident, similar to that found at the similarly sized Bosumtwi impact crater in Ghana that, however, was formed in a target composed of a thin layer of sediment above crystalline rocks. © The Meteoritical Society, 2013.
cited By 28

Enhanced geothermal system potential for sites on the eastern Snake River Plain, Idaho - Podgorney, R.; McCurry, M.; Wood, T.; McLing, T.; Ghassemi, A.; Welhan, J.; Mines, G.; Plummer, M.; Moore, J.; Fairley, J.; Wood, R. (Transactions - Geothermal Resources Council, 2013)
The geologic characteristics and evolution of the Eastern Snake River Plain are consistent with transfer of large amounts of magma advected heat at mid- to upper-crustal levels. We speculate that some of this heat is stored below surficial basalt lavas, within underlying dense, hydrothermally altered rhyolites that infill large nested calderas. Cryptic hydrothermal systems may occur within caldera-related fracture systems, or megabreccias near caldera collapse scarps. Blind hot zones are also possible below young chemically evolved volcanoes on the ESRP. Other factors in addition to high temperatures and high heat flow that support EGS development are also prevalent on the ESRP. A number of deep exploration wells exist, and hundreds groundwater wells provide additional information on the character and makeup of the subsurface. The abundant cold groundwater resource can provide a significant heat sink for power generation, and also provide working fluid and makeup water as necessary. Regional stress and earthquake data suggest that the Plain is extensional to isotropic and quiet. The seismic risks of the eastern Snake River Plain have been extensively investigated because of the nuclear facilities at Idaho National Laboratory. The epicenter of the 1983 (magnitude 7.3) Borah earthquake was located about 100km (70 miles) from INL's nuclear facilities, but no significant damage occurred. This is attributed to the alternating layers of hard basalt and soft sediment that lie beneath the Snake River Plain. This attenuation reduces the seismic risk from natural and induced seismic occurrences. Additional studies are currently underway to better understand the EGS potential for the eastern SRP. These include GIS and VSRP analysis of existing data, new geotechnical and geomechanical analysis of core samples, geochemical studies of water-rock interaction, and numerical modeling studies of fracturing, fluid flow, and heat recovery.
cited By 3
Keywords: Alternating layers; Deep exploration wells; Enhanced geothermal systems; Geologic characteristics; Hydrothermal system; Idaho national laboratories; Snake river plains; Water rock interactions; Basalt; Geothermal fields; Geothermal wells; Groundwater; Groundwater resources; Heat transfer; Models; Nuclear energy; Rivers; Waste heat; Earthquakes

Environment and climate of the last 51,000years - new insights from the Potrok Aike maar lake Sediment Archive Drilling prOject (PASADO) - Zolitschka, B.; Anselmetti, F.; Ariztegui, D.; Corbella, H.; Francus, P.; L{ucke, A.; Maidana, N.I.; Ohlendorf, C.; Sch{abitz, F.; Wastegård, S. (Quaternary Science Reviews, 2013)
In this introductory paper we summarize the history and achievements of the Potrok Aike maar lake Sediment Archive Drilling prOject (PASADO), an interdisciplinary project embedded in the International Continental Scientific Drilling Program (ICDP). The stringent multiproxy approach adopted in this research combined with radiocarbon and luminescence dating provided the opportunity to synthesize a large body of hydrologically relevant data from Laguna Potrok Aike (southern Patagonia, Argentina). At this site, lake level was high from 51ka until the early Holocene when the Southern Hemisphere Westerlies (SHW) were located further to the north. At 9.3kacal.BP the SHW moved southward and over the latitude of the study area (52°S) causing a pronounced negative water balance with a lake level decrease of more than 50m. Two millennia later, the SHW diminished in intensity and lake level rose to a subsequent maximum during the Little Ice Age. Since the 20th century, a strengthening of the SHW increased the evaporative stress resulting in a more negative water balance. A comparison of our data with other hydrological fluctuations at a regional scale in south-eastern Patagonia, provides new insights and also calls for better chronologies and high-resolution records of climate variability. © 2012 Elsevier Ltd.
Keywords: Argentina; Laguna Potrok Aike; Santa Cruz [Argentina]; Climatology; Sedimentology; Argentina; Holocenes; ICDP; Lake levels; Last glacial; Patagonia; Southern Hemispheric Westerlies; Water balance; Holocene; interdisciplinary approach; lacustrine deposit; luminescence dating; maar; radiocarbon dating; Southern Hemisphere; twentieth century; water budget; Lakes

Evidence for high salinity of Early Cretaceous sea water from the Chesapeake Bay crater - Sanford, W.E.; Doughten, M.W.; Coplen, T.B.; Hunt, A.G.; Bullen, T.D. (Nature, 2013)
High-salinity groundwater more than 1,000 metres deep in the Atlantic coastal plain of the USA has been documented in several locations, most recently within the 35-million-year-old Chesapeake Bay impact crater. Suggestions for the origin of increased salinity in the crater have included evaporite dissolution, osmosis and evaporation from heating associated with the bolide impact. Here we present chemical, isotopic and physical evidence that together indicate that groundwater in the Chesapeake crater is remnant Early Cretaceous North Atlantic (ECNA) sea water. We find that the sea water is probably 100-145 million years old and that it has an average salinity of about 70 per mil, which is twice that of modern sea water and consistent with the nearly closed ECNA basin. Previous evidence for temperature and salinity levels of ancient oceans have been estimated indirectly from geochemical, isotopic and palaeontological analyses of solid materials in deep sediment cores. In contrast, our study identifies ancient sea water in situ and provides a direct estimate of its age and salinity. Moreover, we suggest that it is likely that remnants of ECNA sea water persist in deep sediments at many locations along the Atlantic margin. © 2013 Macmillan Publishers Limited. All rights reserved.
cited By 14
Keywords: ground water; sea water; bolide; coastal plain; crater; Cretaceous; dissolution; evaporite; groundwater; impact; osmosis; salinity; seawater; article; chemical analysis; coastal plain; dissolution; evaporation; heating; Lower Cretaceous; osmosis; priority journal; salinity; sediment; temperature; Atlantic Ocean; Bays; Geological Phenomena; Groundwater; Salinity; Seawater; Atlantic Coastal Plain; Chesapeake Bay; United States

Extracting paleoclimate signals from sediment laminae: An automated 2-D image processing method - Gan, Stoney Q.; Scholz, Christopher A. (Computers and Geosciences, 2013)
Lake sediments commonly contain laminations and the occurrence and quantitative attributes of these microstrata contain signals of their depositional environment, limnological conditions, and past climate. However, the identification and measurement of laminae and their attributes remains a largely semi-manual process that is tedious, labor intensive, but subject to human error. Here, we present a method to automatically measure and accurately extract lamina properties from sediment core images. This method is comprised of four major components: (1) image enhancement that includes noise reduction and contrast enhancement to improve signal-to-background ratio and resolution of laminae; (2) identification of 1-D laminae for a user-chosen area in an image; (3) laminae connectivity analyses on the 1-D laminae to obtain a lamina stratigraphy; and (4) extraction and retrieval of the primary and derived lamination stratigraphic data. Sediment core images from Lake Hitchcock and Lake Bosumtwi were used for algorithm development and testing. Our experiments show a complete match between laminae produced by the software and manual process for images from Lake Hitchcock. Quantitative comparisons reveal an insignificant discrepancy in the number of laminae identified automatically by the software and manually by researchers, and in over 90% of the cases the position mismatch of individual laminae is less than one pixel between the software and the manual method for the experimental images from Lake Bosumtwi. © 2012 Elsevier Ltd.
Keywords: Ashanti; Ghana; Lake Bosumtwi; Algorithms; Image matching; Lakes; Laminating; Sedimentology; Sediments; Stratigraphy; 2-D laminae; Algorithm development; Best fit algorithm; Connectivity analysis; Contrast Enhancement; Depositional environment; Human errors; Image processing - methods; Labor intensive; Lake sediments; Lamina properties; Limnological conditions; Manual methods; Manual process; Paleoclimates; Quantitative attributes; Quantitative comparison; Sediment core; Signal-to-background ratio; Stratigraphic data; algorithm; identification method; image analysis; image processing; lacustrine deposit; paleoclimate; quantitative analysis; sediment core; Image processing

Geochemical studies of the SUBO 18 (Enkingen) drill core and other impact breccias from the Ries crater, Germany - Reimold, W.U.; Mcdonald, I.; Schmitt, R.-T.; Hansen, B.; Jacob, J.; Koeberl, C. (Meteoritics and Planetary Science, 2013)
Suevite and melt breccia compositions in the boreholes Enkingen and Polsingen are compared with compositions of suevites from other Ries boreholes and surface locations and discussed in terms of implications for impact breccia genesis. No significant differences in average chemical compositions for the various drill cores or surface samples are noted. Compositions of suevite and melt breccia from southern and northeastern sectors of the Ries crater do not significantly differ. This is in stark contrast to the published variations between within-crater and out-of-crater suevites from northern and southern sectors of the Bosumtwi impact structure, Ghana. Locally occurring alteration overprint on drill cores-especially strong on the carbonate-impregnated suevite specimens of the Enkingen borehole-does affect the average compositions. Overall, the composition of the analyzed impact breccias from Ries are characterized by very little macroscopically or microscopically recognized sediment-clast component; the clast populations of suevite and impact melt breccia are dominated consistently by granitic and intermediate granitoid components. The Polsingen breccia is significantly enriched in a dioritic clast component. Overall, chemical compositions are of intermediate composition as well, with dioritic-granodioritic silica contents, and relatively small contributions from mafic target components. Selected suevite samples from the Enkingen core have elevated Ni, Co, Cr, and Ir contents compared with previously analyzed suevites from the Ries crater, which suggest a small meteoritic component. Platinum-group element (PGE) concentrations for some of the enriched samples indicate somewhat elevated concentrations and near-chondritic ratios of the most immobile PGE, consistent with an extraterrestrial contribution of 0.1-0.2% chondrite-equivalent. © The Meteoritical Society, 2013.
cited By 9

Geochemical consequences of widespread clay mineral formation in Mars' ancient crust - Ehlmann, B.L.; Berger, G.; Mangold, N.; Michalski, J.R.; Catling, D.C.; Ruff, S.W.; Chassefière, E.; Niles, P.B.; Chevrier, V.; Poulet, F. (Space Science Reviews, 2013)
Clays form on Earth by near-surface weathering, precipitation in water bodies within basins, hydrothermal alteration (volcanic- or impact-induced), diagenesis, metamorphism, and magmatic precipitation. Diverse clay minerals have been detected from orbital investigation of terrains on Mars and are globally distributed, indicating geographically widespread aqueous alteration. Clay assemblages within deep stratigraphic units in the Martian crust include Fe/Mg smectites, chlorites and higher temperature hydrated silicates. Sedimentary clay mineral assemblages include Fe/Mg smectites, kaolinite, and sulfate, carbonate, and chloride salts. Stratigraphic sequences with multiple clay-bearing units have an upper unit with Al-clays and a lower unit with Fe/Mg-clays. The typical restriction of clay minerals to the oldest, Noachian terrains indicates a distinctive set of processes involving water-rock interaction that was prevalent early in Mars history and may have profoundly influenced the evolution of Martian geochemical systems. Current analyses of orbital data have led to the proposition of multiple clay-formation mechanisms, varying in space and time in their relative importance. These include near-surface weathering, formation in ice-dominated near-surface groundwaters, and formation by subsurface hydrothermal fluids. Near-surface, open system formation of clays would lead to fractionation of Mars' crustal reservoir into an altered crustal reservoir and a sedimentary reservoir, potentially involving changes in the composition of Mars' atmosphere. In contrast, formation of clays in the subsurface by either aqueous alteration or magmatic cooling would result in comparatively little geochemical fractionation or interaction of Mars' atmospheric, crustal, and magmatic reservoirs, with the exception of long-term sequestration of water. Formation of clays within ice would have geochemical consequences intermediate between these endmembers. We outline the future analyses of orbital data, in situ measurements acquired within clay-bearing terrains, and analyses of Mars samples that are needed to more fully elucidate the mechanisms of martian clay formation and to determine the consequences for the geochemical evolution of the planet. © 2012 Springer Science+Business Media B.V.
cited By 91

Geochemical and paleomagnetic variations in basalts from the wendell regional aquifer systems analysis (RASA) drill core: Evidence for magma recharge and assimilation-fractional crystallization from the central snake river plain, Idaho - Jean, M.M.; Shervais, J.W.; Champion, D.E.; Vetter, S.K. (Geosphere, 2013)
The temporal and magmatic evolution of central Snake River Plain (SRP; Idaho, USA) olivine tholeiites erupted within the past 4 m.y. is evaluated here. This investigation correlates and merges both geochemical and paleomagnetic measurements to constrain the volcanic history recovered from the 340 m Regional Aquifer Systems Analysis (RASA) test well located near Wendell, Idaho. Only a handful of studies have accomplished this task of shedding light on the chemical stratigraphy of the SRP and the petrogenesis of basalts with depth, and therefore through time. Paleomagnetic relationships suggest that time breaks between individual lava flows represent a few years to decades, time breaks between flow groups represent at least a couple of hundred years or possibly much longer, while significant hiatuses in volcanism, revealed by thick sediment packages or polarity reversals (both are evidenced in this well), are inferred to last thousands to tens of thousands of years. Major element geochemistry from 52 basaltic lava flows demonstrates near primitive compositions (i.e., 10 wt% MgO) and tholeiitic iron enrichment trends, similar to lavas from the eastern SRP. Trace element concentrations are similar to those of ocean island basalts, with enriched Ba and Pb, and light rare earth element (REE)/heavy REE ratios similar to those of many Neogene volcanics of the western Cordillera. When combined, we identify a total of 11 flow groups, which we also classify as fractionation or recharge on the basis of decreasing or increasing MgO weight percent with depth. Taking into consideration these trends, we review the potential recharge, fractionation, and assimilation processes that characterize much of SRP olivine tholeiite, and conclude that assimilation, in combination with fractional crystallization, is the dominant petrogenesis for the basalts in the central SRP. Although fractionation of Wendell parent magmas was accompanied by assimilation of crustal material, this could not have been assimilation of ancient cratonic crust. The geochemical cycles observed in this well are inferred to represent fractionation and recharge of basaltic magma from a series of sill-like layered mafic intrusions located in the middle crust, similar to what has been proposed for the processes that control the eruptive history of basalts in the eastern SRP. © 2013 Geological Society of America.
cited By 7
Keywords: aquifer; basalt; concentration (composition); fractional crystallization; igneous geochemistry; igneous intrusion; lava flow; magma; ocean island basalt; paleomagnetism; petrogenesis; tholeiite; trace element; volcanism; Idaho; Snake River Plain; United States

Geochemical and isotopic characteristics of shallow groundwater within the Lake Qinghai catchment, NE Tibetan Plateau - Xiao, Jun; Jin, Zhangdong; Zhang, Fei (Quaternary International, 2013)
Major ions, isotopic ratios of strontium (87Sr/86Sr), hydrogen (δD) and oxygen (δ18O) of groundwater samples were analyzed to decipher spatial variation, controlling factors, solute sources, and the rechargesource of shallow groundwaters within the Lake Qinghai catchment. Shallow groundwaters in this area are slightly alkaline, with 97% being fresh water of good quality, though there are high concentrations of nitrate and sulfide in Buha and lakeside groundwaters. Most of the shallow groundwatersare of the Ca2+-HCO3- type, whereas part of groundwaters surrounding the lake (LS) belongs to the Na+-Cl- type as lake water (QHL). Groundwater geochemistry is controlled by regional lithological association, ion exchange, and mineral precipitation. The dissolved Sr concentrations and 87Sr/86Sr ratios vary from 1.0 to 15.6μmol/L, and from 0.709859 to 0.715779, respectively. The first quantitative calculation in groundwater using a forward model shows that 40% of dissolved Sr is from carbonate weathering, 33% from evaporite dissolution, 17% from silicate weathering, and the remainder from atmospheric input for the whole catchment. Carbonate weathering dominates groundwater geochemistry in Shaliu (SL), Hargai (HG) and Buha (BH) samples, while evaporite dissolution dominates LS and Daotang (DT) samples. δD and δ18O data show that rain water is the major recharge source of both river water and shallow groundwater within the Lake Qinghai catchment. Qinghai Lake water is characterized by Buha-type water, but its Sr geochemistry is different from the shallow groundwater due to carbonate precipitation. Although shallow groundwater contributes 5% of the dissolved Sr to the QHL, groundwater must be taken into account when the chemistry and budget of lake water are characterized. © 2013 Elsevier Ltd and INQUA.
Keywords: China; Qinghai; Qinghai Lake; Qinghai-Xizang Plateau; carbonate; concentration (composition); groundwater; hydrochemistry; hydrogen isotope; ion exchange; isotopic composition; isotopic ratio; lake water; lithology; nitrate; oxygen isotope; rainwater; recharge; river water; solute; spatial variation; strontium isotope; sulfide; weathering

Gas hydrates - A new type of fossil fuel [Gazohydraty - Nowy rodzaj paliw kopalnych] - Zag'orski, J. (Przeglad Geologiczny, 2013)
Unconventional hydrocarbon resources in last years draw the attention of petroleum geologists. Significant position take the gas hydrates, first of all due to occurrences in many regions of the world and the size of the potential resources. These accumulations are localized in Arctic regions with permafrost as well as offshore. First gas hydrate discovery occurred in Siberian gas field Messoyakha in permafrost zone and similar accumulations were found in Alaska. Offshore occurrences are located mainly on continental slope. Drillings and samples from permafrost and seabed provided vast amount of data concerned conditions of gas hydrates formation and concentration and allow to better constrain the volume of hydrate-bearing sediments and their gas yield. Resources of hydrocarbons contained in gas hydrate deposits represent a vast energy source potential. Still essential problem is to elaborate efficient commercial production technology. So far positive developments regard only laboratory or semi-commercial scale.
cited By 2
Keywords: continental slope; fossil fuel; gas field; gas hydrate; hydrocarbon resource; methane; mud volcano; permafrost; submarine landslide; Alaska; Arctic; China; Kuparuk River; Nankai; Siberia; Tianjin; United States

Fluid-level monitoring using a distributed temperature sensing system during a methane hydrate production test - Sakiyama, N.; Fujii, K.; Pimenov, V.; Parshin, A.; Yamamoto, K.; Write, J.F. (Society of Petroleum Engineers - International Petroleum Technology Conference 2013, IPTC 2013: Challenging Technology and Economic Limits to Meet the Global Energy Demand, 2013)
Temperature profiles and their transient behaviors obtained using a distributed temperature sensing (DTS) system were measured while monitoring wellbore fluid levels during a methane hydrate production test. The temperature data were obtained in 2008 as part of the JOGMECTNRCan/Aurora Mallik 2007 2008 Gas Hydrate Production Research Well Program. Methane hydrate is known to be stabilized under low-temperature and high-pressure conditions. In the Gas Hydrate Production Research Well Program, a depressurization method using an electric submergible pump (ESP) was employed to dissociate the hydrate in the reservoir. For recovering the produced gas and fluid without resynthesizing the hydrate after the dissociation, it was essential that the temperature of the produced fluids flowing up the tubing be controlled. According to our numerical temperature simulation, the annulus fluid level around the tubing is one of important factors that govern the tubing fluid temperature during the methane hydrate production. If the annulus fluid level is high, the tubing fluid temperature becomes so low that methane hydrate can potentially be formed inside the tubing; thus, understanding fluid levels during methane hydrate production is important for flow assurance as well as bottomhole pressure control. The conventional method for estimating fluid levels in a wellbore employs an acoustic wave reflection technique; however, the uracy of the survey is subjected to assumption of an acoustic velocity which depends on pressure, temperature, and gas types. On the other hand, estimating fluid levels with a DTS temperature profile is thought to be a more direct method. Although it is not widely known, several papers indicate that the feasibility of estimating fluid levels with the DTS system when the fluid level is static. In this paper, we demonstrate the feasibility of estimating dynamic fluid levels using a DTS system. The dynamic trend in estimated fluid levels with the DTS system shows qualitatively good agreement to that estimated with the pressure on the completion assembly and the pressure at the casinghead. The difference in fluid levels between the DTS temperature-based and the pressure-based methods quantitatively explains a void traction in the two-phase flow of the fluid and the gas. The analysis presented in this paper is based on field data collected during methane hydrate production, but it is potentially applicable to any conventional production scheme that employs artificial lift. Copyright © (2013) by the Society of Petroleum Engineers.
cited By 6
Keywords: Depressurization methods; Distributed temperature sensing systems; Gas-hydrate production; High-pressure condition; Methane hydrate productions; Pressure-based method; Temperature profiles; Temperature simulations; Acoustic wave velocity; Acoustic wave velocity measurement; Bottom hole pressure; Energy management; Estimation; Gases; Hydration; Low temperature production; Methane; Oil field equipment; Petroleum engineering; Temperature control; Temperature sensors; Tubing; Gas hydrates

First results from HOTSPOT: The Snake River plain scientific drilling project, Idaho, U.S.A. - Shervais, John W.; Nielson, Dennis; Evans, James P.; Christiansen, Eric H.; Morgan, Lisa; Pat Shanks, W.C.; Prokopenko, Alexander A.; Lachmar, Thomas; Liberty, Lee M.; Blackwell, David D.; Glen, Jonathan M.; Champion, Duane; et al. (Scientific Drilling, 2013)
HOTSPOT is an international collaborative effort to understand the volcanic history of the Snake River Plain (SRP). The SRP overlies a thermal anomaly, the Yellowstone-Snake River hotspot, that is thought to represent a deep-seated mantle plume under North America. The primary goal of this project is to document the volcanic and stratigraphic history of the SRP, which represents the surface expression of this hotspot, and to understand how it affected the evolution of continental crust and mantle. An additional goal is to evaluate the geothermal potential of southern Idaho. Project HOTSPOT has completed three drill holes. (1) The Kimama site is located along the central volcanic axis of the SRP; our goal here was to sample a long-term record of basaltic volcanism in the wake of the SRP hotspot. (2) The Kimberly site is located near the margin of the plain; our goal here was to sample a record of high-temperature rhyolite volcanism associated with the underlying plume. This site was chosen to form a nominally continuous record of volcanism when paired with the Kimama site. (3) The Mountain Home site is located in the western plain; our goal here was to sample the Pliocene-Pleistocene transition in lake sediments at this site and to sample older basalts that underlie the sediments. We report here on our initial results for each site, and on some of the geophysical logging studies carried out as part of this project.
Keywords: Distributed computer systems; Infill drilling; Stratigraphy; Volcanoes; Basaltic volcanism; Continental crusts; Geophysical logging; Geothermal potential; Scientific drilling; Snake river plains; Surface expression; Thermal anomalies; Rivers

Far-deep core archive and database - Lepland, A.; Mesli, M.; Conze, R.; Fabian, K.; Fallick, A.E.; Kump, L.R. (Frontiers in Earth Sciences, 2013)
cited By 2

Diatoms of Europe: Luticola and Luticolopsis Vol. 7 - Levkov, Z; Metzeltin, D; Pavlov, A (Koeltz Scientific Books, Konigstein, 2013)

Seismic and sedimentological evidence of an early 6th century AD earthquake at Lake Ohrid (Macedonia/Albania) - Wagner, B.; Francke, Alexander; Sulpizio, R.; Zanchetta, Giovanni; Lindhorst, Katja; Krastel, Sebastian; Vogel, Hendrik; Rethemeyer, Janet; Daut, Gerhard; Grazhdani, Andon; Lushaj, Bashkim; Trajanovski, Sasho (Climate of the Past Discussions, 2012)

Observation and scaling of microearthquakes from the Taiwan Chelungpu-fault borehole seismometers - Lin, Y.-Y.; Ma, K.-F.; Oye, V. (Geophysical Journal International, 2012)
Microearthquakes with magnitude down to 0.3 were detected by the Taiwan Chelungpu-fault Drilling Project Borehole Seismometers (TCDPBHS). Despite the large coseismic slip of 12m at the drill site during the 1999 Chi-Chi earthquake, our studies show very little seismicity near the TCDPBHS drill site 6 yr after the Chi-Chi main shock. The microearthquakes clustered at a depth of 9-12 km, where the Chelungpu thrust fault turns from a 30° dipping into the horizontal decollement of the Taiwan fold-and-thrust tectonic structure. Continuous GPS surveys did not observe post-slip deformation at the larger slip region and no seismicity was observed near the drill site. Therefore we suggest that the thrust belt above the decollement is locked during this interseismic period. We further investigated source parameters of 242 microearthquakes by fitting ω -2-shaped Brune source spectra to our observation data using a frequency-independent Q model. We find that the static stress drop increases significantly with increasing seismic moment. However, due to the intense debate on this topic of scaling-relations and the related self-similarity of earthquakes, we further improve the data analysis and correct for path and site effects using the Projected Landweber Deconvolution (PLD) method for events within some clusters. The PLD method analyses the source time functions of the larger and the smaller event by an iterative technique. As a result we received source dimensions and stress drops of larger events including path and site effect corrections. The results from the PLD method are less scattered and also show a positive relation between static stress drop and seismic moment. We find a similar positive trend for the apparent stress scaling with seismic moment. © 2012 The Authors Geophysical Journal International © 2012 RAS.
cited By 13
Keywords: Apparent stress; ChiChi earthquake; Coseismic slips; Drill sites; Drilling projects; Earthquake source; GPS survey; Inter-seismic periods; Iterative technique; Main shock; Method analysis; Micro-earthquakes; Observation data; Seismic moment; Seismotectonics; Self-similarities; Site effects; Source dimensions; Source parameters; Source time functions; Static stress; Stress drop; Tectonic structure; Thrust belts; Thrust faults; Boring; Drills; Drops; Faulting; Seismographs; Earthquakes; Chi-Chi earthquake 1999; decollement; deformation; earthquake magnitude; fold and thrust belt; microearthquake; seismic moment; seismicity; seismograph; seismotectonics; source parameters; tectonic structure; thrust fault; Chelungpu Fault Zone; Taiwan

Physical properties of surface outcrop cataclastic fault rocks, Alpine Fault, New Zealand - Boulton, C.; Carpenter, B.M.; Toy, V.; Marone, C. (Geochemistry, Geophysics, Geosystems, 2012)
We present a unified analysis of physical properties of cataclastic fault rocks collected from surface exposures of the central Alpine Fault at Gaunt Creek and Waikukupa River, New Zealand. Friction experiments on fault gouge and intact samples of cataclasite were conducted at 30-33MPa effective normal stress (n) using a double-direct shear configuration and controlled pore fluid pressure in a true triaxial pressure vessel. Samples from a scarp outcrop on the southwest bank of Gaunt Creek display (1) an increase in fault normal permeability (k=7.45×10-20 m2 to k=1.15×10-16 m2), (2) a transition from frictionally weak (=0.44) fault gouge to frictionally strong (=0.50-0.55) cataclasite, (3) a change in friction rate dependence (a-b) from solely velocity strengthening, to velocity strengthening and weakening, and (4) an increase in the rate of frictional healing with increasing distance from the footwall fluvioglacial gravels contact. At Gaunt Creek, alteration of the primary clay minerals chlorite and illite/muscovite to smectite, kaolinite, and goethite accompanies an increase in friction coefficient (=0.31 to =0.44) and fault-perpendicular permeability (k=3.10×10-20 m2 to k=7.45×10-20 m2). Comminution of frictionally strong (=0.51-0.57) cataclasites forms weaker (=0.31-0.50) foliated cataclasites and fault gouges with behaviors associated with aseismic creep at low strain rates. Combined with published evidence of large magnitude (Mw∼8) surface ruptures on the Alpine Fault, petrological observations indicate that shear failure involved frictional sliding within previously formed, velocity-strengthening fault gouge. Copyright 2012 by the American Geophysical Union.
cited By 76
Keywords: Clay alteration; Friction; Grinding (comminution); Kaolin; Kaolinite; Mechanical permeability; Physical properties; Shear flow; Strain rate; Strengthening (metal); Tribology; Alpine Faults; Cataclasite; Effective normal stress; Fault gouge; Fault rock; Friction coefficients; Frictional sliding; Low strain rates; New zealand; Pore fluid pressure; Rate dependence; Shear failure; Smectites; Surface exposure; surface rupture; Surface ruptures; True triaxial; Unified analysis; Surface properties; cataclasite; earthquake rupture; fault; fault gouge; fault zone; friction; outcrop; permeability; physical property; plate tectonics; Alpine Fault Zone; New Zealand; South Island

Past and present mercury flux to a West African crater lake (Lake Bosomtwe/Bosumtwi, Ghana) - Poste, Amanda E.; Muir, Derek C.G.; Otu, Megan K.; Hall, Roland I.; Hecky, Robert E. (Science of the Total Environment, 2012)
Lake sediment cores have been used to reconstruct mercury deposition patterns in many parts of the world; however, no studies to date have used these methods in West Africa, nor are there any published measurements of mercury deposition to this region. We measured mercury in a 210Pb dated sediment core from a meromictic crater lake in West Africa (Lake Bosomtwe, Ghana). Lake Bosomtwe has a very small catchment area to lake area ratio (1.1) and the sediment mercury profile is expected to reflect past and present atmospheric mercury deposition to the lake. Mercury concentrations in sediments as well as mercury flux to the sediments increased from the mid-1800s to latter half of the 1900s, however there has been a sharp decline in mercury flux to Lake Bosomtwe in recent decades. The recent decline in mercury flux to Lake Bosomtwe's sediments does not appear to be consistent with trends in local, regional or global mercury emissions, and may instead reflect declining global atmospheric mercury concentrations or declining European emissions, highlighting the importance of long-range atmospheric transport of mercury. © 2012 Elsevier B.V.
Keywords: Air Movements; Air Pollution; Environmental Monitoring; Environmental Pollution; Geologic Sediments; Ghana; History; 19th Century; History; 20th Century; Lakes; Mercury; Ashanti; Ghana; Lake Bosumtwi; Anoxic sediments; Atmospheric chemistry; Atmospheric movements; Lakes; Lead; Mercury (metal); Sedimentology; cesium 137; lead 210; mercury; Africa; Atmospheric mercury; Atmospheric mercury deposition; Atmospheric transport; Crater lake; Global mercury emissions; Lake areas; Lake sediments; Long-range atmospheric transport; Mercury concentrations; Mercury depositions; Mercury fluxes; Past and present; Sediment core; Small catchment; West Africa; catchment; concentration (composition); crater lake; deposition; lacustrine deposit; mercury (element); meromictic lake; sediment core; article; catchment; chemical analysis; chemical composition; concentration (parameters); controlled study; geographic distribution; Ghana; isotope labeling; lake; lake sediment; pollution transport; priority journal; sedimentation rate; trend study; water pollution; Lake pollution

Petrographic investigation of melt and matrix relationships in Chicxulub crater Yaxcopoil-1 brecciated melt rock and melt rock-bearing suevite (846-885m, units 4 and 5) - Nelson, M.J.; Newsom, H.E.; Spilde, M.N.; Salge, T. (Geochimica et Cosmochimica Acta, 2012)
The drill core from the International Continental Drill Program's Chicxulub Scientific Drilling Project Yaxcopoil-1 (Yax-1) borehole, in the annular trough of the Chicxulub crater, exhibits from 794 to 895. m a continuous sequence of impactites consisting of reworked fallout, fallout suevite, and brecciated impact melt rock. These impact breccias exhibit a complex history of deposition, fracturing, matrix emplacement and hydrothermal alteration. Detailed investigation of the mineralogy and chemistry of these breccias has led to a better understanding of the complex events involved in their formation. We find that the paragenesis of the brecciated impact melt rock (unit 5, 861-885. m) involved fracturing of melt rock and early K-metasomatism during a hydrothermal alteration episode as suggested by earlier work. However, the present work has identified the role of multiple episodes of precipitation of Mg-rich phyllosilicates and formation and dissolution of accessory minerals in a relatively high temperature (>300. °C) hydrothermal event. The earliest matrix formation event involved precipitation of Mg-rich phyllosilicate, accessory quartz, calcite, apatite, and andradite garnet from a hydrothermal fluid with a brine or seawater component. The fluid could have partly incorporated elements and shock-metamorphosed mineral phases derived from sedimentary lithologies, including calcite and dolomite that underwent complex phase transformations such as melting, decomposition and possible back-reactions. The discovery of andradite garnet in the matrix confirms the presence of an early high temperature hydrothermal event previously identified by mineralogical, stable isotope and fluid inclusion studies. The mineral assemblage, including Mg-rich saponite, suggests the involvement of seawater by comparison with similar alteration assemblages in hydrothermal systems involving seawater around the world. The presence of a later, low-temperature phase of the hydrothermal system, with different fluid chemistry is indicated by the partial dissolution of andradite garnet, and continued precipitation of matrix phyllosilicate minerals, but without the accessory quartz, abundant calcite or andradite, and without an accompanying K-metasomatism event. © 2012 Elsevier Ltd.
cited By 11

Petrologic characteristics and genesis of dolostone from the campanian of the SK-I well core in the Songliao Basin, China - Gao, X.; Wang, P.; Li, D.; Peng, Q.; Wang, C.; Ma, H. (Geoscience Frontiers, 2012)
The well SK-I in the Songliao Basin is the first scientific borehole targeting the continental Cretaceous strata in China. Oval concretions, thin laminae and beds of dolostone are found intercalated within mudstone and organic-rich black shale in the Nenjiang Formation of Campanian age. Low ordered ferruginous dolomite is composed of euhedral-subhedral rhombs with cloudy nucleus and light rims formed during the diagenesis, which are typical features of replacement. The heavy carbon isotopes (δ13CPDB - 1.16-16.0) are results of both the fermentation of organic matter by microbes and degassing of carbon dioxide during the period of diagenesis, and the presence of light oxygen isotopes (δ18OPDB - 18.53∼-5.1) is a characteristic feature of fresh water influence which means the carbonate may have been altered by ground water or rainwater in the late diagenesis. Marine water incursions into the normally lacustrine basin have been proved by both the salinity of Z value and the occurrence of foraminifera in the same strata where dolomite occurs. Pyrite framboids observed by SEM are usually enclosed in the dolomite crystals or in the mudstones, supporting the sulfate reducing bacteria (SRB). The formation of both dolomite and pyrite are associated with marine water incursions, which not only supply magnesium ion for dolomite, but also result in limited carbonate precipitation in the basin. The presence of pyrite framboids indicates the development of an anoxic environment associated with salinity stratification in the lake. The dolomite in the Nenjiang Formation is the results of marine water incursions, diagenetic replacement of calcareous carbonate and sulfate reducing bacteria (SRB). © 2012 Elsevier B.V. All rights reserved.
cited By 8
Keywords: bacterium; black shale; borehole; Campanian; carbon isotope; carbonate; diagenesis; dolostone; lithostratigraphy; mudstone; oxygen isotope; petrology; precipitation (chemistry); pyrite; China; Songliao Basin; Foraminifera

Reading the Archive of Earth’s Oxygenation: Volume 1: The Palaeoproterozoic of Fennoscandia as Context for the Fennoscandian Arctic Russia-Drilling Early Earth Project - Melezhik, Victor; Prave, Anthony R; Fallick, Anthony E; Kump, Lee R; Strauss, Harald; Lepland, Aivo; Hanski, Eero J (Springer Science and Business Media, 2012)

Platinum group element abundances in the upper continental crust revisited - New constraints from analyses of Chinese loess - Park, J.-W.; Hu, Z.; Gao, S.; Campbell, I.H.; Gong, H. (Geochimica et Cosmochimica Acta, 2012)
Platinum group element (PGE) abundances in the upper continental crust (UCC) are poorly constrained with published values varying by up to an order of magnitude. We evaluated the validity of using loess to estimate PGE abundances in the UCC by measuring these elements in seven Chinese loess samples using a precise method that combines NiS fire assay with isotope dilution. Major and trace elements of the Chinese loess show a typical upper crustal composition and PGE abundances are consistent with literature data on Chinese loess, except for Ru, which is a factor of 10 lower than published values. We suggest that the high Ru data and RuN/IrN values of Chinese loess reported by Peucker-Ehrenbrink and Jahn (2001) (Geochem. Geophys. Geosys. 2, 2001GC000172) are an analytical artifact, rather than a true geochemical characteristic of loess because likely sources of loess are not significantly enriched in Ru and transport and deposition processes cannot preferentially enrich Ru in loess. The effect of eolian fractionation on PGE abundances in loess appears to be limited because Chinese loess from different locations shows similar PGE patterns and concentrations. This conclusion is supported by strong positive correlations between the PGE (except for Pt) and other compatible elements such as Fe2O3, Ni, Cr, Co. Using a compilation of PGE data for loess from China, Argentina and Europe, including our data but excluding one sample with an anomalously high Pt content, we propose average PGE abundances for global loess of Ir = 0.022 ppb (ng/g), Ru = 0.030 ppb, Rh = 0.018 ppb, Pt = 0.599 ppb, and Pd = 0.526 ppb, and suggest that these are the best current estimates for the PGE abundances of the UCC. © 2012 Elsevier Ltd.
cited By 56

Possible earthquake trigger for 6th century mass wasting deposit at Lake Ohrid (Macedonia/Albania) - Wagner, B.; Francke, A.; Sulpizio, R.; Zanchetta, G.; Lindhorst, K.; Krastel, S.; Vogel, H.; Rethemeyer, J.; Daut, G.; Grazhdani, A.; Lushaj, B.; Trajanovski, S. (Climate of the Past, 2012)
Lake Ohrid shared by the Republics of Albania and Macedonia is formed by a tectonically active graben within the south Balkans and suggested to be the oldest lake in Europe. Several studies have shown that the lake provides a valuable record of climatic and environmental changes and a distal tephrostratigraphic record of volcanic eruptions from Italy. Fault structures identified in seismic data demonstrate that sediments have also the potential to record tectonic activity in the region. Here, we provide an example of linking seismic and sedimentological information with tectonic activity and historical documents. Historical documents indicate that a major earthquake destroyed the city of Lychnidus (today: city of Ohrid) in the early 6th century AD. Multichannel seismic profiles, parametric sediment echosounder profiles, and a 10.08 m long sediment record from the western part of the lake indicate a 2 m thick mass wasting deposit, which is tentatively correlated with this earthquake. The mass wasting deposit is chronologically well constrained, as it directly overlays the AD 472/AD 512 tephra. Moreover, radiocarbon dates and cross correlation with other sediment sequences with similar geochemical characteristics of the Holocene indicate that the mass wasting event took place prior to the onset of the Medieval Warm Period, and is attributed it to one of the known earthquakes in the region in the early 6th century AD. © Author(s) 2012.
Keywords: Lake Ohrid; depositional environment; earthquake trigger; environmental change; geochemical method; Holocene; sedimentology; seismic data; tephrochronology; volcanic eruption

Projectile Identification in Terrestrial Impact Structures and Ejecta Material - Goderis, S.; Paquay, F.; Claeys, P. (Impact Cratering: Processes and Products, 2012)
cited By 37

Quaternary coastline evolution of Lake Ohrid (Macedonia/Albania) - Hoffmann, Nadine; Reicherter, Klaus; Gr{utzner, Christoph; H{urtgen, Jochen; Rudersdorf, Andreas; Viehberg, Finn A.; Wessels, Martin (Central European Journal of Geosciences, 2012)
Lake Ohrid (between FYR of Macedonia and Albania), situated in an active tectonic region of the Balkanides, is characterized by N - S trending active faults. To reconstruct the Holocene shoreline evolution we investigated the coastline using sediment cores and geophysical methods to image sedimentary and tectonic structures. We revealed areas of differing sedimentation regimes. The plains north and south of the lake are dominated by clastic input related to climate variations and uplift/erosion, whereas the steep western and eastern margins are controlled by recent tectonics. Furthermore, no evidence for a much higher lake-level during the Holocene was found in the plains north and south of the lake, except rare temporary floodings. This is supported by mappings of the limestone cliffs around Lake Ohrid, which yielded no evidence for abrasional platforms or notches as indicators for past highstands. © 2012 Versita Warsaw and Springer-Verlag Wien.

News and Views (2012)

Non-Gaussian gas hydrate grade simulation at the Mallik site, Mackenzie Delta, Canada - Dubreuil-Boisclair, C.; Gloaguen, E.; Bellefleur, G.; Marcotte, D. (Marine and Petroleum Geology, 2012)
For the past decades, gas hydrate reservoirs have beneficiated from an increasing attention in the academic and industrial worlds. As a result, there is a growing need to develop specific and comprehensive gas hydrate reservoir characterization methods. This study explores the use of a stochastic Bayesian algorithm to integrate well-logs and 3D acoustic impedance in order to estimate gas hydrate grades (product of saturation and total porosity) over a representative volume of the Mallik gas hydrate field, located in the Mackenzie Delta, Northwest Territories of Canada. First, collocated log data from boreholes Mallik 5L-38 and 2L-38 are used to estimate the statistical relationship between acoustic impedance and gas hydrate grades. Second, conventional stochastic Bayesian simulation is applied to generate multiple gas hydrate grade 3D fields integrating log data and lateral variability of 3D acoustic impedance. These equiprobable scenarios permit to quantify the uncertainty over the estimation, and identify zones where this uncertainty is greater. Contrary to conventional stochastic reservoir modeling workflows, the proposed method allows integrating non Gaussian and non linear distributions. This permits to handle bimodal distributions without using complex stochastic transforms. The results present gas hydrate grade values that are in accordance with well-log data. The relatively low standard deviation calculated at each pixel using all realizations suggests that gas hydrate grades is well explained by acoustic impedance and log data. © 2012 Elsevier Ltd.
cited By 34
Keywords: Bayesian algorithms; Bayesian simulation; Bimodal distribution; Gas hydrate reservoir; Log data; Non-Gaussian; Non-linear distribution; Reservoir modeling; Standard deviation; Statistical relationship; Stochastic simulations; Total porosity; Well log data; Work-flows; Acoustic impedance; Estimation; Gases; Hydration; Stochastic models; Stochastic systems; Three dimensional; Three dimensional computer graphics; Well logging; Gas hydrates; acoustics; Bayesian analysis; borehole; gas field; gas hydrate; pixel; stochasticity; well logging; Canada; Mackenzie Delta; Northwest Territories

Magnetotelluric Studies at the San Andreas Fault Zone: Implications for the Role of Fluids - Becken, M.; Ritter, O. (Surveys in Geophysics, 2012)
Fluids residing in interconnected porosity networks have a significant weakening effect on the rheology of rocks and can strongly influence deformation along fault zones. The magnetotelluric (MT) technique is sensitive to interconnected fluid networks and can image these zones on crustal and upper mantle scales. MT images have revealed several prominent electrical conductivity anomalies at the San Andreas Fault which have been attributed to the presence of saline fluids within such networks and which have been associated with tectonic processes. These models suggest that ongoing fluid release in the upper mantle and lower crust is closely related to the mechanical state of the crust. Where fluids are drained into the brittle crust, and where these fluids are kept at high pressures, fault creep is supported. Fluid fluxes from deeper levels, in combination with meteoric and crustal metamorphic fluid inflow, and in response to fault creep, leads to high-conductivity zones developing as fault zone conductors in the brittle portion of crust. In turn, the absence of crustal fluid pathways may be characteristic for mechanically locked segments of the fault. Here, MT models suggest that fluids are trapped at depth and kept at high pressures. We speculate that fluids may infiltrate neighboring rocks and in their wake induce non-volcanic tremor. © 2011 Springer Science+Business Media B.V.
cited By 67
Keywords: Creep; Fluids; Magnetotellurics; Strike-slip faults; Volcanic rocks; Electrical conductivity; High-conductivity zones; Interconnected porosity; Magnetotelluric studies; Metamorphic fluids; Non-volcanic tremors; San Andreas fault; Weakening effect; Structural geology; deformation mechanism; electrical conductivity; fault zone; high pressure; magnetotelluric method; porosity; rheology; San Andreas Fault; California; San Andreas; United States

New insights into paleoenvironmental changes in Laguna Potrok Aike, southern Patagonia, since the Late Pleistocene: The PASADO multiproxy record - Recasens, Cristina; Ariztegui, Daniel; Gebhardt, Catalina; Gogorza, Claudia; Haberzettl, Torsten; Hahn, Annette; Kliem, Pierre; Lis'e-Pronovost, Agathe; L{ucke, Andreas; Maidana, Nora; Mayr, Christoph; Ohlendorf, Christian; et al. (Holocene, 2012)
A series of long sediment cores was retrieved from Laguna Potrok Aike, Southern Patagonia, within the framework of PASADO (Potrok Aike Maar Lake Sediment Archive Drilling Project), an ICDP (International Continental Scientific Drilling Program) lake drilling project. This maar lake, located at 52°S, 70°W in the Province of Santa Cruz (Argentina), in the southernmost continental area of the world, is one of the few permanent lakes in the region, providing a unique continuous paleoclimatic and paleoecological lacustrine record for the last glacial cycle. Previous multiproxy studies of this site have characterized the environmental history of these dry lands in the Patagonian Steppe for the last 16 cal. ka BP. This new series of sediment cores provides a much longer record of climate variability in Southern Patagonia since 51.3 cal. ka BP. Using a multiproxy strategy, a set of samples (mostly from core catcher material) was analyzed for physical properties, rock magnetism, geochemistry, CNS elemental analysis, stable isotopes, pollen and diatoms. This preliminary multiproxy limnogeological interpretation sheds new light on the regional Pleistocene and Holocene environmental history, revealing lake-level variations through time and identifying time windows of interest where higher resolution analyses will be carried out. © The Author(s) 2011.
Keywords: Argentina; Laguna Potrok Aike; Patagonia; Santa Cruz [Argentina]; diatom; lacustrine deposit; paleoclimate; paleoecology; paleoenvironment; palynology; Pleistocene; proxy climate record; sediment core; stable isotope

Monitoring the West Bohemian earthquake swarm in 2008/2009 by a temporary small-aperture seismic array - Hiemer, Stefan; Roessler, Dirk; Scherbaum, Frank (Journal of Seismology, 2012)
The most recent intense earthquake swarm in West Bohemia lasted from 6 October 2008 to January 2009. Starting 12 days after the onset, the University of Potsdam monitored the swarm by a temporary small-aperture seismic array at 10 km epicentral distance. The purpose of the installation was a complete monitoring of the swarm including micro-earthquakes (M L < 0). We identify earthquakes using a conventional short-term average/long-term average trigger combined with sliding-window frequency-wavenumber and polarisation analyses. The resulting earthquake catalogue consists of 14,530 earthquakes between 19 October 2008 and 18 March 2009 with magnitudes in the range of - 1.2 ≤ M L ≤ 2. 7. The small-aperture seismic array substantially lowers the detection threshold to about M c = - 0.4, when compared to the regional networks operating in West Bohemia (M c > 0.0). In the course of this work, the main temporal features (frequency-magnitude distribution, propagation of back azimuth and horizontal slowness, occurrence rate of aftershock sequences and interevent-time distribution) of the recent 2008/2009 earthquake swarm are presented and discussed. Temporal changes of the coefficient of variation (based on interevent times) suggest that the swarm earthquake activity of the 2008/2009 swarm terminates by 12 January 2009. During the main phase in our studied swarm period after 19 October, the b value of the Gutenberg-Richter relation decreases from 1.2 to 0.8. This trend is also reflected in the power-law behavior of the seismic moment release. The corresponding total seismic moment release of 1.02×10 17 Nm is equivalent to M L,max = 5. 4. © 2011 Springer Science+Business Media B.V.
Keywords: Bohemia; Czech Republic; aftershock; earthquake catalogue; earthquake magnitude; earthquake swarm; frequency analysis; microearthquake; monitoring; polarization; seismic moment; temporal variation

Mollusc biodiversity in a European ancient lake system: Lakes Prespa and Mikri Prespa in the Balkans - Albrecht, Christian; Hauffe, Torsten; Schreiber, Kirstin; Wilke, Thomas (Hydrobiologia, 2012)
The spatial distribution of (endemic) biodiversity in ancient and potentially ancient lakes in Europe is poorly understood. Examples include Lakes Prespa and Mikri Prespa in the Central Balkans. Utilizing information of the most species-rich taxon in these lakes, the Mollusca, we therefore attempt to statistically assess and visualize the spatial distribution of biodiversity, to analyse biogeographical patterns, and to carry out a conservation assessment. We estimate that at least 40 (sub)species (29 gastropod and 11 bivalve taxa) occur in the lakes. For both lakes combined, 37. 5% of the mollusc taxa are endemic. In general, the mollusc richness in Lake Mikri Prespa is lower than in Lake Prespa and less heterogeneously distributed. The highest species richness can be seen on the western and south eastern shores of Lake Prespa. Based on the presence/absence of genera, a minimum spanning tree analysis supports the sister lake relationship of both lakes, which, in turn, are most closely related to lakes in the western Balkans and not to nearby Lake Ohrid. The IUCN red list assessment revealed (A) a tendency towards mollusc faunal change, (B) a contemporary decline and potential loss of mollusc diversity, and (C) that all endemic species are of conservation concern. © 2011 Springer Science+Business Media B.V.
Keywords: Lake Mikri Prespa; Bivalvia; Gastropoda; Mollusca; assessment method; biodiversity; biogeography; conservation management; endemic species; extinction; habitat conservation; heterogeneity; mollusc; population decline; Red List; spatial distribution; species conservation; species richness; taxonomy; visualization

Modeling evolution of the San Andreas Fault system in northern and central California - Popov, A.A.; Sobolev, S.V.; Zoback, M.D. (Geochemistry, Geophysics, Geosystems, 2012)
We present a three-dimensional finite element thermomechanical model idealizing the complex deformation processes associated with evolution of the San Andreas Fault system (SAFS) in northern and central California over the past 20 Myr. More specifically, we investigate the mechanisms responsible for the eastward (landward) migration of the San Andreas plate boundary over time, a process that has largely determined the evolution and present structure of SAFS. Two possible mechanisms had been previously suggested. One mechanism suggests that the Pacific plate first cools and captures uprising mantle in the slab window, subsequently causing accretion of the continental crustal blocks. An alternative scenario attributes accretion to the capture of plate fragments (microplates) stalled in the ceased Farallon-North America subduction zone. Here we test both these scenarios numerically using a recently developed lithospheric-scale code, SLIM3D, that employs free surface, nonlinear temperature- and stress-dependent elastoviscoplastic rheology and allows for self-generation of faults. Modeling suggests that microplate capture is the primary driving mechanism for the eastward migration of the plate boundary, while the slab window cooling mechanism alone is incapable of explaining this phenomenon. We also show that the system evolves to the present day structure of SAFS only if the coefficient of friction at mature faults is low (0.08 for the best fit model). Thus, our model provides an independent constraint supporting the weak fault in a strong crust hypothesis for SAFS. © 2012. American Geophysical Union. All Rights Reserved.
cited By 23
Keywords: Friction; Geodynamics; Plates (structural components); Strike-slip faults; Tectonics; Best-fit models; California; Coefficient of frictions; Complex deformation; Cooling mechanism; Crustal block; Driving mechanism; Elasto-viscoplastic; Free surfaces; Microplates; Nonlinear temperature; Numeric models; Pacific plates; Plate boundaries; San Andreas fault; Self-generation; Slab windows; Stress-dependent; Subduction zones; Thermomechanical model; Three dimensional finite elements; weak fault in strong crust; Three dimensional; deformation; finite element method; friction; geodynamics; numerical model; Pacific plate; plate boundary; San Andreas Fault; subduction zone; tectonic evolution; California; United States

Mineralogy of the otoliths of naked carp Gymnocypris przewalskii (Kessler) from Lake Qinghai and its Sr/Ca potential implications for migratory pattern - Zhou, Ling; Jin, Zhangdong; Li, Fuchun; Chen-Feng, You; Chia-Hui, Wang; Huilun, Miss Chen; Zhijie, Xu; Yoshiyuki, Iizuka; Fei, Zhang; Yu-an, Jin; Maoyong, He; Yuewei, Shi; et al. (Science China Earth Sciences, 2012)
Otoliths are biogenic carbonate minerals whose microstructure and microchemistry have been used for age determination, stock identification, life history and environmental tracing. Using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy, we have determined the mineral types and crystalline characteristics of three pairs of otoliths from naked carp Gymnocypris przewalskii, the predominant fish in Lake Qinghai. The results indicate that the mineral of both lapillus and sagitta of the naked carp is aragonite, and that of asteriscus is vaterite. The aragonite of lapillus has prefect crystallization. Given the shape of lapillus and the sensitivity of its aragonite to water chemistry, lapillus was used to analyze temporal Sr/Ca ratios along the maximal growth axis by an electron probe microanalyzer (EPMA). Consistent variations of Sr/Ca ratios with a range of 1. 0×10-3-5. 0×10combining triple dot above on the long and short radii indicate that Sr/Ca ratios of lapillus potentially respond to the chemical compositions of the host waters during the period of the naked carp's growth and migration. Discontinuous (dark) zones of lapillus were formed during fall and winter when the naked carp grows slowly in Lake Qinghai, resulting in similar low Sr/Ca ratios to lake water, whereas incremental zones with higher Sr/Ca ratios respond to its migratory river waters during spring and summer. Various Sr/Ca ratios of incremental zones suggest that the migratory pattern of the naked carp may be much more flexible, rather than in a single river. Therefore, high-resolution otolith microchemistry of the naked carp can be used to trace its migratory behavior, which is of significance for determining its migratory pattern and life history of this precious species inhabiting the Tibetan Plateau. © 2012 Science China Press and Springer-Verlag Berlin Heidelberg.
Keywords: China; Qinghai; Qinghai Lake; Qinghai-Xizang Plateau; Asteriscus; Cyprinidae; Gymnocypris przewalskii; Sagitta; Carbonate minerals; Chemical analysis; Fourier transform infrared spectroscopy; Minerals; X ray diffraction; aragonite; Environmental tracers; Lake Qinghai naked carps; migration; otolith; Sr/ca ratios; aragonite; biogenic mineral; calcium; chemical composition; crystallization; cyprinid; mineralogy; otolith; strontium; tracer; Lakes

Mineral-templated growth of natural graphite films - Zuilen, Mark A; Fliegel, Daniel; Lepland, Aivo; Qu, Yuangao; Schreiber, Anja; Romashkin, Alexander E; Philippot, Pascal (Geochimica et Cosmochimica Acta, 2012)

Methanotrophy in a P aleoproterozoic oil field ecosystem, Z aonega F ormation, K arelia, R ussia - Qu, Yu; Črne, AE; Lepland, A; Van Zuilen, MA (Geobiology, 2012)

Major ion geochemistry of shallow groundwater in the Qinghai Lake catchment, NE Qinghai-Tibet Plateau - Xiao, Jun; Jin, Zhangdong; Zhang, Fei; Wang, Jin (Environmental Earth Sciences, 2012)
Conventional hydrochemical techniques and statistical analyses were applied to better understand the solute geochemistry and the hydrochemical process of shallow groundwater in the Qinghai Lake catchment. Shallow groundwater in the Qinghai Lake catchment is slightly alkaline, and is characterized by a high ion concentrations and low water temperature. The total dissolved solids (TDS) in most of the samples are <1,000 mg/L, i. e. fresh water and depend mainly on the concentration of SO 4 2-, Cl - and Na +. Groundwater table is influenced directly by the residents' groundwater consumption. Most of the groundwaters in the Qinghai Lake catchment belong to the Ca 2+(Na +) -HCO 3 - type, while the Qinghai Lake, part of the Buha (BHR) and the Lake Side (LS) samples belong to the Na +-Cl - type. The groundwater is oversaturated with respect to aragonite, calcite and dolomite, but not to magnesite and gypsum. Solutes are mainly derived from strong evaporite dissolution in Daotang, BHR and LS samples and from strong carbonate weathering in Hargai and Shaliu samples. Carbonate weathering is stronger than evaporite dissolution with weak silicate weathering in the Qinghai Lake catchment. Carbonate weathering, ion exchange reaction and precipitation are the major hydrogeochemical processes responsible for the solutes in the groundwater in the Qinghai Lake catchment. Most of the shallow groundwaters are suitable for drinking. More attention should be paid to the potential pollution of nitrate, chloride and sulfide in shallow groundwater in the future. © 2012 Springer-Verlag.
Keywords: China; Qinghai; Qinghai Lake; Carbonate minerals; Carbonation; Catchments; Chlorine compounds; Dissolution; Groundwater; Groundwater pollution; Gypsum; Hydrochemistry; Lakes; Runoff; Weathering; Carbonate weathering; Evaporite dissolution; Fresh Water; Ground water table; Groundwater consumption; Hydrochemical process; Hydrochemicals; Hydrogeochemical process; Ion concentrations; Ion exchange reactions; Low water; Qinghai Lake; Qinghai Tibet plateau; Shallow groundwater; Silicate weathering; Total dissolved solids; hydrogeochemistry; ion exchange; sampling; shallow water; solute; water table; water temperature; Groundwater geochemistry

Major environmental change and bonebed genesis prior to the triassic-jurassic mass extinction - Suan, Guillaume; F{ollmi, Karl B.; Adatte, Thierry; Bomou, Brahimsamba; Spangenberg, Jorge E.; Schootbrugge, Bas (Journal of the Geological Society, 2012)
We present new geochemical and sedimentological data from marginal marine strata of Penarth Bay, south Wales (UK) to elucidate the origin of widespread but enigmatic concentrations of vertebrate hard parts (bonebeds) in marine successions of Rhaetian age (late Triassic). Sedimentological evidence shows that the phosphatic constituents of the bonebeds were subjected to intense phosphatization in shallow current dominated settings and subsequently reworked and transported basinward by storms. Inter bedded organic-rich strata deposited under quiescent and poorly oxygenated conditions record enhanced phosphorus regeneration from sedimentary organic matter into the water column and probably provided the main source of phosphate required for heavy bonebed clast phosphatization. The stratigraphically limited interval showing evidence for oxygen depletion and accelerated P-cycling coincides with a negative 4‰ organic carbon isotope excursion, which possibly reflects supra-regional changes in carbon cycling and clearly predates the 'initial isotope excursion' characterizing many Triassic-Jurassic boundary strata. our data indicate that Rhaetian bonebeds are the lithological signature of profound, climatically driven changes in carbon cycling and redox conditions and support the idea of a multi-pulsed environmental crisis at the end of the Triassic, possibly linked to successive episodes of igneous activity in the central Atlantic Magmatic Province.
Keywords: South Wales; United Kingdom; Wales; Vertebrata; Barium alloys; Isotopes; Lithology; Carbon isotope excursions; Central atlantic magmatic provinces; Environmental change; Environmental crisis; Sedimentary organic matter; Sedimentological data; Sedimentological evidence; Triassic-Jurassic boundary; carbon cycle; environmental change; geochemistry; Jurassic; mass extinction; organic matter; paleoenvironment; petrogenesis; phosphate; phosphatization; redox conditions; Rhaetian; sedimentology; stratigraphic boundary; stratigraphy; vertebrate; water column; Organic carbon

Lithosphere structure of the NE Bohemian Massif (Sudetes) - A teleseismic receiver function study - Geissler, Wolfram H.; K{ampf, Horst; Sk'acelov'a, Zuzana; Plomerova, Jaroslava; Babuška, Vladislav; Kind, Rainer (Tectonophysics, 2012)
In 2004 and 2005 a passive seismic experiment was carried out in the northern and northeastern part of the Bohemian Massif (Sudetes) to study the lithospheric structure. We present results from Ps and Sp receiver function analyses. With one exception, Moho depth at stations in the northwestern part of the study area varies between 28 and 32km. Thicker crust up to 35km was mapped toward the south (Moldanubian unit) and toward the east (Moravo-Silesian and Brunovistulian units) confirming results from previous active seismic measurements. There exists a relatively sharp step in Moho depth between units of the central Sudetes ( 30km) and the Moravo-Silesian unit ( 35km). The v p/v s ratios inverted from primary and multiple Moho Ps conversions hint for different crustal compositions of the units. Toward the Carpathian thrust we have no clear indications for any crustal root or slab beneath the western Carpathians. However, our data suggests a deepening of the Moho or at least a complicated crust-mantle transition in this area. Additional Ps phases were observed between 6 and 10s delay time in the Sudetes. These phases cannot be explained by Moho reverberations, but are most probably caused by low velocity zones in the middle crust or lithospheric mantle as shown by modeling of theoretical receiver functions. The stations showing these abnormal phases are located in the area of Permo-Carboniferous basins on probably Tepl'a-Barrandian crust. Therefore we assume that the phases hint at a mid-crustal low velocity zone between 16 and 20km depth, which is interpreted as a felsic solidified magma reservoir of the Permo-Carboniferous volcanism beneath the Sudetic Basins. Sp receiver functions show phases with negative polarity at 9 to 12s lead time on average, which we interpret as lithosphere-asthenosphere boundary at about 80 to 110km depth. © 2012 Elsevier B.V.
Keywords: Bohemian Massif; Sudetes; Seismology; Central Europe; ratio; Lithosphere-asthenosphere boundary; Lithospheric structure; Moho discontinuity; Permo-Carboniferous volcanism; asthenosphere; Carboniferous; crust-mantle boundary; crustal structure; lithospheric structure; magma chamber; Moho; observational method; Permian; S-wave; seismic tomography; seismic velocity; velocity structure; volcanism; Structural geology

Late Quaternary sedimentological and climate changes at Lake Bosumtwi Ghana: New constraints from laminae analysis and radiocarbon age modeling - Shanahan, Timothy M.; Beck, J. Warren; Overpeck, Jonathan T.; McKay, Nicholas P.; Pigati, Jeffrey S.; Peck, John A.; Scholz, Christopher A.; Heil, Clifford W.; King, John (Palaeogeography, Palaeoclimatology, Palaeoecology, 2012)
The Lake Bosumtwi sediment record represents one of the longest and highest-resolution terrestrial records of paleoclimate change available from sub-Saharan Africa. Here we report a new sediment age model framework for the last . 45. cal kyr of sedimentation using a combination of high-resolution radiocarbon dating, Bayesian age-depth modeling and lamination counting. Our results highlight the practical limits of these methods for reducing age model uncertainties and suggest that even with very high sampling densities, radiocarbon uncertainties of at least a few hundred years are unavoidable. Age model uncertainties are smallest during the Holocene (205. yr) and the glacial (360. yr) but are large at the base of the record (1660. yr), due to a combination of decreasing sample density, larger calibration uncertainties and increases in radiocarbon age scatter. For portions of the chronology older than . 35. cal kyr, additional considerations, such as the use of a low-blank graphitization system and more rigorous sample pretreatment were necessary to generate a reliable age depth model because of the incorporation of small amounts of younger carbon. A comparison of radiocarbon age model results and lamination counts over the time interval . 15-30. cal kyr agree with an overall discrepancy of . 10% and display similar changes in sedimentation rate, supporting the annual nature of sediment laminations in the early part of the record. Changes in sedimentation rates reconstructed from the age-depth model indicate that intervals of enhanced sediment delivery occurred at 16-19, 24 and 29-31. cal kyr, broadly synchronous with reconstructed drought episodes elsewhere in northern West Africa and potentially, with changes in Atlantic meridional heat transport during North Atlantic Heinrich events. These data suggest that millennial-scale drought events in the West African monsoon region were latitudinally extensive, reaching within several hundred kilometers of the Guinea coast. This is inconsistent with a simple southward shift in the mean position of the monsoon rainbelt, and requires changes in moisture convergence as a result of either a reduction in the moisture content of the tropical rainbelt, decreased convection, or both. © 2012 Elsevier B.V.
Keywords: Ashanti; Ghana; Lake Bosumtwi; Sub-Saharan Africa; calibration; climate change; core analysis; drought; glacial-interglacial cycle; graphitization; heat transfer; Heinrich event; Holocene; laminar flow; moisture content; paleoclimate; radiocarbon dating; sedimentation rate; uncertainty analysis

Late Pleistocene and Holocene contourite drift in Lake Prespa (Albania/F.Y.R. of Macedonia/Greece) - Wagner, Bernd; Aufgebauer, Anne; Vogel, Hendrik; Zanchetta, Giovanni; Sulpizio, Roberto; Damaschke, Magret (Quaternary International, 2012)
Hydro-acoustic surveys and coring campaigns at Lake Prespa were carried out between 2007 and 2009. This paper presents hydro-acoustic profiles and provide lithological and chronostratigraphical information from three up to 15.75 m long sediment sequences from the Macedonian side of the lake. The sediment sequences comprise glacial and interglacial sediments likely deposited from the end of Marine Isotope Stage (MIS) 5 to present day. The information implies a distinct change of sedimentation patterns at the Pleistocene/Holocene transition and the establishment of a relatively strong Holocene current system and deposition of channel-related contourite drift in Lake Prespa. Potential causes for the establishment of this current during the Holocene include significant lake level change, reduced winter ice cover, and/or higher aeolian activity. © 2012 Elsevier Ltd and INQUA.
Keywords: Lake Mikri Prespa; chronostratigraphy; contourite; drift behavior; glacial deposit; Holocene; ice cover; interglacial; lake level; lithology; marine isotope stage; Pleistocene; sediment core; sedimentary sequence; sedimentation

Reconstructing Holocene environmental change in Lake Ohrid (Macedonia/Albania) using diatom as proxies - Cvetkoska, Aleksandra; Levkov, Zlatko; Reed, Jane (Macedonian Journal of Ecology and Environment, 2012)

Reading the Archive of Earth’s Oxygenation: Volume 3: Global Events and the Fennoscandian Arctic Russia-Drilling Early Earth Project - Melezhik, Victor; Prave, Anthony R; Hanski, Eero J; Fallick, Anthony E; Lepland, Aivo; Kump, Lee R; Strauss, Harald (Springer Science & Business Media, 2012)

Tsunami backwash deposits with Chicxulub impact ejecta and dinosaur remains from the Cretaceous-Palaeogene boundary in the La Popa Basin, Mexico - Schulte, P.; Smit, J.; Deutsch, A.; Salge, T.; Friese, A.; Beichel, K. (Sedimentology, 2012)
The La Popa Basin in north-eastern Mexico features outstanding, continuous three-dimensional exposures of the Cretaceous-Palaeogene boundary event deposit in shallow shelf environments pierced by salt stocks. In the area to the south-east of the El Papalote diapir, the Cretaceous-Palaeogene deposit consists of two superimposed sedimentary units and erosively overlies upper Maastrichtian sand-siltstones with soft-sediment deformation and liquefaction structures. The basal unit 1 is an up to 8m thick chaotic, carbonate-rich bed that discontinuously fills incised gutters and channels. Besides abundant silicic and carbonate ejecta spherules from the Chicxulub impact, unit 1 includes large sandstone boulders and abundant shallow-water debris (for example, mud clasts, algae, bivalve shells, gastropod shells and vertebrate remains). Unit 1 is conformably overlain by unit 2. Distal to the diapir, unit 2 consists of a centimetre to decimetre-thick conglomeratic, coarse bioclast and spherule-bearing sandstone bed. Closer to the diapir, unit 2 becomes a metre-thick series of four to eight conglomeratic to fine-grained graded sandstone beds rich in shell debris and ejecta spherules. Unit 2 is conformably overlain by structureless to parallel laminated sandstone beds that may mark the return to the pre-event depositional regime. The sedimentary characteristics of the Cretaceous-Palaeogene deposit, including its erosive base, its sheet-like geometry, the presence of multiple, graded beds, evidence for upper flow regime conditions and the absence of bioturbation, support an origin by a short-term multiphase depositional event. The occurrence of soft-sediment deformation structures (for example, liquefaction) below the Cretaceous-Palaeogene deposit suggests that earthquakes were the first to occur at La Popa. Then, shelf collapse and strong backflow from the first tsunami waves may have triggered erosion and deposition by violent ejecta-rich hyperconcentrated density flows (unit 1). Subsequently, a series of concentrated density flows resulting from tsunami backwash surges may have deposited the multiple-graded bedding structures of unit 2. The specific depositional sequence and the Fe-Mg-rich as well as Si-K-rich composition of the ejecta spherules both provide a critical link to the well-known deep marine Cretaceous-Palaeogene boundary sites in the adjacent Burgos basin in north-eastern Mexico. Moreover, the pulse-like input of Chicxulub ejecta material at the base of the event deposit allows for correlation with other Cretaceous-Palaeogene boundary sites in the Gulf of Mexico and the Atlantic, as well as in Central and Northern America. The presence of diverse dinosaur and mosasur bones and teeth in the event deposit is the first observation of such remains together with Chicxulub ejecta material. These findings indicate that dinosaurs lived in the area during the latest Maastrichtian and suggest that the tsunami waves not only eroded deltas and estuaries but the coastal plain as well. © 2011 The Authors. Journal compilation © 2011 International Association of Sedimentologists.
cited By 29

Revisiting elastic anisotropy of biotite gneiss from the Outokumpu scientific drill hole based on new texture measurements and texture-based velocity calculations - Wenk, H.-R.; Vasin, R.N.; Kern, H.; Matthies, S.; Vogel, S.C.; Ivankina, T.I. (Tectonophysics, 2012)
A sample of biotite gneiss from the Outokumpu deep drilling project in Finland was investigated by Kern et al. (2008) for crystal preferred orientation and elastic anisotropy. Considerable differences between measured acoustic velocities and velocities calculated on the basis of texture patterns were observed. Measured P-wave anisotropy was 15.1% versus a Voigt average yielding 7.9%. Here we investigate the same sample with different methods and using different averaging techniques. Analyzing time-of-flight neutron diffraction data from Dubna-SKAT and LANSCE-HIPPO diffractometers with the Rietveld technique, much stronger preferred orientation for biotite is determined, compared to conventional pole-figure analysis reported previously. The comparison reveals important differences: HIPPO has much better counting statistics but pole figure coverage is poor. SKAT has better angular resolution. Using the new preferred orientation data and applying a self-consistent averaging method that takes grain shapes into account, close agreement of calculated and measured P-wave velocities is observed (12.6%). This is further improved by adding 0.1. vol.% flat micropores parallel to the biotite platelets in the simulation (14.9%). © 2012.
Keywords: Finland; Outokumpu; Pohjois-Karjala; Acoustic wave velocity measurement; Anisotropy; Neutron diffraction; Poles; Seismic waves; Textures; Angular resolution; Averaging method; Averaging technique; Biotite gneiss; Counting statistics; Crystal preferred orientations; Deep drilling; Drill hole; Elastic anisotropy; Finland; Gneiss; Grain shapes; Micropores; Neutron diffraction data; P-wave velocity; Pole figure; Pole figure analysis; Preferred orientations; Rietveld technique; Self-consistent averaging; Texture measurement; Texture patterns; Time of flight; Velocity calculations; biotite; crystal property; elastic property; gneiss; measurement method; neutron diffraction; P-wave; preferred orientation; seismic anisotropy; seismic velocity; texture; Mica

The effects of direct current and alternating current on the magnetization rate of shale (in Chinese); 直流场和交变场对泥岩磁化率的影响 - Li, H.; Zhang, S.; Zhao, K.; Wu, H.; Yang, T. (Quaternary Sciences, 2012)

Late Cretaceous biostratigraphy and paleoenvironmental reconstruction based on non-marine ostracodes from well SK1 (south), Songliao Basin, northeast China - Xi, D.; Li, S.; Wan, X.; Jing, X.; Huang, Q.; Colin, J.-P.; Wang, Z.; Si, W. (Hydrobiologia, 2012)
High-resolution biostratigraphy has been established on the basis of fossil ostracodes from cores of the Cretaceous Continental Scientific Drilling borehole-Songke 1 (south) (SK1(s)) in the Songliao Basin, northeast China. More than 80 species belonging to 13 genera have been identified and 15 ostracode assemblage zones have been recognized. On the basis of ostracode paleoecological analysis, paleoenvironments, for example lake levels and salinity, have been reconstructed. Two inferred deep-water phases occurred during the deposition of the lower Qingshankou and lower Nenjiang formations, whereas shallower water phases probably occurred during deposition of the upper Quantou and uppermost Qingshankou to Yaojia formations. The salinity of paleo-Songliao lake is interpreted as predominantly freshwater to oligohaline. Oligohaline to mesohaline water environments may have occurred during the first and middle third members of the Qingshankou formation and the lower first and lower second members of the Nenjiang formation. © 2011 Springer Science+Business Media B.V.
cited By 32
Keywords: biostratigraphy; Cretaceous; deep water; fossil record; ostracod; paleoecology; paleoenvironment; reconstruction; salinity; China; Songliao Basin; Ostracoda

Workshop on drilling of Lake Junin, Peru: Potential for development of a continuous tropical climate record - Rodbell, D.T.; Abbott, M.B. (Scientific Drilling, 2012)
cited By 4

Velocity dispersion of stoneley wave as an insight into permeability - Sun, L.F.; Pun, W.; Milkereit, B. (74th European Association of Geoscientists and Engineers Conference and Exhibition 2012 Incorporating SPE EUROPEC 2012: Responsibly Securing Natural Resources, 2012)
Permeability is a key parameter in hydrocarbon exploration and reservoir analysis. Studies indicate that a higher permeability in a porous rock results in greater P-wave velocity dispersion. We utilize fullwaveform sonic data to study the relation of permeability and velocity dispersion of Stoneley waves. The sonic datasets were acquired from the Mallik gashydrate research wells in Mackenzie Delta, Northwest Territory, Canada. Velocities of Stoneley wave are measured using semblance analysis on low and high pass components, and the velocity difference is therefore velocity dispersion. Well logs from the same borehole are then investigated to produce cross plots of velocity dispersion, permeability, and porosity. The measurements show positive correlation between velocity dispersion and permeability. It is very common that Stoneley wave is much stronger and easier to identify than P or S wave in borehole sonic surveys. Our effort demonstrates that velocity dispersion of Stoneley wave is a potential indicator of in situ permeability.
cited By 0
Keywords: Petroleum reservoir engineering; Petroleum reservoir evaluation; Seismic waves; Shear waves; Velocity; Wave propagation; Well logging; Hydrocarbon exploration; P-wave velocity; Positive correlations; Potential indicators; Reservoir analysis; Semblance analysis; Velocity difference; Velocity dispersion; Dispersion (waves)

Vegetation history of central Chukotka deduced from permafrost paleoenvironmental records of the El'gygytgyn Impact Crater - Andreev, A. A.; Morozova, E.; Fedorov, G.; Schirrmeister, L.; Bobrov, A. A.; Kienast, F.; Schwamborn, G. (Climate of the Past, 2012)
Frozen sediments from three cores bored in the permafrost surrounding the El'gygytgyn Impact Crater Lake have been studied for pollen, non-pollen palynomorphs, plant macrofossils and rhizopods. The palynological study of these cores contributes to a higher resolution of time intervals presented in a poor temporal resolution in the lacustrine sediments; namely the Allerød and succeeding periods. Moreover, the permafrost records better reflect local environmental changes, allowing a more reliable reconstruction of the local paleoenvironments. The new data confirm that shrub tundra with dwarf birch, shrub alder and willow dominated the lake surroundings during the Allerød warming. Younger Dryas pollen assemblages reflect abrupt changes to grass-sedge-herb dominated environments reflecting significantly drier and cooler climate. Low shrub tundra with dwarf birch and willow dominate the lake vicinity at the onset of the Holocene. The find of larch seeds indicate its local presence around 11 000 cal yr BP and, thus a northward shift of treeline by about 100 km during the early Holocene thermal optimum. Forest tundra with larch and shrub alder stands grew in the area during the early Holocene. After ca. 3500 cal yr BP similar-to-modern plant communities became common in the lake vicinity. © 2009 Author(s).
cited By 35
Keywords: climate change; environmental change; Hypsithermal; paleoenvironment; permafrost; sediment core; temporal record; treeline; vegetation history; Chukchi; Elgygytgyn Lake; Russian Federation

U-Pb, trace element and Lu-Hf properties of unique dissolution-reprecipitation zircon from UHP eclogite in SW Sulu terrane, eastern China - Liu, Fulai; Gerdes, Axel; Liu, Pinghua (Gondwana Research, 2012)
A unique dissolution-reprecipitation zircon has been identified for the first time in a Qtz- and Phe-bearing eclogite from the drill hole CCSD-MH, southwestern Sulu UHP terrane by using laser Raman and cathodoluminescence (CL) imaging combined with trace-element analyses and U-Pb and Lu-Hf isotope data. Relic inherited domains of partially dissolved zircon show magmatic features and preserve mineral inclusions of Cpx+Pl+Qtz+Ap. Whereas newly formed zircons crystallized around or along cracks of the inherited (magmatic) domains and contain mineral inclusions of Coe+Grt+Omp+Phe+Ap typical for UHP metamorphism. In addition, primary fluid inclusions were identified in the coesite-bearing zircon domains, characterized by a single H 2O-phase or CO 2-H 2O-phase, indicating the presence of fluids during UHP conditions. Strongly dissolved inherited (magmatic) zircons yielded SHRIMP 206Pb/ 238U ages of 782-588Ma with an upper intercept age of 780±14Ma. New recrystallized or metamorphic zircons yielded consistent Triassic UHP ages around 238-225Ma with a weighted mean of 229.2±2.3Ma. Zircon trace element and Hf isotope compositions and mineral inclusions classify the protolith of the Sulu eclogite as an intermediate to mafic Neoproterozoic igneous rock, which was subducted to mantle depth and experienced UHP metamorphism in Middle Triassic times. The juvenile εHf (780Ma) value of+7.4±2.9 in inherited (magmatic) zircon points to a significant input from the depleted mantle to the Dabie-Sulu UHP terrane during Middle Neoproterozoic. New UHP zircon domains have low Lu/Hf, Th/U and significantly higher 176Hf/ 177Hf ratios than the inherited (magmatic) zircons, consistent with formation during recrystallization and fractionation of the Lu-Hf system during UHP metamorphism. © 2011 International Association for Gondwana Research.

Toward age determination of the termination of the Cretaceous Normal Superchron - He, H.; Deng, C.; Wang, P.; Pan, Y.; Zhu, R. (Geochemistry, Geophysics, Geosystems, 2012)
We present an integrated chronology for the terrestrial Upper Cretaceous in East Asia based on high-resolution magnetostratigraphic results and detailed SIMS U-Pb zircon analyses of a continuous continental sedimentary sequence drilled from the Songliao Basin in northeast China. Correlation to the geomagnetic polarity timescale was achieved by combining magnetostratigraphic and SIMS U-Pb zircon geochronologic data, which suggest that the south core of the CCSD-SK-I sedimentary sequence spans from upper chron C34n to lower chron C33r. The age of the termination of the Cretaceous Normal Superchron (CNS) was estimated to be ∼83.4 Ma. Intervals of reverse geomagnetic field polarity of early Santonian age could be present during the late CNS. Two black shale layers at the base of Member 1 of the Qingshankou Formation and Member 2 of the Nenjiang Formation, which were previously interpreted as the products of lake anoxic events LAE1 and LAE2, have been well dated at 91.4 Ma and 83.7 Ma, respectively, by SIMS U-Pb zircon analyses of intercalated bentonite layers. However, the LAE1 and LAE2 identified here are not temporally correlated to the known oceanic anoxic events. Copyright 2012 by the American Geophysical Union.
cited By 87
Keywords: Anoxic sediments; Geomagnetism; Lead; Sedimentology; Age determination; Anoxic events; Black shales; Cretaceous Normal Superchron; East Asia; Geomagnetic fields; Geomagnetic polarity; High resolution; Magnetostratigraphy; Northeast China; Oceanic Anoxic Event; Sedimentary sequence; Songliao basin; Time-scales; U-Pb zircon; Upper Cretaceous; Geochronology; anoxic conditions; bentonite; black shale; Cretaceous; geochronology; geomagnetic field; magnetostratigraphy; sedimentary sequence; uranium-lead dating; China; Songliao Basin

Tomographic V p and V s structure of the California Central Coast Ranges, in the vicinity of SAFOD, from controlled-source seismic data - Ryberg, T.; Hole, J.A.; Fuis, G.S.; Rymer, M.J.; Bleibinhaus, F.; Stromeyer, D.; Bauer, K. (Geophysical Journal International, 2012)
A seismic reflection/refraction survey across the San Andreas fault near Parkfield, California, has refined our knowledge of the upper crustal structure of the central California Coast Ranges at the San Andreas Fault Observatory at Depth (SAFOD). The survey consisted of a 46-km-long line of seismographs (25-50 m spacing) and 63 explosions (25-200 kg; nominal spacing of 500 m, with some gaps). The traveltimes of refracted P and S waves from the explosions constitute independent data sets of relatively high quality that were inverted to produce P- and S-wave velocity models (V p, V s) along the profile, extending to as much as 5 km depth. The V p and V s models show a prominent lateral drop in velocities a few hundred metres northeast of SAFOD, between the drill hole and the San Andreas fault. The V p model shows particularly well a southwest-dipping velocity inversion beneath SAFOD, the top of which correlates with a fault penetrated by the drill hole that separates granitic rocks above from sedimentary rocks below. In addition to V p and V s models, a V p/V s model was derived. A V p/V s ratio lower than 1.73 is seen only at depth, in a narrow zone beginning at the target earthquakes for SAFOD and extending downward and northeastward into the North America Plate. Clusters in the parameter space spanned by V p/V s ratios and V p can be identified by two different methods, one more intuitive analytical method and one more abstract method based on neural network techniques. These clusters are correlated to different rock types, based on laboratory and in situ data. These clusters are remapped back into x-z plane along the profile. Prominent features mapped this way include Salinian granitic rocks beneath and west of SAFOD, and a body of sedimentary rocks faulted beneath these granitic rocks along what we and others interpret to be a branch of the Buzzard Canyon Fault (BCF) system. These sedimentary rocks extend from this fault to the San Andreas fault system. Unfortunately, our cluster analysis shows no significant discontinuity at the San Andreas fault, owing presumably to the fact that the San Andreas fault is located within sedimentary rocks having similar elastic properties. This paper is an attempt to 'downward' continue a geological map by geophysical means based on elastic properties of rock samples from the region. © 2012 The Authors Geophysical Journal International © 2012 RAS.
cited By 13
Keywords: Body waves; Continental margin; Controlled source; North America; Seismic tomography; Cluster analysis; Elasticity; Granite; Rock drills; Sedimentary rocks; Seismographs; Seismology; Shear waves; Strike-slip faults; Surveys; Transform faults; Structural geology; body wave; cluster analysis; continental margin; P-wave; S-wave; San Andreas Fault; seismic data; seismic reflection; seismic refraction; seismic source; seismic survey; seismic tomography; seismic velocity; seismograph; seismology; transform fault; upper crust; California; Coast Ranges; San Andreas; United States

The Towuti drilling project: Paleoenvironments, biological evolution, and geomicrobiology of a tropical pacific lake - Russell, James; Bijaksana, Satria (Scientific Drilling, 2012)
The Towuti Drilling Project (TDP) is an international research program, whose goal is to understand long-term environmental and climatic change in the tropical western Pacific, the impacts of geological and environmental changes on the biological evolution of aquatic taxa, and the geomicrobiology and biogeochemistry of metal-rich, ultramafic-hosted lake sediments through the scientific drilling of Lake Towuti, southern Sulawesi, Indonesia. Lake Towuti is a large tectonic lake at the downstream end of the Malili lake system, a chain of five highly biodiverse lakes that are among the oldest lakes in Southeast Asia. In 2015 we carried out a scientific drilling program on Lake Towuti using the International Continental Scientific Drilling Program (ICDP) Deep Lakes Drilling System (DLDS). We recovered a total of 1018m of core from 11 drilling sites with water depths ranging from 156 to 200 m. Recovery averaged 91.7 %, and the maximum drilling depth was 175m below the lake floor, penetrating the entire sedimentary infill of the basin. Initial data from core and borehole logging indicate that these cores record the evolution of a highly dynamic tectonic and limnological system, with clear indications of orbital-scale climate variability during the mid- to late Pleistocene. © Author(s) 2016.
Keywords: Biology; Climate change; Drilling; Microbiology; Tectonics; Biological evolution; Climate variability; Continental scientific drillings; Environmental change; International researches; Limnological system; Scientific drilling; Tropical Western Pacific; Lakes

The space and time complexity of chaotic mixing of silicate melts: Implications for igneous petrology - Perugini, D.; De Campos, C.P.; Ertel-Ingrisch, W.; Dingwell, D.B. (Lithos, 2012)
We present new experimental results on the study of the space and time modulation of compositional fields during chaotic mixing between mafic and felsic silicate melts. The experimental strategy was planned using numerical simulations performed using the experimental geometry. These mixing experiments were performed using a recently developed experimental apparatus, which is capable of mixing high-viscosity silicate melts at high temperatures and under precisely controlled conditions of fluid-dynamics and strain. The compositional variability produced by the mixing process was investigated both along linear analytical transects and on high-resolution 2D X-ray maps, covering the mixing patterns.Our results indicate that chaotic flow fields represent very powerful dynamics to blend silicate melts, even under laminar fluid dynamic conditions (Reynolds number ca. 10-7) and for dissimilar melts with high viscosity ratios (on the order of 103). The repetition of stretching and folding processes between the two melts induced a strong increase of contact interfaces thus favoring efficient chemical exchanges. As a result the initial mafic composition is no longer detectable in the mixing system after ca. 2h (i.e. the duration of the experiment). A further important result is the observation of highly non-linear patterns in inter-elemental plots produced by the onset of diffusive fractionation processes. This is contrary to common thinking that magma mixing should always produce linear trends between pairs of chemical elements.A new measure, the concentration variance, is proposed to quantify chemical element mobility during the mixing process. This measure is statistically robust and can be quantitatively used to measure chemical element mobility independently of the geometry in which the compositional variation (i.e. transects, areas, etc.) is embedded or the local strain history of the mingling.Our results highlight concentration variance as a robust probe of the as yet poorly-understood processes involved in the common petrological process of magma mixing. © 2012 Elsevier B.V.
cited By 34
Keywords: computer simulation; experimental study; felsic rock; fluid dynamics; fractionation; high temperature; igneous intrusion; laminar flow; mafic rock; mixing; petrology; Reynolds number; silicate melt

The role of barriers and gradients in differentiation processes of pyrgulinid microgastropods of Lake Ohrid - Schreiber, Kirstin; Hauffe, Torsten; Albrecht, Christian; Wilke, Thomas (Hydrobiologia, 2012)
Ancient Lake Ohrid is characterized by vertical (bathymetrical) zones within the lake, presumably promoting allopatric speciation due to barriers or parapatric speciation along gradients. Examples within the lake include the belt of Chara algae as well as the shell zone, both presumably impeding migrations of benthic invertebrates. Three potential cases of vertical differentiation leading to distinct depth forms have been reported for the gastropod subfamily Pyrgulinae (Caenogastropoda: Hydrobiidae): Ginaia munda ssp., Macedopyrgula spp. and Ochridopyrgulamacedonica ssp. Based on DNA data of the COI gene from a total of 145 specimens, this article aims at investigating the vertical differentiation within these depth forms and thus patterns of speciation in Lake Ohrid. An initial morphometric analysis showed a clear correlation of shell shape and collecting depth for Ginaia munda ssp. and Macedopyrgula spp. This morphological trend is largely reflected in the genetic structure of the respective taxa. The data presented here indicate the existence of strong gradients of abiotic and biotic factors in Lake Ohrid rather than distinct barriers. Therefore, parapatric speciation may be the predominant form of differentiation of benthic invertebrates in the lake. Incomplete lineage sorting, hybridization and phenotypic plasticity possibly caused by epigenetic mechanisms are discussed as possible reasons for the incongruence between geno- and phenotype observed in few specimens of Ginaia munda ssp. and Macedopyrgula spp. For the third taxon, Ochridopyrgulamacedonica ssp., morphometric and genetic analyses revealed only weak support for the previously proposed depth forms. However, a horizontal differentiation of lake and spring populations was revealed instead, and parapatric and allopatric differentiations are discussed in this taxon. © 2011 Springer Science+Business Media B.V.
Keywords: Lake Ohrid; algae; Caenogastropoda; Chara; Gastropoda; Hydrobiidae; Invertebrata; Lonchocarpus glaucifolius; alga; allopatry; barrier (equipment); bathymetric survey; benthos; gastropod; genetic analysis; genetic structure; morphometry; parapatry; phenotypic plasticity; phylogeography; speciation (biology)

The ICDP Snake River Geothermal Drilling Project: Preliminary overview of borehole geophysics - Liberty, L.M.; Kessler, J.E.; Kofman, R.; Bishop, R.; Shervais, J.W.; Evans, J.P.; Champion, D.E. (Transactions - Geothermal Resources Council, 2012)
Hotspot: The Snake River Geothermal Drilling Project was undertaken to better understand the geothermal systems in three locations across the Snake River Plain with varying geological and hydrological structure. An extensive series of standard and specialized geophysical logs were obtained in each of the wells. Hydrogen-index neutron and γ-γ density logs employing active sources were deployed through the drill string, and although not fully calibrated for such a situation do provide semi-quantitative information related to the 'stratigraphy' of the basalt flows and on the existence of alteration minerals. Electrical resistivity logs highlight the existence of some fracture and mineralized zones. Magnetic susceptibility together with the vector magnetic field measurements display substantial variations that, in combination with laboratory measurements, may provide a tool for tracking magnetic field reversals along the borehole. Full waveform sonic logs highlight the variations in compressional and shear velocity along the borehole. These, together with the high resolution borehole seismic measurements display changes with depth that are not yet understood. The borehole seismic measurements indicate that seismic arrivals are obtained at depth in the formations and that strong seismic reflections are produced at lithological contacts seen in the corresponding core logging. Finally, oriented ultrasonic borehole televiewer images were obtained over most of the wells and these correlate well with the nearly 6 km of core obtained. This good image log to core correlations, particularly with regards to drilling induced breakouts and tensile borehole and core fractures will allow for confident estimates of stress directions and or placing constraints on stress magnitudes. Such correlations will be used to orient in core orientation giving information useful in hydrological assessments, paleomagnetic dating, and structural volcanology.
cited By 7
Keywords: Electrical resistivity; Geophysical logging; Hydrological assessment; Laboratory measurements; Magnetic field reversal; Snake river plains; Substantial variations; Vertical seismic profiles; Electric conductivity; Electric logging; Fracture; Geothermal fields; Geothermal wells; Landforms; Lithology; Magnetic susceptibility; Radioactivity logging; Rivers; Seismology; Stratigraphy; Stresses; Structural geology; Boreholes

The Cretaceous-tertiary mass extinction, Chicxulub impact, and Deccan volcanism - Keller, G. (Earth and Life: Global Biodiversity, Extinction Intervals and Biogeographic Perturbations Through Time, 2012)
After three decades of nearly unchallenged wisdom that a large impact (Chicxulub) on Yucatan caused the end-Cretaceous mass extinction, this theory is facing its most serious challenge from the Chicxulub impact itself, as based on evidence in Texas and Mexico and from Deccan volcanism in India. Data generated from over 150 Cretaceous-Tertiary (KT) boundary sequences to date make it clear that the long-held belief in the Chicxulub impact as the sole or even major contributor to the KT mass extinction is not supported by evidence. The stratigraphic position of the Chicxulub impact ejecta spherules in NE Mexico and Texas and the impact breccia within the crater on Yucatan demonstrate that this impact predates the KTB by about 300,000 years. Planktic foraminiferal and stable isotope analyses across the primary impact ejecta layer reveal that not a single species went extinct as a result of this impact and no significant environmental changes could be determined. The catastrophic effects of this impact have been vastly overestimated. In contrast, recent advances in Deccan volcanic studies indicate three volcanic phases with the smallest at 67.5 Ma, the main phase at the end of the Maastrichtian (C29r), and the third phase in the early Danian C29r/C29n transition (Chenet et al. 2007). The main phase of eruptions occurred rapidly, was marked by the longest lava flows spanning 1500 km across India, and ended coincident with the KT boundary. The KT mass extinction may have been caused by these rapid and massive Deccan lava and gas eruptions that account for 80% of the entire 3500 m thick Deccan lava pile. © Springer Science+Business Media B.V. 2012.
cited By 32

Scientific drilling and biological evolution in ancient lakes: Lessons learned and recommendations for the future - Cohen, A.S. (Hydrobiologia, 2012)
Scientific drilling to recover sediment core and fossil samples is a promising approach to increasing our understanding of species evolution in ancient lakes. Most lake drilling efforts to date have focused on paleoclimate reconstruction. However, it is clear from the excellent fossil preservation and high temporal resolution typical of lake beds that significant advances in evolutionary biology can be made through drill core studies coordinated with phylogenetic work on appropriate taxa. Geological records can be used to constrain the age of specific lakes and the timing of evolutionarily significant events (such as lake level fluctuations and salinity crises). Fossil data can be used to test speciation and biogeographic hypotheses and flesh out phylogenetic trees, using a better-resolved fossil record to estimate timing of phylogenetic divergences. The extraordinary preservation of many fossils in anoxic lake beds holds the hope of collecting fossil DNA from the same body fossils that improve our understanding of morphological character evolution and adaptation. Moreover, fossils allow calibration of molecular clocks, which are currently largely inferential. Lake Malawi Drilling Project results provide some guideposts on what might be expected in a drilling project for studies of evolution. The extreme variability in lake level and environmental history that most ancient lakes experience (exemplified by the Lake Malawi record) demonstrates that no one drilling locality is likely to provide a complete record of phylogenetic history for a radiating lineage. Evolutionary biologists should take an active role in the design of drilling projects, which typically have interdisciplinary objectives, to ensure their sampling needs will be met by whatever sites in a lake are ultimately drilled. © 2011 Springer Science+Business Media B.V.
cited By 25
Keywords: adaptation; biogeography; divergence; drilling; fossil record; interdisciplinary approach; lake; paleoclimate; paleoenvironment; paleolimnology; phylogenetics; reconstruction; resolution; salinity; sediment core; speciation (biology)

Temporal and spatial corridors of Homo sapiens sapiens population dynamics during the Late Pleistocene and early Holocene - Richter, J{urgen; Melles, Martin; Sch{abitz, Frank (Quaternary International, 2012)
Keywords: Homo sapiens

Study on meter-scale cycles of the Lower Cretaceous Quantou Formation in SK-1 well (in Chinese with English abstract);[SK-1井下白垩统泉头组米级旋回研究] - Guo, J.; Wu, X.; Pan, J.; Wei, D.; Fu, J. (Lithologic Reservoirs, 2012)

Stochastic volume estimation and connectivity analysis at the Mallik gas hydrate field, Northwest Territories, Canada - Dubreuil-Boisclair, C.; Gloaguen, E.; Bellefleur, G.; Marcotte, D. (Leading Edge, 2012)
Gas hydrates located offshore and onshore beneath thick permafrost areas constitute one of the largest untapped natural gas resources. Yet, gas hydrate in place (GHIP) estimation at the scale of a field is not common in the scientific literature but is required to realistically assess the economical potential of specific accumulations. Progress in the last decade in Alaska and Canada has shown that gas hydrate accumulations beneath thick permafrost can be mapped at depth using conventional seismic attributes (Inks et al., 2009; Riedel et al. 2009). To evaluate the economic potential of gas hydrates in this environment, a test site at Mallik, Northwest Territories, Canada, was extensively surveyed (three-dimensional seismic, full set of logs in two wells, etc.) and a production test was realized in high gas-hydrate horizons. At Mallik, high P- and S-wave velocities, high acoustic impedances, and strong seismic amplitude reflections were all linked to sand-rich sediments with a high saturation of gas hydrates (Bellefleur et al. 2006; Riedel et al.). This relationship provides a strong basis for an integrated data characterization of this gas hydrate deposit. © 2012 Society of Exploration Geophysicists.
cited By 2
Keywords: Acoustic impedance; Energy resources; Gases; Hydration; Natural gas; Natural gas deposits; Offshore oil well production; Permafrost; Petroleum deposits; Seismic prospecting; Seismology; Shear waves; Stochastic systems; Connectivity analysis; Economic potentials; Hydrate accumulations; Natural gas resources; P- and S-wave velocities; Scientific literature; Seismic amplitudes; Volume estimations; Gas hydrates; connectivity; estimation method; gas hydrate; natural gas; permafrost; S-wave; stochasticity; Alaska; Canada; Northwest Territories; United States

Stochastic connectivity analysis and volume estimation at the Mallik gas hydrate reservoir, Mackenzie Delta, Canada - Dubreuil-Boisclair, C.; Gloaguen, E.; Bellefleur, G.; Marcotte, D. (Society of Exploration Geophysicists International Exposition and 82nd Annual Meeting 2012, SEG 2012, 2012)
This study focuses on the Mallik gas hydrate field, in the Northwest Territories, where 3D acoustic impedance and well log data from two wells are available. Firstly, collocated log data are used to infer the statistical relation between acoustic impedance and gas hydrate grade (product of saturation and porosity). Secondly, adapted stochastic Bayesian simulation is applied to generate multiple 3D models of gas hydrate grade fields integrating log data and lateral variability of 3D acoustic impedance. A statistical analysis of these scenarios allows the quantification of the in-place gas volumes. The simulation approach also allows estimating the uncertainty on these volumes. Then, connectivity analysis is computed on the three gas hydrate layers based on different grade cutoffs. The upper gas hydrate layers (zones A & B) show low connectivity and low grades. The deeper gas hydrate layer (Zone C) presents the highest connectivity that reaches the limit of the studied 3D grid, suggesting an even larger connected area of high gas hydrate grades. © 2012 SEG.
cited By 0
Keywords: Acoustic fields; Acoustic impedance; Gases; Geophysical prospecting; Hydration; Petroleum prospecting; Stochastic models; Stochastic systems; Uncertainty analysis; Well logging; Bayesian simulation; Connectivity analysis; Different grades; Gas hydrate reservoir; Simulation approach; Statistical relations; Volume estimations; Well log data; Gas hydrates

Source Characterization of near-surface chemical explosions at SAFOD - Pollitz, F.F.; Rubinstein, J.; Ellsworth, W. (Bulletin of the Seismological Society of America, 2012)
A series of near-surface chemical explosions conducted at the San Andreas Fault Observatory at Depth (SAFOD) main hole were recorded by highfrequency downhole receiver arrays in April 2005. These seismic recordings at depths ranging from the surface to 2.3 km constrain the shallow velocity and attenuation structure as well as the first-order characteristics of the source. Forward modeling of the explosions indicates that a source consisting of combined explosion, delayed implosion, and second-order moment-tensor components (corresponding to a distribution of vertical shear dislocations in the rock directly above the explosion) is sufficient to characterize the generated seismic wave fields to first order. Grid searches over source parameters controlling the nonexplosive components allow for the quantification of distributed vertical shear above the source and the estimation of the moment and time delay of the implosive component relative to the explosion. An estimated implosive to explosive moment ratio of 0.34 to 0.43 indicates a net static moment and positive macroscopic volume change.
cited By 3
Keywords: Chemical explosions; Downholes; First-order; Forward modeling; Grid search; High frequency HF; Moment ratio; Near-surface; Receiver array; San Andreas fault; Second orders; Seismic recording; Source characterization; Source parameters; Static moment; Vertical shear; Volume change; Strike-slip faults; Explosions; moment tensor; nuclear explosion; seismic attenuation; seismic velocity; seismic wave; source parameters

Solute geochemistry and its sources of the groundwaters in the Qinghai Lake catchment, NW China - Xiao, Jun; Jin, Zhang Dong; Zhang, Fei; Wang, Jin (Journal of Asian Earth Sciences, 2012)
Major ion compositions were analyzed in 65 groundwater samples to decipher water quality, solute geochemistry and sources of groundwater within the Qinghai Lake catchment, NE Tibetan Plateau. Groundwaters were slightly alkaline with pH varying from 7.2 to 8.7. The total dissolved solids (TDS) varied over two orders of magnitude from fresh (88%) to brackish (12%) with a mean value of 672mg/L, higher than river waters within the Qinghai Lake catchment and river waters draining the Himalayas and the southeastern Tibetan Plateau. Most of the samples, approximately 80%, were the Ca 2+-Mg 2+-HCO3- type and suitable for drinking and irrigation. Some of the Lakeside, the Buha and the Qinghai Lake water were the Na +-Cl - type and not suitable for drinking and irrigation. Water quality of Hargai and Shaliu samples was better than the others. Rock weathering, ion exchange and precipitation are the major geochemical processes responsible for the solutes in the groundwater within the Qinghai Lake catchment. Anthropogenic input to the groundwater is minor. The forward models on the input of groundwaters from various sources showed that the contributions were 40.1% for carbonate weathering, 29.0% for evaporite dissolution, 16.8% for atmospheric input and 14.1% for silicate weathering of the total dissolved cations for the whole catchment. Evaporite dissolution was dominating in the Lakeside, the Buha and the Daotang samples, contributing 15.3-45.9%, 20.4-61.1% and 21.3-63.9% of the total dissolved cations, respectively. Carbonate weathering was dominated in the Shaliu and the Hargai samples, contributing 23.9-71.7% and 31.8-95.4% of the total dissolved cations, respectively. The result also demonstrated that carbonate weathering had higher contribution to the groundwaters than silicate weathering. © 2012 Elsevier Ltd.
Keywords: China; Himalayas; Qinghai; Qinghai-Xizang Plateau; catchment; dissolution; groundwater; ion exchange; ionic composition; river water; solute; water quality; weathering

Shear wave anisotropy from cross-correlation of seismic noise in the Parkfield pilot hole - Lewis, M.A.; Gerstoft, P. (Geophysical Journal International, 2012)
We use cross-correlation of seismic noise recorded at stations in the San Andreas Fault Observatory at Depth (SAFOD) pilot hole to extract P and S waves and measure S-wave anisotropy on the horizontal components. The data are recorded at seven three-component stations at depths from 1857 to 2097 m in the pilot hole. In late September and early 2004 October drilling noise underneath the stations generated propagating waves, which were absent in the rest of October. Estimates of the P- and S-wave velocities from the cross-correlations, on the vertical and horizontal components, respectively, are consistent with velocity measurements taken directly in the borehole. We observe polarization of the S wave, with a fast polarization direction of 120°-130° that is 4 per cent faster than the slow direction. Cross-correlation of the seismic noise can accurately determine S-wave anisotropy. © 2011 The Authors Geophysical Journal International © 2011 RAS.
cited By 6
Keywords: Body waves; Cross correlations; Drilling noise; P- and S-waves; Pilot holes; Polarization direction; S-wave velocity; S-waves; San Andreas Fault; Seismic anisotropy; Seismic noise; Shear-wave anisotropy; Three-component; Anisotropy; Interferometry; Polarization; Seismology; Shear waves; Velocity measurement; Shear flow; borehole; correlation; interferometry; P-wave; S-wave; San Andreas Fault; seismic anisotropy; seismic noise; wave propagation; wave velocity; California; Parkfield; United States

Seismicity-based estimation of the driving fluid pressure in the case of swarm activity in Western Bohemia - Hainzl, S.; Fischer, T.; Dahm, T. (Geophysical Journal International, 2012)
Two recent major swarms in Western Bohemia occurred in the years 2000 and 2008 within almost the same portion of a fault close to Novy Kostel. Previous analysis of the year 2000 earthquake swarm revealed that fluid intrusion seemed to initiate the activity whereas stress redistribution by the individual swarm earthquakes played a major role in the further swarm evolution. Here we analyse the new swarm, which occurred in the year 2008, with regard to its correlation to the previous swarm as well its spatiotemporal migration patterns. We find that (i) the main part of the year 2008 activity ruptured fault patches adjacent to the main activity of the swarm 2000, but that also (ii) a significant overlap exists where earthquakes occurred in patches in which stress had been already released by precursory events; (iii) the activity shows a clear migration which can be described by a 1-D (in up-dip direction) diffusion process; (iv) the migration pattern can be equally well explained by a hydrofracture growth, which additionally explains the faster migration in up-dip compared to the down-dip direction as well as the maximum up-dip extension of the activity. We use these observations to estimate the underlying fluid pressure change in two different ways: First, we calculate the stress changes induced by precursory events at the location of each swarm earthquake assuming that observed stress deficits had to be compensated by pore pressure increases; and secondly, we estimate the fluid overpressure by fitting a hydrofracture model to the asymmetric seismicity patterns. Both independent methods indicate that the fluid pressure increase was initially up to 30 MPa. © 2012 The Authors Geophysical Journal International © 2012 RAS.
Keywords: Bohemia; Czech Republic; Diffusion in liquids; Estimation; Faulting; Diffusion process; Earthquake dynamics; Earthquake source; Earthquake swarms; Fluid pressures; Hydro-fracture; Migration patterns; Overpressure; Pressure increase; Seismicity pattern; Stress changes; Stress redistribution; earthquake precursor; earthquake swarm; fault; fluid pressure; fracture; geostatistics; seismic migration; seismic source; seismicity; seismology; Earthquakes

Seismic imaging of the Scandinavian Caledonides to define ICDP drilling sites - Hedin, P.; Juhlin, C.; Gee, D. G. (Tectonophysics, 2012)
A 36 kilometer long high resolution 2D seismic reflection profile was acquired in the summer of 2010 to be used in the planning of the COSC (Collisional Orogeny in the Scandinavian Caledonides) Deep Drilling Project. Two fully cored boreholes, each to c. 2.5 km depth, are planned for the Åre-M{orsil area of west-central Sweden in order to increase our understanding of orogenic processes and, in particular, the tectonic evolution of the Scandinavian Caledonides. Besides providing important sub-surface structural information in the vicinity of the potential drill sites, the seismic profile also provides detailed, high resolution images previously not available for the uppermost few kilometers in the region. The subsurface is highly reflective and very complex down to at least 9 km depth (the limit of decoded data) with clear reflections spanning the entire length of the profile. Correlation with previous regional reflection seismic and magnetotelluric surveys has been achieved by acquisition of a short (7 km) connecting profile. A clearly defined reflection, present in the new profile at depths between c. 2.5 km in the east and c. 4.5 km in the west and with an average westwards dip of c. 3.5°, apparently defines the base of the Lower Allochthon. Closer to the Caledonian front, this sole thrust overlies the Cambrian alum shale formation, which rests unconformably on the autochthonous Precambrian crystalline basement. The latter is remarkable for its deep internal reflectivity which is probably related to mafic intrusions in a dominantly granitic host-rock; their deformation may be of both Caledonian and older (e.g. Sveconorwegian) age. The new high resolution seismic data provide the basis for locating the first borehole in the Seve Nappe Complex. They also demonstrate that the second hole, designed to penetrate the Caledonian basement, will have to be located further east than was originally planned.
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Keywords: Reflection seismic; Collisional orogeny; Borehole; Migration; Continental Scientific Drilling; Scandinavian Caledonides

Seismic imaging of gas hydrate accumulations beneath thick permafrost areas of the Mackenzie Delta, NWT, Canada - Bellefleur, G.; Riedel, M.; Brent, T. (Society of Petroleum Engineers - Arctic Technology Conference 2012, 2012)
The Mackenzie Delta in Canada's Northwest Territories hosts many permafrost-related gas hydrate accumulations that were indirectly discovered or inferred from conventional hydrocarbon exploration programs. In particular, gas hydrate intervals characterized with high saturation show high resistivity and high P- and S-wave velocity on well-log data, and are typically found in sand-rich horizons. As demonstrated at the Mallik site, the velocity contrast between highly saturated gas hydrate-bearing sediments and unconsolidated water-bearing sediments is significant and allows their detection with seismic data. Here, we use 2D and 3D seismic reflection data acquired by industry on Richards Island to map and characterize gas hydrate accumulations beneath a thick permafrost area of the Mackenzie Delta. Specifically, we show new seismic evidences of gas hydrate accumulations near YaYa, Ivik and Umiak. The presence of gas hydrate was previously inferred from well-log data in several boreholes located in those areas. All seismic data were re-processed following an AVO-friendly flow that preserved relative amplitude relationships. On such data, the strong acoustic impedance of gas hydrate produces strong amplitude seismic reflections. The seismic signature of gas hydrates is confirmed by seismic-to-well correlation in areas where boreholes are available. Results indicate that gas hydrate accumulations occur in structurally-controlled plays typical of conventional oil and gas traps found in this area, and further demonstrate that gas hydrates are part of the regional petroleum system. Copyright 2012, Offshore Technology Conference.
cited By 0
Keywords: Acoustic impedance; Aquifers; Boreholes; Gases; Gasoline; Hydration; Oil well logging; Permafrost; Petroleum prospecting; Seismic prospecting; Seismic response; Seismic waves; Shear waves; Wave propagation; Well logging; Conventional hydrocarbons; Conventional oil and gas; Hydrate accumulations; P- and S-wave velocities; Relative amplitude; Seismic reflections; Seismic signatures; Velocity contrasts; Gas hydrates

Seismic evidence of up to 200m lake-level change in Southern Patagonia since Marine Isotope Stage 4 - Gebhardt, Andrea Catalina; Ohlendorf, Christian; De Batist, Marc; Anselmetti, Flavio S.; Ariztegui, Daniel; Kliem, Pierre; Wastegård, Stefan; Zolitschka, Bernd (Sedimentology, 2012)
Maar lake Laguna Potrok Aike is located north of the Strait of Magellan (south-eastern Patagonia). Seismic reflection profiles revealed a highly dynamic palaeoclimate history. Dunes were identified in the eastern part of the lake at approximately 30 to 80m below the lake floor, overlying older lacustrine strata, and suggest that the region experienced dry conditions probably combined with strong westerly winds. It is quite likely that this can be linked to a major dust event recorded in the Antarctic ice cores during Marine Isotope Stage 4. The dunes are overlain by a series of palaeo-shorelines indicating a stepwise water-level evolution of a new lake established after this dry period, and thus a change towards wetter conditions. After the initial, rapid and stepwise lake-level rise, the basin became deeper and wider, and sediments deposited on the lake shoulder at approximately 33m below present-day lake level point towards a long period of lake-level highstand between roughly 53·5kacal. bp and 30kacal. bp with a maximum lake level some 200m higher than the desiccation horizon. This highstand was then followed by a regressional phase of uncertain age, although it must have happened some time between approximately 30kacal. bp and 6750yrscal. bp. Dryer conditions during the Mid-Holocene are evidenced by a dropping lake level, resulting in a basin-wide erosional unconformity on the lake shoulder. A second stepwise transgression between ca 5·8 to 5·4kacal. bp and ca 4·7 to 4kacal. bp with palaeo-shorelines deposited on the lake shoulder unconformity again indicates a change towards wetter conditions. © 2011 The Authors. Journal compilation © 2011 International Association of Sedimentologists.
Keywords: Argentina; Laguna Potrok Aike; Magellan Strait; Patagonia; Santa Cruz [Argentina]; Anoxic sediments; Climate change; Glacial geology; Isotopes; Seismic waves; Argentina; ICDP project PASADO; Laguna potrok aike; Lake-level variations; Patagonia; Seismic reflection profiles; climate variation; desiccation; dune; ice core; lacustrine deposit; lake level; marine isotope stage; paleoclimate; sedimentation; seismic reflection; shoreline; transgression; unconformity; water level; Lakes

Seismic anisotropy in the crystalline upper crust: Observations and modelling from the Outokumpu scientific borehole, Finland - Schijns, Heather; Schmitt, Douglas R.; Heikkinen, Pekka J.; Kukkonen, Ilmo T. (Geophysical Journal International, 2012)
Seismic velocity anisotropy measurements are made of a fractured metamorphic formation from the 2.5-km-deep International Continental Scientific Drilling Programme (ICDP) borehole in Outokumpu, Finland. Three component walk-away vertical seismic profile (VSP) measurements are made along two source-line azimuths at three receiver depths (1000, 1750 and 2500 m) and incidence angle-dependent qP- and qS-wave velocities are extracted with a τ-p method. The highest qP-wave anisotropy, 13.6 per cent (v fast= 6160 m s -1, v slow= 5370 m s -1), is measured between 1000- and 1750-m depth, with anisotropy of up to 9.4 per cent (v fast= 6090 m s -1, v slow= 5540 m s -1) measured between 1750 and 2500 m depth. The top ∼1300 m of the region is composed of a homogeneous, strongly intrinsically anisotropic biotite-rich schist, and is sampled by the shallowest walk-away profile. Anisotropy of up to 11.1 per cent (v fast= 5950 m s -1, v slow= 5320 m s -1) is measured by the walk-away VSP between 50 and 1000 m depth, along with shear wave splitting averaging 5 per cent (180 m s -1). Laboratory-derived intrinsic anisotropy of the schist cannot by itself explain the degree or orientation of the anisotropy measured in the walk-away VSPs, however, a model which modifies the intrinsic stiffnesses by the inclusion of a single set of dipping, aligned cracks allows the observed in situ velocities to be reproduced. Forward modelling of the qP-wave walk-away VSP measurements from 50 to 1000 m depth is undertaken using an effective medium model to develop a 3-D velocity model of this region. An orthorhombic medium is used to represent the intrinsic anisotropy of the biotite-rich schist, and a single set of aligned cracks is added to give a bulk elastic stiffness. The resulting model predicts the schist to have an overall anisotropy of 16.8 per cent, with qP-wave velocities of up to 6315 m s -1. The accuracy of the model is assessed through its fit to the walk-away VSP measurements as well as a comparison to known geology of the region. © 2012 The Authors Geophysical Journal International © 2012 RAS.
Keywords: Finland; Outokumpu; Pohjois-Karjala; Anisotropy; Cracks; Mica; Seismology; Stiffness; Three dimensional; Velocity; Angle-dependent; Cratons; Downholes; Effective medium model; Elastic stiffness; Finland; Forward modelling; In-situ; Intrinsic anisotropy; Scientific drilling; Seismic anisotropy; Seismic velocities; Shear wave splitting; Three component; Upper crust; Velocity model; Vertical seismic profiles; accuracy assessment; biotite; borehole; crystallization; forward modeling; fracture zone; homogeneity; in situ measurement; observational method; P-wave; S-wave; seismic anisotropy; seismic velocity; stiffness; three-dimensional modeling; upper crust; wave splitting; well logging; Seismic prospecting

Late Cretaceous chronostratigraphy (Turonian-Maastrichtian): SK1 core Songliao Basin, China - Scott, R.W.; Wan, X.; Wang, C.; Huang, Q. (Geoscience Frontiers, 2012)
Non-marine ostracodes, charophytes and palynomorphs are abundant in most Cretaceous lacustrine basins of East Asia. However, their ranges are not directly integrated with marine biota that defines the Cretaceous stages. Non-biotic events such as magnetochrons and radiometric ages in these terrestrial deposits enable their correlation with marine strata. The SK1 north and south composited cores in the Songliao Basin present a continuous section of Upper Cretaceous non-marine fossil and magnetochron successions in superposed order. These chronostratigraphic events are integrated with marine events by an X/Y graphic plot between the core data and a global database of Global Section and Stratotype Points (GSSP) and key reference sections. This plot projects stage boundaries in marine sections into the SK1 section and interpolates numerical ages to the first and last occurrences of biota and to lithostratigraphic boundaries. This stratigraphic experiment tests and refines age calibrations based on both manual interpolation of depths to numerical ages and cyclostratigraphy. Ages derived by interpolation are similar and ages by cyclostratigraphy are older because stage boundaries are calibrated to a different age scale. © 2011, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. All rights reserved.
cited By 42
Keywords: age determination; charophyte; chronostratigraphy; cyclostratigraphy; lithostratigraphy; Maastrichtian; ostracod; palynomorph; Turonian; China; Songliao Basin; Characeae; Ostracoda

The annual particle cycle in Lake Van (Turkey) - Stockhecke, M.; Anselmetti, F.S.; Meydan, A.F.; Odermatt, D.; Sturm, M. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2012)
The varved sediments of Lake Van provide a high-quality continental archive of seasonal to decadal-scale climate variability. In order to read the natural record, modern varve formation was studied on the basis of (1) remotely-sensed total suspended-matter (TSM rs) concentrations; (2) time-series of particle flux and water temperatures; and (3) turbidity, temperature, and oxygen profiles. TSM rs, validated by contemporaneous water-column sampling, shows great temporal and lateral variations (whitings and turbidity plumes). From 2006 to 2009, sequential sediment traps recorded high particle fluxes during spring and fall, medium fluxes during summer, and almost zero flux during winter. The mean total mass flux of 403mgm -2day -1 comprised 33% (seasonally up to 67%) calcium carbonate, 7% aquatic organic matter, 6% biogenic opal, and 54% detrital minerals. The CaCO 3 fluxes are controlled by river discharge (precipitation and snowmelt) during spring, by high productivity during summer, and by river discharge (precipitation before snowfall starts) and mixing during fall. In November 2007, an anomalously high CaCO 3 flux occurred as a result of a warm water surface supersaturated with calcite coinciding with an anomalous runoff event. The results demonstrate that the couplets of light and dark laminae in the short sediment cores are true varves representing spring-summer-fall and winter conditions, respectively. Consequently, varve formation can be linked to the seasonal climate pattern, providing a calibration that can be used to interpret the partially varved paleo-record of Lake Van and related environmental processes. © 2012 Elsevier B.V.
cited By 46
Keywords: calcium carbonate; concentration (composition); continental shelf; decadal variation; lacustrine deposit; oxygen; paleoenvironment; precipitation (climatology); remote sensing; river discharge; runoff; satellite data; sediment chemistry; sediment core; sediment trap; snowmelt; suspended particulate matter; time series; turbidity; water column; water temperature; Lake Van; Turkey

Isotopic evidence for a sizeable seawater sulfate reservoir at 2.1 Ga - Reuschel, M; Melezhik, VA; Whitehouse, MJ; Lepland, A; Fallick, AE; Strauss, H (Precambrian Research, 2012)

1 The Imandra/Varzuga Greenstone Belt - Melezhik, VA (Reading the Archive of Earth’s Oxygenation: Volume 1: The Palaeoproterozoic of Fennoscandia as Context for the Fennoscandian Arctic Russia-Drilling Early Earth Project, 2012)

Compositional diversity of Mauna Kea shield lavas recovered by the Hawaii Scientific Drilling Project: Inferences on source lithology, magma supply, and the role of multiple volcanoes - Rhodes, J. Michael; Huang, Shichun; Frey, Frederick A.; Pringle, Malcolm; Xu, Guangping (Geochemistry, Geophysics, Geosystems, 2012)
[1] The final Stage (Phase-2) of the Hawaii Scientific Drilling Project (HSDP) recovered 408 m of basaltic core (3098-3506 mbsl) attributed to Mauna Kea volcano. We determined the major and trace element composition of 40 samples from this core. Our results show that the incompatible element ratios, such as Zr/Nb, which are correlated with Pb isotopic ratios, are more variable in the lower 408 m of Mauna Kea shield lavas than in the overlying 2855 m ( 450 ka). We argue that this geochemical diversity was present in the mantle source of Mauna Kea shield lavas and does not require the inter-fingering of lavas from adjacent volcanoes. Because of uncertainties in Ni partitioning between olivine and melt and the wide range of Ni contents in peridotites, we show that all Mauna Kea lavas may have been derived from a peridotite source. We also obtained major and trace element compositions for 24 whole-rock clasts and hyaloclastites and 7 glasses from HSDP Phase-1 core between 1767 and 1808 mbs. These enigmatic lavas, previously recognized by the distinctive high CaO and K2O contents of their glasses, are also relatively enriched in highly incompatible trace elements. We show that this group of lavas have affinities with post-shield lavas and argue that they are a consequence of lower degrees of melting ( a factor of two) than other Mauna Kea shield lavas, thereby providing evidence that magma supply varied significantly during the growth of the Mauna Kea shield. Copyright 2012 by the American Geophysical Union.
Keywords: Hawaii [(ISL) Hawaiian Islands]; Hawaii [United States]; Hawaiian Islands; Mauna Kea; United States; Glass; Lead; Lithology; Olivine; Hawaiian volcanism; Hyaloclastites; Incompatible element; Isotopic ratios; Major and trace elements; Mantle plume; Mantle source; Mauna Kea; Ni content; Scientific drilling; geochemistry; isotopic ratio; lava; lead isotope; lithology; magma; mantle plume; mantle source; olivine; partitioning; peridotite; shield volcano; trace element; volcanism; Volcanoes

Climatic change recorded in the sediments of the Chew Bahir basin, southern Ethiopia, during the last 45,000 years - Foerster, V.; Junginger, A.; Langkamp, O.; Gebru, T.; Asrat, A.; Umer, M.; Lamb, H.F.; Wennrich, V.; Rethemeyer, J.; Nowaczyk, N.; Trauth, M.H.; Schaebitz, F. (Quaternary International, 2012)
East African paleoenvironments are highly variable, marked by extreme fluctuations in moisture availability, which has far-reaching implications for the origin, evolution and dispersal of Homo sapiens in and beyond the region. This paper presents results from a pilot core from the Chew Bahir basin in southern Ethiopia that records the climatic history of the past 45 ka, with emphasis on the African Humid Period (AHP, ∼15-5 ka calBP). Geochemical, physical and biological indicators show that Chew Bahir responded to climatic fluctuations on millennial to centennial timescales, and to the precessional cycle, since the Last Glacial Maximum. Potassium content of the sediment appears to be a reliable proxy for aridity, showing that Chew Bahir reacted to the insolation-controlled humidity increase of the AHP with a remarkably abrupt onset and a gradual termination, framing a sharply defined arid phase (∼12.8-11.6 ka calBP) corresponding to the Younger Dryas chronozone. The Chew Bahir record correlates well with low- and high-latitude paleoclimate records, demonstrating that the site responded to regional and global climate changes. © 2012 Elsevier Ltd and INQUA.
cited By 101
Keywords: climate variation; lacustrine deposit; Last Glacial Maximum; paleoclimate; paleoenvironment; Younger Dryas; Ethiopia; Homo sapiens

Climate and environmental change in the Balkans over the last 17 ka recorded in sediments from Lake Prespa (Albania/F.Y.R. of Macedonia/Greece) - Aufgebauer, Anne; Panagiotopoulos, Konstantinos; Wagner, Bernd; Schaebitz, Frank; Viehberg, Finn A.; Vogel, Hendrik; Zanchetta, Giovanni; Sulpizio, Roberto; Leng, Melanie J.; Damaschke, Magret (Quaternary International, 2012)
This paper presents sedimentological, geochemical, and biological data from Lake Prespa (Albania/Former Yugoslav Republic of Macedonia/Greece). The 320 cm core sequence (Co1215) covers the last 17 ka calBP and reveals significant change in climate and environmental conditions on a local and regional scale. The sediment record suggests typical stadial conditions from 17.1 to 15.7 ka calBP, documented through low lake productivity, well-mixed conditions, and cold-resistant steppe catchment vegetation. Warming is indicated from 15.7 ka calBP with slightly increased in-lake productivity, gradual expansion of trees, and decreasing erosion through disappearance of local ice caps. Between 14.5 and 11.5 ka calBP relatively stable hydrological conditions are documented. The maximum in tree taxa percentages during the Bølling/Allerød interstadial (14.5-13.2 ka calBP) indicates increased temperatures and moisture availability, whereas the increase of cold-resistant open steppe vegetation taxa percentages during the Younger Dryas (13.2-11.5 ka calBP) is coupled with distinct colder and drier conditions. The Holocene sequence from 11.5 ka calBP indicates ice-free winters, stratification of the water column, a relatively high lake trophic level and dense vegetation cover over the catchment. A strong climate related impact on the limnology and physical parameters in Lake Prespa is documented around 8.2 ka through a significant decrease in productivity, enhanced mixing, strong decomposition and soil erosion, and a coeval expansion of herbs implying cool and dry climate conditions. Intensive human activity in the catchment is indicated from around 1.9 ka calBP. This multiproxy approach improves our understanding of short- and long-term climate fluctuations in this area and their impact on catchment dynamics, limnology, hydrology, and vegetation. © 2012 Elsevier Ltd and INQUA.
Keywords: Albania; Balkan; Greece; Lake Mikri Prespa; Macedonia [Greece]; Turkmenistan; climate conditions; climate variation; environmental change; geochemistry; Holocene; human activity; ice cap; lacustrine deposit; limnology; paleoclimate; paleoenvironment; sediment core; sedimentology; warming; water column; Younger Dryas

Clay fabrics in SAFOD core samples - Janssen, C.; Kanitpanyacharoen, W.; Wenk, H.-R.; Wirth, R.; Morales, L.; Rybacki, E.; Kienast, M.; Dresen, G. (Journal of Structural Geology, 2012)
With optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and synchrotron X-ray diffraction measurements, we analyzed clay microfabrics in ultracataclastic/gouge and cataclastic core samples obtained from the main bore hole of the San Andreas Fault observatory at depth (SAFOD). The analysis reveals a significant contrast between weak clay fabrics observed in the core samples with synchrotron X-ray fabric measurements and strong degree of preferred alignment for clay particles documented with the optical microscope. TEM and SEM observations also show distinct zones of locally aligned and randomly oriented clay minerals. The lack of a strong fabric may be attributed to randomly oriented matrix sheet silicates dominating the fault rocks. The presence of weak fabrics in intensely strained ultracataclasites/fault gouges is attributed to 1) newly formed clay minerals that grew in many orientations, 2) folded and kinked clay minerals, and 3) clay particles that are wrapped around grains. In addition, the locally aligned clay particles may act as barriers to fluid flow, which in turn decrease porosity, expel intergranular pore fluids, and consequently, may increase fluid pressure. © 2012 Elsevier Ltd.
cited By 22
Keywords: Clay fabrics; Clay particles; Fault rock; Fluid pressures; Intergranular pores; Micro fabric; Optical microscopes; Oriented matrix; Phyllosilicate; SAFOD; San Andreas fault; SEM observation; Synchrotron x ray diffraction; Synchrotron x rays; Transmission electron microscopy tem; Clay minerals; Optical microscopy; Scanning electron microscopy; Silicates; Strike-slip faults; Tectonics; Textures; Transmission electron microscopy; X ray diffraction; Core samples; clay mineral; core (planetary); fault gouge; fluid flow; petrofabric; phyllosilicate; porosity; San Andreas Fault; scanning electron microscopy; texture; transmission electron microscopy; X-ray diffraction

Chlorite-smectite clay minerals and fault behavior: New evidence from the San Andreas Fault Observatory at Depth (SAFOD) core - Schleicher, A.M.; Pluijm, B.A.; Warr, L.N. (Lithosphere, 2012)
Segments of the modern San Andreas fault experience creep behavior, which is attributed to various factors, including (1) low values of effective normal stress, (2) elevated pore-fluid pressure, and (3) low frictional strength. The San Andreas Fault Observatory at Depth (SAFOD) drill hole in Parkfield, California, provides new insights into frictional properties by recognizing the importance of smectitic clay minerals, as demonstrated by analysis of mudrock and fault gouge samples from zones between 3186 and 3199 m and 3295 and 3313 m measured depths. X-ray diffraction (XRD) results show illite, chlorite, and mixed-layered illite-smectite and chlorite-smectite minerals in the faulted mudrock, whereas serpentine, Mg-rich smectite, and chlorite-smectite minerals are concentrated in the southwest deformation zone and the central deformation zone of the two actively creeping sections in the San Andreas fault. These rocks are abundantly coated by shiny clay mineral layers in some cases, reflecting mineral formation during creep. Secondary- and transmission-electron microscopy (SEM/TEM) and XRD studies of these slip surface coatings reveal thin films of neoformed chlorite-smectite phases, similar to previously described illite-smectite microscale precipitations. The abundance of chlorite-smectite minerals within fault rock of the SAFOD borehole significantly extends the potential role of mineralogic processes to depths up to 10 km, with cataclasis and fluid infiltration creating nucleation sites for neomineralization on displacement surfaces. We propose that localization of illitic to chloritic smectite clay minerals on slip surfaces from near the surface to the brittle-ductile transition promotes creep behavior of faults. © 2012 Geological Society of America.
cited By 53
Keywords: Creep; Friction; High resolution transmission electron microscopy; Observatories; Serpentine; Silicate minerals; Strike-slip faults; Structural geology; X ray diffraction; Brittle ductile transitions; Deformation zone; Effective normal stress; Frictional properties; Frictional strength; Mineral formation; Pore fluid pressure; San Andreas fault; Clay minerals; brittle deformation; chlorite; creep; fault displacement; fluid pressure; infiltration; mudstone; precipitation (chemistry); smectite; California; Parkfield; United States

Chemistry and thermometry of geothermal water from Mountain Home test well MH-2B S: Preliminary results - Lachmar, T.E.; Freeman, T.G.; Wood, T.R.; Shervais, J.W.; Nielson, D.L. (Transactions - Geothermal Resources Council, 2012)
A geothermal test well at Mountain Home AFB in southwestern Idaho encountered artesian flow of geothermal water from a depth of 1,745 m. Samples taken from the well head after 12 hours of flow had a pH of 9.59, and an electrical conductivity of 870 μS. The high pH suggests that the water is at equilibrium with weathered basalt at the measured temperature. The water is high in sulfate relative to chloride and bicarbonate, and high in sodium relative to calcium and magnesium, but has a TDS content of only 1,120 mg/L. Pyrite is probably the source of the sulfate. Deuterium and oxygen-18 levels are -88 and -3.2 per mil, respectively, suggesting that the water is old, not meteoric, and/or has undergone significant fractionation. Calculated equilibrium temperatures vary from ∼134°C to ∼154°C. The calculated temperatures are similar to those measured in the test well. The data suggest a potential electric-grade resource. Further work is in progress.
cited By 4
Keywords: Calcium and magnesiums; Electrical conductivity; Equilibrium temperatures; Geothermal water; Hot spot; Measured temperatures; Mountain Home; Snake river plains; Basalt; Chemistry; Chlorine compounds; Electric conductivity; Geothermal fields; Landforms; Sodium bicarbonate; Sodium sulfate; Geothermal wells

Characteristics and petroleum geologic significances of clay rims in sandstones of Mingshui Formation, well Songke 1, Songliao Basin - Meiyan, Fu; Shaonan, Zhang; Xiaoqi, Ding; Qiming, Liao; Di, Xiong; Zhiliang, Zhu (石油实验地质, 2012)

Carbon isotopes in surface-sediment carbonates of modern Lake Qinghai (Qinghai-Tibet Plateau): Implications for lake evolution in arid areas - Li, Xiangzhong; Liu, Weiguo; Xu, Liming (Chemical Geology, 2012)
To further investigate the significance of carbon isotopes of lake carbonates in arid areas, we examined the carbon isotopic composition of ostracods, bulk carbonate, fine-grained carbonates, and associated water DIC (dissolved inorganic carbon) from Lake Qinghai and several small lakes and ponds surrounding Lake Qinghai. We obtained three major results. 1) The carbon isotopic compositions of ostracods, bulk carbonate, and fine-grained carbonates in the lakes and ponds are clearly correlated with water δ 13C DIC values, which vary with water salinity in the Lake Qinghai area. 2) The variation in the δ 13C DIC values of lake water is mainly controlled by CO 2 exchanges between the atmosphere and lake waters in the Lake Qinghai area. 3) Ostracods, bulk carbonate and fine-grained carbonates show consistent trends of isotopic composition in the study area, and the differences in carbon isotopic composition between authigenic carbonates and ostracods may be explained by the differences in carbon isotopic composition between the DIC of surface water and that of the water near to the sediment-water interface as well as the 'vital offsets' of ostracods.Our results suggest that variations in the δ 13C values of carbonates in Lake Qinghai and other lakes in this arid, high-altitude area are primarily controlled by the carbon-isotope ratios of the lake water DIC, which in turn are related to water salinity. Therefore, changes in carbonate δ 13C values may be used to indirectly indicate changes in water salinity in the Lake Qinghai area. © 2012 Elsevier B.V..
Keywords: China; Qinghai; Qinghai Lake; Ostracoda; Animals; Anoxic sediments; Arid regions; Carbon; Carbon dioxide; Carbonates; Carbonation; Isotopes; Sedimentology; Arid area; Authigenic carbonates; Carbon isotopes; Carbon isotopic composition; Dissolved inorganic carbon; High altitude; Isotopic composition; Lake Qinghai; Lake waters; Ostracods; Qinghai Tibet plateau; Sediment water interface; Study areas; Water salinity; arid region; carbon isotope; carbonate sediment; dissolved inorganic carbon; isotopic composition; isotopic ratio; lacustrine deposit; ostracod; Lakes

Carbon chain length distribution in n-alkyl lipids: A process for evaluating source inputs to Lake Qinghai - Wang, Zheng; Liu, Weiguo (Organic Geochemistry, 2012)
Lake sediments generally contain a mixture of terrestrial and aquatic source inputs, and determining the major inputs is important for understanding geological records in paleoenvironment and paleoclimate research. In this study we describe the distribution of n-alkanes and n-fatty acids (FAs) in representative modern plants from around Lake Qinghai. We found a significant difference in the average length of n-FA carbon chains (ACL Fa 16-32) in terrestrial (23.3) and aquatic plants (18.6). The results reveal that ACL Fa 16-32 may essentially serve as a proxy for evaluating the major source inputs to lake sediments. Assessment of surface sediments from the lake showed that the FAs originated from a mixture of inputs, with the aquatic source input predominant at most sites.Additionally, the δD values of sediment mid-chain n-acids (C 22) showed a relationship with the ACL Fa 16-32 proxy: an increased Fa ACL corresponded to more negative hydrogen isotope ratio values. We suggest that different sources should be considered and ACL Fa 16-32 could be a potential calibration proxy before using δD values to extract reliable isotopic information from lake water. More attention should be paid to source inputs and their relationship to other geochemical proxies in future studies of lake sediments. © 2012 Elsevier Ltd.
Keywords: China; Qinghai; Qinghai Lake; Carbon; Hydrogen; Isotopes; Paraffins; Sedimentology; Sediments; Aquatic plants; Average length; Carbon chains; Carbon-chain length; Geochemical proxies; Hydrogen isotope; Isotopic information; Lake Qinghai; Lake sediments; Lake waters; n-Alkanes; Paleo-environment; Paleoclimate research; Surface sediments; alkane; carbon; fatty acid; geological record; hydrogen isotope; lacustrine deposit; lake water; paleoclimate; paleoenvironment; sediment chemistry; Lakes