All ICDP Publications with Abstracts
From parent-sysfolder "Publications" + 2 folder-levels deep
1544.
Diversity and spatial distribution of extant freshwater ostracodes (crustacea) in ancient Lake Ohrid (Macedonia/Albania)
Diversity,
6
(3)
524 – 550
2014
ISSN: 14242818
Publisher: MDPI AG
DOI:10.3390/d6030524
Keywords:▾
Albania; Greece; Lake Ohrid; Macedonia [Greece]; Crustacea; Ostracoda; anthropogenic effect; biodiversity; endemism; human activity; intertidal environment; ostracod; spatial distribution; species diversity; species evenness; species richness; taxonomy; water depth
Abstract: ▾ We carried out an intensive sampling survey in ancient Lake Ohrid (Macedonia/Albania), covering all seasons, to determine total species number, relative species abundances and spatial distribution of Ostracoda. We identified 32 living species that belong to seven families (Candonidae, Ilyocyprididae, Cyprididae, Leptocytheridae, Limnocytheridae, Cytherideidae, and Darwinulidae) and 15 genera (Candona, Fabaeformiscandona, Candonopsis, Cypria, Cyclocypris, Ilyocypris, Eucypris, Prionocypris, Bradleystrandesia, Herpetocypris, Dolerocypris, Amnicythere, Paralimnocythere, Cytherissa, and Darwinula). Six additional species were identified from empty carapaces and valves. Dominant families in Lake Ohrid were Candonidae and Limnocytheridae, representing 53% and 16% of all species, respectively. Prevalence of species flocks in these two families confirms the "young" ancient status of the lake. Amnicythere displays a preference for oligo-haline to meso-haline waters, but some species are found in saline environments, which suggests Lake Ohrid has a marine history. Recent studies, however, indicate fluvial/glaciofluvial deposition at the onset of Lake Ohrid sedimentation. Candona is the most diverse genus in Lake Ohrid, represented by 12 living species. Paralimnocythere is represented by five living species and all other genera are represented by one or two species. Reports of Candona bimucronata, Ilyocypris bradyi, Eucypris virens, Eucypris sp., Prionocypris zenkeri, Bradleystrandesia reticulate, Herpetocypris sp. 2, and Dolerocypris sinensis are firsts for this lake. Living ostracodes were collected at the maximum water depth (280 m) in the lake (Candona hadzistei, C. marginatoides, C. media, C. ovalis, C. vidua, Fabaeformiscandona krstici, Cypria lacustris, C. obliqua and Amnicythere karamani). Cypria lacustris was overall the most abundant species and Cypria obliqua displayed the highest abundance at 280 m water depth. Principal environmental variables that influence ostracode distributions in Lake Ohrid are water depth and conductivity. In general, species richness, diversity and evenness were greater in waters <60 m deep, with highest values often found in the littoral zone, at depths <30 m. Candonids, however, displayed highest diversity in the sublittoral (30-50 m) and profundal (50-280 m) zones. The most frequent species encountered are taxa endemic to the lake (14 living species), which have a wide depth range (≤280 m), and display higher abundance with greater water depth. Non-endemic species were rare, limited to water depths <50 m, and were found mainly in the north part of the lake where anthropogenic pressure is high. Several cosmopolitan species were encountered for the first time, which suggests that these widespread species are new arrivals that may replace endemics as human impacts increase. © 2014 by the authors.
1543.
International Continental Scientific Drilling Programme Workshop on the Bushveld Complex
Geobulletin,
57
(4)
17--18
2014
1542.
In situ frictional properties of San Andreas Fault gouge at SAFOD
Geophysical Journal International,
199
(2)
956-967
2014
ISSN: 0956540X
Publisher: Oxford University Press
Keywords:▾
Creep; Geomechanics; Strain rate; Strike-slip faults, Constitutive parameters; Constitutive relations; Creep and deformations; Effective normal stress; Fault zone; Friction coefficients; Rate and state friction; Strain-rate strengthening effects, Friction, creep; deformation; displacement; fault gouge; fault zone; friction; geomechanics; rheology; San Andreas Fault, California; San Andreas; United States
Abstract: ▾ Along the central segment of the San Andreas Fault (SAF) near Parkfield, California, displacement occurs by a combination of aseismic creep and micro-earthquake slip. To constrain the strength and parametrize a constitutive relation for the creeping behaviour of the central segment of the SAF, we conducted friction experiments on clay-rich gouge retrieved by coring the Central Deforming Zone (CDZ) of the SAF at 2.7 km vertical depth. The gouge was flaked rather than powdered to preserve the natural scaly microfabric, and formed into 2-mm-thick layers that were sheared using a triaxial deformation apparatus. Experiments were conducted at in situ effective normal stress (100 MPa), pore pressure (25 MPa) and temperature (80-120 °C) conditions using brine pore fluid with the ionic composition of the in situ formation fluid. Velocity-stepping (0.006-0.6 μm s-1) and temperature-stepping experiments were conducted on brine-saturated gouge, and slide-hold-slide experiments were conducted on brine-saturated and room-dry gouge. Results are used to quantify the effects of rate, state, temperature and pore fluid on the strength of the CDZ gouge. We find that the gouge is extremely weak (μ < 0.13) and rate-strengthening, consistent with findings of previous studies on the CDZ gouge. We also find that, in a rate and state friction framework, slip history has a negligible effect on strength (b ≈ 0) under both saturated and dry conditions. The CDZ gouge is temperature-weakening from 80 to 120 °C and weakens 17 per cent when saturated with brine compared to room-dry conditions. Employing the laboratory-derived friction constitutive parameters, and including the temperature weakening and the strain-rate strengthening effects, we determine an approximate in situ friction coefficient of μ ≈ 0.11. For μ ≈ 0.11, aseismic creep under normal pore fluid conditions is permitted for angles up to 79° between the maximum horizontal stress and the plane of the SAF, consistent with nearby stress orientation measurements., Copy; The Authors 2014.
1541.
Incursion of meteoric waters into the ductile regime in an active orogen
Earth and Planetary Science Letters,
3991-13
2014
ISSN: 0012821X
Publisher: Elsevier
Keywords:▾
Digital storage; Flow of fluids; Hydrogen; Isotopes; Metamorphic rocks; Mineralogy; Oxygen; Quartz, Alpine Faults; Fluid inclusion; Meteoric waters; Southern Alps; Stable isotopes, Deformation
Abstract: ▾ Rapid tectonic uplift on the Alpine Fault, New Zealand, elevates topography, regional geothermal gradients, and the depth to the brittle ductile transition, and drives fluid flow that influences deformation and mineralisation within the orogen. Oxygen and hydrogen stable isotopes, fluid inclusion and Fourier Transform Infrared (FT-IR) analyses of quartz from veins which formed at a wide range of depths, temperatures and deformation regimes identify fluid sources and the depth of penetration of meteoric waters. Most veins formed under brittle conditions and with isotope signatures (δ18OH2O = -9.0 to +8.7‰VSMOW and δD = - 73 to - 45‰VSMOW) indicative of progressively rock-equilibrated meteoric waters. Two generations of quartz veins that post-date mylonitic foliation but endured further ductile deformation, and hence formation below the brittle to ductile transition zone (>6-8 km depth), preserve included hydrothermal fluids with δD values between -84 and -52‰, indicating formation from meteoric waters. FT-IR analyses of these veins show no evidence of structural hydrogen release, precluding this as a source of low δD values. In contrast, the oxygen isotopic signal of these fluids has almost completely equilibrated with host rocks (δ18OH2O = +2.3 to +8.7‰). These data show that meteoric waters dominate the fluid phase in the rocks, and there is no stable isotopic requirement for the presence of metamorphic fluids during the precipitation of ductilely deformed quartz veins. This requires the penetration during orogenesis of meteoric waters into and possibly below the brittle to ductile transition zone. © 2014 The Authors.
1540.
Influence of Methanogenic Populations in Holocene Lacustrine Sediments Revealed by Clone Libraries and Fatty Acid Biogeochemistry
Geomicrobiology Journal,
31
(4)
285 – 298
2014
1539.
Inorganic geochemistry data from Lake El'gygytgyn sediments: Marine isotope stages 6-11
Climate of the Past,
10
(2)
467-485
2014
ISSN: 18149324
Publisher: European Geosciences Union
Keywords:▾
chemical composition; concentration (composition); data set; drilling; environmental change; glacial deposit; glaciation; interglacial; lacustrine deposit; marine isotope stage; sediment chemistry; sedimentation, Chukchi; Elgygytgyn Lake; Lake Baikal; Russian Federation; Siberia
Abstract: ▾ Geochemical analyses were performed on sediments recovered by deep drilling at Lake El'gygytgyn in central Chukotka, northeastern Russia (67 30' N; 172 05' E). Major and rare element concentrations were determined using X-ray fluorescence spectroscopy (XRF) on the < 250 μm fraction from 617 samples dated to ca. 440 and 125 ka, which approximates marine isotope stages (MIS) 11 to 6. The inorganic geochemistry indicates significant variations in elemental composition between glaciations and interglaciations. Interglacial sediments are characterized by high contents of SiO2, Na2O, CaO, K 2O, and Sr and are depleted in Al2O3, Fe2O 3, TiO2, and MgO. An extreme SiO2 enrichment during MIS 11.3 and 9.3 was caused by an enhanced flux of biogenic silica (BSi). The geochemical structure of MIS 11 shows similar characteristics as seen in MIS 11 records from Lake Baikal (southeastern Siberia) and Antarctic ice cores, thereby arguing for the influence of global forcings on these records. High sediment content of TiO2, Fe2O3, MgO, Al 2O3, LOI, Ni, Cr, and Zr typifies glacial stages, with the most marked increases during MIS 7.4 and 6.6. Reducing conditions during glacial times are indicated by peaks in the Fe2O3 content and coinciding low Fe2O3/MnO ratios. This conclusion also is supported by P2O5 and MnO enrichment, indicating an increased abundance of authigenic, fine-grained vivianite. Elemental ratios (CIA, CIW, PIA, and Rb/Sr) indicate that glacial sediments are depleted in mobile elements, like Na, Ca, K and Sr. This depletion was caused by changes in the sedimentation regime and thus reflects environmental changes. © 2014 Author(s).
1538.
Inorganic geochemistry data from Lake El'gygytgyn sediments: marine isotope stages 6–11
Climate of the Past,
10
(2)
467-485
2014
1537.
Insights into early Earth from the Pt-Re-Os isotope and highly siderophile element abundance systematics of Barberton komatiites
Geochimica et Cosmochimica Acta,
125394 – 413
2014
1536.
Invaders versus endemics: alien gastropod species in ancient Lake Ohrid
Hydrobiologia,
739
(1)
163 – 174
2014
ISSN: 00188158
Publisher: Kluwer Academic Publishers
Keywords:▾
Lake Ohrid; Ferrissia fragilis; Ferrissia wautieri; Gastropoda; Physa acuta; coexistence; endemism; gastropod; identification key; introduced species; invasive species; lake ecosystem; phylogenetics; species diversity
Abstract: ▾ Species invasions into ancient lakes are an important but little understood phenomenon. At ancient Lake Ohrid, a systematic assessment of invasive mollusc species using morphological and genetic data was conducted from 2003 to 2012. Two globally invasive gastropod species, Physa acuta and Ferrissia fragilis, have recently been discovered at 4 out of 386 sites. These sites are anthropogenically impacted. The invasive species co-occur with endemics. Phylogenetic analyses of populations from native and invaded ranges of both species confirmed their identities and provided insights into their invasion histories. Accordingly, P. acuta is genetically more diverse than F. fragilis. Both species are currently present in a considerable number of lakes on the Balkan Peninsula. Possible future trends in Lake Ohrid and the Balkans are discussed and further spread of both species is likely. Given the ongoing environmental change in Lake Ohrid, the number of observations of non-indigenous or other widespread species will probably rise in the coming years and such species and their impact on native species should be carefully monitored. Moreover, ancient lakes with recurrent invasions of alien species might serve as interesting model systems for the study of important topics of invasion biology. © 2013, Springer Science+Business Media Dordrecht.
1535.
Impact of Lake-Level and Climate Changes on Microbial Communities in a Terrestrial Permafrost Sequence of the El'gygytgyn Crater, Far East Russian Arctic
Permafrost and Periglacial Processes,
25
(2)
107-116
2014
ISSN: 10456740
Publisher: John Wiley and Sons Ltd
DOI:10.1002/ppp.1807
Keywords:▾
abundance; arctic environment; biomarker; carbon cycle; climate change; Holocene; lake level; methane; microbial community; microbiology; microorganism; pedogenesis; permafrost; phospholipid; RNA; total organic carbon; Younger Dryas, Arctic; Chukchi; Elgygytgyn Lake; Russian Federation, Archaea; Bacteria (microorganisms)
Abstract: ▾ Microbial permafrost communities play an important role in carbon cycling and greenhouse gas fluxes. Despite the importance of these processes, there is a lack of knowledge about how environmental and climatic changes affect the abundance and composition of microorganisms. Here, we investigated the changing distribution of permafrost microorganisms in response to climate and lake-level changes. The permafrost core was drilled at the near shore of Lake El'gygytgyn, Far East Russian Arctic, and a combined microbiological and lipid biomarker approach was applied. The lower part of the permafrost core, deposited under subaquatic conditions, contains only small amounts of microbial signals; total organic carbon (TOC) content is sparse. After exposure of the site to subaerial conditions during the Allerød, the abundance of Bacteria and Archaea started to increase and the lake-level change is especially evidenced by the relative proportion of archaeal biomarkers. This increase is supported by rising bacterial and archaeal 16S ribosomal ribonucleic acid (rRNA) gene copy numbers and significant amounts of TOC during the late Allerød. After a small decrease during the colder Younger Dryas, the TOC content and the microbial signals strongly increase during the Holocene, presumably stimulated by pedogenesis. The occurrence of intact phospholipids indicates the presence of living microorganisms in these deposits. Our data suggest that methane formation is mainly expected for the subaerial interval, especially the Holocene where methanogens were identified by fingerprinting. This study emphasises the role of the uppermost permafrost deposits as a hotspot of carbon cycling in arctic environments, especially in the light of expected future global warming. © 2014 John Wiley & Sons, Ltd.
1534.
Investigating ultra high-enthalpy geothermal systems: A collaborative initiative to promote scientific opportunities
Scientific Drilling,
1835-42
2014
ISSN: 18168957
Publisher: Copernicus GmbH
Keywords:▾
Electric power generation; Enthalpy; Geothermal energy; Geothermal wells; Well drilling, Economic challenges; Economic feasibilities; Environmental footprints; Geothermal reservoir; Iceland deep drilling projects; Resource assessments; Science and Technology; Southern California, Geothermal fields
Abstract: ▾ Scientists, engineers, and policy makers gathered at a workshop in the San Bernardino Mountains of southern California in October 2013 to discuss the science and technology involved in developing high-enthalpy geothermal fields. A typical high-enthalpy geothermal well between 2000 and 3000m deep produces a mixture of hot water and steam at 200-300 °C that can be used to generate about 5-10MWe of electric power. The theme of the workshop was to explore the feasibility and economic potential of increasing the power output of geothermal wells by an order of magnitude by drilling deeper to reach much higher pressures and temperatures. Development of higher enthalpy geothermal systems for power production has obvious advantages; specifically higher temperatures yield higher power outputs per well so that fewer wells are needed, leading to smaller environmental footprints for a given size of power plant. Plans for resource assessment and drilling in such higher enthalpy areas are already underway in Iceland, New Zealand, and Japan. There is considerable potential for similar developments in other countries that already have a large production of electricity from geothermal steam, such as Mexico, the Philippines, Indonesia, Italy, and the USA. However drilling deeper involves technical and economic challenges. One approach to mitigating the cost issue is to form a consortium of industry, government and academia to share the costs and broaden the scope of investigation. An excellent example of such collaboration is the Iceland Deep Drilling Project (IDDP), which is investigating the economic feasibility of producing electricity from supercritical geothermal reservoirs, and this approach could serve as model for future developments elsewhere. A planning committee was formed to explore creating a similar initiative in the USA.
1533.
Joint Inversion of Body-Wave Arrival Times and Surface-Wave Dispersion for Three-Dimensional Seismic Structure Around SAFOD
Pure and Applied Geophysics,
171
(11)
3013-3022
2014
ISSN: 00334553
Publisher: Birkhauser Verlag AG
Keywords:▾
Economic and social effects; Seismic waves; Shear waves; Strike-slip faults; Surface waves; Wave propagation, Optimal solutions; Optimal weighting; Relative weights; S-wave velocity structure; San Andreas fault; Seismic structure; Surface wave data; Surface wave dispersion, Dispersion (waves), arrival time; body wave; inverse problem; P-wave; S-wave; San Andreas Fault; surface wave; three-dimensional modeling; velocity structure; wave dispersion
Abstract: ▾ We incorporate body-wave arrival time and surface-wave dispersion data into a joint inversion for three-dimensional P-wave and S-wave velocity structure of the crust surrounding the site of the San Andreas Fault Observatory at Depth. The contributions of the two data types to the inversion are controlled by the relative weighting of the respective equations. We find that the trade-off between fitting the two data types, controlled by the weighting, defines a clear optimal solution. Varying the weighting away from the optimal point leads to sharp increases in misfit for one data type with only modest reduction in misfit for the other data type. All the acceptable solutions yield structures with similar primary features, but the smaller-scale features change substantially. When there is a lower relative weight on the surface-wave data, it appears that the solution over-fits the body-wave data, leading to a relatively rough Vs model, whereas for the optimal weighting, we obtain a relatively smooth model that is able to fit both the body-wave and surface-wave observations adequately. © 2014, Springer Basel.
1532.
Lake level and climate records of the last 90ka from the Northern Basin of Lake Van, eastern Turkey
Quaternary Science Reviews,
10497-116
2014
ISSN: 02773791
Publisher: Elsevier Ltd
Keywords:▾
Climate record; ICDP PaleoVan; Lake levels; Lake vans; Multproxy analyses; Northern basins, authigenesis; climate variation; Dansgaard-Oeschger cycle; Holocene; interstadial; lake level; marine isotope stage; paleoclimate; precipitation (climatology); proxy climate record, Anatolia; Atlantic Ocean; Iran; Kordestan; Lake Urmia; Lake Van; Lake Zeribar; Levant; Mediterranean Region; Turkey
Abstract: ▾ Sedimentary, geochemical and mineralogical analyses of the ICDP cores recovered from the Northern Basin (NB) of Lake Van provide evidence of lake level and climatic changes related to orbital and North Atlantic climate system over the last 90ka. High lake levels are generally observed during the interglacial and interstadial periods, which are marked by deposition of varved sediments with high total organic carbon (TOC), total inorganic carbon (TIC), low detrital influx (high Ca/F) and high δ18O and δ13C values of authigenic carbonate. During the glacial and stadial periods of 71-58kaBP (Marine Isotope Stage 4, MIS4) and end of last glaciation-deglaciation (30-14.5kaBP; MIS3) relatively low lake levels prevailed, and grey homogeneous to faintly laminated clayey silts were deposited at high sedimentation and low organic productivity rates.Millennial-scale variability of the proxies during 60-30kaBP (MIS3 is correlated with the Dansgaard-Oeschger (D-O)) and Holocene abrupt climate events in the Atlantic. These events are characterized by laminated sediments, with high TOC, TIC, Ca/Fe, δ18O and δ13C values. The Lake Van NB records correlate well in the region with the climate records from the lakes Zeribar and Urmia in Iran and the Sofular Cave in NW Anatolia, but are in general in anti-phase to those from the Dead Sea Basin (Lake Lisan) in the Levant. The relatively higher δ18O values (0 to-0.4‰) for the interglacial and interstadial periods in the Lake Van NB section are due to the higher temperature and seasonality of precipitation and higher evaporation, whereas the lower values (-0.8 to-2‰) during the glacial and stadial periods are caused mainly by relative decrease in both temperature and seasonality of precipitation. The high δ18O values (up to 4.2‰) during the Younger Dryas, together with the presence of dolomite and low TOC contents, supports evaporative conditions and low lake level. A gradual decrease in the δ18O values from an average of-0.4‰ during the humid early Holocene to an average of-3.5‰ during the more arid late Holocene suggests an increasing contribution of winter precipitation. The changes in the seasonality of precipitation in eastern Anatolia are probably caused by changes in the temperatures of North Atlantic and Mediterranean and in the strength of Siberian High. © 2014 Elsevier Ltd.
1531.
Lake level and climate records of the last 90ka from the Northern Basin of Lake Van, eastern Turkey
Quaternary Science Reviews,
10497-116
2014
ISSN: 02773791
Publisher: Elsevier Ltd
Keywords:▾
Climate record; ICDP PaleoVan; Lake levels; Lake vans; Multproxy analyses; Northern basins, authigenesis; climate variation; Dansgaard-Oeschger cycle; Holocene; interstadial; lake level; marine isotope stage; paleoclimate; precipitation (climatology); proxy climate record, Anatolia; Atlantic Ocean; Iran; Kordestan; Lake Urmia; Lake Van; Lake Zeribar; Levant; Mediterranean Region; Turkey
Abstract: ▾ Sedimentary, geochemical and mineralogical analyses of the ICDP cores recovered from the Northern Basin (NB) of Lake Van provide evidence of lake level and climatic changes related to orbital and North Atlantic climate system over the last 90ka. High lake levels are generally observed during the interglacial and interstadial periods, which are marked by deposition of varved sediments with high total organic carbon (TOC), total inorganic carbon (TIC), low detrital influx (high Ca/F) and high δ18O and δ13C values of authigenic carbonate. During the glacial and stadial periods of 71-58kaBP (Marine Isotope Stage 4, MIS4) and end of last glaciation-deglaciation (30-14.5kaBP; MIS3) relatively low lake levels prevailed, and grey homogeneous to faintly laminated clayey silts were deposited at high sedimentation and low organic productivity rates.Millennial-scale variability of the proxies during 60-30kaBP (MIS3 is correlated with the Dansgaard-Oeschger (D-O)) and Holocene abrupt climate events in the Atlantic. These events are characterized by laminated sediments, with high TOC, TIC, Ca/Fe, δ18O and δ13C values. The Lake Van NB records correlate well in the region with the climate records from the lakes Zeribar and Urmia in Iran and the Sofular Cave in NW Anatolia, but are in general in anti-phase to those from the Dead Sea Basin (Lake Lisan) in the Levant. The relatively higher δ18O values (0 to-0.4‰) for the interglacial and interstadial periods in the Lake Van NB section are due to the higher temperature and seasonality of precipitation and higher evaporation, whereas the lower values (-0.8 to-2‰) during the glacial and stadial periods are caused mainly by relative decrease in both temperature and seasonality of precipitation. The high δ18O values (up to 4.2‰) during the Younger Dryas, together with the presence of dolomite and low TOC contents, supports evaporative conditions and low lake level. A gradual decrease in the δ18O values from an average of-0.4‰ during the humid early Holocene to an average of-3.5‰ during the more arid late Holocene suggests an increasing contribution of winter precipitation. The changes in the seasonality of precipitation in eastern Anatolia are probably caused by changes in the temperatures of North Atlantic and Mediterranean and in the strength of Siberian High. © 2014 Elsevier Ltd.
1530.
Drilling into magma and the implications of the Iceland Deep Drilling Project (IDDP) for high-temperature geothermal systems worldwide
Geothermics,
49111-118
2014
ISSN: 0375-6505Keywords:▾
Magma energy, Supercritical geothermal energy, Krafla Iceland
Abstract: ▾ Drilling deeper in high-temperature geothermal systems by the IDDP is aimed at increasing the power output of shallower high-temperature geothermal fields by an order of magnitude without increasing their environmental footprints. The main thrust of the IDDP is to develop deep supercritical systems, but an unexpected encounter with a shallow body of magma demonstrated that very high power outputs are also possible from the contact zone of an intrusion. In the future it may be feasible to produce energy directly from magma. Favorable environments to implement these concepts are likely worldwide wherever active volcanoes and young volcanic rocks occur.
1529.
Lake Van deep drilling project PALEOVAN
Quaternary Science Reviews,
1041-7
2014
ISSN: 02773791
Publisher: Elsevier Ltd
Keywords:▾
Deep drilling; Lake vans; Long continental record; Near East; Quaternary, deep drilling; lacustrine deposit; paleoclimate; Quaternary; sediment core; seismic survey; semiarid region, Lake Van; Turkey
Abstract: ▾ A complete succession of the lacustrine sediment sequence deposited during the last ~600,000 years in Lake Van, Eastern Anatolia (Turkey) was drilled in 2010 supported by the International Continental Scientific Drilling Program (ICDP). Based on a detailed seismic site survey, two sites at a water depth of up to 360m were drilled in summer 2010, and cores were retrieved from sub-lake-floor depths of 140m (Northern Basin) and 220m (Ahlat Ridge). To obtain a complete sedimentary section, the two sites were multiple cored in order to investigate the paleoclimate history of a sensitive semi-arid region between the Black, Caspian, and Mediterranean seas. This introductory paper provides background information of the deep drilling project and an overview of the studies presented in this special volume by the PALEOVAN science team dealing with chronology, paleomagnetism, paleoenvironmental proxies, geophysical and petrophysical investigations as well as pore-water and fluid transport. © 2014 Elsevier Ltd.
1528.
Impact of volcanism on the evolution of Lake Van (eastern Anatolia) III: Periodic (Nemrut) vs. episodic (Süphan) explosive eruptions and climate forcing reflected in a tephra gap between ca. 14 ka and ca. 30 ka
Journal of Volcanology and Geothermal Research,
285195-213
2014
ISSN: 03770273
Publisher: Elsevier
Keywords:▾
Explosive activity; Lake vans; Tephra swarm; Tephrostratigraphy; Volcanic activities, climate forcing; earthquake trigger; explosive volcanism; Holocene; late glacial; stratigraphy; tephra; volcanic eruption, Anatolia; Bitlis; Lake Van; Nemrut; Turkey
Abstract: ▾ Fifteen Lateglacial to Holocene rhyolitic, dominantly primary tephra layers piston-cored and drilled (ICDP Paleovan drilling project) in western Lake Van (eastern Anatolia, Turkey) were precisely correlated to either of the two adjacent and active large volcanoes Nemrut and Süphan based on shard textures, mineralogy and mineral and glass compositions. The young peralkaline (comenditic to pantelleritic) primary rhyolitic Nemrut tephras are characterized by anorthoclase, hedenbergitic to augitic clinopyroxene, fayalitic olivine, minor quartz, and rare accessory chevkinite and zircon. Phenocrysts in subalkaline primary rhyolitic Süphan tephras are chiefly oligoclase-labradorite, with minor K-rich sanidine in some, biotite, amphibole, hypersthene, rare augitic clinopyroxene, relatively common allanite and rare zircon.Two contrasting explosive eruptive modes are distinguished from each other: episodic (Süphan) and periodic (Nemrut). The Lateglacial Süphan tephra swarm covers a short time interval of ca. 338. years between ca. 13,078. vy BP and 12,740. vy BP, eruptions having occurred statistically every ca. 42. years with especially short intervals between V-11 (reworked) and V-14. Causes for the strongly episodic Süphan explosive behavior might include seismic triggering of a volcano-magma system unable to erupt explosively without the benefit of external triggering, as reflected in pervasive faulting preceding the Süphan tephra swarm. Seismic triggering may have caused the rise of more mafic ("trachyandesitic") parent magma, heating near-surface pockets of highly evolved magma - that might have formed silicic domes during this stage of volcano evolution - resulting in ascent and finally explosive fragmentation of magma essentially by external factors, probably significantly enhanced by magma-water/ice interaction.Explosive eruptions of the Nemrut volcano system, interpreted to be underlain by a large fractionating magma reservoir, follow a more periodic mode of (a) long-term relatively constant supply of parent magma, (b) evolution by low pressure crystal fractionation resulting in sporadic relatively low-volume eruption of trachytic and minor rhyolitic magmas, (c) evolution of a large magma reservoir to the point of highly explosive large-volume peralkaline rhyolitic Plinian eruptions at temporal intervals of ca. 20-40. ky, some accompanied by ignimbrites and inferred caldera collapse.A striking tephra gap between ca. 14. ka and ca. 30. ka, i.e. during glacial climate conditions, is postulated to be due to climate-forcing via lithosphere unloading following deglaciation. © 2014 Elsevier B.V.
1527.
Intra-continental earthquake swarms in West-Bohemia and Vogtland: A review
Tectonophysics,
6111 – 27
2014
ISSN: 00401951Keywords:▾
Bohemia; Cheb Basin; Czech Republic; Germany; Karlovarsky; Vogtland; Carbon dioxide; Degassing; Exploratory geochemistry; Fluids; Geodynamics; Isotopes; Complex fault system; Earthquake swarms; Earthquake triggering; High-pressure fluids; Isotopic signatures; Triggering mechanism; Vogtland; West Bohemia; carbon dioxide; degassing; earthquake hypocenter; earthquake swarm; earthquake trigger; geochemistry; geodynamics; seismic source; seismicity; seismotectonics; trigger mechanism; volcanism; Earthquakes
Abstract: ▾ Earthquake swarms and high CO2 flow of mantle origin are the characteristic features of West Bohemia/Vogtland (Central Europe). At present, the highest concentration of earthquake activity and CO2 degassing occurs in the area of the Cheb Basin at the intersection of the Eger Rift and Regensburg-Leipzig-Rostock Zone with three Quaternary active volcanoes. We review about 140 studies on structure, tectonics, volcanism, seismicity, earthquake source, triggering mechanisms, and gas-isotope geochemistry focused on the earthquake swarms from this area with the aim to build a complex image of the ongoing processes and find a possible link between activity of the mantle-derived fluids and the earthquake swarms. The so far unpublished data on the 2011 swarm and little known data on the 1824 swarm are presented, as well, showing that earthquake swarms activate a complex fault system and display long-term migration that differs from the occurrence of CO2 escapes. The activity of individual swarms is consistent with models involving high-pressure fluids; the isotopic signature of the rising gas proves its origin at depths below the hypocenters. We show that the earthquake swarms and degassing of CO2 of magmatic origin represent common result of the geodynamic activity of the area. Nevertheless, current knowledge does not preclude processes other than fluid-induced failure in triggering swarm seismicity. © 2013 Elsevier B.V.
1526.
IDDP—The chemistry of the IDDP-01 well fluids in relation to the geochemistry of the Krafla geothermal system
Geothermics,
4966-75
2014
ISSN: 0375-6505Keywords:▾
IDDP, Krafla, Geochemistry, Acid well fluids
Abstract: ▾ The Leirbotnar field, where IDDP-01 is situated consists of an upper liquid dominated zone to 1000–1400m depth, 190–220°C, sulphate major anion, and a lower two phase zone, 300°C chloride main anion. The IDDP-01 fluid is dry steam, local origin, pH 3. The major anion is chloride (20–166mg/kg), probably of magmatic origin. The major metallic cations, Fe (5–100mg/kg), Cr (0–6mg/kg), Ni (0–5mg/kg) and Mn (0.1–0.8mg/kg) seem to be derived from the well casing and sampling equipment. The gas content is low (about 0.1%) and the gas is apparently not directly emitted from magma.
1525.
Faulting processes in active faults - Evidences from TCDP and SAFOD drill core samples
Journal of Structural Geology,
65100-116
2014
ISSN: 01918141
Publisher: Elsevier Ltd
Keywords:▾
Chemical analysis; Deformation; Grinding (comminution); Microstructure; Minerals; Quartz; Seismology; Strike-slip faults; Tectonics, CPO; EBSD; Fault rock; SAFOD; TCDP, Structural geology, active fault; amorphous medium; calcite; clay mineral; crystal structure; crystallography; deformation; fault gouge; faulting; host rock; melting; microstructure; quartz; San Andreas Fault; slip rate
Abstract: ▾ The microstructures, mineralogy and chemistry of representative samples collected from the cores of the San Andreas Fault drill hole (SAFOD) and the Taiwan Chelungpu-Fault Drilling project (TCDP) have been studied using optical microscopy, TEM, SEM, XRD and XRF analyses. SAFOD samples provide a transect across undeformed host rock, the fault damage zone and currently active deforming zones of the San Andreas Fault. TCDP samples are retrieved from the principal slip zone (PSZ) and from the surrounding damage zone of the Chelungpu Fault. Substantial differences exist in the clay mineralogy of SAFOD and TCDP fault gouge samples. Amorphous material has been observed in SAFOD as well as TCDP samples. In line with previous publications, we propose that melt, observed in TCDP black gouge samples, was produced by seismic slip (melt origin) whereas amorphous material in SAFOD samples was formed by comminution of grains (crush origin) rather than by melting. Dauphiné twins in quartz grains of SAFOD and TCDP samples may indicate high seismic stress. The differences in the crystallographic preferred orientation of calcite between SAFOD and TCDP samples are significant. Microstructures resulting from dissolution-precipitation processes were observed in both faults but are more frequently found in SAFOD samples than in TCDP fault rocks. As already described for many other fault zones clay-gouge fabrics are quite weak in SAFOD and TCDP samples. Clay-clast aggregates (CCAs), proposed to indicate frictional heating and thermal pressurization, occur in material taken from the PSZ of the Chelungpu Fault, as well as within and outside of the SAFOD deforming zones, indicating that these microstructures were formed over a wide range of slip rates. © 2014 Elsevier Ltd.
1524.
Drilling of the well IDDP-1
Geothermics,
4923-30
2014
ISSN: 0375-6505Keywords:▾
Iceland Deep Drilling Project, Drilling, Magma, Superheat
Abstract: ▾ The first well of three proposed by the Iceland Deep Drilling Project (IDDP) was drilled in the Krafla Geothermal Field in 2008–2009 by Landsvirkjun, the National Power Company of Iceland. The well was designed to reach supercritical conditions at 4500m, temperatures above 374°C and pressures above 22MPa. Drilling progress was as planned down to around 2000m when drilling became quite challenging, including becoming stuck at 2094 and 2095m depth, followed by twist offs and subsequent side tracking. Finally, drilling came to an end at 2096m depth in the third leg when cuttings of fresh glass indicated the presence of a magma body at the bottom. As the well had such a rigorous well design, the steering committee of the IDDP decided to complete and flow test the well, rather than abandoning it. The well was very powerful and the project has proved to be a valuable experience for drilling supercritical wells in the future and what happens when magma is encountered. Most importantly, it has been proven that it is possible to drill and complete a well in a very hot zone and produce fluid from an environment near a magma body. If sustained long term production proves possible, the drilling of well IDDP-1 will mark a new era in power production in Krafla.
1523.
Iceland Deep Drilling Project: The first well, IDDP-1, drilled into magma
Geothermics,
491
2014
ISSN: 0375-65051522.
Dynamics of the last four glacial terminations recorded in Lake Van, Turkey
Quaternary Science Reviews,
10442-52
2014
ISSN: 02773791
Publisher: Elsevier Ltd
Keywords:▾
Carbonates; Glacial geology; Isotopes; Lithology; Mixing; Organic carbon; Rain; Snow melting systems, Eastern Mediterranean; Glacial/interglacial cycle; Lake vans; Multi proxies; Oxygen isotopes; Termination, Lakes, anoxia; carbonate; epilimnion; glacial environment; glacial-interglacial cycle; isotopic composition; lithology; numerical model; oxygen isotope; paleoclimate; proxy climate record; rainfall; runoff; snowmelt, Anatolia; Lake Van; Mediterranean Sea; Mediterranean Sea (East); Turkey
Abstract: ▾ A well-dated suite of Lake Van climate-proxy data covering the last 360ka documents environmental changes over 4 glacial/interglacial cycles in Eastern Anatolia, Turkey. The picture of cold and dry glacials and warm and wet interglacials emerging from pollen, organic carbon, authigenic carbonate content, elemental profiling by XRF and lithological analyses is inconsistent with classical interpretation of oxygen isotopic composition of carbonates pointing to a more complex pattern in Lake Van region. Detailed analysis of glacial terminations allows for the constraining of a depositional model explaining different patterns observed in all the proxies. We hypothesize that variations in relative contribution of rainfall, snowmelt and glacier meltwater recharging the basin have a very important role for all sedimentary processes in Lake Van. Lake level of glacial Lake Van, predominantly fed by snowmelt, was low, the water column was oxic, and carbonates precipitating in the epilimnion recorded the light isotopic signature of inflow. During terminations, increasing rainfall and significant supply of mountain glaciers' meltwater contributed to lake level rise. Increased rainfall enhanced density gradients in the water column, and hindered mixing leading to development of bottom-water anoxia. Carbonates precipitating during terminations show large fluctuations in their isotopic composition. Full interglacial conditions in Lake Van are characterized by high or slowly falling lake level. Rainfall and snowmelt feed the lake but due tore-established mixing, the isotopic composition of authigenic carbonates is heavier and closer to that of evaporation-influenced lake water than that of runoff representing snowmelt and atmospheric precipitation. © 2014 Elsevier Ltd.
1521.
Early Cenozoic tropical climate: Report from the Tanzania Onshore Paleogene Integrated Coring (TOPIC) workshop
Scientific Drilling,
1813-17
2014
ISSN: 18168957
Publisher: Copernicus GmbH
Keywords:▾
Drilling; Energy resources, Continental scientific drillings; Hemipelagic sediments; Paleoclimatic record; Petroleum development; Project development; Scientific drilling; Southern Tanzania; Tropical climates, Stratigraphy
Abstract: ▾ We are currently developing a proposal for a new International Continental Scientific Drilling Program (ICDP) project to recover a stratigraphic and paleoclimatic record from the full succession of Eocene hemipelagic sediments that are now exposed on land in southern Tanzania. Funding for a workshop was provided by ICDP, and the project was advertised in the normal way. A group of about 30 delegates assembled in Dar-es-Salaam for 3 intensive days of discussion, project development, and proposal writing. The event was hosted by the Tanzania Petroleum Development Corporation (TPDC) and was attended by several geologists, geochemists, geophysicists, and micropaleontologists from TPDC and the University of Dar-es-Salaam. International delegates were from Canada, Germany, India, Ireland, Italy, the Netherlands, United Kingdom, and United States (and we also have project partners from Australia, Belgium, and Sweden who were not able to attend). Some of the scientists are veterans of previous scientific drilling in the area, but over half are new on the scene, mostly having been attracted by Tanzania's reputation for world-class paleoclimate archives. Here we outline the broad aims of the proposed drilling and give a flavor of the discussions and the way our proposal developed during the workshop. A video of the workshop with an introduction to the scientific goals and interviews of many of the participants is available at http://vimeo.com/107911777.
1520.
Elemental composition of the Laguna Potrok Aike sediment sequence reveals paleoclimatic changes over the past 51 ka in southern Patagonia, Argentina
Journal of Paleolimnology,
52
(4)
349 – 366
2014
Abstract: ▾ During the lake deep drilling campaign PASADO in 2008, more than 500 m of lacustrine sediment was recovered from the maar lake Laguna Potrok Aike, Argentina. The major element composition was assessed at high resolution with an ITRAX X-ray fluorescence core scanner. The sharp boundary between a carbonate-bearing and a carbonate-free depositional system occurs at 13.5 cal. ka BP and marks the transition from glacial to Late Glacial sediments. Holocene and Late Glacial sediments can be distinguished by elements that are indicative of organic matter (Br, Cl) or calcite (Ca). Glacial sediments are characterized by elements that represent terrigenous clastic input (Fe, Ti, K, Si). Trace elements (Mn, Rb, V, Ni) accumulate with the bulk of lithogenic elements indicating frequent oxic conditions and rare diagenetic remobilization. Based on principal component analysis we interpret the scores of the first principle component as a summarizing indicator for climate-related variations of depositional conditions. During the Holocene climate changes mirror the total inorganic carbon profile, which was used as a proxy for lake-level reconstructions of the past 16 ka in previous studies. High scores in the first principle component probably reflect periods of increased chemical over mechanical weathering and developing soils and vegetation cover limiting sediment availability for erosional processes. These intervals often also show increases in total organic carbon values and total organic carbon/total nitrogen ratios, which are associated with periods of Antarctic warming in the last glacial. Geochemical variations of the clastic glacial sediments are explored by excluding carbonate-bearing sediments from principal component analysis. Although, in this lake, Ca is a purely clastic signal in carbonate-free sediments, it does not correlate with the bulk of indicators for terrigenous input. Instead Ca dominates a second principal component together with Sr. This component mainly distinguishes coarse grained layers from the remaining sediment. The main provenance of this coarse-grained material is suggested to be a basalt outcrop at the western shore. Low lake levels, high waves and flash-flood events may have increased the availability of basaltic sand during extremely cold, arid and windy conditions. High wind speeds and lack of vegetation may have facilitated the increased transport of coarse-grained material into the center of Laguna Potrok Aike. Decreases in the second principal component can be observed during Oxygen Isotope Stage 2 when increased dust input has been found in cores from Laguna Potrok Aike, the Southern Ocean and Antarctica. © 2014, Springer Science+Business Media Dordrecht.