All ICDP Publications with Abstracts
From parent-sysfolder "Publications" + 2 folder-levels deep
719.
Storage conditions and evolution of andesitic magma prior to the 1991-95 eruption of Unzen volcano: Constraints from natural samples and phase equilibria experiments
Journal of Volcanology and Geothermal Research,
175
(1-2)
168-180
2008
ISSN: 03770273Keywords:▾
Chemical engineering; Feldspar; Landforms; Silicate minerals; Silicon compounds; Volcanic rocks; Volcanoes, andesite; experiment; magma mixing; melt inclusions; storage conditions; Unzen volcano; volatiles, Phase equilibria, andesite; clinopyroxene; magma; magnetite; melt inclusion; phase equilibrium; volatile element; volcanic eruption, Asia; Eurasia; Far East; Japan; Kyushu; Nagasaki [Kyushu]; Unzen Volcano
Abstract: ▾ The compositions of homogenized melt inclusions trapped in plagioclase (Pl) microphenocrysts (40-200 μm length) from mafic enclaves within dacitic rocks erupted at Unzen volcano in 1991-95 were investigated. The SiO2 contents of the melt inclusions vary from 58 to 70 wt.% and Pl anorthite content is An50-70. The stability fields (in terms of temperature and water activity) of natural Pl and coexisting melts from the melt inclusions were estimated from data of phase equilibria experiments performed with a synthetic andesite composition at T = 900-1140 °C, P = 200 MPa, log fO2 = NNO-2-NNO, and water activity of about 0-1. This composition is representative of the average composition of mafic enclaves from the 1991-95 eruption and nearly identical to the composition of andesitic lavas from 1663 Unzen eruption. The temperatures and H2O melt concentrations, calculated using the compositions of coexisting Pl and melt inclusions, provide an estimation of the conditions of andesitic magma evolution within the mafic enclaves prior to eruption. The formation of melt inclusions in plagioclase microphenocrysts occurred at a maximum temperature of ~ 1010 ± 35 °C for a melt containing 2 wt.% H2O and a minimum temperature of ∼ 945 °C ± 30 °C for a melt with ∼ 4 wt.% dissolved H2O. The compositional range of the melt inclusions indicates that the composition of the mafic enclave was not significantly contaminated by the host magma when inclusions were formed. The difference between concentrations of dissolved S (up to 0.06 wt.%) and Cl (up to 0.05 wt.%) in melt inclusions in Pl of mafic enclaves and concentrations of S (< 0.005 wt.%) and Cl (0.05-0.11 wt.%) in melt inclusions in phenocrysts of the dacitic magma clearly implies that two distinct sources for S and Cl in the 1991-95 eruption of Unzen volcano need to be considered. Sulfur degassing was generated by a release of fluids from the high-temperature andesitic magma whereas Cl was degassed from the low-temperature silicic magma. The combination of data from melt inclusions and phase equilibria experiments indicates that the mafic end-member magma at Unzen was already partially crystallized and contained significant proportions (20 to 40 wt.%) of Pl and orthopyroxene (Opx) when melt inclusions started to form. Since clinopyroxene (Cpx) and magnetite (Mt) crystallize after Pl and Opx, the temperatures derived for the mafic end-member magma from coexisting Opx-Cpx and Ilm-Mt pairs do not represent temperatures near to the liquidus. Assuming that the injected mafic magma was nearly aphyric, its initial temperature might have been higher than estimated in previous studies. © 2008 Elsevier B.V. All rights reserved.
718.
Stability analysis of Hawaiian Island flanks using insight gained from strength testing of the HSDP core
Journal of Volcanology and Geothermal Research,
171
(3-4)
163-177
2008
ISSN: 03770273Keywords:▾
Failure analysis; Landslides; Lithology; Sensitivity analysis; Volcanic rocks, Digital elevation models; Edifice stability; Hawaiian Island flank failures; Volcanic slope stability, Volcanoes, collapse; core logging; digital elevation model; failure analysis; limit analysis; rock mass classification; sensitivity analysis; slope stability; stability analysis; strength; testing method, Hawaiian Islands; Pacific islands; Pacific Ocean
Abstract: ▾ Hawaiian Island flank failures are recognized as the largest landslide events on Earth, reaching volumes of several thousand cubic kilometers and lengths of over 200 km and occurring on an average of once every 100 000 years. The 3.1 km deep Hawaii Scientific Drilling Project (HSDP) enabled an investigation of the rock mass strength variations on the island of Hawaii [Schiffman, P., Watters, R.J., Thompson, N., Walton, A.W., 2006. Hyaloclastites and the slope stability of Hawaiian volcanoes: insights from the Hawaiian Scientific Drilling Project's 3-km drill core. Journal of Volcanology and Geothermal Research, 151 (1-3): 217-228]. This study builds on that of Schiffman et al. [Schiffman, P., Watters, R.J., Thompson, N., Walton, A.W., 2006. Hyaloclastites and the slope stability of Hawaiian volcanoes: Insights from the Hawaiian Scientific Drilling Project's 3-km drill core. Journal of Volcanology and Geothermal Research, 151 (1-3): 217-228] by considering more in-depth rock mass classification and strength testing methods of the HSDP core. Geotechnical core logging techniques combined with laboratory strength testing methods show that rock strength differences exist within the edifice. Comparing the rock strength parameters obtained from the various volcano lithologies identified weak zones, suggesting the possible location of future slip surfaces for large flank failures. Relatively weak rock layers were recognized within poorly consolidated hyaloclastite zones, with increases in strength based on degree of alteration. Subaerial and submarine basalt flows are found to be significantly stronger. With the aid of digital elevation models, cross-sections have been developed of key flank areas on the island of Hawaii. Limit equilibrium slope stability analyses are performed on each cross-section using various failure criteria for the rock mass strength calculations. Based on the stability analyses the majority of the slopes analyzed are considered stable. In cases where instability (i.e. failure) is predicted, decreased rock mass quality (strength) of the altered and highly poorly consolidated lithologies is found to have a significant influence. These lithologies are present throughout the Hawaiian Islands, representing potential failure surfaces for large flank collapses. Failure criterion input parameters are considered in sensitivity analyses as are the influences of certain external stability factors such as sea level variation and seismic loading. © 2007 Elsevier B.V. All rights reserved.
717.
Periglacial sediment variations controlled by late Quaternary climate and lake level change at Elgygytgyn Crater, Arctic Siberia
Boreas,
37
(1)
55-65
2008
ISSN: 03009483Keywords:▾
climate change; glacial deposit; highstand; lake level; paleoenvironment; paleohydrology; Quaternary; sedimentation rate; weathering, Chukchi; Elgygytgyn Lake; Eurasia; Russian Federation; Siberia
Abstract: ▾ Late Quaternary sediments in a permafrost environment recovered from the Elgygytgyn Impact Crater were studied to determine regional palaeoenvironmental variability and infer past water-level changes of the crater lake. Stratigraphic analysis of a 5m long permafrost core is based on various lithological (grain size, total organic carbon, magnetic susceptibility) and hydrochemical (oxygen isotope composition, major cation content) properties and pore ice content. The results show that alluvial sediments accumulated on top of cryogenically weathered volcanic rock. Changes in the hydrochemical properties reflect different stages of cryogenic weathering. The lithological characteristics mark the transition from an erosive site to a site with accumulation. This environmental change is linked to a relative lake level highstand at >13 000 yr BP, when a shoreline bar was formed leading to slope sedimentation. Lake level dropped by 4m during the Holocene. © 2007 The Authors, Journal compilation © 2007 The Boreas Collegium.
716.
Preseismic velocity changes observed from active source monitoring at the Parkfield SAFOD drill site
Nature,
454
(7201)
204-208
2008
ISSN: 00280836
Publisher: Nature Publishing Group
Keywords:▾
crack; earthquake; fault zone; measurement method; monitoring; rupture; seismic velocity; seismic wave, article; earthquake; environmental monitoring; measurement; pressure; priority journal; rock; stress, California; North America; San Andreas; San Andreas Fault Zone; United States
Abstract: ▾ Measuring stress changes within seismically active fault zones has been a long-sought goal of seismology. One approach is to exploit the stress dependence of seismic wave velocity, and we have investigated this in an active source cross-well experiment at the San Andreas Fault Observatory at Depth (SAFOD) drill site. Here we show that stress changes are indeed measurable using this technique. Over a two-month period, we observed an excellent anti-correlation between changes in the time required for a shear wave to travel through the rock along a fixed pathway (a few microseconds) and variations in barometric pressure. We also observed two large excursions in the travel-time data that are coincident with two earthquakes that are among those predicted to produce the largest coseismic stress changes at SAFOD. The two excursions started approximately 10 and 2 hours before the events, respectively, suggesting that they may be related to pre-rupture stress induced changes in crack properties, as observed in early laboratory studies. ©2008 Macmillan Publishers Limited. All rights reserved.
715.
Paleomagnetic reorientation of San Andreas Fault Observatory at Depth (SAFOD) core
Geophysical Research Letters,
35
(2)
2008
ISSN: 00948276Keywords:▾
Boreholes; Demagnetization; Magnetic fields; Magnetization; Sandstone; Tectonics, Fine-grained sandstones; Paleomagnetic analysis; Paleomagnetic reorientation, Geomagnetism, borehole; Cretaceous; demagnetization; paleomagnetism; remanent magnetization; San Andreas Fault, California; Central Valley [California]; North America; United States
Abstract: ▾ We present a protocol for using paleomagnetic analysis to determine the absolute orientation of core recovered from the SAFOD borehole. Our approach is based on determining the direction of the primary remanent magnetization of a spot core recovered from the Great Valley Sequence during SAFOD Phase 2 and comparing its direction to the expected reference field direction for the Late Cretaceous in North America. Both thermal and alternating field demagnetization provide equally resolved magnetization, possibly residing in magnetite, that allow reorientation. Because compositionally similar siltstones and fine-grained sandstones were encountered in the San Andreas Fault Zone during Stage 2 rotary drilling, we expect that paleomagnetic reorientation will yield reliable core orientations for continuous core acquired from directly within and adjacent to the San Andreas Fault during SAFOD Phase 3, which will be key to interpretation of spatial properties of these rocks. Copyright 2008 by the American Geophysical Union.
714.
Concurrent evolution of ancient sister lakes and sister species: The freshwater gastropod genus Radix in lakes Ohrid and Prespa
Hydrobiologia,
615
(1)
157 – 167
2008
ISSN: 15735117Keywords:▾
Eurasia; Europe; Lake Mikri Prespa; Lake Ohrid; Southern Europe; Gastropoda; Radix (gastropod); Radix ampla; Radix auricularia; Radix sp.; Biodiversity; Nucleic acids; Organic acids; biodiversity; DNA; endemic species; evolution; freshwater ecosystem; gastropod; lake; phylogenetics; taxonomy; Ancient lake; Balkan; Lake Ohrid; Lake Prespa; Radix; Sister lakes; Lakes
Abstract: ▾ Ancient sister lakes are considered to be ancient lakes lying in close geographic proximity, sharing a related origin and significant time of co-existence, usually having hydrological connection as well as a balanced degree of faunal overlap and distinctness. A paradigm for studying sister lake relationships are the ancient lakes Ohrid and Prespa in the Balkans, which are characterized by high degrees of endemicity. Three general patterns of endemic species can be distinguished for these lakes: (1) taxa that are endemic to either lake, with no close relatives in the respective sister lake, (2) closely related but distinct endemic taxa in both lakes (sister species) and (3) shared endemic taxa occurring in both lakes. In the present paper, two endemic freshwater pulmonate gastropod species, Radix relicta (Lake Ohrid) and R. pinteri (Lake Prespa), are used to study the evolution of presumed sister species based on biogeographical and comparative DNA data from world-wide Radix taxa. Phylogenetic, phylogeographical and parametric bootstrap analyses all suggest a sister group relationship of R. relicta and R. pinteri (pattern 2 of endemic diversity). Sister to these two taxa is the widespread R. ampla, which does not occur in the vicinity of lakes Ohrid and Prespa. The southern feeder spring complexes of Lake Ohrid are inhabited by another lineage (Radix sp. 1), which resembles Radix relicta in morphology/anatomy. For Lake Prespa, the widespread R. auricularia was reported in addition to the endemic R. pinteri. Comparative phylogenetic data favour a western Adriatic zoogeographical affinity of lakes Ohrid and Prespa over an Aegean-Anatolian faunal connection. The status of lakes Ohrid and Prespa as sister lakes is evaluated in the light of current knowledge on gastropod speciation and endemism in these hotspots of biodiversity. © 2008 Springer Science+Business Media B.V.
713.
Drilling fluid technology in the core drilling of SLCORE-I well (main well) (in Chinese with English abstract);[松科1井(主井)取心钻进钻井液技术]
Coal Geology & Exploration,
36
(6)
77-80
2008
712.
Drilling and logging results of USDP-4 - Penetration into the volcanic conduit of Unzen Volcano, Japan
Journal of Volcanology and Geothermal Research,
175
(1-2)
1-12
2008
ISSN: 03770273Keywords:▾
Acoustic logging; Core drilling; Drilling; Forestry; Gamma rays; Geophysics; Harvesting; Ionizing radiation; Landforms; Logging (forestry); Neutron logging; Oceanography; Offshore oil wells; Rock drilling; Sea level; Volcanic rocks; Volcanoes; Water levels, Bore hole; Chemical-; Deviation angles; Drilling operations; extended reach borehole; Geophysical logging; High temperature; Neutron porosity; Research programs; scientific drilling; Self-potential; Sonic velocity; spot coring; Surface mechanism; tough logging; volcanic conduit; Volcanic conduits, Boreholes, borehole logging; chemical analysis; dike; geophysical survey; volcanic eruption, Drilling; Forestry; Gamma Rays; Harvesting; Ionizing Radiation; Logging; Oceanography; Volcanism; Water, Asia; Eurasia; Far East; Japan; Kyushu; Nagasaki [Kyushu]; Unzen Volcano
Abstract: ▾ Borehole USDP-4 was drilled into the Unzen volcanic conduit 9 years after its last eruption. The sub-surface mechanism of eruption at Unzen Volcano was investigated by taking cores and by geophysical logging. The drilling operations were carried out in 2003-04, as a joint research program sponsored by the Japanese Government and the International Continental Scientific Drilling Program (ICDP). Borehole USDP-4 was a directional 6-1/4 in. (158.8 mm) borehole drilled from a site located on the northern slope of the volcano at 840 m above sea level, and was designed to penetrate into the conduit at sea level with a final deviation angle of over 70° from vertical and a borehole depth of 1800 m. An igneous dyke with a high likelihood of being the Unzen conduit was encountered at 1996 m depth and core samples were taken from that location. Chemical analysis of drill cores confirmed the identification of the conduit. Geophysical logging, including recording of gamma ray, resistivity, self-potential, density, neutron porosity, sonic velocity, and temperature suggested an alternation of dykes and flows in rock penetrated during the drilling, and in-hole pictures confirmed the lithologic identifications. Although borehole collapse and high temperature had been expected in the conduit, the actual drilling and logging into the conduit experienced no gas or fluid kick, and the measured temperatures within the dyke were below 200 °C. © 2008 Elsevier B.V. All rights reserved.
711.
Drill bit noise illuminates the san andreas fault
Eos,
89
(38)
349
2008
ISSN: 00963941
Publisher: Blackwell Publishing Ltd
Keywords:▾
drill bit; fault; noise; San Andreas Fault, California; North America; San Andreas; United States
710.
Deep drilling into the Chesapeake Bay impact structure
Science,
320
(5884)
1740-1745
2008
Abstract: ▾ Samples from a 1.76-kilometer-deep corehole drilled near the center of the late Eocene Chesapeake Bay impact structure (Virginia, USA) reveal its geologic, hydrologic, and biologic history. We conducted stratigraphic and petrologic analyses of the cores to elucidate the timing and results of impact-melt creation and distribution, transient-cavity collapse, and ocean-water resurge. Comparison of post-impact sedimentary sequences inside and outside the structure indicates that compaction of the crater fill influenced long-term sedimentation patterns in the mid-Atlantic region. Salty connate water of the target remains in the crater fill today, where it poses a potential threat to the regional groundwater resource. Observed depth variations in microbial abundance indicate a complex history of impact-related thermal sterilization and habitat modification, and subsequent post-impact repopulation.
709.
Deep drilling into the Chesapeake Bay impact structure
Science,
320
(5884)
1740-1745
2008
ISSN: 00368075Keywords:▾
sea water, abundance; deep drilling; Eocene; groundwater resource; impact structure; petrology; sedimentary sequence; sedimentation; stratigraphy, article; asthenospheric upwelling; biosphere; controlled study; Cretaceous; drill; hydrology; instrument sterilization; microbial growth; nonhuman; petrology; priority journal; sedimentation; stratigraphy; terrestrial surface waters, Bacteria; Ecosystem; Geologic Sediments; Heat; Salinity; Seawater; Time; Virginia, Chesapeake Bay; North America; United States; Virginia
Abstract: ▾ Samples from a 1.76-kilometer-deep corehole drilled near the center of the late Eocene Chesapeake Bay impact structure (Virginia, USA) reveal its geologic, hydrologic, and biologic history. We conducted stratigraphic and petrologic analyses of the cores to elucidate the timing and results of impact-melt creation and distribution, transient-cavity collapse, and ocean-water resurge. Comparison of post-impact sedimentary sequences inside and outside the structure indicates that compaction of the crater fill influenced long-term sedimentation patterns in the mid-Atlantic region. Salty connate water of the target remains in the crater fill today, where it poses a potential threat to the regional groundwater resource. Observed depth variations in microbial abundance indicate a complex history of impact-related thermal sterilization and habitat modification, and subsequent post-impact repopulation.
708.
CPCP: Colorado Plateau Coring Project - 100 million years of early Mesozoic climatic, tectonic, and biotic evolution of an epicontinental basin complex
Scientific Drilling
(6)
62-66
2008
ISSN: 18168957707.
Coseismic fluid-rock interactions at high temperatures in the Chelungpu fault
Nature Geoscience,
1
(10)
679-683
2008
ISSN: 17520894
Publisher: Nature Publishing Group
DOI:10.1038/ngeo308
Abstract: ▾ Aqueous fluids are thought to have an essential role in faulting and the dynamic propagation of earthquake rupture. Fluid overpressure can affect earthquake nucleation and in a process termed thermal pressurization, pore fluid pressure produced by frictional heating can reduce the effective normal stress acting on the fault surface. This may lead to a marked reduction in fault strength during slip. However, the coseismic presence of fluids within slip zones and the role of fluids in dynamic fault weakening is still a matter of debate. Here we present compositions of major and trace elements as well as isotope ratios of core samples representing relatively undamaged as well as very fine-grained deformed material from three active zones of the Chelungpu fault, Taiwan. Depth profiles across the most intensely sheared bands that range in thickness from 2-15 cm exhibit sharp compositional peaks of fluid-mobile elements and of strontium isotopes. We suggest that high-temperature fluids (>350 C) derived from heating of sediment pore fluids during the earthquake interacted with material within the fault zone and mobilized the elements. The coseismic presence of high-temperature fluids under conditions of low hydraulic diffusivity within the fault zone is favourable for thermal pressurization. This effect may have caused a dynamic decrease of friction along the Chelungpu fault during the 1999 magnitude 7.6 Chi-Chi earthquake. © 2008 Macmillan Publishers Limited.
706.
Corrigendum to "Quaternary glaciation and hydrologic variation in the South American tropics as reconstructed from the Lake Titicaca drilling project" [Quaternary Research 68 (2007) 410-420] (DOI:10.1016/j.yqres.2007.07.008)
Quaternary Research,
69
(2)
342
2008
705.
Coring Drilling technology in Well-1 (main shaft) of Songliao scientific drilling
Exploration Engineering (Rock & Soil Drilling and Tunneling),
35
(9)
1-5
2008
704.
Core-log integration studies in hole-A of Taiwan Chelungpu-fault Drilling Project
Geophysical Journal International,
174
(3)
949-965
2008
ISSN: 0956540XKeywords:▾
azimuth; Chi-Chi earthquake 1999; displacement; earthquake mechanism; fault zone; S-wave; seismic anisotropy; seismicity; shear zone, Asia; Eurasia; Far East; Taiwan
Abstract: ▾ Taiwan Chelungpu-fault Drilling Project (TCDP) was initiated to understand the physical mechanisms involved in the large displacements of the 1999 Taiwan Chi-Chi earthquake. Continuous measurements of cores (including laboratory work) and a suite of geophysical downhole logs, including P- and S-wave sonic velocity, gamma ray, electrical resistivity, density, temperature, electrical borehole images and dipole-shear sonic imager, were acquired in Hole-A over the depth of 500-2003 m. Integrated studies of cores and logs facilitate qualitative and quantitative comparison of subsurface structures and physical properties of rocks. A total of 10 subunits were divided on the basis of geophysical characteristics. Generally, formation velocity and temperature increase with depth as a result of the overburden and thermal gradient, respectively. Gamma ray, resistivity, formation density, shear velocity anisotropy and density-derived porosity are primarily dependent on the lithology. Zones with changes of percentage of shear wave anisotropy and the fast shear polarization azimuth deduced from Dipole Shear-Imager (DSI) are associated with the appearance of fractures, steep bedding and shear zones. The fast shear wave azimuth is in good agreement with overall dip of the bedding (approximately 30° towards SE) and maximum horizontal compressional direction, particularly in the Kueichulin Formation showing strong shear wave velocity anisotropy. Bedding-parallel fractures are prevalent within cores, whereas minor sets of high-angle, NNW-SSE trending with N- and S-dipping fractures are sporadically distributed. The fault zone at depth 1111 m (FZA1111) is the Chi-Chi earthquake slip zone and could be a fluid conduit after the earthquake. The drastic change in fast shear wave polarization direction across the underlying, non-active Sanyi thrust at depth 1710 m reflects changes in stratigraphy, physical properties and structural geometry. © 2008 The Authors Journal compilation © 2008 RAS.
703.
Comparison of eruptive and intrusive samples from Unzen Volcano, Japan: Effects of contrasting pressure-temperature-time paths
Journal of Volcanology and Geothermal Research,
175
(1-2)
60-70
2008
ISSN: 03770273Keywords:▾
Calcite; Carbonate minerals; Clay minerals; Cooling; Crystallography; Dewatering; Drilling; Feldspar; Heating; Landforms; Lithology; Metallic glass; Mica; Mineralogy; Minerals; Ore deposit geology; Oxide minerals; Physical chemistry; Product development; Pyrites; Quartz; Rate constants; Silicate minerals; Sodium; Sulfate minerals; Textures; Trace elements; Volcanic rocks; Volcanoes, Analytical uncertainties; Bulk compositions; Chemical-; Confining pressures; crystallization texture; decompression experiments; Element concentrations; Equilibrium value; Hydrothermal alterations; Low temperature; Magmatic water; Melt phase; phase equilibria; Physical characteristics; Plutonic suites; Pressure-temperature-time paths; Rapid rate; Rhyolitic; Scientific results; Sericite; Subsolidus; System effects; Time span; Unzen; vesicularity, Cooling water, confining pressure; drilling; emplacement; hydrothermal alteration; igneous intrusion; lava; magmatic differentiation; phase equilibrium; trace element; volcanic eruption, Asia; Eurasia; Far East; Japan; Kyushu; Nagasaki [Kyushu]; Unzen Volcano
Abstract: ▾ Core samples from the conduit of Unzen Volcano, obtained only 9 years after cessation of the 1991-1995 eruption, exhibit important differences in physical characteristics and mineralogy, and subtle differences in bulk chemistry from erupted samples. These differences in the conduit samples reflect emplacement under a confining pressure where about half of the original magmatic water was retained in the melt phase, maintenance at hypersolidus temperature for some unknown but significant time span, and subsequent subsolidus hydrothermal alteration. In contrast, magma that extruded as lava underwent decompression to 1 atm with nearly complete loss of magmatic water and cooling at a sufficiently rapid rate to produce glass. The resulting hypabyssal texture of the conduit samples, while clearly distinct from eruptive rocks, is also distinct from plutonic suites. Given the already low temperature of the conduit (less than 200 °C, [Nakada, S., Uto, K., Yoshimoto, M., Eichelberger, J.C., Shimizu, H., 2005. Scientific Results of Conduit Drilling in the Unzen Scientific Drilling Project (USDP), Sci. Drill., 1, 18-22]) when it was sampled by drilling, this texture must have developed within a decade, and perhaps within a much shorter time, after emplacement. The fact that all trace-element concentrations of the conduit and the last-emplaced lava of the spine, 1300 m above it, are identical to within analytical uncertainty provides strong evidence that both were produced during the same eruption sequence. Changes in conduit magma that occurred between emplacement and cooling to the solidus were collapse of vesicles from less than or equal to the equilibrium value of about 50 vol.% to about 0.1 vol.%; continued resorption of quartz and reaction of biotite phenocrysts due to heating of magma prior to ascent by intruding mafic magma; breakdown of hornblende; and micro-crystallization of rhyolitic melt to feldspar and quartz. Subsolidus changes were deposition of calcite and pyrite, growth of sericite in anorthite-rich zones of plagioclase, and development of montmorillonite as an alteration product. Significant changes in bulk composition were depletion of Mg, Fe and Na and enrichment in C and S. These changes were due mainly to the breakdown of hornblende and plagioclase, and addition of carbonate and pyrite, respectively. The identical concentrations of REEs in the conduit and surface lava are consistent with low water to rock ratios during alteration. This suggests to us that despite convective hydrothermal removal of heat from the conduit, chemical open-system effects were limited to early loss of magmatic water and later addition of magmatic CO2 and SO2 and/or H2S streaming up the conduit from deeper levels. © 2008 Elsevier B.V.
702.
Dry bulk density and water content of piston core CON01-605-3 from Vydrino
701.
Comment on the paper "Chicxulub impact predates K-T boundary: New evidence from Brazos, Texas" by Keller et al. (2007)
Earth and Planetary Science Letters,
269
(3-4)
614-620
2008
700.
Climatic, Tectonic, and Biotic Evolution in Continental Cores: Colorado Plateau Coring Project Workshop; St. George, Utah, 13–16 November 2007
Eos, Transactions American Geophysical Union,
89
(12)
118-118
2008
Abstract: ▾ A workshop was convened in St. George, Utah, to advance planning for the Colorado Plateau Coring Project (CPCP). The vast continental basins of the southwestern United States, particularly well exposed on the Colorado Plateau and its environs, contain one of the richest stratigraphic records of early Mesozoic age (between roughly 145 and 250 million years ago). This time period was punctuated by two of the major mass extinctions in the past 550 million years and witnessed the evolutionary appearance of the modern biota and dramatic climate changes on the continents. Since the mid-nineteenth century, classic studies of these basins, their strata, and their fossils have made this sequence instrumental in framing our context for the early Mesozoic world. Nonetheless, striking ambiguities in temporal resolution, uncertainties in global correlations with other early Mesozoic strata, and major doubts about latitudinal position still hamper testing of the major competing climatic, biotic, and tectonic hypotheses.
699.
Biot-type scattering effects in gas hydrate-bearing sediments
Journal of Geophysical Research: Solid Earth,
113
(6)
2008
ISSN: 21699313
Publisher: Blackwell Publishing Ltd
Keywords:▾
Biot theory; experimental study; gas hydrate; heterogeneous medium; numerical model; porous medium; single-phase flow; wave attenuation; wave propagation; wavelength
Abstract: ▾ This paper studies the energy conversions that take place at discontinuities within gas hydrate-bearing sediments and their influence on the attenuation of waves traveling through these media. The analysis is based on a theory recently developed by some of the authors, to describe wave propagation in multiphasic porous media composed of two solids saturated by a single-phase fluid. Real data from the Mallik 5L-38 Gas Hydrate Research well are used to calibrate the physical model, allowing to obtain information about the characteristics of the cementation between the mineral grains and gas hydrates for this well. Numerical experiments show that, besides energy conversions to reflected and transmitted classical waves, significant fractions of the energy of propagating waves may be converted into slow-waves energy at plane heterogeneities within hydrated sediments. Moreover, numerical simulations of wave propagation show that very high levels of attenuation can take place in the presence of heterogeneous media composed of zones with low and high gas hydrate saturations with sizes smaller or on the order of the wavelengths of the fast waves at sonic frequencies. These attenuation levels are in very good agreement with those measured at the Mallik 5L-38 Gas Hydrate Research Well, suggesting that these scattering-type effects may be a key-parameter to understand the high sonic attenuation observed at gas hydrate-bearing sediments. Copyright 2008 by the American Geophysical Union.
698.
Assembly and concept of a web-based GIS within the paleolimnological project CONTINENT (Lake Baikal, Russia)
Journal of Paleolimnology,
39
(4)
567 – 584
2008
ISSN: 09212728Keywords:▾
Eurasia; Lake Baikal; Russian Federation; catchment; data set; GIS; paleoclimate; paleolimnology; palynology; plant; population distribution
Abstract: ▾ Web-based Geographical Information Systems (GIS) are excellent tools within interdisciplinary and multi-national geoscience projects to exchange and visualize project data. The web-based GIS presented in this paper was designed for the paleolimnological project 'High-resolution CONTINENTal paleoclimate record in Lake Baikal' (CONTINENT) (Lake Baikal, Siberia, Russia) to allow the interactive handling of spatial data. The GIS database combines project data (core positions, sample positions, thematic maps) with auxiliary spatial data sets that were downloaded from freely available data sources on the world wide web. The reliability of the external data was evaluated and suitable new spatial datasets were processed according to the scientific questions of the project. GIS analysis of the data was used to assist studies on sediment provenance in Lake Baikal, or to help answer questions such as whether the visualization of present-day vegetation distribution and pollen distribution supports the conclusions derived from palynological analyses. The refined geodata are returned back to the scientific community by using online data publication portals. Data were made citeable by assigning persistent identifiers (DOI) and were published through the German National Library for Science and Technology (TIB Hannover, Hannover, Germany). © 2007 Springer Science+Business Media B.V.
697.
Archaeabacterial lipids in drill core samples from the Bosumtwi impact structure, Ghana
Meteoritics and Planetary Science,
43
(11)
1777 – 1782
2008
ISSN: 10869379
Publisher: University of Arkansas
Abstract: ▾ Meteorite impacts are associated with locally profound effects for microorganisms living at the terrestrial surface and the subsurface of the impact zone. The Bosumtwi crater in Ghana (West Africa) is a relatively young (1.07 Myr) structure with a rim-to-rim diameter of about 10.5 km. In a preliminary study targeting the subsurface microbial life in the impact structure, seven samples of the impact breccia from the central uplift of the Bosumtwi crater were analyzed for the presence of typical archaeal membrane-lipids (GDGTs). These have been detected in four of the samples, at a maximum depth of 382 m below the lake surface, which is equivalent to 309 m below the surface sediment. The concentration of the GDGTs does not show a trend with depth, and their distribution is dominated by GDGT-O. Possible origins of these lipids could be related to the soils or rocks predating the impact event, the hydrothermal system generated after the impact, or due to more recent underground water transport. © The Meteoritical Society, 2008.
696.
AntiSloughing Drilling Fluid in Main Well bore of SLCORE-I Well (in Chinese with English abstract); [松科1井(主井)防塌钻井液技术]
Petroleum Drilling Techniques,
36
(5)
54-57
2008
695.
Ancient Lake Ohrid: Biodiversity and evolution
Hydrobiologia,
615
(1)
103 – 140
2008
ISSN: 15735117Keywords:▾
Animalia; Mollusca; Mya; Animals; Biodiversity; Offshore oil well production; Rivers; biodiversity; evolution; evolutionary biology; lake; limnology; native species; Pleistocene; speciation (biology); Ancient lake; Balkans; Endemism; Geology; Lake Ohrid; Lake Prespa; Limnology; Sister lakes; Speciation; Lakes
Abstract: ▾ Worldwide ancient lakes have been a major focal point of geological, biological, and ecological research, and key concepts in, for example, evolutionary biology are partly based on ancient lake studies. Ancient lakes can be found on most continents and climate zones with most actual or putative ancient lakes in Europe being restricted to the Balkan Region. The arguably most outstanding of them is the oligotrophic and karstic Lake Ohrid, a steep-sided graben of rift formation origin situated in the central Balkans. Here, an attempt is made to summarize current knowledge of the geological, limnological, and faunal history of Lake Ohrid. Additionally, existing data on biodiversity and endemism in Lake Ohrid are updated and evaluated, and patterns and processes of speciation are reviewed in the context of the Ohrid watershed, including its sister lake, Lake Prespa. Whereas the geological history of the Ohrid Graben is relatively well studied, there is little knowledge about the limnological and biotic history of the actual lake (e.g., the age of the extant lake or from where the lake first received its water, along with its first biota). Most workers agree on a time frame of origin for Lake Ohrid of 2-5 million years ago (Mya). However, until now, the exact limnological origin and the origin of faunal or floral elements of Lake Ohrid remain uncertain. Two largely contrasting opinions either favour the theory of de novo formation of Lake Ohrid in a dry polje with a spring or river hydrography or a palaeogeographical connection of Lake Ohrid to brackish waters on the Balkan Peninsula. Whereas neither theory can be rejected at this point, the data summarized in the current review support the de novo hypothesis. An assessment of the fauna and flora of Lake Ohrid confirms that the lake harbours an incredible endemic biodiversity. Despite the fact that some biotic groups are poorly studied or not studied at all, approximately 1,200 native species are known from the lake, including 586 animals, and at least 212 species are endemic, including 182 animals. The adjusted rate of endemicity is estimated at 36% for all taxa and 34% for Animalia. In terms of endemic biodiversity, Lake Ohrid is with these 212 known endemic species and a surface area of 358 km2 probably the most diverse lake in the world, taking surface area into account. Preliminary phylogeographical analyses of endemic Lake Ohrid taxa indicate that the vast majority of respective sister taxa occurs in the Balkans and that therefore the most recent common ancestors of Ohrid- and non-Ohrid species likely resided in the region when Lake Ohrid came into existence. These data also indicate that there is relatively little faunal exchange and overlap between Lake Ohrid and its sister lake, Lake Prespa, despite the fact that the latter lake is a major water supplier for Lake Ohrid. Studies on selected species flocks and scatters, mostly in molluscs, point towards the assumption that only few lineages originally colonized Lake Ohrid from the Balkans and that the majority of endemic species seen today probably started to evolve within the lake during the early Pleistocene. Within the Ohrid watershed, endemism occurs at different spatial and taxonomic scales, ranging from species endemic to certain parts of Lake Ohrid to species endemic to the whole watershed and from subspecies to genus level and possibly beyond. Modes of speciation in the Ohrid watershed are largely affected by its degree of isolation. Observational evidence points towards both allopatric (peripatric) and parapatric speciation. Though sympatric speciation within a habitat is conceivable, so far there are no known examples. Today, the lake suffers from increasing anthropogenic pressure and a "creeping biodiversity crisis". Some endemic species presumably have already gone extinct, and there are also indications of invasive species penetrating Lake Ohrid. The comparatively small size of Lake Ohrid and the extremely small range of many endemic species, together with increasing human pressure make its fauna particularly vulnerable. It is thus hoped that this review will encourage future research on the ecology and evolutionary biology of the lake's taxa, the knowledge of which would ultimately help protecting this unique European biodiversity hot spot. © 2008 Springer Science+Business Media B.V.