All ICDP Publications with Abstracts
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1144.
Secondary hydrothermal minerals in buried rocks at the Campi Flegrei caldera, Italy: A possible tool to understand the rock-physics and to assess the state of the volcanic system
Periodico di Mineralogia,
80
(3)
385-406
2011
ISSN: 03698963
Publisher: Sapienza Universita Editrice
Abstract: ▾ The distribution of the alteration assemblages and the related physico-chemical changes induced in the rocks with depth, may provide useful information on the state of the system. Drillholes are the only way to define hydrothermal alteration depth-profiles in variable geological contexts. Deep drillings exploiting programs were conducted since the 1970's by the Agip-Enel Joint Venture in the Quaternary Campi Flegrei caldera (southern Italy), where a geothermal system has been active since at least historical times. New macroscopic and microscopic investigations were performed on selected samples made available by Agip in order to: 1) define the precursor lithology, 2) describe the relationships among texture, mineralogy and depth of the studied core samples and 3) examine the character of the secondary minerals and their distribution with depth and temperature. The new data are integrated with physical properties and elastic parameters of cored rocks, as well as structural information and field data, all available from the physical, seismological, geodetical and volcanological literature. The depth-related multi-parameters profiles provide evidence on the different behavior of the buried rocks beneath the Licola 1, Mofete and San Vito 1 areas, sited in three structurally different sectors of the caldera. The features of the hydrothermally altered rocks are a key to interpret the heterogeneities of the Campi Flegrei substratum, as deduced by velocity, attenuation and scattering P- and S- waves tomography. The time and space distribution of both the eruptive vents and the extruded magma volumes are consistent with the results of our analysis. Therefore, we interpret the observed Campi Flegrei geothermal system as a response to the distribution of volcanic activity in two structurally distinct sectors of the caldera. The central-eastern sector, where the San Vito 1 well was drilled, represents the preferential pathways for both gas escape and magma ascent at least since 8 kyrs, in contrast with the other sites of the caldera where eruptions occurred with minor frequency and magnitude.
1143.
Shallow marine carbon and oxygen isotope and elemental records indicate icehouse-greenhouse cycles during the Early Jurassic
Paleoceanography,
26
(4)
2011
ISSN: 08838305
Publisher: Blackwell Publishing Ltd
Keywords:▾
Cleveland Basin; England; North Yorkshire; United Kingdom; anoxic conditions; benthos; biostratigraphy; brachiopod; carbon isotope; depositional sequence; environmental change; fossil record; glaciation; greenhouse effect; nekton; oxygen isotope; paleoceanography; paleoenvironment; Pliensbachian; sea level change; seafloor; sequence stratigraphy; Sinemurian
Abstract: ▾ For much of the Mesozoic record there has been an inconclusive debate on the possible global significance of isotopic proxies for environmental change and of sequence stratigraphic depositional sequences. We present a carbon and oxygen isotope and elemental record for part of the Early Jurassic based on marine benthic and nektobenthic molluscs and brachiopods from the shallow marine succession of the Cleveland Basin, UK. The invertebrate isotope record is supplemented with carbon isotope data from fossil wood, which samples atmospheric carbon. New data elucidate two major global carbon isotope events, a negative excursion of ∼2‰ at the Sinemurian-Pliensbachian boundary, and a positive excursion of ∼2‰ in the Late Pliensbachian. The Sinemurian-Pliensbachian boundary event is similar to the slightly younger Toarcian Oceanic Anoxic Event and is characterized by deposition of relatively deepwater organic-rich shale. The Late Pliensbachian strata by contrast are characterized by shallow marine deposition. Oxygen isotope data imply cooling locally for both events. However, because deeper water conditions characterize the Sinemurian-Pliensbachian boundary in the Cleveland Basin the temperature drop is likely of local significance; in contrast a cool Late Pliensbachian shallow seafloor agrees with previous inference of partial icehouse conditions. Both the large-scale, long-term and small-scale, short-duration isotopic cycles occurred in concert with relative sea level changes documented previously from sequence stratigraphy. Isotope events and the sea level cycles are concluded to reflect processes of global significance, supporting the idea of an Early Jurassic in which cyclic swings from icehouse to greenhouse and super greenhouse conditions occurred at timescales from 1 to 10 Ma. Copyright 2011 by the American Geophysical Union.
1142.
Shock metamorphism investigations of quartz grains in clasts from impact breccia of the Eyreville B drill core, Chesapeake Bay impact structure, USA
Meteoritics and Planetary Science,
46
(5)
621-637
2011
ISSN: 10869379Abstract: ▾ The Chesapeake Bay impact structure, approximately 85km in diameter, has been drilled in 2005-2006 at Eyreville (Virginia, USA), to a total depth of 1766m. In the drill cores, the abundance of shock metamorphosed material is very variable with depth. Shocked mineral and lithic clasts, as well as melt particles, are most abundant in suevitic impact breccia section (1397-1451m depth). Shocked quartz (i.e., quartz grains with planar fractures and/or planar deformation features) and melt particles, although rare, are also dispersed in the Exmore Formation unit (444-867m depth). Other lithologies in the Eyreville drill cores show no clear evidence of shock metamorphism. Here, we report on the investigations of 40 samples from the impact breccia section. A total of more than 27,000 quartz grains were examined in about 200 clasts. The abundance of highly shocked clasts tends to decrease with increasing depth. Crystalline clasts derived from the crystalline basement are commonly only slightly shocked (contain generally <10rel% of shocked quartz grains). The clasts of metamorphosed sediments show a low proportion of shocked quartz grains (mostly <10rel%). Sedimentary clasts show a wide range of proportions of shocked quartz grains, with several of them being highly shocked clasts (most values between 0 and 40rel%). Conglomerates show the highest proportion of shocked quartz grains of all types of clasts (up to 83rel%). Polycrystalline quartz clasts are also commonly highly shocked (contain mostly between 10 and 40rel% of shocked quartz grains). These hard nonporous clasts are possibly more liable to show evidence of shock. The investigations suggest that the intensity of shock metamorphism is the result of several parameters, such as original position in the target (both horizontal and vertical) and the properties of each lithology (e.g., grain size, porosity, and amount of matrix). According to the universal-stage investigations, the dominant orientations of planar deformation features in quartz are {101̄3}, {101̄2}, and also {101̄4}. © The Meteoritical Society, 2011.
1141.
Short term earthquake forecasts at Koyna, India
Journal of the Geological Society of India,
77
(1)
5-11
2011
ISSN: 00167622Keywords:▾
earthquake magnitude; earthquake prediction; nucleation; observational method; seismic zone, India; Koyna; Maharashtra
Abstract: ▾ Earthquake activity is monitored in real time at the Koyna reservoir in western India, beginning from August 2005 and successful short term forecasts have been made of M ∼ 4 earthquakes. The basis of these forecasts is the observation of nucleation that precedes such earthquakes. Here we report that a total of 29 earthquakes in the magnitude range of 3.5 to 5.1 occurred in the region during the period of August 2005 through May 2010. These earthquakes could broadly be put in three zones. Zone-A has been most active accounting for 18 earthquakes, while 5 earthquakes in Zone-B and 6 in Zone-C have occurred. Earthquakes in Zone-A are preceded by well defined nucleation, while it is not the case with zones B and C. This indicates the complexity of the earthquakes processes and the fact that even in a small seismically active area of only 20 km × 30 km earthquake forecast is difficult. © 2011 Geological Society of India.
1140.
Soft-sediment deformation within seismogenic slumps of the Dead Sea Basin
Journal of Structural Geology,
33
(4)
433-457
2011
ISSN: 01918141Keywords:▾
Dead Sea; Folds; Gravity-driven deformation; Mass transport complexes; Slump, Anoxic sediments; Deformation; Earthquakes; Mass transfer; Sedimentology, Gravitation, deformation; earthquake; fold; mass transport; slumping, Dead Sea
Abstract: ▾ The Late Pleistocene Lisan Formation preserved next to the Dead Sea provides exceptional 3-D exposures of folds and faults generated during soft-sediment slumping and deformation. It is possible to generate a range of four different scenarios associated with overprinting in a single slump event. The progressive evolution of slump systems may be broadly categorised into initiation, translation, cessation, relaxation and compaction phases. Thrust packages typically define piggyback sequences during slump translation, with back-steepening of imbricate faults leading to collapse of folds back up the regional palaeoslope. Detailed evaluation of slumped horizons may also permit structures to be traced across apparently separate and distinct slumped units. The recognition that slumps may be reworked by younger seismically-triggered events suggests that in some cases the seismic recurrence interval may be shorter than previously anticipated. © 2011 Elsevier Ltd.
1139.
Solubility of H2O and CO2 in shoshonitic melts at 1250°C and pressures from 50 to 400MPa: Implications for Campi Flegrei magmatic systems
Journal of Volcanology and Geothermal Research,
202
(3-4)
251 – 261
2011
ISSN: 03770273Keywords:▾
Campania [Italy]; Campi Flegrei; Italy; Lipari Islands; Messina [Sicily]; Napoli [Campania]; Sicily; Vulcano; Aluminosilicates; Bearings (structural); Crystals; Fluids; Fourier transform infrared spectroscopy; Glass; Solubility; Water absorption; Campi Flegrei; ; O; Shoshonitic magmas; Vulcanello; absorption coefficient; carbon dioxide; FTIR spectroscopy; mafic rock; magma; magma chamber; magmatism; phenocryst; shoshonite; silicate melt; solubility; volcanic eruption; volcanic glass; Absorption spectroscopy
Abstract: ▾ The solubility of H2O-CO2-bearing fluids in shoshonitic melts relevant to magmas of the Vulcanello peninsula and to mafic melts from magmas erupted at Campi Flegrei (Italy) was experimentally determined at pressures from 50 to 400MPa and at temperature of 1250°C. No quench crystals and less than 1vol.% bubles were observed in the rapid quenched glasses. H2O and CO2 contents in the experimental glasses were determined via Karl-Fischer Titration (KFT) and FTIR spectroscopy. For the quantification of volatile concentrations by IR spectroscopy we have calibrated the absorption coefficients of water-related and carbon-related IR bands for the shoshonitic composition. The determined absorption coefficients are 0.80±0.06L mol-1 cm-1 for the band at ~4500cm-1 (OH groups) and 1.02±0.03L mol-1 cm-1 for the band at ~5200cm-1 (H2O molecules). CO2 is bound in the shoshonitic glass as CO32- exclusively; its concentration was quantified by the peak height of the low wavenumber band of the doublet near 1430cm-1 using the calibrated absorption coefficient of 356±18L mol-1 cm-1.The H2O solubility in the shoshonitic melts is in the same range as observed for other natural aluminosilicate melts, i.e. 5.12±0.07wt.% at 200MPa and 7.92±0.07wt.% H2O at 400MPa. A non-linear variation of the H2O and CO2 solubility in the melts with increasing mole fraction of H2O (and thus decreasing mole fraction of CO2) in the fluid was observed at each investigated pressure. At 1250°C, the concentration of dissolved carbonate (expressed as CO2 component) in melts coexisting with nearly pure CO2 fluid increases from 307 to 2932ppm (±10% relative) as the pressure increases from 50 to 400MPa. The comparison of the dataset with available models predicting the H2O and CO2 concentrations in silicate melts coexisting with H2O-CO2-bearing fluids shows that the effect of melt composition is not calibrated appropriately in the models.The experimental data are used to re-evaluate the typical pressures of glass inclusions entrapment in phenocrysts from Minopoli2 eruption and the results indicate that the main magma chamber may have been located at a depth of ~ 4000 m. © 2011 Elsevier B.V.
1138.
Spatial distribution and flux of terrigenic He dissolved in the sediment pore water of Lake Van (Turkey)
Geochimica et Cosmochimica Acta,
75
(10)
2848-2864
2011
ISSN: 00167037Keywords:▾
basin evolution; deep-sea sediment; helium; isotopic composition; lacustrine deposit; lake water; mantle source; noble gas; permeability; porewater; sediment chemistry; sedimentary structure; spatial distribution, Lake Van; Turkey
Abstract: ▾ In this study, the largest ever carried out to measure noble gases in the pore water of unconsolidated sediments in lakes, the emission of terrigenic He through the sediment column of Lake Van was successfully mapped on the local scale. The main input of He to the water body occurs at the borders of a deep basin within the lake, which is probably the remains of a collapsed caldera. The 3He/4He ratio identifies the He injected into the sedimentary column of Lake Van as a mixture of He released from a mantle source and radiogenic He of crustal origin (3He/4He~2.6-4.1×10-6). During passage through the pore space, terrigenic He seems to be further enriched in radiogenic He that is most likely produced in the sediment column. In fact, two distinct trends in isotopic composition can be distinguished in the He injected from the lake basement into the sediments. One of these characterizes samples from the shallow water, the other characterizes samples from the deep basin. However, both of these trends are related to the same source of terrigenic He. The He fluxes determined seem to be characteristic of each sampling location and might be considered as a proxy for the fluid permeability of the deep sediment column. These new findings provide insight into the process of fluid transport within the sediments and into the process of formation of the lake basin. Moreover, the isotopic signature of the He that emanates into the water column of Lake Van is strongly affected by the mixing conditions prevailing in the overlying water body. This fact misled previous studies to interpret the terrigenic He in Lake Van as being solely of mantle origin (3He/4He~10-5). © 2011 Elsevier Ltd.
1137.
The Lake El'gygytgyn scientific drilling project - conquering Arctic challenges through continental drilling
Scientific Drilling
(1)
29-40
2011
ISSN: 18168957
Publisher: Copernicus GmbH
Keywords:▾
Anoxic sediments; Catchments; Core drilling; Deposits; Drilling platforms; Glacial geology; Meteor impacts; Meteorites; Permafrost; Recovery; Runoff; Sedimentology; Volcanic rocks; Volcanoes, Alluvial fans; Basement rocks; Drill core; Drilling targets; Environmental history; Ice cover; Ice-rich permafrost; Impact events; Information concerning; Lake sediments; Level fluctuation; Meteorite impact; Mid-Pliocene; Pliocene; Pliocene deposits; Scientific drilling; SIBERIA; Underlying rocks, Lakes
Abstract: ▾ Between October 2008 and May 2009, the International Continental Scientific Drilling Program (ICDP) co-sponsored a campaign at Lake El'gygytgyn, located in a 3.6-Ma-old meteorite impact crater in northeastern Siberia. Drilling targets included three holes in the center of the 170-m-deep lake, utilizing the lake ice cover as a drilling platform, plus one hole close to the shore in the western lake catchment. At the lake's center. the entire 315-m-thick lake sediment succession was penetrated. The sediments lack any hiatuses (i.e., no evidence of basin glaciation or desiccation), and their composition reflects the regional climatic and environmental history with great sensitivity. Hence, the record provides the first comprehensive and widely timecontinuous insights into the evolution of the terrestrial Arctic since mid-Pliocene times. This is particularly true for the lowermost 40 meters and uppermost 150 meters of the sequence, which were drilled with almost 100% recovery and likely reflect the initial lake stage during the Pliocene and the last ~2.9 Ma, respectively. Nearly 200 meters of underlying rock were also recovered; these cores consist of an almost complete section of the various types of impact breccias including broken and fractured volcanic basement rocks and associated melt clasts. The investigation of this core sequence promises new information concerning the El'gygytgyn impact event, including the composition and nature of the meteorite, the energy released, and the shock behavior of the volcanic basement rocks. Complementary information on the regional environmental history, including the permafrost history and lake-level fluctuations, is being developed from a 142-m-long drill core recovered from the permafrost deposits in the lake catchment. This core consists of gravelly and sandy alluvial fan deposits in ice-rich permafrost, presumably comprising a discontinuous record of both Quaternary and Pliocene deposits.
1136.
Spatially explicit analysis of gastropod biodiversity in ancient Lake Ohrid
Biogeosciences,
8
(1)
175 – 188
2011
ISSN: 17264189Keywords:▾
Lake Ohrid; Gastropoda; endemic species; environmental factor; evolutionary biology; gastropod; heterogeneity; spatial analysis; spatial variation; species diversity; spring water; taxonomy; water depth
Abstract: ▾ The quality of spatial analyses of biodiversity is improved by (i) utilizing study areas with well defined physiogeographical boundaries, (ii) limiting the impact of widespread species, and (iii) using taxa with heterogeneous distributions. These conditions are typically met by ecosystems such as oceanic islands or ancient lakes and their biota. While research on ancient lakes has contributed significantly to our understanding of evolutionary processes, statistically sound studies of spatial variation of extant biodiversity have been hampered by the frequently vast size of ancient lakes, their limited accessibility, and the lack of scientific infrastructure. The European ancient Lake Ohrid provides a rare opportunity for such a reliable spatial study. The comprehensive horizontal and vertical sampling of a species-rich taxon, the Gastropoda, presented here, revealed interesting patterns of biodiversity, which, in part, have not been shown before for other ancient lakes. In a total of 284 samples from 224 different locations throughout the Ohrid Basin, 68 gastropod species, with 50 of them (= 73.5%) being endemic, could be reported. The spatial distribution of these species shows the following characteristics: (i) within Lake Ohrid, the most frequent species are endemic taxa with a wide depth range, (ii) widespread species (i.e. those occurring throughout the Balkans or beyond) are rare and mainly occur in the upper layer of the lake, (iii) while the total number of species decreases with water depth, the proportion of endemics increases, and (iv) the deeper layers of Lake Ohrid appear to have a higher spatial homogeneity of biodiversity. Moreover, gastropod communities of Lake Ohrid and its feeder springs are both distinct from each other and from the surrounding waters. The analysis also shows that community similarity of Lake Ohrid is mainly driven by niche processes (e.g. environmental factors), but also by neutral processes (e.g. dispersal limitation and evolutionary histories of species). For niche-based mechanisms it is shown that large scale effects such as type of water body or water depth are mainly responsible for the similarity of gastropod communities, whereas small scale effects like environmental gradients affect gastropod compositions only marginally. In fact, neutral processes appear to be more important than the small scale environmental factors, thus emphasizing the importance of dispersal capacities and evolutionary histories of species. © Author(s) 2011.
1135.
Spatiotemporal earthquake clusters along the North Anatolian fault zone offshore İstanbul
Bulletin of the Seismological Society of America,
101
(4)
1759-1768
2011
ISSN: 00371106Keywords:▾
Cross correlations; Double differences; Fault kinematics; High-precision; Mainshock; Marmara Sea; Micro-earthquakes; Microseismicity; North Anatolian Fault Zone; Northwest Turkey; Progressive failure; Region of interest; Relative location; Rupture zone; Seismic sequence; Seismotectonics; Source sizes; Spatiotemporal distributions; Temporal distribution; Travel time; Wave forms, Image segmentation, Earthquakes, accuracy assessment; aftershock; earthquake catalogue; earthquake hypocenter; earthquake magnitude; earthquake mechanism; earthquake rupture; earthquake swarm; fault zone; Kocaeli earthquake 1999; microearthquake; spatiotemporal analysis; tectonic setting, Anatolia; Sea of Marmara; Turkey
Abstract: ▾ We investigate earthquakes with similar waveforms in order to characterize spatiotemporal microseismicity clusters within the North Anatolian fault zone (NAFZ) in northwest Turkey along the transition between the 1999 İzmit rupture zone and the Marmara Sea seismic gap. Earthquakes within distinct activity clusters are relocated with cross-correlation derived relative travel times using the double difference method. The spatiotemporal distribution of micro earthquakes within individual clusters is resolved with relative location accuracy comparable to or better than the source size. High-precision relative hypocenters define the geometry of individual fault patches, permitting a better understanding of fault kinematics and their role in local-scale seismotectonics along the region of interest. Temporal seismic sequences observed in the eastern Sea of Marmara region suggest progressive failure of mostly nonoverlapping areas on adjacent fault patches and systematic migration of microearthquakes within clusters during the progressive failure of neighboring fault patches. The temporal distributions of magnitudes as well as the number of events follow swarmlike behavior rather than a mainshock/aftershock pattern.
1134.
Structure and composition of organic matter and isotope geochemistry of the palaeoproterozoic graphite and sulphide-rich metasedimentary rocks from the Outokumpu Deep Drill Hole, eastern Finland
Special Paper of the Geological Survey of Finland,
2011
(51)
219 – 228
2011
ISSN: 07828535ISBN:
978-952217152-8
Abstract: ▾ Graphitic schists from the Outokumpu Deep Drill Hole were investigated in order to reconstruct the structure and composition of organic matter and stable isotope carbon and sulphur geochemistry of graphite, pyrite and pyrrhotite. Core samples of graphitic schists were collected from three depth levels of the Outokumpu Deep Drill Hole. The studied rocks were biotite-(tremolite-) graphite and, occasionally, muscovite (sericite)- and titanite-bearing schists and quartzitic schists. All samples were enriched in sulphides (mostly pyrite and pyrrhotite). Carbon isotope δ13C values of graphitic C were found to vary from -18.4 to -27.4‰. Graphitic schists from the middle part of the core in association with ophiolite-derived serpentinite and other altered ultramafic rocks showed more elevated δ13C values. This suggests incorporation of isotopically heavy carbon species during metamorphism, probably resulting from decarbonation reactions in carbonatebearing rocks. d34S values in the graphitic schists of the Outokumpu Deep Drill Hole were determined to be in range of -3.0 to -9.9‰ for pyrite and -3.8 to -10.8‰ for pyrrhotite. These concentrations could be explained by bacterial reduction of seawater sulphate and, to some extent, by the addition of hydrothermal sulphur. The predominance of aliphatic and oxygen-bearing groups in the bitumen structure suggests a sapropelic origin of the organic matter. Particularities in the distribution of Corganic and chemical changes in the bitumen composition along the core section could be interpreted as evidence of different sources and possibly the re-deposition of organic matter.
1133.
The Advance of Delta lgR Method and Its Application in Songliao Basin
Journal of Jilin University(Earth Science Edition),
41
(2)
586-591
2011
1132.
The chicxulub multi-ring impact crater, yucatan carbonate platform, Gulf of Mexico
Geofisica Internacional,
50
(1)
99-127
2011
Abstract: ▾ The Chicxulub impact crater is part of a select group of unique geological sites, being a natural laboratory to investigate crater formation processes and global effects of large-scale impacts. Chicxulub is one of only three multi-ring craters documented in the terrestrial record and impact has been related to the global environmental/climatic effects and mass extinction that mark the Cretaceous/Paleogene (K/Pg) boundary. The crater is buried under ~1.0 km of carbonate sediments in the Yucatan peninsula. The buried structure was initially identified from geophysical surveys of the PEMEX oil exploration program in southeastern Mexico. On the surface its influence is marked by the circular ring of cenotes that have formed from differential compaction and fracturing between the impact breccias and surrounding limestone sequences. The crater is about ~200 km in rim diameter, half on-land and half off-shore with geometric center at Chicxulub Puerto, making it possible to use land, marine and aerial geophysical methods. The Yucatan carbonate platform is an ideal place to have the crater, tectonically stable with no volcanic activity, having formed by slow deposition of carbonate sediments. These characteristics permit high resolution imagery of the crater underground structure with unprecedented detail. The impact and crater formation occur instantaneously, with excavation of the crust down to ~25 km depths in fractions of a second and lower crust uplift and crater formation in the next few hundred seconds. Energy release results in intense fracturing and deformation at the target site, generating seismic waves traveling the whole Earth. Understanding the physics of impacts on planetary surfaces and modeling of crustal deformation and rheological behavior of materials at high temperatures and pressures remain major challenges in geosciences. The K/Pg ejecta layer is the only global stratigraphic marker in the geological record, allowing correlation of events worldwide. In the last 20 years much has been learned about the Chicxulub crater and the K/Pg boundary; however what is perhaps most interesting are the questions remaining, which include fundamental aspects of Chicxulub impact and its environmental effects.
1131.
The deep biosphere in terrestrial sediments in the Chesapeake Bay area, Virginia, USA
Frontiers in Microbiology,
2
(JULY)
2011
ISSN: 1664302X
Publisher: Frontiers Research Foundation
Keywords:▾
Anaerolineae; Archaea; Bacteria (microorganisms); candidate division JS1; Chloroflexi; Chloroflexi (class); Crenarchaeota; Eukaryota; Euryarchaeota; Prokaryota
Abstract: ▾ For the first time quantitative data on the abundance of Bacteria, Archaea, and Eukarya in deep terrestrial sediments are provided using multiple methods (total cell counting, quantitative real-time PCR, Q-PCR and catalyzed reporter deposition-fluorescence in situ hybridization, CARD-FISH). The oligotrophic (organic carbon content of ̃0.2%) deep terrestrial sediments in the Chesapeake Bay area at Eyreville, Virginia, USA, were drilled and sampled up to a depth of 140 m in 2006. The possibility of contamination during drilling was checked using fluorescent microspheres. Total cell counts decreased from 109 to 106 cells/g dry weight within the uppermost 20 m, and did not further decrease with depth below. Within the top 7 m, a significant proportion of the total cell counts could be detected with CARD-FISH.The CARD-FISH numbers for Bacteria were about an order of magnitude higher than those for Archaea. The dominance of Bacteria over Archaea was confirmed by Q-PCR. The down core quantitative distribution of prokaryotic and eukaryotic small sub- unit ribosomal RNA genes as well as functional genes involved in different biogeochemical processes was revealed by Q-PCR for the uppermost 10 m and for 80-140 m depth. Eukarya and the Fe(III)- and Mn(IV)-reducing bacterial group Geobacteriaceae were almost exclu- sively found in the uppermost meter (arable soil), where reactive iron was detected in higher amounts. The bacterial candidate division JS-1 and the classes Anaerolineae and Caldilineae of the phylum Chloroflexi, highly abundant in marine sediments, were found up to the maximum sampling depth in high copy numbers at this terrestrial site as well. A similar high abundance of the functional gene cbbL encoding for the large subunit of RubisCO suggests that autotrophic microorganisms could be relevant in addition to het- erotrophs. The functional gene aprA of sulfate reducing bacteria was found within distinct layers up to ca. 100 m depth in low copy numbers.The gene mcrA of methanogens was not detectable. Cloning and sequencing data of 16S rRNA genes revealed sequences of typi- cal soil Bacteria. The closest relatives of the archaeal sequences were Archaea recovered from terrestrial and marine environments. Phylogenetic analysis of the Crenarchaeota and Euryarchaeota revealed new members of the uncultured South African Gold Mine Group, Deep Sea Hydrothermal Vent Euryarchaeotal Group 6, and Miscellaneous Crenarcheotic Group clusters. © 2011 Breuker, Köweker, Blazejak and Schippers.
1130.
The Discussion of the Era of the Cretaceous Qingshankou Formation in Songliao Basin (in Chinese with English abstract); [松辽盆地白垩纪青山口组地质时代探讨]
Science Technology and Engineering,
11
(3)
461-466
2011
1129.
Melt in the impact breccias from the Eyreville drill cores, Chesapeake Bay impact structure, USA
Meteoritics and Planetary Science,
46
(3)
396-430
2011
ISSN: 10869379Abstract: ▾ The center of the 35.3Ma Chesapeake Bay impact structure (85km diameter) was drilled during 2005/2006 in an ICDP-USGS drilling project. The Eyreville drill cores include polymict impact breccias and associated rocks (1397-1551m depth). Tens of melt particles from these impactites were studied by optical and electron microscopy, electron microprobe, and microRaman spectroscopy, and classified into six groups: m1-clear or brownish melt, m2-brownish melt altered to phyllosilicates, m3-colorless silica melt, m4-melt with pyroxene and plagioclase crystallites, m5-dark brown melt, and m6-melt with globular texture. These melt types have partly overlapping major element abundances, and large compositional variations due to the presence of schlieren, poorly mixed melt phases, partly digested clasts, and variable crystallization and alteration. The different melt types also vary in their abundance with depth in the drill core. Based on the chemical data, mixing calculations were performed to determine possible precursors of these melt particles. The calculations suggest that most melt types formed mainly from the thick sedimentary section of the target sequence (mainly the Potomac Formation), but an additional crystalline basement (schist/gneiss) precursor is likely for the most abundant melt types m2 and m5. Sedimentary rocks with compositions similar to those of the melt particles are present among the Eyreville core samples. Therefore, sedimentary target rocks were the main precursor of the Eyreville melt particles. However, the composition of the melt particles is not only the result of the precursor composition but also the result of changes during melting and solidification, as well as postimpact alteration, which must also be considered. The variability of the melt particle compositions reflects the variety of target rocks and indicates that there was no uniform melt source. Original heterogeneities, resulting from melting of different target rocks, may be preserved in impactites of some large impact structures that formed in volatile-rich targets, because no large melt body exists, in which homogenization would have taken place. © The Meteoritical Society, 2011.
1128.
Well logging proxy of the Late Cretaceous palaeoclimate change in Songliao Basin
Journal of Palaeogeography,
13103-110
2011
1127.
Mechanical twinning in quartz: Shock experiments, impact, pseudotachylites and fault breccias
Tectonophysics,
510
(1-2)
69-79
2011
ISSN: 00401951Keywords:▾
C-axis orientations; Creeping segment; Diffraction methods; Drilling projects; EBSD; Fault breccia; Fault surfaces; Frictional melting; High stress; Mechanical twinning; Meteorite impact; Mylonites; Preferred orientations; Pseudotachylites; San Andreas Fault; Seismic stress; Shock deformation; South Africa; Southern California; Transient stress; Twin-free, Crystal structure; Meteor impacts; Quartz deposits; Rocks; Seismology; Structural geology, Quartz, breccia; crystal structure; deformation mechanism; ductile deformation; experimental study; microstructure; preferred orientation; pseudotachylite; quartz; San Andreas Fault; twinning, South Africa
Abstract: ▾ Increasing use of diffraction methods to study preferred orientation of minerals has established that quartz in deformed rocks not only displays characteristic c-axis orientation patterns, but that there is also generally a distinct difference in the orientation of positive and negative rhombs. In the trigonal quartz crystal structure positive and negative rhombs are structurally different, and particularly negative rhombs (e.g. {01. 1-1}) are much stiffer than positive rhombs (e.g. {10. 1-1}). Here, we focus on the role of mechanical Dauphiné twinning under stress as a cause of this difference and illustrate with EBSD measurements ubiquitous twinning in quartz-bearing rocks subjected to high stresses. Characteristic twinning is observed in experimentally shocked sandstones and stishovite-bearing quartzites from the Vredefort meteorite impact site in South Africa. Similar twinning is documented for quartz associated with pseudotachylites from the Santa Rosa mylonite zone in Southern California, whereas quartz in underlying ductile mylonites are more or less twin-free. It suggests that twinning was produced by local seismic stresses that caused fracture and frictional melting on fault surfaces. Quartz-bearing breccias from the SAFOD (San Andreas Fault Observatory at Depth) drilling project also show evidence of twinning and suggest high seismic stresses in the currently creeping segment of the San Andreas Fault at Parkfield. From these observations it appears that Dauphiné twin microstructures can be diagnostic of high local and transient stresses. © 2011 Elsevier B.V.
1126.
Dead Sea deep cores: A window into past climate and seismicity
Eos,
92
(49)
453-454
2011
ISSN: 00963941
Publisher: Blackwell Publishing Ltd
Keywords:▾
archaeology; deep drilling; drilling rig; environmental conditions; paleoclimate; paleoenvironment; paleomagnetism; paleoseismicity; Stone Age; tectonic structure, Dead Sea
Abstract: ▾ The area surrounding the Dead Sea was the locus of humankind's migration out of Africa and thus has been the home of peoples since the Stone Age. For this reason, understanding the climate and tectonic history of the region provides valuable insight into archaeology and studies of human history and helps to gain a better picture of future climate and tectonic scenarios. The deposits at the bottom of the Dead Sea are a geological archive of the environmental conditions (e.g., rains, floods, dust storms, droughts) during ice ages and warm ages, as well as of seismic activity in this key region. An International Continental Scientific Drilling Program (ICDP) deep drilling project was performed in the Dead Sea between November 2010 and March 2011. The project was funded by the ICDP and agencies in Israel, Germany, Japan, Norway, Switzerland, and the United States. Drilling was conducted using the new Large Lake Drilling Facility (Figure 1), a barge with a drilling rig run by DOSECC, Inc. (Drilling, Observation and Sampling of the Earth's Continental Crust), a nonprofit corporation dedicated to advancing scientific drilling worldwide. The main purpose of the project was to recover a long, continuous core to provide a high resolution record of the paleoclimate, paleoenvironment, paleoseismicity, and paleomagnetism of the Dead Sea Basin. With this, scientists are beginning to piece together a record of the climate and seismic history of the Middle East during the past several hundred thousand years in millennial to decadal to annual time resolution.
1125.
Coastal sabkha dolomites and calcitised sulphates preserving the Lomagundi-Jatuli carbon isotope signal
Precambrian Research,
189
(1-2)
193-211
2011
ISSN: 03019268Keywords:▾
anhydrite; carbon isotope; carbonate; coastal sediment; dolomite; dolostone; gypsum; methanogenesis; organic carbon; oxygen; precipitation (chemistry); pseudomorph; sabkha; seawater; sulfate, Arkhangelsk [Russian Federation]; Onega Basin; Russian Federation, Centroberyx lineatus
Abstract: ▾ Palaeoproterozoic Tulomozero Formation carbonates of the Onega basin were targeted by ICDP FAR-DEEP Hole 10B. The recovered rocks contain abundant evidence for Palaeoproterozoic gypsum and anhydrite, particularly in the form of pseudomorphs of inclusion-containing nodules, swallow-tail twinned crystals and evaporite dissolution breccias. Similarly, sand-patch fabric indicates the former presence of surface-covering salt crusts in the Palaeoproterozoic. Atmospheric oxygen and seawater sulphate levels at that time must have been sufficient to allow such sulphates to form. Carbonate δ13C values are considered sedimentary or early diagenetic, predating greenschist facies metamorphism associated with the Svecofennian Orogeny. These carbonate δ13C values range from +7.7 to +15.7‰, with the highest (and lowest) values found in dolostones. The dolostones as well as calcitised calcium sulphates record the Lomagundi-Jatuli signal. However evidence for activity of sulphate-reducing and/or methanogenic bacteria seems to be lacking. Dolomite precipitation (or dolomitisation), calcium sulphate calcitisation and production of the high 13C values (processes which typically involve such bacteria in the Phanerozoic) are thus inferred to have proceeded without the direct influence of sulphate reducers and methanogens. The most plausible explanation for the Lomagundi-Jatuli excursion seems to remain significant sequestration of organic carbon in a location yet to be identified. © 2011 Elsevier B.V.
1124.
Comparative study of infrared techniques for fast biogeochemical sediment analyses
Geochemistry, Geophysics, Geosystems,
12
(10)
2011
Keywords:▾
Analytical geochemistry; Anoxic sediments; Biogeochemistry; Carbon; Cost benefit analysis; Fourier transform infrared spectroscopy; Near infrared spectroscopy; Organic carbon; Reflection; Sedimentology; Silica; Spectrometry; Spectrum analysis; Attenuated total reflectance; Biogenic silica; Biogeochemical sediments; Calibration model; Comparative studies; Correlation coefficient; Cost-efficient; Deep drilling; Diffuse reflectance; Diffuse reflectance fourier transform infrared; Fourier transform IR spectroscopy; Geochemical analysis; Geochemical properties; Infrared technique; Inorganic carbon; IR spectrometry; Limiting factors; Midinfrared; Near-IR spectroscopy; Organic sediments; Sediment samples; Statistical performance; Total inorganic carbon; Total nitrogen; total organic carbon (TOC); Visible-near infrared spectroscopy; biogeochemistry; calibration; comparative study; FTIR spectroscopy; inorganic carbon; near infrared; sediment analysis; total organic carbon; Fourier transforms
Abstract: ▾ Analysis of sediment samples in the visible to mid infrared (IR) region requires small amounts of sample material and enables rapid and cost efficient geochemical analysis of mineral and organic sediment components. Here we use geochemical properties (total organic and inorganic carbon, biogenic silica, total nitrogen) from the ICDP deep drilling project PASADO to compare three different IR spectroscopy techniques: Diffuse Reflectance Fourier Transform IR Spectrometry (DRIFTS), Attenuated Total Reflectance Fourier Transform IR Spectroscopy (ATR-FTIRS) and Visible Near IR Spectroscopy (VNIRS). ATR-FTIRS and VNIRS are more rapid techniques compared to DRIFTS. Results show that calibration models developed using DRIFTS are most robust (correlation coefficient: R = 0.92 for TIC, R = 0.84 for BSi, R = 0.97 for TOC, R = 0.95 for TN). However, good statistical performance was also obtained by using ATR-FTIRS and VNIRS. When time and costs are limiting factors, these tools may be given preference for rapid biogeochemical screening. Copyright © 2011 by the American Geophysical Union.
1123.
Comparing extension on multiple time and depth scales in the Corinth Rift, Central Greece
Geophysical Journal International,
186
(2)
463 – 470
2011
ISSN: 1365246XKeywords:▾
Central Greece; Greece; Gulf of Corinth; Ionian Sea; Mediterranean Sea; Anoxic sediments; Estimation; Geodesy; Morphology; Sedimentology; Tectonics; Central Basin; Continental tectonics; Crustal extension; Deformation mechanism; Detachment fault; Europe; Fault displacement; Fault growth; Geodetic data; Late quaternary; Natural laboratories; Neotectonics; Sediment accumulation; Sedimentary basin; Time range; active fault; deformation mechanism; detachment fault; extensional tectonics; fault displacement; geodesy; geomorphology; neotectonics; rift zone; sedimentary basin; strain rate; subsidence; upper crust; Strain rate
Abstract: ▾ The young (<5Ma) Corinth Rift is an ideal natural laboratory to investigate rift deformation mechanisms by comparing extension rates determined by various methods spanning different depth and time ranges. Corinth Rift geodetic extension rates averaged over 5-100 yr have been interpreted to increase from ~5 mm yr-1 or less in the east to >10-15 mm yr-1 in the west. We quantify total upper-crust and whole-crust extension on three profiles across the Corinth Rift. Whole-crust extension is greater across the central rift (~11-21 km) than across the western part of the rift (~5-13 km). This correlates with the overall rift morphology, which shows maximum basement subsidence, sediment accumulation, rift width and greatest summed Late Quaternary fault displacements in the central basin, but contrasts with the pattern of geodetic extension rates which are greater to the west of the central basin. The E-W increase in strain rates interpreted from geodetic data cannot have persisted over rift history to produce the observed rift morphology. We suggest the discrepancy between short-term and long-term extension patterns is related to shifts in the loci of maximum extension due to fault growth and linkage during Corinth Rift history, and is likely a characteristic of rift development in general. Total upper-crust and whole-crust extension estimates in the western rift, where extension estimates are best constrained, are within error. We propose that uniform pure-shear extension is a viable extension mechanism in the western rift and crustal extension estimates do not require the existence of a major active N-S dipping detachment fault. © 2011 The Authors Geophysical Journal International © 2011 RAS.
1122.
Consistent trends in the true triaxial strength and deformability of cores extracted from ICDP deep scientific holes on three continents
Tectonophysics,
503
(1-2)
45-51
2011
ISSN: 00401951Keywords:▾
Dilatancy; Fault angle; Scientific boreholes; True triaxial strength; True triaxial testing, Deformation; Mechanical engineering; Mechanical properties; Rock mechanics; Testing, Rocks, borehole; deformation; dilatancy; failure mechanism; mechanical property; microcrack; rock mechanics; triaxial test, Germany; Taiwan; United States
Abstract: ▾ An extensive true triaxial testing program was carried out on core samples from three ICDP-sponsored deep scientific boreholes, KTB (Germany), SAFOD (United States), and TCDP (Taiwan). The three rocks differ in the processes that formed them and in many of their mechanical properties. However, all three rocks exhibited similar failure mechanism, in which induced or reopened microcracks are primarily aligned with the σ1-σ2 plane, and the developed fault is steeply inclined in the σ3 direction. Rock strength in all tested rocks increases with σ2 when σ3 is kept constant. Thus, the common Mohr-type criteria, which ignore the effect of σ2, typically underestimate rock strength. Rather a 3D criterion that involves all three principal stresses represents well experimental results. Fracture plane slope for the same σ3 steepens as σ2 rises, contrary to Mohr-type criteria. With respect to deformation, the onset of dilatancy increases with σ2. In conclusion, true triaxial tests conducted on cores from three scientific boreholes, revealed important details of mechanical behavior not otherwise observed in conventional triaxial tests. In addition, they show mechanical behavior similarities as related to σ2 effect regardless of rock type. © 2010 Elsevier B.V.
1121.
Consistent trends in the true triaxial strength and deformability of cores extracted from ICDP deep scientific holes on three continents
Tectonophysics,
503
(1-2)
45-51
2011
ISSN: 00401951Keywords:▾
Dilatancy; Fault angle; Scientific boreholes; True triaxial strength; True triaxial testing, Deformation; Mechanical engineering; Mechanical properties; Rock mechanics; Testing, Rocks, borehole; deformation; dilatancy; failure mechanism; mechanical property; microcrack; rock mechanics; triaxial test, Germany; Taiwan; United States
Abstract: ▾ An extensive true triaxial testing program was carried out on core samples from three ICDP-sponsored deep scientific boreholes, KTB (Germany), SAFOD (United States), and TCDP (Taiwan). The three rocks differ in the processes that formed them and in many of their mechanical properties. However, all three rocks exhibited similar failure mechanism, in which induced or reopened microcracks are primarily aligned with the σ1-σ2 plane, and the developed fault is steeply inclined in the σ3 direction. Rock strength in all tested rocks increases with σ2 when σ3 is kept constant. Thus, the common Mohr-type criteria, which ignore the effect of σ2, typically underestimate rock strength. Rather a 3D criterion that involves all three principal stresses represents well experimental results. Fracture plane slope for the same σ3 steepens as σ2 rises, contrary to Mohr-type criteria. With respect to deformation, the onset of dilatancy increases with σ2. In conclusion, true triaxial tests conducted on cores from three scientific boreholes, revealed important details of mechanical behavior not otherwise observed in conventional triaxial tests. In addition, they show mechanical behavior similarities as related to σ2 effect regardless of rock type. © 2010 Elsevier B.V.
1120.
Correlation between deep fluids, tremor and creep along the central San Andreas fault
Nature,
480
(7375)
87-90
2011
ISSN: 00280836Keywords:▾
mineral, amplitude; correlation; crust; data set; electrical resistivity; fluid; mantle; pressure effect, amplitude modulation; anisotropy; article; biogeographic region; chemical reaction; earthquake; electrical parameters; enzyme kinetics; friction; liquid; nonhuman; porosity; precipitation; priority journal; rock; salinity; san andreas fault; velocity; volcano, California; San Andreas; United States
Abstract: ▾ The seismicity pattern along the San Andreas fault near Parkfield and Cholame, California, varies distinctly over a length of only fifty kilometres. Within the brittle crust, the presence of frictionally weak minerals, fault-weakening high fluid pressures and chemical weakening are considered possible causes of an anomalously weak fault northwest of Parkfield. Non-volcanic tremor from lower-crustal and upper-mantle depths is most pronounced about thirty kilometres southeast of Parkfield and is thought to be associated with high pore-fluid pressures at depth. Here we present geophysical evidence of fluids migrating into the creeping section of the San Andreas fault that seem to originate in the region of the uppermost mantle that also stimulates tremor, and evidence that along-strike variations in tremor activity and amplitude are related to strength variations in the lower crust and upper mantle. Interconnected fluids can explain a deep zone of anomalously low electrical resistivity that has been imaged by magnetotelluric data southwest of the Parkfield-Cholame segment. Near Cholame, where fluids seem to be trapped below a high-resistivity cap, tremor concentrates adjacent to the inferred fluids within a mechanically strong zone of high resistivity. By contrast, subvertical zones of low resistivity breach the entire crust near the drill hole of the San Andreas Fault Observatory at Depth, northwest of Parkfield, and imply pathways for deep fluids into the eastern fault block, coincident with a mechanically weak crust and the lower tremor amplitudes in the lower crust. Fluid influx to the fault system is consistent with hypotheses of fault-weakening high fluid pressures in the brittle crust. © 2011 Macmillan Publishers Limited. All rights reserved.