All ICDP Publications with Abstracts
From parent-sysfolder "Publications" + 2 folder-levels deep
1344.
Microbial community analysis of deeply buried marine sediments of the New Jersey shallow shelf (IODP Expedition 313)
FEMS Microbiology Ecology,
85
(3)
578-592
2013
ISSN: 01686496Keywords:▾
RNA 16S, abundance; biosphere; data set; gene; manganese; marine sediment; microbial community; organic carbon; polymerase chain reaction; porewater; seafloor; shallow soil; sulfate, archaeon; article; bacterium; biodiversity; Chloroflexi; classification; Crenarchaeota; deep biosphere; Deltaproteobacteria; Euryarchaeota; genetics; IODP; isolation and purification; microbiology; Miscellaneous Crenarchaeotal Group; phylogeny; sea; sediment; sediments; travel; United States, Crenarchaeota; deep biosphere; Euryarchaeota; IODP; Miscellaneous Crenarchaeotal Group; sediments, Archaea; Bacteria; Biodiversity; Chloroflexi; Crenarchaeota; Deltaproteobacteria; Euryarchaeota; Expeditions; Geologic Sediments; New Jersey; Oceans and Seas; Phylogeny; RNA, Ribosomal, 16S, New Jersey; United States, Anaerolineae; Archaea; Bacteria (microorganisms); Chloroflexi; Chloroflexi (class); Crenarchaeota; Euryarchaeota; Geobacteraceae; Lake Victoria marburgvirus
Abstract: ▾ The investigated deeply buried marine sediments of the shallow shelf off New Jersey, USA, are characterized by low organic carbon content and total cell counts of < 107 cells per mL sediment. The qPCR data for Bacteria and Archaea were in the same orders of magnitude as the total cell counts. Archaea and Bacteria occurred in similar 16S rRNA gene copy numbers in the upper part of the sediments, but Bacteria dominated in the lowermost part of the analyzed sediment cores down to a maximum analyzed depth of c. 50 meters below seafloor (mbsf). The bacterial candidate division JS1 and the classes Anaerolineae and Caldinilineae of the Chloroflexi were almost as highly abundant as the total Bacteria. Similarly high dsrA gene copy numbers were found for sulfate reducers. The abundance of the Fe(III) and Mn(IV) reducers comprising Geobacteraceae in the upper c. 15 mbsf correlated with concentrations of manganese and iron in the pore water. The isolated 16S rRNA gene sequences of Archaea in clone libraries could be allocated to the phyla Thaumarchaeota, Euryarchaeota, and Crenarchaeota with 1%, 14%, and 85%, respectively. The typical deep subsurface sediment-associated groups MBG-B, MBG-D, MCG, and SAGMEG were represented in the sediment community. MCG was the dominant group with a high diversity of the isolated 16S rRNA gene sequences. © 2013 Federation of European Microbiological Societies.
1343.
Eger Rift ICDP: An observatory for study of non-volcanic, mid-crustal earthquake swarms and accompanying phenomena
Scientific Drilling
(16)
93-99
2013
ISSN: 181689571342.
Impact-generated hydrothermal systems on Earth and Mars
Icarus,
224
(2)
347-363
2013
Abstract: ▾ It has long been suggested that hydrothermal systems might have provided habitats for the origin and evolution of early life on Earth, and possibly other planets such as Mars. In this contribution we show that most impact events that result in the formation of complex impact craters (i.e., >2-4 and >5-10. km diameter on Earth and Mars, respectively) are potentially capable of generating a hydrothermal system. Consideration of the impact cratering record on Earth suggests that the presence of an impact crater lake is critical for determining the longevity and size of the hydrothermal system. We show that there are six main locations within and around impact craters on Earth where impact-generated hydrothermal deposits can form: (1) crater-fill impact melt rocks and melt-bearing breccias; (2) interior of central uplifts; (3) outer margin of central uplifts; (4) impact ejecta deposits; (5) crater rim region; and (6) post-impact crater lake sediments. We suggest that these six locations are applicable to Mars as well. Evidence for impact-generated hydrothermal alteration ranges from discrete vugs and veins to pervasive alteration depending on the setting and nature of the system. A variety of hydrothermal minerals have been documented in terrestrial impact structures and these can be grouped into three broad categories: (1) hydrothermally-altered target-rock assemblages; (2) primary hydrothermal minerals precipitated from solutions; and (3) secondary assemblages formed by the alteration of primary hydrothermal minerals. Target lithology and the origin of the hydrothermal fluids strongly influences the hydrothermal mineral assemblages formed in these post-impact hydrothermal systems. There is a growing body of evidence for impact-generated hydrothermal activity on Mars; although further detailed studies using high-resolution imagery and multispectral information are required. Such studies have only been done in detail for a handful of martian craters. The best example so far is from Toro Crater (Marzo, G.A., Davila, A.F., Tornabene, L.L., Dohm, J.M., Fairèn, A.G., Gross, C., Kneissl, T., Bishop, J.L., Roush, T.L., Mckay, C.P. [2010]. Icarus 208, 667-683). We also present new evidence for impact-generated hydrothermal deposits within an unnamed ∼32-km diameter crater ∼350. km away from Toro and within the larger Holden Crater. Synthesizing observations of impact craters on Earth and Mars, we suggest that if there was life on Mars early in its history, then hydrothermal deposits associated with impact craters may provide the best, and most numerous, opportunities for finding preserved evidence for life on Mars. Moreover, hydrothermally altered and precipitated rocks can provide nutrients and habitats for life long after hydrothermal activity has ceased. © 2012 Elsevier Inc.
1341.
Late-interseismic state of a continental plate-bounding fault: Petrophysical results from DFDP-1 wireline logging and core analysis, Alpine Fault, New Zealand
Geochemistry, Geophysics, Geosystems,
14
(9)
3801-3820
2013
ISSN: 15252027
Publisher: Blackwell Publishing Ltd
Keywords:▾
Earthquakes; Electric properties; Geophysics; Grinding (comminution); Plates (structural components); Principal component analysis; Rock drilling; Structural geology; Well logging, Alpine Faults; DFDP-1; Earthquake cycles; Fault zone structures; Wireline logging, Faulting, core analysis; deep drilling; earthquake rupture; fault zone; principal component analysis; seismicity; well logging, Alpine Fault Zone; New Zealand; South Island
Abstract: ▾ We present a geophysical characterization at 0.1-100 m scales of a major plate-bounding continental fault in a late-interseismic state. The Alpine Fault produces MW∼8 earthquakes every 200-400 years and last ruptured in 1717 AD. Wireline geophysical logs and rock cores extending from one side of the Alpine Fault to the other were acquired in two boreholes drilled in 2011 at Gaunt Creek during the first phase of the Deep Fault Drilling Project (DFDP-1). These data document ambient conditions under which the next Alpine Fault earthquake will occur. Principal component analysis of the wireline logging data reveals that >80% of the variance is accounted for by electrical, acoustic, and natural gamma properties, and preliminary multivariate classification enables the lithologies of sections of missing core to be reconstructed from geophysical measurements. The fault zone exhibits systematic variations in properties consistent with common processes of progressive alteration and comminution near the principal slip zone, superimposed on different protolith compositions. Our observations imply that the fault zone has the opposite sense of elastic asymmetry at 0.1-100 m scales to that of the crustal-scale orogen imaged by remote geophysical methods. On the basis of the fault-zone scale asymmetry, the bimaterial interface model of preferred earthquake rupture directions implies a northeastward direction of preferred Alpine Fault rupture. On-going characterization of the structural and hydraulic architecture of the Alpine Fault will improve our understanding of the relationship between in situ conditions, earthquake rupture processes, and the hazards posed by future earthquakes. © 2013. American Geophysical Union. All Rights Reserved.
1340.
Impact of volcanism on the evolution of Lake Van I: Evolution of explosive volcanism of Nemrut Volcano (eastern Anatolia) during the past >400,000 years
Bulletin of Volcanology,
75
(5)
1-32
2013
ISSN: 02588900
Publisher: Springer Verlag
Keywords:▾
basin evolution; ignimbrite; lithostratigraphy; peralkaline rock; phenocryst; plinian eruption; rhyolite; tephra; trachyte; volcanic eruption; volcanism, Bitlis; Lake Van; Nemrut; Turkey, Plinia; Trachytes
Abstract: ▾ The historically active Nemrut Volcano (2,948 m asl) (Eastern Anatolia), rising close to the western shore of huge alkaline Lake Van, has been the source of intense Plinian eruptions for >530,000 years (drilled lake sediments). About 40 widespread, newly recognized trachytic and less common rhyolitic fallout tephras and ca. 12 interbedded ignimbrites, sourced in Nemrut Volcano, are documented in stratigraphic traverses throughout an area of >6,000 km2 mostly west of Lake Van. Phenocrysts in the moderately peralkaline trachytes and rarer large-volume comenditic rhyolites comprise anorthoclase, hedenbergite-augite, fayalite and, especially in trachytic units, augite, minor aenigmatite, apatite and quartz, and rare chevkinite and zircon. Dacitic to rhyolitic tephras from nearby calcalkalic Süphan Volcano (4,058 m asl), locally interbedded with Nemrut tephras, are characterized by disequilibrium phenocryst assemblages (biotite, augitic clinopyroxene and hypersthene, minor olivine, common crystal clots and/or, in some deposits, amphibole). The magma volume (DRE) of the largest Nemrut tephra sheet (AP-1) described in detail may exceed 30 km3. Extreme facies and systematic compositional changes are documented in the ca. 30 ka Nemrut Formation (NF) deposits formed from one large and complex eruption (thick rhyolitic fallout overlain by ignimbrite, welded agglutinate, overbank surge deposits, and final more mafic fallout deposits). Common evidence of magma mixing in Nemrut ignimbrites reflects eruption from compositionally zoned magma reservoirs. Several young Çekmece Formation trachytes overlying ca. 30 ka old NF deposits and the late trachytes of the NF deposits show compositional affinities to tephra from Süphan Volcano possibly due to temporary influx of Süphan magmas into the Nemrut system following the evacuation of >10 km3 magma (DRE) during the caldera-forming NF eruption. Axes of large fallout fans are dominantly SW-NE but W-E in the younger sheets resembling the direction of the present dominant wind field. Growth of Nemrut volcanic edifice and its peripheral domes since before 0.5 Ma in the hinge area between the Van and Muş tectonic basins is likely to have been the major factor in isolating Lake Van basin thus initiating the origin and subsequent alkaline evolution of the lake. This alkalinity was later significantly controlled by climate forcing. Internal forcing mechanisms (volcanic and geodynamic) may also have contributed to major lake level changes in addition to climate forcing. © 2013 Springer-Verlag Berlin Heidelberg.
1339.
Geochemical consequences of widespread clay mineral formation in Mars' ancient crust
Space Science Reviews,
174
(1-4)
329-364
2013
Abstract: ▾ Clays form on Earth by near-surface weathering, precipitation in water bodies within basins, hydrothermal alteration (volcanic- or impact-induced), diagenesis, metamorphism, and magmatic precipitation. Diverse clay minerals have been detected from orbital investigation of terrains on Mars and are globally distributed, indicating geographically widespread aqueous alteration. Clay assemblages within deep stratigraphic units in the Martian crust include Fe/Mg smectites, chlorites and higher temperature hydrated silicates. Sedimentary clay mineral assemblages include Fe/Mg smectites, kaolinite, and sulfate, carbonate, and chloride salts. Stratigraphic sequences with multiple clay-bearing units have an upper unit with Al-clays and a lower unit with Fe/Mg-clays. The typical restriction of clay minerals to the oldest, Noachian terrains indicates a distinctive set of processes involving water-rock interaction that was prevalent early in Mars history and may have profoundly influenced the evolution of Martian geochemical systems. Current analyses of orbital data have led to the proposition of multiple clay-formation mechanisms, varying in space and time in their relative importance. These include near-surface weathering, formation in ice-dominated near-surface groundwaters, and formation by subsurface hydrothermal fluids. Near-surface, open system formation of clays would lead to fractionation of Mars' crustal reservoir into an altered crustal reservoir and a sedimentary reservoir, potentially involving changes in the composition of Mars' atmosphere. In contrast, formation of clays in the subsurface by either aqueous alteration or magmatic cooling would result in comparatively little geochemical fractionation or interaction of Mars' atmospheric, crustal, and magmatic reservoirs, with the exception of long-term sequestration of water. Formation of clays within ice would have geochemical consequences intermediate between these endmembers. We outline the future analyses of orbital data, in situ measurements acquired within clay-bearing terrains, and analyses of Mars samples that are needed to more fully elucidate the mechanisms of martian clay formation and to determine the consequences for the geochemical evolution of the planet. © 2012 Springer Science+Business Media B.V.
1338.
El'gygytgyn impact crater, Chukotka, Arctic Russia: Impact cratering aspects of the 2009 ICDP drilling project
Meteoritics and Planetary Science,
48
(7)
1108-1129
2013
ISSN: 10869379Abstract: ▾ The El'gygytgyn impact structure in Chukutka, Arctic Russia, is the only impact crater currently known on Earth that was formed in mostly acid volcanic rocks (mainly of rhyolitic, with some andesitic and dacitic, compositions). In addition, because of its depth, it has provided an excellent sediment trap that records paleoclimatic information for the 3.6 Myr since its formation. For these two main reasons, because of the importance for impact and paleoclimate research, El'gygytgyn was the subject of an International Continental Scientific Drilling Program (ICDP) drilling project in 2009. During this project, which, due to its logistical and financial challenges, took almost a decade to come to fruition, a total of 642.3 m of drill core was recovered at two sites, from four holes. The obtained material included sedimentary and impactite rocks. In terms of impactites, which were recovered from 316.08 to 517.30 m depth below lake bottom (mblb), three main parts of that core segment were identified: from 316 to 390 mblb polymict lithic impact breccia, mostly suevite, with volcanic and impact melt clasts that locally contain shocked minerals, in a fine-grained clastic matrix; from 385 to 423 mblb, a brecciated sequence of volcanic rocks including both felsic and mafic (basalt) members; and from 423 to 517 mblb, a greenish rhyodacitic ignimbrite (mostly monomict breccia). The uppermost impactite (316-328 mblb) contains lacustrine sediment mixed with impact-affected components. Over the whole length of the impactite core, the abundance of shock features decreases rapidly from the top to the bottom of the studied core section. The distinction between original volcanic melt fragments and those that formed later as the result of the impact event posed major problems in the study of these rocks. The sequence that contains fairly unambiguous evidence of impact melt (which is not very abundant anyway, usually less than a few volume%) is only about 75 m thick. The reason for this rather thin fallback impactite sequence may be the location of the drill core on an elevated part of the central uplift. A general lack of large coherent melt bodies is evident, similar to that found at the similarly sized Bosumtwi impact crater in Ghana that, however, was formed in a target composed of a thin layer of sediment above crystalline rocks. © The Meteoritical Society, 2013.
1337.
Ikaite precipitation in a lacustrine environment - implications for palaeoclimatic studies using carbonates from Laguna Potrok Aike (Patagonia, Argentina)
Quaternary Science Reviews,
7146 – 53
2013
Keywords:▾
Argentina; Laguna Potrok Aike; Santa Cruz [Argentina]; Calcium carbonate; Isotopes; Lakes; Lasers; Minerals; Oxygen; Sedimentary rocks; Aquatic environments; Atmospheric conditions; ICDP project PASADO; Oxygen isotope fractionations; Palaeoenvironmental reconstruction; Stable isotope fractionations; Stable isotopes; Stable oxygen isotopes; calcite; calcium carbonate; freezing; Holocene; ikaite; isotopic fractionation; lacustrine deposit; lacustrine environment; marine environment; oxygen isotope; paleoenvironment; precipitation (chemistry); reconstruction; sediment chemistry; stable isotope; temperature effect; Calcite
Abstract: ▾ The monoclinic mineral ikaite (CaCO3 · 6H2O) and its pseudomorphs are potentially important archives for palaeoenvironmental reconstructions. Natural ikaite occurs in a small temperature range near freezing point and is reported mainly from marine and only rarely from continental aquatic environments. Ikaite transforms to more stable anhydrous forms of CaCO3 after an increase in temperature or when exposed to atmospheric conditions. The knowledge about conditions for natural ikaite formation, its stable isotope fractionation factors and isotopic changes during transformation to calcite is very restricted. Here, for the first time, primary precipitation of idiomorphic ikaite and its calcite pseudomorphs are reported from a subsaline lake, Laguna Potrok Aike, in southern Argentina. The calculated stable oxygen isotope fractionation factor between lake water and ikaite-derived calcite (αPAI=1.0324 at a temperature of 4.1°C) is close to but differs from that of primarily inorganically precipitated calcite. Pseudomorphs after ikaite rapidly disintegrate into calcite powder that is indistinguishable from μm-sized calcite crystals in the sediment record of Laguna Potrok Aike suggesting an ikaite origin of sedimentary calcites. Therefore, the Holocene carbonates of Laguna Potrok Aike have the potential to serve as a recorder of past hydrological variation. © 2012 Elsevier Ltd.
1336.
Environment and climate of the last 51,000years - new insights from the Potrok Aike maar lake Sediment Archive Drilling prOject (PASADO)
Quaternary Science Reviews,
711 – 12
2013
Keywords:▾
Argentina; Laguna Potrok Aike; Santa Cruz [Argentina]; Climatology; Sedimentology; Argentina; Holocenes; ICDP; Lake levels; Last glacial; Patagonia; Southern Hemispheric Westerlies; Water balance; Holocene; interdisciplinary approach; lacustrine deposit; luminescence dating; maar; radiocarbon dating; Southern Hemisphere; twentieth century; water budget; Lakes
Abstract: ▾ In this introductory paper we summarize the history and achievements of the Potrok Aike maar lake Sediment Archive Drilling prOject (PASADO), an interdisciplinary project embedded in the International Continental Scientific Drilling Program (ICDP). The stringent multiproxy approach adopted in this research combined with radiocarbon and luminescence dating provided the opportunity to synthesize a large body of hydrologically relevant data from Laguna Potrok Aike (southern Patagonia, Argentina). At this site, lake level was high from 51ka until the early Holocene when the Southern Hemisphere Westerlies (SHW) were located further to the north. At 9.3kacal.BP the SHW moved southward and over the latitude of the study area (52°S) causing a pronounced negative water balance with a lake level decrease of more than 50m. Two millennia later, the SHW diminished in intensity and lake level rose to a subsequent maximum during the Little Ice Age. Since the 20th century, a strengthening of the SHW increased the evaporative stress resulting in a more negative water balance. A comparison of our data with other hydrological fluctuations at a regional scale in south-eastern Patagonia, provides new insights and also calls for better chronologies and high-resolution records of climate variability. © 2012 Elsevier Ltd.
1335.
Environmental/climate change in the Cretaceous greenhouse world: Records from Terrestrial scientific drilling of Songliao Basin and adjacent areas of China
Palaeogeography, Palaeoclimatology, Palaeoecology,
3851-5
2013
ISSN: 003101821334.
Evidence for high salinity of Early Cretaceous sea water from the Chesapeake Bay crater
Nature,
503
(7475)
252-256
2013
ISSN: 00280836Keywords:▾
ground water; sea water, bolide; coastal plain; crater; Cretaceous; dissolution; evaporite; groundwater; impact; osmosis; salinity; seawater, article; chemical analysis; coastal plain; dissolution; evaporation; heating; Lower Cretaceous; osmosis; priority journal; salinity; sediment; temperature, Atlantic Ocean; Bays; Geological Phenomena; Groundwater; Salinity; Seawater, Atlantic Coastal Plain; Chesapeake Bay; United States
Abstract: ▾ High-salinity groundwater more than 1,000 metres deep in the Atlantic coastal plain of the USA has been documented in several locations, most recently within the 35-million-year-old Chesapeake Bay impact crater. Suggestions for the origin of increased salinity in the crater have included evaporite dissolution, osmosis and evaporation from heating associated with the bolide impact. Here we present chemical, isotopic and physical evidence that together indicate that groundwater in the Chesapeake crater is remnant Early Cretaceous North Atlantic (ECNA) sea water. We find that the sea water is probably 100-145 million years old and that it has an average salinity of about 70 per mil, which is twice that of modern sea water and consistent with the nearly closed ECNA basin. Previous evidence for temperature and salinity levels of ancient oceans have been estimated indirectly from geochemical, isotopic and palaeontological analyses of solid materials in deep sediment cores. In contrast, our study identifies ancient sea water in situ and provides a direct estimate of its age and salinity. Moreover, we suggest that it is likely that remnants of ECNA sea water persist in deep sediments at many locations along the Atlantic margin. © 2013 Macmillan Publishers Limited. All rights reserved.
1333.
Extracting paleoclimate signals from sediment laminae: An automated 2-D image processing method
Computers and Geosciences,
52345 – 355
2013
ISSN: 00983004Keywords:▾
Ashanti; Ghana; Lake Bosumtwi; Algorithms; Image matching; Lakes; Laminating; Sedimentology; Sediments; Stratigraphy; 2-D laminae; Algorithm development; Best fit algorithm; Connectivity analysis; Contrast Enhancement; Depositional environment; Human errors; Image processing - methods; Labor intensive; Lake sediments; Lamina properties; Limnological conditions; Manual methods; Manual process; Paleoclimates; Quantitative attributes; Quantitative comparison; Sediment core; Signal-to-background ratio; Stratigraphic data; algorithm; identification method; image analysis; image processing; lacustrine deposit; paleoclimate; quantitative analysis; sediment core; Image processing
Abstract: ▾ Lake sediments commonly contain laminations and the occurrence and quantitative attributes of these microstrata contain signals of their depositional environment, limnological conditions, and past climate. However, the identification and measurement of laminae and their attributes remains a largely semi-manual process that is tedious, labor intensive, but subject to human error. Here, we present a method to automatically measure and accurately extract lamina properties from sediment core images. This method is comprised of four major components: (1) image enhancement that includes noise reduction and contrast enhancement to improve signal-to-background ratio and resolution of laminae; (2) identification of 1-D laminae for a user-chosen area in an image; (3) laminae connectivity analyses on the 1-D laminae to obtain a lamina stratigraphy; and (4) extraction and retrieval of the primary and derived lamination stratigraphic data. Sediment core images from Lake Hitchcock and Lake Bosumtwi were used for algorithm development and testing. Our experiments show a complete match between laminae produced by the software and manual process for images from Lake Hitchcock. Quantitative comparisons reveal an insignificant discrepancy in the number of laminae identified automatically by the software and manually by researchers, and in over 90% of the cases the position mismatch of individual laminae is less than one pixel between the software and the manual method for the experimental images from Lake Bosumtwi. © 2012 Elsevier Ltd.
1332.
Far-deep core archive and database
Frontiers in Earth Sciences,
7493-502
2013
ISSN: 18634621
Publisher: Frontiers
1331.
First results from HOTSPOT: The Snake River plain scientific drilling project, Idaho, U.S.A.
Scientific Drilling
(15)
36 – 45
2013
ISSN: 18168957
Publisher: Copernicus GmbH
Keywords:▾
Distributed computer systems; Infill drilling; Stratigraphy; Volcanoes; Basaltic volcanism; Continental crusts; Geophysical logging; Geothermal potential; Scientific drilling; Snake river plains; Surface expression; Thermal anomalies; Rivers
Abstract: ▾ HOTSPOT is an international collaborative effort to understand the volcanic history of the Snake River Plain (SRP). The SRP overlies a thermal anomaly, the Yellowstone-Snake River hotspot, that is thought to represent a deep-seated mantle plume under North America. The primary goal of this project is to document the volcanic and stratigraphic history of the SRP, which represents the surface expression of this hotspot, and to understand how it affected the evolution of continental crust and mantle. An additional goal is to evaluate the geothermal potential of southern Idaho. Project HOTSPOT has completed three drill holes. (1) The Kimama site is located along the central volcanic axis of the SRP; our goal here was to sample a long-term record of basaltic volcanism in the wake of the SRP hotspot. (2) The Kimberly site is located near the margin of the plain; our goal here was to sample a record of high-temperature rhyolite volcanism associated with the underlying plume. This site was chosen to form a nominally continuous record of volcanism when paired with the Kimama site. (3) The Mountain Home site is located in the western plain; our goal here was to sample the Pliocene-Pleistocene transition in lake sediments at this site and to sample older basalts that underlie the sediments. We report here on our initial results for each site, and on some of the geophysical logging studies carried out as part of this project.
1330.
Geochemical and isotopic characteristics of shallow groundwater within the Lake Qinghai catchment, NE Tibetan Plateau
Quaternary International,
313-31462 – 73
2013
ISSN: 10406182Keywords:▾
China; Qinghai; Qinghai Lake; Qinghai-Xizang Plateau; carbonate; concentration (composition); groundwater; hydrochemistry; hydrogen isotope; ion exchange; isotopic composition; isotopic ratio; lake water; lithology; nitrate; oxygen isotope; rainwater; recharge; river water; solute; spatial variation; strontium isotope; sulfide; weathering
Abstract: ▾ Major ions, isotopic ratios of strontium (87Sr/86Sr), hydrogen (δD) and oxygen (δ18O) of groundwater samples were analyzed to decipher spatial variation, controlling factors, solute sources, and the rechargesource of shallow groundwaters within the Lake Qinghai catchment. Shallow groundwaters in this area are slightly alkaline, with 97% being fresh water of good quality, though there are high concentrations of nitrate and sulfide in Buha and lakeside groundwaters. Most of the shallow groundwatersare of the Ca2+-HCO3- type, whereas part of groundwaters surrounding the lake (LS) belongs to the Na+-Cl- type as lake water (QHL). Groundwater geochemistry is controlled by regional lithological association, ion exchange, and mineral precipitation. The dissolved Sr concentrations and 87Sr/86Sr ratios vary from 1.0 to 15.6μmol/L, and from 0.709859 to 0.715779, respectively. The first quantitative calculation in groundwater using a forward model shows that 40% of dissolved Sr is from carbonate weathering, 33% from evaporite dissolution, 17% from silicate weathering, and the remainder from atmospheric input for the whole catchment. Carbonate weathering dominates groundwater geochemistry in Shaliu (SL), Hargai (HG) and Buha (BH) samples, while evaporite dissolution dominates LS and Daotang (DT) samples. δD and δ18O data show that rain water is the major recharge source of both river water and shallow groundwater within the Lake Qinghai catchment. Qinghai Lake water is characterized by Buha-type water, but its Sr geochemistry is different from the shallow groundwater due to carbonate precipitation. Although shallow groundwater contributes ~5% of the dissolved Sr to the QHL, groundwater must be taken into account when the chemistry and budget of lake water are characterized. © 2013 Elsevier Ltd and INQUA.
1329.
Geochemical and paleomagnetic variations in basalts from the wendell regional aquifer systems analysis (RASA) drill core: Evidence for magma recharge and assimilation-fractional crystallization from the central snake river plain, Idaho
Geosphere,
9
(5)
1319-1335
2013
ISSN: 1553040XKeywords:▾
aquifer; basalt; concentration (composition); fractional crystallization; igneous geochemistry; igneous intrusion; lava flow; magma; ocean island basalt; paleomagnetism; petrogenesis; tholeiite; trace element; volcanism, Idaho; Snake River Plain; United States
Abstract: ▾ The temporal and magmatic evolution of central Snake River Plain (SRP; Idaho, USA) olivine tholeiites erupted within the past 4 m.y. is evaluated here. This investigation correlates and merges both geochemical and paleomagnetic measurements to constrain the volcanic history recovered from the 340 m Regional Aquifer Systems Analysis (RASA) test well located near Wendell, Idaho. Only a handful of studies have accomplished this task of shedding light on the chemical stratigraphy of the SRP and the petrogenesis of basalts with depth, and therefore through time. Paleomagnetic relationships suggest that time breaks between individual lava flows represent a few years to decades, time breaks between flow groups represent at least a couple of hundred years or possibly much longer, while significant hiatuses in volcanism, revealed by thick sediment packages or polarity reversals (both are evidenced in this well), are inferred to last thousands to tens of thousands of years. Major element geochemistry from 52 basaltic lava flows demonstrates near primitive compositions (i.e., ~10 wt% MgO) and tholeiitic iron enrichment trends, similar to lavas from the eastern SRP. Trace element concentrations are similar to those of ocean island basalts, with enriched Ba and Pb, and light rare earth element (REE)/heavy REE ratios similar to those of many Neogene volcanics of the western Cordillera. When combined, we identify a total of 11 flow groups, which we also classify as fractionation or recharge on the basis of decreasing or increasing MgO weight percent with depth. Taking into consideration these trends, we review the potential recharge, fractionation, and assimilation processes that characterize much of SRP olivine tholeiite, and conclude that assimilation, in combination with fractional crystallization, is the dominant petrogenesis for the basalts in the central SRP. Although fractionation of Wendell parent magmas was accompanied by assimilation of crustal material, this could not have been assimilation of ancient cratonic crust. The geochemical cycles observed in this well are inferred to represent fractionation and recharge of basaltic magma from a series of sill-like layered mafic intrusions located in the middle crust, similar to what has been proposed for the processes that control the eruptive history of basalts in the eastern SRP. © 2013 Geological Society of America.
1328.
Gas hydrates - A new type of fossil fuel [Gazohydraty - Nowy rodzaj paliw kopalnych]
Przeglad Geologiczny,
61
(8)
452-459
2013
ISSN: 00332151
Publisher: Polish Geological Institute
Abstract: ▾ Unconventional hydrocarbon resources in last years draw the attention of petroleum geologists. Significant position take the gas hydrates, first of all due to occurrences in many regions of the world and the size of the potential resources. These accumulations are localized in Arctic regions with permafrost as well as offshore. First gas hydrate discovery occurred in Siberian gas field Messoyakha in permafrost zone and similar accumulations were found in Alaska. Offshore occurrences are located mainly on continental slope. Drillings and samples from permafrost and seabed provided vast amount of data concerned conditions of gas hydrates formation and concentration and allow to better constrain the volume of hydrate-bearing sediments and their gas yield. Resources of hydrocarbons contained in gas hydrate deposits represent a vast energy source potential. Still essential problem is to elaborate efficient commercial production technology. So far positive developments regard only laboratory or semi-commercial scale.
1327.
Geochemistry and geochronology of the jim sage volcanic suite, southern idaho: Implications for snake river plain magmatism and its role in the history of basin and range extension
Geosphere,
9
(6)
1681-1703
2013
ISSN: 1553040XKeywords:▾
Hydrothermal alterations; Isotopic composition; Lacustrine sediments; Metamorphic core complex; Off-axis magmatism; Snake river plains; Standard mean ocean waters; Vertical component, Basalt; Faulting; Geochronology; Hafnium; Isotopes; Lead; Neodymium; Rivers; Strontium; Volcanoes; Watersheds; Zircon, Granite, basalt; basin evolution; caldera; detachment fault; faulting; geochronology; hafnium; hydrothermal alteration; igneous geochemistry; ignimbrite; isotopic composition; lacustrine deposit; lava flow; magmatism; Miocene; oxygen isotope; range expansion; rhyolite; uranium-lead dating; volcanic eruption; zircon, Idaho; Raft River; Snake River Plain; United States, Tetraonidae
Abstract: ▾ The Jim Sage volcanic suite (JSVS) exposed in the Jim Sage and Cotterel Mountains of southern Idaho (USA) consists of two volcanic members composed of ~240 km3 of Miocene rhyolite lavas separated by an interval of lacustrine sediments. It is capped by rheomorphic ignimbrite and as much as 100 m of basaltic lava fl ows probably derived from the central Snake River Plain (SRP) province to the north. The occurrence of volcanic vents in the JSVS links the lava fl ows to their local eruptive centers, while the adjacent Albion-Raft River-Grouse Creek metamorphic core complex exposes ~3000 km2 of once deep-seated rocks that offer constraints on the composition of the potential crustal sources of these rhyolites. U-Pb zircon ages from the rhyolite lavas of the JSVS range from 9.5 to 8.2 Ma. The Miocene basalt of the Cotterel Mountains has an 87Sr/86Sri composition of 0.7066-0.7075 and εNd(i) = -3.7, and the rhyolite lavas of the JSVS have 87Sr/86Sri = 0.7114-0.7135 and εNd(i) values that range from -6.7 to -7.1. Zircon from the rhyolites of the JSVS range in δ18Ozr (Vienna standard mean ocean water, VSMOW) from -0.5‰ to 5.7‰ and have εHf(i) values ranging from -0.8 to -6.8. Based on geochronology, whole-rock major elements, trace elements, isotopes (Sr and Nd), and in situ zircon O and Hf isotopic compositions, we infer that the JSVS is genetically related to the central SRP province. The eruption of the low-δ18O rhyolites of the JSVS, outside of the main topographic extent of the SRP province (without the large calderas inferred for the SRP rhyolites) implies that there might be an alternative mechanism for the formation of the low-δ18O signature other than the proposed assimilation of hydrothermally altered caldera blocks. One suggestion is that the north to south propagation of SRP-type low-δ18O rhyolitic melt along the Albion fault led to off-axis magmatism. Another possibility is that there was prior and widespread (across a region wider than the SRP) hydrothermal alteration of the crust related to its earlier magmatic and faulting history. The eruption of SRP-type lavas in the hanging wall of an evolving metamorphic core complex helps us outline the role of the SRP magmatic province in the extensional evolution of the northeastern Basin and Range. The lavas of the JSVS imply the addition of basalt, related to the SRP hotspot, to the crust beneath the Raft River Basin that provided a heat source for crustal melting and weakening of the deep crust; this led to a vertical component of crustal fl ow and doming during extension, after the eruption of the 9.5-8.2 Ma JSVS rhyolites. This younger than 8.2 Ma component of vertical motion during faulting of the Miocene stratifi ed sequence of the Raft River Basin and the rotation of the Albion fault to shallower angles collectively resulted in the subhorizontal detachment structure imaged seismically beneath the Raft River Basin. © 2013 Geological Society of America.
1326.
Geomicrobiological investigations in subsaline maar lake sediments over the last 1500 years
Quaternary Science Reviews,
71119 – 130
2013
Keywords:▾
Argentina; Laguna Potrok Aike; Patagonia; Santa Cruz [Argentina]; Bacteria (microorganisms); Bacteria; Biogeochemistry; Biological materials; Deposits; Lakes; Methanation; Methane; Organic compounds; Sedimentology; DGGE; Early diagenesis; Laguna potrok aike; LIA; MCA; Methane production; Microbial activities; PASADO; Patagonia; Subsaline; bacterium; biosphere; colonization; community structure; environmental conditions; fermentation; lacustrine deposit; Little Ice Age; maar; methane; microorganism; organic matter; oxygen; population structure; salinity; sediment core; species diversity; temperature effect; water column; Sediments
Abstract: ▾ Living microorganisms inhabit every environment of the biosphere but only in the last decades their importance governing biochemical cycles in deep sediments has been widely recognized. Most investigations have been accomplished in the marine realm whereas there is a clear paucity of comparable studies in lacustrine sediments. One of the main challenges is to define geomicrobiological proxies that can be used to identify different microbial signals in the sediments. Laguna Potrok Aike, a maar lake located in Southeastern Patagonia, has an annually not stratifying cold water column with temperatures ranging between 4 and 10°C, and most probably an anoxic water/sediment interface. These unusual features make it a peculiar and interesting site for geomicrobiological studies. Living microbial activity within the sediments was inspected by the first time in a sedimentary core retrieved during an ICDP-sponsored drilling operation. The main goals to study this cold subsaline environment were to characterize the living microbial consortium; to detect early diagenetic signals triggered by active microbes; and to investigate plausible links between climate and microbial populations. Results from a meter long gravity core suggest that microbial activity in lacustrine sediments can be sustained deeper than previously thought due to their adaptation to both changing temperature and oxygen availability. A multi-proxy study of the same core allowed defining past water column conditions and further microbial reworking of the organic fraction within the sediments. Methane content shows a gradual increase with depth as a result of the fermentation of methylated substrates, first methanogenic pathway to take place in the shallow subsurface of freshwater and subsaline environments. Statistical analyses of DGGE microbial diversity profiles indicate four clusters for Bacteria reflecting layered communities linked to the oxidant type whereas three clusters characterize Archaea communities that can be linked to both denitrifiers and methanogens. Independent sedimentary and biological proxies suggest that organic matter production and/or preservation have been lower during the Medieval Climate Anomaly (MCA) coinciding with a low microbial colonization of the sediments. Conversely, a reversed trend with higher organic matter content and substantial microbial activity characterizes the sediments deposited during the Little Ice Age (LIA). Thus, the initial sediments deposited during distinctive time intervals under contrasting environmental conditions have to be taken into account to understand their impact on the development of microbial communities throughout the sediments and their further imprint on early diagenetic signals. © 2012 Elsevier Ltd.
1325.
Geophysical characterization of the Chicxulub impact crater
Reviews of Geophysics,
51
(1)
31-52
2013
Abstract: ▾ Geophysical data indicate that the 65.5 million years ago Chicxulub impact structure is a multi-ring basin, with three sets of semicontinuous, arcuate ring faults and a topographic peak ring (PR). Slump blocks define a terrace zone, which steps down from the inner rim into the annular trough. Fault blocks underlie the PR, which exhibits variable relief, due to target asymmetries. The central structural uplift is >10 km, and the Moho is displaced by 1-2 km. The working hypothesis for the formation of Chicxulub is: a 50 km radius transient cavity, lined with melt and impact breccia, formed within 10 s of the impact, and within minutes, weakened rebounding crust rose kilometers above the surface, the transient crater rim underwent localized deformation and collapsed into large slump blocks, resulting in a inner rim at 70-85 km radius, and outer ring faults at 70-130 km radius. The overheightened structural uplift collapsed outward, buried the inner slump blocks, and formed the PR. Most of the impact melt was ultimately emplaced as a coherent <3 km thick melt sheet within the central basin that shallows within the inner regions of the PR. Smaller pockets of melt flowed into the annular trough. Subsequently, slope collapse, ejecta, ground surge, and tsunami waves infilled the annular trough and annular basin with sediments up to 3 km and 900 m thick, respectively. Testing this working hypothesis requires direct observation of the impactites, within and adjacent to the PR and central basin. Key PointsA review of all geophysical data imaging ChicxulubSummary of the key features of the impact structureAn assessment of the relative timing of impact processes © 2013. American Geophysical Union. All Rights Reserved.
1324.
Granitic basement below Deccan Traps Unearthed by drilling in the Koyna seismic zone, Western India
Journal of the Geological Society of India,
81
(2)
289-290
2013
ISSN: 0974-68891323.
High-latitude environmental change during MIS 9 and 11: biogeochemical evidence from Lake El'gygytgyn, Far East Russia
Climate of the Past,
9
(2)
567-581
2013
ISSN: 18149324Keywords:▾
alga; biogeochemical cycle; biomarker; climate change; environmental change; greenhouse gas; interglacial; lacustrine deposit; latitude; marine isotope stage; temperature effect; vegetation, Arctic; Chukchi; Elgygytgyn Lake; Far East; Russian Federation
Abstract: ▾ Marine isotope stages (MIS) 11 has been proposed as an analog for the present interglacial; however, terrestrial records of this time period are rare. Sediments from Lake El'gygytgyn (67 300 N, 172 50 E) in Far East Russia contain a 3.56 Ma record of climate variability from the Arctic. Here, we present the first terrestrial Arctic reconstruction of environmental and climatic changes from MIS 8 through 12 (289 to 464 ka) using organic geochemical proxies. Terrestrial vegetation changes, as revealed by plant leaf wax (n-alkane) indices and concentrations of arborinol (a biomarker for trees), show increased tree cover around the lake during interglacial periods, with higher concentrations observed during MIS 11 as compared to MIS 9. A similar pattern is also observed in records of aquatic productivity revealed by molecular indicators from dinoflagellates (dinosterol), eustigmatophyte algae (long-chain (C28-C32) 1, 15 n-alkyl diols) in addition to short-chain n-alkanes, where aquatic productivity is highest during MIS 11. Changes recorded in these molecular proxies show a similar structure to relative temperature variability as recorded by the MBT/CBT (Methylation of Branched Tetraether/Cyclization of Branched Tetraether) paleothermometer, based on branched glycerol dialkyl glycerol tetraethers (GDGTs). Additionally, relative MBT/CBT temperature changes generally track pollen and diatom 18O temperature estimates, compiled by other studies, which suggest glacial-interglacial temperature changes of 9 to 12 C. These records of environmental and climatic change indicate Arctic sensitivity to external forcings such as orbital variability and atmospheric greenhouse gas concentrations. Overall, this study indicates that organic geochemical analyses of the Lake El'gygytgyn sediment archive can provide critical insight into the response of lake ecosystems and their sensitivity in high latitude regions. © Author(s) 2013.
1322.
High-resolution fault image from accurate locations and focal mechanisms of the 2008 swarm earthquakes in West Bohemia, Czech Republic
Tectonophysics,
590189 – 195
2013
ISSN: 00401951Keywords:▾
Bohemia; Czech Republic; Earthquakes; Stability; Earthquake location; Failure criteria; Fault friction; Focal mechanism; Tectonic stress; Coulomb criterion; earthquake event; earthquake hypocenter; earthquake magnitude; focal mechanism; image resolution; microearthquake; Faulting
Abstract: ▾ We have analyzed 463 micro-earthquakes in the magnitude range from 0.5 to 3.8 that occurred during the 2008 earthquake swarm in West Bohemia, Czech Republic, in order to screen the detailed structure of the focal zone situated at depths between 7 and 11. km. The double-difference location method was applied to records of 22 local seismic stations with an epicentral distance of less than 25. km in order to retrieve highly accurate locations of hypocenters with an accuracy of less than 20. m. The hypocenters are well-clustered and distinctly map the system of activated faults. The fault system has a complex geometry being composed of several fault segments with different orientations. Some of the segments intersect each other. The orientations of the segments coincide well with the focal mechanisms. We have introduced and evaluated the so-called fault instability of the individual fault segments. The fault instability ranges from 0 (most stable faults) to 1 (most unstable faults) and measures the susceptibility of the fault to be activated under specified stress. In the West Bohemia focal zone, two fault segments are optimally oriented with respect to the tectonic stress being characterized by an instability value higher than 0.9. Tractions on these fault segments are concentrated in the Mohr's diagram in the area of validity of the Mohr-Coulomb failure criterion and the associated micro-earthquakes are mainly shear. The other fault segments are slightly misoriented with instability values between 0.7 and 0.9, and the shear traction is significantly lower. These earthquakes are probably more tensile and activated most likely by the local redistribution of Coulomb stress during swarm activity. © 2013 Elsevier B.V.
1321.
High-resolution paleomagnetic secular variations and relative paleointensity since the Late Pleistocene in southern South America
Quaternary Science Reviews,
7191 – 108
2013
Keywords:▾
Argentina; Laguna Potrok Aike; Santa Cruz [Argentina]; South America; Lakes; Magnetization; Sedimentology; ICDP-project PASADO; Laguna potrok aike; Paleomagnetism; Relative paleointensity; Secular variation; Southern Hemisphere; geomagnetism; grain size; lacustrine deposit; paleomagnetism; Pleistocene; proxy climate record; reconstruction; resolution; secular variation; Southern Hemisphere; Geomagnetism
Abstract: ▾ Paleomagnetic inclination, declination and relative paleointensity were reconstructed from the sediments of Laguna Potrok Aike in the framework of the International Continental scientific Drilling Program (ICDP) Potrok Aike maar lake Sediment Archive Drilling prOject (PASADO). Here we present the u-channel-based full vector paleomagnetic field reconstruction since 51.2ka cal BP. The relative paleointensity proxy (RPI) was built by normalising the natural remanent magnetisation with the anhysteretic remanent magnetisation using the average ratio at 4 demagnetisation steps part of the ChRM interval (NRM/ARM10-40mT). A grain size influence on the RPI was removed using a correction based on the linear relationship between the RPI and the median destructive field of the natural remanent magnetisation (MDFNRM). The new record is compared with other lacustrine and marine records and stacks from the mid- to high-latitudes of the Southern Hemisphere, revealing consistent millennial-scale variability, the identification of the Laschamp and possibly the Mono Lake geomagnetic excursions, and a direction swing possibly associated to the Hilina Pali excursion at 20ka cal BP. Nonetheless, a global-scale comparison with other high-resolution records located on the opposite side of the Earth and with various dipole field references hint at a different behaviour of the geomagnetic field around southern South America at 46ka cal BP. © 2012 Elsevier Ltd.
1320.
Geochemical studies of the SUBO 18 (Enkingen) drill core and other impact breccias from the Ries crater, Germany
Meteoritics and Planetary Science,
48
(9)
1531-1571
2013
Abstract: ▾ Suevite and melt breccia compositions in the boreholes Enkingen and Polsingen are compared with compositions of suevites from other Ries boreholes and surface locations and discussed in terms of implications for impact breccia genesis. No significant differences in average chemical compositions for the various drill cores or surface samples are noted. Compositions of suevite and melt breccia from southern and northeastern sectors of the Ries crater do not significantly differ. This is in stark contrast to the published variations between within-crater and out-of-crater suevites from northern and southern sectors of the Bosumtwi impact structure, Ghana. Locally occurring alteration overprint on drill cores-especially strong on the carbonate-impregnated suevite specimens of the Enkingen borehole-does affect the average compositions. Overall, the composition of the analyzed impact breccias from Ries are characterized by very little macroscopically or microscopically recognized sediment-clast component; the clast populations of suevite and impact melt breccia are dominated consistently by granitic and intermediate granitoid components. The Polsingen breccia is significantly enriched in a dioritic clast component. Overall, chemical compositions are of intermediate composition as well, with dioritic-granodioritic silica contents, and relatively small contributions from mafic target components. Selected suevite samples from the Enkingen core have elevated Ni, Co, Cr, and Ir contents compared with previously analyzed suevites from the Ries crater, which suggest a small meteoritic component. Platinum-group element (PGE) concentrations for some of the enriched samples indicate somewhat elevated concentrations and near-chondritic ratios of the most immobile PGE, consistent with an extraterrestrial contribution of 0.1-0.2% chondrite-equivalent. © The Meteoritical Society, 2013.