296 research outputs found

    Oxygen-minimum zone sediments in the northeastern Arabian Sea Sea off Pakistan: a habitat for the bacterium Thioploca

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    Filamentous sulfur-oxidizing bacteria and geochemical parameters of sediments at the Makran accretionary wedge in the northeastern Arabian Sea off Pakistan were studied. The upper continental slope between 350 and 850 m water depth, which is in the center of the oxygen-minimum zone, is characterized by numerous sites of small-scale seeps of methane- and sulfide-charged porewater. White bacterial mats with diameters <1 m were discovered at the surface of these sites using a photo-TV sled. Seep sediments, as well as non-seep sediments, in the vicinity were characterized by the occurrence of the bacterium Thioploca in near-surface layers between 0 and 13 cm depth. Thioploca bundles were up to 20 mm in length and contained up to 20 filaments of varying diameters, between 3 and 75 ”m. Up to 169 ind. cm-2 were counted. Maximum numbers occurred in the top 9 cm of sediment, which contained very low concentrations of soluble sulfide (<0.2 ”M) and high amounts of elemental sulfur (up to 10 ”mol cm-3). Moderate sulfate reduction activity (between 20 and 190 nmol cm-3 d-1) was detected in the top 10 cm of these sediments, resulting in a gradual downcore decrease of sulfate concentrations. CO2 fixation rates had distinct maxima at the sediment surface and declined to background values below 5 cm depth. The nutritional implications of the distinct morphology of Thioploca and of the geochemical setting are discussed and compared to other sites containing Thioploca communities

    Mechanical stability of the CMS strip tracker measured with a laser alignment system

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    Two-particle azimuthal correlations in γp interactions using pPb collisions at √s^{s}NN = 8.16 TeV

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    Lithostratigraphy, diagenesis and paleoenvironment of the Cretaceous-Tertiary post-platform sediments of the Mazagan Escarpment (Morocco)

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    The lithostratigraphy and petrography of the thin Cretaceous-Tertiary cover of deeper-water sediments overlying the shallow-water Jurassic Mazagan carbonate platform were studies by microfacies analysis. The diagenesis of authigenic barite, zeolite, silica, dolomite, and the formation of calcite cement, phosphoritic, glauconitic, and ferromanganese crusts were also studied. The following facies associations were recognized: Early Cretaceous (?upper Berriasian to ?Hauterivian) sandy echinoderm-rich pack-to wackestones; Upper Aptian to Albian (-Cenomanian) hemipelagic nanno marlstones were only deposited at the foot of the paleo-escarpment during the mid-Cretaceous transgressions: Late Cretaceous sediments comprise (a) pelagic, bathyal nannomicrite (Santonian/Campanian), (b) limestone breccia, and (c) a heterogeneous suite of massive and laminated phosphorites, and phosphorite breccias; and Paleogene (Paleocene-Eocene) foraminiferal pack- and wackestones, as well as radiolarian chalks with chert nodules (?Eocene) were deposited in a pelagic slope environment
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