306 research outputs found
(Table 1) Contents of biomarkers indicative for AOM-communities dominated by different ANME groups in two carbonate samples from Hydrate Hole pockmark
No full textThe abbreviation scheme used for the DAGEs is based on Elvert et al. (2005)
Lipid biomarker patterns of methane-seep microbialites from the Mesozoic convergent margin of California
No full textIn order to reconstruct biogeochemical pathways at Mesozoic methane-seeps, a set of Late Jurassic (Tithonian) to Early Cretaceous (Aptian/Albian), C-13-depleted seep-limestones from forearc strata in western California were subjected to detailed molecular-isotopic biomarker analyses. Two of the microbial carbonate deposits are turbidite-hosted/fault-related, whereas one is hosted in serpentinite in a diapir-related setting. The limestones contain 1 3 C-depleted archaeal lipid biomarkers such as crocetane (delta C-13 similar to -80 parts per thousand) and PMI (similar to -100 parts per thousand), indicative of an involvement of anaerobic oxidation of methane (AOM) in carbonate precipitation. Isotopically depleted crocetane in the Tithonian sample represents the oldest reported occurrence of this compound at methane-seeps. In the set of samples, a series of strongly C-13-depleted, regular C-21 to C-24 isoprenoids possibly results from diagenetic alteration of archaeal sesterterpanylglycerol diethers as suggested by the presence of the putative intermediate 3,7,11,15,19-pentamethylicosanoic acid. C-13-depleted 17 alpha(H),21 beta(H) and 17 beta(H),21 alpha(H)-hopanes (C-30-C-34) with 22S- and 22R- isomer couplets (> C-31) are present in all samples in distributions indicative of a moderate thermal maturity. Low delta C-13 values (-78 parts per thousand to -60 parts per thousand) suggest that these are derived from anaerobic bacteria involved in AOM. Notably, 22S-isomers are consistently enriched in C-13 relative to their 22R-counterparts. Our samples represent 70 myr of seepage activity and AOM along the Mesozoic margin of western California, filling the gap between the currently oldest methane-seep biomarker record from the Oxfordian (Late Jurassic) and the more widely recognised Cenozoic examples. (c) 2006 Elsevier Ltd. All rights reserved
Dissolved inorganic carbon and total organic carbon of surface samples from the Wadden Sea
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Natural and artificial radionuclides and organic geochemistry data of sediment core GeoB17409-1
No full textRadionuclide concentrations were studied in a sediment core GeoB17409-1 taken at the continental slope of the Philippine Sea off Mindanao Island in the equatorial Western Pacific. High resolution deposition records of anthropogenic radionuclides were collected at this site. Excess 210Pb together with excess 228Th and anthropogenic radionuclides provided information about accumulation rates. Concentrations of Am and Pu isotopes were detected by gamma spectrometry, alpha spectrometry and ICP-MS. The Pu ratios indicate a high portion (minimum of 60%) of Pu from the Pacific Proving Grounds (PPG). This implies that the transport of PPG derived plutonium with the Mindanao Current southward is similarly effective as the previously known transport towards the north with the Kuroshio Current. The record is compared to other studies from northwest Pacific marginal seas and Lombok basin in the Indonesian Archipelago.
The sediment core top was found to contain a 6 cm thick layer dominated by terrestrial organic matter, which was interpreted as a result of the 2012 Typhoon Pablo-related fast deposition
Substrate characteristic bacterial fatty acid production based on amino acid assimilation and transformation in marine surface sediments from the Wadden Sea, Germany
No full textPolar lipid-derived fatty acids (PLFAs) and their stable carbon isotopes are frequently combined to characterize microbial populations involved in the degradation of organic matter, offering a link to biogeochemical processes and carbon sources used. However, PLFA patterns derive from multiple species and may be influenced by substrate types. Here, we investigated such dependencies by monitoring the transformation of position-specifically 13C-labeled amino acids (AAs) in coastal marine sediments dominated by heterotrophic bacteria. Alanine was assimilated into straight-chain FAs, while valine and leucine incorporation led to the characteristic production of even- and odd-numbered iso-series FAs. This suggests that identical microbial communities adjust lipid biosynthesis according to substrate availability. Transformation into precursor molecules for FA biosynthesis was manifested in increased 13C recoveries of the corresponding volatiles acetate, isobutyrate and isovalerate of up to 39.1%, much higher than for PLFAs (<0.9%). A significant fraction of 13C was found in dissolved inorganic carbon (up to 37.9%), while less was recovered in total organic carbon (up to 17.3%). We observed a clear discrimination against the carboxyl C, whereby C2 and C3 positions were preferentially incorporated into PLFAs. Therefore, position-specific labeling is an appropriate tool for reconstructing the metabolic fate of protein-derived AAs in marine environments
(Table 2) Isotopic analyses from TVG 97
No full textCrust samples are Mg-calcite with 7 mol% MgCO3. Acharax samples are pure calcite
(Table 1) Carbonate mineralogical and isotopic analyses of carbonate subsamples from station TV-GKG 40
No full text(Table 1) Carbonate mineralogical and isotopic analyses of carbonate subsamples from station TV-GKG 4
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