Authigenic carbonate precipitates from the NE Black Sea: a mineralogical, geochemical, and lipid biomarker study

Bahr, André, Pape, T., Bohrmann, Gerhard, Mazzini, A., Haeckel, Matthias, Reitz, Anja and Ivanov, M. (2009) Authigenic carbonate precipitates from the NE Black Sea: a mineralogical, geochemical, and lipid biomarker study International Journal of Earth Sciences, 98 (3). pp. 677-695. DOI 10.1007/s00531-007-0264-1.

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Carbonate precipitates recovered from 2,000 m water depth at the Dolgovskoy Mound (Shatsky Ridge, north eastern Black Sea) were studied using mineralogical, geochemical and lipid biomarker analyses. The carbonates differ in shape from simple pavements to cavernous structures with thick microbial mats attached to their lower side and within cavities. Low δ13C values measured on carbonates (−41 to −32‰ V-PDB) and extracted lipid biomarkers indicate that anaerobic oxidation of methane (AOM) played a crucial role in precipitating these carbonates. The internal structure of the carbonates is dominated by finely laminated coccolith ooze and homogeneous clay layers, both cemented by micritic high-magnesium calcite (HMC), and pure, botryoidal, yellowish low-magnesium calcite (LMC) grown in direct contact to microbial mats. δ18O measurements suggest that the authigenic HMC precipitated in equilibrium with the Black Sea bottom water while the yellowish LMC rims have been growing in slightly 18O-depleted interstitial water. Although precipitated under significantly different environmental conditions, especially with respect to methane availability, all analysed carbonate samples show lipid patterns that are typical for ANME-1 dominated AOM consortia, in the case of the HMC samples with significant contributions of allochthonous components of marine and terrestrial origin, reflecting the hemipelagic nature of the primary sediment.

Document Type: Article
Keywords: Black Sea; AOM; Authigenic carbonates; Methane seepage; Dolgovskoy Mound
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
Refereed: Yes
DOI etc.: 10.1007/s00531-007-0264-1
ISSN: 1437-3254
Date Deposited: 13 Nov 2009 10:08
Last Modified: 18 May 2017 11:15

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