(Table S1) Stable carbon isotope composition of dissolved inorganic carbon and Ion activity product of dolomite of IODP Exp 323 sites, supplement to: Wehrmann, Laura Mariana; Risgaard-Petersen, Nils; Schrum, Heather N; Walsh, Emily A; Huh, Youngsook; Ikehara, Minoru; Pierre, Catherine; d'Hondt, Steven L; Ferdelman, Timothy G; Ravelo, Ana Christina; Takahashi, Kozo; Zarikian, Carlos Alvarez (2011): Coupled organic and inorganic carbon cycling in the deep subseafloor sediment of the northeastern Bering Sea Slope (IODP Exp. 323). Chemical Geology, 284(3-4), 251-261

DOI

We studied microbially mediated diagenetic processes driven by carbon mineralization in subseafloor sediment of the northeastern Bering Sea Slope to a depth of 745 meters below seafloor (mbsf). Sites U1343, U1344 and U1345 were drilled during Integrated Ocean Drilling Program (IODP) Expedition 323 at water depths of 1008 to 3172 m. They are situated in the high productivity “Green Belt” region, with organic carbon burial rates typical of the high-productivity upwelling domains on western continental margins. The three sites show strong geochemical similarities. The downward sequence of microbially mediated processes in the sediment encompasses (1) organoclastic sulfate reduction, (2) anaerobic oxidation of methane (AOM) coupled to sulfate reduction, and (3) methanogenesis. The sediment contains two distinct zones of diagenetic carbonate formation, located at the sulfate–methane transition zone (SMTZ) and between 300 and 400 mbsf. The SMTZ at the three sites is located between 6 and 9 mbsf. The upward methane fluxes into the SMTZ are similar to fluxes in SMTZs underlying high-productivity surface waters off Chile and Namibia. Our Bering Sea results show that intense organic carbon mineralization drives high ammonium and dissolved inorganic carbon (DIC) production rates (> 4.2 mmol/m**3/y1) in the uppermost 10 mbsf and strongly imprints on the stable carbon isotope composition of DIC, driving it to a minimum value of -27 per mil (VPDB) at the SMTZ. Pore-water calcium and magnesium profiles demonstrate formation of diagenetic Mg-rich calcite in the SMTZ. Below the SMTZ, methanogenesis results in 13C-enrichment of pore-water DIC, with a maximum value of +11.9 per mil. The imprint of methanogenesis on the DIC carbon isotope composition is evident down to a depth of 150 mbsf. Below this depth, slow or absent microbially mediated carbon mineralization leaves DIC isotope composition unaffected. Ongoing carbonate formation between 300 and 400 mbsf strongly influences pore-water DIC and magnesium concentration profiles. The linked succession of organic carbon mineralization and carbonate dissolution and precipitation patterns that we observe in the Bering Sea Slope sediment may be representative of passive continental margin settings in high-productivity areas of the world's ocean.

Identifier
DOI https://doi.org/10.1594/PANGAEA.780181
Related Identifier https://doi.org/10.1016/j.chemgeo.2011.03.002
Metadata Access https://ws.pangaea.de/oai/provider?verb=GetRecord&metadataPrefix=datacite4&identifier=oai:pangaea.de:doi:10.1594/PANGAEA.780181
Provenance
Creator Wehrmann, Laura Mariana; Risgaard-Petersen, Nils; Schrum, Heather N; Walsh, Emily A; Huh, Youngsook; Ikehara, Minoru; Pierre, Catherine; d'Hondt, Steven L; Ferdelman, Timothy G; Ravelo, Ana Christina; Takahashi, Kozo; Zarikian, Carlos Alvarez
Publisher PANGAEA - Data Publisher for Earth & Environmental Science
Publication Year 2011
Rights Creative Commons Attribution 3.0 Unported
OpenAccess true
Representation
Language English
Resource Type Supplementary Dataset
Format text/tab-separated-values
Size 508 data points
Discipline Earth System Research
Spatial Coverage (-179.470W, 57.557S, -175.816E, 60.153N); Bering Sea
Temporal Coverage Begin 2009-08-07T00:00:00Z
Temporal Coverage End 2009-08-25T00:00:00Z