Show simple item record

dc.contributor.authorPohlman, John W.  Concept link
dc.contributor.authorRuppel, Carolyn D.  Concept link
dc.contributor.authorHutchinson, Deborah R.  Concept link
dc.contributor.authorDowner, R.  Concept link
dc.contributor.authorCoffin, Richard B.  Concept link
dc.date.accessioned2008-12-30T15:00:22Z
dc.date.available2008-12-30T15:00:22Z
dc.date.issued2008-05-10
dc.identifier.citationMarine and Petroleum Geology 25 (2008): 942-951en
dc.identifier.urihttps://hdl.handle.net/1912/2618
dc.descriptionThis paper is not subject to U.S. copyright. The definitive version was published in Marine and Petroleum Geology 25 (2008): 942-951, doi:10.1016/j.marpetgeo.2008.01.016.en
dc.description.abstractPore waters extracted from 18 piston cores obtained on and near a salt-cored bathymetric high in Keathley Canyon lease block 151 in the northern Gulf of Mexico contain elevated concentrations of chloride (up to 838 mM) and have pore water chemical concentration profiles that exhibit extensive departures (concavity) from steady-state (linear) diffusive equilibrium with depth. Minimum δ13C dissolved inorganic carbon (DIC) values of −55.9‰ to −64.8‰ at the sulfate–methane transition (SMT) strongly suggest active anaerobic oxidation of methane (AOM) throughout the study region. However, the nonlinear pore water chemistry-depth profiles make it impossible to determine the vertical extent of active AOM or the potential role of alternate sulfate reduction pathways. Here we utilize the conservative (non-reactive) nature of dissolved chloride to differentiate the effects of biogeochemical activity (e.g., AOM and/or organoclastic sulfate reduction) relative to physical mixing in high salinity Keathley Canyon sediments. In most cases, the DIC and sulfate concentrations in pore waters are consistent with a conservative mixing model that uses chloride concentrations at the seafloor and the SMT as endmembers. Conservative mixing of pore water constituents implies that an undetermined physical process is primarily responsible for the nonlinearity of the pore water-depth profiles. In limited cases where the sulfate and DIC concentrations deviated from conservative mixing between the seafloor and SMT, the δ13C-DIC mixing diagrams suggest that the excess DIC is produced from a 13C-depleted source that could only be accounted for by microbial methane, the dominant form of methane identified during this study. We conclude that AOM is the most prevalent sink for sulfate and that it occurs primarily at the SMT at this Keathley Canyon site.en
dc.description.sponsorshipThis work was supported by DOE’s National Energy Technology Laboratory, the Office of Naval Research, and the Naval Research Laboratory. J.W.P was supported by a USGS Mendenhall Postdoctoral Research Fellowship Program during preparation of this manuscript.en
dc.format.mimetypeapplication/pdf
dc.language.isoen_USen
dc.publisherElsevier B.V.en
dc.relation.urihttps://doi.org/10.1016/j.marpetgeo.2008.01.016
dc.subjectGas hydrateen
dc.subjectMethaneen
dc.subjectAnaerobic methane oxidationen
dc.subjectSulfateen
dc.subjectBrineen
dc.subjectGulf of Mexicoen
dc.titleAssessing sulfate reduction and methane cycling in a high salinity pore water system in the northern Gulf of Mexicoen
dc.typeArticleen
dc.identifier.doi10.1016/j.marpetgeo.2008.01.016


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record