Implications of carbon flux from the Cascadia accretionary prism; results from long-term, in situ measurements at ODP Site 892B

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doi: 10.1016/S0025-3227(03)00099-9
Author(s): Carson, Bobb; Kastner, Miriam; Bartlett, Douglas; Jaeger, John; Jannasch, Hans; Weinstein, Yishai
Author Affiliation(s): Primary:
Lehigh University, Department of Earth and Environmental Sciences, Bethlehem, PA, United States
Other:
GEOMAR, Federal Republic of Germany
Renard Centre for Marine Geology, Belgium
Scripps Institution of Oceanography, United States
University of Florida, United States
Monterey Bay Aquarium Research Institute, United States
Volume Title: Geosphere-biosphere coupling; cold seep related carbonate and mound formation and ecology
Volume Author(s): van Weering, Tjeerd C. E., editor; Dullo, Wolf-Christian; Henriet, Jean-Pierre
Source: Marine Geology, 198(1-2), p.159-180; American Geophysical Union, 2000 fall meeting, special session on Geosphere-biosphere coupling; cold seep related carbonate and mound formation and ecology, San Francisco, CA, Dec. 15-19, 2000, edited by Tjeerd C. E. van Weering, Wolf-Christian Dullo and Jean-Pierre Henriet. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0025-3227 CODEN: MAGEA6
Note: In English. 81 refs.; illus., incl. 2 tables, sketch map
Summary: A 403-day in situ field experiment at Ocean Drilling Program Site 892B sought to quantify the flux of methane along a fluid-active fault and to experimentally determine rates of methane hydrate and authigenic carbonate deposition associated with fluid expulsion from the borehole. An instrument package was deployed that osmotically sampled fluid, measured borehole pressure and flow rates, and contained reaction chambers in which deposition of gas hydrates and carbonates was anticipated, and from which microbial communities might be extracted. Flow is highly variable in the three-phase water-methane system that exists at Site 892B. Flow rates fluctuate over two orders of magnitude in response to tidally induced pressure variations and gas hydrate formation and dissociation. Hydrate formation began 45 days into the experiment and reduced the initial flow (∼2 l/day) to 20 ml/day. Unexpectedly, the hydrate destabilized after about 125 days. Tidally induced flow reversals are common (∼25% of time) in this setting characterized by "overpressured" pore waters. These reversals pump sulfate-rich bottom water into near-surface sediments where Archaea anaerobically oxidize CH4 and induce carbonate precipitation. At the sediment-water interface, authigenic carbonates are undergoing dissolution. Methanotrophs dominated the microbial community where fluid is discharged to ambient seawater. All expelled methane is apparently oxidized in the water column. Abstract Copyright (2003) Elsevier, B.V.
Year of Publication: 2003
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 07 Marine Geology and Oceanography; Accretionary wedges; Aliphatic hydrocarbons; Alkanes; Archaea; Bacteria; Biogenic processes; C-13/C-12; Carbon; Carbonates; Cascadia Basin; Chemical sedimentation; Chemosynthesis; Continental margin; East Pacific; Faults; Fluctuations; Gas hydrates; Gas seeps; Geochemistry; Hydrocarbons; Hydrochemistry; Isotope ratios; Isotopes; Leg 146; Marine sediments; Methane; Microorganisms; North Pacific; Northeast Pacific; ODP Site 892; Ocean Drilling Program; Oregon; Organic compounds; Oxidation; Pacific Ocean; Pore water; Sea water; Sedimentation; Sediments; Stable isotopes; United States
Coordinates: N444026 N444032 W1250705 W1250709
Record ID: 2003051040
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands