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Methane sources feeding cold seeps on the shelf and upper continental slope off central Oregon, USA

Methane sources feeding cold seeps on the shelf and upper continental slope off central Oregon, USA
Methane sources feeding cold seeps on the shelf and upper continental slope off central Oregon, USA
We report on a bathymetric mapping and remotely operated vehicle surveys along the 100–600 m region offshore Oregon from 43°50?N to 44°18?N. We interpret our results in light of available geophysical data, published geotectonic models, and analogous observations of fluid venting and carbonate deposition from 44°30?N to 45°00?N. The methane seepage is defined by juxtaposition of a young prism, where methane is generated by bacterial activity and its release is modulated by gas hydrate dynamics, against older sequences that serve as a source of thermogenic hydrocarbons that vent in the shelf. We hypothesize that collision of a buried ridge with the Siletz Terrane results in uplift of gas hydrate bearing sediments in the oncoming plate and that the resulting decrease in pressure leads to gas hydrate dissociation and methane exolution, which, in turn, may facilitate slope failure. Oxidation of the released methane results in precipitation of carbonates that are imaged as high backscatter along a 550 ± 60 m benthic corridor.
seep carbonates, Heceta Bank, gas hydrate, methane seeps, Cascadia margin
1525-2027
Q11003
Torres, Marta E.
d00edf0b-fbd6-478c-b629-316b99fa179a
Embley, Robert W.
959cda85-5e89-493d-8207-a62678f059ed
Merle, Susan G.
142f95ca-7ffd-48ca-aa88-474b6191846d
Tréhu, Anne M.
aa4bc138-8705-43b1-86fb-be4a6192f619
Collier, Robert W.
69647a4a-0450-4177-a6be-b0112f98769c
Suess, Erwin
30a3311c-8c64-4fee-b361-f9c77f1e43c9
Heeschen, Katja U.
dfaa166c-5e40-4532-98d9-f7da49213713
Torres, Marta E.
d00edf0b-fbd6-478c-b629-316b99fa179a
Embley, Robert W.
959cda85-5e89-493d-8207-a62678f059ed
Merle, Susan G.
142f95ca-7ffd-48ca-aa88-474b6191846d
Tréhu, Anne M.
aa4bc138-8705-43b1-86fb-be4a6192f619
Collier, Robert W.
69647a4a-0450-4177-a6be-b0112f98769c
Suess, Erwin
30a3311c-8c64-4fee-b361-f9c77f1e43c9
Heeschen, Katja U.
dfaa166c-5e40-4532-98d9-f7da49213713

Torres, Marta E., Embley, Robert W., Merle, Susan G., Tréhu, Anne M., Collier, Robert W., Suess, Erwin and Heeschen, Katja U. (2009) Methane sources feeding cold seeps on the shelf and upper continental slope off central Oregon, USA. Geochemistry, Geophysics, Geosystems, 10, Q11003. (doi:10.1029/2009GC002518).

Record type: Article

Abstract

We report on a bathymetric mapping and remotely operated vehicle surveys along the 100–600 m region offshore Oregon from 43°50?N to 44°18?N. We interpret our results in light of available geophysical data, published geotectonic models, and analogous observations of fluid venting and carbonate deposition from 44°30?N to 45°00?N. The methane seepage is defined by juxtaposition of a young prism, where methane is generated by bacterial activity and its release is modulated by gas hydrate dynamics, against older sequences that serve as a source of thermogenic hydrocarbons that vent in the shelf. We hypothesize that collision of a buried ridge with the Siletz Terrane results in uplift of gas hydrate bearing sediments in the oncoming plate and that the resulting decrease in pressure leads to gas hydrate dissociation and methane exolution, which, in turn, may facilitate slope failure. Oxidation of the released methane results in precipitation of carbonates that are imaged as high backscatter along a 550 ± 60 m benthic corridor.

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More information

Published date: 5 November 2009
Keywords: seep carbonates, Heceta Bank, gas hydrate, methane seeps, Cascadia margin

Identifiers

Local EPrints ID: 69741
URI: http://eprints.soton.ac.uk/id/eprint/69741
ISSN: 1525-2027
PURE UUID: a8e14d4f-9f98-4ee6-be94-78530fc306e6

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Date deposited: 30 Nov 2009
Last modified: 13 Mar 2024 19:43

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Contributors

Author: Marta E. Torres
Author: Robert W. Embley
Author: Susan G. Merle
Author: Anne M. Tréhu
Author: Robert W. Collier
Author: Erwin Suess
Author: Katja U. Heeschen

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