Escape of methane gas through sediment waves in a large methane hydrate province

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doi: 10.1130/0091-7613(2002)030<0467:EOMGTS>2.0.CO;2
Author(s): Holbrook, W. S.; Lizarralde, D.; Pecher, I. A.; Gorman, A. R.; Hackwith, K. L.; Hornbach, M.; Saffer, D.
Author Affiliation(s): Primary:
University of Wyoming, Department of Geology and Geophysics, Laramie, WY, United States
Other:
Georgia Institute of Technology, United States
University of Texas at Austin, United States
Volume Title: Geology (Boulder)
Source: Geology (Boulder), 30(5), p.467-470. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0091-7613 CODEN: GLGYBA
Note: In English. 25 refs.; sects., sketch map
Summary: Despite paleoceanographic evidence that large quantities of methane have escaped from marine gas hydrates into the oceans, the sites and mechanisms of methane release remain largely speculative. New seismic data from the Blake Ridge, a hydrate-bearing drift deposit in the western Atlantic, show clear evidence for methane release and suggest a new mechanism by which methane gas can escape, without thermal or mechanical disruption of the hydrate-bearing layer. Rapid, post-2.5 Ma formation of large sediment waves and associated seafloor erosion created permeable pathways connecting free gas to the seafloor, allowing methane gas expulsion. The amount of missing methane, 0.6 Gt, is equivalent to ∼12% of total present-day atmospheric methane. Our results imply that significant amounts of methane gas can bypass the hydrate stability zone and escape into the ocean. Mechanisms of tapping methane directly from the free-gas zone, such as widespread seafloor erosion, should be considered when seeking the causes of large negative carbon isotope excursions in the geological record.
Year of Publication: 2002
Research Program: ODP Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; 20 Geophysics, Applied; Aliphatic hydrocarbons; Alkanes; Atlantic Ocean; Bathymetry; Bedding plane irregularities; Blake Ridge Depression; Blake-Bahama Outer Ridge; Bottom features; Bottom-simulating reflectors; Clastic sediments; Deep-sea sedimentation; Depressions; Drift; Erosion; Gas hydrates; Geophysical methods; Geophysical profiles; Geophysical surveys; Hydrocarbons; Marine sedimentation; Marine sediments; Methane; North Atlantic; Ocean floors; Organic compounds; Permeability; Sand waves; Sedimentary structures; Sedimentation; Sediments; Seismic methods; Seismic profiles; Surveys; Vents
Coordinates: N313600 N322400 W0751800 W0760000
Record ID: 2002035471
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