Rise of the base of the gas hydrate zone since the last glacial recorded by rock magnetism

Gas hydrate, a clathrate of methane and water widespread on continental margins, has been implicated as a trigger of climate change and submarine slides as a result of methane release when the base of its stability zone moves upward rapidly. Direct tests of these hypotheses are made difficult by the...

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Bibliographic Details
Published in:Geology (Boulder) 2006-02, Vol.34 (2), p.117-120
Main Authors: Musgrave, Robert J, Bangs, Nathan L, Larrasoaña, Juan Cruz, Gràcia, Eulàlia, Hollamby, Jennifer A, Vega, Marta E
Format: Article
Language:English
Subjects:
aliphatic hydrocarbons
alkanes
applications
bottom-simulating reflectors
Cenozoic
Climate change
continental margin
depth
East Pacific
gas hydrates
Geology
geophysical methods
geophysical profiles
geophysical surveys
glacial environment
glaciomarine environment
high-resolution methods
Hydrate Ridge
hydrocarbons
last glacial maximum
Leg 204
magnetic hysteresis
Magnetism
marine environment
marine sediments
Methane
North Pacific
Northeast Pacific
Ocean Drilling Program
organic compounds
Pacific Ocean
paleoclimatology
paleomagnetism
porosity
Quaternary
Quaternary geology
sediments
seismic methods
seismic profiles
surveys
techniques
upper Quaternary
Water
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Summary:Gas hydrate, a clathrate of methane and water widespread on continental margins, has been implicated as a trigger of climate change and submarine slides as a result of methane release when the base of its stability zone moves upward rapidly. Direct tests of these hypotheses are made difficult by the ephemeral record of gas hydrate in sediment. In places, a seismic reflector (double bottom simulating reflector, BSR) appears to mark the old base of the gas hydrate layer, but the occurrence of this feature is patchy and its interpretation is controversial. Microbial activity is stimulated in the presence of gas hydrate, and results in the production of magnetic iron sulfides; the base of the gas hydrate interval is marked by a sharp reduction in the magnetic hysteresis parameter DJH. At Hydrate Ridge on the Cascadia margin, sampled during Ocean Drilling Program Leg 204, this signature occurs between 20 and 65 m below the present-day base of the gas hydrate zone, at a depth consistent with predictions for the base of gas hydrate stability given water depths and bottom-water temperatures appropriate for the last glacial maximum. Seismic evidence for a double BSR over part of Hydrate Ridge corroborates the rock magnetic interpretation.
ISSN:0091-7613
1943-2682
DOI:10.1130/G22008.1