HR: 13:40h
AN: OS42B-01 INVITED     [PDF]
TI: Global Occurrences of Marine Gas Hydrate Beyond Active and Passive Continental Margins
AU: * Kvenvolden, K A
EM: kkvenvolden@usgus.gov
AF: US Geological Survey, 345 Middlefield Road, MS-999, Menlo Park, CA 94025 United States
AB: Natural gas hydrate occurs worldwide in oceanic sediment mainly in slopes and rises of active and passive continental margins. The Blake Outer Ridge, a passive margin in the Atlantic Ocean, and Hydrate Ridge, an active margin in the Pacific Ocean, are two regions of gas-hydrate occurrence that are particularly well studied. But gas hydrate occurs in other geologic settings where conditions of temperature, pressure, and amount and composition of gas and water are appropriate. For example, gas hydrate has been recovered from inland seas and lakes (Black Sea, Caspian Sea, and Lake Baikal). Gas hydrate has been inferred, based mainly on geophysical evidence, to be present in sediment of the Central Argentine Basin, the Bering Sea, and the Barents Sea. Submarine mud volcanoes such as Haakon Mosby in the Norwegian Sea and Kula in the Mediterranean Sea have yielded samples of gas hydrate, and near-surface sediment of the Gulf of Mexico contains gas hydrate associated with submarine gas vents. In fact, submarine gas hydrate was first observed by Russian scientists about thirty years ago when near-surface sediment recovered from the Black Sea was found to contain micro-crystalline aggregates of gas hydrate resembling hoarfrost. Most marine gas hydrate contains micorbially-generated methane; however, thermogenic methane has been observed in gas hydrate from the Gulf of Mexico and the Caspian Sea. Although most marine gas hydrate is found in sediment of active and passive margins, various occurrences beyond these margins demonstrate how globally extensive natural gas-hydrate phenomena actually are.
DE: 1055 Organic geochemistry
DE: 4806 Carbon cycling
DE: 4820 Gases
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting