GAS-HYDRATE FORMATION AND LITHOGENESIS IN OCEAN SEDIMENTS

The demonstration of the presence of gas hydrates is a major finding of deep-water oceanic drilling. There is now no doubt that gas hydrates occur in the upper layers of sea floor sediments over considerable areas. Although hydrates have been observed directly in cores only in two regions (on the continental slope of the Central American Trench in the Pacific and on the Blake Outer Ridge in the Atlantic), the known and indicated occurrences of gas hydrates point to certain regularities. First, the hydrates are associated with continental slopes, where the combination of favorable thermobaric conditions and comparatively high contents of organic matter favors the biogenic generation of methane. Second, the hydrates do not completely fill the pore space in all beds within this zone, but appear to be under some lithologic control: larger amounts of hydrates occur in relatively coarse-grained beds such as tuffaceous and sandy horizons. In this paper, the authors point out analogies between ground ice on the continents and hydrate zones in marine sediments. 14 references.