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Multiple deployments of a pressurized core barrel (PCB) during drilling of DSDP-IPOD Site 533A on the Blake-Bahama Outer Ridge has provided conclusive evidence for the presence of gas hydrate in sediments exhibiting a well-defined bottom simulating reflector. Pressure decline curves monitored during degassing and sampling of two pressurized sediments clearly indicate a pressure plateau at about 1,500 kPa resulting from gas hydrate decomposition. The pressure decline curve also includes a region attributable to hydrostatic pressure and a sediment degassing region. The molecular compositions of volatile hydrocarbons in PCB gas samples were characterized by (a) less than 2% variation in the C₁/C₂ ratio during pressure release, (b) a fourfold increase in C₃6 hydrocarbons over the duration of the experiment, and (c) a tenfold increase in CO₂ content of the expelled gases. Gas hydrate solids were recovered from Core 13-1 (~ 238 m depth) in sufficient quantity to permit several pressure/volume measurements. Gas expansion of the solids was measured at 13:1. Mole ratio of water to gas was found to be 50:1 after correcting for pore fluid content. Sediments remaining after gas hydrate decomposition were 93% H₂O by weight. Most of the water contained in the sediments appeared to be associated with the gas hydrate. The hydrates recovered were extremely fine grained and decomposed rapidly upon removal from in-situ pressures and temperatures.

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