GAS HYDRATES FROM THE CONTINENTAL-SLOPE, OFFSHORE SAKHALIN ISLAND, OKHOTSK SEA

Ten gas-vent fields were discovered in the Okhotsk Sea on the northeas t continental slope offshore from Sakhalin Island in water depths of 6 20-1040 m. At one vent field, estimated to be more than 250 m across, gas hydrates. containing mainly microbial methane (deltaC-13 = -64.3 p arts per thousand), were recovered from subbottom depths of 0.3-1.2 m. The sediment, having lenses and bedded layers of gas hydrate, contain ed 30-40% hydrate per volume of wet sediment. Although gas hydrates we re not recovered at other fields, geochemical and thermal measurements suggest that gas hydrates are present.