Geochemical Significance of Gas and Gasoline-Range Hydrocarbons and Other Organic Matter in a Miocene Sample from Site 134—Balearic Abyssal Plain

Abstract

Gasoline-range hydrocarbons as well as gaseous ones are apparently seeping upward into immature, late Miocene, nonreservoir sediments in the area of Site 134 of the DSDP Leg 13 Mediterranean cruise. These conclusions are drawn from the results of geochemical analyses of a specially collected core sample. This sediment contains significant quantities of light hydrocarbons, but the rest of the organic matter appears to be so immature that it could not produce these light hydrocarbons, particularly the gasoline-range ones. Hence, the occurrence must be considered a minor but significant seepage from below. While not as spectacular as the show at Challenger Knoll (Gealy and Davies, 1969; Davis and Bray, 1969), this "show" is another indication that petroleum has already begun to form and migrate in some shallowly-buried deep-sea sediments.