To date the Deep Sea Drilling Project has revealed migrated liquid hydrocarbons in 3 widely separate areas of the globe. The first occurrence was the highly publicized, visually observed accumulation of immature petroleum in sediments on the Challenger Knoll in the Gulf of Mexico. Subsequent to the discovery of this obvious saturation, chemical analyses revealed 2 more possible examples of migration. The first was a low-grade bitumen saturation in a thin porous zone in Pleistocene sediments on the Shatsky Rise in the western Pacific Ocean. The second and latest was a small but geochemically significant quantity of wet gas and gasoline-range hydrocarbon that apparently seeped upward into Miocene rocks in the Balearic basin of the western Mediterranean Sea. These migrated h drocarbons--in addition to the methane gas commonly encountered in deep ocean cores--reveal that hydrocarbon source beds are present, and that liquids as well as gases have begun to migrate, at least locally, in deep-ocean sediments.

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