Location and hydrocarbon content of a gravity core from the offshore Eel River basin, northern California

The core was collected from ponded sediment near the crest of a diapir-like feature on the Eel Plateau. The measured hydrocarbons are likely to have been derived from deep in the Neogene sedimentary section of the Eel River Basin. Their presence at the surface may indicate migration along fractures in or bordering the diapiric feature and seepage into unconsolidated sediments that are ponded locally within structural and bathymetric depressions. The extent of low molecular weight hydrocarbons at or near the-surface elsewhere in the basin is unknown, but the information based on hydrocarbon composition obtained at this site indicates the possibility that thermogenically-derived hydrocarbons have formed and accumulated in the sedimentary rocks of the offshore Eel River Basin.