A bedrock dredging program by the R/V Sea Sounder in 1977 and 1978 along the continental slope in the eastern Gulf of Alaska revealed a previously unknown Eocene sedimentary sequence that includes argillaceous rocks with favorable petroleum source rock characteristics. Seven of 36 dredge hauls that sampled outcrop contain argillaceous rocks with more than l percent and as much as 1.64 percent organic carbon. Some of the rocks in samples of probable early Eocene age have undergone a thermal history that has resulted in generation of hydrocarbons. The organic matter appears to be hydrogen deficient, however, which could indicate that the rocks are more likely to be a source of gas rather than liquid hydrocarbon, unless the hydrogen loss is due to weathering.
The Eocene rocks are associated with sandstone and conglomerate on the continental slope. They dip northward beneath younger Tertiary strata in the outer continental shelf where they could be an important petroleum source and exploratory target.