During the summers of 1979 and 1980, the U.S. Geological Survey conducted field work in Katmai National Monument to assess the reservoir and source rock potential of stratigraphic units which project into the Shelikof Strait outer continental shelf. Six stratigraphic sections and two traverses of Jurassic, Cretaceous, and Tertiary rocks were measured and sampled. Samples were analyzed for porosity, permeability, geochemistry, and fossil age dates.

Rocks with the highest organic contents are from the Upper Jurassic Naknek Formation (late Kimmeridgian) and from the Upper Cretaceous Kaguyak Formation (Maestrichtian). Organic-rich rocks of these ages found along Hallo Bay also have a strong petroliferous odor. These rocks are part of a large, complex anticline which plunges northeast into Shelikof Strait. The anticline is flanked by the Tertiary West Foreland Formation, with Middle Jurassic Shelikof Formation near the axis. Lower Cretaceous rocks were found between the Naknek and Kaguyak Formations, including discovery of Valanginian and Albian rocks on this part of the Alaska Peninsula. Several unconformities were observed in the area, the most notable of which is between the Upper Jurassic Naknek Formation and the Upper Cretaceou Kaguyak Formation.

Upper Cretaceous sandstones of good reservoir quality were penetrated by the ARCO Lower Cook Inlet COST No. 1 well. Onshore, source rocks were found in both the Naknet Formation (upper part) and the Kaguyak Formation. Mapping of these units should reveal promising exploration targets in the Shelikof Strait OCS.

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