The Bristol Bay basin lies north of the Alaska Peninsula and south of the Ahklun Mountains west of Dillingham. The major part of the basin is offshore on the shallow-water shelf of the Bering See. The primary objectives are Tertiary rocks, which are mainly continental on the northeast end and marine on the southwest. Secondary objectives are marine rocks of Cretaceous and Jurassic age in the southwestern part of the basin southwest of Port Moller. Numerous potential structural and stratigraphic traps may be present in the Bristol Bay basin, which comprises 95,000 sq mi (246,050 sq km) and contains a sedimentary section possibly as thick as 16,000 ft (4,880 m). Major fields may be found both offshore and onshore. Probably the most favorable areas would be the transition zo e where Tertiary marine and nonmarine sedimentary rocks are inter-bedded and/or where the unmetamorphosed marine Cretaceous and Jurassic rocks lie at depths accessible to the drill.