The Quinault Formation, as recognized in this report, consists of moderately folded siltstone, sandstone, and conglomerate beds exposed mainly along the coast between Point Grenville and a point about one mile north of the mouth of the Raft River (Fig. 1, p. 2). Within this stretch of coastline four essentially continuous sections are exposed and are referred to in this report as follows: The section north of Point Grenville (exposed for some three-quarters of a mile north of Point Grenville) (Fig. 2, p. 6); the section south of Taholah (exposed for about one-half mile along the coast in an area about three-quarters of a mile south of the town of Taholah) (Fig. 3, p. 7); the Cape Elizabeth section (extending from the mouth of the Quinault River on the north to a point about one and one-quarter miles north of the Cape) (Fig. 4, p. 8); and the Duck Creek-Pratt Cliff section (extending from the mouth of Duck Creek to a point about three-quarters of a mile north of the north end of Pratt Cliff) (Fig. 5, p. 9).
The area along the coast occupied by these sections is regarded here as the type area of the Quinault Formation. A few small additional outcrops are also included several miles south of Point Grenville, and also in the vicinity of the mouth of the Raft River (Fig. 8, p. 13), but they are so small and so isolated that they represent no appreciable section. The eastern extent of the formation is not known in detail because thick Pleistocene (?) deposits cover much of the area, but nowhere are outcrops of the formation known more than 3 miles inland from the present coastline. To the west, the formation may well be far more extensive. Recent offshore geophysical investigations conducted by petroleum companies, as well as by Federal and university oceanographic research groups, suggest that strata both structurally and stratigraphically comparable to the Quinault Formation may underlie much of the Continental Shelf off the Washington coast. A number of wells have been drilled on or near the coast, and a few were situated offshore. Approximately 20 miles to the north of the Quinault River and nearly 20 miles offshore west of Destruction Island, a well drilled by Pan American Petroleum Corporation to a depth of 10,368 feet penetrated some 2,000 feet of strata that, based on foraminiferal studies by the writer, paleontologically can be correlated with at least parts of the onshore beds of the Quinault Formation. Southward along the coast, particularly in the Ocean City area some 20 miles south of the Quinault River, at least thirteen wells for which records are available have been drilled onshore and one approximately 2 miles offshore. All have penetrated some strata believed to be similar to the Quinault Formation. In some places these beds are at least 2,500 feet thick. Paleontologic evidence from a few of these wells verifies a correlation of these beds with the Quinault Formation of the type area. Several additional wells have been drilled offshore beyond 3 miles, but no information has been made available from them. Therefore, although exposures of the formation are largely confined to a narrow strip along the coast between Point Grenville and the Raft River, this evidence suggests that it is actually a rather widespread unit, mainly on the Continental Shelf and extending at least 20 miles to sea and for at least 40 miles along the coast.
Last Updated: 01-Jun-2006