Geological Survey Bulletin 581—B Oil and Gas in the Western Part of the Olympic Peninsula, Washington

ROCKS EXPOSED ALONG BOGACHIEL RIVER.

The rocks along Bogachiel River were examined at only five localities. The river was not traversed and the points visited are places where rock outcrop or indications of oil or gas were reported.

At location A, on the south side of the river, in the NW. 1/4 NW. 1/4 sec. 27, T. 28 N., R. 14 W., about a mile southwest of the Wilson place, which is described in detail on page 30, "smell mud" is very plentiful in a comparatively recent landslide 75 to 100 feet above the river level. At a point about one-fourth of a mile upstream from location A 6 feet of gray sandstone, which contains some carbonaceous material underlain by sandy shale, is exposed. These beds dip 37° SE., strike N. 34° E., and constitute the only known exposure of the "supposed Cretaceous" rocks for a mile or more both up and downstream. At location B, on the opposite side of the river, nearly flat-lying beds of poorly consolidated sand, clay, and gravel, which are believed to be of Pleistocene age, are exposed for several hundred feet. At location C, near the center of sec. 35, T. 28 N., R. 13 W., just north of the place where the trail from Forks to Bogachiel crosses Bear Creek, a very poor exposure of yellowish-gray argillaceous sandstone overlain by yellow clay shows that the strata dip about 36° SE. and strike N. 30° E. Beds of sandstone are exposed at location D, at the point where the trail referred to above crosses Coon Creek, in the NW. 1/4 sec. 26, T. 28 N., R. 13 W. At this locality beds of dark, resistant sandstone are exposed, but it was difficult to measure the dip and strike on account of the massive character of the rock. Apparently the rocks have a southeastward dip and seem to strike in the same general direction as the beds at location C, described above. Another exposure of rock was examined about one-half mile west of Morgan ranger station, at location E, in the NW. 1/4 sec. 5, T. 27 N., R. 12 W. The rocks here consist principally of gray sandstone overlain by blue shale which have a general dip of about 39° E. and strike N. 5° W. Joints and fractures which have been filled with quartz or calcite are numerous in the sandstone.

The rocks exposed at location A, 2 or 3 miles above the mouth of Bogachiel River, probably belong to the "supposed Cretaceous" formation so well exposed along the coast south of Hoh Head.

The strata exposed at locations C, D, and E, in the vicinity of the Bogachiel post office, probably are of Oligocene and Miocene age and belong to the Clallam formation, as suggested by Arnold.

Beds of Pleistocene clay, sand, and gravel unconformably overlie the older rocks throughout the greater part of this region. They outcrop extensively along Bogachiel River at location B, near Wilson's place, 6 or 7 miles southwest of Forks.