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

ROCKS EXPOSED ALONG HUMPTULIPS RIVER, INCLUDING PARTS OF CAMP NO. 2 AND STEVENS CREEKS.

The rocks exposed along that part of the lower course of Humptulips River shown on Plate II (p. 78) and extending as far northeast as the bridge over the river about a mile above Humptulips post office are believed to consist entirely of poorly consolidated clay, sand, and gravel of Pleistocene age. The writer did not make a thorough examination of the lower course of this river, but at all points where the valley was examined these beds are exposed. A very careful examination of the strata was made along Camp No. 2 Creek for about a mile and a half above its mouth, which is about 2-1/2 miles above the junction of Big Creek with Humptulips River, at the extreme southern edge of the area represented on Plate II. The result of the examination along this creek definitely proves that the rocks are of the same age as those exposed along that part of the lower course of Humptulips River shown Plate II, namely, of Pleistocene age. These rocks on Camp No. 2 Creek consist of yellowish-brown conglomerate, with lenses of soft gray sandy clay alternating, immediately beneath soft bedded sandstone, with yellowish-gray sandy clay. Some of the gray sandy clay includes large numbers of fragments of stems of vegetation similar to grass. At one place a very distinct leaf was found in rather hard, yellowish sandy shale. The conglomerate consists of pebbles, probably derived from the metamorphic rocks and also probably from some of the "supposed Cretaceous" sandstones. This conglomerate is much cross-bedded and in places shows evidence of having been deposited by streams. At one locality a piece of lignite about 6 inches thick was found, but at no place along the stream between locations A and B is any lignite exposed in the walls of the valley. The beds lie practically flat, but at one place, about a mile southeast of location A, they dip 6° N. and strike approximately N. 70° W.

At location C, on Stevens Creek, in the NE. 1/4 sec. 7, T. 20 N., R. 10 W., an extensive outcrop of the Pleistocene beds occurs. These strata are about 75 feet thick and consist principally of poorly consolidated gravel and sand.

About 1-1/2 miles east of Humptulips, on the south side of Humptulips River and about one-third of a mile above the wagon bridge, at location D, there are beds of dark bluish-gray shale which contain thin lenses of iron-stained sandy material and numerous iron nodules. The nodules range from one-half to 1 inch in thickness and some of them are 2 feet in length. The outcrop at this place occurs in the edge of the stream and is entirely covered at high water. It is quite probable that these beds, which dip 69° NE. and strike N. 65° W., are of the same age as those along the coast which have been classed as "supposed Cretaceous."

In examining the outcrops along Humptulips River the writer did not follow the stream channel except in places but traversed mainly the wagon road from which he departed here and there to note the character of the rocks in the valley. At location E, at the bridge in the southern part of sec. 9, T. 20 N., R. 10 W., yellowish-brown fine grained argillaceous sandstone, somewhat massive in character, is exposed. Owing to the absence of definite bedding planes the dip and strike could not be determined. Just below the forks of Humptulips River, at location F, beds of Pleistocene age are well exposed along the north side of the river for several hundred yards. These beds lie practically flat and consist principally of a poorly consolidated conglomerate with some clay and a little lignite, as shown by the following section:

Pleistocene beds exposed at location F, just below the forks of Humptulips River.

The strata are fairly well exposed at a small falls at location G, in the south half of sec. 6, T. 20 N., R. 9 W., just north of the wagon road and a short distance south of Humptulips River. The rocks here consist of a coarse brownish sandstone which in places contains grains and small pebbles of greenish material one-tenth of an inch in diameter. The rocks exposed below the falls are probably 60 to 80 feet thick and are predominantly sandy but less resistant than the rocks directly overlying them. The strata dip 53° SE. and strike N. 65° E. At location H, just north of the wagon bridge over the east fork of Humptulips River, approximately in the SW. 1/4 sec. 5, T. 20 N., R. 9 W., a great thickness of bluish sandy shale with intercalated beds of shaly sandstone of the same color is exposed. Numerous slides and slumps have occurred here, but the loosened material has been carried away and the bedrock exposed by the frequent "splashings" and "sluicings" at the logging camps farther up the river. The beds dip about 55° SE. and strike N. 26° E. These rocks resemble very much the bluish sandy shale exposed on the beach near Copalis Rock (location A). Rocks having the same characteristics are exposed along the south side of the river in the southwestern part of sec. 5, T. 20 N., R. 9 W. At location I, in the NE. 1/4 sec. 5 of the same township, about 1-1/2 miles upstream from the wagon bridge, yellowish-gray sandstone and sandy shale that dip about 72° NE. and strike approximately N. 40° W. are exposed for a short distance. The easternmost outcrop of sedimentary rocks along the east fork of Humptulips River is at location J, in the NW. 1/4 sec. 35, T. 21 N., R. 9 W. These rocks, which are well exposed for a short distance along the north side of the wagon road, consist of gray sandy shale, dipping about 66° SW. and striking N. 35° W. This exposure is less than 100 feet west of what is believed to be the contact between the sedimentary and the igneous rocks. Northeastward from location J to East Fork dam (location K) the rocks exposed along the river and wagon road are igneous and are presumably older than those exposed farther west.

The oldest rocks examined along Humptulips River lie between locations J and K, in the southeastern part of T. 21 N., R. 9 W., and are believed to be of igneous origin. Along the river, between locations D and J, all the rocks examined are considered to be the equivalent of or possibly younger than the "supposed Cretaceous" rocks exposed along the coast in the vicinity of the mouth of Hoh River. The rocks exposed along the lower course of Humptulips River and its tributaries and also near the forks of the river consist of Pleistocene clay, sand, and gravel, and, in addition, these same materials cap all the older, more resistant rocks along the river valley. No indications of oil or gas in the form of oil seeps, gas vents, or "smell mud" are known to exist in this valley.