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

CHARACTER AND AGE OF THE ROCKS.

The surface rocks of the greater part of the area represented on Plate II consist of poorly consolidated clay, sand, and gravel of Pleistocene age. Rocks of the older formations are rarely exposed, except along the coast and the larger rivers. The smaller rivers and creeks in but few places have cut through this Pleistocene veneer except near the coast and the mountains, where it is comparatively thin.

The older rocks in the field, which are unconformably overlain by the Pleistocene material, as stated above, are exposed only along the coast and the larger streams. Arnold,¹ who examined the north coast and the greater part of the west coast of the Olympic Peninsula in 1904, classes the rocks outcropping on the west coast between the northern edge of the area shown on Plate II southward to a point about 1 mile north of Cape Elizabeth (location H), as "supposed Cretaceous." He states that they—

consist almost entirely of a coarse gray sandstone with occasional zones of black shale and rarely a little conglomerate. The thickness of the formation is probably over 5,000 feet, although, owing to its complex structure, this is only a very rough approximation. The series is characterized by calcite veins, which are abundant in nearly all of the exposures. The shales carry some lignite at two or three places, at one locality in particular the coal being used locally for domestic purposes.

---

¹Arnold, Ralph, Geological reconnaissance of the coast of the Olympic Peninsula, Wash.: Geol. Soc. America Bull., vol. 17, pp. 459 and 460, 1906.

---

He then continues with a discussion of evidences of oil in this formation, as quoted on page 26 of this paper.

In this same report Arnold¹ describes three formations—Crescent, Clallam, and Queniult—which lie between the "supposed Cretaceous" below and the unconformable, poorly consolidated Pleistocene beds above. The Crescent formation is assigned to the Eocene series and is described as consisting of "a 1,200-foot series of black basalt and greenish basalt tuffs and tufaceous sands found in the vicinity of Port Crescent" on the north coast.² No outcrops of this formation were recognized in the area shown on Plate II (p. 78).

---

¹Arnold, Ralph, op. cit., pp. 460-465.

²In a later report by Arnold and Harold Hannibal (The marine Tertiary stratigraphy of the north Pacific coast of America: Am. Philos. Soc. Proc., vol. 52, No. 212, p. 573, and correlation table opposite p. 604, 1913) the Crescent formation is considered to be the stratigraphic equivalent of the Arago formation.

---

The Clallam formation, which he assigned to the Oligocene and Miocene series, is described as follows:

Resting unconformably upon the Eocene and older rock of the Olympic Peninsula is a series of conglomerates, sandstones, and shales rich in fossils and extensive in occurrence. The formation is well exposed between Clallam Bay and Pillar Point to the east and for that reason is here named the Clallam formation. * * * A portion of the formation is unquestionably the equivalent of the Astoria sandstones and shales occurring at the mouth of the Columbia River, 130 miles farther south.

The rocks exposed in the hills south of Bogachiel River, according to Arnold, belong to the same formation. He also believes that the thickness of the formation in the vicinity of Cape Flattery is approximately 15,000 feet. Continuing the description of this formation at the type locality, Arnold states:

The conglomerates of the series are usually quite coarse and hard and consist of pebbles and cobbles of quartzite, jasper, black slate, and occasional granitics. They are found mostly at the base and near the top of the series along the straits and in the middle of the series on the Cape Flattery promontory. * * * The sandstones of the Clallam formation are for the most part thin bedded, hard, and resistant to erosion, and are extremely fossiliferous in certain localities, notably east of Clallam Bay. * * * The shale of the Oligocene-Miocene occurs principally in the middle of the formation along the strait (Juan de Fuca). The lower part of the shale is thinly and plainly laminated, but higher up becomes almost massive clay. * * * The shale is gray in fresh exposures, but becomes more or less oxidized upon exposure. * * * Coal occurs in the sandstones east of Clallam Bay, in the upper part of the Oligocene-Miocene series, and in the base of the same series in the vicinity of Freshwater Bay.

No coal of economic value is known to be present in the area rep resented on Plate II.

The Queniult formation, which Arnold assigns to the Pliocene,³ outcrops in—

a great syncline between Capes Elizabeth and Grenville, through the trough of which Queniult River empties into the sea. The formation in which this syncline is developed is therefore named the Queniult. The Queniult consists of over 2,200 feet of conglomerates and shale, with minor quantities of sandstone. The conglomerates are developed north of the river, while the shale with some underlying sandstone occurs south of it.

---

³In the report of Arnold and Hannibal, published in 1913 (op. cit., pp. 589, 591, 592, and table opposite P. 604), the Queniult formation is stated to be of Miocene and Pliocene age and to include the stratigraphic equivalents of the Empire and Merced formations.

---

Numerous fossils were collected by Arnold in both the Clallam and Queniult formations.

Unconformably overlying the Tertiary rocks above mentioned are the poorly consolidated beds of clay, sand, and gravel of Pleistocene age, which in places are 300 feet or more in thickness. Beds of very poor peatlike lignite occur in these rocks both along the coast and Queniult River.

Weaver,¹ in a preliminary report on this general region, published a map which shows that in his opinion the rocks outcropping on the west coast are principally "undifferentiated lower Miocene," with a few exposures of "pre-Tertiary metamorphics" and a formation of upper Miocene age which he designates the Montesano formation.

---

¹Weaver, C. E., A preliminary report on the Tertiary paleontology of western Washington: Washington Geol. Survey Bull. 15, Pl. A, 1912.

---

The writer collected but few fossils in the field and so has little information to add to the existing knowledge regarding the paleontology of the region. An attempt is made in the discussion of the various rock outcrops to correlate them with the formations named and described by Arnold, a summary of which is given above.

METHOD OF PRESENTATION OF THE GEOLOGIC DATA.

In the study of the stratigraphy as well as the structure of this field outcrops of rocks along the coast and in the valleys of the principal rivers were carefully examined at places indicated by letters on the map (Pl. II, p. 78). The structure at these places is shown by dip and strike symbols. Wherever anticlines or upfolds are present lines indicating their axes are shown. The anticlinal axes are not extended far from known outcrops.

It seems advisable in a report on this region, where information regarding the character and thickness of the formations is so meager, to describe the outcrops principally by districts rather than by formations and groups. So in the following discussion the writer has described the outcrops of rocks and their structure in regular order along the coast from south to north—from Copalis to a point about a mile north of Hoh Head—and along the streams from their mouths toward their sources. The rocks that outcrop on the coast are described first. Then follows the description of the rocks examined along the rivers and creeks. In describing these outcrops the stream valleys are considered in order from south to north as follows: Humptulips River, including parts of Camp No. 2 and Stevens creeks; Moclips River, Queniult River, Queets River, including parts of Salmon River and Mathney and Sams creeks; Clearwater River as far east as the west boundary of the Olympic National Forest, Hoh River, and parts of Bogachiel and Calawa rivers at the extreme north.