832 INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



quadrangle does not afford the best opportunity to determine the absolute age of the Tertiary 

 formations, nor their relation to one another. * * * 



In Philips burg Valley and Willow Creek valley there are exposures of light-colored silty 

 material shown by microscopic examination to be chiefly volcanic ash. These correspond in 

 character to beds well exposed near New Chicago, north of the quadrangle, in which Douglass 

 has collected vertebrate fossils that indicate a late Miocene age. * * * 



The soft, pale-tinted, obscurely stratified volcanic ash beds, presumably of Miocene age, 

 occur (1) at the north boundary of the quadrangle west of Flint Creek, (2) on Willow Creek near 

 the west border of the quadrangle, and (3) in Philipsburg Valley with its southern continua- 

 tion across the east fork of Rock Creek. These beds are perhaps the least resistant to erosion 

 and the most poorly exposed in the quadrangle, being rarely uncovered except on steep slopes 

 below the brinks of terraces capped by protecting gravel. Among the better exposures are 

 some about 3 miles northwest of Philipsburg, whose whitish tint makes them visible from the 

 town, and another in a gully about 1 mile north of Quinlan's ranch, at the head of Philipsburg 

 Valley. 



L-M 10. OliYMPIC PENINSULA, WASHINGTON. 



The reconnaissance of the coast of the Olympic Peninsula in 1904 by Arnold ^^ 

 led to the recognition of a formation covering parts of Oligocene and Miocene time, 

 the Clallam formation. Arnold says : 



Resting unconformably upon the Eocene and older rocks of the Olympic Peninsula is a 

 series of conglomerates, sandstones, and shales rich in fossils and extensive in occurrence. The 

 formation is well exposed in the region between Clallam Bay and Pillar Point, to the east, 

 and for that reason is here named the Clallam formation. According to Dr. Dall, the fossils 

 of the formation indicate that the basal portion of the series is Oligocene in age, while the upper 

 part is certainly Miocene. Since the separation of the two members will necessarily have to 

 be made on paleontologic grounds and will require a more detailed study of the material in hand 

 than time has yet permitted, the term " Oligocene-Miocene series" will be used temporarily 

 to designate the age of the beds. 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. 



All of the pre-Pleistocene deposits along Fuca Strait from Freshwater Bay to Cape 

 Flattery, with the exception of the Eocene basalts and tuffs of Crescent Bay and the Phocene 

 conglomerate and sandstone of the Clallam Bay-Hoko River region, belong to the Oligocene- 

 Miocene series, and at least the greater part and possibly the whole of the thick series of con- 

 glomerates, sandstones, and sliales exposed in the Cape Flattery promontory, and also the 

 sandstones and shales exposed in the hills south of the Bogochiel River, come under the same 

 head. The thickness of this series as exposed in sections along the strait, which, by the way, 

 virtually parallels the strike of the beds for most of the distance from Freshwater Bay to Neah 

 Bay, is about 3,650 feet. The Waatch-Neah Bay section, which cuts directly across the strike 

 of the great Cape Flattery monocline, exposes approximately 15,000 feet of conformable strata, 

 most and possijjly all of which may be Oligocene-Miocene. 



The conglomerates of the series are usually quite coarse and hard and consist of pebbles 

 and colables 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 zone of conglomerate in the middle of the Cape Flattery sec- 

 tion may be the equivalent of the basal conglomerates of the series as developed unconform- 

 ably above the Eocene around Crescent Bay. If so, the sandstones at the base of the Cape 

 Flattery section are older than any of the Ohgocene-Miocene beds exposed on the strait. The 

 base of the Cape Flattery section is unknown, as the lowest beds exposed in the section are 

 separated from the subjacent rocks by a fault. 



