GEOLOGY OF THE COASTAL REGION 459 



least the greater part of the Olympic mountains is composed of a hard 

 gray sandstone, certainly pre-Oligocene and probably Cretaceous in age. 



THE COASTAL REGION 



Geologic formations. — The formations involved in the geology of the 

 coastal region of the Olympic peninsula include serpentine, old diabase or 

 greenstone, metamorphosed sandstone and quartzite, probably of Jurassic 

 age ; 6,000+ feet of gray sandstone with minor quantities of carbonaceous 

 shales, supposed to represent the lower part of the Puget group and of 

 Cretaceous age; 1,200+ feet of basalt and basalt tuffs of Eocene age; 

 15,000 feet of Oligocene-Miocene conglomerate, sandstone, and shale; 

 2,260 feet of Pliocene conglomerate, sandstone, and shale, and at least 

 300 feet of Pleistocene till, clay, and gravel. In addition to this, the 

 Oligocene-Miocene breccia contains large quantities of angular fragments 

 of hard black slate, indicating a probable widespread formation of this 

 type of rock somewhere in the general region. Nothing is known of the 

 age of the slate except that it is pre-Oligocene. 



Supposed pre-Cretaceous. — The supposed pre-Cretaceous rocks of the 

 territory examined were confined entirely to the coast south of cape 

 Flattery, the most important areas occurring at Portage head, 8 miles 

 south of the cape, Point of the Arches, 3% miles still farther south, and 

 in the region from Point Greenville south to within a few miles of Grays 

 harbor. The types of rock composing this old series embrace old dia- 

 base or greenstone, serpentine, quartzite, conglomerate, etcetera. These 

 are much fractured and faulted and are occasionally cut by quartz veins, 

 some of which, in the Point of the Arches complex, are said to carry small 

 amounts of gold and silver. An interesting fact in relation to the con- 

 glomerate and serpentine in this same locality is the occurrence in them 

 of a high grade petroleum. Where freshly exposed, both the conglomerate 

 and serpentine give off a most nauseating odor, like that of benzine or 

 some other allied product. The occurrence of the oil is made the more 

 interesting when it is known that no shales or other possible oil-producing- 

 rocks outcrop in the immediate vicinity, although shales of probably 

 Oligocene or Miocene age are found something over a mile south of the 

 serpentine. 



Supposed Cretaceous. — The rocks supposed to be Cretaceous in age, 

 the correlation being based on their stratigraphic position and lithologic 

 character, are also confined to the western coast of the peninsula. They 

 extend over most of the territory from 1% miles south of Point of the 

 Arches to 1 mile north of cape Elizabeth, and consist almost entirely of a 



