JANUABT 8, 1915] 



SCIENCE 



55 



greater contrast, not only in composition, 

 structure and age, but in mode of develop- 

 ment. 



The coast range of Oregon extends from 

 Cape Blanco in Oregon through Washing- 

 ton to the strait of Juan de Fuca, a dis- 

 tance of nearly 400 miles. At the southern 

 end it abuts against or rather runs into the 

 Klamath mountains without any sharp 

 topographic termination. At the north it 

 ends in the Olympic mountains of bold 

 relief, reaching an altitude of 8,150 feet, 

 but not quite reaching the height of the 

 Klamath-Mountains. South of the Columbia 

 along its crest are Onion Peak, Saddle 

 Mountain and Mary's Butte, of which sev- 

 eral are volcanic. 



On the whole the range is a unit but ir- 

 regular and, as compared with the Sierra 

 Nevada and coast range of California, is 

 characterized by its lack of effect upon 

 drainage. Although of small extent, it is 

 cut across by four rivers, the Umpqua, 

 Nehalen, Columbia and Chehalis. 



It is composed wholly of Mesozoic and 

 Tertiary rocks which at both ends abut 

 against those of the Paleozoic age. The 

 Franciscan series of sandstones, shales and 

 cherts of Franciscan age, with serpentine 

 and other intrusives, form a large part of 

 the Olympics and a portion of the south- 

 ern terminus of the range in Oregon, but 

 have not been recognized in intermediate 

 portions of the range. The same is true of 

 the Cretaceous, especially the Upper Cre- 

 taceous, which lies with marked uncon- 

 formity upon the rocks of Franciscan age 

 and thus records the great diastrophie 

 epoch of compression, probably about the 

 close of the Jurassic. 



The Cretaceous on the Pacific coast was 

 a time of subsidence so profound, at least 

 in one locality, as to result in the accumu- 

 lation of 29,000 feet of deposits in a mod- 

 erately shallow sea which transgressed the 



sinking land until it reached the base of 

 the Sierra Nevada. In Oregon there was 

 apparently a great embayment covering 

 not only the northern end of the Klamath 

 Mountains, but extending inland beyond 

 the Cascade range to the base of the Blue 

 Mountains. This great sinking embay- 

 ment, as it were in the lee of the Klamath 

 Mountains, the stable and insular terminus 

 of the Sierra Nevada, is an important fea- 

 ture of both the Cascade and the coast 

 ranges in Oregon. The steeper inclination 

 of the Cretaceous strata as compared with 

 the Eocene indicates their unconformity, 

 and the discordance is the greater in pro- 

 portion as the underlying Cretaceous is 

 older. 



The Eocene sandstones and shales, al- 

 though mainly marine, are in part of fresh 

 or brackish water accumulation and con- 

 tain locally more or less important deposits 

 of coal. They form the bulk of the coast 

 range in Oregon and southwest "Washing- 

 ton, and with them are associated in many 

 places contemporaneous volcanics, for the 

 most part basalts. 



A large part of the coast range in Ore- 

 gon and Washington south of the Olympics 

 was probably not raised above the ocean 

 before the close of the Eocene, but at that 

 time the elevation became somewhat more 

 pronounced, forming a low ridge which 

 with minor oscillations admitted the Mio- 

 cene sea through the gateway of the Che- 

 halis and Columbia into the Willamette 

 Valley. 



Toward the southern end, where the 

 Eocene contains some marine sandstones 

 derived from the near shore of the Kla- 

 math Mountains, the coast range is gently 

 synclinal. It presents a bold bluff with 

 even crest to the Umpqua Valley, possibly 

 due to a fault. Although, as a whole, the 

 coast range of Oregon has not been sub- 

 jected to as great compression as that of 



