TERTIARY FAUNAS OF THE PACIFIC COAST 249 



correlation on a basis of diastrophism, unsupported by paleontologic 

 evidence, is extremely hazardous. 



CYCLES OF DIASTROPHISM 



The period of the Tertiary uplift of the last worldwide cycle of 

 diastrophism has been marked by two complete subcycles in the 

 Pacific Coast of North America. The first was begun with gradual 

 submergence in early Eocene, was continued by a gradual elevation 

 in the later Eocene when marine conditions gave place to brackish- 

 or freshwater conditions, and was completed by the epoch of uplift 

 and erosion in the Oligocene. The second was initiated by submer- 

 gence in the Miocene, was continued by the gradual elevation in the 

 Pliocene, when, as in the later Eocene, freshv/ater conditions sup- 

 planted marine, and has been practically completed by the Quaternary 

 uplift which marks the present position of the continent. 



PERIODS OF MAXIMUM ELEVATION AND SXIBSroENCE 



The periods of marked elevation were the Oligocene, late Plio- 

 cene, and Quaternary; the periods of maximum subsidence were the 

 middle Eocene and upper Miocene; the periods of greatest volcanic 

 activity were the middle Eocene and the middle Miocene. It is note- 

 worthy that the periods of maximum volcanic activity were practically 

 coincident with the periods of maximum subsidence in adjacent 

 areas. 



CHANGES IN CLIMATE 



The climate was tropical to subtropical in the Eocene, transitional 

 from this to warm temperate in the Oligocene, warm temperate in the 

 Miocene, transitional from this to sub-boreal in the lower Pliocene, 

 sub-boreal in the upper Pliocene and lower Pleistocene, and warm 

 temperate in the later Pleistocene. 



DIASTROPHIC PROVINCES 



The study of the Tertiary history of the Pacific Coast shows the 

 following positive elements or areas of persistent uplift in the coastal 

 belt: The Olympic Mountains; a more or less uncertain, probably 

 disconnected, belt along the western part of Washington and Oregon; 

 the region of the California-Oregon line and thence eastward toward 

 the Blue Mountains of southeastern Washington; the Santa Lucia 

 Range, south of Monterey Bay; the region north and northeast of 



