THE EOCENE OE NORTH AMERICA 465 



unconformably upon Mesozoic and Paleozoic strata. No fossils 

 have been reported from it. It consists of a coarse, variable 

 conglomerate. Its thickness varies from a few feet to 1000 feet. 

 It is thicker toward the west and dips toward the eajst. 



Some geologists, however, would dispute the right of the San 

 Miguel formation to a place among the Eocene formations on 

 the grounds on which Purington places it there. If it is admit- 

 ted to the Eocene epoch, there would seem to be no good reason 

 for excluding a number of other formations, among which are 

 the Denver and the Arapahoe beds. Geologists appear to be 

 not fully agreed upon the criteria that shall determine the base 

 of the Eocene. 



INTERPRETATION 



Having reviewed the various Eocene formations of the 

 region, we may now consider some of the conditions presented 

 by the region as a whole, and some of the problems involved in 

 its history. 



Physiography and Climate. — On the Pacific coast the Tejon as 

 now known was deposited in marine water which occupied the 

 great valley of California and western Oregon. It is not known 

 whether the beds of Oregon and California were connected with 

 each other or not. This interior sea in which the Tejon of 

 California was deposited probably connected with the ocean in 

 southern California. There may have been several connecting 

 channels. No definite knowledge exists upon the subject. 

 Before the end of the Tejon deposition the Chico area in Oregon, 

 which had been land and subject to erosion, went down beneath 

 the sea, and beds of Upper Tejon age, possibly underlain by 

 Martinez, were deposited upon it. Probably the same subsidence 

 admitted the sea in which the Umpqua and Tyee beds were 

 deposited a little farther to the southwest. If so, these beds 

 are to be correlated with the Tejon. The correlation of these 

 geographically separated beds must finally be decided by their 

 fossils. 



The plants of the Kenai formation indicate a temperate 

 climate at the time of their growth. This climate probably 



