248 RALPH ARNOLD 



Miocene and Pliocene, conditions prevailed favoring the migration 

 of similar faunas into Japan and California or intermigration between 

 the two. This is shown by the close similarity of certain pectens 

 found in the upper Miocene in California, in still later beds in Alaska, 

 and in the living fauna of Japan. The general resemblance of the 

 late Tertiary faunas of California and Japan also favors this conclu- 

 sion. 



SUMMARY AND CONCLUSIONS 



SUMMARY 



Following the period of elevation and erosion at the close of the 

 Cretaceous, the Eocene was inaugurated by a subsidence below sea- 

 level of the greater part of western Washington and Oregon and the 

 western part of central and southern California. Volcanic activity 

 was pronounced in the early and middle Eocene. Later in the 

 Eocene brackish- and freshwater conditions prevailed over the same 

 area, and extended over much of Alaska. The fauna and flora of 

 the Eocene were tropical to subtropical. The Oligocene was a period 

 of elevation with marine conditions restricted to a much smaller 

 area than in the Eocene. The fauna was transitional with stronger 

 affinities toward the Miocene. The lower Miocene marked a wide- 

 spread subsidence in the coastal belt which was followed by a period 

 of mountain building and great local deformation, volcanism, etc. 

 The Miocene faunas and floras indicate conditions comparable with 

 those of the present day, or possibly a little warmer, except at the 

 very close, when cool conditions began to prevail. The upper 

 Miocene was a period of subsidence, with ideal conditions for maxi- 

 mum deposition of sediments in local basins. During Pliocene and 

 early Pleistocene time there was a continuation of many of the upper 

 Miocene conditions, except that marine environment gave place 

 locally to freshwater. The marine fauna of the upper Pliocene and 

 lower Pleistocene indicates sub-boreal conditions in southern Cali- 

 fornia, followed by conditions in the middle or later Pleistocene more 

 tropical than those of today. A period of elevation and considerable 

 local deformation in the early Pleistocene inaugurated the present 

 conditions on the Pacific Coast. Many of the movements occurring 

 throughout the Tertiary were of local extent, and, for that reason, 



