TERTIARY FAUNAS OF THE PACIFIC COAST 53a 
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, 
