Cenozoic Floras Around the Northern Pacific 67 



altitudes in western North America in the Miocene epoch. Since 

 it Uved in situations suited to the preservation o£ leaves and 

 other parts of the plants, this forest has left a plentiful and wide- 

 spread record from CaUfornia north to southern British Colum- 

 bia, and eastward across Idaho and Nevada into Montana and 

 Colorado. By the end of the Miocene, reduction in rainfall and 

 temperature, with associated orogeny, had greatly restricted its 

 distribution and limited its opportunities for entering the fossil 

 record. This forest has survived, with important modifications, 

 in many limited areas in western North America. The presence 

 of its altered modern equivalent in the eastern United States 

 at the present time suggests that in the Miocene it may have 

 occupied this area as well, but the fossil record of its occurrence 

 there is too scant to establish definitely such a distribution. 



The dominant species of the Miocene floras of western Amer- 

 ica is Sequoia langsdorfii, the Tertiary equivalent of the living 

 S. sempervirens, the coast redwood. Present in the older Tertiary 

 floras of Alaska and northeastern Asia, this species is completely 

 absent from the Eocene deposits of California and Oregon.* It 

 is much reduced in distribution in the Pliocene epoch, and may 

 therefore be used as an accurate index fossil for the Miocene of 

 middle latitudes. The climatic and other physical requirements 

 of the modern coast redwood are so restricted as to make its 

 Tertiary equivalent a valuable indicator of past environments. 

 Particularly is this true where remains of Sequoia langsdorfii are 

 found with those of Alnus, Quercus (Lithocarpus), Umbellu- 

 laria, and other genera which are its most regular associates 

 along the northern coast of California at the present time. Ex- 



• S. langsdorfii is recorded from the upper Eocene of northwestern Washing- 

 ton, in a flora intermediate between the typical subtropical type from the Eocene 

 of more southern latitudes and the typical temperate type from the Eocene of 

 Alaska. 



