416 



University of California Publications. [Geology 



on the question of a land connection between the continents 

 during the early part of the Tertiary. 



Rocks of Kenai age are known in widely separated parts of 

 Alaska, and are of fluvial, lacustral, and possibly, in part, of 

 estuarine origin. The Kenai flora indicates that temperate or 

 subtropical conditions prevailed over Alaska in Upper Eocene 

 time. 



Extensive deposits of alluvial material occur throughout 

 Seward Peninsula. They consist of sands, gravels and silts, and 

 local accumulations of glacial debris. They have not yet been 

 studied from a chronological standpoint. Logs of a species of 

 spruce, the northern limit of which is now in the latitude of Sitka, 

 and mammalian remains have been found in them, and indicate 

 climatic conditions greatly different from those of the present. 8 



Scattered observations only are available concerning the 

 adjacent Siberian coast. These concur in describing it as a 

 bold mountainous region composed essentially of granitic rocks. 



According to Suess, 9 Bogdanowitsch has investigated the 

 geology of Chukchi Peninsula in some detail. He finds that 

 the rocks are mainly of eruptive and metamorphic character, 

 from which it may be concluded that they furnish little light on 

 the problem under discussion. 



Prom the foregoing brief resume it is obvious that the record 

 of the geologic history of the region as revealed by the sedi- 

 mentary rocks is characterized by immense lacunae, and is prac- 

 tically a blank for the whole of the Tertiary period. Such 

 further evidence as may be obtained must be afforded by the 

 study of the physiographic evolution of the region. 



Accumulating evidence shows that the physiographic history 

 is complex in detail. It is unfortunately true that the peninsula 

 has not been studied as a whole by any one observer, and conse- 

 quently a comprehensive account has not yet been formulated. 

 Certain broader facts, however, have been established, and from 

 them may be drawn conclusions important to the present dis- 

 cussion. 



s The available information concerning the Pleistocene vertebrate 

 fauna of Alaska has recently been assembled and discussed by C. W. 

 Gilmore in Smithsonian Misc. Coll., vol. 51, 1908. 



9 Antlitz der Erde, vol. Ill, 2d part, 1909, p. 405. 



