Vol. 5] Knopf. — Land Connection between Asia and America. 419 



shows that the region in the vicinity of Cape Nome was de- 

 pressed at least 112 feet helow sea-level during the Pliocene and 

 has only partly recovered from that submergence during Quat- 

 ernary time. 



CONCLUSIONS. 



The stratigraphy of adjacent portions of Asia and America, 

 so far as now known, throws little light on the question of 

 whether a land connection between those continents ever existed 

 during Cenozoic time. In fact, all the evidence from which 

 conclusions of some positiveness can be drawn record only epochs 

 of more widely spread submergence and increased separation of 

 the continents. It has been determined beyond question that 

 the uplift of submerged portions of the continental border was 

 accompanied by marked deformation. During the upraising of 

 the marine-wrought York bench a differential warping of 400 

 feet in a distance of fifteen miles was produced. 



Dawson, 18 writing in 1894, believed that the available evidence 

 pointed to a general submergence during the later Miocene, 

 uplift of the present land areas at the close of the Miocene, and 

 subaerial conditions, with possibly brief intervals of depression, 

 during post-Miocene time. The evidence of the Miocene sub- 

 mergence, however, was based on the occurrence of the Nulato 

 sandstone on the lower Yukon, which had been referred to the 

 marine Miocene by Dall, but which subsequent work has shown 

 to be of Upper Cretaceous age. 19 



The observations of the last decade show that it is unsafe 

 to make wide-reaching generalizations embracing the whole region 

 of Bering Sea and its environs. The diastrophic movements 

 have been too complex, the oscillations of the strand line too 

 frequent and localized, and the information concerning them 

 too scanty. Recognizing those elements of uncertainty, we may 

 sketch the Cenozoic history of the region as interpreted from 

 the evidence now available. 



is Dawson, G. M., Geological notes on some of the coasts and islands 

 of Bering Sea and vicinity. Bull. Geol. Soc. Amer., Vol. 5, 1894, pp. 143 

 et seq. 



is Brooks, A. H:, Geography and Geology of Alaska: Prof. Paper U. 

 S. Geol. Survey No. 45, 1006, p. 236. 



