Vol. 5] Knopf. — Land Connection between Asia and America. 415 



GEOLOGY. 



The oldest rocks of Seward Peninsula comprise various 

 schists, limestones, and gneisses, forming' the bedrock of the 

 auriferous areas. They are regarded as probably of early Paleo- 

 zoic age. In the northwestern part of the peninsula there is a 

 large area of fossiliferous limestone, called the Port Clarence 

 limestone, which on the basis of recent paleontologic study is 

 known to range in age from Upper Cambrian to Upper Silurian. 4 



Near Cape Prince of Wales a belt of limestone and marble 

 five miles wide trends northwest across the western extremity 

 of the peninsula. Evidence secured by Collier 5 shows it to be 

 of Mississippian age. 



A stock of coarse porphyritic granite is intrusive into the 

 limestone and is therefore of post-Mississippian age. It is in 

 all probability pre-Cretaceous, like analogous occurrences in the 

 eastern part of Seward Peninsula." This granitic mass forms 

 the youngest bedrock of that portion of the American continent 

 lying in closest proximity to Asia. The Diomede Islands mid- 

 way between the continents are composed of similar granite. 



There are, however, scattered throughout the peninsula, small 

 patches of unaltered sediments composed of conglomerates, sand- 

 stones, and shales, locally carrying seams of coal, of which the 

 largest known is 88 feet thick. These rocks rest unconformably 

 on the metamorphic terranes, and in the absence of fossil evi- 

 dence are believed from their lithologie resemblance to other 

 coal-bearing formations of Alaska to be of Cretaceous or Eocene 

 (Kenai) age. On St. Lawrence Island, which lies about 150 

 miles south of Bering Strait and is the largest island in Bering 

 Sea, Collier has discovered some coal-bearing sediments carrying 

 plant remains. 7 A few conifers and dicotyledons were found, 

 among which Knowlton has identified Sequoia langsdorfii, indi- 

 cating Kenai age. This bit of evidence, incomplete and unsatis- 

 factory as it is, is the most important yet discovered that bears 



* Kindle, E. M., unpublished manuscript. 



o Collier, A. J., Bull. U. S. Geol. Survey No. 328, 1908, p. HI. 

 « Oral communication by P. S. Smith. 

 7 Unpublished information. 



