Vol. 5] Knopf. — Land Connection between Asia and America. 417 



After the deposition of the coal-bearing sediments a long 

 period of stability supervened, during which much of the penin- 

 sula was reduced to a peneplain. According to Brooks, 10 the age 

 of this peneplain has not been determined, but it is probably the 

 same as that of the Yukon plateau, which is known to have been 

 developed in post-Kenai pre-Pliocene time. This old surface of 

 erosion is now represented throughout the peninsula by flat- 

 topped ridges and domes ranging in altitude from 800 to 2,400 

 feet. The level summits of the interstream areas blending into 

 an even sky-line form a striking feature of the topography. In 

 the western part of the peninsula, on the northern flank of 

 Brooks Mountain at an altitude of 1,800 feet, the writer found 

 remnants of well-rounded gravels, which can hardly be inter- 

 preted otherwise than as relics of an ancient drainage system. 

 In the region of the Kotzebue Sound the flat-topped ranges are 

 especially well developed and are rendered highly impressive 

 by terraces, in places up to twelve in number and ranging in 

 height from 10 to 100 feet scored upon their flanks. 11 



A finely preserved terrace of marine origin known as the 

 York bench extends northwestward from Port Clarence to the 

 apex of the continent. South of the York Mountains it bevels 

 the upturned edges of the Port Clarence limestone, and attains 

 a width ranging from a few hundred yards to four miles. "The 

 surface of this bench," says Collier, 12 "is an almost perfect plain 

 swept bare of gravel or other detrital material, but is covered 

 in many places with yellow clay derived from the solution of the 

 limestone." Between the York Mountains and Cape Mountain 

 the bench merges with a prominent topographic feature known 

 as the York Plateau, which constitutes a well-marked upland 

 surface. 13 



At Cape Prince of Wales, the terrace which is there carved 

 upon the granite of Cape Mountain has an elevation of 300 feet ; 

 fifteen miles eastward, at Kanauguk River, it attains a height 

 of 700 feet ; fourteen miles farther eastward at Lost River it 



i<> Bull. U. S. Geol. Survey No. 328, 1908, p. 112. 



11 Moffit, F. H., Bull. U. S. Geol. Survey No. 247, 1905, p. 44. 



12 Prof. Paper U. S. Geol. Survey No. 2, 1902, p. 37. 



is These features are well shown on the topographic maps accompanying 

 Bull. U. S. Geol. Survey No. 328, 1908. 



