452 



REPORT OF NATIONAL MUSEUM, U>04. 



basis of his geological map of the United States, published in Boston 

 in 1853, above noted, he claimed to have been the first to recognize in 

 the West. He divided it into three divisions, the lowest of which he 

 considered as equivalent to the red sandstones of Lake Superior (now 

 considered as Cambrian), the Bay of Fundy, the Prince Edward and 

 Magdalen islands, and a part of that of Virginia and New Jersey. At 

 Pyramid Mount, in the Llano Estacado, he claimed to have found 

 Jurassic rocks overlying conformably the Keuper (the first discovery 

 of rocks of this horizon in America), and at Galisteo, in New Mexico, 

 the White Chalk division of the Cretaceous. From the fact that the 

 Cretaceous beds lie unconformably upon the upheaved Triassic and 

 Jurassic beds, he concluded that the same were deposited after the 

 principal dislocation of the Rocky Mountains, which took place at the 

 end of the Jurassic period. 



The Sierra Nevada he rightly inferred to be of more recent uplift 

 than the Rocky Mountains, probably dating from the end of the 



Miocene or Pliocene, and the Coast Range 

 from the end of the Eocene. 



To W. P. Blake fell the lot of accompany- 

 ing Lieutenant Williamson, whose route led 

 from San Francisco southward along the San 

 Joaquin River, through San Francisco Pass 

 in the mountains to the Mohave River, and 

 workofw.P.eiake eastward along the thirty- 

 ESESSHSSE* second and thirty-third par- 



Surveys, 1853-1856. a H c l s to tllC UlOUth of the 



Gila. The region, as pointed out by S. F. 

 Emmons," "is not one from which definite 

 geological data could be obtained," the rocks, 

 with the exception of recent and Tertiary 

 formations, being barren and classed as 

 metamorphic and eruptive. He however noted the wide-spread occur- 

 rence of Tertiary rocks about San Francisco and in southern Cali- 

 fornia and the occurrence of eruptive serpentinous rocks. He also 

 made man}' interesting minor observations on the polishing and groov- 

 ing of -hard rocks by wind-blown sand and other desert phenomena. 

 Mountains of the isolated or "lost mountain' 1 type were described, 

 and the fact that the Colorado Desert was below the level of the sea 

 noted. The age of the coast mountains was determined as at least 

 post-Pliocene, and the impregnation of the rocks of the region with 

 gold he regarded as having been contemporaneous with the uplift. 



Fig. 60.— William Phippa Blake. 



"Presidential address, Geological Society of Washington, 1896. 



