Geol.— Vol. II.] ANDERSON— CRETACEOUS DEPOSITS. 7 



The Chico Group was made to embrace all of the occur- 

 rences of Cretaceous on the eastern side of the Sacramento 

 Valley, some important beds in the vicinity of Mount Diablo 

 and Martinez, in Southern Oregon, and the coal-bearing 

 deposits of Vancouver Island. It was correlated with the 

 Chalk of England, though not definitely with either division. 



The Martinez was believed to be distinct from the Chico, 

 and was represented by beds at Mount Diablo, and near 

 Martinez, Contra Costa County. 



In 1887, in connection with the work of the United 

 States Geological Survey upon the quicksilver deposits 

 of the Pacific Coast, Becker (1888) and White (1888 and 

 1889) revised the classification of the California Cretaceous, 

 recognizing essentially two divisions, the Lower and the 

 Upper, separated by an unconformity. 



The Upper Cretaceous was called the Chico-Tejon, to 

 which were annexed, as probably conformable with it, the 

 Wallala Beds discovered by Becker on the coast of Sonoma 

 and Mendocino counties, at San Diego, and in Lower 

 California. 



The Lower, or Shasta Group, was made to include not 

 only what is now recognized as properly belonging to that 

 division, but they placed in it also a great series of meta- 

 morphic rocks occurring in the Coast Ranges, as well as 

 the Mariposa formation of the western Sierra Nevada, both 

 of which are now known to be distinct from it. The lower 

 portion of the Shasta Group was called the Knoxville, from 

 its occurrence, with its typical fauna, at Knoxville in Napa 

 County. The upper portion of the Shasta, or the Horse- 

 town stage, was thought to be perhaps a portion of the 

 same series, and involved with the Knoxville in the "pre- 

 Wallala upheaval." 



It was afterwards shown by A. Hyatt (1894), J. S. Dil- 

 ler (1894) ^"d J- P- Smith (1894) that the former view 

 held by Professor Whitney regarding an unconformity 

 between the Mariposa and Cretaceous strata was correct; 

 that after the folding and metamorphism of the Mariposa 

 slates the Cretaceous subsidence of the region had been 



