Geol.— Vol. II.] ANDERSON— STRATIGRAPHIC STUDY 157 



Introduction. 



In order that one of the main purposes of this paper may 

 be understood, it is necessary, at the outset, to make the 

 following statement. It is believed that during the Neocene 

 periods, if not throughout the Tertiary, there were a number 

 of more or less separated basins, or minor faunal provinces, 

 along the Pacific border, two of which are represented 

 within the confines of California. 



The California interior basin was bounded approximately 

 by the outer Coast Range, the Tehachapi Range, and the 

 Sierra Nevada. At the south the barrier described a broad 

 curve, following the axis of the Santa Cruz and Santa Lucia 

 ranges along the present coast, thence turning eastward to 

 Pine Mountain and the Tehachapi Range, which united it to 

 the Sierra Nevada. The interior basin thus occupied the 

 region of the Great Valley of California and the inter- 

 montane valleys between that and the coast. 



The basin thus bounded and outlined is clearly distin- 

 guished from that of the open ocean of the time, the littoral 

 deposits of which form a narrow fringe at intervals along the 

 present coast, or fill the narrow coastal valleys, especially 

 at the south. 



The present paper is concerned especially with the deposits 

 of the interior basin of California, which are believed to be 

 typically represented in the Mount Diablo Range and in a 

 few other localities within the Great Valley. 



The Mount Diablo Range, as defined by Whitney,' 

 extends along the southwestern border of the Great Valley 

 of California, from Mount Diablo, near the Straits of Car- 

 quinez, southeasterly to Pine Mountain, where it unites with 

 the Tehachapi Range, which links it with the Sierras. Thus 

 the valley of the San Joaquin is surrounded by a continuous 

 barrier of ranges on the east, south, and west, while it is 

 separated by the Mount Diablo Range from the rest of the 

 interior basin occupied by the Salinas and the Carisa valleys. 

 In other words the Mount Diablo Range divides the basin of 



1 Geo!. Surv. Calif. Geol. v. i, pp. 8-60. 



