612 BRUCE L. CLARK 
the Pliocene, that the basins of deposition were local. Crustal 
movements appear to have been more frequent during the Pliocene 
than during the other periods of the Tertiary, and we may therefore 
expect to find a large number of stratigraphic breaks which do not 
represent any very great time break. At the opening of the 
Pliocene the Jacalitos sea was much more limited than the seas of 
ee ee. ee 
SS 
Fic. 11.—Merced (Middle Pliocene) 
the Middle or possibly the Upper Pliocene, and the principal 
localities where deposition took place were probably in the region 
of the southern and western side of the San Joaquin Valley and the 
southern part of the Salinas Valley. This sea was probably con- 
nected with the ocean in the vicinity of the upper Salinas Valley. 
With the opening of the middle Pliocene a great change had 
taken place. The sea transgressed over wide areas to the north. 
Areas which had previously been subject to erosion were covered. 
