THE MARINE TERTIARY OF THE WEST COAST 613 
This great incursion is referred to here as the Merced sea and 
represents the time of deposition of the Purissima, Etchegoin, and 
Jacalitos (Fig. 11). The condition was similar to that which 
existed in the Upper Miocene, when there were restricted basins at 
the opening of the period, a great incursion during the later part of 
the period, and then a retreat shown by widespread unconformities. 
Fic. 12.—Saugus (Upper Pliocene) 
The Saugus formation, of which little is known, appears to have 
been formed after the folding and consequent retreat of the sea 
from the great inland basins in the San Joaquin and Salinas Valley 
districts. ‘The Saugus beds are largely confined to the coast, but 
in the Ventura district an embayment extended a considerable 
distance inland (Fig. 12). 
The Pliocene period was followed by great crustal movements 
which folded the formations in great anticlines and synclines, some 
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