602 BRUCE L. CLARK 
from the San Francisco Bay area, we find evidences of crustal 
movements between the Temblor and the Santa Margarita which 
have been described as mountain-making. In the Salinas Valley 
region it is not uncommon to find the difference in dip between the 
Temblor and the Santa Margarita as much as 30° to go°, together 
Fic. 7.—Temblor (upper Monterey, Miocene) 
with marked difference in strike. Dr. Arnold, in describing the 
movements that caused this unconformity, says: 
One of the most widespread and important periods of diastrophism in 
the Tertiary history of the Pacific Coast was that immediately following the 
deposition of the Monterey or lower middle Miocene. Its effects are visible 
from Puget Sound to southern California It is marked as much by readjust- 
ment, by local faulting and folding as by general movements of elevation and 
subsidence. In some regions the folding and faulting were intense, the greatest 
disturbances accompanying the uplift of the mountain ranges to an altitude of 
thousands of feet. In other regions low broad folds were formed during the 
