70 
SANTA MARIA OIL DISTRICT, CALIFORNIA. 
had been more highly tilted the later sediments were laid down 
unconformably. In places the first Fernando beds were of similar 
lithologic character to the Monterey shale, being deposited probably 
under similar conditions or else derived from the redeposition of the 
shale material. This similarity, added to the bedding conformity, 
caused the formations to appear as completely conformable and con¬ 
tinuous. But the presence in places of layers of brecciated Monterey 
shale at the base of the Fernando, and in places of true angular 
unconformities, proves that a period of erosion preceded the Fer¬ 
nando deposition. 
After the period of deposition of the finer sediments usually found 
at the base of the Fernando, shallow-water conditions prevailed. 
The deposits were almost entirely detrital, the product of erosion on 
land, much of the material coming from areas of Monterey shale. 
Fresh-water or possibly brackish-water conditions may have pre¬ 
vailed in the latter part of Fernando time. They certainly did for a 
time and locally, at least, when the brackish-water limestone beds 
were formed. 
MAIN QUATERNARY PERIOD. 
Downward and upward movements of the coastal region were 
probably in progress during the Fernando period, but were intensi¬ 
fied early in Pleistocene time, and disturbance of the strata along the 
lines influenced by the post-Monterey upheaval took place. In this 
way the mountain ranges were upraised in their present position and 
the Fernando became warped along the lines of further folding in the 
Monterey. 
After this uplift erosion set in and eventually removed the Fer¬ 
nando from some parts of the region over which it had formed a 
thick covering. The mountain regions were worn into rugged shapes, 
Santa Maria and Santa Ynez rivers developed graded valleys, and 
the sea planed off the coast extensively by cutting. During the same 
period, however, land building over this region was in progress as the 
result of differential movements of the coast. The great resultant 
changes of level in post-Fernando time, as indicated by the records, 
were a pretty general depression to a depth of 1,100 to 1,200 feet, and 
locally to at least 1,400 feet; and a later uplift to the present 
level. These movements were probably gradual and continuous, 
but not sufficiently slow to allow the formation of deposits of great 
thickness. During these movements the sea cut into the land as the 
water encroached and receded, forming terraces inclined toward the 
ocean, and beach and shallow-water sediments were laid down as thin 
coatings over the newly planed surfaces. These deposits were prob¬ 
ably formed as the land rose. During the periods of depression the 
streams built up deposits of gravel, sand, and clay at different levels, 
giving rise to extensive terraces and to filled valleys. Great deposits 
