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University of California Publications. 



[Geology 



San Pablo Time. — The San Pablo rocks indicate in general 

 slow submergence followed by a slow uplift during which deposi- 

 tion went on continuously. 



The basal conglomerates of the San Pablo formation indicate 

 non-marine sedimentation over a basin whose floor consisted of 

 the eroded Monterey and Franciscan rocks. The erosion period 

 of the pre-San Pablo rocks had not ceased and both Franciscan 

 and Monterey rocks were prominent features of the land mass, 

 supplying waste to form the conglomerates of the San Pablo. 



Submergence continued and the blue sandstones, growing 

 finer and finer towards the top, were deposited, overlapping the 

 basal conglomerates. Distant volcanoes contributed their fine 

 ashes. 



At just what time marine conditions were inaugurated is 

 doubtful, but they continued to the end of San Pablo time. 

 Uplift began and the brown fossiliferous sandstones were de- 

 posited, followed by the conglomeratic sandstones at the top of 

 the San Pablo formation. This uplift continued and the San 

 Pablo sediments emerged from the sea. The uplift was not 

 accompanied, apparently, by any profound disturbance. An 

 erosion interval of perhaps not great length ensued and the land 

 was again slowly submerged to receive the Merced sediments. 



Merced and Later. — During Merced time the diorite of the 

 Santa Cruz range became submerged and its surface was exposed 

 to wave action. The sea transgressed over part of the land and 

 evidently formed a deep bay across the region now occupied by 

 the Pajaro Valley-. In this bay marine sedimentation went on. 

 During this period sedimentation was temporarily interrupted 

 and fresh-water conditions prevailed in the Santa Clara Valley 

 and delta beds were deposited. At least twice during the earlier 

 part of this delta accumulation the sea overflowed the fresh- 

 water depositional area and a sparse marine life existed for a 

 time, only to be forced out again by the gradual exclusion of the 

 sea and the resumption of fresh-water conditions over this inland 

 basin. 



The uplift following the close of the delta deposition was 

 accompanied by considerable tilting and folding. The fresh- 

 water and Merced beds were both affected. In the erosion which 



