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University of California Publications. [Geology 



sandstones are predominant. Several bands of shale are present 

 and also several prominent belts of conglomerate bnt none of 

 these exceed two feet in thickness. Fossils are abundant. On 

 the east side of the valley along the line of this same section the 

 strata are well exposed. For the most part they are composed 

 of heavy, thick-bedded, gray sandstones which are very conglom- 

 eratic in places, and beds of conglomerate and shale. Near the 

 top one belt of shale has a thickness of over fifty feet. The top- 

 most strata are composed of a yellowish-gray, thick-bedded sand- 

 stone. Beyond this only the Orindan is exposed, with no tuff 

 intervening. 



Corral Hollow. — In the vicinity of Corral Hollow the San 

 Pablo has a thickness of about twelve hundred feet and outcrops 

 for a distance of nearly ten miles. The strata dip to the north 

 at low angles. The strike is nearly east and west. The Monterey 

 appears to be absent and the San Pablo lies upon the Tejon. 

 Above, it is overlain by the Orindan. The line of contact cannot 

 be determined with certainty as one seems to grade into the other. 

 The strata are composed mostly of heavy, thick-bedded bluish- 

 gray sandstones, shales, and conglomerates. The shale bands 

 predominate at the base. In these occur fossil leaves. 



North of Karquinez Straits. — On the north side of Karquinez 

 Straits the San Pablo is represented in Carneros Creek Canon 

 between the towns of Napa and Sonoma. Farther north it occurs 

 in the hills on either side of Pleasant 's Valley extending from 

 Vaeaville to Winters. 



In the hills between Napa and Sonoma the San Pablo is repre- 

 sented by a volume of sandstone, shale and conglomerate having 

 a total thickness of over fifteen hundred feet. It rests appar- 

 ently unconformably upon the Tejon sandstone and dips north- 

 westerly at an angle of 60 degrees into the hills. It lies uncon- 

 formably beneath the Pliocene volcanics. No Monterey occurs 

 in this region. The base is composed of thin-bedded shaly sand- 

 stones, shale and sandstones. Higher up the formation is com- 

 posed of thick-bedded, soft, bluish-gray sandstones, resembling 

 in places almost a volcanic ash. One or two narrow seams of 

 shale are present. 



In the Pleasant 's Valley section the San Pablo lies directly 



