Clark: The San Lorenzo Series of Middle California 89 



Summary or San Lorenzo Section on North Side op Mount Diablo 



San Pablo Group 

 (Upper Miocene) 



Kirker formation 



Markley formation 



Tejon Group 

 (Upper Eocene) 



Basal conglomerates of San Pablo. 



Unconformity 

 50-0 feet — Tuffaceous sandstone. 



350 feet — Ehyolitic, white tuff beds with lentals of bluish 



tuffaceous sandstones. 

 50 feet — Sandstone, tuffaceous toward the top. 



Disconformity 



500 feet — Micaceous, gray to yellow-brown sandstones and 



shales, the latter variegated in color. 

 160 feet — Light-colored shales, diatomaceous in part. 

 300 feet — Dark, carbonaceous, arenaceous and argillaceous 



shales. 



1400 feet — Micaceous sandstones and argillaceous and arena- 

 ceous shales alternating; poor outcrops of shale. 

 200 feet — Soft, argillaceous shale. 



700 feet — Medium-coarse, gray, arkosic, micaceous sand- 

 stones. 



Total, 3700 feet. 



500 feet — Tejon shale. 



List of Species from San Lorenzo Beds to North of Mount Diablo 



Following is a complete faunal list of the known species from the 

 San Lorenzo beds on the north side of Mount Diablo, with the localities 

 indicated in the columns on the side. Abbreviations used are : R, 

 rare ; C, common. Those species marked with an asterisk in front of 

 them are also found in the San Lorenzo beds to the west of the moun- 

 tain in the Concord Quadrangle. 



