76 



University of California Publications in Geology [Vol. ll 



Above this, the strata consist chiefly of fine, gray sandstone, becoming 

 finer and more shaly near the top. 



Fossil wood and fairly good leaf impressions were found in 

 abundance at several localities in the basal beds ; none of these forms 

 have as yet been determined. 02 



Summary of section of San Lorenzo and basal Monterey as meas- 

 ured from the south side of Sobrante anticline, a little to the west of 

 Bear Creek. 



Basal part of 

 Monterey Group 

 (Area montereyana 

 zone) 



San Lorenzo 

 series (Agasoma 

 gravidum zone) 



Tejon 



250 feet — Claremont shale. Soft and diatomaceous in some 

 localities, in others, hard and flinty ; layers of chert with 

 partings of shale. 



80 feet — Sobrante sandstone. Medium coarse, massive, 

 light gray sandstone, grades into Claremont shale. 



Unconformity 



250 feet — Concord formation. Fine, grayish sandstone 

 which apparently becomes rather shaly near the top ; 

 thin layer of tuffaceous conglomerate at base, as de- 

 scribed above. (Fossils found at base of these beds 

 listed under University of California locality 3053.) 



Disconformity 



100 feet — Kirlcer tuffs. White, fine, fairly indurated tuffs; 

 contain Schizaster calif omica and Glycimeris tenuimbri- 

 cata in abundance. 



40 feet — San Ramon formation. Massive, medium coarse 

 to fine, fossiliferous, gray sandstone. University of Cali- 

 fornia locality 14 is the basal bed of this section. 



Uncomf ormity 



Shale. 



Evidence for a Stratigraphic Break Between the San Lorenzo and the 



Monterey 



Fairlj' conclusive evidence for a stratigraphic break of consider- 

 able importance between the San Lorenzo and the Monterey of the 

 Sobrante anticline is brought out in the mapping of these beds. 

 Apparently there is no appreciable difference in dip between the beds 

 of the two horizons, but a considerable difference in strike was found 

 at several localities. The beds representing the San Lorenzo series a 

 little to the west of Bear Creek are much thinner on the north side of 

 the anticline than on the south side, the latter locality being not more 

 than a half-mile from the former. Only a few feet of the Concord 

 formation is present on the north side of the anticline, the entire thick- 



62 Two of the most important fossil localities in the Concord formation are 

 University of California localities 3055 and 3053. 



