384 University of California Publications in Geology [Vol. 9 



a conglomerate which marks a very decided change in sedimenta- 

 tion at the base of the Tejon. (See Fig. 3.) 



Oil Canon 



Sea Leve/' 



Fig. 3. North-south section showing relations of Chico, Martinez and 

 Tejon in the region north of Mount Diablo, near Stewartville. 



FAUNA 



The principal fossiliferous horizon in the Tejon north of Mount 

 Diablo occurs above the coal strata in the vicinity of the old coal 

 mining village, Somersville. Stanton 30 described this locality as 

 follows : 



The contact between the Chico and the Tejon was not found exposed at 

 any place near the coal mines east of Clayton, but it is evident that the coal 

 beds are not far above the base of the Tejon. Gabb reports the occurrence 

 of Cucullaea mathewsonii and Fasciolaria laeviuscula in the "intermediate 

 beds" beneath the coal near Clayton, thus indicating a horizon much better 

 represented by fossils near Pacheco, Benicia, and Lower Lake. At Summers- 

 ville, one of the coal-mining villages east of Clayton, an undescribed species 

 of Corbicula occurs abundantly in a layer beneath the lower coal bed. 



The beds associated with and immediately overlying the coal consist 

 mostly of light-colored, rather coarse, friable sandstone, 400 or 500 feet in 

 thickness. In most of the exposures examined they are fossiliferous only in 

 the upper part, where they contain a typical Tejon fauna like that described 

 from Fort Tejon. Probably the lowest of these fossiliferous horizons above 

 the coal is exposed in a low hill just west of Summersville and south of the 

 cemetery, in sandstones not mere than 100 feet above the principal coal 

 bed mined there, and perhaps 300 feet above the base of the sandstones. 

 The following species have been identified in the collection from this place: 



Modiola ornata Gabb 

 Venericardia planicosta Lam. 

 Lucina gyrata (Gabb) 

 Corbula parilis Gabb 

 Tellina hoffmaniana Gabb 

 Turritella uvasana Conrad 

 Solarium cognatum (Gabb) 

 Ficopsis remondi Gabb 

 Aturia mathewsoni Gabb? 



Pectunculus sagittatus Gabb 

 Cardium cooperi Gabb 

 Solen parallelus Gabb 

 Meretrix uvasana Conrad? 

 Corbula hornii Gabb 

 Amauropsis alveata (Conrad) 

 Rimella macilenta White 

 Fusus californicus Conrad 



The Tejon strata, dipping strongly northward, may be traced almost 

 continuously from Summersville west toward Clayton for three or four 



so Stanton, T. M., The Faunal Relatons of the Eocene and Upper Creta- 

 ceous on the Pacific Coast, 17th Annual Report, U. S. Geol. Surv., pp. 1011- 

 1059, 1896. 



