1914] Dickerson: Fauna of the Martinez Eocene of California 93 



of the fold. This syncline plunges toward the west. Both the Tejon 

 and Martinez are found in this fold. The Martinez rests upon the 

 Chico, Knoxville, and Franciscan and on the west it is overlapped by 

 the later "Cache Lake" beds, andesitic lava flows, and alluvium. 



The Franciscan in this region consists of a typical complex of 

 diabase, radiolarian cherts, seamed quartzitic sandstone, fine-grained, 

 dark gray schists, and bedded foraminiferal limestones. Serpentine is 

 intruded as small dikes in the sedimentaries. This series appears to 

 be in fault contact with the Chico on the south side of the syncline 

 described above and the Martinez appears to rest upon it uncon- 

 formably. 



A small area of Knoxville appears in contact with Martinez on the 

 extreme eastern limit of the Martinez area. It consists of a dark gray 

 limestone and shale containing well-preserved specimens of Aucella 

 piochii Gabb. The main Chico area borders the Martinez on the south. 

 It consists of a laminated, dark gray sandstone weathered to yellow 

 brown, dark gray shale with limestone strata or limy concretions and 

 minor strata of micaceous, carbonaceous, brown sandstone interbedded 

 with it. The only fossils found in it were Chione varians (Gabb) and 

 a Pecten, n. sp., obtained at University of California Location 783, 

 three-quarters of a mile west of Lower Lake. Structurally the Chico 

 is folded in many minor plications and shows complex twisting and 

 faulting. The lower Martinez can be readily distinguished from the 

 underlying Chico by great differences in lithology and structure. 

 The lower Martinez consists of medium-grained, hard sandstone con- 

 taining grains of hornblende, quartz and biotite. It has a peculiar 

 velvety luster which may be due to secondary silica. Structurally the 

 Martinez is not faulted, nor has it been folded and contorted like 

 the underlying Chico. In the bed of Herndon Creek near the contact 

 with the Chico it has a strike of N 50 W, while that of the Chico is 

 N 65 W. The basal Martinez appears to overlie the Chico, Knoxville 

 and Franciscan indifferently and without doubt it is unconformable 

 upon all of them. Differences in strike, in the amount of folding and 

 crushing, in fauna and in areal distribution between the Martinez and 

 the underlying Chico, Knoxville and Franciscan lead us to the above 

 conclusion. The great thickness of the Martinez in this region is 

 noteworthy. A measured section down Herndon Creek shows that 

 the basal Martinez consists of 1200 feet of medium gray sandstone. 

 This is overlain by 500 feet of fine, massive, tan-colored sandstone 

 flecked with black grains. No exposures of Martinez are found for 



