176 



University of California Publications. 



[Geology 



conglomerate. Either the Chico or Martinez formations sup- 

 plied this material, or possibly both may have contributed to this 

 basal Tejon, as these species are limited to the upper Cretaceous 

 and the Eocene on this coast. 



RELATION OF MARTINEZ TO CHICO. 



The evidence of relationship of the Martinez to the Chico is 

 based (1) upon the areal mapping of the beds containing char- 

 acteristic faunas of these two formations; (2) upon the variation 

 of dip and strike at the contact; (3) upon a pre-Martinez fault 

 in the Chico ; (A) upon a sudden and complete change from 

 Chico to Martinez fauna at he contact; (5) upon the presence 

 of a line of boring molluscs (Zirphaea) ( ?) which have pene- 

 trated the Chico along the line of contact. 



The strike of the Chico and Martinez throughout most of 

 this field is approximately the same. One marked variation 

 occurs in lower Oil Canon, where the strike of the Chico is 

 N 75° W, while that of the Martinez which rests upon it is 

 N 90° W. A few hundred feet west the Chico has a strike 

 N 90° W. Detailed work shows that the Chico is faulted here 

 and that the contact between the Chico and Martinez is directly 

 traceable across this fault, thus proving the pre-Martinez age of 

 the fault. 



One mile south of Stewartville a sharp contact between the 

 Chico and Martinez was found. The Chico sandstone has a dip 

 of 65° N, while the gray conglomeritic Martinez sandstone has a 

 dip of only 45° N. Immediately below the contact this Chico 

 sandstone contains the folowing fauna: Meckia sella, Tellina 

 matheivsoni, Inoceramus, sp., Cypraea, sp., Scalaria, sp., and a 

 shark's tooth. Ten feet below the contact the Chico forms 

 Hclicoceras vermicular is, ('in alia obliqua, and Tellina, sp. were 

 found in a dark gray limestone. 



From six inches to ten feet above the contact at the above- 

 mentioned locality the following Martinez species were collected : 

 Tellina uudulifcra, Ampullina striata, Turritella infragranulata, 

 Area biloba, Urosyca caudata, Cucullaea matheivsoni, Pectun- 

 c ul us veatchii, var. major, Siphonalia lineata, Lima, n. sp. ( ?), 



