1914] Dickerson: Fauna of the Martinez Eocene of Calif ornia 71 



DESCRIPTIONS OF THE TYPICAL MARTINEZ SECTIONS 



IN CALIFORNIA 



Lower and Middle Zones op Martinez North of Mount Diablo 



The stratigraphy and the faunal relations of the Martinez to the 

 Chico and Tejon have already been fully discussed in a former 

 paper. 18 The zonal relations of the Martinez in this area have not 

 been described. In the Martinez area four miles north of Mount 

 Diablo we have a lower section which has yielded the most abundant 

 fauna of any Martinez locality, over eighty species having been found 

 in the lowermost beds alone. Abundantly fossiliferous, distinctly 

 bedded outcrops extending for the entire length of the east-west four- 

 mile strip have enabled the writer to be sure of the stratigraphic 

 position of the various fossil localities. A north-south cross-section 

 examined a mile south of Stewartville is, in descending order, as 

 follows : 



(5) Gray-green shales, 250-300 feet. 

 (4) Gray-green, glaueonitic sandstone, 50 feet. 

 (3) Fine-grained, bard, gray sandstone, 200 feet. 

 (2) Shales and argillaceous sandstones, 100 feet. 

 (1) Brown, conglomeratic, lower sandstone, 50-100 feet. 

 Total, 650-750 feet. 

 (See figure 2.) 



A similar section was examined at the head of Oil Creek, two miles 

 west of this line. The principal fossil localities are limited to the 

 lower bed and the gray-green glaueonitic sandstone four hundred feet 

 above the base. The accompanying map shows these localities (see 

 fig. 3). The lower bed yielded a fauna in which one of the most 

 abundant forms was Meretrix dalli, n. sp. 



FAUNA OF THE MERETRIX DALLI ZONE 



Large collections from the lowermost beds have been made by 

 J. R. Powers, B. L. Clark, William Kew and the writer in the past 

 three years. Below is a complete list of the fauna obtained from 

 these beds : 



is Dickerson, Roy E., Univ. Calif. Publ. Bull. Dept. Geol., vol. 6, pp. 173-177, 

 1911. 



