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University of California Publications. [Geology 



most abundant and easily recognized form. The fauna is known 

 so far by about fifty species, of which nearly one-third are pe- 

 culiar to these beds, about one-fourth are known also from the 

 Contra Costa County Miocene, and one-sixth from the Merced." 

 Further he says: "The sea-urchins form the most prominent 

 organic feature of the formation, neither of the Astrodapsis 

 species being found outside of it." Lithologically he charac- 

 terizes it "as containing a considerable thickness of tuffs and 

 ashes, most prominent in the upper portion of the formation, and 

 a peculiar weathering of the sandstone." He considers the pos- 

 sibility of a break between the San Pablo and the Contra Costa 

 County Miocene and states that the stratigraphic relations of 

 the San Pablo to the Merced are not definitely known. He finds 

 the fauna of the San Pablo more closely related to the Contra 

 Costa County Miocene than to the Merced fauna. As to the age 

 he considers that it probably represents the middle Neocene. 



In September, 1908, Dr. H. W. Fairbanks correlated Neocene 

 beds in the San Luis range with the San Pablo of middle Cali- 

 fornia. 



In 1898, Mr. II. W. Turner 7 in his paper on the Rocks of the 

 Coast Ranges of California gives quite a detailed description of 

 the San Pablo localities in the vicinity of Mount Diablo and 

 Corral Hollow. Large collections of fossils were made and on 

 the basis of the ratio of the living and fossil forms he regards 

 the formation as of lower Pliocene age. At Kirker's Pass he 

 divides the formation into four divisions, the lowermost being 

 composed of fine-grained white shales and volcanic detritus. The 

 second division is composed of sandstone containing a majority 

 of the marine fossil shells. Above this are blue beds composed 

 of volcanic conglomerates, tuff, and sandstone. In the topmost 

 portion of this were found leaves and above all were layers of 

 volcanic pumice. The total thickness of the formation at Kir- 

 ker's Pass he considers to be six hundred meters. At Railroad 

 Ranch and Corral Hollow similar fossil leaves were found. He 

 suggests a possible correlation with a part of the auriferous 

 gravels in the Sierra Nevada. 



i Journal of Geol., vol. 6, pp. 483-499. 



