UNIVERSITY OF CALIFORNIA PUBLICATIONS 

 Bulletin of the Department of Geology 



Vol. 3, No. 16, pp. 377 381 ANDREW C. LAWSON, Editor 



A NOTE ON THE 



FAUNA OF THE LOWER MIOCENE 

 IN CALIFORNIA 



BY 



John 0. Merriam 



In nearly all typical sections of the Californian Miocene it is 

 possible to distinguish at least two divisions of the system based 

 on the geological range of faunas. At least three faunal zones 

 can be recognized in Contra Costa County, if we include the 

 variation in fauna due to change in the character of the sea 

 bottom during the deposition of the Monterey shale. This 

 does not mean that there are only two divisions possible, or that 

 the two mentioned are the same two in different sections, but 

 rather that we are certainly dealing with more than one distinct 

 zone. 



One of the most characteristic phases of the Miocene in Cali- 

 fornia is the Monterey shale. The fauna of this formation, as 

 we know it, is limited to foraminifera, radiolaria, fish, cetaceans, 

 a crustacean and a few mollusca. Among the last, Pecten 

 peckhami, the indefinite Tellina congesta and a Leda are the 

 most common forms. The fauna belongs to a deep water fades 

 and must not be confused with the faunas of sandy, shallow 

 water deposits. At many places where sandstone is interstratined 

 with the shales a very sudden change of the fauna is noticed, 

 nearly all of the typical shale species dropping out but reappearing 

 in shaly layers above. 



