1915] 



Clark: Fauna of the San Pablo Group 



429 



Ashley did not separate the fauna of the transition beds from that 

 of his typical Pliocene beds. That he believed his Merced series rep- 

 resented the entire Upper and Middle Neocene is shown by the fol- 

 lowing' quotation from page 322 of the paper just cited : 



It seems possible that most of the beds from which the older Pliocene have 

 been reported will be found to correspond to this series. Thus the fauna from 

 Kirkers Pass and Green Valley, Contra Costa County, Santa Eosa and Russian 

 River, Sonoma County, would suggest the presence of the Merced series. 



Dr. J. C. Merriam, 26 in a paper on the Neocene sea-urchins of 

 California, appears to have been the first person to recognize two 

 distinct faunal zones above what is here designated Lower Neocene. 

 He points out that the San Pablo is without doubt older than the 

 Merced, the type section of which is just across the bay from that of 

 the San Pablo. 



In 1903 Dr. W. H. Fairbanks 27 described, under the name San 

 Pablo, a formation in San Luis Obispo County, which he correctly re- 

 garded as the equivalent of at least a part of the San Pablo of Mer- 

 riam. The following year, however, he described these beds under 

 the names Santa Margarita and Pismo formations, placing these in 

 what he termed the San Pablo group. 



In 1904, H. L. Haehl and Dr. Ralph Arnold 28 subdivided the Merced 

 series of Ashley in the Santa Cruz Mountains into the Purisima 

 formation below (5000 ft.), and Merced formation above (5000 ft.). 

 The upper limit of the Purisima was placed in that part of the section 

 regarded by them as corresponding to the base of the type Merced at 

 Seven Mile Beach. 



From this time on there was considerable confusion as to whether 

 or not the faunas of the Purisima and of the Merced in the Santa 

 Cruz Mountains represented respectively the San Pablo and Merced as 

 differentiated by Merriam. 



In 1905, Mr. F. M. Anderson 20 published a paper entitled "A 

 Stratigraphic Study in the Mount Diablo Range of California." This 

 was followed in 1908 by a paper entitled "Further Stratigraphic 

 Study in the Mount Diablo Range of California." In these papers 



26 Bull. Dept. Geol. Univ. Calif., vol. 2, no. 4, pp. 109-118, 1898. 

 - 7 " The Stratigraphy of the California Coast Ranges," Journ. Geol., vol. 3, 

 no. 4, p. 415, 1903. 



28 ' ' Miocene Diabase of the Santa Cruz Mountains in San Mateo County, Cali- 

 fornia, " Proe. Am. Phil. Soc, vol 43, pp. 15-53, 1904. 



29Proc. Calif. Acad. Sci., 3d series Geol., vol. 2, no. 2, pp. 156-246, 1905. 

 Proc. Calif. Acad. Sci., 4th series Geol., vol. 3, pp. 1-40, 1908. 



