430 University of California Publications in Geology [Vol. 8 



he divided the Upper Neocene on the east side of the Coast Ranges in 

 the vicinity of Coalinga, in ascending order, into the Coalinga beds, 

 and the Etchegoin formation, correlating the former with the Upper 

 Miocene and the latter with the Pliocene. Later work in this field 

 has shown that in the region to the northwest of Coalinga, a part of 

 the area mapped by Anderson as Coalinga beds in reality belongs to 

 his Temblor formation, Lower Neocene. To the west and southwest 

 of Coalinga the beds mapped as Coalinga are in part equivalent to 

 the beds mapped by Arnold and Anderson as Jacalitos, a formation 

 to which reference will be made later. Anderson believed the Coalinga 

 beds to be equivalent to the Santa Margarita of Fairbanks, but doubted 

 their equivalence to the San Pablo. On pages 39 and 40 of the second 

 paper cited above, he says : 



In the former paper the San Pablo, as known from its type localities, was 

 correlated with the Etchegoin; and this seems to be its closest ally among the 

 stratigraphie series farther south, while in the Salinas Valley and elsewhere, 

 beds that have been generally called San Pablo and otherwise correlated with 

 it, are undoubtedly more closely related to the Coalinga. The type locality of 

 Ostrea titan, Tamiosoma gregarea, Pecten estrellanus, P. crassicardo and many 

 other species described by Conrad, was the Estrella Creek where Coalinga beds 

 are abundantly fossiliferous. It yet remains to be shown that these beds are 

 properly correlated with the San Pablo of the type localities; whereas, the 

 fauna of the Coalinga beds are unmistakable in them, as in the Santa Mar- 

 garita beds. ' ' 



In 1906, Arnold 30 published a paper on "The Tertiary and Quar- 

 ternary Pectens of California," in which he gives a brief review of the 

 stratigraphy and palaeontology of the Tertiary formations of Cali- 

 fornia. He recognizes the probable equivalency of the San Pablo to 

 the Santa Margarita of Fairbanks, but is undecided as to the relation 

 of the San Pablo to the Purisima. On page 25 he states : 



Much uncertainty exists in the mind of the writer as to the exact relation 

 existing between the Purisima and San Pablo formations. After a careful 

 examination of a large amount of material from the type locality of the two 

 formations, and also from the supposedly equivalent formation in the Salinas 

 Valley and adjacent regions, supplemented by field studies at most of the 

 localities from which the material was obtained, it appears evident that the 

 two formations are quite intimately related. It is a complex problem and is 

 one which will require careful field and laboratory study for its solution. The 

 Purisima fauna, taken as a whole, appears to be younger than the aggregate 

 San Pablo fauna and for the sake of convenience will be considered as the 

 later of the two. 



so U. S. G. S. Prof. Paper 47, 1906. 



