442 



University of California Publications in Geology 



[Vol. 8 



in the Lower Jacalitos ( ?). If these beds, which appear to be land or 

 estuarine in origin, prove to be of the same age as those of the typical 

 Jacalitos on Jacalitos Creek to the southwest of Coalinga, then possibly 

 we may be able to determine the upper limit of the San Pablo quite 

 accurately. 



Another horizon from which land vertebrates were obtained was in 

 the type section of the Etchegoin. Horse teeth of the genus Proto- 

 Mppus, together with a number of other forms, were secured in the 

 basal beds of the Etchegoin. This fauna together with the vertebrate 

 evidence of the basal beds of Jacalitos?, stratigraphically 1800 feet 

 lower, shows quite conclusively that the Etchegoin is distinctly Plio- 

 cene rather than Miocene. 



Probably the best evidence showing the age of the uppermost beds 

 of the San Pablo of Middle California comes from vertebrate material 

 obtained in the fresh-water beds which in Middle California overlie 

 unconformably the San Pablo Group. This material was described by 

 Professor J. C. Merriam 48 in his paper "Vertebrate Fauna of the 

 Orindan and the Siestan Beds in Middle California." His conclusions 

 as to the age of these beds as shown by the vertebrates was as follows : 



The mammalian remains known from both the Orindan and Siestan up to 

 the present time all represent forms such as might be expected in the late 

 Miocene or in the earliest Pliocene, but it will be necessary both to have better 

 material from the Orindan and Siestan and to have well-known faunas of 

 western Miocene and Pliocene for comparison before the last word on the age 

 determination can be pronounced. 



Considering the indefiniteness of all the factors concerned, one would not 

 seem justified in being more definite than to state that the Orindan and Siestan 

 faunas are near a late Miocene stage. When the faunas of the two formations 

 are better known, it may appear that more than one stage is represented. 



CONCLUSIONS 



(1) The San Pablo division should be designated a group rather 

 than a formation, as these terms are used by the United States Geo- 

 logical Survey. 



(2) The Neocene of California is divisible into at least three dis- 

 tinct stratigraphic groups, which in this paper are called Lower, Mid- 

 dle, and Upper Neocene ; the San Pablo group represents the Middle 

 Neocene ; the Lower Neocene is represented by the Monterey group, 

 including the Vaqueros, Temblor, and Monterey shale ; the Upper 



•is Univ. Calif. Publ. Bull., Dept. Geo!., vol. 7, no. 19, pp. 384-385, 1913. 



