100 University of California Publications in Geology [Vol. 11 



unconformably by younger strata. South of Panoche Creek, it is overlain by 

 the Vaqueros formation (early Miocene), with which it shows distinct angular 

 unconformity. This unconformity is widespread and represents one of the major 

 breaks in the sedimentary record in this region. Distinct angular discordance in 

 dip was noted at several places (see pi. 9) and near Ciervo Mountain the basal 

 beds of the Vaqueros formation, westward from the edge of the San Joaquin 

 Valley, lies on successively lower beds of the Kreyenhagen shale. "i 



The fauna of the Vaqueros of this region is that of the Turritella 

 ocoyana zone. 



SAN LORENZO OF SAN EMIGDIO HILLS 



Beds of San Lorenzo age are present in the San Emigdio Hills at 

 the south end of the San Joaquin Valley in Kern County, California. 

 Apparently the first to recognize and differentiate the beds in that 

 general region which contain the San Lorenzo fauna were Clark Gester 

 and E. G. Gaylord. During the summer of 1917 a party from the 

 University of California visited this section and spent several weeks 

 mapping the Eocene, Oligocene and Lower Miocene formations. Large 

 invertebrate collections were obtained especially from the Lower Mio- 

 cene and Oligocene. The results of this work will be published in 

 the near future. The fauna of the San Lorenzo was found in beds, 

 which are unconformable below beds containing the fauna of the 

 Lower Miocene. The maximum thickness of these Oligocene beds, 

 found in the vicinity of San Emigdio Canon, is between 2500 and 

 3000 feet. 



SAN LORENZO FORMATION OF THE SANTA CRUZ MOUNTAINS 



Reference has already been made to the type section of the San 

 Lorenzo, the fauna of which was first listed and described by Ralph 

 Arnold (see p. 62). This fauna is undoubtedly very near to, if not 

 contemporaneous with, that of the San Lorenzo beds in the vicinity 

 of Mount Diablo. A discussion of this relationship will be found 

 on page 101. 



Thirteen species of invertebrates were listed by Arnold from beds 

 designated by him as transitional Oligocene-Miocene ; of these, all the 

 determinable species are found in the San Lorenzo. Much more work 

 must be done on this section before the stratigraphic relationships of 

 the different horizons, including the Oligocene and Lower Miocene, 

 can be established for a certainty. At the present time the writer 

 is inclined to doubt that these so-called transitional Oligocene-Miocene 

 beds are really transitional. 



