258 



University of California Publications. 



[Geology 



CORRELATION. 



The San Pablo formation is characterized faunally by the 

 presence of seventy-three species and fifty-three genera, a large 

 number of which are peculiar to the San Pablo alone while others 

 range back into the Miocene or Monterey and many more have 

 survived to the present time and may be found in the living 

 fauna along the Pacific Coast of North America. A study of 

 the fauna collected at various horizons in the sections made at 

 several localities shows certain forms to be characteristic of the 

 lower beds and others of the upper. Whether this is sufficient 

 evidence for dividing the San Pablo into an upper and a lower 

 division is not certain, but it remains a fact that several dis- 

 tinctive and characteristic species are coufined to certain horizons 

 within the formation. At no one locality within the area studied 

 is it probable that the San Pablo formation in its entirety is 

 represented. 



Upon a palaeontologieal basis the strata at San Pablo Bay 

 may be divided into two divisions. Professor Merriam has al- 

 ready clearly shown the occurrence and range of the echinoids in 

 the section. Scutella gabbi appears to be confined to the lower 

 part of the formation, while the upper part is characterized by 

 the presence of Astrodapsis tumidus. Certain of the species seem 

 to be closely associated with the Astrodapsis beds and are not 

 present in the Scutella zone. Among those in this section are 

 Pecten pabloensis, Pectunculus near patxdus, Mulinea densata, 

 and Olivella boetica. Altogether seventeen species have been 

 collected from this section. 



In the Kirker's Pass locality the thickness of the strata as 

 measured in cross-section amounts to over one thousand feet. 

 Turner's estimate of six hundred meters is due to the fact that 

 he included in the San Pablo formation the uppermost division 

 of tuffs and ashes, which are here placed in the Pinole Tuff. 

 Forty-nine species were collected from the Kirker's Pass section. 

 Nearly all of these came from the layer B of Turner, which 

 overlies the white chalky shales and underlies the volcanic con- 

 glomerates and sandstones. The lower division, or rather the 

 Scutella gabbi zone, which occurs in the San Pablo Bay district, 



