50 University of California Publications in Geology I. Vol. 7 



typical soft, light diatomaceous earth, such as is characteristic 

 of the Monterey in the many parts of the state. The lower part 

 of this shale band is very diatomaceous, the most common diatom 

 present is of the genus Coscinodiscus. The upper portion of this 

 member is more argillaceous and darker in color; diatoms are 

 absent and leaf impressions are quite common. Fish scales and 

 vertebrae are very common through the shale. Thus far, only 

 two species of invertebrates have been found in the shale ; these 

 are Leda cah ill ensis Arnold, and an ophiuroid. The latter 

 appears to be a species found commonly in the Monterey near 

 Pinole Station on San Pablo Bay. These two species, taken with 

 the lithologic character of the shales, indicate that the beds are 

 Monterey. 



Carbonaceous Shales and Sandstones. — The shale just de- 

 scribed in the Kirker Creek section grades up into a series of 

 massive sandstones alternating with thin layers of shale and 

 clay. The sandstones are, for the most part, soft, of a medium- 

 coarse texture, massive, and vary from a gray to a yellow- 

 brown color. The shales and clays interbedded with the sand- 

 stones show considerable variation. Some of the layers of the 

 shale are black, others are nearly pure white. Carbonaceous 

 material, and impressions of leaves and wood are abundant in 

 many parts of this zone, and it appears that the beds were 

 deposited under estuarine or fresh-water conditions. The com- 

 bined thickness of this part of the section and the shale below 

 is roughly estimated as 1000 to 1200 feet. 



Tuffaceous Shales and Sandstones. — Above the shales and 

 massive sandstones just described is a series of white ash-beds, 

 tuffaceous shales, and fine tuffaceous sandstones. These beds 

 in the vicinity of Kirker Creek have a thickness of about 400 

 feet. They were included by Turner and by "Weaver in the 

 San Pablo formation. The results of the writer's work show 

 that they belong to the Monterey, and lie uneonformably below 

 the San Pablo. 



The following is a section seen in these tuffaceous sandstones 

 and shales about one mile to the west of Kirker Creek (SW 14, 

 Sec. 3, E. 1 B, T. 2 S). At the base of these beds, imme- 

 diately above the massive sandstones and shales already de- 



