76 



University of California Publications. [Geology 



however, is a syncline of pumiceous tuff resting conformably on 

 typical San Pablo strata, and of identical appearance to that 

 beneath the Orindan gravels at Pinole and southward, and in 

 this tuff Dr. Merriam recently found horse-teeth of more recent 

 type than those from the Orindan gravels. He thinks that they 

 cannot be older than Pliocene. No gravels occur with the tuff 

 at Rodeo. 



Proceeding on this assumption, therefore, the writer corre- 

 lates the fresh-water deposits beneath the Mark West Andesite 

 on the eastern side of Santa Rosa Valley with the Orindan. 



If the above correlation is correct, it is evident that the gap 

 between San Pablo and Merced is somewhat bridged over, but 

 the writer thinks it premature to attempt at this time any cor- 

 relation of his intervening formations with those of the Berkeley 

 Hills, such as the Berkeleyan. 



QUATERNARY. 



It was not found possible with the scale used to adequately 

 represent the Quaternary deposits. All of the streams of the 

 territory under discussion show terraces, usually covered with 

 flood-plain deposits, while the shores of the bays and estuaries 

 frequently show wave-cut terraces covered with gravels and 

 •sands. 



Tomales Bay Deposits. — According to Anderson, the Pleisto- 

 cene deposits in the vicinity of Tomales Bay consist of "Coarse 

 arkose detritus with an indistinct horizontal stratification. They 

 are found generally in the larger depressions of the peninsula, 

 and range in elevation from 500 feet downward. They form a 

 series of low, broad hills, extending along the middle of the 

 valley near Olema, and occur at intervals upon both shores of 

 Tomales Bay, forming there a system of low, bench-like terraces 

 below 200 feet in height. West of the main ridge they are found 

 in occasional patches around the flanks of the hills at the head 

 of Drake's Estero and north of Abbott's Lagoon." 



Bodega Bay Deposits. — At Bodega Bay similar deposits to 

 those mentioned by Anderson occur on both sides of the bay, but 

 only in small patches, most of them having been removed by 

 erosion. Near Bodega Point on the bay side is a remnant resting 



