42 



University of California Publications. 



[Geology 



the boundary line between Napa and Lake Counties to Knox- 

 ville ; continuing' in this same general northeast direction, pass- 

 ing through the high ridge between Knoxville and the north end 

 of Capay Valley at Rumsey, and thence through the low rolling 

 foothills to the Sacramento Valley and Arbuckle, a distance in 

 all of about eighty miles. 



Section CD starts at a point about midway along the west 

 shore of Point Reyes Peninsula, and runs northeast across To- 

 males Bay, continuing over the high ridge and rolling foothills 

 for about fifteen miles, to the valley at Petaluma, thence, swing- 

 ing a little more to the eastward, it passes through a low series 

 of hills and crosses Sonoma Valley, some three miles south of 

 the town of Sonoma ; thence northeast to Napa City, continuing 

 across Napa Valley, through the high ridge to the east to Wooden 

 Valley and the upper end of Gordon Valley; through the promi- 

 nent vidge separating the latter from Pleasant Valley, and thence 

 through the rolling hills to the Sacramento Valley at Winters, a 

 distance in all of about sixty-five miles. 



Together the sections enclose an area of about fifteen hun- 

 dred square miles, and since, as displayed in the graphical repre- 

 sentations of the sections, there appears to be a well marked con- 

 tinuity of formations, it is believed that the geology is fairly 

 typical of the Coast Ranges for a considerable distance north 

 and south of the lines chosen. 



The geological formations encountered in these sections range 

 from pre-Franeisean to Pleistocene. They will be described in 

 chronological order. 



PRE-FR ANCISCAN. 



SEDIMENTABLES. 



The oldest rocks known anywhere in the territory are a few 

 small remnants of limestone and crystalline schists described by 

 Anderson* in his paper on Point Reyes Peninsula. According to 

 him, they consist of a "Marble similar to the white crystalline 

 limestone of Montara Mountain and the limestone of Santa Cniz 

 and the Santa Lucia Mountains." Associated with these lime- 

 stones is quartzite, and at another place mica-schist and wollas- 

 tonite schists are found overlying the granite. 



*Bull. Dept. Geol., Univ. Cal. Vol. 2, No. 5. 



