CHAPTER Vlir. 



DESCRIPTIVE GEOLOGY OF THE KNOXVILLE DISTRICT. 



[Atlas Sheet V.] 



General character. — Tliis clistrlct iucludes tliG poliit iit wliicli Napa, Lake, 

 and Yolo Counties meet. It presents the usual characteristics of the Coast 

 Ranges: low, rocky ridges, partially covered by brush and a scant}^ growth 

 of trees and divided by narrow valleys. Though some pleasing views are 

 to be had from the highe'r points, the region is not a picturesque one. It 

 possesses great geological interest, however, for it affords an admirable 

 opportunity for the determination of the age of the metamorphic sei'ies and 

 for a study of the processes of metamorphism. It also contains a series of 

 quicksilver deposits which show instructive features and which bear signifi- 

 cant relations to the metamorphic rocks and to basalt. 



The Knoxviiie series — The area embraced in the detailed map contains fos- 

 sils at a number of points, and study of the district shows that all of the 

 sedimentary beds are probably of the same age, belonging to one division, 

 the lower, of the Shasta group of Messrs. Galjb and Whitney. As has been 

 explained in Chapter Y, it is advisable to consider this series as wholly dis- 

 tinct from the Shasta beds on Cottonwood Creek, in Shasta County. It is 

 characteristically developed in the Knoxviiie district, where also it is the 

 only series exposed, and Dr. White and I have therefore christened it the 

 Knoxviiie group. The Knoxviiie beds form a very large part of the Coast 

 Ranges and of the auriferous .slates of the Sierra Nevada. 



A considerable portion of the rocks in this district are nearly or quite 

 unaltered and consist of predominant sandstones interbedded with shales 



