CHAPTER V. 

 DESCRIPTIVE GEOLOGY. 



In the following- pages will be found a detailed description of the sed- 

 imentary rocks in the Eureka District, the order followed being- for the most 

 part the same as that adopted in the chapter devoted to tlie general 

 geoloo^ical sketch. Each orographic block is described by itself, beginning- 

 with Prospect Ridge, where the oldest rocks occur, followed bv the other 

 blocks according to the geological succession of strata; thu only changes 

 made in the oi-der of treatment being for the purpose of liringing out more 

 forcibly the sti-uctural relations of the individual blocks to eacli other. This 

 chapter necessarily contains a repetition of many facts state<l in other por- 

 tions of the volume, but at the same time there is an omission of man}- 

 details that, if not presented elsewhere, would properly find a place liere. 



The principal object of this chapter is to give a connected description 

 of the country and to place numerous details in permaneut form for the 

 use of those who may wish to study the field in person, or who may desire 

 to investigate more fully the facts upon which the generalizations ai-e based. 

 Certain portions of the country are described more fullv than others, and 

 in a few instances the descriptions follow closely those given elsewhere in 

 the volume. 



PROSPECT RIDGE REGION. 



This region includes all the country lying between the Hoosac fault 

 on the east side and the Spring Valley, Prosjiect ^lountain, and Sierra 

 faults on the west. These lines of faulting s]iarpl\- outHne a mountain 

 block which, in its geological structm-e, stands out on all sides clearh- 

 defined from the adjacent country. 



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