PKOSPEOT KIDGE SECTION. 101 



Ruby Hill Fault. This fault starts in near the reservoir in New York 

 Canyon, branching out from the Hoosac fault and running in a northwest 

 direction. It cuts diagonally across the Pogonip limestone, and abruptly 

 terminates the Hamburg limestone and Hamburg shale, which form such 

 persistent topographic features of the country to the southward, and inter- 

 sects the Jackson fault near the American shaft, just south of the Jackson 

 mine (atlas sheet vm). For a short distance this fault apparently coincides 

 with the Jackson fault, then crosses it, following a northwesterly direction 

 the same course it held before the intersection with the great north and south 

 fault. On Ruby Hill the fault may be traced in the underground workings 

 of all the principal mines through to the Albion. It has exerted a most 

 powerful influence upon the structure of Ruby Hill, and from its relations 

 to the ore bodies its importance from a mining point of view can not be 

 overestimated. Reference will be made to this fault in the discussion on 

 the geology of Ruby Hill. 



From Spring Valley eastward across Prospect Ridge and Hamburg 

 Ridge to the Hoosac fault, the highly inclined strata offer an unbroken 

 geological section from the lowest beds of the Cambrian to the Eureka 

 quartzite of the Silurian. It offers the best section to be found in Nevada 

 of the Cambrian rocks, with all the epochs into which it has been divided 

 clearly denned. Sections across Prospect Mountain limestone may vary 

 greatly in details within a few hundred feet in the relative thickness of 

 compact limestone and calcareous shaly beds, but in general the sections 

 across the entire thickness of the horizon coincide fairly well. 



Section CD-EF (atlas sheet xui), constructed across the central portion 

 of the Eureka Mountains, intersects Prospect Ridge about 3,000 feet to the 

 north of the peak, at a point selected to bring out the anticlinal structure of 

 the mountains. The underlying quartzite is overlain on both sides of the 

 fold bv the Prospect Mountain limestone, which on the west side extends 

 down to Spring Valley, while on the opposite side it forms not only the 

 summit, but the entire east wall of the main ridge. This is in turn over- 

 lain by the remaining subdivisions of the Cambrian, all of wlxich stand 

 inclined at a uniformly high angle to the east. As the section is drawn 

 across a high saddle at the head of New York Canyon, connecting Pros- 



