214 GEOLOGY OF THE EUREKA DISTEICT. 



accumulations. These, from their position resting directly upon the quartz- 

 ites, have been referred to the Lone Mountain beds. The Spring Valley 

 fault brings these Silurian beds up against the Cambrian of Prospect Ridge. 

 The section intersects Prospect Ridge just to the north of the summit of 

 Prospect Peak and brings out the anticlinal structure in the quartzite on 

 the west slope overlain on both sides of the fold by the Prospect Mountain 

 limestone which on the west side comes down to the line of the Spring Val- 

 ley fault. Prospect Mountain limestone here forms the summit of the 

 main ridge. This is in turn overlain by Secret Canyon shale, Hamburg 

 limestone, and Hamburg shale, the remaining subdivisions of the Cambrian, 

 all of which stand inclined at about 70 to the east. As the section is 

 drawn across quite a high saddle at the head of New York Canyon, con- 

 necting Prospect Peak with Hamburg Ridge, the erosion of the Secret 

 Canyon shale, which is so marked a feature of the region, is not so well 

 shown as it would be if the section were drawn either to the north or south 

 of this point, but it is sufficient to bring out the prominence of the Ham- 

 burg Ridge, which is everywhere parallel to the main ridge. Overlying 

 the Hamburg shale occurs the Pogonip limestone and the Eureka quartzite, 

 the latter occupying the slope down to the Hoosac fault. 



At the base of the long uniform slope of Pogonip limestone, which is 

 well shown in the surface outline, the line of the section has been moved 

 northward 700 feet, in order to illustrate to better advantage several struc- 

 tural features. By thus moving this line the Eureka quartzite is shown on 

 both sides of the homblende-audesite body, which in breaking out along 

 the Hoosac fault has shattered the quartzite all along the fault. Immedi- 

 ately along the line of the section only a small outcrop of the quartzite 

 occurs to the east of the andesite, but by reference to the geological map it 

 will be readily seen that the exposure forms a part of a continuous body of 

 considerable extent. East of the fault the Carboniferous limestones come 

 up dipping easterly, but separated from the main body by a minor fault, 

 which, so far as can be determined, is accompanied by only a slight dis- 

 placement. This is followed by a synclinal fold, described elsewhere, 

 lying between Spring Hill and the Pinto fault. Continuing along the 

 line of the section east of the Pinto fault the Lone Mountain limestones rise 



