Vol. 4] Smith. — Upper Region of Main Walker River. 



deposits. It is in this ridge that the best exposures of the lime- 

 stone occur. There is presented in one place about eight hundred 

 feet of its thickness, and as to bow much thicker it may be was 

 not ascertained. Capping all these rocks and debris is basalt. 

 The debris is very susceptible to erosion, and is readily carried 

 away, the basalt being thereby readily sapped. West of the 

 summit, at the Ludwig Mine, iron ore again occurs with lime- 

 stone, as it did in the first ridge, only in this case its strike is 

 continuous with that of the limestone. It is also continuous 

 with the limestone in depth, so far as could be ascertained from 

 the mine openings, which had a depth at the time the writer was 

 there of about four hundred feet. The continuation of this ridge 

 south of the map consists of granite intrusives, some sedimen- 

 taries, quartz-porphyry and basalt. One of these intrusives was 

 found containing an inclusion of granite-porphyry. The investi- 

 gation of the ridge was not continued south of the Hutson Pass 1 , 

 which is about six miles south of the area covered by the map 

 PI. 1. The Superjacent Series, in this ridge, is represented 

 by tuff, andesite, earlier and later, rhyolite, Tertiary beds and 

 basalt within the area of the map ; but these rocks do not extend 

 the entire length of the crest line. From Mickey Pass south- 

 ward the latter is continued by several members of the Bedrock 

 Complex; as, for instance, several granites nearly alike, granite- 

 porphyry and some more basic intrusives. The limestone, how- 

 ever, lies a little lower'. The two major divisions, the Bedrock 

 Complex and the Superjacent Series, are probably not better 

 represented within the region as to the number of formations 

 comprised, but the relative sequence of the rhyolite and the 

 basalt of the Superjacent Series is better seen in other parts of 

 the territory. 



The Third Ridge. — The third or easternmost ridge is along the 

 eastern margin of the map PI. 1. Its northern end is merely a 

 chain of buttes which, it may be said, begin at the base of a very 

 considerable ridge which has a trend at right angles to those that 

 have been so far mentioned. Unfortunately, it was not possible 

 to make an excursion to this quarter, and their mapping is accord- 

 ingly hypothetical. Some schist, metamorphosed sandstone, 



1 See U.S.G.S., Wellington Atlas sheet, 



