178 GEOLOGY OF THE EUREKA DISTRICT. 



Nature of Material. The 30,000 feet of sediments at Eureka between the 

 base of the Prospect Mountain quartzite and the summit of the overlying 

 Upper Coal-measure limestone are made up of well denned bodies of sili- 

 ceous, calcareous, and argillaceous strata, each representing a distinctive 

 epoch in the geological history and development of the region. These 

 rock masses grouped according to the character of their sediments show 

 clearly the relative amount of the three classes of deposits into which sub- 

 aqueous sediments may be divided. 



SILICEOUS. 



Feet. 



Prospect Mountain (Cambrian) 1, 500 



Eureka quartzite (Silurian) 500 



Diamond Peak quartzite (Carboniferous) 3, 000 



Weber conglomerate (Carboniferous) 2, 000 



Total 7, 000 



CALCAREOUS. 



Prospect Mountain limestone (Cambrian) 3, 050 



Hamburg limestone (Cambrian) 1, 200 



Pogonip limestone (Silurian) 2, 700 



Lone Mountain limestone (Silurian) 1, 800 



Nevada limestone (Devonian) 6, 000 



Lower Coal-measure limestone (Carboniferous) 3, 800 



Upper Coal-measure limestone (Carboniferous) 500 



Total 19, 050 



ARGILLACEOUS. 



Secret Canyon shale (Cambrian) 1, 600 



Hamburg shale (Cambrian) 350 



White Pine shale (Devonian) 2, 000 



Total 3, 950 



For the most part the siliceous formations are composed of pure quartz- 

 ites, sandstones, or conglomerates, interstratified beds of foreign material 

 occupying very inferior positions. Oil the other hand the calcareous and 

 argillaceous deposits are more or less interrupted by occasional belts of 

 other material or impure layers of mixed sediments occurring as transi- 

 tion beds. 



