DIAMOND PEAK QUAETZITE. 85 



Diamond Peak Quartzite.-Tliis epoch, tlie basc of the sories, ttikes its name 

 from Diamond Peak, where it is exposed on both flanks of the peak, dip- 

 ping into the range with a synclinal structure. On the west side of the 

 peak, where it attains its greatest exposure, it measures about 3,000 feet in 

 thickness. Beds of this epoch are found only at Diamond Peak and on 

 the opposite side of the valley in the region of The Gate. At the base of 

 the horizon fine conglomerates firmly cemented together lie next the argil- 

 laceous shale of the White Pine epoch, but quickly give place to a more 

 massive, usually vitreous, quartzite with a characteristic grayish brown color 

 and breaking irregularly with a flinty fracture. Intercalated l)lack cherty 

 bands, carrying a more or less ferruginous matter, occur near the middle 

 jK)rtion of the horizon. Near the summit the beds pass into thinly 

 laminated green, brown and chocolate-colored schists and clay shales. The 

 Carboniferous age of the epoch is determined by a narrow lielt of blue 

 limestone, which occurs interstratified in the quartzite about 200 feet above 

 its base, in which the widespread species Productus semireficulatus occurs 

 associated with an undetermined species of Athijrls. As the fauna at the 

 top of the black shales foreshadows the coming in of the Carboniferous, the 

 presence of this characteristic Frodudiis, with oidy a Carboniferous fauna 

 higher up in the series, determines without question the geological position 

 of the quartzite between the black shale and Coal-measure limestone. 



Lower Coal-measure Limestone.— Beds of this epocll are folUld iu a great 



number of ranges in Utah and Nevada, stretching all the way from the 

 Wasatch to Battle Mountain, and the horizon has probably been better 

 studied than any other in the Great Basin. The beds cover large areas at 

 Eureka and off'er better exposures than any other division of the Carbon- 

 iferous. In the Diamond Range they overlie conforinably the Diamond 

 Peak quartzite, the transition beds passing rapidly from siliceous to cal- 

 careous sediments. In their lithological character and physical habit they 

 do not differ essentially from the same beds elsewhere, except, jJerhaps, 

 at theii" base, where they carry intercalated beds of chert, argillite, and 

 gritty, pebbly limestone, with evidences of shallow water deposition. They 

 pass rapidly, however, into purer gray and blue limestone, for the most 

 part hea-vnly bedded and distinctly stratified at A-arying intervals. In 



