28 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA. 
CAMBRIAN. 
In the Specter Range from 2,000 to 3,000 feet of quartzite and con- 
glomeratic quartzite conformably underlie limestone containing Cam- 
brian fossils. The rather impure quartzite, which grades into minor 
beds of slaty shale, is probably the equivalent of the Prospect Moun- 
tain quartzite a described by Hague, from the Eureka district. Less 
certainly to be correlated with this formation is the quartzite with 
intercalated schist arid marble beds of the Amargosa and Panamint 
ranges, a rock series which may possibly be of pre-Cambrian age. 
Conformably overlying the Prospect Mountain quartzite in the 
Specter Range is a limestone apparently from 5,000 to 0,000 feet thick, 
which is probably to be correlated with the Prospect Mountain lime- 
stone a of Hague. The limestone is dark gray, compact, fine grained, 
and crystalline. Black chert occurs at certain horizons. In the Sil- 
ver Peak Range, Stonewall Mountain, the Goldfield, Southern Klon- 
dike, Lone Mountain, and Mount Jackson hills, and Slate and Gold 
Mountain ridges occur rocks that are in part at least of Lower Cam- 
brian age. The predominant member is a dense dark-gray limestone 
of finely crystalline texture. As a rule it is massively bedded. In a 
number of places this limestone has been silicified to a banded gray 
and black jasperoid. Tnterbedded with the limestone are layers of 
green slaty shale, usually finely Laminated. In the Silver Peak Range 
and the Lone Mountain foothills the shale reaches a thickness of 
1,000 feet. These rocks, in part at least, are the equivalent of* the 
Prospect Mountain limestone, although lithologically rather distinct 
from that formation in the type locality. 
Of less certain Cambrian age are the mica schists of the Bull frog- 
Hills, Tolicha Peak, and Trappmans Camp. The Secret Canyon shale, 
and the Hamburg limestone and shale were not recognized, and the 
Cambrian limestones appear to pass upward without distinct litho- 
logic break into the Pogonip limestone. 
ORDOVICIAN AND SILURIAN. 
The Pogonip limestone as describe'd by Hague h is 2,700 feet thick 
and contains Upper Cambrian fossils at its base and Orclovician fos 
sils in its middle and upper portions. At Eureka it overlies the 
Hamburg shale" conformably, while in southwestern Nevada it seems 
to succeed the Cambrian limestone without marked lithologic change. 
The Pogonip limestone is well exposed in the Belted, Amargosa, 
a Present usage of the Survey does not sanction the double use of formation names, as! 
Prospect Mountain quartzite and Prospect Mountain limestone, but as this reconnais- 
sance paper is not the place to propose new names, they arc retained as used by Hague. 
b Hague, Arnold, Mod. IT. S. Geol. Survey, vol. 20, pp. 4X-f>4. 
