AMARGOSA RANGE, SEDIMENTARY COCKS. 
the limestone. A thin bed of white quartzite is interbedded with 
the limestone in the lower part of the series at Cave Rock Sprint. 
Similar quartzite and black flint occur in the limestone north of 
Grapevine Springs. 
The Pogonip limestone is rather fossiliferous, the fossils being of 
Ordovician age. From the limestone north of Grapevine Springs 
poorly preserved fossils were collected, which Mr. E. (). Ulrich 
identified as Orthoceras olorus and 0. perroti, other Orthoceras 
fragments, and a fragment of a pelecypod probably of the genus 
Clionychia. These fossils indicate a middle Ordovician horizon. 
Mr. F. B. Weeks collected Ordovician fossils from the main Paleo- 
zoic area, 5 miles southeast of the Staininger ranch, and Mr. G. K. 
Gilbert h collected fossils in Boundary Canyon which he considered 
early Silurian or Cambrian. 
Eureka quartzite. — Overlying the Pogonip limestone near Bound- 
ary Canyon is about 800 feet of quartzite. It is well exposed at 
Daylight Spring and is a pink, rather pure quartz rock of medium 
grain. The bedding planes, which are rather massive, are empha- 
sized by many fine laminae varying slightly in color and in size 
of the constituent grains. Conglomeratic bands containing well- 
rounded pebbles one-half inch in diameter occur. Some of the peb- 
bles are of quartzite, possibly derived from Cambrian rocks. Thin 
layers of black" fine-grained argillaceous quartzite and of olive- 
green or brown slaty shales are also interbedded with the normal 
quartzite. This rock is correlated, with considerable confidence, 
with the Eureka quartzite (Ordovican). 
Lone Mountain limestone. — Overlying the supposed Eureka 
quartzite in the vicinity of Keane, Daylight, and Willow springs 
is about 300 feet of limestone which resembles the Pogonip closely, 
although less distinctly bedded. This is probably the Lone Mountain 
limestone 6- of the Eureka section. The inlier 4 miles north of the 
Staininger ranch is composed of fine-grained dark-gray limestone, 
with interbedded black flint, white or pink quartzite, and limy 
shales. Imperfect silicified fossils, one of which Mr. E. O. Ulrich 
considers a late Silurian coral (genus Cladopora), were collected 
by the writer from this locality. Other small inliers in this vicinity 
may in realty be the Lone Mountain limestone rather than the 
Pogonip. 
Siebert lake beds and contemporaneous deposits. — The rather large 
mass of later rhyolite and biotite latite to the southeast of Stainin- 
gers Ranch has between its flows layers of white or light-colored in- 
«.Spurr, J. E., Bull. U. S. Geol. Survey No. 208, 190:;. p. 188. 
» Gilbert, G. K.. U. S. Geog. Survey W. 100th Mer., vol. 3, 1875, pp. 34, 169, IS] 
c Hague, Arnold, Mon. U. S. Geol. Survey, vol. 20, 1892, pp. .17-59. 
