56 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA. 
zuma is filled with good water, and a tunnel near by furnishes a little 
stock water tainted with ferrous sulphate. Alkali Spring has already 
been described (p. 19). Springs flow from the mountain slopes near 
Lida. and the water table in the canyon below the village is in many 
places but 30 to 100 feet below the surface. 
GENERAL GEOLOGY. 
The formations exposed in these mountains, from the oldest to the 
youngest, include: Cambrian sedimentary rocks, post-Jurassic gran- 
ite and gray quartz-monzonite porphyry, white quartz-monzonite 
porphyry, diorite porphyry, andesite, older rhyolite and dacite, 
Slebert lake beds, younger rhyolite, and basalt. 
SEDIMENTARY ROCKS. 
Cambrian. — The dominant rocks of these mountains are limestones, 
shales, and quartzites, in part at least of Cambrian age, and in the 
series no break in the process of sedimentation is apparent. West of 
Montezuma Peak these rocks consist of 1,000 feet of limestone with 
some -hale beds near it- top, overlain by 1,000 to L,200 feet of shale 
with some interbedded limestone layer-. A bed of white quartzite 
of fine to medium grain, '<> Heel thick, occurs near the middle of the 
upper shale member. Neither bottom nor top of this series is exposed. 
Quartzite is more prominent in (he hills southwest of Alkali Spring, 
where it is as abundant as -hale. 
The limestone \< dark gray, compact, and fine grained. The weath- 
ered rock is medium gray in color, except in mineralized portions, 
where the reds, yellow.-, and brown- of iron -tains are characteristic. 
Much of it is siliceous and grade- into a black, dense secondary jasper- 
oid of conchoidal fracture. The lime-tone is massively bedded, ex- 
cept where interlaminated with shale, where it is usually in rather 
thin beds. Gray lenses and nodules of flint form one-third of the 
limestone mass 6 miles north of west of Montezuma Peak. By the 
addition of clay the limestone passes into calcareous shale and finally 
into shale. 
The thin-bedded slaty -hales a. re of fine, even grain and of gray or 
olive-green color. In many places museoyite plates are present upon 
bedding plane-, and semischistose facies are developed by further 
formation of muscovite. Where joint planes are closely spaced the 
shale breaks into pencil-like fragment-. Locally weathered surfaces 
are stained red or brown by iron compound-. With increase in size of 
grain and in content of quartz the shales pass into dense argillaceous 
quartzites of greenish-gray to black color and fine to medium grain. 
Cross-bedding is in places well developed. 
The character of the rocks and the series of alternations of various 
rocks across the bedding planes indicate that the Cambrian rocks w ere 
