84 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA. 
canyons radiate from the central peak, ending at the alluvial slopes 
2,500 to 8,000 feet below. The most striking feature of the moun- 
tain is the fault scarp at Stonewall Spring, a sheer wall 800 to 1,000 
feet high. Erosion has cut partially through this scarp, forming a 
narrow V-shaped gap, the lowest point of which i> at least 100 feet 
above the stream bed in the south. Behind this wall the valley is 
broad and U-shaped, regaining its V shape some distance back in the 
mountains. Other streams near by are characterized by narrow can- 
yons, which open upstream into more mature valleys. 
The mountain- above an elevation of 6,100 feet are clothed with a 
sparse although locally heavy growth of juniper, pihon, and mountain 
mahogany. Excellent pasturage covers the higher peaks and valleys. 
Groves of the tree yucca occur on alluvial slopes to the west and on 
Pahute Mesa to the southeast. Stonewall Spring yields daily about 
3,000 gallons of pure cold water. A stream 100 yards long flows 
from a spring in the gulch one-half mile east of Stonewall Spring. 
Another spring is located 1 mile west of the culminating peak of the 
range. 
GENERAL GEOLOGY. 
The formations of Stonewall Mountain are, in ascending order, 
Cambrian lime-tone. post-Jurassic granitoid igneous rocks, earlier 
rhyolite, quartz syenite and quartz-monzonite porphyry, Siebert lake 
beds, later rhyolite. and basalt. 
SEDIM ENTAEY RO< K s. 
Cambrian. —Three -mall masses of dark-gray crystalline limestones 
cut by many white calcite veinlets, protrude from the igneous rockj 
near the north edge of the mountain. Angular inclusions of lime* 
-tone and jaspilite are embedded in the older rhyolite. the monzonitf 
porphyry, and the basalt. The lime-tone i> similar lithologically to 
that of the Cuprite mining district, and, like it, is probably of Cam- 
brian age. In contact with quartz-monzonite porphyry, near the 
northwest boundary of the mountain mass it has been metamorphosed 
to a white marble containing epidote. 
Siebert lah c beds. — Incoherent, well-bedded tuffaceous sandstones 
and conglomerates of red, yellow, white, and greenish-white color 
cover a -mall area east of Stonewall Spring. The bowlders, which 
are well rounded to semiangular, are largely of the earlier rhyolite. 
A thickness of about 500 feet i- exposed. These beds are without 
much doubt the equivalent of the Siebert lake beds. 
[GNEOl S BOCKS. 
Post-Jurassic granite and granite porphyry. — A few inclusions of 
granite occur in the earlier rhyolite and prior to the extrusion of 
that rock granite may have been exposed in these mountains. A nar- 
