166 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA. 
coherent tuffaceous sandstone, which readily breaks down into sand. 
The section at this point is as follows: 
Section southeast of Stainingers Ranch. 
Feet 
Lava, largely biotite latite 375 
Rhyolite flows and some tuffaceous sandstone 100 
Tuffaceous sandstone and thin rhyolite flows 375 
Rhyolite flows . 75 
Tuffaceous sandstone *. 225 
Between the lava and the sediments are minor erosional gaps, but 
these are probably current erosional unconformities, and the series is 
approximately all of one age. Bedding planes from 2 inches to 20 
feet apart are well developed at some places. 
Locally the tuffaceous sandstone lies unconformably upon folded 
Pogonip limestone. It is closely similar to that of the Mount Jack- 
son hills and. like it. i- overlain by siliceous lavas. This formation i^. 
without much doubt, the Siebert lake beds. 
A number of -mall areas of conglomerate occur on the eastern slope 
of the Amargosa Range, east of boundary post No. 94, southeast of 
Daylight Spring and north of Willow Spring. The rocks, varying 
from loosely to rather strongly consolidated material, consist of con- 
glomerates and arkoses with a little shale. They range in color from 
green to red, yellow, or brown. Bedding planes, which are from 1 
inch to 2 feci apart, are well developed. The pebbles in the conglom- 
erate, which are very well rounded and many of them highly polished, 
reach a maximum diameter of 4 inches. They are derived principally 
from the Paleozoic rock- near by, with here and there a pebble of fine- 
to medium-grained granite, and in the area east of boundary post No. 
94 some of earlier rhyolite. These rocks appear to be the shore de- 
posits of a lake in which waves swept with considerable force. Mate- 
rial was transported from considerable distances, since granite does 
not now outcrop in the vicinity. Since the conglomerate contains 
pebble- of rhyolite and none of basalt, the deposits are younger than 
the rhyolite (early Miocene) and older than the basalt (Pliocene- 
Pleistocene), and in consequence of middle or late Tertiary age, pre- 
sumably Miocene. They are approximately contemporaneous with 
the lake in which the Siebert lake beds were deposited, and it is be- 
lieved that they are shore deposits of that lake. The conglomeratic 
lake beds of the Funeral Mountains, south of the area mapped, are 
to be correlated with these conglomerates. 
Older alluvium. — From a point 8 miles north of Surveyors Well to 
a point o miles north of Mesquite Spring the western flank of the 
Amargosa Range i> formed of older alluvium, and the same forma- 
tion covers a considerable area west of boundary post No. 85. This 
deposit consists of clays and bowlder beds similar to those of Death 
