16 BORAX OF DEATH VALLEY AND MOHAVE DESERT, [bull. 200. 
PAHRUMP VALLEY TO OWENS LAKE. 
Amargosa Valley near Ash Meadows. — Near the California-Nevada 
State line Amargosa Valley was occupied by another lake, the sedi- 
ments of which are to be seen on the road from Pahrump Valley to 
Furnace Creek in Death Valley. 
The beds are similar in composition to those about Resting Spring, 
but the stream has not succeeded in cutting awa}^ the barrier that 
ponded the water, and the beds are only slightly dissected. The bar- 
rier at the lower end of the lake was presumably only a few miles 
south of the road, but to the north the water may have extended far 
into Amargosa Desert. 
The easternmost exposure of these beds is at an altitude (barome- 
ter) of about 2,200 feet. From this they descend westward to about 
1,850 feet at Amargosa River. This inclination is about the same as 
that which marks the beds near Resting Spring; hence the move- 
ment that produced it was probably common to the region east of 
Death Valley. These beds are not visible west of Amargosa River, 
but it is altogether probable that they rest against the foothills of 
Funeral Mountain. Since in this locality the mountain is composed 
of folded Tertiary rocks striking northwest and southeast;, it is appar- 
ent that the two series are of different ages, and that the lakes which 
occupied Amargosa Valley came into existence after the disappearance 
of the lake in the north end of Death Valley and after the folding 
and elevation of its sediments into Funeral Mountain. This coincides 
with the statements heretofore made that lake-forming conditions 
appear to have prevailed at least during two distinct periods, the first 
of which may have been in the Eocene period and the last in Pliocene 
time. 
furnace Creek in Death Valley. — By far the greatest exposure of 
lake beds, and also the largest deposits of borax that are known, occur 
in Funeral Mountain, or, as they are more generall}- described, on 
Furnace Creek in Death Valley. These sediments lie diagonally across 
Funeral Mountain, in a belt whose reported width is 12 or 15 miles. 
On the north they are limited by an abrupt mountain wall of Paleozoic 
limestones, shales, and quartzites, which stand from 3,000 to 4,000 feet 
above the general level of the Tertiary hills on the south. The Pale- 
ozoic strata comprising this mountain front strike at right angles to 
the direction of the mountain face, and dip generally to the southeast 
from 30° to 60°. So far as could be determined without climbing, 
this escarpment extends in a straight line across the mountain, and it 
coincides in direction and presumably is continuous with the foot of 
the mountain which bounds Death and Mesquite valleys on the north- 
east. It undoubtedly marks the position of one of the great faults of 
the region, which extends parallel with the great structural features 
of central California. 
