198 
SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA. 
^ 
formed, while the older lake beds are sandstones and well-rounded 
conglomerates which dip at high angles. Be- 
low Ash Meadows, in the Amargosa Desert, 
Campbell found evidence that the detrital 
deposits were laid down, after the folding and 
elevation of the lake beds into the Funeral 
Mountains. The time gap between the two is 
considerable, and the older beds are tentatively 
considered by Campbell /; Eocene and the others 
Pliocene. It is believed, however, from evi- 
dence obtained in the Amargosa Range, that 
the older beds are probably largely as Late as 
the Miocene and that they may be the shore 
deposits of Siebert Lake, while the presence of 
basalt, contemporaneous with the upper portion 
of the younger beds, indicates that their depo- 
sition probably extended into the Pleistocene. 
The later beds are evidently the equivalent of 
the older alluvium. 
Territory lah beds (including flu Siebert 
l<il>i beds). — The Tertiary lake beds, which are 
a northwesterly extension of the folded Ter- 
tiary sediments extending across the Funeral 
Mountains southwesl of Furnace Creek ranch, 
are confined, in the area surveyed, to the east 
side of Death Valley near the boundary. Nu- 
merous hills of these beds rise above the Recent 
gravels, and the scale of the map permits only 
an approximate representation of their com- 
plex distribution. 
The Tertiary lake bed- consist of white, 
yellow, and green consolidated clays, friable 
sandstones with ironstone concretions, rounded 
and subangular gravels, and thin lime-lone 
lenses. Much of the clay shows sun cracks 
and ripple marks, indicating that the lake was 
at times shallow and even (]ry. The subangular 
form of certain of the gravels indicates that 
cloudbursts at times spread sheets of detrital 
deposits over the lake beds. Colemanite and 
other chemical precipitates interbedded with the 
other deposits were laid down during periods 
of unusual evaporation. The more northerly 
hills to the west of the Daylight Spring-Furnace Creek road were 
Campbell, M. R., Bull. T". S. Geol. Survey X... 
Loc. cit. 
200, 1902, p. 1G. 
