California Tertiary Formations.—Hershey. 303 
northeast-southwest and is open to Antelope valley on the 
northeast, but is drained to the south by Piru creek through 
a deep gorge. The main basin is about 12 miles long by 7 
miles in greatest width. An arm extends into the depression 
between Alamo and Fraser mountains. Another narrow arm 
extends along the very deep, narrow depression between 
Fraser mountain and the San Emedio-Tehachapai range. Still 
another arm extends northeast into Antelope valley where 
the same series is probably developed along the northern flank 
of the Sierra de la Liebre. 
This basin is occupied mainly by soft, heavy-bedded 
sandstone. On the north border, along the foot of the granite 
range, there is a narrow belt.of lava, rhyolitic in part, which 
has been faulted down into the granite anda remnants pre- 
served from erosion. Seemingly a detrital slope of granitic 
debris from the Tehachapai range, was built up over the nar- 
row strip of lava. Near the outer border and toward the top 
this detrital slope material is stratified, showing apparently 
the action of static water. On the west, where the Pliocene 
extends into a sort of cove in the schist-gneiss-granite moun- 
tains, a depression separating Fraser and Alamo mountains, 
the lower division is a buff bed of waterworn and water-de- 
posited material from the headwaters of Piru creek, and re- 
sembles the lower or Lang division of the Upper Pliocene 
in the valley of the Santa Clara river. On the southeast of 
the basin where the mountains are low and of Cretaceous 
strata, the lower division is thin and indefinite. In short, the 
lower division displays the influence of local conditions sur- 
rounding the basin, and the beginning of static-water con- 
aitions. 
The middle division and bulk of the series is an alterna- 
tion of heavy beds of light pink coarse sandstones, (with an 
occasional granite pebble,) and finer and more argillaceous 
sandstone of a light olive color. The first may have derived 
its peculiar pink color from the pink feldspar of the granite 
of the Tehachapai range, and the latter its light olive color 
and clayey constituent from the dark olive Cretaceous shales 
on the southeast. This division is sharply and regularly strat- 
ified, not of the alluvial or beach types, and seemingly corres- 
ponds in taxonomic position with the middle or Soledad 
member of the Upper Pliocene in the Santa Clara basin. 
