44 
RECONNAISSANCE OF PART OF WESTERN ARIZONA. 
the other basins along the course of the river. The Chemehuevis 
gravel, which derives its name from this valley, occurs here in char- 
acteristic development, lying unconformably upon older and partly 
consolidated gravels. The older gravels are horizontally bedded 
in some places but in others are faulted and highly inclined. 
The relation of the Chemehuevis gravel to the older conglomerate 
was noted at several points along the river. In some places the older 
gravels are undisturbed beneath the Chemehuevis, the two being 
separated by an unconformity of erosion (section ^L,fig. 11). In other 
places the older gravels are upturned, eroded, and overlain by hori- 
zontally stratified Chemehuevis gravel (section B, fig. 11). In still 
Fig. 11. — Relations of gravel formations to each other and to igneous rock in the Chemehuevis Valley. 
A, The three gravel formations horizontally bedded hut separated by unconformities of erosion; B, 
the older conglomerate tilted, eroded, and overlain by horizontally bedded younger gravels; C, the 
older gravels tilted, intersected and overlain by lava, eroded, and again overlain by horizontally 
bedded younger gravels. 1, Flood-plain deposits; 2, Chemehuevis gravel; 3, Temple Bar (?) con- 
glomerate; 4, igneous rocks. 
other places the older gravels are tilted, intersected by lava, eroded, 
and overlain by the Chemehuevis gravel (section C, fig. 11). 
The older gravels apparently overlie rhyolite and andesite, and at 
one point a stratum of rhyolitic ash occurs within them. They vary 
greatly in character from place to place from sandy clay to a breccia 
with granite bowlders 4 feet in diameter. In general appearance 
they resemble the Temple Bar conglomerate, and are provisionally 
correlated with it. This conglomerate is apparently the one which 
Newberry a in the Ives report referred to the Tertiary. 
AUBREY CANYON. 
Near the southern end of the Chemehuevis Valley the granite 
of the bordering mountains approaches the river, and at the mouth 
of Williams River the Colorado enters a narrow canyon, the walls of 
a Newberry, J. S., Report upon the Colorado River of the West by Lieut. J . C. Ives, pt. 3, 1861, p. 29. 
