20 RECONNAISSANCE OF PAKT OF WESTERN ARIZONA. 
Mountain to Trout Creek, and are best observed in Truxton Canyon, 
through which the Santa Fe Railway descends from the high plateau 
to the lowlands farther west. The Aquarius Cliffs extend from 
Trout Creek southward to the Aquarius Mountains. 
Topographic features. — The Cottonwood and the Aquarius cliffs 
are lower and less precipitous than the Grand Wash Cliffs. Alluvial 
cones and slopes are developed to some extent at the base of the 
Cottonwood Cliffs north of Truxton Canyon, but from that canyon 
southward to Signal the Big Sandy flows close to the cliffs and 
prevents the formation of cones. 
The continuity of the escarpment formed by these cliffs is inter- 
rupted in several places by canyons, chief among which are Truxton, 
White Cliff, Trout, and Sycamore creeks. The canyons are narrow 
and steep and the streams torrential in character. 
Rock masses. — The Cottonwood Cliffs are composed principally of 
granite, 2,500 feet of which is exposed near Hackberry. The granite 
is covered by a comparatively thin sheet of andesite which forms the 
cap rock of the cliffs and thickens southward, connecting with' the 
great masses of igneous rock in the Aquarius Mountains. 
Vz 
Fig. 1.— Sketch section across White Cliff Canyon, showing relation of the andesite of the Truxton 
Plateau to the younger basalt at the foot of the cliff. 1, Andesite flow; 2, granite; 3, andesite tuff; 
4, basalt flow; 5, stratified volcanic ash. 
In White Cliff Canyon the plateau is covered by andesite 200 feet 
thick, the lower half consisting of tuff and the upper half of a columnar 
flow. Near the mouth of the canyon a younger mass of volcanic 
rock occurs in an erosion embayment about 1,200 feet lower than 
the lava capping the cliffs. The younger mass is basalt and consists 
of several layers of ash, tuff, and flow. (See fig. 1.) 
YAMPAI CLIFFS. 
Location. — A series of irregular cliffs extends from Music Mountain 
in a general southeasterly direction to the southern end of the Juniper 
Mountains, where they turn northward, forming the western bluffs 
of the Chino Valley, which lies directly east of the area here described. 
These are locally known as the Yampai Cliffs. 
Topographic features. — The Yampai Cliffs resemble the Grand Wash 
Cliffs in being precipitous and composed of hard limestone strata, 
but differ from them in being much more irregular in outline. They 
vary in altitude from about 6,000 to 6,700 feet and rise 1,000 or 
more feet above the Truxton Plateau. In their sinuous outlines, 
large reentrant angles, and detached outlying portions Yampai 
