JOHNSON: GRAND CANON DISTRICT. 139 
bends in the road the red beds are seen dipping steeply to the south- 
west where they are dragged up along a fault ))lane. Farther up, the 
grey crossbedded sandstone is similarly affected. The continuation of 
this fault toAvard the southeast is distinctly visible on the southeast 
wall of the valley, where the lava capping the crossbedded sandstone 
abuts against the sandstone at the contact, indicating a considerable 
displacement. It would appear that the general trend of the dis- 
placement where it crosses Oak Creek is northwest-southeast. 
From the first western bend in the road, above referred to, one has a 
splendid view of a prominent fault in one of the outlying mesas (pi. 17, 
fig. 2, F), where the lava-capped crossbedded sandstone on the eastern 
side of the displacement has dropped down 800 or 1,000 feet (esti- 
mated). This fault (which appears to be independent of the one just 
described) has a north-south trend and coincides with Oak Creek for 
an unknown distance northward, and may be called the Oak Creek 
Fault (fig. A, 0. C). The eastern side of Oak Creek is thus dis- 
tinctly lower than the western side. Near the outlying mesa, however, 
the creek swings to the east of the fault line, leaving a fragment of the 
downfaulted block west of the creek, and affording the precise contact 
visible in the end of the mesa. It is evident that the lava is older 
than the faulting, and from the character of the contact between the 
lava and underlying sandstone it appears that the lava was outpoured 
upon a surface at least somewhat diversified, with a valley several 
hundred feet deep near the present location of Oak Creek. 
The topographic features along this portion of the great escarpment 
terminating the Plateau Province show a fairly pronounced angularity, 
while segments of the escarpment and portions of the stream courses 
are relatively straight for considerable distances (see Verde sheet, 
U. S. topographic atlas). The location of Upper Oak Creek has 
evidently been determined by the Oak Creek Fault. In like manner. 
Bear Wallow Gulch a])]iears to have been erodetl along a fault line. 
There is thus a suggestion that faulting has exerted an important .con- 
trol over erosion in this region. More field work will be necessary 
before the evidence in favor of general fault-control can be regarded 
as conclusive. 
In the vicinity of Oak Creek the beds of the plateau series dip gently 
northward, thus ])reserving the general dip observed in other parts 
of the San Francisco Plateau. Farther north the dip has carried the 
crossbedded sandstone below the surface, and the overlying Aubrey 
