JOHNSON: GRAND CANON DISTRICT. 151 
A dam built across the entrance to the gorge serves to retain a j^art of 
the small amount of water which falls in this desert region, forming a 
pool at which cattle and horses may drink. In common with the 
reversal of the to])ographic effect of faulting at the knoll, the absence 
of cliffs farther northeast, and the drainage relations may be best 
explained on the basis of an ancient date for the faulting. 
As stated in a preceding paragraph, successively lower beds rise in 
the face of the cliff as the latter is traced toward the southwest. This 
feature becomes especially noticeable when the upper Carboniferous 
limestones appear. Bed after bed of this series rises from beneath the 
general level of the Uinkaret Plateau, to take its part in forming the 
west-facing escarpment. Yet the escarpment does not show a corre- 
sponding increase in height. On the contrary, the beds are bevelled 
across at a fairly uniform elevation, so that the outcrops of the suc- 
cessive layers swing away from the summit of the scarp, toward the 
east, as shown in the map (fig. C). Such relations indicate that there 
has been an uplift accompanied by warping along the east side of the 
fault, with subsequent baselevelling to reduce the uplifted beds to a 
fairly uniform surface. The softer beds (upper Carboniferous and 
lower Permian shales) which the faulting left opposite the limestones 
on the Avestern side of the fault, have been more or less removed by 
erosion, so that the surface on the west is now lower, consisting of the 
Carboniferous limestone series with considerable remnants of the 
overlying shales. There would seem to be no doubt that we have 
here to deal with a cliff developed along an ancient fault after a period 
of more or less extensive baselevelling had once destroyed the original 
topographic effect of faulting. It has been suggested that such cliffs 
may be called "fault-line cliffs," to distinguish them from true fault 
cliffs resulting directly from displacement. 
ToROWEAP Fault. 
According to Dutton the Sevier and Toroweap Faults are independ- 
ent, the first having its southern end near Pipe Spring (fig. A, P. S.), 
the latter its northern end twenty miles north of the Grand Caiion. 
The faults are therefore represented as distinct on the maps accompany- 
ing Button's monograph. 
Davis recognized that the Sevier Fault continued farther southwest 
