DAVIS: THE GRAND CANYON OF THE COLORADO. 165 
was, as has been stated, near the centre of greatest local upheaval (the 
Kaibab) where the revelation of weak underlying strata had reduced the 
level of the Trias by sapping, and had thus produced an amphitheatre, 
open on the southwest. At the same time, the subsequents under the 
Triassic escarpment were gathered into a single stream to form the 
Little Colorado, discharging northward ; but this result may have been 
in part the effect of spontaneous interaction among the streams them- 
selves, after their habit in such cases, and only in part the effect of 
upheaval at the time of faulting. Once reaching the Kaibab amphi- 
theatre, the new-born river followed southward along the subsequent 
Permian valley which must have been opened along the east Kaibab 
flexure, until the slopes of the northeast-dipping flexure that limits the 
— —— 
Figure 13. 
The eastern lobe of the Coconino plateau, as seen from near Lockett’s tank. The fore- 
ground shows a ravine in the upper Aubrey limestone, once filled with lava, and now 
partly re-excavated. The ‘‘tank” is a waterfall pool. Drawn from rough sketch. 
Coconino plateau were encountered. The river then turned northwest- 
ward along a trough of weak and low-lying Permian strata that occu- 
pied a depression between the two uplifts; and it is notable that 
the small but sharp flexure which bounded this trough on the south 
may now be traced through the spurs of Carboniferous strata on the 
southern canyon wall (Dutton, c, p. 185). The flexure comes from the 
southeast, where it forms the northern border of the eastern lobe of 
the Coconino plateau ; it trends northwest, as if to join the now-faulted 
flexure at the western base of the Kaibab. We had a good view of it 
from the southern rim and from the bottom of a side canyon. Thus 
interpreted, it appears that a part of the true Kaibab uplift lies south 
of the canyon, where it slopes into what is locally known as “the 
