THE HEEAT UNCONFORMITY. 
179 
ter, and wherever the river has cut through them their edges form a vertical 
ledge at the summit of the inner gox’ge. In the middle, and indeed through 
the greater portion of the Kaibab division, they rest immediately upon the 
Archsean schists. Wherever the opening of the inner gorge is disclosed, this 
ledge is a very conspicuous feature. At the head of the Grand Canon it is 
also visible and as prominent as elsewhere, but this lower group here rests 
no longer upon the Archaean. An enormous mass of stratified rocks of older 
date has made its appearance, and the Archaean is far beneath them, and 
upon this older mass the lower Carboniferous quartzites are seen to 
repose unconformably. The dip of the Carboniferous system, which is still 
under the influence of the vanishing East Kaibab monocline, is about 5 or 6 
degrees to the eastward. The dip of the strata beneath, though not quite in 
the same direction, is nearly so, and the amount of it is upon an average 1 4 
to 15 degrees. As each stratum rises up to the plane of contact with the 
quartzites it is beveled off and disappears. Careful scrutiny discloses in the 
exposed edges an old fault, with a displacement of about 1,200 or 1,300 feet, 
cutting the lower strata, but not affecting the Carbonifei’ous above; and the 
beds upon the lifted side (the throw or drop of the fault is upon its western 
side) are planed off to a continuous up^^er surface. Farther down the river 
is also disclosed an abrupt anticlinal fold in the series, which is also planed 
off to a unifoi’m upper surface. For ten miles down stream this relation of 
the strata may be distinctly traced, showing a dip to the eastward which is 
visibly interrupted only by the fault and anticline just spoken of The view 
of it is at length lost behind the buttes. The “granite” is nowhere seen, but 
we know that it comes to the daylight only a mile or two beyond the point 
where the inner gorge winds out of sight. The thickness of this mass must 
be very great. As we follow down the river every mile of progress must 
bring up about a thousand feet of lower and lower beds, and the cumulative 
effects of this rise appear to be subject to subtraction only at the fault and 
anticline just spoken of. Altogether there must be at least 6,000 feet of 
them, and Professor Powell, who saw them in his descent of the river, esti- 
mates the total thickness at not far from 10,000 feet. Unless there are more 
faults or anticlines which cannot be seen from Cape Final, his estimate is 
apparently justified. 
