60 C. D. WALCOTT — A DISPLACEMENT IN" THE GRAND CANON. 



movement produced the upward Hexing of the strata, as is shown in 

 meet of the cross-sections of the fault, as well as by the alteration of the 

 Red Wall limestone. The latter formation received its flexure and local 

 metamorphism in passing by the rocks of the same geologic ago ami 

 also the Upper Tonto Btrata beneath, on the opposite or west Bide of the 

 fault Then- is m> direct evidence that the Aubrey limestone was also flexed 

 and metamorphosed, as ii is now removed by erosion from the vicinity of the 

 fault, but from the relations it bears to the strata below, as shown in sections 

 •1. 5 and 6, and in fig. 1 1 , there is little doubt that such was the case. This is 

 almoel absolutely proven by its partaking ol* the flexure of the fold, to the 

 north, in perfect conformity to the strata beneath. 



Prom these considerations and the present relationsof the strata on the 

 opposite Bide of the fault, as given in rig. 11, it is evident that tin 1 formations 

 (Upper A.ubrey, Lower A.ubrey, Red Wall, Upper Tonto, and Tonto sand- 

 stone) had not been eroded, within the dotted lino, at the time of faulting. 



< )n the slope of the East Kaibab ibid, twenty miles to the north, the hard, 

 compact limestones of the summit of the Aubrey group form the surface 

 rock. The massive layers curve downward with the flexure of the fold, and 

 often large slabs, detached by erosion, retain the curvature they received. 

 When this Hexing occurred there must have been a considerable thickness of 

 Btrata above, exerting by its weight a powerful downward pressure. This 

 necessitates the presence of the Permian and more or less of the superjacent 

 strata over the east -lope of the Kaibab Plateau and the Grand ('anon 

 ana. Whatever other < litions of slow movement and lateral pressure 



may have existed, a downward preS8Ure, as above indicated, was also 

 necessary in order to fold and flex the strata as they occur on the lii f 



the Easl Kaibab displacement, both in the fold and on the line of the Butte 

 fault. 



The Hull' Fault >ni<l the Grand ('anon. — It is stated in the preceding 

 paragraph that in order to explain the curvature of the strata near the fault 

 a considerable thickness of strata must have existed above the rocks now 

 exposed to view. With a thousand feet or more of strata above the area 

 now occupied by the Kaibab and the lower plateaus adjacent to the Grand 

 Canon, ii is difficult to understand how the canon could bave existed even 

 to a limited .hpth. in it- present position, al the time of the elevation of the 

 Kaibab Plateau. An explanation more in accord with observations on the 

 I tern Kaibab displacement is that while the uplifting of the plateau and 

 the Easl Kaibab displacement were progressing, the Colorado river w 

 cutting its channel down through the Mesozoic groups that then rested on 

 the Paleozoic rocks in which the presenl ••anon is eroded, and that, instead 

 of cutting a channel down through the limestones and sandstones of the 

 Paleozoic, u the plateau was elevated, it was cutting through the fold in the 



