62 C. D. WALCOTT — A DISPLACEMENT IX Till: GRAND CANON. 



superjacent Mesozoic rocks. Thia would influence the manner of the erosion 

 of tin- Grand Cafion, ami, if followed nut in all it- bearings, would probably 

 necessitate Bome change in the now accepted views concerning the manner of 

 the erosion of the broad outer ami narrow inner cafions, wesl of tin- BLaibab 

 division of the Grand Canon. At present tin- influence of the Butte fault 

 on the erosion of the area immediately adjacent to it will alone be noticed. 



Fig. 11 shows thai as so in as the river reached the limestone on the west 

 of the fault, it would necessarily erode the softer strata on the east Bide until 

 the BUmmit of the Upper Aubrey limestone «;i> reached. If mar <»r on the 

 line of the fault, the channel would be deflected eastward by the slope of the 

 ita until it reached the base of the slope, leaving a strip of rock between 

 the river channel and the fault line. The cliff left on the west Bide of the 

 fault as the river deepened its channel, afforded the agencies of aerial erosion 

 an opportunity to do their work rapidly, and the debris was carried to the 

 river as soon as it fell on the limestone slope below. With the deepening of 

 the river bed, channels formed between it and the retreating cliff, and the 

 great buttes were marked off Subsequent erosion deepened the channels to 

 cafions and removed the strata on the west of the fault. When the base 

 line of erosion once reached the friable and easily eroded argillaceous Btrata 

 of the Ghuar group, the cutting away of the inner canon valley area advance d 

 at a rapid rate, until the havoc and ruin was greater than that accomplished 

 by the direct agency of the river in the cafion east of the buttes. To-day 

 the buttes rise high above the inner cafion valleys and guard them from the 

 ravages of the river, although they are 2,000 feet below the level of the 

 Kaibab plateau. 



Analogy between tl"- Hurricane Fault and ili> Butte Fault. The Butte 

 fault i- only paralleled in the Plateau country, as far as known to me, by a 

 portion of the great Hurricane fault, north <»f the town of Toquerville, in 

 southern Utah. The upturning of the strata is there on a somewhat greater 

 Male, and it occurred in the earlier movement on the line of the fault, for 

 the upward flexing is from the east and the present downthrow is to the west. 



The downthrow of the Hurricane fault north of Toquerville is estimated 

 by Captain Dutton to l>c over 6,000 6 i The massive Aubrey limestone 



rises towards the fault from the east at an angle of from 25° to 30°, the 

 western face of the flexed Btrata forming a more or less broken cliff 1,000 

 feel in Keight. To the north the shear of the fault increases rapidly. Ten 

 miles distant it is estimated by Dutton at from 12,000 t<» 14,000 feet. 

 Tin- upturning of the Btrata from the east is also more marked north of 

 Canarra, where it curve- up to the vertical and is even reversed bo as to 

 have a westward dip of 1 •» for a distant f several miles along the fault. 



Captain DuttOD -tale- that the thrown he. Is, on the west Bide of the fault, 



curve down towards it. He explains this by the presence of a monoclinal 



•miv History ..t ti,.- Qr»od Cafion m-tn 



