148 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
valley it happened to be located. The feature might also be explained 
a.s the result of an older and a later uplift along the fault line. 
Sevier Fault. 
In common with the other displacements which traverse the Grand 
Canon district, the Sevier Fault (fig. A, .S'.) was regarded by Dutton 
as of recent age. He described this fault as terminating a few miles 
southwest of Pipe Spring, where the principal topographic evidence of 
the fault does vanish (Dutton, '82, p. 20-21). It was a part of Button's 
theory that the faulting was so very recent that erosion had not yet 
been able materially to affect the fault cliffs. He writes: "It may be 
remarked here that every fault in the district is accompanied with a 
corresponding break in the topography. I do not recall an instance 
where the lifted beds are planed off by erosion, so as to make a con- 
tinuous level with the thrown beds" (Dutton, '82, p. 130). Yet he 
recognizes the greater retreat of the plateau terraces on the up-thrown 
side of the faults as one result of the faulting. Thus, he states that 
the faults occurred so long ago that the Vermilion and Shinarump Cliffs 
have been worn back from ten to twenty-five miles on the u]>thrown 
side, in excess of the amount of wearing back on the down-thrown 
side, since the time of the faulting (Dutton, '82, p. 200); also that the 
faults occurred so recently that the fault cliffs have been worn back 
but little (Dutton, '82, pp. 94, 117, 130). Such a discrepancy in the 
amount of erosion suffered by the two ty])es of cliffs })oints strongly to 
some other interpretation than that given by Dutton. 
It has already been shown that the retreat of the Vermilion and 
Shinarump Cliff's in the Pi])e Spring district affords evidence of an 
ancient date for the Sevier Fault (Davis, '01, p. 143-145; '03, p. 12-15). 
It has likewise been shown by the same writer that the drainage in that 
district is from the down-thrown side of the fault toward the up-thrown, 
and that cliff's of the down-thrown rocks overlook lower areas eroded 
on the up-thrown rocks (Davis, '01, p. 145-140; '03, p. 15-10). A 
com])lete reversal of the to])ographic eff'ects of faulting is thus shown, 
])ointing to an ancient date for the fault, and at least one ])eriod of 
extensive baseleveling between tlie faulting and the present time. The 
following paragraplis present similar evidence observed farther south- 
west, and add another argument for the ancient date of the Sevier 
Fault. 
