146 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
retreat of the revived cliff from the fault line has sometimes given rise 
to the belief that the fault is of recent date, but it is evident that no 
such conclusion can hold. The revived cliff may be in the thrown- 
block, if the arrangement of the rocks favors such a result. A striking 
example of this kind may be seen in Tennessee (see Briceville, Tennes- 
see, topographic sheet, United States Geological Survey), where the front 
of the Cumberland plateau is cut across by a northwest-southeast fault, 
the northeastern block being relatively uplifted ; but to-day the surface 
is worn low on the weaker strata of the uplifted block, so that it is over- 
looked by the uplands of Carboniferous sandstones on the depressed 
block. 
If these considerations are accepted, there can be little doubt that the 
Sevier fault continnes in strong force beyond Pipe spring, as if to join 
the Toroweap fault, some thirty wiles further to the southwest. Some 
topographical expression of the fault ought to be found in the broad 
floor of Antelope valley, beyond the Shinarump cliffs of the Uinkaret 
plateau, where the weak Permian of the Uinkaret block lies opposite 
the resistant upper Aubrey of the Kanab block. It is perhaps in this 
way that one may explain a west-facing bluff which extends about ten 
miles south of Antelope valley (Dutton, c. Atlas, sheet XXII.), but 
further study on the ground is needed before this can be assured. It 
is interesting to note, however, that the wet-weather drainage here is 
from the weaker beds of the thrown block eastward through a gorge in 
the bluff that is determined by the more resistant beds of the heaved 
block ; a condition that is again entirely inconsistent with a recent 
movement on the fault plane. 
The Hurricane Fault is not definitely dated in Dutton’s report, but its 
southern part is thought to be of “ comparatively recent origin,” be- 
cause “ the amount of recession by erosion of the cliff of displacement is 
very small” (ce, pp. 116, 117). Its northern part near Virgin river 
must, however, be old enough to have allowed a strong recession of the 
Triassic escarpment since the faulting; for the two parts of the Trias 
east and west of the fault line are now fifteen miles apart (c, pp. 42, 
200); and as in the Sevier-Toroweap fault, the displacement of the 
cliffs is a measure not merely of their erosion since faulting, but of 
the excess of erosion in the heaved block over that in the thrown. The 
small amount of recession of the Hurricane ledge (Aubrey) from the 
fault line“in the southern part of the Uinkaret plateau, as stated in 
the last quotation from Dutton, may be explained not so much by the 
recent date of the fault, as by the recent date at which erosion had 
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