144 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
erosion since faulting are generally indicated by a break in the align- 
ment of the Triassic and Shinarump cliffs wherever the fault lines cross 
them. Powell (a, p. 191), Gilbert (a, p. 51) and Dutton (c, p. 200) 
all recognize the greater recession of the escarpments of the heaved side 
of the faults as a general occurrence, but they do not explicitly connect 
the amount of recession with the date of faulting. The dislocation of 
the cliff front is, as Gilbert phrases it, “not due to any horizontal 
ee 
th 
C 
’ 
4 
‘ 
. 
' 
. 
Figure 11. 
Sketch map of the Pipe spring district, showing the Sevier-Toroweap fault. _Weak lower 
Triassic strata, dotted; Triassic and Shinarump cliffs, hachured. Constructed from 
Dutton’s map and original field notes. 
displacement along the line of fault, but merely to the fact that the 
eastern portions, beittg lifted higher than the western, became subject 
to different conditions of denudation” (a, p. 51). Near Pipe spring, 
not only have the cliffs of the eastern (Kanab) block receded ten miles 
since the faulting occurred: but ten miles is the excess of the recession 
of the eastern cliffs over that of the western ; hence the chief movement 
of the fault here must certainly be of earlier date than the beginning of 
