HURRICANE FA ULT IN SOUTHWESTERN UTAH 5 5 



during the interval there was time for the erosion of the surface 

 nearly to baselevel. 



b) The lava-covered stirfaces 07i the Shiv wits plateau. — West of 

 the Hurricane, on the Shivwits plateau, lava is seen lying on a 

 level surface of soft Verkin shales — rocks so easih^ eroded that 

 they can assume a level 

 surface only when close 

 to baselevel. The wide 

 distribution of these lava- 

 covered surfaces points 

 to an approach to pene- 



plaination over a con- 



. , , 1 ■ ,1 Fig. 5. — The Hurricane Fault at Coal 



siderable area m the ,, . ... 



bpnng, looking north. 



southwest. 



c) The old fault, the old lowland surface, and the new fatdt. — -At 

 several points between Fort Pierce and Kanarra, where the Hur- 

 ricane fault-line is crossed by basalt flows, a displacement of two 

 different dates is clearly shown, and it is seen that at the end of 

 the interval between the two the relief of the region was much less 

 than now. Where the first faulting had brought resistant strata, 

 such as the Aubrey limestone or Upper Kanab sandstone, into 

 .contact with softer strata, such as the Verkin shales, the harder 

 strata rose in a low escarpment, whether they lay on the heaved 

 or thrown side of the fault. Against this the lava flowed, and 

 thus was checked soon after crossing the line of displacement, 

 while in other places, where the strata on the two sides of the 

 fault were of nearly equal resistance, the lava flowed across the 

 faults to a much greater distance. In still other cases the strata 

 underlying the basalt are more or less tilted, but nevertheless they 

 were reduced by erosion to a level surface that bevels the edges 

 of the layers. Sometimes these are shales, such as those at 

 Gould's Ranch, which under present conditions of active erosion 

 rarely form a level surface; for they are so soft that when the 

 overlying cap of hard strata is removed, they are at once minutely 

 dissected into a rough bad-land topography and are soon wholly 

 swept away, in so far as they He above grade. In other places, 

 as near Bellevue, five miles north of Toquerville, highly inclined 



