62 



E. HUNTINGTON- J. IV. GOLDTHU'AIT 



date. At Coal Spring, where the basalt flowed west across the 

 old fault line onto the Verkin, the weak shales were locally pro- 

 tected, so that the modern cliff front at this point is west of the 

 old Hurricane fault line. Of this i,8oo-foot escarpment all but 

 a few hundred feet is the product of erosion on the line of the 

 old fault during the canyon cycle. There could be no better 

 illustration of the progress of erosion since the later faulting than 

 this, which shows that the existing cliff has been shaped almost 



Fig. 10. — Sugarloaf mesa, on the edge of the Hurricane escarpment, west of 

 Gould's ranch. A small basaltic cap protects a few hundred feet of Verkin shales, 

 which recent erosion has elsewhere stripped off to the level of the Aubrey platform 

 seen in the foreground. 



wholly by erosion, working under the conditions imposed by the 

 old fault, the erosion interval, the basalt flows, and the recent 

 uplift. 



SUMMARY. 



The post-Eocene history of the Toquerville district has been 

 characterized by two periods of upheaval, separated and followed 

 by periods of relative quiet. In the first period, which was 

 doubtless of great duration, with an unknown amount of erosion, 

 occurred the original folding, the eruption of andesite upon a 

 surface, but slightly, if at all, dissected, the reversal of the direc- 

 tion of deformation, and the earlier faulting. In the Kanarra 



