of the, C'uzco Valley, Peru. 



75 



by this easy disintegration has produced pinnacles and 

 columns and bizarre forms which have no counterpart in the 

 erosion remnants of other formations in the Cuzco region 

 (fig. 37). At all places visited the rock is traversed by joints 

 along many of which movement has taken place, as is indicated 



Fig. 37. 



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Fig. 37. Erosion column formed of Bambanusa sandstone. 



by slickensides and by numerous faults of a few inches dis- 

 placement. The rock does not, however, show the crushing and 

 shattering so common to the older sandstone of this district. 

 The material filling the joints, even where calcareous, is more 

 resistant to erosion than the rock itself, and the position of 

 joints and faults is indicated by ridges rather than by 

 depressions. 



