of the Cuzco Valley, Peru. 



29 



streams was thus interrupted and the initial major features of 

 the Cuzco Valley were developed. That the drainage system of 

 the Huatanay is not young is evidenced by the form of its valley, 

 and by several episodes in its history (described below), each 

 of which involves the lapse of long periods of time; that the 

 Cuzco Valley does not antedate the formation of the Inca 



Fig. 20. 



Fig. 20. Angostura Narrows showing truncation by recent, stream 

 cutting of mature slopes bordering the Huatanay. 



peneplain is shown by the remnants of ancient base-leveled 

 surfaces now subject to vigorous attack. The position of the 

 Huancaro fault with uplift on its western border points to a 

 crustal movement that may have determined the western limit 

 of the present Cuzco Valley; faults of the same or of later 

 date are believed to have outlined the course of the Huatanay. 



