PHYSIOGRAPHIC AND GEOLOGIC DEVELOPMENT 257 



series of sedimentary rock lias suffered but slight deformation. 

 A still more highly deformed basal series occurs on the right of 

 the section, presumably the older quartzites. At Huancarqui, op- 

 posite Aplao, an extensive view was gained of the western side 



Fig. 175 — Sketch section to show the structural details of the strata on the south 

 wall of the Majes Valley near Cantas. The section is two miles long. 



of the valley, but the lower Tertiary seems not to be represented 

 here, as the upper undeformed series rests unconformably upon 

 a tilted series of quartzites and slates. Farther up the Cantas 

 valley (an hour's ride above Aplao) the Tertiary rests upon vol- 

 canic flows or older quartzites or the granite-gneiss exposed here 

 and there along the valley floor. 



In no part of the sedimentaries in the Majes Valley were fos- 

 sils found, save in the now uplifted and dissected sands that over- 

 lie the upraised terraces along the coast immediately south of 



Fig. 176 — Composite geologic section to show the structural relations of the 

 rocks on the western border of the Maritime Cordillera. The inclined strata at the 

 right bottom represent older rocks; in places igneous, in other places sedimentary. 



Camana and also back of Mollendo. Like similar coastal deposits 

 elsewhere along the Peruvian littoral, the terrace sands are of 

 Pliocene or early Pleistocene age. The age of the deposits back 

 of the Coast Range is clearly greater than that of the coastal de- 

 posits, (1) since they involve two unconformities, a mile or more 

 of sediments, and now stand at least a thousand feet above the 

 highest Pliocene (or Pleistocene) in the Camana Valley, and (2) 

 because the erosion history of the interior sediments may be cor- 

 related with the physiographic history of the coastal terraces and 

 the correlation shows that uplift and dissection of the terraces 

 and of the interior deposits went hand in hand, and that the de- 



