256 THE ANDES OF SOUTHERN PERU 



in lithographical character may be noted between these and the 

 beds of the preceding section. 



Again just above Cantas on the east side of the valley is a 

 clean section exposing about two thousand feet of strata in a half 

 mile of distance. The foundation rocks are old quartzites and 

 shales in regularly alternating beds. Upon their uneven upper 

 surfaces are several thousand feet of red sandstones and conglom- 

 erates, which are both folded and faulted with the underlying 

 quartzites. Above the red sandstones is a thick series of gray 

 sandstones and silts which makes the top of the section and uncon- 

 formably overlies the earlier series. 



A similar succession of strata was observed at Aplao, still 

 farther up the Majes Valley, Fig. 174. A greatly deformed and 

 metamorphosed older series is unconformably overlaid by a great 



Fig. 174 — The structural relations of the strata on the border of the Majes Valley 

 at Aplao, looking west. Field sketch from opposite side of valley. Height of section 

 about 3,000 feet; length about ten miles. 



thickness of younger strata. The younger strata may be again 

 divided into two series, a lower series consisting chiefly of red 

 sandstones and an upper consisting of gray to yellow, and only 

 locally red sands of finer texture and more uniform composition. 

 The two are separated by an erosion surface and only the upper 

 series is tilted regionally seaward with faint local deformation; 

 the lower series is both folded and faulted with overthrusts ag- 

 gregating several thousand feet of vertical and a half mile of 

 horizontal displacement. 



The above sections all lie on the eastern side of the Majes Val- 

 ley. From the upper edge of the valley extensive views were 

 gained of the strata on the opposite side, and two sections, though 

 they were not examined at close range, are at least worth com- 

 paring with those already given. From the narrows below Can- 

 tas the structure appears as in Figs. 175-176, and shows a deform- 

 ing movement succeeded by erosion in a lower series. The upper 



