of the Cuzco Valley, Peru. 55 



Qquilqtte Fokmatton. 



As displayed in the field the strata included in the Qquilqne 

 formation are bounded on the east and north by the Huancaro 

 fault; in other directions the formation extends beyond the 

 limits of the area mapped. Although showing numerous small 

 folds with variously oriented axes the beds in general form an 

 anticline trending approximately north. The dips on the east 

 limb of the major fold reach angles exceeding 80° ; high dips 

 prevail also on the west limb but decrease in amount with 

 increase of distance from the central axis. Alternating beds 

 of brown sandstone and chocolate-colored shale are exposed on 

 the two limbs ; the truncated crest includes beds of limestone 

 conglomerate and of gypsum. Unequal resistance of the vari- 

 ous strata has determined the lines of major drainage; the 

 broad upper valley of the Qquilque in particular appears to 

 owe its position and form to the weathering of soluble beds. 

 The character and arrangement of strata in the upper portion 

 of the Qquilque formation is shown in the following section 

 of the east limb of the anticline. 



I. Section of upper beds of the Qquilque formation in 

 an area of intricately folded strata along the Ferrobamba trail, 

 beginning three-quarters of a mile from the mouth of Qquilque 

 Quebrada. 



Average strike approximately north; dip 30° E-90°. 



Top. Feet. 



1. Sandstone, brown, fine to medium grained; quartz 

 grains with calcareous and argillaceous cement ; beds 

 4 to 5 feet thick, subdivided by fine lines or stripes 

 of darker material; lenses and pellets of clay com- 

 mon ; much secondary lime along joints 80 



2. Shale and argillaceous sandstone; red to chocolate; 



calcareous in places; highly variable in texture, 

 composition, and structure 8 



3. Sandstone, brown, calcareous, lenticular and nodular 1 



4. Shale and argillaceous sandstone, like No. 2 ; in places 



recemented bits of fine sandstone 4 



5. Sandstone, brown, calcareous, fine grained; minutely 



striped and cross-bedded; beds displaced 3 feet by 



a fault trending, about east 1 



6. Shales, light red to chocolate; calcareous; irregularly 



bedded; resemble compact weathered sandy clay, 

 rearranged by pressure 10 



7. Sandstone, brown, like No. 1 4 



