of the Cuzco Valley, Peru. 65 



V. Section of Huayllabamba formation, Ccorao Pass 

 between Seqqueray and Catunga-Huayna. 



Strike N 80° W; dip 40° ± S. 



Feet. 



1. Sandstone, brown to gray, fine grained, even grained, 



massive; composed of quartz with small amounts of 

 feldspar and mica and specks of iron ore. Many 

 shale pellets near upper surface. Forms cliff 20 



2. Shale, dark red to chocolate; calcareous; sun-baked, 



includes beds and lenses of dark-red sandstone .... 30 



3. Sandstone, brown, in part gray, with thin beds of 



shale; mostly fine grained, but includes beds with 

 quartz grains the size of bird shot and pellets of 

 chocolate-brown clay, foliation surfaces mud cracked 65 



4. Sandstone, gray, fine grained, feldspathic 1 



5. Limestone, dark red, or highly calcareous sandstone, in 



beds about 2 inches thick, including shale layers ... 5 



6. Sandstone, brown, medium grain, even grained, slightly 



calcareous 6 



127 



The strata in Section V are disturbed by numerous faults 

 of small displacement. Green copper stain is common on 

 slickenside surfaces. The chocolate-colored shales, abundant 

 in Sections II and IV, are here relatively rare. 



The lofty mass of Seneca, overlooking the Cuzco Basin from 

 the northwest, consist essentially of strata of brown and gray 

 sandstone interspersed with beds of chocolate-colored shale. 

 Much of the sandstone is feldspathic and approaches arkose in 

 composition and texture; many beds include irregular layers 

 of conglomerate consisting of angular chunks of shale. The 

 strata, particularly at the base of Seneca, are intricately frac- 

 tured and where most disturbed are impregnated with malachite 

 accompanied with lesser amounts of azurite. 



In the bed of the Huatanay and along the Chunchullumayo, 

 thin strata of black limestone and of black shale were found, 

 and a measured section of the west bank of Rio Cachimayo, 

 2 miles above San Sebastian, includes 15 feet of black, slightly 

 carbonaceous shale, in the midst of which are two layers, each 

 half an inch thick, of nodular limestone. In other respects 

 the rock in Cachimayo Valley is typical for the Huayllabamba 

 formation. 



Am. Jour. Sci.— Fourth Series, Vol, XLI, No. 241.— January, 1916. 

 5 



