of the Cuzco Valley, Peru. 63 



Feet. 



31. Shale, chocolate 2 



32. Sandstone, brown, thin-bedded, cross-bedded, ripple 



marked 11 



33. Shale, chocolate, with lens of sandstone; footprints( ?) 



on sun-dried surfaces 3 



34. Sandstones, alternating gray and brown; with lenses, 



stringers and nodules of calcareous chocolate shale 14 



35. Shale, chocolate 3 



36. Sandstone, brown, with lenses of shale at top 10 



37. Shale, chocolate 6 



38. Sandstone, brown, extremely thin-bedded 3 



39. Shales, chocolate 3 



40. Sandstone, gray, with bands and lenses of chocolate 



shale 12 



41. Shale, chocolate 2 



42. Sandstone, gray, fine grained; contains chunks of 



shale and a few well-worn quartz pebbles 28 



43. Shale, chocolate; upper surface highly uneven, chan- 



neled 2 



44. Sandstone, brown, with 4 to 6 inch bands of chocolate 



shale 40 



45. Sandstone, brown, and chocolate shale, in alternating 



beds 1 to 8 feet thick, with features essentially like 

 Nos. 30-45 inclusive 300 



703 



Two hundred feet of rocks, exposed in scattered outcrops and 

 stratigraphically above the beds included in Section III, differ 

 from the measured strata only in having a somewhat more 

 regular lamination and a slightly greater calcareous content. 

 Two thin layers or lenses of black argillaceous limestone were 

 noted. All the beds are thin, individual layers rarely exceed- 

 ing 5 feet. The transition from shale upward into sandstone 

 is in most places accomplished by means of a sandy zone made 

 conglomeratic by the presence of fragments of the underlying 

 shale. The shales themselves usually consist of alternating 

 arenaceous and argillaceous layers one-sixteenth to 1 inch thick. 

 Many of the arenaceous shale laminse present smooth, glisten- 

 ing, sun-baked surfaces specked with mica, dotted with mud 

 lumps, crossed by polygonal cracks. Features interpreted as 

 worm trails and borings and impressions of plant fibers were 

 noted at a few places. The beds are traversed by closely spaced 

 joints which furnish the talus slopes with rhombohedral blocks 

 a few inches in long diameter. 



