of the Guzco Valley, Peru. 79 



Strata horizontal. 



Feet. 



1. Adobe and fine sand forming present surface 3 



2. Sand, white, calcareous 1 



3. Adobe, yellowish t . . . . 2 



4. Limestone, white, compact, massive in places, elsewhere 



very thinly laminated; abundant shells of Physa, 

 Sphserium, and Planorbis ; roots represented by rusty 

 tubes ; quarried for lime 6 



5. Adobe with lenses of white lime; several overlapping 



lenses of gravel, pebbles as much as one half inch in 

 diameter of quartz, sandstone, and aggregates of black 

 sand 9 



6. Sand and adobe like No. 12 2 



7. Limestone, white, fossiliferous 0.5 



8. Adobe and sand like No. 12 10 



9. Limestone, white, with carbonized material in 1-inch 



bands, lens-shaped ; capped by yellow weathered zone 1 



10. Adobe, light red, in very thin beds ; exceedingly irreg- 



ular and wavy in deposition and containing lenses 

 3 to 5 feet thick of fine sand and fine gravel with 

 pebbles of quartz and lime concretions as large as 

 buckshot, all very well worn; contains also minute 

 streaks of white lime and of carbonized materials . . 5 



11. Shale-like materials, black, in bands 2± inches thick, 



consisting of (1) white weathered adobe at base; (2) 

 gray shale with abundant impressions of grass, stems, 

 roots, etc., and rare shells; and (3) thin beds of 

 black peat. These beds are continuous, but portions 

 of 1, 2, and 3 interleave at distances of 20 to 100 

 feet 3 



12. Adobe consisting of fine sand with clay; highly cal- 



careous ; lime in minute specks and streaks ; rare 

 coarser-grained material of same composition in 

 lenses 18 



61.5 



This section is shown in fig. 38. 



X. Section of San Sebastian formation on bank of Rio 

 Huatanay, half a mile south of San Sebastian. 



Beds horizontal. 



Feet. 

 1. Adobe, massive, brown, firmly cemented; traversed by 

 vertical root tubes ; contains scattering grains of sand 

 the size of buckshot in lower part. Toward top 

 color gradually changes to yellow-gray 5 



