of the Cuzco Valley, Peru. 



Feet. 



7. Silt, earthy, calcareous, compact, banded with, white 



layers representing old soils ; few shells 7 



Unconformity. 



8. Sand and coarse gravel composed of angular fragments 



of sandstone 4 



44 



In quebradas immediately north of the village of San Sebas- 

 tian over 200 feet of sediments assigned to the San Sebastian 

 formation are exposed. At their contact with the Yucay lime- 

 stone the beds are nearly horizontal; farther southwest they 

 slope toward the Huatanay with a dip gradually increasing 

 to 15° (fig. 31). In this locality the lacustrine beds are 

 chiefly sand (fig. 40) ; limestone and adobe being compara- 

 tively small in amount, as shown in the following partial 

 section : 



XIII. Section of San Sebastian formation in wall of 

 unnamed quebrada 1 mile north of San Sebastian Cathedral. 



Strike N; dip 6° W. 



Feet. 



1. Limestone forming surface slope; thin-bedded, soft, 



porous, chalky ; contains shells 12 



2. Sand, hard-packed; alternating fine and coarse ; lentic- 



ular, cross-bedded 30 



3. Limestone, thin-bedded, impure 5 



4. Adobe with abundant plant impressions 2 



5. Sand 16 



6. Adobe 3 



7. Sand like No. 2 60 



8. Sand, fine, and adobe with 3-inch band of white lime- 



stone 16 



9. Gravel, with pebbles as much as 2 inches in diameter 1 



10. Gravel, fine, and coarse sand, dark gray, with thin beds 



of fine light-red sand; cross-bedded and intricately 

 faulted along planes showing displacement of indivi- 

 dual blocks of one half inch to 8 inches 25 



11. Sand, even grained, fine, cross-bedded; faulted 20 



12. Limestone, white 3 



13. Sand 2 



95 



In the sediments at San Sebastian the calcareous beds are 

 highly variable in thickness and extent; in certain places 

 examined only one thin bed of limestone was found in 100 feet 



