so 



II. E. Gregory— A Geologic Reconnaissance 



Feet. 



2. Limestone, white, massive; abundant shells; a calcare- 



ous, consolidated mud silt 5 



3. Shales or mud, white, yellow, black and brown ; thin- 



banded; calcareous, unconsolidated; becoming more 

 arenaceous and more carbonaceous in middle 4 



4. Limestone, like HSTo. 2 6 



5. Adobe like jSTo. 1, separated from No. 4 by an erosional 



unconformity 10 



Fig. 38. 





°iW&. 



Fig. 38. Section of San Sebastian formation near the mouth of Rio 

 Huancaro. 



6. Sand, gray to black, coarse, cross-bedded, thinly strati- 



fied, with bands of fine brown sand 2 



7. Sand and clay in alternating dark-red and gray regular 



beds, 1 inch to 1 foot in thickness ; sand fine with 

 few coarse beds ; clay and adobe increase in amount 

 toward top ; forms vertical banks of river 55 



87 



At the mouth of Rio Huilcarpay, 800 feet east of the locality 

 including the strata of Section X, the laminae of adobe uncon- 

 formable overlie and are interleaved with lenses of fine and 

 coarse cross-bedded black sands and gravels. Thin beds of 

 decomposed peat are also present. 



