78 IOWA ACADEMY OF SCIENCE 



relations, and that all the associated strata must be taken into 

 consideration in the identification of any horizon. Nearly all 

 the available limestone on Tarkio creek is exhausted ; no quarry- 

 ing has been done lately, and in recent years no outcrop where 

 a satisfactory section could be obtained was known. At Snow 

 Hill, one mile north of Coin, recent erosion has exposed the fol- 

 lowing section. It is given as it is the only good outcrop at 

 present on Tarkio creek. 



SECTION ON TARKIO CREEK ONE MILE NORTH OP COIN. 



FEET. 



9. Shale, yellow passing down into blue 9 



8. Limestone, gray weathered yellow, Fusulina.... 1 



7. Shale, gray, calcareous 3 



6. Limestone, blue, weathered brown 2 



5. Sandstone, brown, friable 1 



4. Shale, gray, weathered 6 



3. Limestone, gray 1 



2. Shale, red 3 



1. Shale, gray, weathered 2 



Total 28 



The upper eight inches of number six usually parts from the 

 rest of the ledge, and in some localities this parting becomes a 

 shale two feet thick. 



About two hundred yards east of this outcrop near the Chi- 

 cago, Burlington and Quincy railroad a core drill hole gives 

 the following record of the City Bluffs shale. The drilling com- 

 mences immediately beneath the Tarkio limestones exposed in out- 

 crop at the old mill site. 



SECTION OF CORE DRILLING ON RAILROAD NORTHEAST OF 



COIN. 



FEET INCHES 



21. Light shale 16 8 



20. Gray shale 11 4 



19. Gray limestone, impure, shaly 9 G 



18. Gray shale 32 2 



17. Limestone, impure, shaly 6 



16. Calcareous shale 2 



15. Light shale 3 8 



14. Black shale 2 



13. Coal, Elmo 6 



