GREENE: DAKOTA-PERMIAN CONTACT. 3 



county, shows a typical succession of the Permian beds of that 

 region : 



10. Limestone, thin-bedded, and yellowish shales 5 ft. 



9. Limestone, massive 6 in. 



8. Shales, calcareous olive-gray, with limestone about four feet 



from bottom 16 ft. 



7. Limestone, grading through marly concretions to marly 



shales , 1 ft. 



6. Shales, marly gray , 4 ft. 



5. Shales, red, evenly bedded, with occasional indurated bands; 



in the lower portion are two layers of very impure semi- 

 crystalline limestone or dolomite, apparently thrown down 

 by precipitation. There are also four or five very thin lay- 

 ers of greenish shales 15 ft. 



4. Covered 10 ft. 



3. Limestone, two layers, separated by bluish shale ; upper lime- 



stone hard 3i ft. 



2. Shales, olive, indurated 4 ft. 



1. Shales, yellow calcareous and argillaceous limestone 2 ft. 



Covered slope below. 



The character of the Permian from a little different horizon 

 is shown in a section from the north bank of Mill creek, near 

 the middle of section 13, Charleston township, Washington 

 county : 



7. Covered. 



6. Limestone, light buff, cellular, rather thin-bedded 8 ft. 



5. Shales, bluish and yellowish 13 ft. 



4. Limestone, blue, laminated, fossiliferous 4 in. 



3. Shales, bluish 3 ft. 



2. Limestone, hard, buff, fossiliferous 8 in. 



1. Shale, blue, and covered slope to water level 17 ft. 



Cretaceous-Dakota. — The prominent bluffs of this forma- 

 tion are composed of a deep-red or brown, rather coarse- 

 grained, ferruginous sandstone. For this reason the forma- 

 tion is often spoken of as the Dakota sandstone, but this is 

 a misnomer, as the bulk of the formation is probably not a 

 hard sandstone, but clays and shales.^ Other exposures vary 

 greatly. In fact, it is hard to imagine a formation of a more 

 diversified character. It gives much evidence of being a shal- 

 low-water deposit, such as would be formed along shores and 

 in small estuaries by delta deposits, etc. Both the nature of 

 the deposits and the fossil content bear out this statement. 

 The land mass was probably a short distance east of the pres- 

 ent eastern outcrop, as the Dakota becomes more evenly strat- 



1. Gould. Trans. Kan. Acad. Sci., XVII, pp. 122-178. 1901. 



