THE DELAWARE LIMESTONE 427 



ing Club. Formerly the upper part of the Columbus limestone was 

 fairly well shown in the bluff of the Scioto River for some distance 

 below this locality, while Slate Run affords a good section of the 

 Delaware limestone and the overlying Olentangy shale. At this 

 locality Whitfield first noticed the brownish shales containing a 

 Marcellus fauna, although in the description it is not located more 

 definitely than "six miles northwest of Columbus." A section 

 was furnished by Dr. Orton, which was published in Whitfield's 

 paper. 1 



Thickness Total Thick- 

 No. (Feet) ness (Feet) 



13. Ohio shale. — On the northwest bank, immediately n\± 107 



above the outcrop of Olentangy shale, is about 6 feet 



of the typical black, thin, arenaceous shale of this 



formation. The line of contact is sharp between 



these two shales. Farther up the stream, near the 



fence, the top of the Olentangy shale is near water- 

 level, above which is about n \ feet of the Ohio shale. 



A little farther up the run, and above the fence, are 



a number of concretions of various sizes imbedded in 



the Ohio shale. 

 12. Olentangy shale. — Bluish or greenish to drab argil- 22§ 95A — 



laceous shale, with the lithological appearance of 



typical exposures of Olentangy shale in Delaware 



County. One thin layer of brownish shale occurs at 



about the middle of the cliff, and two layers near its 



base. There are also thin layers of impure limestone, 



especially in the lower part of the formation, one of 



which, about 6 feet above its base, is 52 inches in thick- 

 ness. On Dr. Orton's section the Olentangy shale is 



given as 15 feet in thickness, 2 but this is obviously an 



underestimate. 

 11. Top of Delaware limestone. — A rather thin-bedded 13+ 7 2 f 



bluish-gray limestone, with occasional layers of chert, 



which extends to the top of the cascade. It may also 



be seen on the steep southeast bank farther down the 



stream, which is the best place for measuring its thick- 

 ness. 



1 Proceedings 0} the American Association for the Advancement of Science, Vol. 

 XXVIII (1880), p. 298. 



2 Ibid., p. 298. 



