Devonian Shales of Northern Ohio. L99 



shale is everywhere characterized in Ohio by spherical concre- 

 tions often of large size. Concretions of this type are entirely 

 unknown in the Cleveland shale both in its typical area and 

 outside of it. On the other hand, in the region where the 

 Cleveland shale is typically developed the thin limy bands with 

 cone-in-cone structure are common. This type of rock has 

 never been found associated with the spherical concretions. 

 As these two very peculiar and striking lithologic features 

 characterize distinct parts of the Ohio shale group (upper and 

 lower parts) from northern Ohio into Kentucky, they seem to 

 be very valuable and desirable lithologic characters to use in 

 discriminating the Huron from the Cleveland shale. Although 

 careful watch was kept throughout the season, these two 

 features were nowhere found in the same or even in closely 

 associated beds. It is proposed, therefore, to limit the term 

 Huron shale to those beds of the Ohio shale exposed on the 

 Huron River, at Rye Beach and elsewhere, in which the 

 spherical concretions occur and the Cleveland shale to the higher 

 beds in which they do not occur and in which the cone-in-cone 

 structure does occur. The spherical concretions are a persistent 

 feature of the lower or Huron shale as far south as the first 

 tier of counties in Kentucky.* The cone-in-cone bands of the 

 Cleveland persist still farther and have been observed as far 

 south as Irvine, Kentucky. Using these criteria for distin- 

 guishing between the two black shale members, the Huron will 

 have in the Huron section a thickness of probably 100 feet. 

 At the base of the Huron along the Olentangy River about 25 

 feet of gray argillaceous shales, known as the Olentangy, 

 separate the Huron from the Delaware limestone. 



If the convenience of those geologists who are engaged with 

 the correlation and classification of rocks had been considered 

 when our Paleozoic sedimentaries were laid down, we would 

 no doubt have had the Ohio shale terranes definitely sepa- 

 rated by diastrophic breaks and persistent in lithologic type. 



* In the paper referred to (see p. 188), Mr. Ulrich has put the question 

 whether the drill has ever been known to strike one of these concretions in the 

 Huron east of Cleveland where he assumes its absence. The question of course 

 assumes a negative answer and consequent confirmation of the claim of the 

 propounder that both the concretions and the formation which they charac- 

 terize are absent below the Chagrin. Let us put a similar question concern- 

 ing the Cleveland. Has any one ever heard of a drill striking one of the 

 fiat fish-bearing, or one of the dike-like concretions, or a cone-in-cone band 

 in the black shale under the Bedford southwest of Cleveland ? In this region 

 the curious wall-like concretionary structures are not uncommon and the flat 

 concretions are abundant while the cone-in-cone bands are practically 

 universal. The writer must confess that he has not heard of drillers striking 

 any of these unique structures in either case. But this does not lead him 

 to doubt either that the black shale below the Bedford to the southwest of 

 Cuyahoga River is the Cleveland nor that the black shale below the Chagrin 

 east of Cleveland is the Huron. 



