584 H. P. Cushing — Age of the Cleveland Shale of Ohio. 



Grand river valley in Ashtabula county, but has not been found 

 on the east side. The country there is, however, poorly 

 adapted to furnish exposures of the proper horizon. 



At the same time the Chagrin formation underneath increases 

 in thickness eastward with great rapidity, and in its eastern 

 extension fossils are much more abundant and range through a 

 greater vertical thickness of the formation than is the case about 

 Cleveland. In its upper portion also faunas seem to come in 

 which are no longer typical Chemung faunas, but higher ones. 

 I have, for example, collected abundant Syringothyris near Jef- 

 ferson, at least 100 feet below the summit of the beds which were 

 formerly referred to the " Erie " (now Chagrin) shale by New- 

 berry. These upper faunas have not been diligently collected 

 and studied, except perhaps very recently by Prosser. My im- 

 pression is that there comes over into the eastern townships of 

 Ohio a thinned and thinning edge of the formations which, in 

 western New York and Pennsylvania, have been called the 

 Oswayo and Knapp, or the Conewango and Knapp formations, 

 and which are regarded as younger than the Chemung. So 

 far as I know, these beds have not as yet been noted on the 

 west side of Grand river, while the Cleveland shale has not 

 been found on the east side. The Cleveland pinches out going 

 east, the others toward the west. Until the district has been 

 thoroughly covered in the effort to find the two in the same 

 section, so that their relative ages may be determined beyond 

 question, some doubt must attach to it. It seems to me 

 to be most probable that the Cleveland overrides the other, 

 and is the younger, in which case it can hardly be classed as 

 Devonian in age. My reason for the belief is that, up to the 

 point of its disappearance, the Cleveland sticks tightly to the 

 base of the Bedford ; and the Bedford overrides these other 

 formations on the east side of the Grand river valley. But I 

 most frankly admit that this is nothing but a surmise. I sim- 

 ply want to point it out as a possibility, and to urge it as the 

 most promising method of settling what the age of the Cleve- 

 land shale really is. But until it is shown that the Cleveland 

 does not override these formations, the conditions seem to me 

 to strongly suggest caution in asserting the Devonian age of 

 the Cleveland shale. Just as the conditions to the west of 

 Cleveland seem to me to suggest caution in asserting that the 

 whole, or even the greater part, of the Huron shale is older 

 than the Chagrin. 



In closing I wish to make one more suggestion, namely, that 

 if the Conodont faunas of the Huron and Cleveland shales are 

 to receive detailed study, it would add much to the importance 

 and completeness of the results if the similar faunas of the 

 Sunbury were included. I think no one questions the Waver- 

 lyan age of the Sunbury. 



Western Reserve University, Cleveland, Ohio. 



