582 H. P. Gushing — Age of the Cleveland Shale of Ohio. 



locality. There is no real Sunbury in the section at Bedford, 

 the horizon being occupied by a few feet of light-colored shale. 

 Above this there is a blackish shale, the Orangeville, but the 

 merest tyro in geology could not confuse this with the Cleve- 

 land when one considers the prominence of the Berea grit in 

 that uninterrupted section. But the matter is finally settled 

 for us by Newberry's definite pronouncement that he collected 

 these fossils himself; he says : " At Bedford I obtained from 

 this stratum quite a number of fish-teeth consisting of species 

 of Polyrhizodus, Cladodus, and Orodus ; all Carboniferous 

 sharks." * 



Aside from the frequent tiny scales of Paleoniscus (?) remains 

 of fishes are rare fossils in the Cleveland shale. The local 

 collector, he who diligently scans his ledges day after day 

 throughout the year, can make collections at some localities. 

 But the geologist, spending a day or two at a locality and then 

 moving on, is exceedingly fortunate if he finds in that time 

 any fish remains whatever worth taking along. Under these 

 circumstances the fact that subsequent collectors have failed to 

 report these forms from the Cleveland shale is not so surpris- 

 ing as it might seem. Some years ago, however, I collected 

 from the Cleveland shale at Bedford a fragment of a spine, 

 which tends to substantiate Newberry's assertion. 



Age of the Cleveland Shale. — I have had in manuscript for 

 some time a report on the geology of three quadrangles in the 

 Cleveland vicinity, the result of recent field work. Earlier 

 work had given me a familiarity with the formations concerned 

 all across northern Ohio. In two respects this work has a 

 bearing on the problem discussed by Mr. Kindle, and these I 

 wish briefly to set forth. 



Shales west of Cleveland — At Cleveland the Cleveland shale 

 is a band of black, slaty shale, 20 to 50 feet thick, which is 

 most sharply delimited from the underlying Chagrin shale and 

 the overlying Bedford shale. The same conditions persist east 

 of the city. But in West Cleveland the true Cleveland shale is 

 underlaid by from 15 to 20 feet of blackish soft shale, with thin 

 bands of blue shale, which separates it from the Chagrin below. 

 This is well exposed along Big Creek. A few miles farther 

 west, along Rocky river, this blackish shale has increased to 

 60 feet in thickness, and the steady increase in thickness seems 

 to continue to the west edge of the Berea quadrangle, beyond 

 which our detailed work has not gone. This increasing thick- 

 ness, coupled with a westerly clip, puts the Chagrin summit 

 below the lake level at Avon Point. 



Now this blackish shale must be one of three things : it may 

 represent a lateral change in character of the Chagrin shale ; 

 it may represent a downward thickening of the Cleveland shale, 



* Geol. Surv. Ohio, vol. i, p. 189. 



