JE. M. Kindle — Devonian Shales of Northern Ohio. 187 



Art. XVIII. — The Stratigrajphic Relations of the Devonian 

 Shales of Northern Ohio ,'* by Edward M. Kindle. 



Introduction. — North eastern Ohio is an area of unusual 

 importance to students of late Devonian and early Carbonif- 

 erous formations and faunas. An acquaintance extending - over 

 several years with the border land of Devono-Carboniferous 

 stratigraphic paleontology in the Allegheny region and the 

 states adjacent to Ohio has resulted in the conviction that north- 

 eastern Ohio affords a better opportunity for a satisfactory dis- 

 crimination and placing of the boundary between the Devonian 

 and Carboniferous than any other area in the eastern states. 

 Here we are not confronted with a great series of nearly barren 

 beds in the vicinity of the base of the Carboniferous as we are in 

 southeastern New York and in much of the Allegheny region. 

 Neither do we have to deal, as in southern Kentucky! and Ten- 

 nessee, with a set of formations so nearly alike on the two sides 

 of the boundary as to make discrimination sometimes difficult. 

 On the contrary, the formations of the late Devonian and 

 early Carboniferous show very marked lithologic differentiation 

 in northeastern Ohio. Reference to a properly established 

 point is of no greater importance to the engineer than is the 

 selection by the stratigrapher of a horizon whose relative posi- 

 tion can be fixed with precision in the general time scale. 

 Northeastern Ohio is, therefore, a favorable region from which 

 to approach the difficult problems of the stratigraphy of the 

 black shale formations of the Ohio shale group. The geologist 

 can start here with a horizon for a reference plane which is 

 marked not only by the diverse lithology of the Bedford shale 

 and the Berea sandstone, but by an unconformity separating 

 the two. At present this appears to be the only horizon 

 between the Devonian limestone and the Carboniferous which 

 all geologists agree extends uninterruptedly across northern Ohio 

 from the Pennsylvania line almost to the Devonian limestone 

 belt south of Sandusky. Its position on the map (fig. 1, p. 190) 

 is shown approximately by the line separating the Ohio shale 

 area in outcrop from that under cover. This definitely-marked 

 horizon above, and the even more conspicuous boundary at the 

 top of the Devonian limestone below, mark the limits of the 

 formations with which we are concerned in this discussion. 



* Published with the permission of the Director of the U. S. Geological 

 Survey. 



f Limitations of space make it desirable to defer the further discussion of 

 the age of the Chattanooga shale to another paper. For critical review of the 

 evidence on record see this Journal, Feb., 1912. 



