GIRTY, GEOLOGIC AGE OF THE BEDFORD SHALE 319 



Berea, respectively. In view of the fact that the Berea possesses a char- 

 acteristic fauna which has not been found in the sections under consid- 

 eration, whereas the Bedford fauna has been found there, and in a shale, 

 and at the base of the interval, it seems to me that that portion of the 

 interval would better be identified as Bedford alone, whatever is done 

 with the upper part, though the evidence would suggest the advisability 

 of calling the upper sandy beds Berea where they are present, and the 

 whole interval Bedford where they are not. 



The bearing which this aspect of the Bedford-Berea stratigraphy has 

 on the question of the geologic age of the Bedford shale is not entirely 

 clear. From one point of view, one might say that it did not affect the 

 classification of the beds at all, except insofar as it made them difficult 

 to distinguish in the field and to delineate on a map. On the other 

 hand, it might be urged with some force that since by the expansion and 

 differentiation of the Chattanooga shale in a northward direction, that 

 formation seems to cover an interval including the lower Cuyahoga, the 

 Berea, the Bedford, the Chagrin and probably the Huron formations, 

 and in a manner to bind them together into one group of sediments, 

 they ought all to be classed as Devonian or all as Carboniferous. This, 

 however, does not at all agree with the facts, where these formations are 

 differentiated and developed in an unequivocal manner, and I believe 

 that it should not prejudice such a classification of the rocks as is indi- 

 cated by the facts ascertainable under those conditions. 



Therefore, while the weight of the evidence is not entirely cast on 

 one side of the question, I believe that so far as the facts are known 

 they indicate the line at the base of the Berea sandstone as the proper 

 position of the Devonian-Carboniferous boundary in northern Ohio. 

 This is because that boundary is marked by an unconformity, by the 

 presence of a basal sandstone and by a pronounced faunal change, such 

 that while the fauna of the Berea ("Corry") sandstone has a distinctly 

 Carboniferous facies and is probably to be correlated with the Kinder- 

 hook group of the Mississippi Valley, that of the Bedford shale, though 

 its stratigraphic position is above the typical Chemung, has, in connec- 

 tion with the other "Bradfordian" faunas, a distinctly Devonian facies. 



