102 GEOLOGY OF OHIO. 



mation, we have an indisputable record of another of the great continental 

 submergences to which I have so many times referred. 



In Ohio we have almost exclusively the shore deposits, the lowest mem- 

 ber of the trinity ; but by going into Kentucky and traveling toward the 

 depths of the old Carboniferous sea, we find the series complete, and trace 

 the record of a progressive but doubtless a very irregular submergence of 

 southern Ohio in the last or Chester epoch of the Sub-carboniferous period. 



In order that this interesting episode of our geological history may be 

 fully comprehended, I will briefly review the phenomena presented by 

 the Lower Carboniferous Limestone in the region south and west of that 

 which it occupies in the State of Ohio. 



In the hills bordering the Ohio river the limestone member of the 

 group shows a thickness of from 30 to 40 feet ; going southward it rap- 

 idly increases in force, until, in central Kentucky, it forms fully half of 

 the Lower Carboniferous series. 



In all this region the lower, or silicious, portion of the group consists of 

 a series of fine-grained sandstones and shales, which, from the fact that 

 they compose many of the hills left by erosion in the excavation of the 

 valleys of the Ohio and its tributaries — hills which are known as the 

 Knobs — have received the popular designation of the Knobstones. In 

 the northern part of Kentucky, the " Knob rocks " are soft yellow, brown, 

 or bluish shales, with some beds of sandstone, the whole resembling 

 very closely our Waverly group as it appears in the central and 

 southern portions of the State. On the southern line of Kentucky, near 

 Burksville, this group of rocks is represented by a nearly homoge- 

 neous mass of blue and gray shales, capped above by the Lower Carbon- 

 iferous limestone, and resting upon the " black slate," the equivalent of 

 our Huron. From various localities in this region I have obtained 

 abundant fossils, characteristic of the Lower Carboniferous series in 

 Tennessee and Illinois, and these reach down quite to the black shale, 

 so that we are compelled to regard all these as of Carboniferous age. 

 We now know that our Waverly group, as exposed on the southern mar- 

 gin of the State, is the exact equivalent of these Lower Carboniferous 

 shales of Kentucky. 



In Michigan the Lower Carboniferous series, according to Prof. Win- 

 chell, consists of the Lower Carboniferous limestone above, the Michigan 

 Salt group in the middle, and the Napoleon and Marshall sandstones at 

 the base. The limestone has an average thickness of 60 feet, and, as 

 Prof. Winchell shows, represents the upper beds of the limestone group. 

 Above this series is found the Conglomerate ; below it the Huron shales, 

 regarded by Prof. Winchell as the equivalents of the Portage and Che- 

 mung in New York. 



