135 Devonian of Southern Indiana 



south the formations thin rapidly, and the Harrodsburg limestone 

 usually extends to within a mile or less of the easternmost out- 

 crop of the Riverside sandstone in southern Indiana and Ken- 

 tucky. The Riverside sandstone dips to the west or southwest at 

 the rate of from 26' to 64'* to the mile. This formation usually 

 presents along its eastern outcrop an escarpment from two to four 

 hundred feet high, facing the comparatively level plain formed 

 by the uniform weathering of the Black shale and the Devonian 

 limestone. In northern Indiana Mr. Hopkinsf has shown that 

 the lowest member of the Coal measures rests uticonformably on 

 the Riverside sandstone. 



In southern Indiana and Kentucky the Harrodsburg limestone 

 (Lower Carboniferous) is the formation which succeeds it. 



ROCKFORD lylMESTONE. 



The Rockford limestone is a thin bed of limestone from three 

 to six feet thick which separates the Black shale from the New 

 Providence shale. The formation is persistent throughout south- 

 ern Indiana and is known to extend as far north as Columbus ;[. 

 It has not been seen south of the Ohio. Nearly all of the fossils 

 described from it have been obtained near the village of Rock- 

 ford, from which the formation has received its name. The 

 earliest mention of this limestone seems to have been that of 

 Owen and Norwood in i847§. 



New Albany Black Shale. 



The Black shale has been correlated with various formations. 

 But the only local term which has been used is that given by 

 Borden 1 1 in 1873 — the New Albany Black shale. It is a fine- 



*Newsome, Proc. Ind. Acad. Sci. 1897, p. 254. 

 *Bennett, " " " " " " 259. 

 *Kindle, " '' " " 1895. 



t20th. Ann. Rept. Ind. Dept. Geol. and Nat. Hist., pp. 196, 197. 

 JProc. Ind. Acad. Sci., 1897, p. 261. 



^Researches among the Protozoic and Carboniferous Rocks of Central 

 Kentucky, made during the summer of 1846; 12 pp. 



||Ind. Geol. Rept., 1874, p. 88; 2d. Ann. Rept. 2d. Geol. Surv. 



