1 84 The Ohio Naturalist. [Vol. VII, No. 8, 



THE DEVONIAN LIMESTONES OF CENTRAL OHIO AND 



SOUTHERN INDIANA. 



Clinton R. Stauffer. 



A comparative study of the two regions, lying on opposite 

 sides of the Cincinnati island, shows that there is a remarkable 

 similarity between the Devonian limestones of central Ohio and 

 southern Indiana. This is perhaps more evident from a litholog- 

 ical point of view although the paleontology of the formations 

 of the two places is very similar and the stratigraphic arrange- 

 ment is identical. 



These deposits in Ohio have been divided into the Columbus 

 and Delaware limestones. The Columbus presents two very 

 different lithological phases which are persistent throughout the 

 state. In southern Indiana Dr. Edward M. Kindle has recog- 

 nized three distinct formations, the Geneva and Jeffersonville 

 limestones and the Sellersburg beds,^ the latter including the 

 Silver Creek hydraulic limestone of some authors. 



The lower of these Indiana formations, stratigrar)hically, is 

 the Geneva limestone which "is generally a massive light buff to 

 chocolate brown saccharoidal magnesian limestone" in which 

 "fossils are extremely rare at most locations and occur usually 

 as casts when found. '"^ It thins out toward the Ohio river 

 but may be seen in the vicinity of Charleston, along the hill above 

 the "Lick" and at the road side east of town. 



In Ohio the lower thirty-five to forty feet of the Columbus 

 limestone answers admirably to the above description. It is 

 usually a porous brown limestone high in its percentage of mag- 

 nesium carbonate. The bedding is irregular and frequently 

 almost wanting. Oblique jointing, although not necessarily 

 characteristic, is common. It contains but few fossils all of 

 which arc usually but poorly preserved, existing mostly as 

 moulds with occasional casts. Bituminous matter is also usually 

 found, either as thin films between layers or within the rock 

 itself causing an irregular banding. Pockets of calcite crystals 

 are often found and occasionally some gray chert. 



The upper sixty-five or seventy feet of the Columbus lime- 

 stone is usually a crystalline gray limestone high in its percentage 

 of calcium carbonate. It contains great numbers of excellently 

 preserved fossils and considerable gray chert which is also quite 

 fossilifcrous. The limestone occurs in even beds which vary from 

 comparatively thin to massive layers. The lower part of this 



1. TAventy-fifth Annual Report of the Department of Geologv and 

 Natural Resources of Indiana. (1900), pp. ry.iS 5.^6. 



2. Ibid. pp. 53.5, 536. 



