THE CINCINNATI GROUP 3 I 



the intervening section is poorly exposed. Those Ordovician 

 rocks of Ohio which stratigraphically belong below those exposed 

 at low-water mark in Cincinnati were included in the lower 

 division. The best and clearest section of these rocks is seen 

 near Point Pleasant, about twenty-five miles above Cincinnati, on 

 the Ohio river. Although the upper boundary of the lower 

 division cannot be readily determined with exactness at this 

 locality, the rocks included within this division were called the 

 Point Pleasant beds. 



At present the term Cincinnati group no longer includes all of 

 the Ordovician rocks exposed in Ohio. Since the Point Pleasant 

 beds and the lower fifty feet of rock at Cincinnati have been 

 identified as equivalent to the upper part of the Trenton, the 

 term Cincinnati group has been restricted so as to include only 

 the remainder of the Cijicijinati beds proper diXid the Lebanon beds 

 of Orton. 



In iSg/Winchell and Ulrich ' divided the Cincin?iati beds proper 

 of Orton into two divisions, identifying the lower with the Utica^ of 

 New York, and the upper with the Lorraine. For the term Lebanon 

 beds they substituted the term Richmo?id group, since the name 

 Lebanoji had been used by Professor Safford for a formation 

 included in the Trenton group of Tennessee, before Professor 

 Orton applied it to his upper division of the Cincinnati group. 

 No sections are described, but at Cincinnati the Utica is said to 

 be over 250 feet thick, and the Lorraine about 200 feet. The 

 line between the Utica and Lorraine is sufficiently well established, 

 to anyone acquainted with the Cincinnati section, by the state- 

 ment that at the base of the Lorraine there are some arenaceous 

 layers that on weathering frequently preserve the fossils as casts, 

 and that above these there are numerous layers of crystalline 

 limestone, three to ten inches in thickness, separated by rela- 

 tively thin bands of shale. The line of division between the 

 Utica and Lorraine is evidently the same as that between beds 

 XI and XII of Ulrich.3 



^Minnesota Geol. and Nat. Hist. Sitrv., Final Rept., Vol. Ill, Part II, p. ci. 



"Ulrich, "Correlation of Lower Silurian Horizons," Am. Geol.,\o\. I (1888), 

 P-3I5- 



Ibid., Vol. II, p. 41 



