OLENTANGY SHALE OF CENTRAL OHIO 341 



mentation was continuous from Olentangy into Huron time, but the 

 Huron type alone is represented in northern Ohio, where by overlap 

 it rests upon the eroded surface of the Prout limestone. The latter 

 is absent in central Ohio, where either it was never deposited, or, 

 what is more likely, it was removed by pre-Huron erosion. This 

 erosion extended down to the Delaware limestone, though it is not 

 impossible that a part of the lower Prout series is represented in the 

 central area by the Delaware limestone itself. If the name "Prout" 

 is to be restricted to the limestone member of the northern series, 

 then the shale below it must receive another name. It certainly is 

 not Olentangy, which name belongs to the earliest Upper Devonian 

 formation of central Ohio. In my report on The Devonic Formations 

 of Michigan I have proposed the name " Arkona beds" for the shales 

 lying below the Encrinal limestone of the Thedford, Ontario, region. 

 If, as Stauffer holds, the shales below the Prout limestone are the 

 equivalent of these Ontario shales, which he calls Olentangy, then 

 the name "Arkona " may also apply to them. It may be wiser, how- 

 ever, to refer to them as the Plum Creek shales, since the distance 

 between Arkona and Plum Creek is too great to permit of positive 

 identification. True, Dr. Shimer and myself correlated the 

 Encrinal limestone of Thedford with that of western New York, on 

 the basis of faunal characters, and this correlation may be correct. 

 At the same time, we now know that the Encrinal of western New 

 York (Morse Creek) and that of central New York (Tichenor) are 

 not the same beds. I have also shown 1 that the faunas of the 

 shales below the Morse Creek in Eighteen Mile Creek occur in the 

 shales above this limestone 60 miles to the east, where they are not 

 found below that limestone. I have also shown that this typical 

 Hamilton fauna is absent from the beds above the Morse Creek 

 limestone at Eighteen Mile Creek, there being thus a complete 

 inversion of faunas. On purely faunal grounds the shales below 

 the Morse Creek at Eighteen Mile Creek would be correlated with 

 the shales above that bed at Moscow and elsewhere in the Genesee 

 Valley. The explanation of this and the relation of the western 

 New York Hamilton faunas to the Thedford and Michigan Traverse 



1 "The Faunas of the Hamilton Group of Eighteen Mile Creek and Vicinity in 

 Western New York," 16th Annual Report, N.Y. State Museum, 1898, p. $30. 



