OLENTANGY SHALE OF CENTRAL OHIO 339 



That exact correlation with the Encrinal limestone of Lake 

 Erie is possible may perhaps be doubted, since the calcareous beds 

 increase in number westward. The Encrinal (Morse Creek) lime- 

 stone is the attenuated eastward extension of the great Alpena 

 limestone of Michigan, and the Prout limestone probably represents 

 one of the lower Traverse limestones of Michigan. Still, Stauffer 

 is undoubtedly correct when he makes the age of the Prout lime- 

 stone and associated shales lower Hamilton, and it is gratifying to 

 me to feel myself in substantial agreement with one who has made 

 such prolonged studies of these formations and faunas. 



When it comes to the Olentangy shale of central Ohio, however, 

 Stauffer and I are in cordial disagreement. He makes it the equiva- 

 lent of the Prout limestone and shales of the north and so of 

 Hamilton age, while I regard it as a part of the Huron shale series, 

 and referable to the Upper Devonian. 



Although I had held this view for many years, it was not until 

 the summer of 19 14 that I was enabled thoroughly to test my con- 

 clusions in the field. At that time I examined all the important 

 exposures of the formation in Delaware County, beginning with 

 WinchelPs type locality, on the Olentangy River. A new section 

 opened here for commercial purposes made a careful study possible. 

 The actual- contact between the Olentangy and Huron is sharp, 

 but perfectly even and uniform. In the upper portion of the gray 

 Olentangy are several thin bands of black or chocolate-colored 

 shale of the type of the Huron. 



The bedding of the Olentangy shale is chiefly brought out by the 

 occurrence of thin bands of dark shale, and by more or less con- 

 tinuous layers of flat concretions. These are calcareous, up to 

 2 feet long by 1 foot thick, but mostly smaller. They abound in 

 iron pyrites, as does also the Huron shale overlying. In some 

 sections, as in the Deep Run and Lewis Center and Bartholomew 

 runs, the lower part of the Olentangy shale contains thin bands 

 of impure limestone. In one of these I found fish scales. In all 

 the sections, however, are found the thin bands of black shale in 

 the upper part of the gray, thus indicating a transition of the one 

 formation into the other. At the contact with the first great mass 

 of Huron shale there are sometimes found indications of a slight 

 drying of the surface of the Olentangy, with the formation of cakes 



