THE HAMILTON IN OHIO’ 
CLINTON R. STAUFFER 
Ohio State University 
At the beginning of the deposition of the Devonian formations 
belonging to the upper part of the Ulsterian and early Erian series, 
much of Ohio lay beneath a great inland sea. The island caused 
by the Cincinnati geanticline, and covering parts of Ohio, Indiana, 
and Kentucky, according to Ulrich and Schuchert,? probably became 
connected with the mainland to the southeast sometime during the 
Upper Silurian period, thus constituting it a peninsula of Appalachia. 
This condition probably continued until late in the Onondaga age, 
when the Cincinnati area once more became an island. 
The Cincinnati peninsula may have extended as far north as the 
mouth of the Detroit River, the northern limit of the Silurian outcrop; 
but in this there is an element of uncertainty, since preglacial and 
glacial erosion might have removed the Devonian formations which 
may have covered the northern end of this tongue of land. But 
whatever the extent-of this island or peninsula, the sea which sur- 
rounded it, wholly or in part, was continuous over a large part of the 
southern peninsula of Michigan, portions of Ontario, New York, and 
Pennsylvania, as well as Kentucky, Tennessee, Indiana, and Illinois. 
By the beginning of the Hamilton—that is, the Erian epoch— 
great changes had occurred. The small gulf in eastern Ohio had 
expanded into the Cumberland basin, the Cincinnati island was again 
free from the mainland, and the Traverse strait formed a means of 
communication between the Dakota and Mississippian seas; but 
the Kankakee peninsula still formed an effective barrier between 
this western sea and the Indiana basin of the Mississippian. In 
: A paper read before the Biological Club of the Ohio State University, February 
4, 1907. The work on this subject was done while a graduate student at the university 
(1905-6), and during the succeeding summer; hence it contains many of the ideas and 
suggestions of Professor Prosser. 
2 New York State Museum Bulletin No. 52 (1901), p. 648. 
3 Schuchert, American Geologist, Vol. XXXII, pp. 143-62, and Plates XX, XXI. 
59° 
