SOME ESTIMATES OF THE THICKNESS OF THE 

 SEDIMENTARY ROCKS OF OHIO 



T. M. HILLS 

 Ohio State University 



Since the discovery of crystalline rock at a depth of 3,320 feet 

 at Waverly^ in 191 1, and at Findlay/ at a depth of 2,770 feet, in 

 1012, deep wells have been drilled in many parts of Ohio. From 

 their records, the following estimates are made of the thickness of 

 the sedimentary rocks along the eastern and southern borders of the 

 state. 



The data used^ have been taken from wells located along three 

 lines, two of them running east-west, the other north-south. The 

 first extends from Findlay through Cleveland eastward to the 

 central part of Ashtabula County, the second from the city of 

 Columbus east to northern Muskingum County, the third from 

 Norwalk to Jefferson Township, Jackson County. 



The two formations used as datum planes in the calculations 

 are the Trenton and the Clinton. The tops of these formations 

 are recognized with a reasonable degree of certainty by drillers. 

 Unfortunately, the two wells mentioned above are the only ones 

 that have passed through the Trenton rocks of the state. There- 

 fore the distance from the top of the Trenton to the crystalline 

 rocks must be taken from these wells and considered as constant 

 for the area. The wells in the eastern and central parts of the state 

 do not extend below the Clinton; therefore the depth from this 

 formation to the Trenton, and to the crystalline rocks below, must 

 be supplied from the known wells of other parts of the state. This 

 assumes that the Trenton-to-crystalline-rock interval is constant 

 over a wide area, and that the Clinton-to-Trenton interval varies 

 at a uniform rate. These are both broad assumptions, but with the 

 data available cannot be avoided. 



^ Condit, Amer. Jour. Sci., Fourth Series, Vol. XXXVI, p. 123, August, 1913. 

 ^ Acknowledgments are due The Ohio Geological Survey for the use of its files of 

 well data. 



