Geography of Ohio 165 



STRATIGRAPHY OF OIL AND GAS 



Below I give a list of the periods and the formations in which 

 the oil and gas of this state occur. 



Ordovician. The oldest rocks in the state, producing oil or 

 gas, are found in this period. The Trenton limestone is reached 

 in the western part of the state at a depth of about 1100 to 1500 

 feet. This formation is found on the surface next to the Ohio 

 River, but it dips towards the north, on account of the arching of 

 the Cincinnati anticline. The Trenton oil and gas fields appear 

 to be associated with this deformation. Elsewhere in the state 

 wells have been sunk into the Trenton but without success. The 

 farther east one goes, the deeper it is necessary to drill. The 

 extreme depth of a well in this limestone is reported as 3440 feet; 

 this well is near Ironton.^^ 



Silurian. Two formations of this period have economic value. 

 The Clinton sandstone supplies much gas in Knox, Hocking, 

 Licking and Fairfield counties. Some oil also occurs locally in 

 this sandstone. In Jefferson and Ashtabula counties gas is found in 

 the sand horizons of the lower Helderberg; very little oil, however, 

 occurs here. 



Devonian. In one formation of this period, the Ohio shale, 

 gas has been found for a great many years. This formation out- 

 crops along the southern shore of Lake Erie, westward nearly 

 to Sandusky. Probably no formation of the state contains so 

 many wells. These are all shallow, seldom going over 800 feet. 

 No one well has ever produced commercial gas, but has produced 

 sufficient to supply one or a few houses. The wells are long-lived ; 

 it seems not unlikely that no formation contains more gas than 

 does the Ohio shale. i' The gas appears to be widely distributed 

 in the formation, instead of being confined to a few reservoirs, 

 as is the case in most gas-producing rocks. 



Mississippian . Two formations of this period have commercial 

 value in oil and gas. The Berea sandstone, which outcrops 

 along an east-west line south of the lake, and then turns south- 

 ward across the state from the eastern side of Huron County, 

 dips to the east quite rapidly. In Washington and Monroe coun- 



1" Geological Survey of Ohio, vol. vi, (1888), p. 304. 

 1' Ibid., p. 413. 



