PAPERS ON GEOLOGY AND GEOGRAPHY 389 



POSSIBLE HORIZONS FOR OIL AND GAS IX 

 XORTHEASTERX ILLIXOIS 



L". S. Gkaxt, X^orthwesteex Lxr^ersity 



During the last twenty months an interest in drilling 

 for oil and gas has developed in several places in the 

 northeastern part of the state. Companies have been or- 

 ganized, leases have been taken, and some actual drill- 

 ing has been done. The greatest interest has been near 

 the northern edge of Cook County, the southern edge of 

 Lake County, and in western McHenrj^ County. It con- 

 sequently seems proper on this occasion to outline brief- 

 ly the horizons in which there is a possibility of the oc- 

 currence of oil or gas. Beginning with the latest for- 

 mations, these horizons may be listed as follows: 



1. Glacial Drift. Lying below the most recent or Wis- 

 consin drift there is frequently an old soil zone or a zone 

 containing large amounts of vegetable material, especial- 

 ly remains of trees. Probably more than one such hori- 

 zon is present in some localities. Wells have been sunk 

 to one of these zones rich in organic matter, and gas has 

 been obtained from a great many such wells. The gas 

 pressure at first is occasionally quite strong, but usually 

 soon declines so that it is only a few pounds per square 

 inch and eventually this pressure may disappear alto- 

 gether. However, in a number of places such gas wells 

 have furnished and undoubtedly will continue to furnish 

 for years to come local supplies which can be used in 

 farm houses or possibly in small communities. Show- 

 ings of oil in these same horizons have also been re- 

 ported. 



2. Devonian Shales. In a few places in the eastern 

 part of the state, either in cracks in the Xiagara lime- 

 stone or in small masses probably detached in the drift, 

 remains of Devonian black shale occur. This shale is 

 frequently highly carbonaceous and might form a source 

 for oil or gas, but the lack of any extensive bodies of this 

 material under a suitable non-porous cover makes it im- 



