218 ILLINOIS STATE ACADEMY OF SCIENCE 



glacial waters, a valley train was deposited, which may 

 have come from the ice during the building of the Cerro 

 Gordo moraine. Since the disappearance of the ice, the 

 sand and gravel fill has been partly eroded away and a 

 flood-plain, 150 to 200 feet wide, has been developed on 

 both sides of the stream. 



RELATION TO THE RESERVOIR PROJECT 



According to the foregoing interpretation the "hard- 

 pan," or glacial till, which is to receive the cut-off sheet- 

 ing, is drift of the Illinoian ground moraine and not drift 

 of the Wisconsin terminal moraine. Since the drift of the 

 Illinoian ground moraine was deposited chiefly beneath 

 the ice, rather than at its terminus, it is a typical clay-till. 

 It is, therefore, unlikely that it contains lenses of sand and 

 gravel thick enough to afford excessive sub-surface leakage 

 as would likely be the case if the drift were a part of the 

 Shelbyville moraine. 



