336 THE ILLINOIS GLACIAL LOBE. 



extensive lake, therefore, can scarcely have had a level on its south border 

 higher than the lower parts of the ridge that forms that border of the sandy 

 area, or 675 to 685 feet above tide. This is about the elevation of the 

 sandy ridge which leads from Monon Creek west to Percy Junction. It is 

 also about the elevation of the eastern end of the Kankakee marsh at its 

 junction with the gravel plains bordering the Valparaiso and Maxinkuckee 

 moraines. It is fully 50 feet lower than the highest parts of the sand- 

 covered area, not only those on the east borders but also points in the 

 interior. A lake with this elevation could have had but shallow depth 

 throughout much of the Indiana portion, and interrupted as it must have 

 been by numerous islands it could scarcely have allowed wave action of 

 much strength. It, therefore, seems improbable that lake waves should 

 have caused the formation and deposition of much of the sand. 



The hypothesis of glacial outwash as the chief contributor of sand, and 

 of wind as an important distributor, apparently needs to be supplemented 

 by that of the presence of a shallow body of water over much of the sandy 

 area during and for some time subsequent to the retreat of the ice lobes. 

 Even now much of the Kankakee marsh is covered throughout the greater 

 part of the year by a broad shallow body of water in which the current is 

 very sluggish and which resembles a lake more than a stream. 



The Avestern portion of this sandy area needs separate interpretation, 

 since the saiad deposits there appear to have had a history somewhat inde- 

 pendent of the eastern portion. 



As above noted, the sand deposits on the outer or western face of the 

 Iroquois moraine in eastern Iroquois County in all probability were largely 

 contributed by the ice sheet at the time that moraine was forming. This 

 being the case, they antedate the deposits found east of that moraine. In 

 case the correlation of the Iroquois moraine with the bowldery strip along 

 the south side of the Kankakee in Will and Kankakee counties, Illinois, is 

 sustained, the sandy belts found in close association with these bowlders 

 would perhaps be of the same age as those of northeastern Iroquois County, 

 Illinois, with which they connect in southeastern Kankakee County. It 

 seems probable that a shallow lake occupied northern Iroquois County 

 at that time. Possibly it stood as high as the sand ridge which leads 

 through Onarga and Ridgeville (675 feet above tide), though it seems more 

 probable that it had shrank to a lower level, since there appears to have 



