338 THE ILLINOIS GLACIAL LOBE. 



the Illinois became an outlet for the large amount of water discharged from 

 Lake Chicago, and which caused a rapid deepening of the outlet and greatly 

 hastened the draining of the lake in the Morris Basin. During a portion of the 

 time that the Chicago outlet was in operation the Kankakee afforded a line 

 of discharge for the St. Joseph River and the waters poured into it from the 

 melting Saginaw lobe, which probably accounts for much of the erosion 

 accomplished along the borders of that stream and a measurable part of 

 that along the Illinois. This deepening of channel at the mouth of the 

 Kankakee has led to an excavation on the lower portion of the Kankakee, 

 which has progressed no farther up the valley than the rock barrier at 

 Momence. The upper portion is still flowing at the low gradient of its 

 large predecessor. 



Reviewing the above observations, the interpretation which seems to 

 best apply to this region admits only lakes of small extent or shallow depth, 

 and opposes the occupancy of the entire sandy area by water at any one 

 time. Grlacial lakes held in the Morris Basin and the Iroquois Basin may, 

 at their maximum extent, have formed a single body of water with an outlet 

 or outlets about 650 feet above tide. This lake level had probably become 

 lowered somewhat before the sand deposits were made in northeastern Iro- 

 quois County and along the lower course of the Kankakee, and possibly 

 may have been cut down nearly to the level of the uppermost well-defined 

 beach in the Morris Basin (560 feet). The sand deposits in the upper 

 Kankakee region and neighboring districts on the south seem best explained 

 as glacial outwash made during the withdrawal of the ice sheet to the posi- 

 tion marked by the Valparaiso and Maxinkuckee moraines, and probably 

 continued during the formation of those moraines. The upper Kankakee 

 Basin seems then to have been occupied only by a shallow body of water 

 which may have extended but little beyond the limits of the Kankakee 

 marsh. The method of formation of the well-defined south border of the 

 sand area in western Indiana, with its fluctuations in elevation, is as yet not 

 understood. The distribution of the sand ridges and their alternation with 

 bowldery belts, both in the Indiana district and along the south border of 

 the Kankakee, are features which do not lend themselves to a ready solu- 

 tion. Indeed, the entire interpretation is less definite than could be desired. 



