322 THE ILLINOIS GLACIAL LOBE. 



Such being- the case at the time the Valparaiso moraine was forming-, it fol- 

 lows that at the time the Minooka Ridge was formed the lake stood fully as 

 high, if not higher, for the Minooka Ridge antedated the the Valparaiso 

 moraine in its formation. The low part of the basin immediately west of 

 the Minooka Ridge stands only a few feet above the level of the beaches 

 referred to and would apparently have been extensively inundated during 

 the melting of the ice sheet, even if the outlet from the Morris Basin had 

 been cut down to the level of the well-defined beach bordering the Illinois 

 River. A vigorous discharge of waters across the basin could scarcely be 

 expected. Certain features which suggest vigorous discharge will next be 

 considered. 



The channels noted above, which cross the ridge a few miles north of 

 the head of the Illinois, seem to have been made by a stream with a current 

 having considerable volume, if not considerable strength. They are cut 

 down to a gradient too low to give the present small stream which drains 

 them a good gradient, and are consequently occupied by marshes. The 

 conditions under which the}' were formed were probably similar to those 

 which caused the gaps in the Marseilles moraine discussed above (pp 310, 

 314). A thin coating of sand is found in the portion of the basin immedi- 

 ately west and south of these channels, a feature which implies current 

 action, but perhaps no stronger than is consistent with the presence of a 

 lake or very broad lake-like stream. On the whole, the evidence seems 

 insufficient to establish the existence of good drainage conditions. 



Turning to the Kankakee for light as to drainage conditions accom- 

 panying the formation of the ridge on its north border, it is found that sand 

 deposits occur along the opposite side of the valley, forming a much more 

 conspicuous feature than on the west border of the Minooka Ridge. The 

 deposits extend back usually 3 or 4 miles from the present stream and 

 reach an elevation fully as high as the ridge on the north side of the valley. 

 They have been drifted in places into prominent dunes. This sand may be 

 interpreted either as the direct outwash from the ice at the time the ridged 

 belt north of the valley was in process of formation, or it may seem refer- 

 able to subsequent stream transportation, for the Kankakee Valley was the 

 line of discharge for glacial streams issuing from the Saginaw lobe during 

 the period embraced in the formation of two or more strong moraines, and 

 from a part of the Lake Michigan lobe during the formation of the Val- 



