THE MLTSTOOKA TILL EIDGE. 319 



is not entirely beyond question. There seem, however, sufficient grounds 

 for referring certain features in that region provisionally to the late Wiscon- 

 sin deposits. These features are of two classes, namely, bowlder belts and 

 ridged drift. These are discussed separately, since their association is not 

 sufficiently close to make it certain that they represent a single ice advance. 

 As indicated below, the ridging (discussed under the head "Minooka Till 

 Ridge") may have preceded rather than accompanied the deposition of the 

 bowlders. 



SECTION I. THE MINOOKA TILL RIDGE. 



DISTRIBUTION. 



This till ridge receives its name from the village of Minooka, in north- 

 eastern Grundy County, which is situated on its crest. As noted above, it 

 is united with the Marseilles moraine in Kane County, and being smaller 

 than that moraine its discrimination may be made with difficulty. In the 

 northeast part of Kendall County it leaves the Marseilles moraine and takes 

 a southward course along the county line between Kendall and Will and 

 Grundy and Will counties to the head of the Illinois River. The crest as a 

 rule lies in the eastern tier of sections in Kendall and Grundy counties, 

 but in places touches western Will County. The width of the ridge, includ- 

 ing both slopes, is scarcely 2 miles. It consists of a single smooth ridge 

 on whose crest and slopes there are few swells exceeding 10 feet in height. 

 The ridge is crossed by two valley-like depressions which unite near its 

 western edge in sec. 13, T. 36, R. 8 E., and drain west into Au Sable Creek. 

 These are cut down to the level of the plain on the east side of the ridge. 

 They apparently were formed by the discharge of water from the ice 

 margin or ponded between the ridge and the receding ice front. 



PROBABLE LINE OP CONTINUATION. 



Up the Kankakee River, from the head of the Illinois nearly to the 

 State line, there is an occasional development of low drift ridges and o-entle 

 swells on the north side of the valley. On that side of the river, 1 to 3 

 miles back from the stream, there is an abrupt bluff-like rise of 25 to 50 

 feet, and the ridges and swells front this bluff or he immediately back of it. 

 This system of ridges and swells nearly everywhere stands slightly higher 

 than the plain which lies to the north. In the vicinity of Kankakee this 



