276 THE ILLINOIS GLACIAL LOBE. 



bowlders 20 or 30 feet in depth. The excessive amount of coarse material 

 seems referable to the contribution of such material from the overhanging 

 ice during the building up of the terrace. For this reason the terrace has 

 been connected with the Bloomington rather than a later substage. Possiblv 

 some cutting of the valley of the Illinois took place between the heavy 

 deposition of gravel on the outer border and that near the inner border of 

 the moraine, in which case the deposits near the inner border may not have 

 been built up to the level of those on the outer border. This view seems 

 supported by the observations farther up the valley, no remnants higher 

 than that at Chillicothe having been found. 



Down the valley from Peoria there is a rapid decrease in the altitude of 

 the gravel terrace, a fall of 70 or 80 feet being made in the 10 miles to the 

 mouth of the Mackinaw River, just below Pekin. There is a great expansion 

 of the valley just below that city, in which the gravel has an elevation of 520 

 to 530 feet above tide, or 90 to 100 feet above the Illinois River. The gravel 

 is capped by sandy deposits, which are in places drifted into dunes 20 to 

 30 feet or more in height. Gravel deposits are conspicuous down the val- 

 ley beyond the mouth of the Sangamon River, but the material becomes 

 finer in passing down the stream. The gravel has a height of about 500 

 feet above tide at the mouth of the Sangamon, or 75 to 80 feet above the 

 level of the Illinois River. Farther down it gradually approaches the 

 level of the river, the highest terraces near the mouth of the stream, which 

 seem connected with the Wisconsin invasion, being but 40 to 50 feet above 

 low water. 



There appears to have been no gravel outwash into Kickapoo Creek 

 Valley in northern Peoria County, although this stream follows the outer 

 border of the moraine quite closely for a distance of 7 or 8 miles. Upon 

 turning away from the moraine the creek cuts through the Shelbyville 

 moraine, and it is probable that this offered an obstruction to the rapid 

 escape of waters from the ice margin. 



In southeastern Stark County there is a low plain extending back from 

 Spoon River Valley to the Bloomington moraine which received a slight 

 outwash from the moraine. A few exposures were found where gravel to a 

 depth of several feet was deposited. It seems, however, to have been only 

 a weak point of discharge, as the gravel deposits scarcely extend to Spoon 

 River Valley, though this valley approaches within 6 or 7 miles of the 





