THE MARSEILLES MORAINE. 313 



The depth of surface oxidation in this moraine is less than on any other 

 moraine of the Wisconsin series within the area under discussion. In Liv- 

 ingston County the blue till is commonly entered at 4 to 6 feet, and in 

 places at even less depth. The oxidized till, therefore, has scarcely half 

 the depth usually found in the Wisconsin drift sheets. The slight depth of 

 surface oxidation is probably attributable to the compactness of the till, 

 which is nearly impervious to water. It can not be attributed to flatness 

 of sui-face, because the depth of oxidation is found to be very slight on 

 undulating as well as level portions of this drift sheet. 



The sections of many wells obtained along this moraine and on the 

 inner border are presented in the discussion of wells (Chapter XIV) in the 

 counties traversed by the moraine. These serve to indicate the great 

 preponderance of till over assorted material in the portion of the drift 

 referable to the Marseilles moraine. They also serve to indicate the rela- 

 tive proportions of till and assorted material in the sheets of older drift 

 underlying the Marseilles and other Wisconsin drift sheets. 



CHARACTER OP THE OTJTWASH. 



Along Fox River, in Kane and Kendall counties, just outside the Mar- 

 seilles moraine, there is a belt of coarse gravel. In places the deposit lies 

 mainly on the same side of the river as the moraine, but generally it is on 

 the opposite side. At Batavia it is chiefly on the west side, at Aurora on 

 the east side, and at Yorkville on the west side. At Millbrook and at Mill- 

 ington the larger part of the gravel is on the east side of the river. The 

 belt of gravel extends but a short distance below Millington, the valley 

 below that point being cut in till and rock strata. The origin of this belt 

 of gravel has not been decided. Possibly it is referable to the invasion 

 which formed the Marseilles moraine, but quite as probably it should be 

 referred to the later advances of the ice sheet, during which the Marseilles 

 moraine was partially overridden. The gravel is so extensive in Kane and 

 Kendall counties and so small in amount farther down Fox River as to sug- 

 gest the interpretation that it forms an extensive delta in northern Kendall 

 and southern Kane counties, and that free drainage or escape of the waters 

 down Fox River had not been established. 



In the vicinity of the Illinois River there are indications of a lake-like 

 expansion of outflowing 'waters whose borders are found in the sand ridges 



