COMPOSITE MORAINIC BELT OF NORTHERN ILLINOIS. 301 



referred to the Peorian interglacial stage, for they probably occur at the 

 junction of the Wisconsin and Iowan drift sheets. But it is possible that in 

 many cases they are of Sangamon age and occur at the junction of the 

 Iowan and Illinoian sheets. In the majority of cases they occur in the 

 lower part of the drift. On the elevated portions they seldom are found at 

 less than 125 feet from the surface, and in one instance (at Gilbert station) 

 a soil was found at 180 feet. The drift on the elevated portions apparently 

 averages not less than 200 feet. On the lower portions of the belt, in 

 southern Kane Count} 7 , the drift is correspondingly thinner. The buried 

 soil is found at much less depth, but at about the same elevation above tide 

 as in the higher portion. The occurrence of the buried soil, its depth and its 

 relation to other beds of the drift, may be seen by reference to well sections 

 of McHenry and Kane counties given on subsequent pages. 



As noted above, this portion of the composite belt abounds in knolls 

 and short ridges which are composed largely of gravel. These are largest 

 and most numerous along the inner slope adjacent to Fox River, but are 

 found occasionally on the elevated parts of the moraine — for example, near 

 the north line of Kane- County. These ridges occur both singly and in 

 groups. They are also arranged in chains or narrow belts. They present 

 considerable variation in structure. The majority have but little till with 

 the sand and gravel, but some present a large amount of till in the lower 

 portion. This is especially true of those on the elevated portion of the 

 moraine in northern Kane County. In several cases the knolls are found 

 to have a body of coarse gravel and cobble at their summits which extends 

 downward in a funnel-shaped mass toward the center of the hill. In other 

 cases the central portion of the hill is composed of sand and the gravel and 

 cobble is found in the peripheral portion. A knoll in sec. 14, T. 42, R. 7 E., 

 opened extensively for gravel, is found to contain alternations of till and 

 assorted material. The till apparently forms a network of connections 

 around lenticular masses of gravel. In most instances the gravel and cob- 

 ble is found to extend scarcely as low as the base of the knolls. Borings 

 have sometimes been made in the bottom of the giwel pits, and these usu- 

 ally penetrate a considerable depth of oxidized till. Indeed, the oxidation 

 appears to be fully as deep beneath these knolls as the average depth of 

 surface oxidation outside the knolls. The bedding of the assorted material 

 is seldom horizontal, but curves and dips as if the material had been subject 



