2 70 MORRIS M. LEIGHTON 



ment is hereby recorded. The writer also wishes to express 

 his appreciation of the distinct service rendered by his assistants, 

 Dr. E. P. Rothrock, of the University of South Dakota, and Messrs. 

 George E. Ekblaw and C. P. Halushka, students at the University 

 of Illinois. 



THE BELVIDERE LOBE 



Extent. — The Belvidere lobe extends as far west as Stillman 

 Valley, Ogle County, within 4 miles of the present course of Rock 

 River (see Fig. 2). It includes only a part of the territory which 

 was mapped lowan in United States Geological Survey Monograph 

 XXXVIII, and its boundary transects the old lowan area, and 

 excludes the drumhnoid forms of northwestern Boone County which 

 are regarded as lUinoian in age. 



The ice built a curving moraine which may be traced from a 

 point i| miles south of Holcomb to a point i^ miles west of Davis 

 Junction and thence northeast to the forks of Kishwaukee River. 

 Some kames enter into its constitution and increase its morainal 

 aspect. Beyond this moraine, the occurrence of relatively fresh 

 drift, as revealed by auger borings, relatively fresh gravels as north 

 of Stillman Valley, a smoothed aspect of the topography, and the 

 narrow gorge of the Rock River just beyond the isolated hill at the 

 mouth of the Kishwaukee River, indicate that the ice reached its 

 hmit some 4 miles at a maximum beyond this moraine without leav- 

 ing such marginal accumulations as might be called a moraine. 

 West and north of Belvidere and northeast of C apron there are 

 thickened marginal deposits, but elsewhere they are poorly devel- 

 oped or entirely lacking. No valley trains have been identified; 

 whether there were none originally or whether they have been 

 buried by the alluvial back-water fill from the Late Wisconsin Valley 

 train of Rock River and Kishwaukee River cannot be determined. 

 Back within the area there are some well-developed knolls and ridges 

 of fresh aspect, made up of both till and gravel. The drift is thick 

 enough over some areas to control the major features of the topog- 

 raphy, but near the margin the old land surface is incompletely 

 masked. Probably the average thickness does not exceed 15 or 20 

 feet. 



