GEOLOGICAL AND NATURAL HISTORY SURVEY. 19 



Where best developed the members of «this morainic system 

 have a relief of fifty to seventy-five feet above plains on the outer 

 border, but, like the S'helbyville system, the relief is less pro- 

 nounced on the inner border. In Indiana the belts have less relief, 

 seldom more than thirty or forty feet. Where best developed, the 

 members of this morainic system are one to two miles in width. 

 The surface is usually strongly undulating, a feature which dis- 

 tinguishes the moraines from the bordering nearly level plains. 

 The surface expression is on the whole stronger than in the Shelby- 

 ville moraine. 



In structure this morainic system does not differ markedly 

 from the Shelbyville system. The ridges are composed mainly 

 of a soft till. The soft till extends to a level somewhat lower 

 than the base of the ridges, a feature which is thought to indicate 

 that the Shelbyville drift is here present in considerable thickness. 

 Beneath the soft till of the Shelbyville drift a black soil is found, 

 Which forms the surface of a drift older than the Shelbyville, pre- 

 sumably the Illinoian drift sheet. 



Bloommgton Morainic System. — This is a more prominent 

 morainic system than the Champaign. It is traceable from West- 

 em Indiana westward across Central Illinois in a somewhat indi- 

 rect course (with a re-entrant angle near Gibson City) nearly to 

 the Illinois Valley. Whether this system crosses the Illinois just 

 above Peoria and becomes combined with an earlier system, or has 

 its continuation in certain local developments of morainic topog- 

 raphy along the east side of the Illinois, northward to the bend 

 near Hennepin, is not fully determined. It is thought that the 

 moraine leading from the bend of the river northeastward and 

 passing near Mendota and DeKalb belongs to this system. At the 

 east this system is overridden by a later moraine in Benton and 

 Warren Counties, Indiana. 



The portion east from the Illinois River has, in places, three, 

 and elsewhere two well-defined members separated from each 

 other by narrow plains. The outer member of the system has 

 generally a relief of 75 to 100 feet above plain tracts south of it, 

 thus approaching in strength the Shelbyrille system. 



In structure the drift of this morainic system closely re- 

 sembles that of the two systems outside of it, being chiefly a soft 

 blue till. It rests upon a soft till, which is thought to be the 

 northward extension of the Shelbyville sheet. This in turn is 

 underlain by a hard till, probably of the Illinoian stage. 



The topography is of a swell and sag type, rather more pro- 



