THE BLOOMINGTON MOEAINIG SYSTEM. 265 



elevation of about 625 feet. In these exposures the Peorian and Sangamon 

 both occur as noted above. Instances of buried soil at an elevation of 625 

 to 650 feet are reported from the vicinity of Cooper, which are probably 

 Sangamon. The Wisconsin drift ranges in thickness from 50 feet up to 

 fully 150 feet in this portion of Tazewell County. 



In northwestern McLean County instances of a buried soil and a change 

 from soft to hard till are found at a depth of 150 feet beneath the crests of 

 morainic ridges and at an elevation of 650 feet above tide. There are 

 instances of "black clay" at lower levels, which may prove to be soil hori- 

 zons. In the southwestern part of the county, in sec. 29, T. 24, R. 1 W., 

 and sec. 3, T. 23, R. 1 W. (which are situated south of the Bloomington 

 moraine), the fresh till extends to a much lower elevation than in neighbor- 

 ing districts. It seems probable, therefore, that there was a valley or con- 

 cealed lowland tract traversing these sections. In sec. 3 a black muck was 

 found below the fresh till at a depth of 200 feet and at an elevation of but 

 525 feet above tide. In the vicinity of Bloomington a black soil is found at 

 an elevation of 625 to 640 feet above tide, which probably is of Sangamon 

 age. Another buried soil occurs near the base of the drift at an elevation of 

 about 540 feet. This is beneath a hard till and is perhaps preglacial. North- 

 eastward from Bloomington the elevation of the surface of the Illinoian drift 

 sheet is found to soon reach 700 feet; at least wells in T. 24, R. 4 E. enter 

 a hard till at that elevation. One well in sec. 4 of this township is reported 

 to have entered hard till at an elevation of 750 feet above tide. South from 

 this township, in the vicinity of Leroy, a buried soil is found at an elevation 

 of 740 feet above tide, which is probably under the Shelbyville or lowest 

 Wisconsin drift sheet. Eastward the elevation of the surface of the Illinoian 

 drift appears to decline to 700 feet or less, as shown by wells in southern 

 Livingston, southwestern Ford, and western Champaign counties. The 

 elevation continues decreasing toward the north and east across northern 

 Ford, Iroquois, and Vermilion counties. The elevation of the Illinoian 

 surface throughout much of Iroquois County and northern Vermilion 

 County is 600 feet or less. 



In Iroquois County, as noted above, there are two soil horizons, one 

 being at the junction of the fresh and soft till with the harder till, the other 

 being in the midst of the hard till. There is little doubt that the upper soil 

 marks the base of the Wisconsin. But whether the sheet of drift which it 



