T. (J. CJiainberlin — Diversity of the Glacial Period. 181 



3d stage. Deposition of main body of loess and associated 

 silts. Apparently very low altitude and slack drainage. 



4th stage. Long interval of deglaciation. Large valleys 

 cut in loess. 



5th stage. Formation of thick drift sheet with morainic bor- 

 der 75 to 100 feet deep. Ice reached Shelbyville (not Litch- 

 field) at maximum advance. Later sub-stages of glaciation 

 marked by moraines or thickenings of drift at the margin of the 

 sheets (40 to 50 feet). Intervals between successive moraines 

 probably short since evidences of oxidization, leaching, erosion 

 and soil accumulations are scant. Elevation about as at present 

 when Shelbyville moraine was formed. Drainage less vigor- 

 ous when later moraines of this stage were formed. 



6th stage. Interval during which ice lobes and ice currents 

 were shifted. Length probably considerable, though decisive 

 evidence is wanting. 



7th stage. Latest series of ice lobes south of Lake Michigan 

 formed. Elevations greater, drainage freer. Minor moraines 

 marking later sub-stages. Followed by the lake deposits of 

 the region. 



Mr. Leverett is inclined to correlate the outer moraine in 

 Eastern Ohio and Northwestern Pennsylvania (there called 

 the terminal moraine in a double sense by some -writers), with 

 the outer member of this last group, which is about 240 miles 

 from the extreme limit of drift in Illinois, but owing to the 

 fact that the moraines in the intervening region became 

 bunched together in the angles between the ice lobes, an 

 entirely demonstrative correlation by tracing is difficult, and 

 he withholds a final judgment. But leaving the doubt as wide 

 open as the phenomena will admit, he regards a correlation of 

 the outer moraine of Western Pennsylvania with anything 

 within 120 miles of the southern limit in Illinois as opposed 

 to all evidence. 



In his elaborate monograph on " The Pleistocene History of 

 of Northeastern Iowa,"* Mr. McGee defines and illustrates, 

 with great fullness, the following series : 



1. A lower till ranging in thickness from a mere veneering 

 to 200 feet, averaging perhaps 50 feet, characterized by green- 

 stone erratics (in contrast with the granitic erratics which 

 characterize the upper till) ; nowhere displaying a moraine- 

 like peripheral thickening, but everywhere attenuated toward 

 its margin. General facies ancient, ferrngination and oxida- 

 tion greater than that of upper till. 



2. A forest bed found in 40 per cent of the well- sections, 

 20 to 25 per cent of them showing a definite bed. Old soil 



* 11th Annual Report TJ. S. Geological Survey. 



