246 FRANK LEVERETT 



well the time between the culmination of the Iowan and Wis- 

 consin glaciations as if taken where the Shelbyville sheet over- 

 lies Iowan till. 



The loess has been traced back in valley exposures several 

 miles beneath the Shelbyville till sheet in northern Tazewell 

 county, Illinois, and beneath the combined Shelbyville and 

 Bloomington sheets in Woodford and Bureau counties. Farther 

 south it has been recognized in well sections in southern Taze- 

 well, northeastern Logan, western De Witt, southern Macon, 

 and western Sullivan counties, Illinois. The phase of loess 

 known as white clay has been traced several miles up the Kas- 

 kaskia and Embarras valleys in Shelby and Coles counties 

 beneath the Shelbyville till sheet. 



Of the several exposures those east of Peoria in northern 

 Tazewell county are the best displayed. Decisive evidence is 

 also found at these exposures of an interval of some length 

 between the deposition of the loess and the deposition of the 

 overlying Shelbyville till sheet. In view of these conditions in 

 the vicinity of the city of Peoria it has seemed appropriate to 

 apply the name Peorian to the interval between the Iowan loess 

 and the Shelbyville till sheet, a till sheet which appears to be 

 the earliest of the Wisconsin series. 



In exposures along the T. P. & W. R. R., east of Peoria, 

 and also on the east bluff of the Illinois opposite that city, the 

 Shelbyville sheet is underlain by a bed of fossiliferous loess, 

 similar to that found on the surface of the Illinoian outside the 

 limits of the Shelbyville drift sheet, both in texture and in age. 

 The loess is 8 to 12 feet in thickness, or about the same as on 

 the uplands outside the Shelbyville sheet. It occurs at a cor- 

 responding elevation of about 200 feet above the Illinois River. 

 Beneath it there is exposed fully 100 feet of the older drift 

 sheet. 



The upper part of the loess to a depth of two or three feet 

 presents a reddish brown color, and is thoroughly leached. The 

 leaching extends usually to a depth of about six feet. But 

 beneath that depth the loess is often calcareous. The Shelby- 



