OUTLINE OF DRIFT SHEETS AND INTERVALS. 51 



4. Second or Yarmouth interval of recession or deglaciation. 



5. lUinoian drift sheet. 



6. Third or Sangamon interval of recession or deglaciation. 



7. lowan drift sheet and main loess deposit. 



8. Fourth or Peorian interval of recession or deglaciation. 



9. Early Wisconsin di'ift sheets, as represented in Illinois, the display in 



the Ohio district being less complete. 

 a. Shelbyville morainic sj^stem. 

 1). Champaign morainic system. 



c. Bloomington morainic system. 



d. Marseilles morainic system. 



10. Fifth interval of recession (unnamed), shown by .shifting of ice lobes. 

 IL Late Wisconsin drift sheet, as represented in the Ohio district. 



a. The main morainic system and attendant great bowlder belts. 

 h. Mississinawa (Valparaiso I) morainic system; includes Union 

 and Mississinawa moraines of the Maumee-Miami lobe and 

 the Powell and Broadway moraines of the Scioto lobe, and 

 is a probable correlative of the Valparaiso morainic system 

 of the Lake Michigan lobe. 



c. St. Johns or Salamonie moraine. 



d. Wabash moraine. 



e. St. Marys or Fort Wayne moraine. 



/ Lake Maumee beaches and correlative moraines. 



g. Lake Whittlesey beach and correlative moraines. 



h. Lake Warren beaches and correlative moi'aines. 



i. Lake Dana beach (Lake Lundy?). 



j. Lake Ii'oquois beach. 



By reference to the glacial map, PI. II, the extent of exposure of each till 

 sheet and the distribution of the moraines and the lake beaches may be seen. 

 It will be observed that the oldest drift sheet of this region (the Kansan 

 or pre-Kansan) is exposed only in a limited area in northwestern Penn- 

 sylvania. The next younger or Illinoian drift sheet has not been recognized 

 in northwestern Pennsylvania, but it is extensively exposed in southwestern 

 Ohio, southeastern Indiana, and in the glaciated portion of Kentucky. The 

 lowan drift sheet appears not to extend beyond the limits of the Wisconsin 

 drift in the region covered by the map, but a silt deposit which appears to 



