86 LIFE OF THE PLEISTOCENE 



Elephas primigenius (or columbi?) 



Lake County, Indiana 6 " 



Haas' gravel pit, Oak Park 52 

 Elephas columbi 



Chicago Heights, in creek bank, 18 or 20 feet below surface, in Wallace Creek. 63 

 Odocoileus irirginianus 



Toleston beach, Evanston. Pelvic bones. 54 



Toleston beach, Evanston. Femur. 55 



E. THE SAG LOW WATER STAGE 56 



(Kirkfield Stage of Lake Algonquin) 



Previous to the Toleston stage the glacial lakes consisted of local bodies of 

 water, which grew in size as the ice melted. Thus we have lakes Upham and 

 Duluth in the Superior basin; lakes Maumee, Saginaw, Arkona, Wayne Whit- 

 tlesey, Warren, and Lundy in the Huron-Erie basin; and Lake Chicago in 

 the Michigan basin. During the formation of these lakes the outlet was mostly 

 by way of Chicago to the Gulf of Mexico. Lake Erie began as a small body of 

 water in the eastern end of the Erie basin its outlet being into Lake Iroquois 

 (in the Ontario basin) which emptied into the Atlantic Ocean via the Mohawk 

 and Hudson rivers. 



The ice sheet gradually withdrew farther toward the northeast, causing the 

 Superior, Huron, and Michigan basins to unite and form a single body of 

 water known as Lake Algonquin. During the life of Lake Iroquois the ice 

 uncovered the Trent Valley in Ontario which provided a lower outlet for the 

 waters of Lake Algonquin, which flowed thru this valley past Kirkfield into 

 Lake Iroquois. This change of outlet at first caused a lowering of the water 

 in the Chicago region, in many localities a land surface appearing. This con- 

 dition is attested by the oxidized character of some of the silt beds above the 

 Unio deposit and also by the presence of peat deposits. Uplift in the region 

 of the Trent outlet eventually brot the lake up to a level high enough to dis- 

 charge again thru the Chicago and St. Clair outlets. The water in the 

 Chicago basin probably was raised to the Toleston level (20 feet), forming the 

 Hammond stage. 57 



62 Leverett, 1897, p. 71. 



53 Collected by Mr. James H. Knapp. 



54 Higley and Raddin, p. XIV. 



65 Leverett, 1888, p. 188. 



66 It seems desirable that the different stages of Lake Chicago and its successors should 

 receive local names, even when the stage is a part of the Great Lake system, for the conven- 

 ience of students of postglacial life. As this low water stage is shown to the best advantage 

 in the beds of the old Sag outlet, this name is here suggested. See footnote under Hammond 

 stage. 



67 This height is given by Leverett (12th An. Rep. Mich. Acad. Sci., p. 36). Goldthwait 

 (Bull. 111. Geol. Surv. VII, p. 64; XI, p. 56) refers the Algonquin level to the 12-14 foot 

 beaches. The evidence in the north shore channel and elsewhere is in favor of the 20 feet 

 return, as suggested by Leverett. 



