342 LIFE OF THE PLEISTOCENE 



IV. SlJMMAR\ 



Deposits referable to the Sangamon Interglacial interval extend from Iowa 

 thru southern Illinois, Indiana and Ohio to New York. Northward they have 

 been recognized at Toronto, Canada, and near James Bay, as well as in Minne- 

 sota, Wisconsin and Michigan. It was an interval, therefore, of wide extent 

 and also, probably, of long duration. The soil horizons and the peat deposits 

 as well as the amount of erosion bear evidences of a long period of exposure to 

 the air. The old forest beds are the most extensive of any interglacial interval, 

 and are widely scattered, being especially well preserved in Iowa, Illinois, 

 Indiana, Ohio, Wisconsin and Ontario. 



The climate varied as was the case in the Yarmouth interval, there being 

 evidences (especially at Toronto) of a warm, a temperate and a cold climate. 

 Loess deposits were formed on the Sangamon soils and cover a wide extent of 

 territory along the Mississippi, Illinois, Ohio and other valleys, indicating a 

 period of dry, windy conditions. Land mollusks were abundant, as in the 

 post-Kansan loess. 



A large lake was present in the Ontario basin, comparable in size (probably) 

 to the Lake Ontario of today. Coleman thus summarizes the lake conditions 

 in the Ontario region: "Reviewing the old water levels of the Ontario basin 

 . . . , we find that the records commence with the Toronto formation at the 

 middle of an inter-glacial period, and that the succession may be represented 

 in the following table: 



(1) Don Stage, warm climate, fresh-water shells, dammed by differential 

 elevation toward the northeast to about 60 feet above present lake. Succes- 

 sor to Laurentian River enters north of Toronto. 



(2) Scarboro stage, cold temperate climate, fresh-water shells, deposit 

 conformable with those of last level, but reach 145 feet, and consist of delta 

 materials of Laurentian River. 



(3) Low water stage, with subaerial erosion and cutting of river valley 

 to a depth below present lake level. 



(4) High water stage, glacial or sub-glacial climate, probably fresh-water 

 shells, ice-dammed to a height of at least 320 feet. " 



That the other lake basins were also filled with water is rendered certain 

 < by analogy, because the naiad fauna at Toronto must have migrated thence 

 from the Mississippi Valley and this could only have been accomplished by 

 way of an interglacial Chicago or Fort Wayne outlet. Evidently there were 

 ,lakes comparable to the postglacial Chicago, Whittlesey, Warren, Iroquois, 

 etc., long prior to the great waters which have left the evidences of their exist- 

 ence in the old shore lines surrounding the present Great Lakes. 



