THE LIFE OF GLACIAL LAKE CHICAGO 75 



front; one at Milwaukee (correlative with the Port Huron-Whitehall moraine) 

 and one at Two Rivers, Wisconsin (believed to represent the Manistee moraine). 



During one of these retreats the ice may have opened an outlet north of 

 the Green Bay Valley which caused a lowering of the lake level. Writing of 

 the changes in the Michigan basin, Taylor says, 20 "Bordering the west shore 

 of Lake Michigan and extending into the Green Bay — Lake Winnebago trough 

 and the Fox and Wolf River valleys is an extensive deposit of red clay, partly 

 laminated, partly pebbly and massive, which was described by Chamberlin 

 in his Geology of Eastern Wisconsin. Later study of this deposit by Alden, 

 under the direction of Chamberlin, shows that the larger part of this deposit, 

 the massive pebbly clay, is to be interpreted as glacial till which was laid down 

 during a readvance of the glacier in the Lake Michigan basin as far south as 

 Milwaukee and of the Green Bay lobe in the Green Bay-Lake Winnebago 

 trough to a point south of Fond du Lac, Wis. The ice also crowded west- 

 ward in the Fox and Wolf River valleys. The red silt composing the laminated 

 clay and the matrix of the massive pebbly clay is thought to have come from 

 the Lake Superior region, being brought into the Green Bay and Lake Michigan 

 basins by the opening of a southward outlet southeast of Marquette. The 

 first opening of this outlet must have been at or near the climax of the stadial 

 retreat immediately before the readvance to the first red till moraine. The 

 phenomena indicate a readvance over a relatively wide interval, and it seems 

 certain that if a lower outlet had been opened by the retreat, it was closed 

 again by the readvance and the level of the glacial waters in the western half 

 of the Lake Superior basin were raised again to the level of some earlier, higher 

 outlet. Perhaps this accounts for the faintness of some of the beaches im- 

 mediately above the Algonquin beach in the Lake Superior basin; they may 

 have been submerged and obliterated after they were made. " These fluctua- 

 tions may have affected the level of Lake Chicago. Professor Upham 21 be- 

 lieves that Lake Chicago flowed thru a glacial lake which he calls Lake Jean 

 Nicolet (via the Wisconsin River to the Mississippi River) during this low 

 water stage, and that the Green Bay region has been uplifted since that time. 

 This opinion seems untenable because the divide at Portage is too high (797 

 feet above sea level) for an overflow at the Bowmanville stage (590 feet). 



Just what relation the Bowmanville stage may bear to glacial Lake Wayne 

 of the Huron-Erie-Ontario basins can only be surmised. This lake followed 

 Lake Whittlesey, the waters falling 80 or 85 feet. This drop in level was due 

 to further retreat of the ice, which uncovered an opening along the ice front 

 near Syracuse, into the Mohawk Valley. Taylor says, 22 " When the Huron-Erie 



28 Smith. Report, 1912, p. 313. 



21 Amer. Geol., XXXH, pp. 105-115; 330-331, 1903. 



23 Smith. Rep., 1912, p. 313; also 305-306. 



