THE PLEISTOCENE HISTORY OF THE LOWER 

 WISCONSIN RIVERA 



PAUL MacCLINTOCK 

 University of Chicago 



INTRODUCTION 



The Wisconsin River, rising among the glacial lakes in the 

 northern part of the state of Wisconsin, flows almost due south 

 nearly to Portage, where it turns and flowing westward for a dis- 

 tance of about 80 miles joins the Mississippi just south of Prairie 

 du Chien (Fig. i). It is this lower, east- west part of the river 

 valley which is discussed in this paper. The terminal moraine of 

 the Wisconsin glacial epoch crosses the valley just east of Prairie 

 du Sac and marks not only the eastern boundary of the region here 

 considered but also that of the drif tless area. Since glacial drift is 

 found in Iowa opposite the lower end of the valley, it may be said 

 that the Wisconsin River traverses from east to west the entire 

 driftless area. It is thus seen that drift remnants which are found 

 in this part of the valley are of important significance in the history 

 of ancient ice invasions in bordering regions. 



These remnants of glacial drift in the valley fall naturally into 

 two divisions: First, there are terraces of Wisconsin age: (a) 

 remnants of the valley train sloping from the terminal moraine, 

 where it crosses the valley near Prairie du Sac, to the Mississippi 

 River, and (b) a lower terrace standing only 15 feet above the pres- 

 ent river flood-plain; and second, standing well above the preced- 

 ing terrace, are rock benches covered with much older drift. These 

 upper benches have a gentle slope toward the east (Fig. 2) . 



PART I. OLDER DRIFT 



Stated in the simplest terms, there are six areas of the older 

 drift: (i) near Lone Rock, (2) near Muscoda, (3) from Muscoda 

 to Boscobel, (4) from Boydtown to the Kickapoo River, (5) at 



' Condensed from Ph.D. thesis submitted to the Department of Geology, the 

 University of Chicago, 1920. 



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