PLEISTOCENE HISTORY OF LOWER WISCONSIN RIVER 675 



Wauzeka, (6) at Bridgeport. The first four of these are similar 

 in topography, constitution, and amount of weathering, while the 

 last two differ from the others in that they contain not only much 

 striated material (at Bridgeport) but also a large percentage of 

 calcareous material. 



I. SUBDIVISION 



It appears from the evidence that the older drift is not all of the 

 same origin or age. 



a) A lithologic study of some 300 characteristic rock specimens 

 collected from the different exposures, and examined in the labora- 

 tory, shows 37 common to Wauzeka and Bridgeport, 17 common to 



! I i 1 



3 ^ X -J 



' I ■ ■ ' I i' ■' 



''■''" 



OUt- 7«ra«i 



High H^ltconiln TerracM 



— — Low iVltcon3ln Terract 



Fig. 2. — Profile of the Wisconsin River Valley from Prairie du Sac to Prairie 

 du Chien showing the bedrock, the drift partly filling the valley, and the levels of 

 the three terraces. 



Orion (Port Andrew) and the nearest IlHnoian drift at Verona, 

 9 miles southwest of Madison, 27 common to Orion and Wauzeka, 

 and 25 common to Bridgeport and Iowa (near McGregor). These 

 facts show that there is close similarity between the drifts of Illi- 

 noian age and that at Orion on the one hand, and between the 

 drift at Wauzeka, Bridgeport, and Iowa on the other. 



b) The drift at Wauzeka and Bridgeport contains much Lime- 

 stone and dolomite, while farther up the valley there is neither. 

 Since the IlHnoian and pre-Ilhnoian drifts east of the region contain 

 calcareous material, it is likely that these terrace deposits in the 

 mid-course of the valley originally contained the carbonates which 

 have been subsequently leached. 



