PLEISTOCENE HISTORY OF LOWER WISCONSIN RIVER 68i 



2. Sloping gently westward from the moraine north of the river 

 a sandy outwash plain extends to an irregular boundary against 

 the sandstone hills of the country rock. The western edge is irreg- 

 ular, for the fluvio-glacial material is found up the valleys of Honey 

 and Otter creeks. Of special interest are the erratics found in 

 the south branch of Honey Creek as far west as Blackhawk and 

 Plain. They He on an upper terrace, corresponding in elevation 

 to that of the outwash plain across the mouth of the creek at its 

 eastern end. This position, 17 miles beyond the terminal moraine, 

 impHes that the bowlders were carried to their positions while 

 frozen in blocks of ice floating on a lake. 



Such a lake may have been formed in one of two ways: 



a) The edge of the ice may have extended beyond the terminal 

 moraine and dammed the mouth of Honey Creek. No evidence 

 was found to substantiate this possibiHty. 



b) As the outwash plain was being built, the glacial waters 

 issuing from the ice-front between Prairie du Sac and the South 

 Range swept their load southward across the mouth of Honey 

 Creek. Outwash material may thus have dammed the mouth of 

 Honey Creek, forming a lake upon which icebergs may have floated 

 the bowlders. While this suggestion involves the difficulty of 

 getting the bergs swept across the outwash plain and into the lake, 

 it still seems the more probable of the two. 



3. The valley train, now represented by terrace remnants, once 

 filled the bottom of the valley from the terminal moraine to the 

 Mississippi River. It was 90 feet above the present flood-plain 

 near the terminal moraine, 30 feet in mid-course, and 40 feet at 

 the western end of the valley. As this outwash deposit was grow- 

 ing, the glacial waters constantly deposited material across the 

 mouths of the tributary valleys, causing them in turn to aggrade 

 their channels. Terrace remnants of these slack-water deposits are 

 to be seen in most of the tributary valleys, serving to project the 

 level of the valley train even where it has been removed from the 

 main valley by subsequent erosion. 



The most easterly remnant of the original valley train lies near 

 Mazomanie at the mouth of Black Earth Creek. It is an irregular 

 area a mile wide by 6 miles long, separated from the south bluffs 



