PLEISTOCENE HISTORY OF LOWER WISCONSIN RIVER 685 



the high terrace is older than the terminal moraine and outwash of 

 the low terrace, was not verified. For cuts on and directly west of 

 the moraine show about the same amount of leaching as do the 

 exposures farther west on the high fill. 



vi) The high terrace marks a time of great filling, while the 

 low one is much less important in this respect. Evidence from 

 other regions has led to the generalization that the ice of the late 

 Wisconsin substage was the most energetic of all the ice advances, 

 building higher and more rugged moraines; eroding more deeply 

 and more conspicuously; dumping more sedunent into the drainage 

 lines leading away from the ice-front, and so building larger valley 

 trains. This hne of evidence would point rather to the late Wisconsin 

 than the early Wisconsin substage as the builder of the high terrace. 



vii) Since erratics in Honey Creek Valley rest only on the high 

 Wisconsin terrace, it seems clear that a glacial lake stood in this 

 valley during at least part of the time when the slack-water fill of 

 which these terraces are remnants was being deposited. It would be 

 inferred that the lake was dammed during the maximum extent of 

 the ice, rather than when the ice-edge stood farther east, as it did 

 in early Wisconsin time if the early Wisconsin ice affected this 

 immediate region. This piece of evidence suggests that the high 

 Wisconsin fill in Honey Creek Valley was deposited when the ice- 

 front stood at least as far west as Prairie du Sac. 



The weight of this evidence is seriously against the possibility 

 that the low terrace was deposited as a valley train of the late 

 Wisconsin invasion. 



h) When the ice-front of the Green Bay lobe had withdrawn east 

 of the Portage divide, the ice-dammed lake, Jean Nicolet,^ was 

 formed with its outlet down the Wisconsin Valley. These outlet 

 waters were clear, and probably cut the upper part of the valley 

 train down to the level of the low terrace. Evidence that the low 

 terrace was cut by waters from Lake Jean Nicolet follows. 



i) The uniform height, 12 to 15 feet, of the terrace above the 

 flood-plain all the way from the terminal moraine to the mouth of 

 the valley, suggests strongly an erosional rather than a depositional 

 origin. 



' W. Upham, Amer. Geologist, Vol. XXXII (1903). P- 33°- 



