126 IOWA ACADEMY OF SCIENCES. 



The topographic features of an area across the middle 

 portion of this lobe are bolder. The tops of the hills stand, 

 in many places, forty to fifty feet above the valleys. The 

 contours are quite sharp and the slopes are steep. The 

 irregular character of these sand or loess capped hills 

 resembles very closely the ridges which are found around 

 the margin of the lowan drift plain. Even here, however, 

 the stream channels, choked and clogged with aqueo-gla- 

 cial debris, the occurrence of lowan drift near the base of 

 the hills, and the presence of large, light-colored granite 

 bowlders along the valleys bear indubitable testimony to 

 the former presence of the lov^^an ice sheet. The axes of 

 these hills are composed of Kansan drift, but their tops are 

 usually crowned with sand or with loess, often to a depth 

 of fifteen to thirty feet. A short distance south of the 

 Monticello church, in section 33 of Howard township, the 

 road has been cut through a bank of loess exposing a 

 depth of about fifteen feet while in the valley a short dis- 

 tance away there may be seen a bed of lowan drift. The 

 loess at this place is very fossiliferous, containing numer- 

 ous individuals of species of Polygyra, Succinea, Zonites 

 and Pupa. Examples of sand covered hills over this area 

 are numerous, but typical places have been already cited. 



The peculiar topography of the Toledo lobe, the pres- 

 ence of loess overlying the lowan drift, together with the 

 very scant amount of material that the lowan ice sheet 

 left over its surface would seem to indicate an unusual 

 episode in the history of the lowan ice action. The phe- 

 nomena which it presents lend themselves to the following 

 interpretation. During the early stages of the extension 

 of the lowan glacier a narrow lobe of ice was pushed south- 

 ward beyond the main body over the deeply eroded Kan- 

 san surface, covering the area outlined as the Toledo lobe. 

 For some reason the pressure from behind soon became 

 insufficient to keep up the movement over this lobe, and 

 the ice which covered the region became dead and gradu- 

 ally melted where it came to rest. As the glacier moved 

 slowly over the old Kansan surface, the stones which were 

 held fast along the bottom of the ice would form instru- 



