THE NEBRASKAN ICE INVASION 239 



gastropod shells are reported from a depth of 100 feet. The great depths of 

 these deposits indicate that they underlie the Kansan drift and are therefore 

 referable to the Aftonian interval. The records from Murray, 85 ' Nobles, 86 and 

 Rock counties" also apparently belong to the same horizon. From the last, at 

 Luverne, clam shells and wood are reported from a depth of 81 feet. Red 

 cedar and tamarack occur in these strata. It is also extremely probable that 

 the old soils reported from Olmsted, s7 Filmore, and Winona counties should be 

 referred to the Aftonian stage. 



8. Wisconsin 



Few evidences of Aftonian life have been observed from this state. An old, 

 pre-Kansan drift has been recorded by Wiedman 88 who describes it as "a very 

 old, thin drift." Koehler 831 describes an old forest bed 4 to 12 inches thick, 

 near Woodville, St. Croix Co., which appears to be referable to the Aftonian 

 interval. The wood was identified as spruce. The order of strata was as 

 follows: 



Illinoian drift 



Weathered soil 



Kansan drift 



Old torest bed 



Pre-Kansan drift 



9. Illinois 



In Illinois, Aftonian deposits are apparently indicated in several places. 

 At Bloomington, McLean County, a well section passes thru many deposits, 

 showing the Aftonian at the base. 89 



1. Surface soil and brown clay (Wisconsin 10 feet. 



2. Blue clay (Wisconsin) 40 " 



3. Gravelly hard pan (Wisconsin) 60 " 



4. Black mold with pieces of wood (Sangamon) 13 " 



5. Hardpan and clay (Illinoian) 89 " 



6. Black mold (Yarmouth) 6 " 



7. Blue clay (Kansan) 34 " 



8. Sand, buff and drab, with fossil shells (Aftonian) 2 " 



Height of section 252 " 



Bannister 90 records Helicina occulta from No. 8 and suggests that the 

 deposit may be loess. 



85 Op. cit., I, p. 529. 

 "Op. cit., p. 530. 



87 Op. cit., p. 553; 264; 312. 



88 Science, N. S., XXXVII, No. 951. p. 457, 1913. 

 8,a American Forestry, XXII, pp. 92-93, 1916. 



,9 Leverett, Illinois Glacial Lobe, p. 108. 

 9 °Geol. Illinois, IV, p. 178. 



