238 LIFE OF THE PLEISTOCENE 



7. Minnesota 



It is not definitely known how far north the Aftonian deposits extend, but 

 it is believed that they are represented in the southern part of Minnesota. 



Chamberlin 81 has correlated with the Aftonian certain peaty deposits in the 

 basin of Lake Agassiz, together with other peat beds between the two till 

 sheets in southern Minnesota, described by Winchell. At this time, however, 

 the pre-Kansan or Nebraskan till sheet was but little known, and the Aftonian 

 was placed above the Kansan. The recognition of the Aftonian as an interval 

 between the Kansan and the Nebraskan, places some of these deposits from 

 Minnesota above the Kansan, and hence correlates them with the Yarmouth 

 Interglacial stage. A number of Minnesota records, however, appear to be 

 referable to the Aftonian interval. 



In Wilkin County, 82 at Mitchell, a well record gave the following section: 



Soil 2 feet. 



Yellowish-gray till 6 " 



Gray sand : Yi " 



Dark bluish till 18 



Sandy black mud x " 



The sandy black mud contained many small gastropod shells. The dark 

 blue till is evidently Kansan and the shells are referable therefore to the Afton- 

 ian interval. 



In McLeod County, a number of wells encountered mollusks at various 

 depths. 83 A boring from the Stewart railroad well descended to a considerable 

 depth, as noted below: 



Yellowish till 20 feet 



Dark bluish till 240 feet 



Sand with gravel 5 feet 



Height of section 265 feet 



' At 100 feet, in a thin muddy layer, shells were found, and at 110 feet more 

 shells. At 177 feet the trunk of a tree was encountered. In the sand and 

 gravel at the bottom a number of fragments of bones were found. The dark 

 bluish till includes both Wisconsin and Kansan till, and the shells at 100 and 

 110 feet are evidently referable to the Yarmouth interval. The bones in the 

 gravel at the bottom are possibly Aftonian. 



In Cottonwood County gastropod shells and wood have been found 60 

 feet below the surface at Windom, and in Jackson County 84 wood and small 



81 Journ. Geol., Ill, pp. 272-273, 1895. 

 » 2 Geol. Min., Final Rep., II, p. 529. 

 "Op.cil., pp. 186-187. 

 »* Op. cit., I, p. 511. 



