THE KANSAN ICE INVASION 263 



more, 62 and Winona 63 counties are probably referable to the Aftonian as they 

 he under what is now believed to be Kansan drift. The area of the Iowan till 

 is not definitely known. Near Moscow, Freeborn County, at depths of 35 and 

 50 feet below the surface, sticks, apparently of tamarack, occur in gravel and 

 clay associated with the remains of crayfish and gastropod shells. In a well 

 a log (tamarack?) was found 20 feet below the surface which had been gnawed 

 by beavers (possibly Castoroides). Peat moss and sticks were associated with 

 the gnawed wood. At Manchester a bed of muck was found 70 feet below 

 the surface. 64 



In Martin County, which is covered with the Wisconsin drift, several 

 horizons of shell beds have been reported. At Center Creek 65 a sand bed 8 feet 

 thick underlies 60 feet of till. This sand bed contained " elm e res and clam 

 shells in abundance, the latter 3-4 inches long. " Well diggers report shells in 

 coarse, dark sand at depths of 20 to 60 feet below the surface, under yellow 

 and then blue till. Gastropod shells have been reported 6 feet below the sur- 

 face, underlaid and overlaid by yellow till. Some of these references doubt- 

 less include the Yarmouth beneath Iowan till but the shallower shell beds are 

 evidently Peorian. 



In Brown and Redwood counties shells and vegetation 66 are reported 

 between till sheets. In Lyon County 67 gastropod and bivalve shells are re- 

 ported in sand and gravel from 8 to 26^2 feet below the surface. In Lac qui 

 Parle County 68 wood was found at a depth of 52 feet. In Hennepin County 69 

 the remains of wood have been observed at various places between tills. In a 

 well 25 feet above Red River an abundance of the remains of marshes and 

 sedges was found at a depth of 45 feet. To just what interval this deposit 

 should be assigned is not clear; it may be Yarmouth or it may be Aftonian. 

 It could scarcely be post- Wisconsin. 70 



Shell deposits occur in Blue Earth County, on Blue Earth River near the 

 Minnesota River. A section published by Owen 71 may be interpreted as 

 follows: 



1. Ash-colored clay (Wisconsin) 8 feet 



2. Coarse sand with some pebbles (Wisconsin) 2 " 



3. Ash-colored clay marl (Wisconsin) 7 " 



"Op. cit., I, p. 312. 



• a Op. cit., I, p. 264. 



M Op. cit., I, p. 390. 



■ Op. cit., I, pp. 486-487. 



■ Geol. Minn., Final Rep., 1, p. 580. 

 " Op. cit., 1, pp. 608-609. 



" Op. cit., 1, p. 630. 



-Op. cit., I, p. 306. 



n Op. cit., 11, p. 529. 



71 Rep. Geol. Surv. Wis. Iowa and Minn., p. 489. 



