360 HALL AND SARDESON — EOLIAN DEPOSITS OF MINNESOTA 



by their superjacent position 

 which also determines their 

 relative age. Their relation 

 to fluviatile post - Glacial 

 deposits is that of a con- 

 temporary. At Minneapo- 

 lis the fossiliferous gravel, 

 stratified sand, and marsh 

 peat of an ancient Missis- 

 sippi River channel were 

 formed contemporaneously 

 with the lag gravels and 

 dune sands lying on the 

 terrace which was the bank 

 of the river prior to the 

 time when Saint Anthony 

 falls were situated one and 

 one-half miles below their 

 present position. The rela- 

 tion of the eolian deposits to 

 the fluviatile and these in 

 turn to the glacial drift is 

 evidence that the river's 

 domain at that time was 

 within a channel, and, fur- 

 ther, that the earlier formed 

 terraces were neither a lake 

 accumulation nor a glacial 

 river product. Incidentall}^ 

 the accompanying section 

 (figure 2) shows that the 

 Mississippi river has done 

 an amount of work in addi- 

 tion to the cutting of the 

 gorge in which it now flows, 

 on which cutting estimates 

 of the length of post-Glacial 

 time as determined by the 

 Mississippi river are often 

 based. 



