EOLIAL OR WIND-LAID DEPOSITS 



63 



rainfall which caused floods that completely covered the flood plains. 

 These periods of alluviation were followed by those in which the 

 rivers contracted to their ordinary channels and left the sediment 



Fid. 61. Calcium carbonate concretions (Lueaa Kindchen), from the loens of Illinois. 



Fia.62. A roud through a deposit of deep loess along the lower Illinois River. The deposit 

 is 30 to 50 feet deep. The vertical walls are characteristic. 



