Problems, Middle Mississippi River Region, Pleistocene Time 229 
Inter-glacial Glacial 
Today 
Recent 
Years ago Wisconsin 
Peorian 
Iowan 
100,000 
Sangamon 
Illinoian 
200,000 
300,000 
Yarmouth 
400,00 
Kansan 
500,000 
Aftonian 
600,000 
a 
700,000 Nebraskan 
rae Ga oe Acne 
TABLE VII. 
Time scale of the Pleistocene modified from estima tes hy George F. Kay. 
