16 ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 496 



LAKE MICHIGAN CORE 969-2A 



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Fig. 6 



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 Percent 



Diagram of percentages of pollen for Lake Michigan core 969-2A. 

 200 fossil pollen grains were counted from each sample. 



(ISGS-219) radiocarbon years B.P. (fig. 8). Seven samples from core 800-5, 

 taken near core 1001-3A, were dated at about 2000 radiocarbon years B.P. at the 

 surface and at more than 7000 radiocarbon years at the 1 -meter level (fig. 9) 

 (Gross, Coleman, and Lineback, 1973). These misleading radiocarbon dates re- 

 sult from the low indigenous organic carbon content of the sediment (1% to 3%) 

 and from the likelihood that much of the carbon present is detrital material derived 

 from erosion of the Woodfordian tills around the lake. If the percentage of older 



