HOLOCENE PALYNOLOGY AND S E DI M E N T O LO G Y 



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Pollen concentration 

 grains/g dry wt. 



X 1000 

 20 40 60 80 100 



Scale change 

 20 



Core collected at 42° 18.0' N. , 86°42 .0' W. from 73 .4 meters of water, 

 (see text) . 200 fossil pollen grains were counted from each sample. 



number of arboreal pollen grains. At the same time, land disturbance in the re- 

 maining areas has continued to increase and has produced the steady rise in rag- 

 weed pollen shown in the diagrams. 



Chi-square tests on adjacent pairs of samples identified significant dif- 

 ferences (.95 confidence level) in pollen percentages between the 13-cm and 14- 

 cm samples and between the 75-cm and 80-cm samples. These depths are those 

 previously assigned as the boundaries between zones 3 and 4a, and zones 2 and 

 3, respectively. As zone 4b is distinguished primarily by increasing pollen con- 

 centration, it was not identified by the x 2 tests. 



