22 ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 496 



eastern side of the southern basin and at only 6 cm in the center of the southern 

 basin of the lake. Man-made pollution, measured by the concentrations of trace 

 elements such as lead, increases upward in the sediments cored. The increase in 

 trace-element concentration towards the surface takes place within the same depth 

 intervals as the Ambrosia increase. Therefore, both the Ambrosia increase and 

 the trace-element concentration increase in the upper few centimeters of Lake 

 Michigan sediments can be related to man's activities since 1840 A.D. 



ACKNOWLEDGMENTS 



We appreciate the valuable assistance of Captain Richard Thibault and the 

 crew of the R. V. Inland Seas and of the Universityof Michigan Great Lakes Re- 

 search Division, which operated the ship under the sponsorship of the National 

 Science Foundation. Alan Jacobs assisted with the coring and sampling; Rose 

 Duffield and Kent Robinson helped with the laboratory preparation of the pollen 

 samples. We wish to acknowledge Louis J. Maher, F. B. King, and J. Johnson 

 for critically reviewing the manuscript. This work was supported in part by 

 National Science Foundation grant GB-24710 to James E. King. 



REFERENCES 



Adam, D. P., 1967, Late-Pleistocene and Recent palynology in the central Sierra Nevada, Cali- 

 fornia, _in Cushing, E. J., and H. E. Wright, Jr., eds., Quaternary Paleoecology . New 

 Haven, Conn.: Yale University Press, p. 275-301. 



Anderson, T. W., and J. Terasmae, 1966, Palynological study of bottom sediments in Georgian 

 Bay, Lake Huron: Proceedings of Ninth Conference on Great Lakes Research, Chicago, 

 1966: University of Michigan Great Lakes Research Division Publication 15 , p. 164-168. 



Benninghoff, W. S., 1962, Calculation of pollen and spore density in sediments by addition of 

 exotic pollen in known quantities: Pollen et Spores, v. 4, no. 2 , p. 332-333. 



Braun, E. L. , 1950, Deciduous forests of eastern North America. New York: Hafner Publishing 

 Company, 596 p. 



Bruland, K. W., Minoru Koide, Carl Bower, L. J. Maher, and E. D. Goldberg, 1975, Lead-210 and 

 pollen geochronologies on Lake Superior sediments: Quaternary Research, v. 5, no. 1, 

 p. 89-98. 



Creer, K. M., D. L. Gross, and J. A. Lineback, 1976, Origin of regional geomagnetic variations 

 recorded by Wisconsinan and Holocene sediments from Lake Michigan, U.S.A., and Lake 

 Windermere, England: Geological Society of America Bulletin, v. 87, no. 4, p. 531-5 1 +0. 



Cushing, E. J., 1965, Problems in the Quaternary phytogeography of the Great Lakes Region, _in 



Wright, H. E., Jr., and D. G. Frey, eds., The Quaternary of the United States. Prince- 

 ton, N. J.: Princeton University Press, p. 403-416. 



Davis, M. B., L. B. Brubaker, and J. M. Beiswenger, 1971, Pollen grains in lake sediments: 

 Pollen percentages in surface sediments in southern Michigan: Quaternary Research, 

 v. 1, no. 4, p. 150-467. 



Denton, G. H. , and S. C. Porter, 1970, Neoglaciation: Scientific American, v . 222 , no . 6, p . 101- 1 10. 



Edgington, D. N., and J. A. Robbins, 1976 , Records of lead deposition in Lake Michigan sediments 

 since 1800: Environmental Science and Technology, v. 10, no. 3, p. 266-274. 



Elsik, W. C, 1971, Microbial degradation of sporopollenin, _in Brooks, J., P. R. Grant, M. D. 

 Muir, P. Van Gijel, and G. Shaw, eds., Sporopollenin. London: Academic Press, 

 p. 480-511. 



Federal Water Pollution Control Administration, 1967, Lake currents: Water quality investi- 

 gations, Lake Michigan Basin. Chicago: FWPCA Great Lakes Region, 364 p. 



