CALL FOR PROPOSALS:

ORGANIZERS

  • Harvey Thorleifson, Chair
    Minnesota Geological Survey
  • Carrie Jennings, Vice Chair
    Minnesota Geological Survey
  • David Bush, Technical Program Chair
    University of West Georgia
  • Jim Miller, Field Trip Chair
    University of Minnesota Duluth
  • Curtis M. Hudak, Sponsorship Chair
    Foth Infrastructure & Environment, LLC

 

Paper No. 27
Presentation Time: 3:30 PM

CORRELATING PHYTOLITH AND POLLEN DATA FROM WILD RICE LAKES AND DESIGNATION OF FIRST OCCURRENCE – A CAUTIONARY NOTE


THOMPSON, Robert, Department of Anthropology, University of Minnesota, Minneapolis, MN 55455, MYRBO, Amy, LacCore/CSDCO, Department of Earth Sciences, University of Minnesota, 500 Pillsbury Dr. SE, Minneapolis, MN 55455, MISQUADACE, Shelden, Cloquet, MN 55720, PETERSON, Misty Rose, Fond du Lac Tribal and Community College, Cloquet, MN 55720, WEINGARTEN, Matthew, Salish Kootenai College, Pablo, MT 59855 and LOCATELLI, Emma Rose, Geology and Geophysics, Yale University, Kline Geology Laboratory, 210 Whitney Ave, New Haven, CT 06511, rthompso@umn.edu

Wild rice (Zizania palustris) is central to Ojibwe culture. For example, the Fond du Lac Band of Lake Superior Chippewa chose the location of their reservation in the 1854 treaty based on the presence of several wild rice lakes in this area. The manoomin project, a shared effort between the Fond du Lac band and the University of Minnesota, is studying the history of the wild rice lakes on the reservation using sediment core samples. The lakes share a basic history, having been formed in depressions left by melting of ice blocks calving off the retreating glacier. Variations in hydrology impact this history differently for each lake. Nevertheless, a basic pattern of lakes filling in gradually through the Holocene is shared by the three lakes cored in the first year of this study: Dead Fish Lake, Perch Lake and Rice Portage Lake. Each of these lakes was infilled first with organic-poor silt in the early Holocene, then later with organic rich, fine-grained sediment (diatomaceous silty sapropel) with interspersed plant macrofossils. Both phytoliths and pollen were recovered from cores taken from each of these lakes, and their respective abundance in subsample splits from the uppermost levels of the lake cores were compared. In each of the lakes, pollen, and in particular grass pollen, is abundant in the surface sediments of the lakes. While wild rice does not produce unique pollen, the abundance of grass pollen is thought to reflect the presence of wild rice. Wild rice phytoliths (in fact any phytoliths) are sparse in the surface levels, beginning to concentrate 15-20 cm below the surface. Phytoliths have a specific gravity of 2.3- 2.35, which allows them to sink further than pollen. The disjunct between grass (presumed wild rice) pollen and wild rice phytoliths demonstrates the need for caution in interpreting the correlation between phytoliths and pollen recovered from the same core horizons. In addition, the first appearance of wild rice phytoliths in the sedimentary record may predate the first appearance of wild rice plants in the lake.
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