Mid-Wisconsinan environments on the eastern Great Plains |
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| Authors: | RG Baker EA Bettis RD Mandel JA Dorale GG Fredlund |
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| Institution: | 1. Littoral, Environnement et SociétéS (LIENSs), Université de La Rochelle, UMR 7266 CNRS-ULR, 2 rue Olympe de Gouges, 17000 La Rochelle Cedex, France;2. Université de Caen Basse-Normandie, FRE3484 BioMEA CNRS, Esplanade de la Paix, 14032 Caen, France;3. IFREMER, Dyneco, Laboratoire Pelagos, BP70, 29280 Plouzané, France;1. Quaternary Surveys, 26 Thornhill Ave, Thornhill, Ontario L4J1J4, Canada;2. Department of Geography, York University, N. York, Ontario M3J 1P3, Canada;3. Camosun College, Department of Chemistry and Geoscience, Camosun College Lansdowne Campus, 3100 Foul Bay Rd., Victoria, British Columbia V8P 5J2, Canada;4. University of Lethbridge, Department of Geography, Lethbridge, Alberta T1K 3M4, Canada;5. Medical Physics and Applied Radiation Sciences, McMaster University, Hamilton, Ontario L8S 4K1, Canada,;6. Department of Anthropology, McMaster University, Hamilton, Ontario L8S 4K1, Canada;7. University of Lisbon, Department of Geology, Lisbon, Portugal;8. Department of Geography, Dundee University, Dundee, Scotland, UK |
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| Abstract: | Few sites on the eastern Great Plains contain paleobotanical records for the mid-Wisconsin. We report on four sites, two stream cutbanks and two quarry exposures, ranging in age from >50 to ～23.4 ka. The oldest site at >50 ka contains a suite of macrofossils from prairie and disturbed ground habitats, with no representation of trees, indicating an open prairie. By ～38 ka the assemblages include aquatic, wetland, mudflat, and prairie elements with rare specimens of Populus, Betula cf. papyrifera, Salix and at the most northerly site, Picea. This assemblage suggests a prairie/parkland with interspersed marshes, cooler temperatures and increased moisture. Populus and Salix continued to be represented from ～36 to ～29 ka, but the only other taxon was Carex. A hiatus may be present at some time during this interval. After ～29 ka, Picea became dominant on the uplands and it was joined by sedges in local wetlands. At sites near riverine loess sources, loess accumulation began to fill in the wetlands and organic deposition ceased some time after 29 ka. |
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