A multi-proxy palaeoecological and palaeoclimatic record within full glacial lacustrine deposits, western Tennessee, USA

David A. Grimley, Daniel Larsen, Samantha W. Kaplan, Catherine H. Yansa, B. Brandon Curry, and Eric A. Oches

    The Fulton Section, along the Mississippi River in western Tennessee, USA, is a 1 km continuous exposure (
20m vertically) of Quaternary fluvial and lacustrine deposits, inset within Eocene sediments and buried by thick loess. Fossiliferous slackwater lake sediments record maximum aggradation during the last two major glaciations, with deposition between ca. 190140 ka andQ1 24 18 14C ka BP, based on amino acid and radiocarbon chronology, respectively. During the onset of full glacial conditions (ca. 2422 14C ka BP), a relatively permanent shallow lake environment is indicated by ostracodes, aquatic molluscs, and both pollen and macrofossils of aquatic plants. By 21.8 14C ka BP, increasing emergent plants, amphibious gastropods (Pomatiopsis) and heavier d18O compositions suggest marsh-like conditions in a periodically drying lake. The surrounding uplands consisted of PiceaPinus woodlands mixed with cool-temperate hardwoods (e.g. Quercus, Populus, Carya), grasses and herbs. More open conditions ensued ca. 20 14C ka BP, with loess and slopewash gradually infilling the former lake by 18 14C ka BP. Modern analogue analyses of ostracodes and palaeontological evidence imply a full glacial climate similar to todays mixed-boreal zone in central Minnesota, USA, about 98C cooler in mean annual temperature than present-day western Tennessee.