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

Abstract

2009. A multi-proxy palaeoecological and palaeoclimatic record within full glacial lacustrine deposits, western Tennessee, USA.ABSTRACT: The Fulton Section, along the Mississippi River in western Tennessee, USA, is a 1 km continuous exposure ($20 m 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. 190-140 ka and 24-18 14 C ka BP, based on amino acid and radiocarbon chronology, respectively. During the onset of full glacial conditions (ca. 24-22 14 C ka BP), a relatively permanent shallow lake environment is indicated by ostracods, aquatic molluscs, and both pollen and macrofossils of aquatic plants. By 21.8 14 C ka BP, increasing emergent plants, amphibious gastropods (Pomatiopsis) and heavier d 18 O compositions suggest marsh-like conditions in a periodically drying lake. The surrounding uplands consisted of Picea-Pinus woodlands mixed with cool-temperate hardwoods (e.g. Quercus, Populus, Carya), grasses and herbs. More open conditions ensued ca. 20 14 C ka BP, with loess and slopewash gradually infilling the former lake by 18 14 C ka BP. Modern analogue analyses of ostracods and palaeontological evidence imply a full glacial climate similar to today's mixed-boreal zone in central Minnesota, USA, about 98C cooler in mean annual temperature than present-day western Tennessee.

Synthesis on Quaternary aeolian research in the unglaciated eastern United States

“…LMV. Delcourt et al (1980), Grimley et al (2009) provide paleoecologic, stratigraphic, and age data for sites between $35°a nd 38°N in western TN (a and o on Fig. 21) and the Great Lakes region of southern IL and northwestern KY (Yansa and Adams, 2012).…”

Natural and human-induced prehistoric and historical soil erosion and landscape development in Southwestern Tennessee, USA

“…It is not known when the first erosional incisions cut into the loess cover. It is likely that the first loess deposits and underlying sands and gravels were already incised by runoff during cooler and wetter phases in the earlier periods of the Pleistocene, similar to that observed along the Hatchie River (Grimley et al, 2009). A comparison of 185 radiocarbon samples from tributary floodplains in northern Mississippi revealed only sparse evidence for intensive fan formation and accompanying valley incision or gullying during the late Pleistocene (Grissinger and Murphey, 1984b).…”

“…Shown also is the Wagon Wheel Site from Barnhardt (1988) which shows a similar, and we suggest correlative, stratigraphy to our E6 site. et al, 1982;Smith, 1983;Grissinger and Murphey, 1984a,b;Barnhardt, 1988;Grimley et al, 2009). These studies demonstrate cool, boreal conditions in western Tennessee during the Last Glacial Maximum when soils in the bluff area were highly degraded.…”

“…Phase 1b: the upper Peoria loess was deposited during and after the maximum of the Wisconsin glaciation (Rodbell et al, 1997;Markewich et al, 1998;Grimley et al, 2009). Some exposed sites along the bluff line (not shown here) show clear evidence for soil development under a woodland vegetation cover in warmer interstadials.…”

“…12, phase 1a). Loess deposition occurred primarily during glacial maxima with substantial paleosol development occurring during interglacial and interstadial intervals (Rodbell et al, 1997;Markewich et al, 1998;Grimley et al, 2009).…”