CLIMATE CHANGE, PREHISTORIC DEFORESTATION, OR FLOODPLAIN EVOLUTION: MULTI-PROXY EVIDENCE FOR RAPID AND PERMANENT VEGETATION CHANGE DURING THE LATE HOLOCENE FROM AN OXBOW OF THE MISSISSIPPI RIVER, WAPANOCCA BAYOU, ARKANSAS, USA

Geoarchaeological cores from an infilling oxbow within the meander belt of the Central Mississippi Valley recovered evidence of a rapid shift in vegetation during the Late Holocene. The sampling site, Wapanocca Bayou (Crittenden County, Arkansas), is flanked by levee complexes that supported a large complex of Mississippian villages (AD 800-1540). Oxbow formation began by 350 BC and palynological data from a 10+ meter core documents a rapid shift from a Mixed Hardwood forest to a vegetation community dominated by non-arboreal and ruderal species beginning after AD 1050. Coeval diachronic trends in soil chemistry and magnetic susceptibility; charcoal concentrations; and archaeological data corroborate the pollen record and suggest a punctuated shift in vegetation that persisted into Historic times. The overhaul in vegetation roughly coincides with both the end of the Medieval Warm Period, and the expansion of local human settlements. Working alternative hypotheses that may explain this rapid change include climate change, prehistoric anthropogenic disturbances, or vegetation response to local floodplain evolution. Comparisons of the sedimentary record, regional paleoenvironmental reconstructions and archaeological evidence for human history are used to adjudicate between these alternatives.