LATE HOLOCENE DUNE ACTIVATION AFTER THE MEDIEVAL CLIMATIC ANOMALY IN THE ARKANSAS RIVER VALLEY, SOUTH-CENTRAL KANSAS

Within the central Great Plains, several chronologies of sand-dune activation have been reported, but most of these are from sites on the High Plains of western Nebraska, Colorado, Kansas, and Oklahoma. Little work has been conducted in the eastern part of the region, however, which would serve to provide a more spatially comprehensive perspective on the impact of prehistoric Midcontinent droughts. This study is the third in a north-to-south sequence of sites intended to document activation histories along the eastern margin of the central Great Plains: the Duncan dune field in the eastern Platte River valley, Nebraska (Hanson et al., 2009), the Abilene dune field adjacent to the Solomon River in northeastern Kansas (Hanson et al., in review), and this study of the Hutchinson dune field along the Arkansas River in south-central Kansas. The Hutchinson dune field mantles a high terrace on the north side of the Arkansas River valley that optical dating methods indicate was deposited prior to 61 ka. Optical age estimates from dunes overlying the terrace (n = 13) indicate that dunes were active from ~1200 to 120 years ago. Some of our ages indicate that dunes were active during the Medieval Climatic Anomaly, a period when many other dune fields located on the western Great Plains also show dune activation. However, most of our ages were concentrated between 400 to 300 years ago, indicating drought impacted this region much more recently than locations to the north. Activation ages of about 300 years ago were obtained from samples taken deep within dunes (>7 m), indicating that massive dune activity, and associated drought, occurred within the eastern Great Plains and at least locally impacted some dunes only a few hundred years ago.