Wednesday, 8 October 2008: 8:15 AM
George R. Brown Convention Center, 352DEF
Activation histories of the larger central Great Plains dune fields, including the Nebraska Sand Hills and the Great Bend Sand Prairie in Kansas, indicate nearly contemporaneous movement from ~ 1000-600 yrs ago. Though smaller dune fields found to the east of these larger dune systems have not received much attention, they potentially hold important information regarding the geographic extents of ancient drought events. For this study, optical (aka OSL) dating methods were used to determine activation histories of three relatively small dune systems in eastern Nebraska and Kansas. Dunes along the Smoky Hill River near the town of Abilene, Kansas were last active between 1100-500 years ago and were previously moving prior to 10,000 years ago. Dunes in the Platte River Valley near Duncan, Nebraska were active twice in the past ~ 5,000 years, with ages clustering around 3800 and 700 years ago. Two preliminary age estimates taken from another dune field located to the east and northeast of the Elkhorn River near the town of Scribner, Nebraska indicates that dunes were last active around 10,000 years ago. Although our collective findings are preliminary, these ages indicate that the megadroughts responsible for the activation of the larger Great Plains dune fields also resulted in the mobilization of smaller dune fields near the eastern edge of the central Great Plains. The preliminary 10,000 year old dune ages near Scribner, Nebraska may indicate an eastern extent for drought-induced vegetation reductions that were adequate for dune mobilization during late Holocene megadroughts.