LATE HOLOCENE HISTORY OF DUNE ACTIVITY ALONG THE ELKHORN RIVER IN NORTHEASTERN NEBRASKA

The Nebraska Sand Hills have been an important study area for dune activation and the nature of drought events in the Great Plains for the past four decades. However, little has been done to understand the impact of these droughts to smaller dune fields along the eastern margin of the Great Plains. This study focuses on the Stanton dune field, found to the east of the Sand Hills along the southern banks of the Elkhorn River near the town of Stanton in northeastern Nebraska. With a wetter and slightly cooler climate regime than that of the Nebraska Sand Hills and most of the Great Plains dunes, the study of the Stanton dunes could provide valuable insight into the extent of large-scale dune activation. In addition, this study could determine whether there is a climatic threshold for dune activation along the eastern margin of the Great Plains. Sixteen preliminary optically stimulated luminescence (OSL) ages from the Stanton dunes reveal several activation periods that cluster into three distinct groups: 400-500 years ago (n = 5), around 800 years ago (n = 2), and around 4,000 years ago (n = 2). The first set of ages are significantly younger than the last major dune activation of the Nebraska Sand Hills, while the following two sets of ages correlate with the activation of the major dune fields in the western Great Plains. Regional megadroughts throughout the Great Plains, correlating with the latter two age sets, may have increased sediment supply from the Sand Hills to the Elkhorn River, and subsequently to the Stanton dune field. Preliminary age estimates in the Stanton dune field suggests that megadroughts reach far beyond the eastern edge of the Nebraska Sand Hills. Whether these events were driven by drought, changes in sediment supply, or a combination is yet to be determined.