Date of this Version
The Nebraska Sand Hills have been an important study area for dune activation and the nature of prehistoric drought events in the Great Plains. 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 which is found about 145 km east of the Sand Hills along the southern edge of the Elkhorn River valley in northeastern Nebraska. With a wetter and slightly cooler climate regime than that of the Nebraska Sand Hills and most other central Great Plains dunes, the Stanton dunes could provide valuable insight into the extent of large-scale dune activation and the nature of regional drought events. Twenty-four optically stimulated luminescence (OSL) ages from the Stanton dunes reveal several activation periods that cluster into several distinct groups: less than 120 years ago (n=2), around 410-630 years ago (n = 7), around 1000 years ago (n = 2), and around 3,800 to 5,800 years ago (n = 6). The two younger clusters do not correspond to major dune activation events in the Nebraska Sand Hills, while both of the older periods chronologically overlap with the activation of dunes in the Nebraska Sand Hills and other major central Great Plains dune fields. Optical ages in the Stanton dune field suggest that megadroughts reach far beyond the eastern edge of the Nebraska Sand Hills. Geochemical evidence indicates that the Stanton dunes and the underlying alluvium are similar to the sand found in the Nebraska Sand Hills. The two older dune formation events from the Stanton dunes may be related to drought-induced changes in sediment supply in the Elkhorn River which drains a portion of the Nebraska Sand Hills. Thus, the activation events of the Stanton dunes may have been driven by a combination of drought and changes in sediment supply.
Advisor: Paul R. Hanson