The Central and Southern Great Plains

An often-windy landscape with few major topographic features, poorly consolidated fine-grained geology, and limited and variable precipitation has endowed the Central and Southern Great Plains with the ideal environment for development and repeated reactivation of dune fields and sand sheets. Mapping efforts have documented large numbers, sizes, and a wide distribution of aeolian sand deposits, and the application of soil texture, geochemistry and other data have begun to enhance our perspective on these deposits. In recent decades, numerical dating techniques have spurred inquiry into the development of activation chronologies, which have defined periods of sediment flux and prehistoric droughts, including megadroughts commonly observed in other paleoclimatic records. Nearly thirty dune fields within the region have been investigated and dated with radiocarbon and luminescence techniques. Activation, which has usually been climatically forced, occurs when sediment becomes transportable under the prevailing wind regime. Currently, most dunes throughout the Great Plains are, however, inactive, but those that are active occur primarily along the Texas-New Mexico border region and in areas impacted by human activity such as cattle ranching and off-road vehicle recreation. With the major exception of the Nebraska Sand Hills, most dune fields of the Central and Southern Great Plains are associated geomorphically with and in some cases geochemically-linked to one or more fluvial systems. Dunes composed of fine sediments (silt, clay) also occur in the region—lunettes, or crescentic dunes associated with playa basins (Kansas through to Texas into New Mexico), and the parna dunes of the Oklahoma Panhandle. Adaptation of mineralogical and geochemical finger printing of aeolian sand deposits and potential sand sourcing has made possible the identification of provenances (e.g., the Miocene Ogallala Formation and late Pleistocene-modern river systems) and by implication the directions of formative paleowinds. Given the early indications of global warming and model scenarios for the future, the Central and Southern Great Plains may experience future intense and extended-duration droughts and the attendant reactivation of dune fields and sand sheets.