Aeolian sand depositional records from western Nebraska: landscape response to droughts in the past 1500 years.

The Great Plains is dominated by presently stabilized dune fields that are indicators of extreme drought in the late Holocene. This study focused on deciphering the timing of reactivation of dunes in western Nebraska. Stratigraphy adjacent to dune-dammed lakes reveals aeolian sand separated by palaeosols, indicating mobilization of aeolian sand followed by landscape stability. The chronology of aeolian-sand depositional events is constrained using the luminescence-based, single aliquot regeneration method, providing resolution to relate dune movement to tree-ring and palaeolimnologic records of drought. There are at least a six aeolian depositional events in the past 1500 years, with apparent mean ages of 1390±130, 670±70, 470±40, 240±40, 140±20 and 70±10 yr. All study sites show evidence for aeolian accumulation in the twentieth century, potentially reflecting the 1930s drought. Significant aeolian activity is coincident with the tree-ring-identified sixteenth-century megadrought, indicating widespread landscape impacts. [ABSTRACT FROM AUTHOR]