Optical and radiocarbon ages of stacked paleosols and dune sands in the Nebraska Sand Hills, USA

Optical ages for eolian sands from the Nebraska Sand Hills indicate periods of extensive eolian activity at ca 115725, 840770, 23007240, and 35607340 a. Activity was also noted at single sampling locations at ca 61807370, 84307510 and 131107800 a. Many of these ages are similar to those noted by earlier authors. Optical ages from samples collected within paleosols indicate shorter and possibly less extensive periods of eolian activity at approximately 12207150, 15907110, and possibly 19507150 a, during which the paleosol sands accumulated. What was originally interpreted as a single 1.2m thick paleosol is shown by optical dating to consist of three or more welded soils developed within eolian sands with optical ages of ca 38007240, 27407240, 15607110, and possibly 19307140 a, each of which match eolian pulses recognized elsewhere. Scatter in some optical ages is attributable to intersection of sand-filled rodent burrows extending in outcrop 1.5m below the contact between paleosol and overlying topset beds. A 53107360 a optical age for one probable intersected burrow provides evidence for upward or lateral transport of older sands. r 2003 Elsevier Ltd. All rights reserved.