Geochemical and mineralogical evidence from eolian sediments for northwesterly mid-Holocene paleowinds, central Kansas, USA

A prominent (4500 km(2)) dune field in the Great Plains is the Great Bend S and Prairie of south-central Kansas. Dunes here overlie late Quaternary all uvium and were reactivated extensively in the late Holocene. Geomorphic and soil evidence suggests that the most likely eolian sand source is the Arka nsas River valley to the northwest. Nevertheless, orientations of stabilize d dunes indicate that the most recent dune-forming winds came from the sout h or southwest, in agreement with modern wind data. Mineralogy and trace element concentrations in eolian sands of the Great Be nd Sand Prairie are similar to those of the Arkansas River, which permits t he Arkansas River as a sediment source. Ca and Sr abundances, which reflect small amounts of carbonate minerals, are higher in Arkansas River sand com pared to eolian sands and show a systematic depletion away from the Arkansa s River to the southeast. These trends are likely due to carbonate mineral depletion downwind from abrasion and size reduction. Thus, paleowinds proba bly were northwesterly during initial deposition. Northwesterly winds occur today when dry, Pacific-derived air is dominant. We hypothesize that the r esidence time of this air mass was much greater while dunes initially forme d, possibly during a warmer and drier mid-Holocene period. (C) 2000 Elsevie r Science Ltd and INQUA. All rights reserved.