Abstract

Stabilized dune fields are common features near Hudson, on the Piedmont of northern Colorado. Exposures in dune and interdune sites expose a sequence of eolian sediments and paleosols that record a complex history of eolian activity during the late Quaternary. Radiocarbon and thermoluminescence age estimates on A horizons buried by eolian sand indicate that dunes were reactivated sometime between 7 and 9 ka. On the basis of morphology of surface soils, the dunes were most recently stabilized <3 ka. At present there are no data to indicate if there were multiple periods of dune movement and stabilization during the Holocene. The penultimate pre-Holocene dune-forming episode probably terminated ca. 13 ka and may be coincident with the Pinedale glaciation. The stratigraphy at interdune sites shows at least two eolian depositional events prior to the penultimate event; they were separated by periods of pedogenesis, one of which may have exceeded 40 ka. This analysis indicates that dunes in northern Colorado were active during both cold-arid and warm-arid periods in the late Quaternary.

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