SHIFTING SANDS: DUNE ACTIVITY RECORDS OF NATURAL MOISTURE VARIABILITY IN THE CENTRAL COLORADO PLATEAU
Sand dunes are complex geomorphic landforms responsive to threshold climate conditions of aridity, wind velocity, vegetative cover and sediment supply. We investigate eolian activity in two dune fields in southern Utah using optically stimulated luminescence (OSL) dating and radiocarbon (14C) ages from charcoal, filling a regional gap in available paleoclimate records. Geomorphic maps constructed for each dune field using dune morphology and vegetation density form the basis for our systematic sampling plan. Stratigraphy, geomorphology, sedimentology (grain size) and age control obtained from OSL and 14C dating are used to differentiate sediment packages and develop dune chronostratigraphy. We interpret contemporaneous dune-field activity to represent persistent, regional droughts leading to changes in threshold conditions for dune mobility.
Here we present a chronostratigraphy of dune activity for the Kanab dune field in southwestern Utah and review preliminary chronostratigraphy for San Rafael dune field in southeastern Utah. Geochemical and grain-size analyses are used to determine the sediment source for two dune fields and discuss geomorphic processes contributing to dune field development. Finally, we discuss the implications for the Holocene climate changes recorded in our dune activity record.