DYNAMIC FLUVIAL AND EOLIAN SYSTEMS IN SOUTHERN UTAH. LOOKING INTO THE PAST, WITH AN EYE TOWARD THE FUTURE

Holocene geomorphic archives from the central Colorado Plateau in Southern Utah record abrupt large magnitude changes in landscape dynamics. Streams draining the Grand Staircase toward Grand Canyon experienced up to five arroyo entrenchment and re-aggradation events in the last 6 kyr, some locally changing grade up to 40 m on centennial time-scales. Dune fields experienced four to five periods of activation followed by stabilization over the same time period. Although less well documented, loess and alluvial fan deposition similarly fluctuated during the mid- to late Holocene. These geomorphic changes all occurred during relatively stable mean-state climate in the region, attesting to the sensitivity of the regional landscape to environmental change and hydroclimate variability. These geomorphic records provide valuable constraints on the range of natural landscape response to non-anthropogenic environmental perturbations and climate change, including autogenic dynamics. Understanding the natural variability, sensitivity and dynamics of these systems is important for assessing the response of the region to current and future inter-connected changes in climate, hydrology, ecosystems and geomorphic/landscape dynamics of the region. Middle to late Holocene records from the central Colorado Plateau will be presented in context of how these archives may help guide understanding of systems-response to predicted change in the region.