DYNAMIC FLUVIAL AND EOLIAN SYSTEMS IN SOUTHERN UTAH. A CLIMATE OR GEOMORPHIC RECORD?

Holocene sedimentary 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 in the region similarly record four to five periods of activation followed by stabilization over the same time period. These geomorphic changes occurred during relatively stable middle to late Holocene climate conditions that were punctuated by regional multi-decadal drought and pluvial periods.

Understanding the natural variability, sensitivity and dynamics of alluvial and eolian systems is important for assessing the response of the region to past and future inter-connected changes in climate, hydrology, ecosystems and regional geomorphic/landscape dynamics. However, interpretations of Holocene records suggest either sensitivity in landscape response to hydroclimate variability, or alternatively, dynamic response of these systems to non-linear and autogenic geomorphic thresholds. Perhaps it is some combination of both? This talk will explore alluvial and eolian records from southern Utah and discuss possible linkages to climate change and evidence for geomorphic controls and overprinting of the records.