LATE PLEISTOCENE ALLUVIAL RECORDS IN THE GRAND STAIRCASE REGION, SOUTHERN UTAH

Research focuses on the influence of climate and geomorphic processes on late Pleistocene landscape evolution of the Grand Staircase region of southern Utah using alluvial deposits as markers of past hillslope sediment supply, river incision, and cliff retreat. Research tests whether these alluvial deposits record biogeomorphic response to past climate change. The primary hypothesis is that alluvial deposition corresponds to transitions between glacial (stadial) and interglacial (interstadial) conditions. Investigation and correlation of the alluvial deposits between five adjoining catchments is based on geomorphic and long-profile analysis, and detailed outcrop and facies descriptions of the sedimentology, stratigraphy and soil profile development. Age control is provided by optically stimulated luminescence (OSL) dating of representative alluvial deposits in each catchment.

Preliminary results suggest that late Pleistocene alluvial deposition occurred during transitions from glacial/stadial periods, with increase effective moisture, to warmer and more arid interglacial/interstadial climates during marine isotope stages (MIS) 3 and 5. Specifically, regionally extensive alluvial deposits have been dated to 42-54 ka, 71-74 ka, 60-82 ka, 95 ka and 100 ka. Additional analyses of modern and paleo-fluvial long profile morphology (e.g. slope, concavity, and steepness [ksn and chi]) was also analyzed using ArcGIS and MATLab coding to test for changes in stream profiles over time.