LAKE BONNEVILLE SHORELINES IN NORTHEAST UTAH: PROXIES FOR PALEOWIND DIRECTION?

Paleowind directions in the eastern Great Basin are poorly understood despite numerous Quaternary paleoclimate studies. Transgressions and regressions of the Late Pleistocene pluvial Lake Bonneville developed excellent shorelines throughout the Bonneville basin, with the greatest highstand approximately 15,000 radiocarbon years ago. Depositional and erosional features of Lake Bonneville shorelines are used to help reconstruct both hydrodynamic conditions and paleowind direction in the northwest portion of the Bonneville basin.

On the northeast side of the Pilot Mountain Range, bedrock of cherty limestone formed islands, which were influenced by lake processes on all sides, allowing for shoreline exposure to all possible wind directions. The primary features of bench width, tufa localities, and erosional and depositional character of the Provo (post highstand) level shorelines are mapped and evaluated with respect to different transport incident and exposure angles. The mapped features are used to evaluate hydrodynamic conditions and infer paleowind directions, with additional consideration of bedrock type, susceptibility to erosion, accommodation space, sediment supply, slope, and fetch. Preliminary mapping at two localities northeast of the Pilot Range (Lion Mountain and Lucin Hill) reveals headlands with significant tufa and no bench development on northeast aspects. Additionally, erosional benches with little to no deposition on the eastern aspects and significant depositional features on western aspects indicate a possible paleowind direction from the northeast.

Field-based hydrodynamic information is vital to interpreting processes of Lake Bonneville during the Late Pleistocene. This data can be used as “ground-truth” for constructing and understanding larger Quaternary regional climate models.