DYNAMIC EVAPORITE CRYSTALLIZATION AND DISSOLUTION IN A SALINE PAN: ENVIRONMENTAL AND PETROGRAPHIC OBSERVATIONS OF EVAPORITE CRUSTS AT THE BONNEVILLE SALT FLATS, UTAH, USA

The Bonneville Salt Flats is a dynamic saline pan in Utah. Natural and anthropogenic processes, including fluctuating hydrological balances, eolian transport, solute cycling through brine mining and replenishment, and surface disruption, influence this system. This research focuses on the interactions of the evaporite crust and liquid and vapor water movement. It utilizes visual and surficial environmental observations, and groundwater temperature, level, density, and compositional measurements at differing temporal scales over three years. These new high-resolution environmental observations yield insights into the timing and mechanisms of halite growth and dissolution. These data show that 1) there is ~2 cm diurnal fluctuation in the groundwater table with the highest level occurring in the middle of the day, 2) the density of groundwater within the evaporite crust fluctuates on two to five day periods, suggesting circulation, 3) evaporation rates are controlled by surface moisture and reduced by over a factor of ten when the surface is desiccated. Observed processes vary depending upon the surface state of BSF – flooded or desiccated. These observations suggest that halite growth from the evaporation of brine is minimal when the surface is desiccated. Periodic fluctuations in groundwater density and level may enhance subsurface halite dissolution and precipitation. These environmental observations are placed within the context of BSF’s well-characterized evaporite morphologies. They enhance our understanding of the physical processes that affect saline pan diagenesis and microbial ecosystems.