SEDIMENTOLOGY, MINERALOGY, GEOCHEMISTRY, AND GEOMICROBIOLOGY OF THE BONNEVILLE SALT FLATS

The Bonneville Salt Flats (BSF) of northwestern Utah are a dynamic and extreme hypersaline desert environment characterized by a perennial salt crust that spans over 30 square miles. The BSF are impacted by a range of natural and anthropogenic processes including extreme weather, complex surface and groundwater interactions, extensive land speed racing, and potash salt mining. Our interdisciplinary team of geologists and microbiologists are working to document the spatial heterogeneity in sedimentology, geochemistry, and mineralogy to interpret the natural variability and the impacts of the processes that influence the environment, and to evaluating how the observed geologic processes and deposits relate to the microbial ecology of the salt flats. Remote sensing analyses show how the surface has changed over seasonal, annual, and decadal time scales and help guide interpretations of the depositional history. Saline sediment and brine samples collected from BSF in August 2013, October 2013 and June 2014 were characterized mineralogically and geochemically via visible-near infrared spectroscopy, X-ray diffraction, X-ray fluorescence, and petrography. Associated surface and shallow groundwater brines were analyzed for H and O isotopes and show multiple different fluid populations actively precipitating salt. Microbes in the salt were identified by culturing pure isolates to run PCR amplifications of 16s rRNA genes for DNA sequencing. There is evidence of specialized halophilic microbes in sedimentary layers and other geologic features such as fractures and upwelling zones. The BSF stratigraphy is generally comprised of an ephemeral halite crust, historically meters thick and currently a few cm thick, overlying various layers of carbonate-rich gypsum, organic matter, clay, and unconsolidated halite crystals. Temporal and spatial changes in surfaces textures and spatial variations in stratigraphy illustrate the ephemeral and dynamic nature of the BSF deposits. Future work will include evaluation of spatial heterogeneity in geobiology, identification of the processes by which the microbial communities sustain and migrate through the salt flats, and the relative impact of natural versus anthropogenic processes on the environment.