UTILIZING SURFACE TEXTURES TO UNDERSTAND CHANGE DYNAMICS AT THE BONNEVILLE SALT FLATS

Humans have used the Bonneville Salt Flats for recreational automobile racing and potash mining for over a century. The Bonneville Salt Flats (BSF) is a dynamic ephemeral saline pan consisting of a lens-shaped hard surface layer of interbedded halite and gypsum that changes in response to both human-use and climate. Five salt crust thickness studies since 1960 mapped BSF size and thickness. Our research builds and expands upon those studies and explores the connections between surface textures of the salt flats and underlying crust thicknesses. This work helps to identify ties between surface features and human uses including car racing, mining, and crust replenishment efforts. This research draws upon field observations, aerial imagery, time-lapse surface level photography, sedimentological textural, mineralogical, and geochemical data from over 60 core localities, and various types of microscopy. These data enable a new classification of BSF surface types. Halite polygons with raised halite rims are common in areas of thickest halite accumulation. These polygons have at least three scales of magnitude (<1 to >3 m wide, varying relief) which often are superimposed upon each other. “Popcorn” halite forms on daily timescales on the surface through capillary evaporation of the shallow groundwater brine. Surface textures change over daily, weekly, seasonal, and annual scales in response to both climatic and anthropogenic forces. Characterizing these changes and the primary drivers of change helps to guide interpretation of subsurface strata and the timescales of overall deposition and dissolution of BSF salt crust package. Surface textures are influenced by precipitation, evaporite input (solute and eolian flux), thermal flux, crust thickness, land use, and more. By further examining these surficial features and associated environmental data, this research will help to differentiate between natural and human driven textural changes within this system.