Airborne geophysical imaging of freshwater reservoir beneath the eastern margin of Great Salt Lake

This paper presents the results of the pilot airborne electromagnetic (AEM) and magnetic survey conducted over a sector of Great Salt Lake (GSL), Utah, aimed at investigating the potential presence of a large freshwater reservoir beneath the lake -the largest inland saline water body in the Western Hemisphere. A 3D inversion of AEM data reveals a laterally extensive resistive layer underlying the lake's highly conductive brine. This resistive unit is interpreted as freshwater-saturated sediments or bedrock. Its identification provides evidence for substantial freshwater resources beneath the hypersaline layer. The presence of freshwater-saturated sediments beneath the saline water layer has been independently verified by direct measurements of water salinity and chemistry from cores collected in the wells. It has been demonstrated that the AEM method can overcome the challenge of imaging through a hypersaline surface layer to map deeper freshwater. Complementing the AEM data, the magnetic data and their inversion into remanent magnetization provided valuable insights into deeper basement structures. Based on the results of the pilot project, we anticipate that airborne geophysics will enable basin-scale surveys beneath the expansive (> 4,000 km2) footprint of the Great Salt Lake, as well as surveys of other terminal lakes and offshore freshened groundwater.