EXPLORING GEOLOGIC PROCESSES OF GREAT SALT LAKE WITH BATHYMETRIC LIDAR

Great Salt Lake in north-central Utah is the largest saline terminal lake in North America. It occupies the lowest part of the vast Bonneville Basin which has contained extensive climatically driven pluvial lakes during the Miocene to Late Pleistocene and Holocene. The modern Great Salt Lake is shallow (avg. depth 4.3 m, 14 ft; max. depth 10.6 m, 35 ft), saline (∼12% in the South Arm), and hosts unique biological systems. The most foundational component of the lake ecosystem are microbial carbonate “reefs” that grow in shallow water around the lake. The Oquirrh-Great Salt Lake fault zone bisects the lake, and previous seismic reflection studies indicate subsurface faulting correlates broadly with escarpments mapped using marine acoustic technologies. Climate change and historical water diversions have decreased surface water inflows and the lake elevation. Accurately measuring the bathymetry of Great Salt Lake is critical to understanding how the lake may change over time. Terrestrial high-resolution topographic data (i.e., lidar) has revolutionized how geoscientists are able to inspect, quantify, monitor, and model landscapes, vegetation, hazards, and human impacts. Similarly, bathymetric lidar data can be used to quantify, monitor, and show change in subaqueous environments. In spring 2023, the Utah Geological Survey (UGS) collected bathymetric lidar data over a pilot study area of 130 square kilometers (~50 square miles) of Great Salt Lake off the west coast of Antelope Island. The survey reached depths of 4.5 meters and shows sub-meter topographic relief on microbialite structures in the nearshore environment. Bedforms on the shallow shelf from lake current cycling are visible, and one area of slumping off of the western fault-related shelf raises some questions about how the lake’s surface responds to seismic shaking. As a result of this successful pilot study, the UGS is currently working with a contractor to collect bathymetric lidar data for the entire shallow-water perimeter of Great Salt Lake (down to ~4180 feet elevation), Farmington Bay, and Bear River Bay. We will present initial observations and findings of the pilot dataset and best practices we have found for bathymetric lidar surveys in hypersaline lakes.