HIGH-RESOLUTION 3D IMAGING OF LAKE BONNEVILLE SHORELINE STRATIGRAPHY USING GPR

Three-dimensional (3D) ground-penetrating radar (GPR) imaging can resolve fine-scale stratigraphic features down to a few centimeters. Pilot Valley, located in the eastern Basin and Range, north of Wendover, Utah, contains numerous shorelines and depositional remnants of ancient Lake Bonneville. Some of these remnants present classic GPR targets due to their coherent stratification and due to their low-clay, low-salinity, and low-moisture content. While lake levels in Lake Bonneville fluctuated due to flooding events, climatic changes were the dominant factor in controlling lake elevation. In Pilot Valley, the paleo-wind entered from the northwest and circulated clockwise around the basin, forming offshore sand bars. On the western side of the valley, a uniquely well-preserved regressive phase beach deposit, dated late Pleistocene, is hypothesized to have been a point bar around the time that the Provo Shoreline developed. 3D GPR data, measured stratigraphic sections, cores, mineralogical analysis, and the collection of gastropod samples for radiocarbon dating constrain a reconstruction of the depositional environment and local paleoclimate for Lake Bonneville. The GPR images, visualized with state-of-the-art petroleum industry tools, reveal fine-scale stratigraphic detail that can be analyzed using seismic stratigraphy concepts. Our study provides a comprehensive model for ancient pluvial lake-shore depositional environments in a Basin and Range setting using an integration of geological and geophysical data.