CHIRP SEISMIC ATLAS FOR JACKSON LAKE, WYOMING: EVIDENCE FOR LATE QUATERNARY TECTONIC, CLIMATIC, AND ANTHROPOGENIC CHANGES

Jackson Lake in Grand Teton National Park (Wyoming, USA) provides near-ideal imaging conditions for marine-type geophysics. Submerged features here (e.g., paleoshorelines, normal faults) have been the targets of seismic reflection and side-scan sonar surveys since the early 1980s. Recent advances in compressed high-intensity radar pulse (CHIRP) sub-bottom profiling technology and seismic data processing routines have afforded the opportunity to re-examine Jackson Lake’s stratigraphy and structure at high-resolution. Here we present a catalog of CHIRP seismic reflection images collected from Jackson Lake in 2018 and 2021. Seismic images reveal considerable morphological complexity, owing to the presence of fault-controlled margin-coincident topography (e.g., the Teton range), the Snake River delta, drowned glacial landforms, sub-merged springs, and the Jackson Lake dam. Strata in the lake’s depocenter exceed 100 milliseconds TWTT thick and show evidence of fault-related deformation above the acoustic basement. The stratigraphy is heavily influenced by slope failures and mass wasting processes, possibly triggered by major Holocene earthquakes associated with the Teton fault. High-resolution CHIRP sub-bottom imagery was crucial for landing two long scientific boreholes in Jackson Lake; sediments from these cores provide ground-truth for seismic stratigraphic interpretations and radiocarbon age control that clarifies the timeline of important geological processes affecting the region.