HIGH-RESOLUTION SHALLOW ACOUSTIC SURVEY OF FISH LAKE, UTAH

Fish Lake is a high-altitude (2700 m) lake on Utah’s High Plateaus, located in a Quaternary graben complex that borders the transition zone between the Basin and Range and the Colorado Plateau. Measuring approximately 5km by 1.7km with a maximum recorded depth of 37m and an average depth of 27m, the NE-SW trending lake is currently fed by several small creeks from a small (~150 km²) drainage area. The Hightop Plateau (elevation ~3500m) on the northwest side of the lake maintained glaciers that fed into at least one end of the lake during the LGM. This study presents results from a high-resolution chirp subbottom profiler survey in the main body of the lake, combined with bathymetric and sidescan sonar surveys, to present the shallow stratigraphic architecture and sedimentary infill geometries for the lake. Seismic penetration was from <1m in gas-rich sediments to 40+ m away from the central axis of the lake, leaving an estimated 60- to 250-m of deeper material for future work. The lakefloor reflector was strong to weak to imperceptible. Complexity of seismic packages is highest near the lake edges, with more horizontal and parallel sequences towards the center of the lake away from fluvial and glacio-fluvial sources. Multiple seismic packages separated by strong reflectors adjacent to Doctor Creek (unglaciated) are apparent at several levels in the lake and may represent various lake levels. Across the basin, four to six distinct seismic sequences are present, providing a detailed seismic framework for the upper 40-m of sediment.