Revision to the chronology of the early transgressive phase of Lake Bonneville

Abstract

Abstract Newly available 14C and U-Th ages for microbialites at Death Point (on the shore of Great Salt Lake at Lakeside, UT; Jour Quat Sci 2022) call for a major revision of the Lake Bonneville hydrograph. At the beginning of the Lake Bonneville cycle, the lake experienced an abrupt rise about 30,000 cal yr BP, then dropped back down to levels near the modern elevation of Great Salt Lake, then over the ensuing 6 thousands of years the lake experienced a series of fluctuations, up to levels a few 10s of meters higher than average Great Salt Lake levels then down again. The exact timing and amplitudes of those fluctuations are not known at this time, but importantly the lake did not rise to levels near the Stansbury shoreline until after about 24,000 cal yr BP. Although the Stansbury oscillation(s) occurred during the transgressive phase of Lake Bonneville, not during the regressive phase, as was traditionally thought, the oscillation(s) were younger than 24,000 cal yr BP. This interpretation conflicts with previously published chronologies.