Obliteration of surficial paleolake evidence in the Tule Valley subbasin of Lake Bonneville

This paper analyzes the extent of preserved and obliterated paleolake shoreline and sediment evidence in the Tule Valley subbasin of Lake Bonneville. It identifies the dominant processes responsible for effacing the paleolake evidence and estimates long-term average obliteration rates. Temporal control is provided by the well-constrained reconstructed chronology of Lake Bonneville. Erosion associated with alluvial-fan processes is overwhelmingly responsible for the partial obliteration of the studied shorelines. Long-term average shoreline-obliteration rates vary from 3.0 to 5.7 percent per 1,000 yrs. Extent of preservation increases with the strength of a shoreline's geomorphic development. Measurements of the areal extent of all lacustrine and nonlacustrine Quaternary deposits below the highest shoreline reveal that 57 percent of the paleolake sediments have been removed from surface exposure since the start of Lake Bonneville regression. This yields a long-term average obliteration rate of 3.9 percent (47 km2) per 1,000 yrs. Alluvial-fan and eolian processes are responsible for 89 and 11 percent, respectively, of the removal of paleolake sediments from surficial exposure in Tule Valley.