EVALUATING DESERT SILT PRODUCTION USING FIELD, EXPERIMENTAL, AND REMOTE-SENSING METHODS

Abstract

Production of the silt that forms loess deposits has been attributed to processes operating in both glacial environments (via glacial grinding) and warm deserts (via saltation-induced fracturing). However, the efficacy of warm desert processes for major silt production remains controversial. Understanding the potential for silt production in desert environments is essential for determining the paleoclimatic significance of loess deposits. To better assess the significance of aeolian abrasion as a silt production mechanism, experimental abrasion was conducted in a device designed to enable saltation of sand (~100 g) at sustained storm wind velocities (~25 m/s). This design differs from previous studies in using 1) natural aeolian dune sand, 2) a relatively large starting mass, and 3) controlled wind velocities, and thus enables the scaling of results to natural geologic conditions. After experimental abrasion, produced silt had a mode (35.3 - 45.6 µm) which is in the range of typical North American Peoria loess, coarser than typically found in the Chinese Loess Plateau (25 µm) and finer than coarse modes found at desert margins in north Africa (>60 µm). Scaling rates of production from experimental results to the geologically significant scale indicates aeolian abrasion within deserts produces insufficient silt to create large loess deposits.