Abstract
AbstractProduction of the silt that forms loess is attributed to processes operating in both glacial systems (glacial grinding) and sandy deserts (saltation-induced fracturing). However, the efficacy of saltation for significant silt production is controversial. Understanding the potential for silt production in deserts is essential for determining the paleoclimatic significance of loess. To better assess the significance of eolian abrasion for silt production, experimental abrasion was conducted in a device designed to simulate sand saltation at sustained storm-wind velocities (∼25 m/s). The design differs from previous work in (1) maintaining strong measured velocities for long duration, (2) removing preexisting silt and utilizing control samples, (3) and scaling results to estimate potential for loess accumulation. Scaling experimental rates of production to geologic proportions indicates that eolian abrasion of sand produces insufficient silt to create geologically significant loess deposits.
Highlights
Silt composing many of Earth’s major loess deposits is linked to physical grinding from glacial processes (e.g., Pye, 1995; Smalley, 1995; Assallay et al, 1998; Muhs, 2013)
If deserts do not produce significant silt in the loess size range through eolian abrasion, desert-adjacent loess deposits likely contain silt produced by glaciation or other mechanisms
Silt in loess could contain a small fraction of material produced from eolian abrasion of sand, the majority of silt in loess likely originated via other processes
Summary
Silt composing many of Earth’s major loess deposits is linked to physical grinding from glacial processes (e.g., Pye, 1995; Smalley, 1995; Assallay et al, 1998; Muhs, 2013). The desert loess hypothesis posits that the silt that forms loess originates largely by eolian abrasion of sand (e.g., Smalley and Vita-Finzi, 1968; Tsoar and Pye, 1987; Smith et al, 2002; Crouvi et al, 2008; Enzel et al, 2010), Muhs (2013) noted that so-called “desert loess” could derive from deflation of silty sources (e.g., playas) or silt-rich protoliths. Some assert that eolian abrasion plays a large role in silt production (Smith et al, 2002; Crouvi et al, 2008; Enzel et al, 2010). If deserts do not produce significant silt in the loess size range through eolian abrasion, desert-adjacent loess deposits likely contain silt produced by glaciation or other mechanisms
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