Isotope fingerprinting reveals western North American sources of modern dust in the Uinta Mountains, Utah, USA

The deposition of aeolian dust has profound effects on biogeochemical cycling, soil development, and hydrology in alpine ecosystems. In the western United States, it has been proposed that much of the dust reaching the Rocky Mountains is derived from arid regions located to the west-southwest. Because these areas are vulnerable to drought-related changes in vegetation, grazing impacts, mining, off-road vehicle travel, urban development, and other factors that affect the availability of fine-grained sediment for wind deflation, it is imperative that source areas for this dust be better constrained to guide future management decisions. Here we collect modern dust in the Uinta Mountains (Utah) and compare its 87Sr/86Sr and 143Nd/144Nd “fingerprint” with surficial sediments in possible source areas. Our results confirm that this dust is exotic to the Uinta Mountains, and demonstrate its similarity to numerous dune fields in western Utah, as well as surficial sediments in parts of the Colorado Plateau, southern Basin and Range, and the Mojave Desert. The seasonal sampling we employed also reveals that considerable dust is deposited during the shorter alpine summer. Recognition that specific areas in the southwestern US are sources of dust to the Rocky Mountains, particularly during summer months, should be considered in future land management planning.