EOLIAN ACTIVITY RECORDS FROM TWO SOUTHERN UTAH DUNE FIELDS: AN INSIGHT TO NATURAL HYDROCLIMATE VARIABILITY DURING HOLOCENE

A multi-decadal and ongoing drought in the beginning of the 2000’s AD has impacted much of the western United States and resulted in unprecedented Colorado River water supply restrictions to Arizona, Nevada and Mexico. Past mega-droughts have also affected this region. Growing population and changing climate add urgency to development of adaptive land and water management strategies for the region. Paleoclimate records that extend the relatively short instrumental record, and provide perspective on the magnitude and duration of natural hydroclimate variability, contribute to better understanding future hydroclimate variability.

Sand dunes are complex geomorphic landforms that are particularly sensitive to changes in aridity, capable of reactivation from a stable (vegetated) state when threshold wind and moisture conditions are exceeded. We systematically investigate eolian activity in sand dunes from two dune fields in southern Utah using optically stimulated luminescence (OSL) dating and radiocarbon (¹⁴C) ages from charcoal. Geomorphic maps for each dune field based on vegetation density and dune morphology are constructed as a first order evaluation of landscape processes. Stratigraphy, geomorphology, sedimentology (grain-size), and age control obtained from OSL and ¹⁴C dating are used to differentiate sediment packages and develop a chronostratigraphic record of dune activity for each dune field.

Here we present 38 ages from 24 sites in Kanab dune field (KDF) and 34 ages from 22 sites in San Rafael desert dune field (SRDF). Four millennial-scale episodes of eolian activity are determined for the Kanab dune field: E1 (~6.8-5.6 ka), E2 (~4.4-3.3 ka), E3 (~2.2-1.2 ka) and E4 (~0.7-0.4 ka). Three millennial-scale eolian episodes are determined for the San Rafael desert dune field: E2 (~9.6-7.4 ka), E4 (~3.4-2.5 ka), E6 (1.1-0.4 ka). Ages for these events are identified at multiple individual sites within the respective dune fields, and thus are interpreted as dune field-wide eolian activity. We discuss implications for regional hydroclimate variability based on differences in landscape response and chronostratigraphic records. Synchronous dune field-wide activity records occur in late Holocene ~3.4 ka (E2-KDF and E4-SRDF) and ~0.7-0.4 ka (E4-KDF and E6-SRDF).