CONNECTING DESERT GEOMORPHIC ACTIVITY TO EOLIAN FLUX IN THE SOUTHWESTERN US DURING THE QUATERNARY PERIOD

Stratigraphies of eolian sediment accumulation offer insight into upwind geomorphic processes that produce and emit dust. Here, we present a nearly one-million-year-long record of continuous dust accumulation on the southwestern edge of the Colorado Plateau from Stoneman Lake in central Arizona, USA. The core’s existing chronology, based on 15 radiocarbon dates, tephrochronology of the Lava Creek B, Early Rhyolite, Bishop Ash, and Upper Glass Mountain tephra, and correlation of facies and pollen changes to global climate transitions, shows depositional continuity to at least 1 Ma and a strong sensitivity of paleoenvironmental indicators to glacial-interglacial climate change. The lake catchment’s small size, limited fluvial activity, and basaltic bedrock promote straightforward identification and quantification of windblown dust likely derived from upwind landscapes in the Mojave and Sonoran Deserts. Dust mass accumulation rate is determined from the product of dry bulk density of clastics, the sedimentation rate, and the fractional percent of dust in bulk sediment, derived from end member modeling of laser granulometric data. During the Late Quaternary, dust accumulation at Stoneman Lake corresponds to episodes of alluvial and fluvial aggradation. This suggests that the supply of fine sediment in upwind desert landscapes, determined by geomorphic responses to climate change, is the first order control on regional dust flux. Desert deposits from deeper in the past are more likely to be completely eroded from the modern landscape, and therefore undatable by direct means. The Stoneman Lake core’s dust accumulation record stretches further into the past than the age of most Quaternary deposits in the southwestern US. It can therefore be used to determine dust flux and consequently a regionally integrated signal of fluvial and alluvial aggradation much further into the past than previously possible.