EOLIAN ACTIVITY IN THE SOUTHWESTERN US OVER THE LAST 1 MA FROM THE STONEMAN LAKE, AZ RECORD

A lacustrine sediment core (STL14: Stoneman Lake, Arizona, USA) from the southwestern edge of the Colorado Plateau is ideally situated to disentangle a continuous history of eolian activity, geomorphic changes, and climate in the arid southwest since the Early Pleistocene. Long-term perspectives on surficial processes are especially important in the American Southwest where weathering, erosion, and wind play a pivotal role in shaping geographic, ecologic, and human landscapes. In this study, we compare elemental indicators from 0.5 cm-resolution X-ray fluorescence core scans (ITRAX) to those of catchment bedrock and soils. Core sediments and thin hillslope soils from around the lake are mineralogically and geochemically similar to eolian material and are distinct from local basalt bedrock. The core record’s K:Ti and Zr:Ti ratios indicate eolian inputs exhibit glacial-interglacial variations over the last 1 Ma, generally reaching a maximum during glacial periods when Stoneman Lake was at its deepest. This pattern is similar to other long dust records from the Chinese Loess Plateau and polar ice cores, despite greater local effective precipitation (interpreted from deeper lake deposits). MIS 22, 20, 10, and 8 appear to be the dustiest glacials based on the K:Ti ratio. Increased long-range transport of dust resulting from stronger winds and more global dust sources may have combined with local, sediment-exposing processes like floodplain activity and playa margin fluctuations to increase dustiness in the southwest during glacials. This finding is an important insight into critical zone behaviors in the southwest over longer timescales.