Post-IR IRSL Dating of the Nenana Dune Field in the Tanana Lowlands, central Alaska

Abstract

Sand dunes record paleoclimatic change within their stratigraphy as they respond to climatic shifts through sequences of activation and stabilization. Developing chronologies documenting periods of dune activity and stabilization can thus provide information about past climatic conditions. Consequently, the need for accurate chronological determinations of aeolian features has stimulated the advancement of dating techniques. In Alaskan sand dune settings, radiocarbon dating of organic material and optical dating of quartz grains have proven to be problematic due to insufficient organic material and a weak optical signal, respectively. In such cases, feldspar grains can be dated using Infrared Stimulated Luminescence (IRSL) dating, but are often avoided due to inherent anomalous fading that results in age underestimation. The lack of a viable dating technique has resulted in a paucity of chronostratigraphic Alaskan dune studies, particularly within central Alaska. This research tests the use of a post-infrared (pIR) IRSL protocol, specifically designed to limit the effects of anomalous fading, on the Nenana dune field within the Tanana River Lowlands of central Alaska. Results indicate that dune activity occurred as far back as ~16 ka for the Nenana dunes, as deglaciation of the surrounding area provided an influx of sediment into glacial streams throughout the Tanana River Lowlands. IRSL ages indicate a switch from sand to silt accumulation between 11 ka and 10 ka and stabilization of the dune field that is likely tied to the spread of boreal forest throughout the region around this time. These IRSL ages align with regional proxy data indicating similar timing of activation and stabilization of aeolian features during the transition between the Late Pleistocene and early Holocene. This research represents one of the first IRSL sand dune studies of central Alaska and supports further use of a pIR IRSL protocol to expand aeolian research within Alaska.