IRSL DATING OF A VEGETATED DUNE FIELD IN CENTRAL ALASKA

High-latitude dunes of Alaska are ubiquitous landscape features that contain significant records of late-Quaternary paleoclimatic change within their stratigraphy. While some high-latitude dune fields have been examined in past research, those in central Alaska have received little attention. This study examines a dune field located just south of Nenana, AK, in the Tanana River Lowlands (TRL) of central Alaska. These low-relief, vegetated dunes rest atop alluvium of the Nenana River and are mantled by a thin (<1m) loess cap presumed to be Holocene in age. Our objectives are to (1) address the unresolved questions of when dune formation occurred for the Nenana dunes, as well as if and when the most recent reactivation period occurred, and (2) identify the primary source for the sand comprising the dunes. A recent pilot study of another vegetated dune field of the western TRL determined that the dunes formed ~15-16 ka and the last stabilization occurred ~10-12 ka. Use of traditional protocols for optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL) dating produced anomalously young ages; however, a newly-developed IRSL protocol yielded the above ages that are in agreement with limited AMS¹⁴C ages from charcoal. The current study will utilize this new protocol, known as post-IR IRSL, that was validated by the pilot study. Samples were collected July 2013 from the loess mantle and underlying sand of the Nenana dunes via auguring and man-made profiles for analyses including IRSL dating, rock magnetics, and geochemistry (ICP-MS). Approximately 20 IRSL samples, collected from the crest, base, and flanks of the dunes, will be dated at the Utah State University Luminescence Laboratory following the aforementioned IRSL protocol. Understanding the formation and reactivation chronologies of these dunes will identify periods when past climates created a favorable environment for sand mobilization. Advancing our knowledge of these events can provide insight on the environmental impacts that future climatic conditions are likely to bring about, particularly in these higher latitudes where climate change is occurring most rapidly.