Avulsion History of the Yukon River Since the Last Glacial Maximum

The Yukon fluvial-deltaic system is the largest sediment source surrounding the Bering Sea. Much of its sediment load is transferred to the Arctic Ocean by northward directed surface currents during sea level highstands such as today. Yet, during lowstands there is inferential evidence suggesting the Yukon flowed into the deep Bering Basin. It may have even connected with Alaska's third largest sediment producer, the Kuskokwim River, during the last glaciation. This work proposes to test the hypotheses that the Yukon River avulsed from south to north since the Last Glacial Maximum and that during the early part of this migration the Yukon separated from the Kuskokwim River, making two independent river systems. In the summer of 2012 we collected several 2 to 5 meter sediment cores from the floodplains of the Yukon and Kuskokwim Rivers as well as multiple dug pit sites for determining thermoluminescence ages of dune and loess deposits in the Yukon Delta region. We will present down core sedimentologic data in conjunction with satellite imagery and high resolution topography to provide initial interpretations of the fluvial-deltaic stratigraphy and avulsion history of the Yukon-Kuskokwim Delta.