TIMING AND EXTENT OF GLACIATION IN THE NENANA VALLEY, ALASKA: TESTING THE SYNCHRONEITY OF GLACIATION IN ALASKA

Two major glacial systems influenced Alaska during glacial times: alpine glaciers and the Cordilleran Ice Sheet. However, much of the sedimentary record of these glacial systems is sparse because the extensive LGM Cordilleran Ice Sheet reworked or deposited a great deal of the record offshore. However, the more restricted glaciation of the Cordilleran Ice Sheet to the north of the Alaskan Range has resulted in the preservation of successions of glacial and non-glacial landforms in north trending valleys. These are particularly well preserved in the Nenana Valley where an ice stream from the Cordilleran Ice Sheet flowed north across the Alaska Range and coalesced with the Yanert Glacier, an alpine glacier that flowed northwestwards. The resulting glacial and non-glacial landforms, including moraines and river terraces allow the timing and extent of both glacial systems to be determined. This study focuses on developing a quantitative glacial stratigraphy using cosmogenic radionuclide surface exposure dating of moraines and river terraces and optically stimulated luminescence of terrace capping loess for the Nenana Valley that span beyond the last glacial cycle. This numerically dated chronology and the reconstruction of the extent of Quaternary glaciers in the Nenana Valley provides important insights into the dynamics of both glacial systems in central Alaska. Quantifying the nature of glaciation in this region allows comparisons with glacial chronologies in other regions of Alaska, which in turn is beginning to help define the nature of long-term Quaternary climate change in Alaska.