USING IN SITU 14C COSMOGENIC RADIONUCLIDE DATING TO DATE LANDSCAPE CHANGES IN EASTERN TAYLOR VALLEY, ANTARCTICA

Taylor Valley is a part of the McMurdo Dry Valleys; the largest ice-free oasis on the Antarctic mainland. Eastern Taylor Valley opens to the McMurdo Sound, which was occupied by the Ross Ice Sheet (RIS) during the last glaciation. The RIS advanced westward into Taylor Valley, facilitating the formation of a high level ice-dammed lake named Glacial Lake Washburn (GLW). The retreat of the RIS from Taylor Valley is thought to coincide with the end of GLW. In addition to recording movements of the RIS and paleo-lake level changes, the landscape of eastern Taylor Valley is dotted with alpine glaciers and streams, and records a dynamic history of interaction between all of these elements. Here, we use in situ 14C cosmogenic radionuclide dating to decipher this history, aiming to understand the order in which various landscape changes occurred and the timing of those occurrences. We find evidence that a north facing alpine glacier in eastern Taylor Valley retreated from its maximum position ~23.9 ka, that a major south facing alpine glacier remained at its maximum position until ~13.5 ka, and that stream channels along the north and south valley walls were down-cutting through RIS drift prior to 16.1 ka and 11.5 ka, respectively. These data place constraints on the timing of RIS retreat from its western limit in Taylor Valley, as well as the timing and spatial expanse of GLW highstands.