TETON GLACIER FLUCTUATIONS DURING THE LATEST PLEISTOCENE AS RECONSTRUCTED FROM DELTA LAKE SEDIMENTS, GRAND TETON NATIONAL PARK, WYOMING

Alpine glaciers are sensitive to climate change and records of their past fluctuations are valuable sources of paleoclimate data. This project aims to reconstruct changes in glacier extent during the latest Pleistocene (from approximately 14,000 years ago to 11,000 years ago) in the Teton Range, Wyoming, using sediments preserved at Delta Lake (2755 m asl; 0.02 km²; max depth, ~8.0 m), a glacial tarn positioned approximately 1 km below the Teton and Dike glaciers in the central Tetons. Previous work at this site demonstrates that changes in upstream glacier extent are faithfully recorded at Delta Lake through changes in sediment physical and geochemical parameters (Larsen et al., 2020, Sci. Adv.). Here, we extend this earlier record to roughly 14 ka by analyzing a new set of sediment cores collected in 2021. Radiocarbon dating of terrestrial macrofossils and the position of the Glacier Peak ash layer (13.6 ka) confirm the lake was deglaciated shortly before 14 ka and provide a secure geochronology. To track past glacier changes, we analyze a suite of glacier indicators, including sediment bulk density, magnetic susceptibility, total organic matter content, sXRF elemental composition, clastic sediment flux, and grain size distributions, at multi-decadal resolution. Sediment characteristics at the start of the sequence suggest a period of variable glacier extent from the base of the record until approximately 13 ka. All glacier proxies indicate a subsequent glacier advance and prolonged high stand spanning the Younger Dryas interval, prior to rapid retreat at the start of the Holocene. These data suggest glaciers in the Teton Range were responsive to global climate changes during the latest Pleistocene. We present the Delta Lake record within the context of existing temperature and precipitation reconstructions from the western US with the goal of understanding how alpine environments in this region responded to climate changes during the last glacial-interglacial transition. Results from this study may improve predictions of future glacial fluctuations in the Tetons and other alpine regions in the western US.