GLACIER RESPONSE TO LATE GLACIAL ABRUPT CLIMATE EVENTS IN THE TETON RANGE, WYOMING, USA

The Last Deglaciation was characterized by abrupt climate oscillations driven primarily by ocean circulation changes in the North Atlantic. While evidence of these events—e.g., the Bølling-Allerød warming and the Younger Dryas cooling—has been documented across much of the northern hemisphere, their manifestation in the western U.S. is unclear. In particular, few glacial deposits in the western U.S. have been definitively correlated with the Younger Dryas using absolute dating techniques, and many sedimentary records are of insufficient resolution to adequately capture such short-lived events. Here, we combine high-resolution lake sediment analyses with cosmogenic ¹⁰Be dating to demonstrate that glaciers in the Teton Range, WY, retreated around the time of the Bølling-Allerød and readvanced during the Younger Dryas. ¹⁰Be ages from a recessional moraine and bedrock-perched boulders document the retreat of the Teton Glacier after ~15 ka. Following rapid glacier retreat, the Teton Glacier readvanced and formed a moraine that dates to within the Younger Dryas based on ¹⁰Be ages of moraine crest boulders. This moraine is positioned between the Little Ice Age moraine and Delta Lake, a small tarn that receives meltwater from the extant Teton Glacier. A ~16-m sediment core from Delta Lake extends to >13.6 ka and records this Younger Dryas readvance as demonstrated via sediment lithostratigraphy, grain size, clastic flux, and scanning XRF elemental abundances. This readvance is represented by >2 m of laminated glaciolacustrine sediment, creating a unique opportunity to assess the alpine glacier response to the Younger Dryas at high resolution. Lake records from nearby basins in Tetons that span the latest Pleistocene similarly record rapid glacier retreat through the Bølling-Allerød and enhanced glacial or paraglacial activity during the Younger Dryas, indicating that these were range-wide responses. Further investigation is required to determine whether the glacial/paraglacial readvances were due to summer cooling, increased winter precipitation, or some combination. In any case, these high-resolution sedimentary records and securely dated glacial deposits point to a strong link between North Atlantic–centered abrupt climate change events and alpine environments of the western U.S.