Evidence for rapid deglaciation between Tuolumne Meadows and Tioga Pass
The remarkably broad subalpine basin system extending from Tuolumne Meadows to Tioga Pass was sculpted by multiple, converging Tioga-age glaciers. The distinctive arrangement of glacial landforms in this area, and their sedimentary structures, informs a fundamental question regarding local ice-retreat dynamics: did LGM (Tioga) deglaciation in the Sierra Nevada occur rapidly by in situ melting and disintegration of ice, or slowly through gradual retreat (e.g., Clark, 1976)? Reconstructing the LGM deglaciation of the Tuolumne Meadows region requires a precise understanding of geomorphic adjustments recorded by patterns of erosion and sedimentation. We conducted new surficial geologic mapping by integrating field observations, analysis of lidar topographic data, and multi-proxy geochronologic investigations ( 10 Be, IRSL, Tephra, 14 C) to evaluate the exceptionally well-preserved glacial landforms and investigate the pace of deglaciation.