Glacial Chronology of a High Altitude Moraine Series, Tamarack Bench/Francis Canyon, Sierra Nevada, California

Alpine glaciers in the Sierra Nevada are sensitive to regional climate fluctuations and preserve a high resolution record of climate change in the form of glacial deposits (surficial and lacustrine). Fluctuations of alpine glaciers signify shifts in precipitation and temperature. Developing a regional chronology of changes will enable correlation to regional and global climate records, assist in understanding the mechanisms behind these shifts, and help predict possible future changes. A chronology of a high altitude moraine series on the Tamarack Bench /Francis Canyon, eastern Sierra Nevada showing a complex late Pleistocene retreat during MIS 2 was developed through mapping and dating of 3 glacial deposits: TBm2 (18.8 ka), FLm2 (16.6 ka), and FCm3 (12.6 ka) using terrestrial cosmogenic nuclide 10Be. Currently no standard practice exists for interpretation of cosmogenic nuclide ages creating problems with correlation. Here I present a method of interpretation through application to our data and critical evaluation of current regional studies. Attempts at resolving the timing of the regional Recess Peak advance in the Sierra Nevada using only TCNs will be unsuccessful until accuracy improves.