This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Recent developments in the understanding of Pleistocene glacial records in the western U.S. reveal spatial variability in the onset of the last glacial-interglacial transition (GIT; the time ~17-10 ka) among the northern, middle, southern Rocky Mountains, and the central Colorado Plateau. Such variability may reflect differences in precipitation among these areas caused by shifts in the location of the polar jet and accompanying storm tracks, or possibly the importance of Great Basin pluvial lakes as moisture sources for downwind mountain ranges. In determining the extent, timing, and chronology of glacier and lake fluctuations in the north-central Great Basin, this project fills a broad spatial gap in the understanding of glacial and paleoclimate history in the western U.S., and provides a much needed addition to climate records used to validate regional climate models. Intellectual Merit: Numerous mountain ranges and intermountain valleys in the north-central Great Basin contain abundant evidence of glacier and pluvial-lake fluctuations during the last GIT. However, the timing of glacier and lake responses to climate changes during this transition is virtually unknown in this region, and the nature of temperature and/or precipitation changes during this interval of profound climate change is poorly understood. Using glacier and pluvial-lake records from this region to infer climate changes during the Latest Pleistocene is of great current interest for several reasons. First, the location of the Great Basin, central among well-dated glacial and pluvial-lake locales in the interior western U.S., provides significant potential for examining the response of climate-sensitive, small glaciers and lakes to climate changes associated with the retreat of North American ice sheets and accompanying reorganization of regional-scale atmospheric circulation. Second, the excellent preservation of glacial and pluvial-lake deposits provides ideal targets for cosmogenic-surface exposure dating and optically-stimulated luminescence (OSL) dating. Finally, the proximity of mountain glaciers to closed-basin pluvial lakes during the last GIT affords a rare setting in which combined numerical modeling of glacier and lake mass balance can be used to set narrow limits on paleo-temperature and precipitation. Broader Impacts: This research is carried out by faculty from two predominantly undergraduate institutions, and all aspects of field and analytical work are aided by student researchers from Middlebury College and SUNY Geneseo. Maps produced through this project are published by the Nevada Bureau of Mining and Geology, making the glacial history of these popular areas available to recreational users. EarthCache sites are in development for the Nevada Bureau of Mining and Geology website to provide information about the geology and Quaternary history of popular localities in the study area. Additionally, mapping and all other results are provided to the USDA-Forest Service, the Bureau of Land Management, and the National Park Service, which manage nearly all of the proposed study areas.
