Paper No. 302-8
Presentation Time: 10:45 AM
FEASIBILITY ANALYSIS OF COSMOGENIC ISOTOPE SURFACE EXPOSURE DATING OF GLACIAL DEPOSITS TO DETERMINE HOLOCENE GLACIAL CHRONOLOGY ON MOUNT RAINIER, WA
Mount Rainier glaciers supply many of the surrounding communities with water for consumption and for hydropower, and understanding past glacial change gives insight to future glacial change that will affect the quality of life of the residents of western Washington. This study analyzes the cosmogenic isotope surface exposure dating method for its feasibility of use on Mount Rainier because, while this is a powerful method commonly used to determine glacial history, many factors that make cosmogenic isotopes difficult to use converge on Mount Rainer. Through examination of glacier chronology literature, geologic maps, Google Earth imagery, Mount Rainier cosmogenic isotope dating literature, and cosmogenic correction factor literature this study suggest that cosmogenic isotope exposure dating can be used on Mount Rainier and that 3He is the best isotope to use. Three main advances, divided into five events, are common time periods where glaciers likely deposited moraines which now can be dated to determine glacial history: McNeeley 1 and 2 (13-10 ka), Burroughs Mountain (4-2.2 ka), and Older and Younger Garda (<2.2 ka). Important corrections include erosion, snow shielding, and moraine degradation for which this study suggests using a 2mm/ka erosion rate, the snow shielding model presented by Schilden et al. (2005), and the moraine degradation sampling parameters delineated in Putkonen et al. (2003).