A Holocene Chronology of Alpine Glaciation for the Western United States

Our research will develop a Holocene glacial chronology based on cosmogenic dating of boulders from moraine crests at several sites across the western United States. The chronology will address spatial and temporal glacier variability in response to postulated Holocene climate forcings. A number of studies have interpreted several Holocene glacial advances in the western U.S. (e.g., LIA, Neoglacial, Early-Holocene) (see, Burke and Birkeland, 1983; Davis, 1988 and Osborn and Bevis, 2001) but age control is based largely on relative dating techniques. Surface exposure dating using cosmogenic nuclides now provides a robust method to reevaluate and re-date several of these poorly defined glacial chronologies and develop a high-precision glacial record across the western U.S. for the Holocene epoch. Development of this chronology will provide new constrains on the extent of major Holocene climate forcings and their effects on the mass balance of western North America alpine glaciers as well as providing a better framework for understanding climate forcing during deglaciation. We will present initial data from three cirque moraines in the Medicine Bow Mountains, Wyoming as well as ongoing and future work in the western United States.