LATE PLEISTOCENE GLACIATION OF THE EAST BECKWITH MOUNTAIN AREA, WEST ELK MOUNTAINS, COLORADO

A complex late-Pleistocene alpine glacier system was reconstructed in the West Elk Mountains of south-central Colorado. The boundaries of the glacier were drawn by mapping terminal and lateral moraines and striated, plucked, and scoured bedrock. The paleo-ELA was determined to be 3170 m by locating the boundary between the erosional features created within the accumulation zone and the depositional features created within the ablation area of the ice system. Mapping and theoretical considerations indicate that the ice system was much larger and more complex than orginally thought. The field reconstruction was modified by mass balance and basal shear stress calculations. This resulted in a model that included ice flow that originated off a high source area atop Storm Ridge and extended through passes both to the east and west of East Beckwith Mountain. The large system was supported by a north-facing aspect as well as high local rates of accumulation.