CLIMATE CHANGE DURING THE LAST PLEISTOCENE GLACIATION IN NORTHERN NEVADA INFERRED FROM NUMERICAL GLACIAL MODELING, ANGEL LAKE TYPE LOCALITY, EAST HUMBOLDT RANGE, NEVADA, U.S.A

Valley glaciers were abundant in the northern Great Basin region of Nevada during the last Pleistocene glaciation. In the East Humboldt Range, the type locality for the Angel Lake Glaciation (the last Pleistocene glaciation in the Great Basin), glacial deposits and landforms are well preserved and easily identifiable. Cosmogenic ¹⁰Be surface exposure dating of multiple moraine crests and glacially polished bedrock in the Angel Lake valley indicates that the Angel Lake Glaciation culminated prior to 20.1 ka and that ice disappeared from the valley at ca. 14.8 ka. The dated glacial records provide a useful chronological framework for inferring changes in climate from the pattern of ice retreat. To infer past climate changes, 2-D modeling of glacier mass balance and ice flow was used to reconstruct the known ice extents at steady state during the culmination of the Angel Lake Glaciation and during deposition of recessional moraines. Model experiments generated a set of precipitation and temperature combinations accompanying intervals of moraine deposition. These experiments indicate that if precipitation was at or near modern, then a temperature depression of ~9^°C accompanied deposition of the terminal moraine in the Angel Lake Valley. This result is consistent with findings of model experiments applied to glacial valleys in other mountains in northern Nevada and Utah. These and other inferences of paleoclimate support the hypothesis that, during the last glaciation, the Great Basin experienced a greater change in temperature or precipitation compared to neighboring regions in the western United States.