SPATIAL AND TEMPORAL PATTERNS OF LATE PLEISTOCENE GLACIATION IN THE LEMHI RANGE, EAST-CENTRAL IDAHO

Patterns of Late Pleistocene mountain glaciation across the western United States have long been a point of contention. Mountain glacier systems across the western United States have experienced variable maximum ice extent before, during, and after the Last Glacial Maximum (LGM, ca. 18-24 ka). This poses a regional asynchrony in the timing of maximum ice extent across mountain glacier systems during this time. In addition, it has been thought that mountain glacier maximum ice extent is coeval with the maximum ice sheet extents during marine isotope stages 2 and 6. When the timing and intensity of glaciation before, during, and after the LGM is further constrained, we will better understand the climatic drivers of regional glaciation in space and time.

This study will elucidate the paleoclimatic conditions that produced extensive mountain glaciers in east-central Idaho. The semi-arid nature of the Lemhi Range, Idaho, suggests low intensity past glaciation and should thus provide detailed records of climatic fluctuations through the Late Pleistocene. I will generate a surficial geologic map of Late Pleistocene glacial and alluvial deposits. This map will establish ice limits, providing the basis for glacier reconstructions and the calculation of Pleistocene equilibrium-line altitudes, which in turn will yield possible precipitation-temperature relationships during the glacial events. Application of Optically Stimulated Luminescence and Cosmogenic Radionuclide dating techniques is essential to develop a chronology of glaciation and understand the drivers of spatial and temporal patterns of glaciation. New chronologies extracted from the Lemhi Range will fill an important gap between maritime and inland glacier records by identifying responses to climate change before and during the LGM.