LATE PLEISTOCENE CHRONOLOGY OF LAKE TERRETON, SOUTHEASTERN IDAHO

A better understanding of Late Pleistocene climate change in the western US is important because it can help to calibrate climate models that are designed to predict future changes caused by global warming. Shorelines of closed lake basins provide excellent climatic records, which are particularly good at recording the timing of high stands caused by wetter and/or cooler conditions. Lake Terreton was a large lake situated on the eastern Snake River Plain, an area with relatively few direct climate proxies. The lake occupied the Mud Lake and Big Lost Trough sub-basins around the time of the last glacial maximum. 35 samples of shoreline-proximal sands were collected from outcrops and hand-dug soil pits. Preliminary OSL ages for five of the samples indicate that the lake rose to its highest level at roughly 23 ka and experienced smaller high stands near 8 and 13 ka. The oldest high stand at 23 ka matches the timing of the Big Lost River Flood, which flowed into the Terreton Basin. This suggests the flood may have filled the Terreton basin to the point of overflow, causing an exceptionally large high stand. The younger high stands tentatively correlate with known climatic anomalies in the North Atlantic although additional work is required to better constrain the ages and place them in a regional context.