Timing of the last glaciation and subsequent deglaciation in the Ruby Mountains, Great Basin, USA

The timing of the last Pleistocene glaciation in western North America is becoming increasingly well understood, largely due to improved methods of obtaining numerical ages of glacial deposits and landforms. Among these, cosmogenic radionuclide surface-exposure dating has been widely applied to moraines of mountain glaciers, providing the framework for understanding terrestrial climate change during and since the last glaciation in western North America. During the Late Pleistocene, the Great Basin of the western United States hosted numerous mountain glaciers, the deposits of which can provide valuable records of past climate changes if their ages can be precisely determined. In this study, twenty-nine cosmogenic radionuclide 10Be surface-exposure ages from a suite of moraines in Seitz Canyon, western Ruby Mountains, limit the timing of the last glacial episode in the interior Great Basin, known as the Angel Lake Glaciation. Results indicate that deposition of a terminal moraine and two recessional moraines began just prior to ∼20.5 ka and continued until ∼20.0 ka. Retreat from the next younger recessional moraine began at ∼17.2 ka, and final deglaciation began at ∼14.8 ka. These ages are broadly consistent with cosmogenic surface-exposure ages from the eastern Sierra Nevada and the western Wasatch Mountains, in the western and eastern extremes of the Great Basin respectively. Furthermore, these ages suggest that the valley glacier in Seitz Canyon was at or near its maximum extent before and during the hydrologic maxima of Pleistocene lakes in the Great Basin, supporting previous suggestions that a cool and wet climate persisted in this region during the early part of the last glacial–interglacial transition.

► The last glaciation is limited by cosmogenic 10Be exposure dating of moraines. ► Results indicate that this event coincides with marine oxygen isotope stage 2. ► Timing and duration of this event are similar to Pinedale and Tioga Glaciations. ► Glacier maxima in the Great Basin overlapped with highstands of paleolakes.