Abstract

Glacial deposits on the north slope of the Uinta Mountains were investigated through map and air photo interpretation combined with field mapping. Deposits representing the Smiths Fork (local Pinedale equivalent), Blacks Fork (Bull Lake equivalent) and pre-Blacks Fork Glaciations are present in the form of terminal and lateral moraines, ground moraine, and outwash valley trains. Nineteen separate valley glaciers covering ~940 km² were present in the northern Uinta Mountains during the peak of the Smiths Fork Glaciation. Ice cover was even more extensive (~1100 km²) during the penultimate Blacks Fork Glaciation. Distinct patterns of glaciation are evident from east to west along the north slope. Smiths Fork-age deposits in the Ashley Creek/Carter Creek/Sheep Creek region at the eastern end of the north slope indicate extensive ice stagnation. In contrast, Smiths Fork-age glaciers at the western end did not stagnate, and retreated actively after formation of their terminal moraines. In the central part of the north slope, bedrock structure apparently exerted a strong control on glacier dynamics in the Burnt Fork/Beaver Creek/Henrys Fork region. Reconstructed glacier equilibrium line altitudes for the Smiths Fork Glaciation drop dramatically at the western end of the range, indicating that glaciers in the western Uintas received considerably more precipitation than those farther east, probably due to lake effect snow derived from pluvial Lake Bonneville. Many drainages also contain small cirque-floor moraines indicating glacier advances after the Smiths Fork Glaciation, likely during the latest Pleistocene/early Holocene. Two drainages also contain evidence for Neoglaciation in the late Holocene, but before the classic Little Ice Age.