MUNROE, Jeffrey S., Quaternary Research Group, Department of Geology & Geophysics, University of Wisconsin-Madison, 1215 W. Dayton St., Madison, WI 53706, jmunroe@geology.wisc.edu

The extent of possible Neoglacial ice in the Uinta Mountains is not well constrained.  However, recent radiocarbon dates indicate that at least three favorably oriented cirques did not contain ice during most of the Holocene.  Instead, the youngest, highest, moraines in these cirques record the action of ice masses that persisted, or re-formed, following the terminal Pleistocene deglaciation.
Dates of 9370 (plus or minus 70) and 8570 (70) 14C yr BP (10.4 to 10.3 ka and 9.6 to 9.5 ka BP) on Salix fragments from the base of a 4-m thick sedimentary sequence immediately behind a moraine dam near the head of the Henrys Fork provide a minimum age for a glacier that descended to 3273 m asl.  Due to the location of this exposure 3.7 km from the headwall, the presence of Neoglacial ice in the basin cannot be ruled out.  However, a date of 7310 (70) 14C yr BP (8.1 to 8.0 ka BP) from the base of another section at the head of the basin indicates that any Neoglacial ice in the Henrys Fork must have been quite limited in extent.
Dates of 8950 (70) and 8730 (90) 14C yr BP (10.2 to 9.9 ka and 9.9 to 9.6 ka BP) on wood fragments from the base of a colluvial basin fill behind the highest moraine (3200 m asl) at the head of the East Fork of Bear River above Allsop Lake indicate that glaciers failed to reoccupy that cirque during the Neoglaciation.
Dates from a 270-cm long core from Hacking Lake at the eastern end of the glaciated Uintas also preclude Neoglacial ice at the head of the North Fork of Ashley Creek.  A date of 5495 (75) 14C yr BP (6.2 to 6.4 ka BP) on organic fragments from 162 cm below the sediment-water interface, along with three younger dates from higher levels in the core, indicate that the cirque has been free of glacial ice for at least the last 6 ka.

Uinta Mountains, Neoglaciation