Ages and significance of glacial and mass movement deposits on the west side of Boulder Mountain, Utah, USA
Abstract Using air photos, satellite images, and field observations we mapped Quaternary glacial and mass movement deposits on the west side of Boulder Mountain in south-central Utah, USA. Prominent glacial moraines were deposited by outlet glaciers that emanated from an ice cap that existed atop Boulder Mountain. Cosmogenic 3 He exposure ages of these deposits range from 20.2 ± 1.5 to 22.5 ± 2.5 ka and indicate maximum ice advance during the global last glacial maximum (LGM). Three 3 He exposure ages of boulders from the Pine Creek slump deposit indicate that the slumping likely occurred at or before ∼ 125 ka. Eight 3 He exposure ages of boulders from the Miller Creek Potholes debris flow deposit range from 20.2 ± 2.0 to 50.4 ± 3.0 ka; five of those boulders yielded ages in the range of 26–33 ka and suggest emplacement of the debris flow deposit during that time. Both of these mass movement features cover prominent fault traces related to the Thousand Lakes fault but do not appear to be offset, suggesting that major faulting has not occurred since ∼ 125 kyr ago in this area.