Testing and refining the timing of hydrologic evolution during the latest Pleistocene regressive phase of Lake Bonneville

Lacustrine, fluvial, and wetland landforms present in the now desertified regions of Dugway Proving Ground (DPG) and the Sevier Desert in western Utah, record a fascinating history of falling lake level, river development, and establishment of wetland habitats in the Lake Bonneville basin between ∼13 and 9 ka. This was not only a time of rapid climate change but also of human occupation into suitable habitats made available by decline of the large lake. Using optically stimulated luminescence (OSL) dating methods we have determined depositional ages for sediment samples from bar features (reworked deltaic sands), braided fluvial channels, and topographically inverted fluvial channels collected from DPG. All samples analyzed showed good luminescence characteristics. An uncertainty estimate incorporated into Minimum Age Model analysis increased confidence in the equivalent dose (De) estimate for the majority of samples. OSL ages for five of six samples studied support the previously constructed model of overflow from the Sevier basin northwards to the Great Salt Lake basin at ∼12–13 ka and rapid regression of Lake Bonneville at this time.