Don R. Currey Memorial Field Trip to the shores of Pleistocene Lake Bonneville

Chronology of latest Pleistocene mountain glaciation in the western Wasatch Mountains, Utah, U.S.A.

“…Although the timing of the Lake Bonneville highstand is well established, the age of the underlying till is limited only by its weathering characteristics (Scott et al, 1983) and by correlations to nearby settings where age limits are available (Madsen and Currey, 1979). Additionally, some recent reports include observations of till overlying shoreline gravels of Lake Bonneville at the western front of the Wasatch Mountains (Personius and Scott, 1992;Godsey et al, 2005b), thereby indicating multiple ice advances to the mouth of Little Cottonwood Canyon. However, as noted above, whether the till underlying shoreline gravels was deposited during MIS 2 or an earlier interval of the late Pleistocene cannot be discerned from the available data.…”

“…If the glacier in Little Cottonwood Canyon deposited a terminal moraine prior to the Bonneville highstand, then the moraine may have been eroded away by wave action along the shore of Lake Bonneville (as suggested by previous studies), and the remnant of this moraine may be the Pinedale-equivalent till that extends beyond the terminal moraines at the mouth of the canyon. If the stratigraphic observations of Godsey et al (2005b) are accurate, the glacier then deposited the right-lateral sector of the terminal moraine after the Bonneville highstand (and above its shoreline elevation of~1550 m asl) before beginning its final retreat. Based on glacial geomorphic evidence at American Fork Canyon, it is unclear whether the glacier would have persisted at the terminal moraine during the Bonneville highstand (18.7 to 17.6 cal ka BP) or readvanced to the terminal moraine prior to 15.7 ± 1.3 ka; the former seems more likely considering that mountain glaciers occupied terminal moraines in the nearby Uinta Mountains during this time (Laabs et al, 2009).…”

“…Some recent observations suggest that glaciers occupied the mouth of Little Cottonwood and Bells Canyons after the Bonneville highstand. Godsey et al (2005b) document till overlying and underlying shoreline gravels of Lake Bonneville exposed in trenches excavated at the toe of the right-lateral sector of the terminal moraine at Little Cottonwood Canyon (Fig. 1).…”