Relative and Numeric Age Data for Pleistocene Glacial Deposits and Diamictons in and near Sinks Canyon, Wind River Range, Wyoming, U.S.A

Abstract

Glacial deposits are identified from within and near Sinks Canyon, southwest of Lander, Wyoming, representing 6 first-order Pleistocene glaciations. Relative-age analyses of the deposits (including moraine morphology and soil development characteristics) indicate that they correspond to 4 glaciations previously identified from the Wind River Range (Pinedale, Early Wisconsin, Bull Lake, and Sacagawea Ridge) and to 2 older glacial events (Younger and Older Pre–Sacagawea Ridge). 10Be and 26Al exposure ages associated with recessional Pinedale deposits are similar to those associated with recessional Pinedale deposits elsewhere in the range. 10Be and 26Al exposure ages also support the identification of Early Wisconsin deposits here. The Early Wisconsin deposits represent the second locality where O-isotope stage 4 glacial deposits are described from the Wind River Range. Preliminary analysis of 10Be exposure data from the Older Pre–Sacagawea Ridge deposit suggests that a glacial advance occurred here before O-isotope stage 18 (>800 ka). If true, then Sinks Canyon contains the most complete record to date of glaciation in the Wind River Range and the only reported record of Pleistocene glaciation prior to O-isotope stage 18 in the Rocky Mountains.