BE-10 DATING OF THE DURATION AND RETREAT OF THE LAST PINEDALE GLACIALSEQUENCE

Accurate terrestrial glacial chronologies are needed for comparison wi th the marine record to establish the dynamics of global climate chang e during transitions from glacial to interglacial regimes. Cosmogenic beryllium-10 measurements in the Wind River Range indicate that the la st glacial maximum (marine oxygen isotope stage 2) was achieved there by 21,700 +/- 700 beryllium-10 years and lasted 5900 years. Ages of a sequence of recessional moraines and striated bedrock surfaces show th at the initial deglaciation was rapid and that the entire glacial syst em retreated 33 kilometers to the cirque basin by 12,100 +/- 500 beryl lium-10 years.