COSMOGENIC EXPOSURE DATING OF LATE PLEISTOCENE MORAINES IN THE TAYLOR RIVER DRAINAGE, SOUTHERN SAWATCH RANGE, COLORADO

Recent terrestrial cosmogenic nuclide (TCN) 10Be exposure age dating of terminal and recessional moraines within the Taylor River drainage expands upon decades of research aimed to map, model, and date the culmination and retreat of the Taylor River Glacier Complex (TRGC). At its terminal extent the TRGC, fed by the Taylor River and the Bowman, Pine, Tellurium, Italian, and Red Mountian Creek Drainages, covered an area of ~215 km². The TRGC was ~22 km long at its maximum, and past findings have suggested that it remained at near maximum extents for approximately 6 kyr. Retreat of the TRGC was punctuated by multiple standstills or readvances as indicated by the presence of at least 9 recessional moraines. Past TCN dating has primarily aimed to discern the timing of terminal moraine emplacement for the TRGC and neighboring valley glaciers. Twenty new samples were collected for TCN ¹⁰Be dating from five moraine surfaces within the Taylor River valley. Sampled moraines include the terminal and four recessionals, representing ice retreats of ~10%, ~20%, ~40%, and ~60% from terminal position. Reported exposure ages further limit the timing of glacier retreat within the TRGC.