Chronology of the lost glacial maximum in the upper bear river basin, Utah

Published in:

Arctic Antarctic and Alpine Research 39,4 (2007) 537-548;


The headwaters of the Bear River drainage were occupied during the Last Glacial Maximum (LGM) by outlet glaciers of the Western Uinta Ice Field, an extensive ice mass (similar to 685 km(2)) that covered the western slope of the Uinta Mountains. A well-preserved sequence of latero-frontal moraines in the drainage indicates that outlet glaciers advanced beyond the mountain front and coalesced on the piedmont. Glacial deposits in the Bear River drainage provide a unique setting where both Be-10 C-14 dating of sediment cosmogenic surface-expo sure dating of moraine boulders and in Bear Lake downstream of the glaciated area set age limits on the timing of glaciation. Limiting C-14 ages of glacial flour in Bear Lake (corrected to calendar years using CALIB 5.0) indicate that ice advance began at 32 ka and culminated at about 24 ka. Based on a Bayesian statistical analysis of cosmogenic surface-expo sure ages from two areas on the terminal moraine complex, the Bear River glacier began approximately coincident with the start of its final retreat at about 18.7 to 18.1 ka, deglaciation elsewhere in the central Rocky Mountains and many other alpine glacial localities worldwide. Unlike valleys of the southwestern Uinta Mountains, deglaciation of the Bear River drainage began prior to the hydrologic fall of Lake Bonneville from the Provo shoreline at about 16 ka.


Environmental Sciences;; Geography, Physical

Date of this Version

January 2007

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