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The Last Glacial Maximum (LGM) in the Rocky Mountain region occurred about 21 ka (20,000 years before present). However, dated glacial chronologies suggest that while LGM glacier advances in individual ranges in Colorado were somewhat synchronous, retreat from their maximum extents was asynchronous, varying between ~20 and 15 ka or later. The precise timing and spatial variation of glacier advance and retreat provides insights into LGM climate change and is necessary to calibrate climate models. To better understand the timing of the LGM in the Mosquito Range in Colorado, we collected 12 samples from granitic boulders on moraine crests in the summer of 2016. Sample processing began in Fall 2016. Samples were crushed, sieved and subject to magnetic separation. Chemical processing is underway to further separate quartz grains, and ultimately to extract beryllium oxide (BeO) “targets.” Target will be analyzed for the concentration of 10Be, a cosmogenically-produced isotope, using accelerator mass spectrometry at PRIME Lab (Purdue University). 10Be concentrations will then be used to determine the age of the moraines and thus reveal the timing of the local LGM.
Last Glacial Maximum, Rocky Mountains, Mosquito Range (Colo.), Moraines, Glaciers
Geology | Glaciology
Bensen, Noah and Brugger, Keith A., "Toward the Development of a 10Be Chronology of Glaciation in the Mosquito Range, Colorado: A Progress Report" (2017). Undergraduate Research Symposium 2017. 10.