We have used cosmogenic 36 Cl surface exposure dating to deterime apparent construction ages of late Pleistocene moraines in the Sierra Nevada, the White Mountains, and the Wind River Range, all in the western United States. This is due either to unfavorable conditions for glacier development at some times or to obliteration of earlier deposits by later, more extensive glaciers.
Most moraines have young apparent exposure ages, with only a few older than the last glacial cycle.
This may be due to young true ages of these deposits, erosion of moraine surfaces, or obliterative overlap and covering of older deposits by younger ones. Similarly, some previously uncorrelated deposits have the same exposure ages and may be correlative. These clusters suggest that alpine moraines are formed during short deposition episodes that last between several hundred and several thousand years.