Eight uncorrected 36Cl ages for Pinedale boulders in north-central Colorado fall in the range 16.5 to 20.9 kyr. 10Be age determinations on four of five boulders are in close agreement (less-than-or-equals, slant6% difference) with 36Cl determinations. Hypothetical corrections for snow shielding increased the 36Cl ages of Pinedale boulder surfaces by an average of not, vert, similar12%. Most ages for pre-Pinedale (Bull Lake) boulders fall within marine-isotope stage (MIS) 5, a time when continental and Sierran ice accumulations were small or nonexistent. Under the assumption that these boulders were deposited on moraines that formed before the end of MIS 6 (not, vert, similar140 kyr BP), calculations indicated that rock-surface erosion [...]
