Lowering Rates of Moraine Crests From Accumulation of Cosmogenic 36C1 and 10BE: Eastern Sierra Nevada, California

Abstract

The accumulation of in-situ 36Cl and 10Be in soils from the crests of 11 moraines near Bishop Creek, California was used to determine time-integrated erosion rates and exposure ages. Previous studies have provided the exposure history and estimates of erosion for the Bishop Creek moraine sequence allowing for the validation of the 36CV10Be model used in this study. With the two isotopes, simultaneous calculations of exposure ages and erosion rates of the soils have been made. Mean erosion rates of the soils calculated using 10Be correlate well with those calculated using 36Cl, and range from 19 to 62 mm/ky. Erosion rates from 10Be have larger uncertainties than those calculated using 36Cl and typically are slightly higher. Meteoric 10Be used in combination with the two in-situ isotopes yielded an average 10Be deposition rate (q) of 0.46 ± 0.16 x 106 atoms cm-2 yr-1, in agreement with previous estimates.