Cosmogenically enabled sediment budgeting.

We used 10Be and 26Al to constrain the millennial-scale sediment and nuclide budget for a common, long-studied, but poorly understood landform in arid regions, the desert piedmont. We sampled the Chemehuevi Mountain piedmont, a complex multisurfaced landform in the Mojave Desert, western United States. The nuclide data indicate that sediment is produced more rapidly (1.1 × 105 kg·yr-1·.km-2) in steep mountain source basins than on the low-gradient pediment (4.0 × 104 kg·yr-1·km-2) or the intrapiedmont mountain range (2.5 × 104 kg·yr-1·km-2). However, the bulk of the sediment in transport is derived from erosion of the large abandoned alluvial surface (3.9 × 104 kg·yr-1·km-2). The combination of mass and nuclide budgeting suggests that sediment transport speeds decrease downslope from tens of meters per year in confined channels on the proximal pediment to decimeters per year in unconfined distributaries on distal wash surfaces. The sediment and nuclide budgeting approach we use is particularly valuable in arid regions where geomorphically significant events are infrequent and dating control is poor, thus confounding traditional sediment-budgeting techniques. [ABSTRACT FROM AUTHOR]