Cosmogenically enabled sediment budgeting

We used 10 Be and 26 Al to constrain the millennial-scale sedi- ment 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 multi- surfaced landform in the Mojave Desert, western United States. The nuclide data indicate that sediment is produced more rapidly (1.1 3 10 5 kg·yr 21 ·km 22 ) in steep mountain source basins than on the low-gradient pediment (4.0 3 10 4 kg·yr 21 ·km 22 ) or the intra- piedmont mountain range (2.5 3 10 4 kg·yr 21 ·km 22 ). However, the bulk of the sediment in transport is derived from erosion of the large abandoned alluvial surface (3.9 3 10 4 kg·yr 21 ·km 22 ). 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 sed- iment and nuclide budgeting approach we use is particularly valu- able in arid regions where geomorphically significant events are infrequent and dating control is poor, thus confounding traditional sediment-budgeting techniques.