QUESTION
Surface Processes on Simple Wash Dominated Piedmont Surfaces.
For a detailed analysis of this project read our manuscript published in Geomorphology.
QUESTION
How long do you think it takes sediment to go from the rangefront to the bottom of the piedmont? This is the question that spurred me to study the long-term sediment transport down desert piedmonts.
METHODS
I collected 10Be and 26Al to use as tracers as sediment moves down piedmont. I collected sediment at 21 collection locations along 4 km long transects and amalgamated the sediment. The transects were spaced at 1 km intervals from the rangefront.
I collected sediment from three drainage basins to estimate the sediment yield from the drainage basins using 10Be and 26Al. The average sediment yields are 0.01 g cm-2 y-1 and average basin-wide lowering rates are 30 to 40 mm ky-1.
I collected depth profiles from two soil pits on the Iron Mountain piedmont to determine the depositional history.
RESULTS
Sediment moving down both the Iron and Granite Mountain piedmonts is dosed in a regular fashion.
The piedmonts were recently depositional systems (at 15 and 40 m Ma-1, respectively for Pit 1 and Pit 2) until between 8,500 and 12,800 years ago when deposition stopped.
Using a mass balance approach we determined average sediment velocities between ~ 20 cm per year and 100 cm per year.