1. Basins and bedrock: Spatial variation in 10Be erosion rates and increasing relief in the southern Rocky Mountains, USA.
- Author
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Dethier, David P., Ouimet, Will, Bierman, Paul R., Rood, Dylan H., and Balco, Greg
- Subjects
- *
GEOLOGICAL basins , *BEDROCK , *EROSION , *SEDIMENTARY rocks , *PROTEROZOIC Era - Abstract
We used measurements of cosmogenic 10Be in alluvium to estimate erosion rates on a 103-104 yr time scale for small (0.01-47 km²), unglaciated basins in northern Colorado, southern Wyoming, and adjacent western Nebraska (western United States). Basins formed in Proterozoic cores of Laramide ranges are eroding more slowly (23 ± 7 mm k.y. -1, n = 19) than adjacent basins draining weakly lithified Cenozoic sedimentary rocks (75 ± 36 mm k.y. -1, n = 20). Erosion rates show a relationship to rock resistance and, for granitic rocks, to basin slope, but not to mean annual precipitation. We estimated longer-term (>105 yr time scale) erosion rates for the granitic core of the Front Range by measuring the concentration of 10Be and 26Al produced mainly by muon interactions at depths 1.7-10 m below the surface. Concentrations imply erosion rates of 9-31 mm k.y. -1, similar to shorter-term erosion rates inferred from alluvial sediment. The spatial distribution of erosion rates and stratigraphic evidence imply that relief in the southern Rocky Mountains increased in the late Cenozoic; modern relief probably dates from post-middle Miocene time. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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