Assessing the effect of a major storm on 10BE concentrations and inferred basin-averaged denudation rates

Autor: Melissa A. Foster, Robert S. Anderson
Rok vydání: 2016
Předmět:
Zdroj: Quaternary Geochronology. 34:58-68
ISSN: 1871-1014
Popis: 10Be concentrations in stream sediments are commonly employed to calculate basin-averaged denudation rates. Such calculations assume that denudation is steady in time and that quartz is uniformly distributed in the watershed. The 10Be concentrations in stream sediments are assumed to represent a spatially and temporally averaged concentration, and therefore should not be affected by a discrete erosion event. The effect of such events on 10Be concentrations has been modeled, but has not been previously field-tested following a large precipitation event. In this study, we resampled stream sediments that had been previously analyzed to deduce basin averaged erosion rates in small, tributary basins in the Colorado Front Range following an extreme precipitation event in 2013. Most of our sample sites show no significant change between pre- and post-flood concentrations, and hence no change in the denudation rates inferred from them. The sample locations include a partially burned site, a debris flow site, and sites with very small drainage areas. A notable exception exists at lower Gordon Gulch, within the Boulder Creek Critical Zone Observatory; here, local 10Be data indicate that a large portion of flood-deposited sediment is likely derived from deep soils in fans, terraces, and fills, that are predominantly located on the north-facing toe slope. Overall, the reproducibility of denudation rates deduced from pre- and post-storm samples indicates that the uncertainty associated with 10Be-derived denudation rates is likely less than 15% in this setting.
Databáze: OpenAIRE
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