Journal
EARTH SURFACE PROCESSES AND LANDFORMS
Volume 40, Issue 13, Pages 1719-1729Publisher
WILEY
DOI: 10.1002/esp.3748
Keywords
Be-10; erosion rate; lithology; Andes
Funding
- IRD
- French national research agency ANR [ANR-06-JCJC-0100]
- Agence Nationale de la Recherche (ANR) [ANR-06-JCJC-0100] Funding Source: Agence Nationale de la Recherche (ANR)
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Millennial catchment-mean erosion rates derived from terrestrial cosmogenic nuclides are generally based on the assumption that the lithologies of the parent rock each contain the same proportion of quartz. This is not always true for large catchments, in particular at the edge of mountainous plateaus where quartz-rich basement rocks may adjoin sedimentary or volcano-sedimentary rocks with low quartz content. The western Central Andes is an example of this type of situation. Different quartz contents may be taken into account by weighting the TCN production rates in the catchment. We recall the underlying theory and show that weighting the TCN production rate may also lead to bias in the case of a spatial correlation between erosion rate and lithology. We illustrate the difference between weighted and unweighted erosion rates for seven catchments (16 samples) in southern Peru and northern Chile and show variations up to a factor of 2 between both approaches. In this dataset, calculated erosion rates considering only granitoid outcrops are better correlated with catchment mean slopes than those obtained without taking into account the geological heterogeneity of the drained watershed. This dataset analysis demonstrates that weighting erosion rates by relative proportions of quartz is necessary to evaluate the uncertainties for calculated catchment-mean erosion rates and may reveal the correlation with geomorphic parameters. Copyright (c) 2015 John Wiley & Sons, Ltd.
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