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A note on 10 Be‐derived mean erosion rates in catchments with heterogeneous lithology: examples from the western Central Andes
Author(s) -
Carretier Sebastien,
Regard Vincent,
Vassallo Riccardo,
Martinod Joseph,
Christophoul Frederic,
Gayer Eric,
Audin Laurence,
Lagane Christelle
Publication year - 2015
Publication title -
earth surface processes and landforms
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.294
H-Index - 127
eISSN - 1096-9837
pISSN - 0197-9337
DOI - 10.1002/esp.3748
Subject(s) - lithology , geology , erosion , sedimentary rock , drainage basin , outcrop , structural basin , weighting , sedimentary basin , cosmogenic nuclide , quartz , geomorphology , bedrock , geochemistry , physical geography , hydrology (agriculture) , soil science , paleontology , geography , medicine , physics , cosmic ray , astrophysics , radiology , cartography , geotechnical engineering
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 © 2015 John Wiley & Sons, Ltd.