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Fast long-term denudation rate of steep alpine headwalls inferred from cosmogenic 36Cl depth profiles


Mair, David; Lechmann, Alessandro; Yesilyurt, Serdar; Tikhomirov, Dmitry; Delunel, Romain; Vockenhuber, Christof; Akçar, Naki; Schlunegger, Fritz (2019). Fast long-term denudation rate of steep alpine headwalls inferred from cosmogenic 36Cl depth profiles. Scientific Reports, 9(1):11023.

Abstract

Quantifications of in-situ denudation rates on vertical headwalls, averaged over millennia, have been thwarted because of inaccessibility. Here, we benefit from a tunnel crossing a large and vertical headwall in the European Alps (Eiger), where we measured concentrations of in-situ cosmogenic 36Cl along five depth profiles linking the tunnel with the headwall surface. Isotopic concentrations of 36Cl are low in surface samples, but high at depth relative to expectance for their position. The results of Monte-Carlo modelling attribute this pattern to inherited nuclides, young minimum exposure ages and to fast average denudation rates during the last exposure. These rates are consistently high across the Eiger and range from 45 ± 9 cm kyr−1 to 356 ± 137 cm kyr−1 (1σ) for the last centuries to millennia. These high rates together with the large inheritance point to a mechanism where denudation has been accomplished by frequent, cm-scale rock fall paired with chemical dissolution of limestone.

Abstract

Quantifications of in-situ denudation rates on vertical headwalls, averaged over millennia, have been thwarted because of inaccessibility. Here, we benefit from a tunnel crossing a large and vertical headwall in the European Alps (Eiger), where we measured concentrations of in-situ cosmogenic 36Cl along five depth profiles linking the tunnel with the headwall surface. Isotopic concentrations of 36Cl are low in surface samples, but high at depth relative to expectance for their position. The results of Monte-Carlo modelling attribute this pattern to inherited nuclides, young minimum exposure ages and to fast average denudation rates during the last exposure. These rates are consistently high across the Eiger and range from 45 ± 9 cm kyr−1 to 356 ± 137 cm kyr−1 (1σ) for the last centuries to millennia. These high rates together with the large inheritance point to a mechanism where denudation has been accomplished by frequent, cm-scale rock fall paired with chemical dissolution of limestone.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Geography
Dewey Decimal Classification:910 Geography & travel
Uncontrolled Keywords:Multidisciplinary
Language:English
Date:30 July 2019
Deposited On:06 Jan 2020 11:29
Last Modified:06 Jan 2020 11:38
Publisher:Nature Publishing Group
ISSN:2045-2322
OA Status:Gold
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1038/s41598-019-46969-0
Project Information:
  • : FunderSNSF
  • : Grant IDCR22I2_159299
  • : Project TitleDevelopment and scientific application of nuclear emulsion particle detectors to geological problems in 3D

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