Preprints
https://doi.org/10.5194/gchron-2021-5
https://doi.org/10.5194/gchron-2021-5

  01 Mar 2021

01 Mar 2021

Review status: this preprint is currently under review for the journal GChron.

Erosion rates in a wet, temperate climate derived from rock luminescence techniques

Rachel K. Smedley1, David Small2, Richard S. Jones2,3, Stephen Brough1, Jennifer Bradley1, and Geraint T. H. Jenkins4 Rachel K. Smedley et al.
  • 1School of Environmental Sciences, University of Liverpool, Liverpool, UK
  • 2Department of Geography, Durham University, South Road, Durham, UK
  • 3School of Earth, Atmosphere and Environment, Monash University, Melbourne, Australia
  • 4Independent researcher: Powys, Wales, UK

Abstract. A new luminescence erosion-meter has huge potential for inferring erosion rates on sub-millennial scales for both steady and transient states of erosion, which is currently not possible with any existing techniques capable of measuring erosion. This study applies new rock luminescence techniques to a well-constrained scenario provided by the Beinn Alligin rock avalanche, NW Scotland. Boulders in this deposit are lithologically consistent, have known cosmogenic nuclide ages, and independently-derived Holocene erosion rates. We find that luminescence-derived exposure ages for the Beinn Alligin rock avalanche were an order of magnitude younger than existing cosmogenic nuclide exposure ages, suggestive of high erosion rates (as supported by field evidence of quartz grain protrusions on the rock surfaces). Erosion rates determined by luminescence were consistent with independently-derived rates measured from boulder-edge roundness. Inversion modelling indicates a transient state of erosion reflecting the stochastic nature of erosional processes over the last ~4 ka in the wet, temperate climate of NW Scotland. Erosion was likely modulated by known fluctuations in moisture availability, and to a lesser extent temperature, which controlled the extent of chemical weathering of these highly-lithified rocks prior to erosion. The use of a multi-elevated temperature, post-infra-red, infra-red stimulated luminescence (MET-pIRIR) protocol (50, 150 and 225 °C) was advantageous as it identified samples with complexities introduced by within-sample variability (e.g. surficial coatings). This study demonstrates that the luminescence erosion-meter can infer accurate erosion rates on sub-millennial scales and identify transient states of erosion (i.e. stochastic processes) in agreement with independently-derived erosion rates for the same deposit.

Rachel K. Smedley et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gchron-2021-5', Benjamin Lehmann, 25 Mar 2021
    • AC1: 'Reply on RC1', Rachel Smedley, 11 May 2021
  • RC2: 'Comment on gchron-2021-5', Anonymous Referee #2, 08 Apr 2021
    • AC2: 'Reply on RC2', Rachel Smedley, 11 May 2021
  • EC1: 'Associate editors comments on Smedley et al.', James Feathers, 12 Apr 2021
    • AC3: 'Reply on EC1', Rachel Smedley, 11 May 2021
  • EC2: 'Comment on gchron-2021-5', James Feathers, 15 May 2021
  • AC4: 'Comment on gchron-2021-5', Rachel Smedley, 27 May 2021

Rachel K. Smedley et al.

Rachel K. Smedley et al.

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Short summary
We apply new rock luminescence techniques to a well-constrained scenario of the Beinn Alligin rock avalanche, NW Scotland. We measure accurate erosion rates consistent with independently-derived rates and reveal a transient state of erosion over the last ~4,000 years in the wet, temperate climate of NW Scotland. This study shows that the new luminescence erosion-meter has huge potential for inferring erosion rates on sub-millennial scales, which is currently impossible with existing techniques.