Rapid age assessment of glacial landforms in the Pyrenees using Schmidt hammer exposure dating (SHED)

  • Matt D. Tomkins, Jason M. Dortch, Philip D. Hughes, Jonny J. Huck, Andrew G. Stimson, Magali Delmas, Marc Calvet, Raimon Pallàs
  • Quaternary Research, April 2018, Cambridge University Press
  • DOI: 10.1017/qua.2018.12

The Schmidt Hammer can be used to reconstruct the glacial history of the Pyrenees

What is it about?

We sampled dated glacial surfaces (moraine boulders/ice sculpted bedrock) using the Schmidt Hammer and compared the results to 10Be ages. We show a clear non-linear relationship (R2 = 0.96, P < 0.01) between exposure age (i.e. how long the rock has been uncovered) and the degree of weathering (i.e. Schmidt Hammer R-values). This relationship permits the exposure age of a surface to be estimated using the Schmidt Hammer; a technique which is rapid, cost-effective and of comparable accuracy to radiometric dating techniques. To demonstrate this, we sampled 100 surfaces in a glacial catchment in the eastern Pyrenees. Our data record glacial retreat over he last ~50,000 years, are stratigraphically correct and are supported by independent radiometric ages.

Why is it important?

Our work builds on previous applications of this technique in the British Isles and demonstrates that Schmidt Hammer exposure dating (SHED) can be applied successfully in contrasting climatic regimes and that equivalent time-dependent weathering of granite surfaces can occur within regions of similar climate. Our method is based on a large age control data (n = 52) which has been shown to produce robust ages for glacial landforms. This work is important because our rapid, cost-effective technique could be applied widely to landforms across the Pyrenees to generate a wealth of new chronological data related to glacier dynamics over the last ~50 ka. Reconstructing the retreat history of palaeo-glaciers is crucial to understanding the climatic, glaciological and topographic controls on glacier advance/retreat. This information provides the foundation for models of future glacier behavior in response to anthropogenic climate change.

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