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Slow regolith degradation without creep determined by cosmogenic nuclide measurements in Arena Valley, Antarctica

Published online by Cambridge University Press:  20 January 2017

Jaakko Putkonen*
Affiliation:
Department of Earth and Space Sciences, MS 351310, University of Washington, Seattle, WA 98195, USA
Greg Balco
Affiliation:
Department of Earth and Space Sciences, MS 351310, University of Washington, Seattle, WA 98195, USA
Daniel Morgan
Affiliation:
Department of Earth and Space Sciences, MS 351310, University of Washington, Seattle, WA 98195, USA
*
*Corresponding author.E-mail address: putkonen@u.washington.edu (J. Putkonen).

Abstract

Estimates of regolith degradation in the McMurdo Dry Valleys of Antarctica are currently based on indirect evidence and ancient ashes at or near the soil surface that suggest excellent preservation of surfaces. On the other hand, the existing cosmogenic-nuclide surface exposure ages from many parts of the Dry Valleys are younger than the age of surface deposits inferred from stratigraphic relations. This suggests some combination of surface erosion or past ice cover, both of which would reduce the apparent exposure age. This paper quantifies the regolith degradation and/or past ice cover by measuring10Be and26Al from a landslide deposit that contains 11.3 Ma volcanic ash. The surface sample yields an apparent exposure age of only 0.4 Ma. However, measurements of the subsurface nuclide concentrations show that the deposit has not been shielded by ice, and that the age of the ash does not conflict with the apparent exposure age when slow degradation of the deposit (2 m Ma−1) is taken into account. Soil creep, which is a common degradational process in a wide variety of environments, is non-existent at this field site, which likely reflects the persistent lack of bio- and cryoturbation.

Information

Type
Research Article
Copyright
University of Washington

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