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Rapid thinning of the Welsh Ice Cap at 20–19 ka Based on 10Be Ages

Published online by Cambridge University Press:  20 January 2017

Philip D. Hughes ,
Neil F. Glasser  and
David Fink
Philip D. Hughes*
Affiliation:
Geography, School of Environment, Education and Development, University of Manchester, Manchester M13 9PL, England, UK
Neil F. Glasser
Affiliation:
Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth SY23 3DB, Wales, UK
David Fink
Affiliation:
Australian Nuclear Science and Technology Organisation, PMB1, Menai, NSW 2234, Australia
*
⁎Corresponding author. E-mail address:Philip.hughes@manchester.ac.uk (P.D. Hughes).
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Abstract

New 10Be ages from the summits of three mountain areas of North Wales reveal a very similar exposure timing as the Welsh Ice Cap thinned after the global Last Glacial Maximum. Eight bedrock and one boulder sample gave a combined arithmetic mean exposure age of 19.08 ± 0.80 ka (4.2%, 1σ). Similar exposure ages over a 320 m vertical range (824 to 581 m altitude) show that ice cap thinning was very rapid and spatially uniform. Using the same production rate and scaling scheme, we recalculated six published 10Be exposure ages from the nearby Arans, which also covered a similar elevation range from 608 to 901 m and obtained an arithmetic mean of 19.41 ± 1.45 ka (7.5%, 1σ). The average exposure age of all 15 accepted deglaciation ages is 19.21 ± 1.07 (5.6%, 1σ). The complete dataset from North Wales provides very strong evidence indicating that these summits became exposed as nunataks at 20–19 ka. This result provides important insight to the magnitude of ice surface lowering and behavior of the Welsh Ice Cap during the last deglaciation that can be compared to other ice masses that made up the British-Irish Ice Sheet.

Keywords

Welsh Ice CapNunatak10BeCosmogenic exposure datingRhinogsMoelwynsArenigsDeglaciation
Type
Original Articles
Information
Quaternary Research , Volume 85 , Issue 1 , January 2016 , pp. 107 - 117
Copyright
University of Washington

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