Cosmogenic exposure age constraints on deglaciation and flow behaviour of a marine-based ice stream in western Scotland, 21–16 ka

Small, D., Benetti, S., Dove, D., Ballantyne, C. K., Fabel, D. , Clark, C. D., Gheorghiu, D. M. , Newall, J. and Xu, S. (2017) Cosmogenic exposure age constraints on deglaciation and flow behaviour of a marine-based ice stream in western Scotland, 21–16 ka. Quaternary Science Reviews, 167, pp. 30-46. (doi:10.1016/j.quascirev.2017.04.021)

Small, D., Benetti, S., Dove, D., Ballantyne, C. K., Fabel, D. , Clark, C. D., Gheorghiu, D. M. , Newall, J. and Xu, S. (2017) Cosmogenic exposure age constraints on deglaciation and flow behaviour of a marine-based ice stream in western Scotland, 21–16 ka. Quaternary Science Reviews, 167, pp. 30-46. (doi:10.1016/j.quascirev.2017.04.021)

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Abstract

Understanding how marine-based ice streams operated during episodes of deglaciation requires geochronological data that constrain both timing of deglaciation and changes in their flow behaviour, such as that from unconstrained ice streaming to topographically restricted flow. We present seventeen new 10Be exposure ages from glacial boulders and bedrock at sites in western Scotland within the area drained by the Hebrides Ice Stream, a marine-based ice stream that drained a large proportion of the former British-Irish Ice Sheet. Exposure ages from Tiree constrain deglaciation of a topographic high within the central zone of the ice stream, from which convergent flowsets were produced during ice streaming. These ages thus constrain thinning of the Hebrides Ice Stream, which, on the basis of supporting information, we infer to represent cessation of ice streaming at 20.6 ± 1.2 ka, 3–4 ka earlier than previously inferred. A period of more topographically restricted flow produced flow indicators superimposed on those relating to full ice stream conditions, and exposure ages from up-stream of these constrain deglaciation to 17.5 ± 1.0 ka. Complete deglaciation of the marine sector of the Hebrides Ice Stream occurred by 17–16 ka at which time the ice margin was located near the present coastline. Exposure ages from the southernmost Outer Hebrides (Mingulay and Barra) indicate deglaciation at 18.9 ± 1.0 and 17.1 ± 1.0 ka respectively, demonstrating that an independent ice cap persisted on the southern Outer Hebrides for 3–4 ka after initial ice stream deglaciation. This suggests that deglaciation of the Hebrides Ice Stream was focused along major submarine troughs. Collectively, our data constrain initial deglaciation and changes in flow regime of the Hebrides Ice Stream, final deglaciation of its marine sector, and deglaciation of the southern portion of the independent Outer Hebrides Ice Cap, providing chronological constraints on future numerical reconstructions of this key sector of the former British-Irish Ice Sheet.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Small, Dr David and Gheorghiu, Dr Delia and Xu, Dr Sheng and Fabel, Dr Derek
Authors: Small, D., Benetti, S., Dove, D., Ballantyne, C. K., Fabel, D., Clark, C. D., Gheorghiu, D. M., Newall, J., and Xu, S.
College/School:College of Science and Engineering > School of Geographical and Earth Sciences
College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:Quaternary Science Reviews
Publisher:Elsevier
ISSN:0277-3791
ISSN (Online):1873-457X
Published Online:06 May 2017
Copyright Holders:Copyright © 2017 The Authors
First Published:First published in Quaternary Science Reviews 167:30-46
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
583231BRITICE-CHRONODerek FabelNatural Environment Research Council (NERC)NE/J008729/1SCHOOL OF GEOGRAPHICAL & EARTH SCIENCES