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Ice crystal properties of amber ice and strain enhancement at the base of cold Antarctic glaciers

Denis Samyn1, Anders Svensson2, Sean J. Fitzsimons3, Reginald D. Lorrain1

1 Départment des Sciences de la Terre et de l'Environnement, Faulté des Sciences, CP 160/03, Université Libre de Bruxelles, B-1050 Brussels, Belgium
2 The Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen, Denmark
3 Department of Geography, University of Otago, PO Box 56, Dunedin, New Zealand

 
Abstract

To improve our understanding of the deformation properties of cold-based polar glaciers, we examine here some of the factors leading to the localization of strain within the amber ice facies. We present a crystallographic case study of amber ice (a fine-grained bubbly ice containing a relatively high impurity content) sampled at the base of two Antarctic glaciers. The crystal fabrics and textures of amber ice were computed by application of a recently developed automated method. To date, it was tedious and awkward to determine amber ice facies accurately because of the sub-millimetric crystal size and relatively high debris content of this facies. The authomatic analytical method applied in this study allows not only for improving analytical accuracy in this task but also for considerably reducing the time of analysis. Our investigations reveal highly homogeneous crystallographic properties fro teh studied amber ice. The ice crystals are mainly polygonal, equant and sub-millimetric, and show a strong lattice-prefered orientation. These properties, besides the relatively high impurity content, are likely to exert a major control on strain enhancement in amber ice when this facies is present at the base of cold glaciers.

 
Reference 

Samyn, D., Svensson, A., Fitzsimons, S. J. and Lorrain, R. D. 2005. Ice crystal properties of amber ice and strain enhancement at the base of cold Antartic glaciers. Annals of Glaciology, 40, 185-190. [PDF 246kb].

 

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