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Equifinality of basal ice facies from an Antarctic cold-based glacier

Suzanne Sleewaegen1, Denis Samyn1, Sean J. Fitzsimons2, Reginald D. Lorrain1

1 Département des Sciences de la Terre et de l'Environnement, Université Libre de Bruxelles, Brussels, Belgium
2 Department of Geography, University of Otago, Dunedin, New Zealand

 

Abstract

Three debris-bearing ice facies were recognized at the base of Suess Glacier, a cold-based glacier damming a lake in Taylor Valley, South Victoria Land, Antarctica. These facies are termed "amber ice", "solid facies" and "basal stratified facies". This paper uses stable-isotope composition (D and 18O), gas content and gas composition (CO2, O2 and N2) to develop an understanding of the processes responsible for the formation of these facies. The basal ice is characterized by a striking difference in ice properties between the innermost end of a 25 m long tunnel dug 200 m upstream from the glacier front and the front itself. At the glacier front, co-isotopic data plot along a well-defined freezing slope (S = 5.6), whereas, inside the tunnel, the isotopic data offset from the freezing slope and from the local meteoric water-line (which has a slope of 8.2). CO2 concentrations rise from a minimum of about 1000 ppmv in the tunnel to about 220 000 ppmv at the front. Taken together, these characteristics strongly suggest an increasing contribution of liquid water in the formation of basal ice towards the glacier terminus. We therefore conclude that visually similar basal ice facies can have different origins.

 

Reference

Sleewaegen, S., Samyn, D., Fitzsimons, S.J. and Lorrain, R.D. 2003. Equifinality of basal ice facies from an Antarctic cold-based glacier. Annals of Glaciology 37, 257-262. [PDF 1079 kb]

 

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