Folding in the Johnsons Glacier, Livingston Island, Antarctica

Author:

Ximenis L.1,Calvet J.1,Garcia D.1,Casas J. M.1,Sàbat F.1

Affiliation:

1. Departament de Geodinàmica i Geofísica, Universitat de Barcelona Martí i Franquès s/n, Barcelona 08028, Spain lximenis@geo.ub.es

Abstract

AbstractAn active fold system revealed by interbedded tephra layers is visible on the ablation surface of Johnsons Glacier (Livingston Island, South Shetland Islands, Antarctica). Johnsons Glacier is a cirque-shaped glacier of 5 km2 area located in a temperate ice cap. Converging flow-lines as a consequence of the reducing channel section extend from ice divides and terminate in a calving ice-cliff. Recent tephra layers from the volcano on Deception Island constitute excellent markers of the internal structure of the glacier and, when dated, provide valuable information about deformation kinematics.Detailed field mapping of the clearly visible tephra markers revealed several folded layers that define a set of folds with sub-horizontal and fan-distributed axes being sub-parallel to the converging flow-lines. Folds become tighter towards the centre of the channel, where a cylindrical anticline is clearly exposed. Related deformational structures, comprising minor folds, foliations, thrust faults and crevasses, are observed in the ablation area. Strain-rates reflect extensional flow and higher deformation values where maximum confluence occurs.We examine how the occurrence of this structure results from the transverse shortening in response to the reducing channel section and the consequent confluence of ice masses, increase in differential flow-rates between the centre of the glacier and the margins, and the development of passive folding processes.

Publisher

Geological Society of London

Subject

Geology,Ocean Engineering,Water Science and Technology

Reference26 articles.

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2. 1970 volcanic eruption at Deception Island;Baker;Nature,1971

3. Benjumea B. Teixidó T. Casas J. M. Ximenis L. Feriche M. (1998) IV Meeting of the Environmental and Engineering Geophysical Society in Proceedings, 2D seismic survey on Johnsons Glacier, Livingston Island (Antarctica), ed Casas A. (Instituto Geográfico Nacional, Madrid), pp 591–594.

4. Disminución del casquete glaciar de la isla Livingston;Calvet;Geogaceta,1998

5. Calvet J. Pallàs R. Sàbat F. Vilaplana J. M. (1993) in V Simposion Español de Estudios Antárticos, Los niveles de cenizas de los glaciares de Livingston, Criterios para su datación, ed Serrat D. (Comisión Interministerial de Ciencia y Tecnología, Madrid, Acta), pp 195–208.

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