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Entrainment of Glaciomarine Sediments and Formation of Thrust-Block Moraines at the Margin of Sorsdale Glacier, East Antarctica

Sean J. Fitzsimons

Department of Geography, University of Otago, PO Box 56, Dunedin, New Zealand

 
Abstract

The morphology, sedimentology and structure of moraines at the margin of an outlet glacier in east Antarctica are described, and contemporary depositional processes in a marine inlet adjacent to the ice margin are examined. Results indicate that the principal moraines are thrust-block moraines produced by basal freezing and deformation of glaciomarine sediment as the outlet glacier expands into a marine inlet. Preservation of detailed glaciomarine sedimentary structures and beds of marine shells suggests that the sediment was frozen during entrainment, transportation and deposition. The presence of low-angle faults in the moraines show that the moraines consist of an en echelon arrangement of thrust plates. The sedimentology, structure, thickness of the thrust plates, and inferred entrainment processes are consistent with Weertman's ice-debris accretion hypothesis for debris entrainment at the edge of cold ice sheets. A model of thrust-block moraine development produced by this study provides a framework for the interpretation of radiocarbon dates from marine macrofossils in the moraines. The model may also be useful in the interpretation of similar moraines in coastal east Antarctic oases and other polar marginal marine environments.

Keywords: entrainment; glaciotectonics; basal freezing; thrust-block moraines

 

Reference

Fitzsimons, S.J. 1997. Entrainment of glaciomarine sediments and formation of thrust-block moraines at the marine of Sørsdale Glacier, East Antarctica. Earth Surface Proccesses and Landforms 22 (2), 175-187. [PDF 500kb] doi:10.1002/(SICI)1096-9837 (199702)22:2<175::AID-ESP694>3.0.CO;2-G

 

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