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Depositional models for moraine formation in East Antarctic coastal oases

Sean Fitzsimons

Department of Geography, University of Otago, Dunedin, New Zealand

 
Abstract

This paper examines the origin of moraine ridges in East Antarctic coastal oases and derives depositional models appropriate for the reconstruction of Quaternary history. On the basis of morphology, structure and sedimentology, four principal types of ridge may be identified: (1) type A moraines form when the basal debris zone crops out near an ice margin; (2) type B moraines form when large recumbent folds develop in the basal debris zone; (3) type C moraines are ice-contact screes and fans which form when debris accumulates at steep or cliffed ice margin; and (4) type D moraines are trust-block moraines that form when unconsolidated sediment is entrained by freezing , shearing and thrusting of sediment blocks at the base of the glacier. Simple calculations of the rate of debris accumulation at ice margins suggest that type A, B, and C moraines take thousands of ears to form and record stable ice margins. The D moraines are structural features that may form relatively quickly when ice margins override unconsolidated sediment. Constructing models to explain the origin of the moraines is an important part of reconstructing the Quaternary history of Antarctic coastal oases, because the models provide a basis for reconstructing the position and behaviour of the ice sheet during advance and retreat.

 
Reference

Fitzsimons, S.J. 1997. Depositional models for moraine formation in East Antarctic coastal oases. Journal of Glaciology 43 (144), 256-264. [PDF 496kb]

 

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