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Sedimentological signatures of the sub-Amery Ice Shelf circulation

Published online by Cambridge University Press:  01 October 2007

M.A. Hemer ,
A.L. Post ,
P.E. O'Brien ,
M. Craven ,
E.M. Truswell ,
D. Roberts  and
P.T. Harris
M.A. Hemer*
Affiliation:
Marine and Coastal Environment Group, Geoscience Australia, GPO Box 378, Canberra, ACT 2601, Australia
A.L. Post
Affiliation:
Marine and Coastal Environment Group, Geoscience Australia, GPO Box 378, Canberra, ACT 2601, Australia
P.E. O'Brien
Affiliation:
Marine and Coastal Environment Group, Geoscience Australia, GPO Box 378, Canberra, ACT 2601, Australia
M. Craven
Affiliation:
Australian Antarctic Division and Antarctic Climate and Ecosystems Co-operative Research Centre, Private Bag 80, Hobart, TAS 7001, Australia
E.M. Truswell
Affiliation:
Department of Earth and Marine Science, Building 47, Australian National University, Canberra, ACT 2600, Australia
D. Roberts
Affiliation:
Institute of Antarctic and Southern Ocean Studies, University of Tasmania, Private Bag 77, Hobart, TAS 7001, Australia
P.T. Harris
Affiliation:
Marine and Coastal Environment Group, Geoscience Australia, GPO Box 378, Canberra, ACT 2601, Australia
*
*Corresponding author: now at CSIRO Marine and Atmospheric Research, GPO Box 1538, Hobart, TAS 7001, Australia mark.hemer@csiro.au
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Abstract

Two sediment cores collected from beneath the Amery Ice Shelf, East Antarctica describe the physical sedimentation patterns beneath an existing major embayed ice shelf. Core AM01b was collected from a site of basal freezing, contrasting with core AM02, collected from a site of basal melting. Both cores comprise Holocene siliceous muddy ooze (SMO), however, AM01b also recovered interbedded siliciclastic mud, sand and gravel with inclined bedding in its lower 27 cm. This interval indicates an episode of variable but strong current activity before SMO sedimentation became dominant. 14C ages corrected for old surface ages are consistent with previous dating of marine sediments in Prydz Bay. However, the basal age of AM01b of 28250 ± 230 14C yr bp probably results from greater contamination by recycled organic matter. Lithology, 14C surface ages, absolute diatom abundance, and the diatom assemblage are used as indicators of sediment transport pathways beneath the ice shelf. The transport pathways suggested from these indicators do not correspond to previous models of the basal melt/freeze pattern. This indicates that the overturning baroclinic circulation beneath the Amery Ice Shelf (near-bed inflow–surface outflow) is a more important influence on basal melt/freeze and sediment distributions than the barotropic circulation that produces inflow in the east and outflow in the west of the ice front. Localized topographic (ice draft and bed elevation) variations are likely to play a dominant role in the resulting sub-ice shelf melt and sediment distribution.

Keywords

Antarcticabaroclinic circulationsedimentsub-ice shelf circulation

Information

Type
EARTH SCIENCES
Information
Antarctic Science , Volume 19 , Issue 4 , December 2007 , pp. 497 - 506
Copyright
Copyright © Antarctic Science Ltd 2007

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