Antarctic Science

Papers—Earth Sciences and Glaciology

Ice shelf grounding zone features of western Prydz Bay, Antarctica: sedimentary processes from seismic and sidescan images

P.E. O'Brien a1, L. De Santis a2, P.T.  Harris a3, E. Domack a4 and P.G. Quilty a5
a1 Antarctic CRC and Australian Geological Survey Organisation, GPO Box 378, Canberra, ACT 2601, Australia
a2 Osservatorio Geofisico Sperimentale, 34016 Trieste, Italy
a3 Antarctic CRC and Australian Geological Survey Organisation, University of Tasmania, GPO Box 252-80, Hobart, TAS 7001, Australia
a4 Hamilton College, Hamilton, NY 13323, USA
a5 Australian Antarctic Division, Channel Highway, Kingston, TAS 7050, Australia

Article author query
o'brien p   [PubMed][Google Scholar] 
santis l   [PubMed][Google Scholar] 
harris p   [PubMed][Google Scholar] 
domack e   [PubMed][Google Scholar] 
quilty p   [PubMed][Google Scholar] 


Several grounding zone wedges were left on the floor and flanks of Prydz Channel in western Prydz Bay by the Lambert Glacier during the last glacial cycle. Seismic profiles indicate that vertical accretion at the glacier bed was the most important depositional process in forming the wedges, rather than progradation by sediment gravity flows. Sidescan sonographs reveal extensive development of flutes on the sea floor inshore from the wedges, indicating deformable bed conditions beneath the ice. The region inshore of the east Prydz Channel wedge features extensive dune fields formed by currents flowing towards the grounding zone. This orientation is consistent with models of circulation beneath ice shelves in which melting at the grounding line generates plumes of fresher water that rise along the base of the ice shelf, entraining sea water into a circulation cell. The Lambert Deep is surrounded by a large composite ridge of glacial sediments. Internal reflectors suggest formation mostly by subglacial accretion. The sea floor in the Lambert Deep lacks dune fields and shows evidence of interspersed subglacial cavities and grounded ice beneath the glacier. The absence of bedforms reflects sea floor topography that would have inhibited the formation of energetic melt water-driven circulation.

(Received December 30 1997)
(Accepted May 15 1998)

Key Words: Amery Ice Shelf; grounding zone; Prydz Bay; sedimentology; seismic; sidescan.