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Victoria University Antarctic Research Expedition Science and Logistics Reports 1996-97: VUWAE 41

1. Popular Summary of Scientific Work Achieved

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1. Popular Summary of Scientific Work Achieved

The aim of this event was to look at raised beaches along the Scott Coast from Cape Bernacchi to Dunlop Island. These features have developed since the last glacial maximum approximately 18,000 years ago when the ice sheets were at their greatest extent. The weight of the overlying ice depressed the land which has slowly rebounded after the ice melted. While rebounding a series of beach ridges were formed.

One part of the project is to date the beach ridges and associated rock platforms by three different methods and obtaining relative heights above sea level today. This will allow modelling of the volume and extent of the ice during the last glacial maximum. There has been approximately 120 m of sea level rise since the last glacial maximum, with the well constrained northern hemisphere ice sheets contributing about 90 m. The Antarctic contribution is less well constrained, so by this study combined with other similar studies from East Antarctica a better idea of the amount of ice in Antarctica during the last glaciation should be obtained.

To obtain a height above sea level today it is necessary to know where sea level was on the raised beach ridges. The second part of the project looks at the modern beach formation. Very little work has been done on Antarctic beaches and the processes which form them. Studying the modern beaches along the Scott Coast will add enormously to this knowledge. By linking processes found on the modern beaches to features in the raised beaches should give an accurate position of sea level on the raised beaches.

The third part of the event aims to identify the provenance of glacial moraines along the Scott Coast and to provide a chronology for retreat of ice from this area using surface exposure dating techniques.

The work was carried out from a series of four camps along the Scott Coast, one at Marble Point which covered the area from South Stream to Gneiss Point, one at Kolich Point, one at Spike Cape which covered both tombolos and the mainland and finally one at Dunlop Island.

There are well developed boulder beaches along most of the coast which are dominantly storm deposits with very little ice influence. A good correlation was able to be established between the size of ridges and materials to the energy of formation. Links were established between active processes and sediments found in the raised beaches, such as the evidence of a shallow tidal channel features on Marble Point. Well developed raised rock platforms between the beaches should provide the key dating tool (surface exposure dating). These will allow a better record of relative sea level fall in the area than has previously been available. Links have been established between the various dating techniques. Surveying of marine limits and beach profiles page break should be more accurate than in previous surveys due to better controls. Preliminary observations of volcanic erratics indicate the Ross Sea ice extended to an approximate altitude of 350 m on Hjorth Hill and covered Marble Point and Spike Cape. Moraine deposits imply a more recent advance of the Wilson Piedmont Glacier which may overrun earlier Ross Sea moraine.