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Report on the Eleventh Victoria University of Wellington Antarctic Expedition 1966-67: VUWAE 11
Elevated Beach Ridges
Elevated Beach Ridges.
- A[unclear: R]2(0.2), B:2.2. (0.2), C 3.1 (0.2), D 3.9 (0.2), E 6.0 (1.4), F 7.2 (0.6), G 9.2 (0.5), H 10.4 (0.2), I 11.3 (?), J 13.1 (0.2), K 115.0 (0.9), L 18.1 (1.0)
In Northern Norway a similar but more numerous series of ridges that have been attributed to isostatic uplift are reasonably well dated by four radio-carbon samples. Isostatic uplift is generally assumed to be a continuous and not an intermittent process, and isostatic continuity in Finland is substantiated by tilt observed on lakes during the past 40 years. Uplift but not the formation of specific beach ridges can be attributed to the isostatic movement, and their formation must be due to some intermittent factor, either directly climatic or to some small sea-level oscillations. The radio carbon samples indicate that the time interval between the formation of the Norwegian ridges is remarkably uniform with a value of almost
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exactly 400 years. Because of the uniform interval, and because, the rate of isostatic uplift has been decreasing while sea level has remained substantially stationary the vertical interval between successive Norwegian beach ridges has progressively decreased with tine for the last 6,000 years.
In South Victoria Land there is no general agreement on the age of shore line features of the kind we measured near Marble Point. However, it is possible that the 400 year cycle may well operate, and this is made likely by progressive decrease in the vertical interval between successive beach ridges indicated by the values given above. The progressive decrease in vertical interval indicates that the ridges are a single series and not, for example, in part 100,000 or more years old and in part less than 6,000 years old. The distance over which the ridges were observed is too small to determine the small tilt that is likely to have taken place, and because the difficulties in correlation it is unlikely that the direction and tilting can be established anywhere in South Victoria Land. One clear relation was observed: the older and higher ridges progressively cut out towards the south. The cut-out is attributed to the southerly retreat of the Ross Ice Shelf while the beach ridges were being cut.