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Geophysical Monograph Series




Crustal structure in Antarctica

G. P. Woollard

Methods of crustal study that have been applied, or are contemplated, for the study of the crust beneath Antarctica are reviewed in order to assess the relative reliability of results obtained using different methods. The results of shallow (3–5 km) refraction measurements are used to show there is no significant difference in the velocity structure of the upper crust beneath Eastern and Western Antarctica, and that both are typically ‘continental.’ The results of earthquake surface-wave dispersion studies of crustal thickness in Antarctica are reviewed and the strong dependence of this method of analysis on choice of a standard model demonstrated. On the basis of a realistic standard model, compatible with modern seismic refraction measurements, it appears the crust beneath Western Antarctica is about 30 km thick and that beneath Eastern Antarctica about 40 km thick. The strong dependence of crustal solutions, using gravity and elevation data, in Antarctica on knowing the thickness of ice present is demonstrated by results for the Soviet traverse to the Pole of Inaccessibility and the British Trans-Antarctic traverse. These same results are also used to demonstrate the general reliability to be expected in using free air gravity anomalies for determining the elevation and configuration of the sub-glacial rock surface. First approximations of crustal thickness are derived along a number of traverse routes in both Eastern and Western Antarctica and it is shown that whereas the crust beneath Western Antarctica is about 32 km thick with thinning to 28 km beneath the Filchner Ice Shelf, the Ross Sea embayment and its extension beneath Marie Byrd Land, that beneath Western Antarctica is either 42 km or 49 km, depending upon the existence of the major sub-glacial mountain range reported near the Pole of Inaccessibility. That Antarctica, beneath its superimposed load of ice, is in isostatic equilibrium is indicated by the regional approximation of zero free air gravity anomaly, and it is shown that the equivalent thickness of rock for the column of ice present is equal to the degree of crustal warping and equal to the amount of isostatic rebound to be expected if the ice were to melt.

Citation: Woollard, G. P. (1962), Crustal structure in Antarctica, in Antarctic Research: The Matthew Fontaine Maury Memorial Symposium, Geophys. Monogr. Ser., vol. 7, edited by H. Wexler, M. J. Rubin, and J. E. Caskey Jr., pp. 53–73, AGU, Washington, D. C., doi:10.1029/GM007p0053.

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