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Alfred Wegener Institute for Polar and Marine Research, Postfach 120161 D-27515 Bremerhaven, Germany
1 Fachbereich Geowissenschaften, Universität Bremen, Postfach 330 440, D-28334 Bremen, Germany
The investigation of the crustal structure in the southern Weddell Sea was one of the scientific targets of two refraction seismic experiments carried out by the Alfred Wegener Institute in 1984 and 1992. Two profiles were shot in front of the Ronne Ice Shelf between 50°W and the Antarctic Peninsula. The data reveal different crustal structures east and west of 60°W. In the east, sediments up to 13 km thick overlie basement about 20 km thick, which is of continental origin. The lower crust is characterized by velocities between 7.1 and 7.5 km s–1 which may indicate magmatic underplating and/or intrusions. From these data, it is estimated that the crust is stretched by a factor between 1.5 and 3.0. In the west, the sedimentary basin pinches out, whereas the upper crustal layers exhibit higher velocities (>5 km s–1) than in the east (<4 km s–1).
The existence of continental crust in the southern Weddell Sea excludes geodynamic models which propose a palaeoposition of the Ellsworth-Whitmore Mountains between South Africa and Coats Land, East Antarctica. Based on recently published potential field data, a new model for the location of the continent-ocean boundary is proposed.
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