Weddell Sea tectonics and Gondwana break-up: an introduction

The Weddell Sea, part of the circumpolar Southern Ocean, is probably the most remote, least known and least accessible sea in the world. Difficult ice conditions have limited the acquisition of ship data, although this has been partly offset in recent years by access to satellite radar altimetry data. The Weddell Sea was originally defined by the Admiralty Hydrographic Department in 1932 and redefined by the Antarctic Place Names Committee in 1976 (Hattersley-Smith 1991). It is bounded on the western side by the east coast of the Antarctic Peninsula, on the southern side by the Ronne and Filchner ice fronts, and on the southeastern side by the Dronning Maud Land and Coats Land coasts of East Antarctica (Fig. 1). The South Scotia Ridge separates the Weddell Sea from the Scotia Sea to the north and a line joining Southern Thule in the South Sandwich Islands and Kapp Norvegia in Dronning Maud Land, separates it from the South Atlantic Ocean to the NE. Within this volume, papers relate to the Weddell Sea as defined above, together with part of the adjoining South Atlantic Ocean up to 50°E, and to the geology of the once neighbouring continents of Gondwana. The term Weddell Sea embayment is also used informally throughout this volume to include the embayment area to the south of the Weddell Sea now covered by the Ronne and Filchner ice shelves, including Berkner Island, and the continental shelf north of the Ronne and Filchner ice fronts (Figs 1 & 2).