Geophysical fieldwork on the Ronne Ice Shelf, Antarctica

The idea of a single landmass, Gondwanaland, uniting all the southern continents in the Palaeozoic was first established by Wegener (1915). Du Toit (1937) presented a reconstruction of the supercontinent which recognised the central position of Antarctica relative to the other fragments. Common to this and all subsequent attempts at reconstruction is the need to justify or remove an apparent overlap of the Antarctic Peninsula and southern South America (Barker & Griffiths 1977). Removal of this overlap is commonly produced by allowing substantial continental movement and extension within an area subsequently masked by the ice sheet of West Antarctica. Here the geology is complex for the isolated outcrops include fragments of pre-Cambrian crystalline basement, folded sequences of Palaeozoic sediments and lithologies representing Mesozoic-Cenozoic subduction-related activity. Deep subglacial trenches separating the outcrops are believed to indicate a micro-continental nature for West Antarctica, in contrast to the stable craton of East Antarctica.