First Break - Volume 4, Issue 1, 1986

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.

During the period 1983-84 a geophysical synthesis of several coastal basins in Morocco was carried out. The interpreted area included the Doukkala, Essaouira and Souss Basins. These are Mesozoic basins underlain by Palaeozoic unmetamorphosed rocks. The interpretation was based primarily on gravity data, together with additional information from seismic, aeromagnetic, outcrop and well data. An essential goal of this interpretation was the determination of the structure of the deep Palaeozic unconformity, which is hardly recognisable on the seismic sections.