oa Gravity and Magnetic Surveys of the South African Offshore

A substantial number of magnetic and gravity surveys have been carried Out over the last<br>forty years around the South African coast, the main participants being SOEKOR, the<br>Council for Geoscience, and De Beers Marine.<br>Since 1994, an increased interest by international companies in petroleum ventures in the<br>country’s territorial waters has resulted in the necessity of re-evaluating the existing gravity<br>and magnetic data.<br>Maps on the poster show the areas covered by the various gravity and magnetic surveys. The<br>vintage, mode of acquisition, number of lines, line spacing, total distance of lines traversed,<br>and status of each survey in terms of the extent to which the data have been processed and<br>interpreted is tabulated. Image compilations of areas around the South African coast are<br>shown, generated by juxtaposing SOEKOR ‘s gravity and magnetic data against other data<br>sets.<br>Individual case histories show the use of gravity and magnetics with respect to aiding seismic<br>interpretations in:<br>• Determining gross structure and depth to basement of sedimentary basins.<br>• Identifying sills and/or volcanics within sedimentary sequences.<br>• Distinguishing between carbonate reefs and dolerite dykes.