Palaeomagnetism of the Msissi norite (Morocco) and the Palaeozoic reconstruction of Gondwanaland |
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| Authors: | EA Hailwood |
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| Institution: | Department of Oceanography, University of Southampton, Southampton Great Britain |
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| Abstract: | Palaeomagnetic results are reported from eight sites in an Upper Devonian basic intrusion (the Msissi norite) in southeast Morocco. Specimens from one site are suspected of having been affected by lightning, but results from the other seven sites indicate the presence of a less-stable component, probably of viscous origin. The pole position corresponding to the stable component(0.5°S, 25°E, A95 = 16.5) is interposed between the Middle Cambrian/Ordovician pole and the Lower Carboniferous pole on the African polar wander curve. When the southern continents are reassembled on the Smith/Hallam reconstruction of Gondwanaland the new Moroccan Devoniån pole is in excellent agreement with the corresponding portion of the main Australian polar-wander curve. This places additional constraints on the possible date of fusion of the separate Southeast Australian plate with the rest of Gondwanaland, postulated recently on palaeomagnetic grounds by M.W. McElhinny and B.J.J. Embleton (1974). The combined African/Australian polar-wander curve is compared with the South American curve, and two possible interpretations of available data are discussed, one involving possible relative tectonic motion between South America and the rest of Gondwanaland during the Lower and Middle Palaeozoic, and the other, favoured here, requiring a reassessment of the ages of several South American pole determinations. |
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