Further Palaeomagnetic Results from South Victoria Land, Antarctica

Summary A palaeomagnetic study has been made of rock samples taken from a 5000 ft sequence in South Victoria Land. The sequence consists of granites, sediments and hypabyssal intrusives of Mesozoic, Palaeozoic and possibly Pre-Cambrian ages. The directions of natural remanent magnetization are approximately uniform throughout, but small and apparently real differences do occur between some of the units within the sequence. Laboratory tests using alternating magnetic fields suggest that these differences are due to the presence of unstable components of small but variable magnitude and that the mean directions of the stable components are parallel in all the units studied. This uniformity in direction could have resulted from the geomagnetic field in the region being constant in direction for a long period of time in the Palaeozoic and Mesozoic, or from the reheating of the whole area during the last phase of intrusion (that of the Ferrar dolerites) in Mesozoic times. The latter interpretation is favoured. The variations in magnetic properties through the Ferrar dolerite sheets are described and provide information relevant to theories of their emplacement and differentiation.

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