The Palaeomagnetism of the Antrim Plateau Volcanics of Northern Australia

The magnetization of samples from 29 sites in Lower Cambrian Volcanics and interbedded sediments, collected over an area of 250 000 km2 of northern Australia, has been investigated. Fourteen of the sites respond to magnetic cleaning, although in one case thermal cleaning is preferred. The other sites either become randomly magnetized or remain magnetized in the direction of the present geomagnetic field, as in the case of the interbedded sediments The mean direction of D = 51°, I = +66° (α95 = 13°) gives a palaeomagnetic pole at 9 N, 160 E with A95 = 17° The polar-wander path for Australia is for the first time extended back to Lower Cambrian times with confidence, and a complete curve can now be drawn for the Phanerozoic. It is concluded that Australia was situated in the Northern Hemisphere in Cambrian times. Two rapid polar transitions are identified during the Palaeozoic, a feature which is also present in data from Africa. The polar-wander paths for these two continents can now be made to coincide for the whole of the Palaeozoic, implying that their relative positions remained unchanged during this period.