Palaeomagnetic measurements on rocks from Mt Crean to determine the continental drift of gondwanaland

The Beacon sediments of East Antarctica were deposited over the Devonian to Triassic geological periods, from 400 to 200 million years ago. Palaeomagnetic measurements on these rocks provide information on the continental drift of Gondwanaland and the geological history can be inferred. Past dating of Antarctic rocks finds a single pole, for a time 160 million years ago in the Jurassic period corresponding to a massive intrusion of dolerite sills into the Beacon sediments. Heat and fluid from these intrusions largely destroyed the primary magnetisation acquired by rocks older than them. Rock samples from the Victoria University of Wellington Antarctic rock collections were remeasured using newly developed techniques. Some rock samples were found to retain some primary magnetisation. Further samples were collected from promising sites to corroborate the measurements. 200 orientated cores, 25 mm in diameter and 50 to 150 mm long were obtained from Mt Crean on the edge of the polar plateau, 200km west of Scott Base, Mt Feather and Table Mountain. The sediments sampled were red siltstones from the Aztec Group, or Upper Devonian age. A reassessment of the structure of Gondwanaland and its climate at the time was reported due to these new results.