Some Palaeomagnetic Measurements in Antarctica

Abstract

... The activity engendered by the International Geophysical Year 1957-8 provided an opportunity to obtain suitable rock specimens from the antarctic continent, and the author was able to visit two localities in Victoria Land. At Cape Hallett (72°S., 171°E.) the prominent Cenozoic volcanics were sampled, but the Palaeozoic sediments of the Robertson Bay group, quite highly metamorphosed in this region, were rejected as unlikely to provide reliable data on the ancient magnetic field. In the Ferrar Glacier region (78°S., 161°E.), samples were collected from the late Palaeozoic / early Mesozoic Beacon sandstone, and from the extensive Mesozoic dolerite sills intrusive within the sandstone series. The remanent magnetizations of the rocks collected were measured at King's College, University of Durham. A sensitive astatic magnetometer was employed to measure the weaker magnetization of the sedimentary rocks and a simpler instrument was used for the more strongly magnetized igneous specimens. Mean directions of magnetization and corresponding pole positions were calculated, and the 95 per cent level of confidence estimated in the usual way. ... Uncertainties in geological age and - for the Cape Hallett lavas - of the sampling procedure, preclude any precise statements. However, some general conclusions may be drawn. Here, as elsewhere, reversed directions of magnetization occur and may be interpreted as representative of reversals of the main magnetic field of the earth. Cenozoic rocks appear to have been magnetized in a mean field not essentially different from that of a geocentric dipole aligned with the present axis. Older rocks are magnetized in a direction significantly different from that of the present mean magnetic field. This may be interpreted as evidence of polar wandering, implying a polar movement of some 30 degrees since the later part of the Mesozoic era. The data are perhaps too sparse to admit of a discussion of continental drift.