Demonstrating That Continents Had Drifted: Paleomagnetic Measurements at the Australian National University 1952 - 1964

Abstract

Over fifty years ago, the new Department of Geophysics of the Australian National University in Canberra pursued research in paleomagnetism which was to be fundamental to the major developments in Earth Sciences now known as the plate tectonics revolution. In the setting of some then unexplained phenomena such as reversely magnetized rocks, and slightly in advance of fundamental developments in the dating of rocks using radioactive decay schemes of naturally-occurring isotopes, a team led by Edward Irving obtained data for the Australian continent which, accepted and combined with data from Europe and North America, demanded that major continents of the globe had moved relative to each other over geological time. Generally these facts are recognised in histories of science, however such histories usually do not record the local Australian National University setting, which it is intended to describe in this paper. Essential for the paleomagnetic work was the skilled support of a wide range of Australian geologists, who guided collection strategy and supplied oriented samples that had been collected continent-wide. It may also be little appreciated that the first paleomagnetic measurements at the Australian National University were carried out by J. C. Jaeger on samples of Tasmanian dolerite, following work on the same rock by P. M. S. Blackett's group in England. Because these cores were vertical and the magnetization in them approximately vertical, that they were not oriented with regard to horizontal direction was unimportant. Their vertical magnetization gave a forerunner of the continental-drift result.