Palaeomagnetism of Some Devonian Rock Formations in Australia

Abstract

From southern New South Wales a palaeomagnetic survey of rocks whose ages are Upper Silurian-Lower Devonian, Middle Devonian and Upper Devonian has been made. The rock types include the Canberra Volcanics and Porphyries, the Murrumbidgee Sandstones and the Nethercote Basalts. Throughout these formations and irrespective of the rock type the directions of magnetization are remarkably uniform. The low inclination of the direction of remanent magnetization indicate that throughout this period Australia lay 10–15° away from the equator, the pole lying in the South Atlantic. Evidence for stability of the rocks is as follows: (1) their uniformity of direction, (2) the deviation from the present geomagnetic and dipole fields, (3) the presence of normal and reversely magnetized rocks. These data lend support to the belief that south-eastern Australia experienced tropical conditions during the Devonian.