ON POLAR-WANDER PATH FOR AUSTRALIA DURING CENOZOIC

Detailed palaeomagnetic measurements potassium‐argon and (K‐Ar) dating have been carried out on continuous lava sequences in the Nandewar, Liverpool and Barrington Volcanoes of New South Wales. Consistent K‐Ar ages in each case indicate that the volcanoes were built rapidly at 17.5±0.3 m.yr (Nandewar), 33.7±0.7m.yr (Liverpool) and 51.6±0.7 m.yr (Barrington), where the errors quoted are the standard deviations. Most of the 150 flows investigated show stable directions of magnetization after magnetic cleaning. Several field reversals are noted and in one instance a series of nine flows records the transition zone from reversed to normal polarity. The frequency and timing of the reversals are consistent with the Cenozoic geomagnetic time scale deduced from the interpretation of marine magnetic anomalies in terms of the sea‐floor spreading hypothesis around 17 and 34 m.yr, but not at 52 m.yr. It appears that the extrapolations made in its derivation may no longer be valid at that time. The three new precisely determined palaeomagnetic poles add detail to the Cenozoic polar‐wander path for Australia. A steady movement of the South Pole at about 0.45° per m.yr (∼ 5 cm yr−l) is indicated for the past 100 m.yr. This movement is not consistent with a simple northward movement of Australia as inferred from sea‐floor spreading data. It indicates in addition a westward excursion of the South Pole, which is attributed to a component of polar wandering superimposed upon the continental drift. Copyright © 1969, Wiley Blackwell. All rights reserved