The Geomagnetic Field in Permo‐Triassic Time

Abstract

A least‐squares fit of the 500‐fathom or 1000‐metre contour of the principal continental masses has been constructed which may approximate to the arrangement of the continents in Permo‐Triassic time. Reliable Permo‐Triassic palaeomagnetic data have been plotted on this reassembly, mean pole positions for the larger fragments have been calculated, and grand mean poles for Permian and Triassic time have been estimated. To a first approximation results are consistent with a geocentric dipole field, but small systematic departures have been detected. These may be attributed to superimposed multipole components coaxial with a dipole field, although other explanations, such as anomalies originating in the crust cannot be completely excluded. Tests for the existence of multipole components are suggested. The effect of such components on the accuracy of continental reassemblies based on palaeomagnetism is briefly noted. Copyright © 1971, Wiley Blackwell. All rights reserved