The Palaeomagnetism of the Stormberg Lavas, II. The Behaviour of the Magnetic Field During a Reversal

Abstract

The main theme of this paper is to investigate the intensity of the ancient geomagnetic field during the transition from a reversed to a normal direction as the Stormberg lavas were being extruded in Triassic-Jurassic times. The nature of the natural remanent magnetization of these rocks is investigated. It is thought that the effects of secondary magnetization, notably a high isothermal remanent magnetization believed to be due to lightning discharges and a remanent component resembling viscous magnetization, have been eliminated. The direction and intensity of magnetization of the normal and reversed zones are described and compared. It seems probable that the field strength decreased by a factor of four to five during the transition.