Magnetic Cleaning of Rocks in Palaeomagnetic Research

Abstract

Summary It has been observed that the remanent magnetism of rocks is often the resultant of two magnetizations: firstly a magnetization with low coercive force, mostly directed by the local present Earth's field; and secondly a magnetization with high coercive force which shows the direction of the field from the period of the rock formation. It is shown that it is possible to remove the disturbing magnetization of low coercive force while saving a good deal of the fossil magnetization with the aid of partial demagnetization. This was carried out by a combination of alternating fields and heating. Generally a demagnetization with alternating fields up to 300 oersted (effective) at a temperature of 150 °C appeared to be sufficient to clean the rocks.