On the magnetic memory phenomenon in rocks and its bearing on palaeomagnetic measurements

Summary The results of recent extensive studies on the low field hysteresis in basalts from India and East Africa and the memory phenomenon observed in some of the rocks have been found to have a direct bearing on the various parameters such asQ _n,Q _tn, stability by the A.C. field technique etc. which are of great importance in rock-magnetism. It has been found that rocks having low Curie temperature (it _c ) and not exhibiting memory phenomenon are ideally suited for palaeomagnetic studies. Also, rocks having relatively higher it _c often exhibit memory phenomenon, given inconsistent NRM directions and show an irregular behaviour on A.C. field cleaning. In using the latter rock types for palaeomagnetic work one has to take a number of precautions which are clearly brought out by the studies described in this paper.