Rock magnetism—Geophysical aspects

Abstract

This review will not be concerned with rock magnetism as a geophysical tool to assist the geologist in unravelling structures and in the correlation of strata. No doubt the remarkable development since the war of the airborne magnetometer or fluxgate and the use in consequence now made of magnetic surveys will soon need to draw upon the increasing knowledge of the fundamental magnetic properties of rocks. Also the permanent magnetization of rocks varying in direction and intensity between strata will be an important assistance in the work of the geologist. However this review is solely concerned with the application of rock magnetism to the extension of our knowledge of the physical properties of the earth throughout geological time. An important stage in the development of our understanding of rock magnetism was the publication by Koenigsberger (1938) of an extensive review of work done up to that date in the field. Recently Nagata (1953) has reviewed very fully many aspects of the subject, particularly the method by which igneous rocks become magnetized and the physical properties of the iron oxide minerals responsible for the magnetization. This review will therefore be restricted mainly to the discussion of developments since Nagata's important book.