MAGNETISM IN ROCKS

Rock magnetism is the study of induced and remanent magnetization of f errimagnetic mineral grains in rocks, sediments, soils, and organisms. Its applications include environmental magnetism, magnetic anisotropy , sources of continental and oceanic magnetic anomalies, records of ge omagnetic field variations and polarity reversals, and the paleomagnet ic record of plate motions and the Wilson cycle. This paper reviews th e beginnings of rock magnetism and then traces the development of six particularly interesting areas: pseudo-single-domain behavior; magneti c domains and micromagnetic structures; diagnostic tests of the type a nd stability of remanent magnetization; magnetic microanalysis; thermo viscous remagnetization; and chemical remanent magnetization. Other ar eas, including sediment and soil magnetism, are covered in a companion paper by Verosub and Roberts on environmental magnetism.