Magnetic Stratigraphy



Magnetic stratigraphy consists of grouping sedimentary or igneous rock strata into intervals that have a common magnetic property. The best-known method—magnetostratigraphy—uses magnetization directions to define “magnetozones” of constant polarity in a rock outcrop. Magnetostratigraphy has helped to confirm and date the record of polarity derived from oceanic magnetic anomalies in the past 180 Ma, and has thus contributed to developing and accepting the plate tectonics paradigm.

Other types of magnetic stratigraphy make use of nondirectional magnetic parameters (for example, the intensities of different remanent magnetizations or magnetic susceptibility), which are affected by sedimentary processes such as erosion and depositional rates. Stratigraphic fluctuations in these parameters may reflect paleoclimatic influences; therefore, they have received more attention in recent years as a result of the increasing interest in environmental magnetism. When sedimentation effects can be taken into account, the stratigraphic variation of magnetization intensity may relate to fluctuations of geomagnetic paleointensity.