Paleomagnetism, principles

Abstract

Apart from isolated but important pioneering studies, in which the characteristics of the geomagnetic field and the rudiments of rock magnetism were explored, paleomagnetism originated as a scientific discipline in the 1950s. As a result of the continuous development and refinement of instrumentation and analytic techniques, it has made many notable contributions to geological knowledge. Initially it focused on the tectonic problem of “continental drift” and by developing apparent polar wander paths for the different continents it documented incontrovertibly the mobility of the continents. Matching of APW paths led to the reconstruction of supercontinents such as Rodinia, Pangea, and Gondwana. In parallel to this work, paleomagnetic analysis in conjunction with geological dating worked out the history of geomagnetic reversals. On the basis of the established reversal history and the rock magnetic properties of oceanic basalts, the hypothesis of seafloor spreading was developed. This development provided the key to the mechanism of plate tectonics and allowed the documentation and dating of plate motions, and explained how “continental drift” took place. In turn, the pattern of magnetic reversals in the oceanic crust along with magnetostratigraphy established a dated sequence of geomagnetic polarity history for the past 160 Ma. The methods of paleomagnetism and rock magnetism have found wider application in addressing environmental problems and in contributing to an understanding of paleoclimatic history.