Get access
Eos, Transactions American Geophysical Union

Geomagnetic reversals and long-period secular variation

Authors


Abstract

A number of notable contributions to our knowledge of long-period fluctuations of the geomagnetic field have been made since 1967 through studies of the paleomagnetism of igneous and sedimentary rocks. The highlights of this research include the following: (1) A more accurate radiometric time scale of geomagnetic reversals has been developed for the past 5 m.y., with the result that during this time all polarity intervals with durations longer than 50,000 years have probably been recognized. (2) An intensive study of deep-sea sedimentary cores has served to define this time scale more accurately and to extend it back in time well beyond 5 m.y. (3) Marine magnetic anomalies have been analyzed by using the theory of sea-floor spreading to yield a reversal time scale extending back 70 m.y. (4) Long-period geomagnetic secular variation within individual polarity intervals has been investigated paleomagnetically by studying paleointensities and by measuring variations in angular dispersion of directions of the earth's field as a function of latitude. In the present report all these subjects are reviewed with the exception of marine magnetic anomalies, which are discussed in a separate report. In addition to the references cited specifically in the text, numerous important papers relevant to these subjects are listed in the bibliography.

Get access to the full text of this article

Ancillary