A series of previous review articles on paleomagnetic polarity stratigraphy has documented the growth of this field and its passage through various stages of development, in which work was concentrated on young lavas, young deep‐sea sediments from piston cores, and red beds Cox, 1969; Larson and Helsley, 1975; Opdyke, 1972; Harrison, 1974; Irving and Pulliah, 1976; Butler and Opdyke, 1979. The closely related development of the geomagnetic reversal time scale has been reviewed by Ness et al. 1980. At the time of the last quadrennial U.S. National Report, Butler and Opdyke 1979 noted that the recent development of digital spinner and cryogenic magnetometers was making it possible to measure large numbers of very weakly magnetized samples. In the last four years cryogenic magnetometers have been acquired by many laboratories and studies of magnetic stratigraphy involving stepwise demagnetization of hundreds of samples have become fairly common. In view of the time and effort that go into a careful study of paleomagnetic stratigraphy, it seems unlikely that this technique will ever become as routine a correlation tool as biostratigraph
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