Until recently, studies of the geomagnetic polarity time scale were confined for the most part to the problem of defining the broad structure of the polarity history for the period t = 0 to 6 m.y. Now that this is well advanced, two interrelated directions of research are evolving: the problem of the fine detail of the geomagnetic history is beginning to attract active interest, and the time scale is poised for widespread utilization as the time framework for research on the various phenomena represented in deep-sea sedimentary cores and in outcrops of diverse sediments on land. These latter applied studies are in turn capable of contributing to definition of the polarity scale, but are also very easily capable of distorting the known polarity scale unless rigorous criteria are applied to distinguish polarity changes from other geomagnetic behavior and spurious data. It is therefore appropriate at this time to review the history of the development of the polarity time scale and some of its initial applications to ocean-crust dating, deep-sea sedimentary core studies, and work on continental sediments, in order to illustrate the great vulnerability of the time scale to circular reasoning and the difficulty of reliable interpretation of limited amounts of data. Special attention is paid to the problem of defining short polarity events. This is most efficiently demonstrated by focusing discussion on the polarity history between t = 0 and 2.6 m.y.
The nomenclature conventions and some associated ambiguities are also reviewed. It is concluded that the establishment of an international commission or panel for guiding the acceptance of new and revised details of the polarity history and its nomenclature will be of substantial value in maintaining the future coherence of the polarity scale. This would provide the essential control for resolution with minimum ambiguity of the various geological and geophysical phenomena examined within the framework of the geomagnetic polarity time scale.