This paper summarizes the results of the three previous papers in this series, which have shown the presence of a pattern of magnetic anomalies, bilaterally symmetric about the crest of the ridge in the Pacific, Atlantic, and Indian oceans. By assuming that the pattern is caused by a sequence of normally and reversely magnetized blocks that have been produced by sea floor spreading at the axes of the ridges, it is shown that the sequences of blocks correspond to the same geomagnetic time scale. An attempt is made to determine the absolute ages of this time scale using palcomagnetic and paleontological data. The pattern of opening of the oceans is discussed and the implications on continental drift are considered. This pattern is in good agreement with continental drift, in particular with the history of the break up of Gondwanaland.

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Four magnetic profiles across the Pacific-Antarctic Ridge reveal magnetic anomalies that show trends parallel with the ridge axis and symmetry about the ridge axis. The distribution of bodies that could cause these anomalies supports the Vine and Matthews hypothesis for the generation of patterns of magnetic anomalies associated with the midocean ridge system. The geometry of the bodies accords with the known reversals of the geomagnetic field during the last 3.4 million years, indicating a spreading rate of the ocean floor of 4.5 centimeters per year. If one assume that the spreading rate within 500 kilometers of the ridge axis has been constant, reversals of the geomagnetic field during the last 10.0 million years can be determined. This new, detailed history of field reversals accords with observed anomalies over Reykjanes Ridge in the North Atlantic if a spreading rate of 1 centimeter per year is assumed there.

The symmetric linear magnetic pattern found over the crest of the Pacific‐Antarctic and Juan de Fuca ridges can now be traced across the flanks and into the basins in the North and the South Pacific Ocean. The bilateral symmetry is best shown in the South Pacific, where the western half of the pattern can be traced to the edge of the New Zealand plateau. The eastern half extends to at least 90°W at 62°S. Although sections of the pattern south of the ridge axis have not yet been mapped because of the difficulties of data collection in antarctic waters, sufficient marine data are available to compile a magnetic map of these linear anomalies in the South Pacific from 35° to 65°S and from 90°W to 175°E. In the North Pacific, the eastern half of the symmetric pattern is generally masked by the North American continent. The complete axial pattern can be observed only in the area north of the Mendocino fracture zone. The western half of the pattern is, however, identical to that observed in the South Pacific to the west of the ridge axis. The North Pacific pattern extends from 51° to 25°N and from the edge of the continental rise as far west as 165°W at 51°N. Previous work has shown that the axial magnetic anomaly pattern correlates with the known history of reversals of the, earth's magnetic field. It is now possible to correlate between contemporaneous regions in the North and South Pacific and to assign relative ages to over one‐half the Pacific basin.