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.

Magnetic profiles across the South Atlantic Ocean from the Rio Grande rise and Argentine basin to the southwest coast of Africa and between 25° and 50°S are presented. Anomalies have been correlated from profile to profile, and the resulting magnetic pattern is parallel to and symmetric about the axis of the mid‐Atlantic ridge. The observed magnetic pattern in the South Atlantic Ocean is very similar to the pattern observed across the East Pacific rise in the Pacific Ocean. The results have been interpreted as supporting ocean floor spreading and the hypothesis of Vine and Matthews for the origin of the anomalous field. Possible fracture zones, the Rio Grande rise, and the Walvis ridge are discussed.

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