POLAR WANDERING AND CONTINENTAL DRIFT: AN EVALUATION OF RECENT EVIDENCE

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Abstract
In rocks free from directional characteristics, thermal treatment since their origin or recent weathering, there is every reason to expect the present natural remanent magnetization to be in the same direction, after correction for geological dip, as the geomagnetic held at the time of the formation of the rocks, provided the ferromagnetic grains have sufficiently high coercivities. The theory of the geomagnetic field predicts that its mean, after the removal of the geomagnetic secular variation, has always been symmetrical about the rotational axis of the earth. There are also reasons for believing that this mean field should have always been that of a geocentric dipole. Consequently, from the palaeomagnetic survey of the geological column in the various continents the positions of the poles throughout geological time can be plotted. In the Cenozoic they are in close agreement with the present poles, but prior to this era the poles have migrated with respect to the continents. Because the poles’ wandering curves from the different continents do not agree, it is believed that the continents have drifted apart. An attempted reconstruction will be described. The possibility that the field has been non-dipolar at times in the past will be discussed and shown to be inconsistent with the palaeomagnetic data. The palaeoclimatic data will be discussed, and shown to give general support to the inferences drawn above. An explanation of polar wandering and continental drift in terms of thermal convection in the earth’s mantle will be given.

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