There are two principal features characterizing the behavior of the geomagnetic field as observed in the study of samples from any given region. Commonly rocks are found with a polarity opposite to that anticipated and the directions themselves indicate an increasing deviation from the present rotational poles with time. The first is interpreted, in most cases, as evidence for the reversal of the geomagnetic field, the second in terms of progressive movement of blocks of continental extent with time (i.e. continental drift).

Although both of these features provide information relevant to the problems of the Permian-Triassic boundary, there is a distinct disadvantage in the small number of reliable results. It is only in recent years that magnetic cleaning has become a standard procedure for all rocks and in consequence many older results, even if they appear reliable, must be looked at with suspicion.

In contrast to the Triassic, the Permian geomagnetic field appears to have been remarkably stable during Permian times, fully justifying Irving's introduction of the "Kaiman Magnetic Interval". Detailed investigation does reveal a number of periods of reversed polarity, although as yet little may be said of their duration. These reversals are more common in the Late Permian than in the Early Permian. It may be coincidental that the Permian-Triassic boundary appears almost to coincide with a change in behavior of the geomagnetic field. If we make use of this, then it may be suggested that from the paleomagnetic standpoint the top half of the Ochoan should be included in the Triassic.

The declination-inclination data provide a means of establishing ancient geography, for the data from nearly all continents imply that considerable displacements must have occurred. This information can be used either as a means of creating paleogeographic maps or as a means of testing configurations arrived at by other means. Whenever there are Permian results from many horizons in a given region they can be interpreted satisfactorily by a single pole position although this is not necessarily so for all regions. For Triassic rocks we have concentrated upon results from the Lower Triassic whenever possible, but more general "Triassic" results must be used for some regions with the consequent introduction

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of errors which may be appreciable. Models due to Dietz, Du Toit, and others have been examined in the light of the paleomagnetic data and the most consistent of these paleogeographic models is presented for Permian and Early Triassic times.

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