Geological and geophysical implications of paleomagnetic results from Africa

Publisher Website
Google Scholar
Abstract
A critical review of all African paleomagnetic results has yielded 31 sets of data that are useful for discussions of the behavior of the paleomagnetic field and of polar wandering and continental drift. Most of the reliable data are new. They largely confirm the previously published polar‐wander path relative to Africa for Permian and younger time and add detail particularly about rates of polar shift relative to that continent. They permit a tentative extension of the polar‐wander path back to about 600 m.y. (beginning of Cambrian time). A complete revision of the previously published Precambrian polar‐wander curve is presented in two parts, covering the periods from 2700 m.y. to about 2100 m.y. and from 2000 m.y. to 1300 m.y., respectively. For these two periods it is possible to use paleomagnetism as a tool in geological correlation and as a means of dating. There is still no information on the interval from about 2100 m.y. to 1950 m.y. or for the interval between 1300 m.y. and 600 m.y. The Mesozoic data remain consistent with Du Toit's reconstruction of Gondwanaland for the Jurassic. The Permo‐Carboniferous data confirm the period of rapid drift within the Carboniferous, which has already been identified in Australia by Irving, and confirm the general correctness of the relative positions of Australia and Africa suggested by L. C. King. Comparison of African data with data for the Canadian shield for the period 2000 to 1200 m.y. enables us to suggest tentatively that the Canadian and Southern African cratons did not move relative to each other during that time. This is the first attempt at reconstruction of the relative positions of two continental regions from Precambrian paleomagnetic data. The oldest Precambrian data confirm the existence of a terrestrial magnetic field which occasionally reversed itself at least 2700 m.y. ago. The dispersion of directions in reliable paleomagnetic data is taken as a measure of paleosecular variation; only 3 of the 19 estimates are significantly different from the secular variation associated with the present geomagnetic field.

This publication has 71 references indexed in Scilit: