Magnetization of Basalt of Bed I, Olduvai Gorge, Tanganyika

Abstract

PALÆOMAGNETIC data which bear on the time-scale of geomagnetic polarity epochs are here reported for a radiometrically dated Pleistocene basalt flow in East Africa, The occurrences in various places of stratigraphic groups of rocks which are magnetized either with the sense of the present geomagnetic field (normal polarity) or with the opposite sense (reversed polarity) have been interpreted to mean that the geomagnetic field has reversed itself at various times in the geological past^1,2. The accumulated evidence for the reality of such fteld reversals has recently been reviewed^3,4, and palæomagnetic investigations of radiometrically dated volcanic rocks have permitted a preliminary attempt by Cox et al. to bracket the ages of the most recent reversals⁵.