EVIDENCE FROM ICELAND ON GEOMAGNETIC REVERSAL DURING WISCONSINAN ICE AGE

THE discoveries of reversely magnetised basalts in the axial valley of the Mid-Atlantic Ridge1-3 and Cayman Trough4 have added a new facet to the debate about geomagnetic events during the recent Brunhes. Are these reversely magnetised rocks the legacy of a recent geomagnetic event or are they the product of some process of axial valley tectonics which we do not yet understand? We have confirmed the existence of two reversely magnetised lava flows which were erupted subglacially in southwestern Iceland (Fig. 1) and seem to be direct analogues of the reversed rocks in the axial valley. We report here that a recent geomagnetic event is the only mechanism which can explain both the Icelandic and axial valley reversed outcrops. © 1978 Nature Publishing Group.