Successive palaeomagnetic reversal records from Kauai

Abstract

Geomagnetic field reversal is a rapid phenomenon1,2, perhaps taking only a few thousand years. Knowledge of how the field behaves during these brief and active periods may eventually help to constrain theories of the geodynamo and thus inform us about conditions in the Earth's core. Unfortunately, reliable and detailed palaeomagnetic records of transitional field behaviour are few, almost entirely from Northern Hemisphere sites, and heavily biased toward reversals of the reverse–normal (R–N) sense. We report here new data from basalts on the island of Kauai, Hawaii, which have recorded successive R–N and N–R field reversals. The sequences of changing field directions for the two reversals are very similar, as would be expected if a standing nondipole component controlled the transitional field. The data are also consistent with zonal flooding models in which the reversal process depends on the sign of the field. Other reversal records, however, cannot be explained by these same models unless the standing field or flooding process changes between some reversals.