SAWTOOTH PALEOINTENSITY AND REVERSALS OF THE GEOMAGNETIC-FIELD

Valet and Meynadier (Valet, J.P., Meynadier, L., 1993) noted an intrig uing sawtooth intensity pattern in sequences drilled during Leg 138 of the Ocean Drilling Program. The pattern is an almost linear decrease in intensity during stable polarity times followed by a rapid recovery or increase in intensity immediately after a reversal. They further n oted an apparent correlation between the size of the intensity of the recovery and the length of the subsequent polarity chron and inferred that reversals are a consequence of a progressive degradation of the d ipole field in that a strong dipole field inhibits a future reversal. This has significant potential implications for dynamo theory. However , their hypothesis implies that the nonstationarity in reversal rate d uring the Cenozoic is controlled by inhibition, and so their hypothesi s is immediately testable using the available reversal chronology. Ana lysis of the chronology shows that the hypothesis is not sustainable. Crown copyright (C) 1997 Published by Elsevier Science B.V.