Magnetic reversals and mass extinctions

Previous analyses of the time distribution of reversals of the Earth's magnetic field have yielded mixed results. Some authors have claimed significant periodicities of order 10⁷ yr^1,2 whereas others have reported failure to reject null hypotheses of random spacing at that scale^3-6. Because of repeated suggestions that field reversal is linked to biological extinction^7-12, further analysis of the magnetic time series is appropriate. I present here the results of a study of the reversal record of the past 165 Myr. A stationary periodicity of 30 Myr emerges (superimposed on the non-stationarities already established by others⁵), which predicts pulses of increased reversal activity centred at 10, 40, 70,... Myr BP.