A revised magnetic polarity timescale for the Cretaceous and Cainozoic

Abstract

Magnetostratigraphic correlations of biostratigraphic stage boundaries have established calibration points for dating the polarity reversal sequence derived from marine magnetic anomalies. Interpolation between the best-estimate ages for these tie points gives a revised magnetic polarity timescale for the Cainozoic and Cretaceous. Recomputed sea-floor spreading rates for this time prove to be high during the Cretaceous quiet interval at several plate margins, but remained remarkably constant in the central Atlantic. The geomagnetic reversal frequency, when averaged over intervals of several megayears duration, has exhibited a steadily increasing trend since the late Cretaceous.