A new geomagnetic polarity time scale for the late Cretaceous and Cenozoic

Abstract

We have constructed a magnetic polarity time scale for the Late Cretaceous and Cenozoic based on an analysis of marine magnetic profiles from the world's ocean basins. The new time scale has several significant differences from previous time scales. For example, chron C5n is ~0.5 m.y. older and chrons C9 through C24 are 2-3 m.y. younger than in the chronologies of Berggren et al. (1985b) and Harland et al. (1990). Additional small-scale anomalies (tiny wiggles) that represent either very short polarity intervals or intensity fluctuations of the dipole field have been identified from several intervals in the Cenozoic. Spreading rates on several ridges were analyzed in order to evaluate the accuracy of the new time scale. Globally synchronous variations in spreading rate that were previously observed around anomalies 20, 6C, and in the late Neogene have been eliminated. The new time scale helps to resolve events at the times of major plate reorganizations. -from Authors