THE MAGNETIC POLARITY STRATIGRAPHY OF A HAUTERIVIAN BARREMIAN CARBONATE SEQUENCE FROM SOUTHERN ITALY/

Remanence directions, measured at 2 cm intervals along a composite 88 m bore-core, enable mean palaeomagnetic poles to be defined at 13.6 de grees S, 25,2 degrees W and 13.6 degrees N, 154.8 degrees E. The direc tions of remanence vary very smoothly away from each palaeomagnetic po le, extending more than 90 degrees from them. This raises doubts about the physical meaning of polarity definitions based on the distance be tween virtual and mean palaeomagnetic poles. For practical purposes, i ntermediate polarity is defined as directions whose virtual poles lie more than 25 degrees from the mean pole, enabling at least five normal subchrons to be specified within the upper predominately reversed qua rter of the core and 11 reversed subchrons within the lower predominan tly normal three-quarters of the core. The stratigraphic thickness bet ween these subchrons shows a very high linear correlation (r > 0.99) w ith the stratigraphic thickness of other terrestrial sequences and the distances between marine polarity sequences of comparable age. The an alysed sequence contains wavelength spectra which, when transformed to the temporal realm, match periodicities determined for three marine m agnetic anomaly profiles of similar age. These also match planetary or bital periodicities for the Cretaceous. These observations suggest tha t secular variations and polarity transitions are driven by common cor e processes whose surface expression is influenced by changes in the p lanetary orbits. Such detailed geomagnetic features enable far greater reliability in establishing magnetostratigraphic correlations and als o enable them to be dated astronomically.