New magnetostratigraphic and 40Ar39Ar dating results from the Suva Marl, Fiji: Calibration of the Early Pliocene geomagnetic polarity time scale

The Suva Marl (Fiji) provides a rare opportunity to integrate Early Pliocene biostratigraphic, magnetostratigraphic and chronostratigraphic data. We present new paleomagnetic data that extend the previously reported magnetostratigraphy [P. Rodda, I. McDougall, R.A. Cassie, D.A. Falvey, R. Todd, J.A. Wilcoxon, Isotopic ages, magnetostratigraphy, and biostratigraphy from the Early Pliocene Suva Marl, Fiji, Geol. Soc. Am. Bull. 96 (1985) 529–538] of the Suva Marl down section, and suggest a revision of the original correlation with the geomagnetic polarity time scale (GPTS). 40Ar39Ar laser incremental-heating analyses of mineral separates from the interbedded tuffs yield refined age constraints for previously reported KAr dates for the Suva Marl polarity reversals. The new dates and the new magnetostratigraphic data are most consistently interpreted as supporting the revised Early Pliocene polarity time scale [W.A. Berggren, D.V. Kent, C.C. Swisher III, M.P. Aubry, A revised Cenozoic geochronology and chronostratigraphy, in: W.A. Berggren, D.V. Kent, M.P. Aubry, J. Hardenbol (Eds.), Geochronology, Time Scales and Global Stratigraphic Correlation, Soc. Econ. Paleontol. Mineral. Spec. Publ. 54 (1996) 129–212]. The ages of the Suva Marl reversals derived from the 40Ar39Ar dates provide a revised direct calibration of the early Pliocene GPTS, bringing it in synch with those calibrations produced by orbital tuning of Milankovitch cycles (astronomical time scale).