Astronomical Calibration of the Danian Formation of Ndayane : Paleogeographic and Paleoclimatic Implications

Résumé

The previous studies of the Formation of Ndayane, that collected a wide set of lithological and biostratigrahic data, as the existing species of benthic and planktonic foraminifera or pelagic index, has been revisited. In fact, he analysis of these data gave general indications on the age of the formation that was dated from Mid to Late Danian. In this work, the available pelagic indices of the Formation of Ndayane are correlated with La2004 numerical solution of eccentricity and insolation. The principle of the correlation is based on the established relation between pelagic index, eccentricity and eustatism. The correlation of eccentricity with insolation is more obvious. The performed correlation allows showing that the pelagic index is well correlated to eccentricity and that the thickness of limestone beds is also correlated to the insolation amplitude. Warmer climate corresponds to thicker limestone beds. Moreover, the method allowed more accurate dating of the Formation of Ndayane, as the first limestone bed at the bottom of the Popenguine cliff can be dated at 64.32 MA.