THE AGE OF THE TORTONIAN MESSINIAN BOUNDARY

The Tortonian/Messinian boundary is marked by the first occurrence datum (FOD) of Globorotalia conomiozea which is found all over Crete in open-marine marls with good palaeomagnetic properties. Within the framework of the MIOMAR project, the previously studied sections of Langereis et al. [1] have been extended and (partly) resampled. Here, we present new magnelostratigraphic and biostratigraphic results from sections on eastern Crete (Faneromeni), central Crete (Kastelli) and western Crete (Potamida and Skouloudhiana) supplemented by cyclostratigraphic data. The recently developed geomagnetic polarity time scale (CK92) of Cande and Kent [2] allows an unambiguous correlation of the polarity sequences on Crete. The FOD of G. conomiozea occurs in the reversed interval of anomaly C3Bn.1r. This leads to a new age determination of 6.92 Ma for the Tortonian/Messinian boundary and a duration of 1.76 Myr for the Messinian. A slightly modified version of CK92-if we use more recent age estimates-provides an age of 7.10 Ma and a duration of 1.78 Myr, respectively. Bipartite sedimentary cycles are distinctly present in the Cretan sections studied. Assuming that these cycles are precession-induced and using an average periodicity of 21.7 kyr enables us to independently estimate the duration of the successive individual polarity zones. The astronomically derived durations of the Cretan polarity zones are in good agreement with CK92, but are approximately 10% shorter.