Calcareous nannofossil biostratigraphy, biochronology and paleoecology at the Tortonian/Messinian boundary of the Faneromeni section (Crete)

A detailed calcareous nannofossil analysis was performed on 180 samples from the astronomically dated Faneromeni section to identify the most important calcareous nannofossil events across the Tortonian/Messinian (T/M) boundary in the Mediterranean and to date and correlate them precisely to the previously observed sections. Here we confirm the reliability of the genus Amaurolithus, the successive entries of Amaurolithus primus, Amaurolithus aff. amplificus and Amaurolithus delicatus, have been dated at 7.430, 7.388 and 7.250 Ma, respectively. The first occurrence and the first common occurrence of Reticulofenestra rotaria are further confirmed bioevents, dated at 7.421 and 7.264 Ma. These events improve the biostratigraphic resolution in the T/M boundary interval, at least for the Mediterranean. Quantitative analysis revealed marked changes in the calcareous nannofossil assemblage associated with the sapropels as previously observed in other sections of the same time interval. A decrease in the total number of coccoliths, but an increase in abundance of the genera Rhabdosphaera and Helicosphaera characterize sapropels. The observed fluctuations are comparable to the previous findings in Neogene Mediterranean sapropel sediments and suggest that similar mechanisms were responsible for their formation during this interval. The possible influence of preservation on nannofossil assemblages is discussed.