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 fro m the astronomically dated Faneromeni section to identify the most importan t calcareous nannofossil events across the Tortonian/Messinian (T/M) bounda ry in the Mediterranean and to date and correlate them precisely to the pre viously observed sections. Here we confirm the reliability of the genus Ama urolithus, 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 occurren ce of Reticulofenestra rotaria are further confirmed bioevents, dated at 7. 421 and 7.264 Ma. These events improve the biostratigraphic resolution in t he T/M boundary interval, at least for the Mediterranean. Quantitative anal ysis revealed marked changes in the calcareous nannofossil assemblage assoc iated with the sapropels as previously observed in other sections of the sa me time interval. A decrease in the total number of coccoliths, but an incr ease in abundance of the genera Rhabdosphaera and Helicosphaera characteriz e sapropels. The observed fluctuations are comparable to the previous findi ngs in Neogene Mediterranean sapropel sediments and suggest that similar me chanisms were responsible for their formation during this interval. The pos sible influence of preservation on nannofossil assemblages is discussed. (C ) 2000 Elsevier Science B.V. All rights reserved.