Improved astronomical age constraints for the middle Miocene climate transition based on high-resolution stable isotope records from the central Mediterranean Maltese Islands

Marine outcrops of the Globigerina Limestone and Blue Clay formations on the Maltese Islands in the central Mediterranean document the middle Miocene climate transition between similar to 15 and 13.5 million years ago. Here high-resolution benthic and planktic oxygen isotope records have been constructed for this enigmatic interval in Cenozoic climate evolution. Detailed biostratigraphic correlations to the astronomically tuned La Vedova section in northern Italy allow revision of the tuning of the Blue Clay Formation, constraining the age of the sediments directly above the formation boundary and hence the Mi-3b oxygen isotope event and Serravallian Global Stratotype Section and Point (GSSP). Biostratigraphic age control and cyclic patterns in the benthic carbon isotope record further lead to an astronomically-tuned age model for the Upper Member of the Globigerina Limestone Formation. Start of sedimentation of the Upper Globigerina Limestone is dated at similar to 14.95 Ma, and the oldest Blue Clay sediments have a revised astronomical age of 13.76 +/- 0.02 Ma. Our data indicates that a hiatus between 13.95 and 13.76 Ma cannot be excluded and could have implications for the Serravallian GSSP currently defined in this section. The global middle Miocene cooling is reflected in the benthic oxygen isotope record, showing a similar to 0.6% increase (Mi-3b) between similar to 13.95 and 13.76 Ma. A divergence between the planktic and benthic oxygen and carbon isotope records after 13.76 Ma could point to a decrease in ventilation, possibly related to increased fresh water influx after the climate transition.