Cyclostratigraphy and astrochronology of the Tripolo diatomite formation pre-evaporite Messinian, Sicily, italy)

The ongoing debate about the Messinian salinity crisis in the Mediterranean is fuelled in part by the lach of an adequate time control. The most accurate and, at the same time, detailed constrains are nowadays provided by the astronomical dating technique. Here we present an astronomical age model for the cyclically bedded Tripoli diatomite Formation on Scily pre-evaporite Messinian, Italy) based on an intergrated stratigraphic study of three key sections, Falconara, Gibliscemi and Capodarso. Characteristic sedimentary cycle pattenrs allow i) the sections to be cyclostratigraphically correlated, the 'bed-to-bed' correlations being confirmed by high-resolution planktonic foraminiferal biostratigraphy, and ii) the Tripoli cycles to thecalibrated to the astronomical record. Despite minor misfits the correctness of thetuning is evident from the match between precession-obliquity interference in the astronomical target and its reflection in the sedimentary cycle record. The tuning provides absolute astronomically dated at 7.005 Ma, indicating that the onset of diatomite formation is diachronous in the mediterranean since itstarted 300 000 years earlier on Sicilt than on Gavdos, south of Crete. The top of the Tripoli, and thus the onset of the salinity crisis proper on Sicily, arrives at 5.98 Ma