The Messinian volcaniclastic layers of the Northern Apennines: evidence for the initial phases of the Southern Tyrrhenian spreading?

A petrological investigation has been carried out on the Late Miocene (around 5.5 Ma) volcaniclastic layer interbedded in the uppermost Messinian deep-water sediments of the Northern Apennines foredeep basin. The studied samples derive from five sections located on a 200 km long area and reveal that the volcaniclastic layer corresponds to centimetric- to metric-thick turbiditic sequence, essentially composed of lapilli to ash-sized glass shards and scarce (