Refining the Mediterranean "Messinian gap" with high-precision U-Pb zircon geochronology, central and northern Italy

""During the Messinian Salinity Crisis (MSC), the Mediterranean Basin recorded a well developed precessionally modulated cyclicity. The astronomical tuning of the Messinian deposits with the insolation curve reveals a ~90 kyr “Messinian gap”, corresponding to the evaporative draw down of the Mediterranean, with consequent erosion of the basin margins. and formation of the Messinian Erosional Surface (MES). In the Messinian deposits above. the MES, a distinctive volcanic ash bed with a biotite 40Ar\\\/39 Ar plateau corrected date of 5.50 ±0.04 Ma has been used to constrain the post-evaporitic phase of the MSC and to tune the sedimentary cycles to the insolation curve. Using high-precision CA-TIMS U-Pb dates on single zircon grains derived from two post-MES ash layers sampled in northern and central Italy, we obtained dates of 5.5351 ± 0.0051 Ma and 5.5392 ± 0.0088 Ma, respectively. Combining the new high-precision geochronology with the age model for the precessionally modulated cycles of the Messinian Lower Evaporites, we refine the duration of the “Messinian gap” to 50 kyr or less, which correlates with either the TG12 glacial interval alone, or both the TG12 and TG14 glacial intervals. This gap should encompass the draw down of the Mediterranean, its near-complete desiccation, and deposition of the thick Messinian halite layer.""