Land-to-sea indicators of the largest megaflood in the geological record

The termination of the Messinian salinity crisis 5.33 million years ago is often attributed to the Zanclean megaflood, a catastrophic event that rapidly refilled the Mediterranean Sea. This study provides compelling evidence for this megaflood, tracing its impact from an onshore shallow marine corridor in southeastern Sicily to the offshore Noto Canyon. Key indicators include (i) over 300 streamlined, asymmetrical erosional ridges aligned with the flood direction, (ii) a poorly sorted breccia layer situated between the Messinian and Lower Zanclean Trubi Formations, (iii) soft-sediment deformation and clastic injections within the breccia and underlying layers, and (iv) a 20 km-wide erosional channel linking the ridges to Noto Canyon. Numerical modeling reveals how the excavation of the channel and canyon influenced the flow's velocity and direction. These findings confirm that the Messinian salinity crisis ended with a catastrophic flood, highlighting a significant Mediterranean sea-level drop prior to the event.