Land-to-sea indicators of the Zanclean megaflood

Abstract

One debated scenario for the termination of the Messinian salinity crisis at 5.33 Ma is cataclysmic refilling of the Mediterranean Sea by the Zanclean megaflood. Here we present a clear line of onshore-to-offshore evidence for this megaflood, and its spillover across a shallow-water marine corridor in SE Sicily and into the nearby subaqueous Noto Canyon: (i) >300 asymmetric and streamlined ridges aligned with the megaflood direction, (ii) poorly-sorted breccia between the Messinian and Lower Zanclean Trubi Formations, (iii) soft-sediment deformation structures and clastic injections in the breccia and underlying units, and (iv) a 20 km wide erosional shelf channel connecting the ridges with Noto Canyon. Numerical modelling results support the modulation of flow velocity and direction by the excavation of the channel and Noto Canyon. Our findings demonstrate that the Messinian salinity crisis was terminated through a cataclysmic flood, which implies significant Mediterranean sea-level drawdown prior to the flooding.

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