Glacioeustatic control on the origin and cessation of the Messinian salinity crisis.

Abstract

The desiccation of the Mediterranean during the Messinian salinity crisis (MSC) is one of the most intriguing geological events of recent Earth history. However, the timing of its onset and end, as well as themechanisms involved remain controversial.We present a novel approach to these questions by examining theMSC fromthe Atlantic, but close to theGibraltar Arc, analysing the completeMessinian record of theMontemayor-1 core of theGuadalquivir Basin (SWSpain). Flexural backstripping analysis shows a tectonic uplift trend that would have reduced the depth of the Rifian Corridors considerably. Nonetheless, the rate of tectonic upliftwas insufficient to account for the close up of the corridors. At 5.97 Ma, a global cooling and associated glacioeustatic sea-level drop, estimated in 60 m, is observed. Thiswould have been sufficient to restrict the Rifian Corridors and to trigger theMSC. The later flooding of the Mediterranean occurred during a sea-level rise associated with global warming during a stable tectonic period. We postulate a two-step flooding event: 1) A glacioeustatic sea-level rise during interglacial stage TG 11 (5.52 Ma) led to subtropical Atlantic waters entering the west-central Mediterranean through pathways south of the Gibraltar Strait, probably the Rifian Corridors. 2) A global sea-level drop at 5.4 Ma, thatmight have favoured intensification of regressive fluvial erosion in the Gibraltar threshold, along with the subsequent global sea-level rise would have generated the Gibraltar Strait leading to complete Mediterranean refilling during the earliest Pliocene.