No abstract

During the Messinian Salinity Crisis (MSC, 5.97–5.33 Ma), thick evaporites were deposited in the Mediterranean Sea associated with major margin erosion. This has been interpreted by most authors as resulting from water level drop by evaporation but its timing, amplitude and variations between subbasins are poorly constrained due to uncertainty in post‐Messinian vertical motions and lack of a clear time‐correlation between the marginal basin and offshore records. The Balearic Promontory and surrounding basins exemplify a range of responses to this event, from margin erosion to up to a kilometre thick Messinian units in the abyssal areas containing the majority of the MSC halite. The Balearic Promontory contains unique patches of halite with thickness up to 325 m at intermediate depths that provide valuable information on water level during the stage of halite deposition. We compile seismic markers potentially indicating ancient shorelines during the drawdown phase: the first is marked by the transition from the MES to UU based on seismic data. The second is the limit between the bottom erosion surface (BES) and abyssal halite deposits. We restore these shorelines to their original depth accounting for flexural isostasy and sediment compaction. The best‐fitting scenario involves a water level drop of ca. 1,100 ± 100 m for the Upper unit level and 1,500 ± 100 m for the BES level. According to our results, halite deposition began in the Central Mallorca Depression at 1,300–1,500 m depth, perched hundreds of metres above the deep basins, which were at 1,500–1,800 m (Valencia Basin) and >2,900 m (Algerian Basin). The hypothesis that erosion surfaces were formed subaerially during the drawdown phase is consistent with a model of halite deposition before/during the water level drop of at least 1,000 m, followed by the deposition of the Upper unit until the MSC is terminated by the reinstatement of normal marine conditions.

No abstract

The extreme Mediterranean sea-level drop during the Messinian salinity crisis has been known for >50 years, but its amplitude and duration remain a challenge. Here we estimate its amplitude by restoring the topography of the Messinian Nile canyon and the vertical position of the Messinian coastline by unloading of post-Messinian sediment and accounting for flexural isostasy and compaction. We estimate the original depth of the geomorphological base level of the Nile River at ~600 m below present sea level, implying a drawdown 2–4 times smaller than previously estimated from the Nile canyon and suggesting that salt precipitated under 1–3 km deep waters. This conclusion is at odds with the nearly-desiccated basin model (>2 km drawdown) dominating the scientific literature for 50 years. Yet, a 600 m drawdown is ca. five times larger than eustatic fluctuations and its impact on the Mediterranean continental margins is incomparable to any glacial sea-level fall.