DID THE MEDITERRANEAN SEA DRY OUT DURING THE MESSINIAN SALINITY CRISIS? A LESSON FROM THE LEVANT BASIN

The Levant Basin is the only deep Mediterranean basin where the entire section representing the Messinian Salinity Crisis (MSC) has been penetrated by wells tied to high-resolution 3D seismic surveys. Based on the new data from the Levant, a series of recent studies challenge the desiccation paradigm dominating the MSC literature for >50 years.

The first study (Gvirtzman et al., 2017) identified the transition from Stage 2 to Stage 3 of the MSC as an Intra-Messinian Truncation Surface (IMTS), separating the nearly 2 km thick salt sequence from the overlying ~100 m thick upper clastic-rich anhydrite unit. The origin of the flat IMTS was interpreted as a result of submarine dissolution in odds with previous interpretations that argued for subaerial erosion.

Two following studies (Manzi et al., 2018, 2021) identified the Stage 1 deposits below the salt as a 10s-of-m thick (below seismic resolution) foraminifera barren interval (FBI), composed of shales with no evaporites. This unit indicates that during Stage 1, salinity in the deep basin progressively increased and marine organisms gradually disappeared, but still with no salt deposition.

The identification of Stage 1 deposits (shale) below the salt and Stage 3 deposits (sand+shale+anhydrite) above the salt, leads to the conclusion that the entire salt sequence was deposited during Stage 2, i.e., within a short period of 60 kyr. At that time, sedimentation rate jumped by three order of magnitude compared to the pre- and post-MSC deposits, reaching a few cm/yr like the modern Dead Sea and artificial salinas.

Following the suggestion that the top salt was truncated in deep waters by dissolution, Moneron and Gvirtzman (2022) further showed that the Stage 3 unit overlying the truncation surface contains a dense net of channels, characterized by submarine aggradation characteristics (levee height, channel depth, and channel-floodplain coupling). This adds up to the conclusion that evidence previously interpreted as indications for subaerial exposure (erosion and fluvial channels), are better explained by submarine processes (dissolution and turbidite channels).

Finally, based on the reconstruction of the Messinian Nile River, Gvirtzman et al. (2022) estimate the amplitude of the MSC sea-level drop by ~600 m. Accordingly, salt was deposited in a water depth of >1 km in the Levant Basin and probably >2 km in the Herodotus Basin.