During the Messinian Salinity Crisis (MSC) 5.96 to 5.33 million years ago, the Mediterranean Sea was cut off from the Atlantic Sea, which led to a period of extreme evaporation. This event transformed the Mediterranean into a gigantic salt basin.
Researchers were still unsure about the process that led to a dramatic drop in Mediterranean waters. Geologists debate whether the MSC was accompanied by a major sea level reduction or not.
A new study conducted by CNRS could solve the long-running enigma. By analyzing the chlorine isotopes from Mediterranean seabed salt, researchers were able to identify two phases of the extreme evaporation period.
The first period lasted approximately 35 thousand years and witnessed the halting of the free flow of Mediterranean waters into the Atlantic. During this period, salt deposition increased but only in the eastern Mediterranean.
To back this claim, researchers analyzed 60 drill cuttings from the Aphrodite well located in the eastern Mediterranean. During their drill to the topmost 140m, the team found that the abundance of halite decreased, meanwhile, the other minerals increased. This indicates the isolation of the Mediterranean from the Atlantic Ocean
The second period, lasting less than 10,000 years, was the age of rapid evaporation. As the inflow of Atlantic water was blocked, the Mediterranean water level started to fall. The entire basin dropped until the depth of the Sicily sill was reached.
Sicily sill is a submerged ridge that separates the western and eastern Mediterranean Sea. Ahead of the Sicily sill, the sea level dropped independently in the eastern and western basins.
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The water level in the eastern Mediterranean dropped by 1.7–2.1 km, while in the western Mediterranean, it dropped by approximately 0.85 km. This geological event led to a 70% water loss from the entire Mediterranean Basin.
“Our results solve a controversy regarding the mode of halite precipitation – deep basin, deep water vs deep basin shallow water – that is outstanding since the discovery of the deep basin evaporites,” says the study.
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Journal Reference
- Aloisi, G., Moneron, J., Guibourdenche, L., Camerlenghi, A., Gavrieli, I., Bardoux, G., Agrinier, P., Ebner, R., & Gvirtzman, Z. (2024). Chlorine isotopes constrain a major drawdown of the Mediterranean Sea during the Messinian Salinity Crisis. Nature Communications, 15(1), 1-8. DOI: 10.1038/s41467-024-53781-6
