A team led by Giovanni Aloisi, CNRS researcher and geochemist at IPGP, highlights the significant drop in the level of the Mediterranean Sea during the Messinian salinity crisis, a major geological event which transformed the Mediterranean into a gigantic saline basin between 5 .97 and 5.33 million years ago.
How a million cubic kilometers of salt accumulated on the Mediterranean ocean floor in a short period of time was previously unknown. Through an analysis of isotopes of chlorine contained in the salts extracted from the bottom of the Mediterranean, scientists have traced the two phases of this extreme drying.
In a first phase, around 35,000 years ago, salts were deposited in the eastern part of the Mediterranean due to a partial restriction of its flow towards the Atlantic.
During a second, shorter phase (less than 10,000 years), salts accumulated throughout the Mediterranean, causing a rapid drying of the sea, with a drop in water levels of 1. 7 to 2.1 kilometers in the eastern Mediterranean and about 850 meters in its western part. Thus, the Mediterranean basin lost up to 70% of its volume of water.
Artistic representation of the rupture of the Gibraltar threshold at the end of the Messinian salinity crisis. In the final moments of this crisis, the level of the Mediterranean Sea is approximately one kilometer lower than that of theAtlantic Ocean.
© Pibernat & Garcia-Castellanos
This spectacular drop in sea level would have had consequences on terrestrial fauna and the Mediterranean landscape. She would also have triggered volcanic eruptions in this region due to the relief of the earth’s crustand would have generated climatic effects on a global scale linked to the depression thus created.
These results, published in the journal Nature Communicationsprovide a better understanding of past extreme geological phenomena, the evolution of the Mediterranean region and its repercussions on a global scale.
The two phases of accumulation of the Mediterranean salt layer during the Messinian salinity crisis. During the first phase, salt accumulated in a brine-filled Mediterranean basin; in the second phase, salt accumulated in a Mediterranean completely isolated from theocean Atlantic under the effect of the significant drop in sea level in the western and eastern Mediterranean sub-basins.
© Giovanni Aloisi
Notes:
– This exceptional event covered the depths of the Mediterranean with a layer of salt up to three kilometers thick. Understanding the causes, consequences and environmental modifications suffered by the Mediterranean region in response to the Messinian salinity crisis is a challenge that has mobilized the scientific community for decades.
– The analysis of the two stable isotopes of chlorine (³⁷Cl and ³⁵Cl) makes it possible to estimate the rate of salt accumulation and to detect any drop in sea level.
Reference:
Nature Communications (2024).
DOI: 10.1038/s41467-024-53781-6
G. Aloisi, J. Moneron, L. Guibourdenche, A. Camerlenghi, I. Gavrieli, G. Bardoux, P. Agrinier, R. Ebner et Z. Gvirtzman, Chlorine isotopes constrain a major drawdown of the Mediterranean Sea during the Messinian Salinity Crisis.
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