6.2 Million Years Ago: A Cataclysm Transformed the Red Sea Into a Desert

Turquoise waters and its coral reefs evoke a prosperous ecosystem. However, the Red Sea has experienced a total environmental collapse. A study by researchers from the King Abdullah University of Sciences and Technologies in Saudi Arabia reveals that around 6.2 million years ago, the basin has emptied all of its water, turning into a saline desert swept by winds. This upheaval occurred when the Mediterranean Sea entered the famous Messinian salinity crisis, a massive evaporation phase which also affected the marine exchanges between basins.

Thanks to seismic imaging techniques, geochemical dating and microfossil analysis, the researchers highlighted a vast desiccation event. The totally urged sea floor was subjected to intense erosion. The study, published in the journal Communications Earth & Environment, shows that a continuous geological surface, called a reflector S, testifies to this massive ablation phase which remodelled the structure of the basement over several hundred meters.

In some areas, the winds and surface runoffs have plated the saline deposits of the Mansiyah formation by almost a kilometer in thickness. The Red Sea, then isolated from the Mediterranean by the North, no longer received any water supply. Intense evaporation and aridity of the climate then sculpted a gigantic pool of evaporites, which natural elements have gradually leveled.

The brutal return of the waters and its visible traces today

The situation changed when the waters of the Indian Ocean crossed the volcanic threshold which closed the south of the Red Sea, at the Hanish archipelago. This crossing was not smooth. According to the authors, a dazzling marine flood swept through the desert basin, digging a 320 kilometers long-term canyon still visible on modern Bathymetric maps. This phenomenon, described as a cataclysm, would have allowed the Red Sea to reconnect to the globe oceans, long before the later reconnection of the Mediterranean by the Strait of Gibraltar.

The violence of this deluge covered the strata of evaporites with a fossil -rich marine deposit. The carrots extracted from the well A, drilled more than a thousand meters deep, reveal a steep transition between sterile anhydrites and fossiliferous limestones containing red algae, foraminifera and tubicole verses. These indices confirm the rapid return to normal marine conditions, in less than 100,000 years. This spectacular reconfiguration has revived a sterile basin, laying the foundations for the current ecosystem.

In the most recent sediments, researchers have also found traces of the foraminifera Borelis Schlumbergerian emblematic species of Indo-Pacific, completely absent from the Mediterranean archives. This detail confirms that the Red Sea, once flooded, turned south, definitively breaking its links with the Northern Tethys.

From tectonics to ecosystems, a model to understand other basins

The case of the Red Sea far exceeds the framework of a simple local geological story. It offers a natural model of observation of interactions between climate, tectonics and ocean circulation. By slowly separating from the African continent 30 million years ago, the oceanic floor of the Red Sea has sunk, creating an increasingly deep depression. This is how it was able to accumulate several kilometers of salt, then occur the episode of total emptying followed by a spectacular flood.

This extreme scenario sheds new light on the history of closed basins on the planet, and in particular the risks linked to their isolation. The discovery of such a succession of events, as short as it is radical, underlines how great marine balances can switch to the blink of an eye at the geological time scale.

From an ecological point of view, this brutal switch between sterility and abundant life also highlights the resilience of an environment subject to extreme conditions. The Red Sea ecosystem, today among the richest in corals and marine biodiversity, was born in a post-catastrophic environment. As the Kaust team originates from the study relayed by Phys.org, the Red Sea embodies a living laboratory where the history of the land can read its funds.