About six million years ago, the sea Mediterrenian It was a great salt lake, completely cut off from other seas. Such a situation became possible when it dries up after being isolated from the Atlantic Ocean and its level drops by about 1.5 km, giving rise to what is known as the ‘Messinian salt crisis’.
In that period, With the flow of water interrupted by the tectonic closure of the Strait of Gibraltar, water from the Mediterranean was evaporating faster than the rivers could supply.. Gradually, a one kilometer layer of evaporite (gypsum and salt) formed over the entire Mediterranean basin.
It was a time of extreme environmental crisis across the region. ended with megacele It occurred during the Zanclian period, five million years ago, due to the massive influx of Atlantic water into the waterless Mediterranean basin.
Now, geologists from the universities of Utrecht, London and Granada have gathered clues and information about its properties. The megacele is the largest flood the Earth has ever known.
In a newly published investigation in the newspaper sedimentology, The researchers studied the sandstone exposed along the south coast of Sicily and concluded: Formed by a strong eastward flow from the western Mediterranean. At that time, they say, water flowed over a barrier separating the then isolated basins in the western and eastern Mediterranean.
The entire basin was flooded in just a few years
In an article already published in 2009 Naturehow severe the Mediterranean flood was, which With discharges of up to 100 million cubic meters per second (about a thousand times the current Amazon’s average flow) it would happen in just a few years.As described in a later analysis by researcher Daniel García-Castellanos of Geociencias Barcelona (GEO3BCN-CSIC).
García Castellanos spoke later. These “catastrophic” events are “the most important event since the extinction of the dinosaurs”. 65 million years ago”.
One of the questions that expert scientists did not answer during this period was to determine exactly how the waters reached their former levels. Streams from Gibraltar they first flooded the western basin and then filled the eastern region through the Strait of Sicily. from the Mediterranean. The other unknown was its duration, which was estimated to be between a few months and two years.
Tracing the geology
During these years, research in the waters of southern Italy continued. In the Caltanissetta Basin of Sicily, the Arenazzolo Formation is a 5 to 7 meter thick sandy sedimentary range that may reveal a genetic link with the sudden flooding of the Mediterranean.
Thanks to granulometric, petrographic and paleocurrent analyses, The authors were able to calculate on which flanks and by what type of currents the sand at Arenazzolo might have been deposited.. These currents, associated with the active circulation of water bodies, will indicate that the reconnection between the Western and Eastern Mediterranean is created when the basin’s margins overflow.
The source for this latest article was Wout Krijgsman, professor at the University of Utrecht and organizer of the study, who explained that rocks formed during the flood were found off the southern coast of Sicily.
The scientist had been working on the Messinian Crisis for several years, and in 2020 he was intrigued by several meters of sandstone that appeared in the transition between a layer of gypsum (the remnant of the dry period) off the coast of Sicily. and a type of sedimentary rock made of marl, calcium carbonate, and clay (formed after the area was flooded).
This discovery prompted Krijgsman to return to the region in 2021 with a team of geologists from the University of Utrecht, the Royal Holloway University of London, and the University of Granada.
current fluctuations
researchers They carefully examined the sand and found that the composition and size of the grains changed every few centimeters. “We soon noticed the patterns of undulations of fossilized streams in the sand.” recalls Gijs van Dijk, one of Krijgsman’s former students at Utrecht University and lead author of the new study.
“These structures are formed when fast-flowing water brings sand with it. For example, we all know the pattern that sand leaves behind when exposed to strong winds or fast-moving water currents for long periods of time.”
The team took pictures of the structures and, From its geometry, the researchers deduced ancient flow directions and conditions that shaped the sand 5.3 million years ago.
They discovered whether the sand was washed away by rivers or local deltas, but instead formed by a river. strong undercurrent flowing from west to east in deeper waters than previously assumed.
Imprinted disasters
This new study provides another physical geological evidence of a mega-flood flowing from the west to the eastern Mediterranean.
“Today we can test and measure directly. one of the most devastating periods of environmental change to occur on our planetwhich until now we have only been able to describe it in geophysical models”, says Van Dijk.
As he explains, geologists are “trained to use contemporary processes at the Earth’s surface” to interpret what they observe in rocks. But in this case, they couldn’t trust this procedure because they didn’t know “a similar phenomenon for at least the last 100 million years.”
It is precisely these conditions of discovery that make these results “very intriguing,” Van Dijk concludes.
Reference work: https://onlinelibrary.wiley.com/doi/10.1111/sed.13074
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