A view of Israel, including the Mediterranean Sea, Red Sea and Suez canal.
(photo credit: REUTERS)
The world’s oldest oceanic crust lies nearby at the bottom of the eastern Mediterranean Sea. According to research by Dr. Roi Granot of Ben-Gurion University of the Negev published on the website Nature Geoscience on Monday, the Mediterranean ocean floor may be millions of years older than previously thought.
Oceanic crust is extremely dense. That compact formation generally makes it return rather rapidly (at least in geological terms) back into Earth’s mantle at places where tectonic plates meet. As a result of this “rapid recycling,” most oceanic crust is less than 200 million years old. But Granot’s research suggests the crust of the Herodotus Basin in the eastern Mediterranean may be some 140 million years older.
Although this ancient remnant may be preserved in the Herodotus Basin, the area is covered by thick sediments, making it unclear precisely how old the crust is, or even whether it is oceanic at all.
Granot, of BGU’s department of geological and environmental sciences, used magnetic data to analyze the structure of the Herodotus Basin crust. What he found there were rocks characterized by magnetic stripes, the hallmark of oceanic crust formed at a mid-ocean ridge.
That is significant, because as hot magma below or within the Earth’s crust at such locations cool, magnetic minerals in the newly formed rocks align with the planet’s magnetic field. Over time, that change of orientation is recorded in the ocean floor, creating a unique “barcode” that provides a time stamp for crust formation, Granot said.
By identifying and analyzing skewed patterns in these magnetic stripes using this principle, he was able to show that the oceanic crust in the Herodotus Basin could be as much as 340 million years old.
The geologist suggested that the crust might be a remnant of the Tethys Ocean, which long ago preexisted the Atlantic and Indian Oceans. If correct, this implies the ocean formed much earlier than previously thought.
Granot received funding from the Science, Technology and Space Ministry and was supported by the European Union Seventh Framework Program and the Israel Science Foundation. His research also received assistance from the Eco Ocean Project.