The oldest ocean surface in the world is in the Mediterranean, between Cyprus, Crete and Egypt, and can be around 340 million years, according to a recent work published in the journal Nature Geoscience.
The ocean surface is constantly renewed, forming dorsal and disappearing in subduction zones. This achieves a maximum of 200 million years. The exception was found in the Mediterranean basin of Herodotus. Geo-magnetic data have been analyzed to calculate the age of its surface. When the magma originating in the new surface is extracted and cooled in the ocean dorsal, the minerals are oriented according to the Earth's magnetic field. And as the direction of the magnetic field changes over time, there is a time map at the bottom of the oceans. With the reading of this map it is estimated that the surface of the Herodotus Basin can be between 315-365 years. Researchers have suggested that this piece of surface could be part of the Tetis Sea of the time of the Pangea supercontinent.