Sardinia? “It was born from the merger of two microplates detached from the European margin”

CAGLIARI. Sardinia was “born from the fusion of two microplates, between 30 and 21 million years ago”. This is supported by researchers from the National Institute of Geophysics and Volcanology and the Roma Tre University, who analyzed the rocks of Sulcis and other localities, reconstructing the tectonic processes responsible for the origin of Sardinia and its current position in the Mediterranean Sea.

“It is known, thanks to paleomagnetic data obtained in Sardinia and Corsica since the 1970s – explains Fabio Speranza, Director of the Rome2 Section of INGV and co-author of the study – that the Sardinian-Corso tectonic block detached 21 million years ago from the European Provençal-Catalan margin, reaching its present position with a counterclockwise rotation of 50°-60°. However, with this work we have taken an important step forward: we have in fact discovered that south-western Sardinia – specifically the territory of Sulcis – has undergone a greater rotation, of about 90°, after 30 million years. Not only that: in the light of the new evidence we have re-evaluated data already present in the literature relating to much older rocks, dating back to the interval 300-150 million years ago, and we have discovered that the rotation of the southern portion of the island is even wider , equal to about 120°”.

Sardinia, therefore, would have formed from two independent microplates which in geologically recent times, between 30 and 21 million years ago, welded together and, together, detached from the European margin to be located in the central Mediterranean.

While the northern part of Sardinia was part of a single block with Corsica and Provence, the southern plate of the island belonged to the so-called Iberian plate, which decoupled from Europe between 120 and 150 million years ago, during the opening of the Gulf of Biscay, with a first anti-clockwise rotation of 30°”goes on Gaia Siravo, researcher at INGV and co-author of the study, “With a second counterclockwise rotation of 30° which occurred between 30 and 21 million years ago, southern Sardinia was welded to the rest of the Sardinian-Corso block along the so-called Nuoro fault. After that, between 21 and 15 million years ago, the entire ‘new’ Sardinian-Corsa plate definitively detached from the European margin with an anti-clockwise rotation of 60° and reached its current position”.

The results obtained from this work therefore suggest that before 30 million years ago the Iberian plate was actually much larger than it is today (in fact, we speak of Greater Iberia) since it was united not only with southern Sardinia, but also with the Balearic Islands, the Calabro-Peloritan block, the Kabili blocks (northern Algeria) and the Alboran block (which includes Morocco and Andalusia). After that, starting 30 million years ago, Greater Iberia was fragmented and the microplates produced by this fragmentation dispersed until they reached their current location.

And the researchers are already aiming for new discoveries: “Our next objectives certainly include trying to determine with greater precision the age of the oldest 30° counterclockwise rotation of southern Sardinia, which is currently included in a time interval very long, between 250 and 40 million years ago: being able to better date this event would allow us to further deepen our knowledge of the tectonics of our country”.

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