New geological research has identified evidence that the seabed south of Formentera preserves part of a much older geological structure dating back to the Mesozoic Era, when dinosaurs lived on Earth.

The study, published online in September 2026 in the journal Marine Geoscience and Energy Resources, examines the Formentera Basin and concludes that it represents a remnant of the ancient passive margin of the Ligurian-Maghrebian Tethys, an oceanic domain that existed during the Mesozoic.

The findings provide new information about how the western Mediterranean developed and how the geological structure beneath the Balearic Islands evolved over hundreds of millions of years.

Evidence Beneath the Sea

The research focuses on the Formentera Basin, an offshore depression located between the southern Formentera platform and the Émile Baudot Escarpment.

The basin lies at intermediate depths of approximately 1,500 to 1,800 metres and forms part of the wider Balearic Promontory, the geological structure that includes Ibiza, Formentera, Mallorca and Menorca.

Researchers used offshore seismic data to investigate geological structures beneath the seabed.

Their analysis identified faults and other structures within Mesozoic rock sequences, allowing the researchers to reconstruct part of the region's ancient geological history.

A Geological Structure From the Mesozoic

The study interprets the Formentera Basin as a Mesozoic half-graben system.

A half-graben is a type of geological basin formed as the Earth's crust stretches and faults develop. In this case, the researchers identified structures associated with extension of the continental crust, including normal faults, salt-related structures and folds.

The authors conclude that the Formentera Basin and the southern Formentera margin are not primarily structures created during the much more recent Neogene period.

Instead, they interpret them as remnants of a Mesozoic geological system that extended towards the deeper oceanic domain.

The Ancient Tethys Ocean

The geological history described in the research is linked to the Ligurian-Maghrebian Tethys.

This ancient oceanic domain formed part of the complex system of seas and continental margins that existed during the Mesozoic, long before the Mediterranean reached its present configuration.

The researchers interpret the structures beneath the Formentera Basin as part of the northwestern passive margin of this ancient ocean.

A passive margin is a continental edge that forms where continental crust transitions towards oceanic crust without being an active plate boundary dominated by major earthquakes or volcanism.

Much Older Than the Modern Mediterranean

The discovery does not mean that today's Mediterranean Sea existed in its current form during the age of the dinosaurs.

Instead, it provides evidence of an older geological architecture from which parts of the present western Mediterranean region later evolved.

The study explains that the Balearic Promontory consists of thinned continental crust and occupies a position between the Valencia and Algerian basins. Its geological history has been affected by several phases of extension, compression and later deformation.

The structures identified in the Formentera Basin therefore preserve evidence of geological processes that predate the formation of the modern western Mediterranean basins.

What the Research Reveals About Formentera

The study's findings add another layer to the geological history of Formentera.

The island itself is largely made up of much younger exposed rocks. Official Balearic geological information identifies the oldest materials exposed on Formentera as Upper Miocene, approximately 11 to 7 million years old, including extensive fossil coral reefs around La Mola.

That distinction is important.

The new research is primarily about the much older geological structures preserved offshore and beneath the seabed, rather than exposed rocks on the island dating directly from the dinosaur era.

Four Researchers Behind the Study

The research was carried out by Fadl Raad, Agnès Maillard, Eduard Roca and Johanna Lofi.

The researchers are affiliated with institutions including the University of Montpellier and CNRS, Université de Toulouse and the Universitat de Barcelona.

The paper, titled "The Formentera Basin (Balearic Promontory - Western Mediterranean): A Remnant of the Mesozoic Tethyan Passive Margin", was published online on September 16, 2026.

A Window Into the Ancient Mediterranean

The researchers say the results help refine understanding of the tectonic and geological evolution of the Balearic Promontory and the western Mediterranean.

For Formentera, the significance lies largely beneath the surrounding waters. Seismic evidence has allowed scientists to identify geological structures inherited from a period when the region was part of a very different continental and oceanic setting.

The island may therefore look familiar today, but the rocks and structures beneath its surrounding seabed preserve evidence of a geological landscape that existed hundreds of millions of years before Formentera took its present form.