A new paleomagnetic study conducted by researchers at the INGV in collaboration with the University of Sassari provides new evidence on the geological evolution of the Sardinian-Corsican microplate.
New data obtained from sedimentary successions of the Upper Paleozoic and Mesozoic outcropping in the Nurra (region of north-western Sardinia) have highlighted that the Sardinian-Corsican microplate underwent a total rotation of 90° counterclockwise between 30 and 15 million years ago, concurrently with the opening of the Liguro-Provençal Ocean. This rotation affected only Sardinia and southern Corsica: central-northern Corsica, in fact, appears to have undergone a counterclockwise rotation of only 30°. This is what emerges from the study. “Post‐Eocene 90◦ CCW Rotation of Sardinia‐South Corsica: Paleomagnetic Evidence From Permian‐Cretaceous Sediments of Nurra (NW Sardinia)”, recently published in the scientific journal 'Tectonics' of AGU by a team of researchers from theIstituto Nazionale di Geofisica e Vulcanologia (INGV) and University of Sassari.
Previously collected data confined the rotation of the Sardinian-Corsican block to the interval between 21 and 15 million years ago, up to a maximum of 50-60°.
“The new data we analyzed show no evidence of the rotation of the Iberian Plate synchronous with the opening of the Bay of Biscay (which occurred between 150 and 120 million years ago): they therefore demonstrate that before 30 million years ago the Sardinian-Corsican block - except for southern Sardinia, about which there are uncertainties - was joined to Provence and not to Catalonia as previously hypothesized.”, explains Gaia Siravo, researcher at INGV and first author of the article. “Furthermore, what our work highlights implies that if today Sardinia and Corsica are aligned in a North-South direction, 30 million years ago they were, instead, aligned in an East-West direction.”.
Another important result from the study concerns the rotation processes of Nurra and northern Sardinia during the Permian, the geological period that ends the Paleozoic Era, between approximately 300 and 250 million years ago. During that period, Sardinia was part of the supercontinent Pangea, which was thought to have been fairly stable between 300 and 200 million years ago, when its fragmentation triggered the formation of the Atlantic Ocean and the continents as we know them today.
Conversely, researchers have identified a 30° clockwise rotation process that occurred between 290 and 270 million years ago, demonstrating that Pangea—or some of its segments—was characterized by intense tectonic activity. The nature of this process is debated in the literature, but the new data suggest a rotation of the Sardinian-Corsican microplates at the edges of Pangea, likely due to the subduction of the Paleo-Tethys Ocean.
Our results provide a significant update on the rotation history of the Sardinian-Corsican microplate. Originally hypothesized over 50 years ago as a single plate with a total rotation of approximately 30°, subsequent studies—dating back about two decades—had increased this value to 60°. Our work shows that this value should be further increased to 90° and that the architecture of the Sardinian-Corsican plate, as well as its rotational history, are more complex than previously assumed., he specifies Fabio Speranza, Research Director at INGV and co-author of the article.
The recently published work clearly highlights the relevance of paleomagnetic studies for the production of paleogeographic models and indicates how the progressive production of new data provides significant improvements in the understanding of the geological processes that led to the complex evolution of the Earth's plates and microplates.
The work was published as part of the ROSE infrastructure project (SAKURA research line) funded by the Ministry of University and Research (MUR).
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Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Figure 1: a. Geographic map and main tectonic features of the central-western Mediterranean where the current NS alignment of Sardinia-Corsica can be observed. The black box indicates the location of Nurra (NW Sardinia), the study area of this research. b) Paleogeographic model proposed at approximately 30 million years ago, where Sardinia and central-southern Corsica were aligned in an EW direction before undergoing a 90° counterclockwise rotation between 30 and 15 million years ago.
Figure 2: INGV researchers during fieldwork. Note the small portable drill used to sample the rock units in the foreground. The researchers are located at the boundary between the Paleozoic and Mesozoic eras. The lower rock formation (Cala del Vino Formation) dates to the Early-Middle Permian (ca. 270 million years old), while the upper formation (Porticciolo Conglomerate) dates to the Early Triassic (ca. 250 million years old).