Paleomagnetic Evidence for Pre-21 Ma Independent Drift of South Sardinia From North Sardinia-Corsica: “Greater Iberia” Versus Europe

Abstract

It is unanimously acknowledged that the Corsica-Sardinia microplate rotated counterclockwise (CCW) by 40–50° between 21 and 15 Ma, synchronous with Liguro-Provençal Basin oceanic spreading. Conversely, 60–120° CCW rotations with respect to Europe from Sardinia (Permian dykes, volcanics and sediments, Mesozoic carbonates, and lower Eocene limestones) have been interpreted to be related to (a) late Permian intra-Pangea shear events, (b) Aptian Iberia rotation, and (c) Eocene Valais Ocean closure. We report paleomagnetic data from 31 red-bed sites from the mid-late Eocene (45–32 Ma) Cixerri Fm. exposed in SW Sardinia. Characteristic paleomagnetic directions from 25 dual polarity sites (240 samples) define an 86 ± 7° CCW rotation. We suggest that a S Sardinia block located NE of Balearic Islands rotated 30° CCW during the 30–21 Ma Liguro-Provençal rifting, and was decoupled from N Sardinia along the left-lateral Nuoro fault. After 21 Ma, Corsica-Sardinia underwent a drift-related 60° CCW rotation as a whole. A re-analysis of available paleomagnetic results shows that Permian data from N Sardinia-Corsica align with European directions considering a 60° CCW rotation, whereas Permian and mid Jurassic data from S Sardinia match European directions only after considering a ∼35° CCW Iberia rotation besides the 90° post-Eocene event. We suggest that S Sardinia was part of Iberia, and rotated CCW during both Aptian Iberia drift and Oligo-Miocene Liguro-Provençal opening. Our data, along with recent paleomagnetic results from Calabria, suggest that S Sardinia, Balearic Islands, Calabria, Peloritan, Kabylies, and Alboran were fragments of “Greater Iberia,” joined to Iberia before 30 Ma Liguro-Provençal rifting.