Miocene rotation of Sardinia: New paleomagnetic and geochronological constraints and geodynamic implications

The Miocene rotation of Sardinia (Western Mediterranean) remains poorly constrained despite a wealth of paleomagnetic data, primarily due to poor chronostratigraphic control. However, this rotation is contemporaneous with the opening of the Liguro-Provençal back-arc oceanic basin, and its history is key to understanding the kinematics of opening of the Western Mediterranean. We address this issue through paleomagnetic and 40Ar/39Ar geochronological investigations of Miocene volcanic sequences in Sardinia. Precise age control allows secular variation of the geomagnetic field to be evaluated. These data provide constraints on the rotational history of this continental microplate; Sardinia rotated 45° counterclockwise with respect to stable Europe after 20.5 Ma (Aquitanian), which is a marked increase over the estimate of 30° derived from prior paleomagnetic studies. Rotation was essentially complete by 15 Ma. About 30° of rotation occurred between 20.5 and 18 Ma (Burdigalian), corresponding to the period of maximum volcanic activity in Sardinia. The observed rotation validates palinspastic models derived from a morphological fit of basin margins, and indicates high rates of opening (up to 9 cm yr− 1 in the southern part of the basin) between 20.5 and 18 Ma.