Pattern of orogenic rotations in centraleastern Sicily: Implications for the timing of spreading in the Tyrrhenian Sea

Abstract: New palaeomagnetic data from upper Triassic to Pliocene sediments reveal that in eastern Sicily a major 708 clockwise (CW) rotation took place between Oligocene and late Tortonian time, followed by a further 308 CW rotation. Results from central Sicily are less coherent. They show 44–838 post-Oligocene CW rotation, local 148 post-late Tortonian counterclockwise (CCW) rotation, and 258 post-mid-Pliocene CW rotation. We interpret the larger CW rotation observed in eastern Sicily as related to a more internal palaeogeographical position with respect to central Sicily. Our results complement pre-existing data from the northwestern Sicily carbonates, and indicate that all the internal carbonate nappes coherently rotated by c. 1008 CW during tectonic emplacement, implying a west-to-east increase of shortening in the Sicilian Maghrebian belt. In Sicily, compressive deformation started during the Langhian, i.e. just after the deposition of the upper Oligocene–upper Burdigalian Numidian Flysch turbidites. Therefore the age of the older 708 palaeomagnetic rotation (synchronous to the thrusting) is constrained to occur between the Langhian and late Tortonian. Furthermore, by considering a maximum possible rotation rate of 208 Ma1, we infer that CW rotation started in Sicily in Langhian–Serravallian times, between 15–16 and 11–12 Ma ago. The 1008 CW rotation observed in pre-orogenic strata from the whole of Sicily is mirrored by 808 orogen-scale CCW rotations characterizing the internal southern Apennines. Palaeomagnetism therefore shows that durin