New palaeomagnetic data from upper Triassic to Pliocene sediments reveal that in eastern Sicily a major 70° clockwise (CW) rotation took place between Oligocene and late Tortonian time, followed by a further 30° CW rotation. Results from central Sicily are less coherent. They show 44-83° post-Oligocene CW rotation, local 14° post-late Tortonian counterclockwise (CCW) rotation, and 25° 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. 100° 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 70° 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 20° Ma-1, we infer that CW rotation started in Sicily in Langhian-Serravallian times, between 15-16 and 11-12 Ma ago. The 100° CW rotation observed in pre-orogenic strata from the whole of Sicily is mirrored by 80° orogen-scale CCW rotations characterizing the internal southern Apennines. Palaeomagnetism therefore shows that during orogenesis, the southern Apennines and the Sicilian Maghrebides rotated in a 'saloon-door' fashion, synchronous to back-arc spreading of the southern Tyrrhenian Sea. Consequently, our palaeomagnetic data suggest that the southern Tyrrhenian back-arc basin started to spread during Langhian-Serravallian times (from 15-16 to 11-12 Ma), significantly earlier than the late Tortonian age (8 Ma) suggested so far by oceanic drilling data.
|Titolo:||Pattern of orogenic rotations in central-eastern Sicily: implications for the timing of spreading in the Tyrrhenian Sea|
|Data di pubblicazione:||2003|
|Appare nelle tipologie:||1.1 Articolo in rivista|