Pattern of orogenic rotations in central–eastern 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 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.

Evolution of the southern Tyrrhenian slab tear and active tectonics along the western edge of the Tyrrhenian subducted slab

“…These results support the saloon-door opening of the Tyrrhenian basin, when compared to the coeval counter clockwise rotation of the Southern Apennines (Gattacceca & Speranza 2002). Palaeomagnetic data also show that CW rotations in Sicily increase from west to east (Speranza et al 2003). These data can be tied to the evolution of the Adventure thrust front/foredeep system that is present in the western part of the Strait of Sicily Argnani1993).…”

“…In fact, palaeomagnetic data from Sicily indicate that large CW rotation affected the Mesozoic to Pliocene sediments stacked within the fold-and-thrust belt (Channell et al 1990;Speranza et al 1999Speranza et al , 2003. A CW rotation of about 708 occurred between Langhian and Late Tortonian, whereas 308 CW rotation affected the thrust-and-fold belt between Messinian and early Pleistocene.…”

Geomorphological evolution of western Sicily, Italy

“…The tectonic evolution of the western Sicily belt was a progressive accretion of thrust sheets (Catalano et al 2000) and duplex formation (Catalano et al 1996), combined with the clockwise rotation of the allochthonous blocks (Oldow et al 1990;Speranza et al 2003).…”

Mountain building in NW Sicily from the superimposition of subsequent thrusting and folding events during Neogene: structural setting and tectonic evolution of the Kumeta and Pizzuta ridges

“…The resulting tectonic structures are not coaxials and their present-day setting can be explained by the occurrence of progressive, vertical-axis clockwise rotations during their emplacement (Oldow, Channell, Catalano, & D'Argenio, 1990;Speranza, Maniscalco, & Grasso, 2003). The rotation amount decreases stepwise from internal to external tectonic units and the high value of rotation measured in the internal tectonic unit (e.g.…”