Structural evidence for Neogene rotations in the eastern Sicilian fold and thrust belt

Abstract

A geological and structural analysis carried out on a sector of the eastern Sicilian fold and thrust belt pointed out the occurrence of two systems of structural associations, typical of collisional fronts. In particular, the Mesozoic–Serravallian succession of the Mt. Judica unit, outcropping in three W–E- to WNW–ESE-striking distinct ridges, is characterized by two fold systems with sub-perpendicular axes, the first plunging towards 010–040 at angles of 30–55°, the second one with sub-horizontal axes trending 090–115. The different angular values of plunging suggest that the folds of the first system underwent the effects of severe tectonic deformation following their formation. Moreover, the distinct ridges were uplifted by south-verging thrusts and relative back-thrusts coaxial to the second system of folds. Conversely, the Upper Tortonian–Lower Pliocene deposits of Mt. Pulicara show only one fold and thrust system, WNW–ESE-trending, roughly coaxial to the second system recognized in the Mt. Judica unit succession. The structural analysis carried out in the two areas, compared with published eastern-central Sicily palaeomagnetic data, suggest that the Mesozoic–Serravallian succession of the Mt. Judica Unit recorded both major 70° Langhian–Late Tortonian clockwise rotations and locally 30° Pliocene clockwise rotations. So, the structures formed during the first deformation stage were totally rotated up to 100°. Conversely, structures of the Mt. Pulicara Upper Tortonian–Lower Pliocene deposits were involved only in the Pliocene clockwise rotation. From a geodynamic point of view, the Neogene clockwise rotation in the eastern Sicily fold and thrust belt is related to the regional framework of the Africa–Europe convergence.