Vertical-axis rotations in the Sicilian fold and thrust belt: new structural constraints from the Madonie Mts. (Sicily, Italy)

A detailed geological and structural analysis was carried out in the Madonie Mts., along the central-northern sector of the Sicilian-Maghrebian Chain, in order to define the tectonic evolution of the area in relation to the rotation episodes occurred since the Middle Miocene. Upper Triassic-Middle Miocene successions are characterized by two fold systems with sub-perpendicular axes, the first one trending between NNW-SSE and SSW-NNE, characterized by 15-55 degrees angle of plunging, the second one trending between WSW-ENE and WNW-ESE, characterized by sub-horizontal axes. The second system of folds is coaxial to major south-verging breaching thrust of the Madonie Mts. over the Upper Miocene-Lower Pliocene thrust-top deposits. Conversely, these latter show only one fold and thrust system, roughly coaxial to the second system recognized in the Upper Triassic-Middle Miocene successions. The structural analysis, compared with published paleomagnetic data, revealed that the Neogene thrusting was accompanied by vertical-axis clockwise rotations. In particular, Upper Triassic-Middle Miocene successions recorded both major 70 degrees Langhian to Tortonian regional rotations and locally similar to 30 degrees Pliocene rotations related to activity of strike-slip fault zone. So, the structures formed during the first deformation stage were totally rotated up to similar to 100 degrees. Conversely, structures of the Upper Miocene-Lower Pliocene deposits were involved only in the Pliocene clockwise rotations, these latter related to activity of strike-slip faulting.