Structural analysis of the Albidona Formation in the Alessandria del Carretto-Plataci area (Calabro-Lucanian Apennines, Southern Italy)

The Albidona Formation, one of the uppermost formations of the Cilento Unit (Langhian-Early Tortonian), crops out at the border between Calabria and Lucania (Southern Apennines, Italy). In the studied area, located between the villages of Alessandria del Carretto and Plataci, the Formation lies unconformably on different basinal terrains represented by the Crete Nere, the Saraceno, and the Sicilide Units. Lithologically, the formation shows turbiditic arenaceous-pelitic facies which evolve upwards to conglomeratic-arenaceous ones. At different levels of the series, slumping, conglomeratic-arenaceous and calcareous-marly megaturbidites, as well as synsedimentary faults are found, which suggest significant synsedimentary tectonic phenomena. The thickness of the entire succession cropping out in this area is about 1200 m. This turbiditic succession represents the infilling of thrust-top or foredeep basins which developed on the frontal part of the accretionary wedge of the Apenninic Chain during its Middle-Late Miocene northeastwards migration. Detailed field mapping and structural analysis carried out on the Albidona Formation shows a polyphase deformation history with at least two main contractional deformation sequences (D1 and D2). The former is characterized by two coaxial compressive episodes (D1a and D1b) that produced the main shortening recognized in this area. The first episode (D1a) formed recumbent to moderately inclined NE-vergent folds, while the second (D1b) determined coaxial refolding of earlier structures. The latest deformation event (D2) produced NE-SW trending upright gentle folds. The superposition of folding events D1b and D2 produces a gentle dome and basin interference pattern on top of the gently dipping D1a fold limbs. Nevertheless, the main regional structure observed in the Albidona Formation consists of a moderately inclined to recumbent NEvergent macrofold running for about 10 km along the strike from the village of Plataci to Timpone della Niviera.