Plio-Pleistocene tectonic evolution of the western margin of the S. Arcangelo basin (Southern Apennines)

The S. Arcangelo basin is located on the easternmost reaches of the Lucania Apennines. This basin, filled by Plio-Pleistocene elastic deposits, is interpreted as a piggy-back belonging to a series of Plio-Quaternary thrust-top basins which formed on the eastern portions of the thrust belt during the latest stages of the orogenic accretion. A detailed analysis of the geometry and structural features of the western margin of the S. Arcangelo basin, as part of a widerscale investigation involving the whole basin and its corresponding orogenic front, reveals a clear interaction between tectonics and deposition. Deposits of middle-late Pliocene age, exposed along the western margin of the basin (Caliandro unit), are presently tilted to the NE with an average dip of 50°. Variations in the geometry of successive lithostratigraphic intervals of this unit, point to a major progressive angular unconformity that reflects the uplift and tilting of the basin's margin. The uplift of this region, constrained in time by the age of the Caliandro unit, is the surface effect of the creation of a buried thrust belt in the Apulian carbonate units. A coeval foreland migration of the frontal allochthonous thrust sheets is documented by well data and indicates that the Apulian units have recorded from Late Pliocene a WSW-ENE shortening in the order of 20-25 km.