Neogene Foreland Tectonics in the Southern Apennines

F. Roure, P. Casero, I. Moretti, C. Muller, L. Sage, R. Vially

Combined structural and biostratigraphic analyses and seismic interpretation help us to balance cross sections through the southern Apennines from the Adriatic to the Tyrrhenian Sea and to propose an overall model for the evolution of the belt. Three lithostratigraphic units have been distinguished according to their Mesozoic facies and style of deformation: the western platform (upper unit), the Lagonegro-Molise basin, and the eastern platform. Foreland deformation migrated from west to east, and external domains were reached progressively by synorogenic flysch deposits (foredeep) and later incorporated into the thrust sheets. Presently, only the most external part of the eastern platform is still unaffected by thrusting, while internal parts are building the overthrust elt at depth, which is masked on the surface by allochthonous basinal nappes. The evolutive geometry of thrust and piggy-back basins results from the continuous understacking of new material at the bottom of the tectonic prism. The deeper basement is also progressively involved in the deformation, giving rise to large nappe anticlines.

Despite the early subsidence and deformation of the western platform and basinal domains in Langhian to Tortonian time, all the deformation of the eastern platform has occurred since Messinian time. These compressive structures are thus contemporaneous with the opening of the Tyrrhenian Sea. To the west, the upper tectonic units of the Apennines are indeed affected by listric normal faulting, with previous thrust planes having been locally reactivated during the distension.

Post-Messinian shortening in the sedimentary cover is accompanied by a crustal thickening outlined by the Moho's geometry. We interpret it as a result of the subduction of the Apulian continental lithosphere. Recent uplift of the Apennines is indeed directly related to this crustal root.

AAPG Search and Discovery Article #91032©1988 Mediterranean Basins Conference and Exhibition, Nice, France, 25-28 September 1988.