Understanding the structural setting in the Southern Apennines (Italy): insight from Gravity Gradient Tensor

Abstract

The Lucania Apennines form the frontal part of the Apennines in Southern Italy. This orogenic belt was formed in response to late Miocene–Early Pleistocene shortening and allochthon emplacement toward the northeast, and was subsequently affected by extensional faulting which migrated to northeast ahead of the thrust system. As a result, contraction structures are found associated to Pliocene–Early Pleistocene thrust-top basins in the NE part of the area, whereas extensional faults shape Middle Pleistocene–Holocene basin on the SW sector. The main structural grain of the belt is NW–SE, but E–W structures are widespread in the area as a result of phases of non-coaxial thrusting and strike-slip faulting. The analysis, one by one, of the components of the Gravity Gradient Tensor (GGT) has proved to yield a fine image of the structural setting of the investigated area. GGT is a second rank tensor containing the second spatial derivatives of the gravity potential and in this paper is used instead than the more traditional gravity data. The Tzz component allows an accurate description of the location and of the shape of basins and other structures, but different components of the GGT provide even more detailed insights for such structures. In particular, we found that the Tzy and Tyy locate well those structures trending closer to the E–W direction for both thrust-top and extensional basins, and their termination against the main NW–SE structures. The combined use of components of GGT provides a finer definition of the anomaly sources particularly if a good knowledge of their strike and depth is independently estimated with other geological and geophysical investigations.