Inherited rift faults as Drivers of orogenic complexity: The case of the Amora Fault System, central Southern Alps (N Italy)

Studying structural inversion phenomena is essential for reconstructing fold-and-thrust belt evolution and understanding how pre-existing structures influence their final architecture. In this study, we investigate the tectonic evolution of the Amora Fault System in the central Southern Alps, a Jurassic rift-related structure repeatedly reactivated during Alpine orogenesis. We reconstruct the multiphase history of faulting through detailed structural mapping, paleostress analyses, and microstructural analysis of fracture-filled carbonates, integrated with analogue model comparisons. The Amora Fault System initiated as a long-lived N–S-striking normal fault system during the Early–Middle Jurassic rifting, followed by renewed post-rift reactivation in the Late Jurassic-Early Cretaceous. Subsequent Alpine compression (Late Cretaceous–Eocene) led to the development of the S-verging Albino Thrust, strike-slip reactivation of Jurassic normal faults, and mid-Eocene magmatism accompanied by emplacement of E–W-trending andesitic dikes and associated faulting. Paleostress reconstructions reveal progressive changes in stress orientation, with a vertical σ1 and an E-W trending σ3 during the Jurassic, a N-S σ3 during the mid-Eocene magmatism, and a horizontal N–S-directed σ1 during Alpine compression. The evolution of the Amora Fault System highlights the interplay between structural inheritance, thermal weakening, and stress field reorientation in controlling fault reactivation, thrust segmentation, and deformation partitioning. More broadly, this study illustrates how inherited rift structures govern the architecture of orogenic belts, generating complex along-strike thrust geometries and multiphase deformation patterns. These results contribute to a better understanding of fault system evolution across rift–orogen cycles, with implications for tectonic reconstruction and seismic hazard assessment.