Origin, recurrent reactivations, and tectonic role of transverse zones in thrust‐and‐fold belts. The Central Southern Alps (Italy)

Transverse zones (TZs) in fold-and-thrust belts typically comprise strike-slip to transpressional faults and related folds, oriented sub-parallel to the regional shortening direction. These zones are typically associated with inherited faults or lateral stratigraphic changes, which promote strain partitioning, stress rotation, and kinematic decoupling between adjacent blocks. In the Central Southern Alps (CSA), transverse zones sub-parallel to the N–S shortening direction originated as pre-orogenic rift-related faults, later reactivated during the Alpine orogeny under compressional regimes. Their structural complexity has long been recognized, but no systematic absolute dating has constrained their long-term evolution and reactivation history. To address this gap, we combine geological mapping, multi-scale structural analysis, and U–Pb geochronology on syn-tectonic carbonates from TZs and major thrust faults in the Lecco area to reconstruct their structural evolution within the Alpine thrust system. We infer a pre-orogenic origin for N–S TZs and some E–W striking faults linked to rift-related extensional tectonics active during the Late Norian and Early–Middle Jurassic times. U–Pb ages provide new insights into the Early Cretaceous-Miocene syn-orogenic evolution of the Central Southern Alps. During this interval, rift-inherited N–S faults were episodically reactivated in strike-slip mode under N–S shortening for nearly 100 Ma. We discuss how the TZs influence the build-up of the belt, promoting along-strike strain partitioning, acting as lateral connectors of thrusts and contributing to shortening accommodation when oblique to the maximum horizontal compression.