Push-up inversion structures v. fault-bend reactivation anticlines along oblique thrust ramps: examples from the Apennines fold-and-thrust belt (Italy)

Abstract

The study of inversion structures in fold-and-thrust belts that originated as extensional faults is valuable for the development of geometric and kinematic models that are helpful in unravelling the structural style and for detecting structural hydrocarbon traps. We document push-up inversion structures versus fault-bend reactivation anticlines occurring along oblique thrust ramps, by examining examples of buried Apulian structures in the Central–Southern Apennines and outcropping thrust-related folds in the Central–Northern Apennines of Italy. The different geometric features between push-up inversion structures and fault-bend reactivation anticlines are functionally controlled by the mechanical characteristics of the involved sedimentary multilayer, the original architecture of the former extensional basin, and the amount of thrust displacement. The recognition of such inversion structures is important in understanding the anatomy and structural style of foreland fold-and-thrust belts. In addition, their identification is critical in interpreting the geometry and types of structural traps that may be expected along oblique thrust ramps. This study reveals that push-up inversion structures and fault-bend reactivation anticlines could coexist along oblique thrust ramps within a curved thrust system and may be detected among analogous foreland thrust belts that include inherited extensional basins.