Coalescence of fault-bend and fault-propagation folding in curved thrust systems: an insight from the Central Apennines, Italy

The coalescence and spatial variability of different thrust-related folding mechanisms involving the same mechanical multilayer along a curved thrust system are documented in this study. The field-based analysis of thrust-related folds spectacularly exposed in the Gran Sasso thrust system, Central Apennines of Italy, allowed us to reconstruct the interference fold pattern between fault-bend and fault-propagation folding. These two thrust-related folding mechanisms exhibit spatial variability along the differently oriented ramps of the curved Gran Sasso thrust system, passing from one style to the other. Their selective development is controlled by contrasting styles of compressional normal-fault reactivation related to positive tectonic inversion. Fault-bend and fault-propagation folding interact with a characteristic interference fold pattern in the salient apex zone of the curved thrust system due to their synchronous/in-sequence growth. This interference fold pattern might be helpful and predictive when reconstructing lateral variations in different thrust-related folds in similar subaerial or submarine thrust belts.