Rift inheritance controls ramp-dominated thrusting and Quaternary normal-fault geometry in the Umbria–Marche Apennines (Italy

Continental collision commonly overprints rifted continental margins, such that inherited extensional architecture and mechanical stratigraphy exert first-order controls on strain partitioning during shortening and on the structural pathways exploited during subsequent extension. The Umbria–Marche sector of the Northern Apennines constitutes a well-constrained natural laboratory for addressing these issues, as Neogene shortening of the Adria passive-margin multilayer produced a fold-and-thrust belt that was later dissected by Quaternary normal faulting.

We integrate field structural constraints with regional seismic interpretation tied to boreholes, balanced and restored cross-sections, gravity modelling, and 3D structural modelling. We further quantify fault-system kinematics using along-strike length–displacement profiles and displacement–length scaling derived from the 3D framework. This integrated workflow constrains shortening partitioning between the sedimentary cover and the upper crust and assesses the extent to which inherited rift structures and stratigraphic thickness variations governed thrust segmentation and the subsequent extensional overprint.

Our reconstruction indicates a ramp-dominated contractional style. Shortening was mainly accommodated on moderately dipping thrust ramps that cut through the sedimentary succession and link downwards into the upper crust, without requiring large displacements along a laterally continuous basal décollement within – or at the base of – the sedimentary cover. Thrust-related folding and progressive ramp linkage generated pronounced along-strike segmentation, while shortening was distributed between thrust slip, associated folding, and subsidiary distributed deformation. Along-strike variability is systematic and reflects the interaction between inherited Mesozoic extensional discontinuities and lateral stratigraphic heterogeneity, which preconditioned ramp nucleation, guided linkage pathways, and modulated cover–basement coupling during Neogene shortening. This framework reconciles surface structures with deep crustal architecture independently supported by gravity constraints and is consistent with progressive cover–upper crust coupling and strain localisation within a mechanically heterogeneous carbonate–siliciclastic multilayer.

Quaternary extension is expressed by segmented, high-angle normal fault systems that dissect the pre-existing thrust stack and penetrate the upper crust. Their 3D geometry and segmentation indicate that extension is superposed on – but does not represent a kinematic reversal of – contractional structures. Cross-cutting relationships document limited systematic reactivation of thrust faults under extension, whereas extensional structures are primarily guided by inherited crustal anisotropies and mechanical layering.

Overall, the Umbria–Marche Apennines show how rift-related inheritance promotes ramp-dominated thrusting and segmented fold-and-thrust belt development, while also conditioning the localisation and segmentation of late-orogenic normal faults within a mechanically layered, anisotropic crustal architecture.