Superimposed Deformation of Sub‐Salt Rift Basins in Fold‐Thrust Belts: Insights From Analog Modeling

Abstract Rift inversion plays a significant role in accommodating shortening in fold‐thrust belts but is often obscured by post‐rift salt, complicating deformation sequences and masking underlying sub‐salt inversion structures. This study uses four scaled analog models with Particle Image Velocimetry to investigate the influence of post‐rift salt on the strain evolution and final structural geometry of sub‐salt rift inversion. Results demonstrate that post‐rift salt decouples deformation, facilitating early thin‐skinned shortening in the supra‐salt cover which precedes and delays inversion of the underlying sub‐salt rift basin. Rift inversion initiates with minor basin uplift reflecting early strain localization, potentially guiding both supra‐salt thin‐skinned thrust nucleation and the localization of subsequent sub‐salt thrusts. Subsequent deformation is accommodated primarily by new, low‐angle (12°–22°) thrusts (e.g., footwall shortcuts) cutting across rift basins, favored by the frictional lock‐up of steep (58°–81°) pre‐existing normal faults. This process generates characteristic “harpoon” geometries in both single and multiple basin inversion settings, characterized by steep normal faults truncated by low‐angle footwall shortcut thrusts and associated hanging‐wall anticlines, mirroring structures observed in the Outer Western Carpathians and Kalpin fold‐and‐thrust belts. These findings highlight the crucial role of post‐rift salt in controlling sub‐salt rift inversion kinematics and provide a framework for interpreting inversion styles in deep layers where seismic imaging is often ambiguous.