A new gravity survey (almost 900 new sites and more than 4000 sites from previous studies) reveals the existence of Pyrenean-oriented long-wavelength residual gravity anomalies ranging from −18 to 28 mGal, associated with frontal structures, and short-wavelength gravity lows (up to −16 mGal) distributed along an oblique zone in the western sector of the South Pyrenean Central Unit of the Spanish Pyrenees. These clearly correlate with the occurrence of several bodies and diapirs of Triassic evaporites and mudstones. The subsurface geometry and regional location of these evaporitic bodies is derived from four 2.5D gravity models that tie data from field geology, rock density analysis, seismic reflection profiles, boreholes and our gravity survey. Gravity-constrained cross-sections allow us to distinguish between vertically well-developed and poorly developed diapirs that belong to the Sierras Marginales Unit, and to characterize the relationships between thrusting and diapirism during Eocene–Oligocene time.

We present a series of 2D thermo-mechanical numerical experiments of thick-skinned crustal extension including a pre-rift salt horizon and subsequent thin-, thick-skinned, or mixed styles of convergence accompanied by surface processes. Extension localization along steep basement faults produces half-graben structures and leads to variations in the original distribution of pre-rift salt. Thick-skinned extension rate and salt rheology control hanging wall accommodation space as well as the locus and timing of minibasin grounding. Upon shortening, extension-related basement steps hinder forward propagation of evolving shallow thrust systems; conversely, if full basin inversion takes place along every individual fault, the regional salt layer is placed back to its pre-extensional configuration, constituting a regionally continuous décollement. Continued shortening and basement involvement deform the shallow fold-thrust structures and locally breaches the shallow décollement. We aim at obtaining a series of structural, stratigraphic and kinematic templates of fold-and-thrust belts involving rift basins with an intervening pre-rift salt horizon. Numerical results are compared to natural cases of salt-related inversion tectonics to better understand their structural evolution.

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