Salt Diapirs and Minibasins Along a Transect Across the Basque‐Cantabrian Pyrenees: Implications for Cover‐Basement Interaction During Rifting and Inversion

Abstract The Basque‐Cantabrian Pyrenees experienced Early Cretaceous rifting and latest Cretaceous to Cenozoic inversion, with the presence of prerift Upper Triassic Keuper salt influencing how deformation was accommodated. Considerable disagreement exists on the degree of decoupling of supra‐ and subsalt deformation, the amount of thin‐skinned translation of the cover relative to basement, and the dip polarity of the primary extensional and contractional lithospheric detachment. To address these issues, we use surface and subsurface data to evaluate six diapirs and associated minibasins along a transect across the Basque‐Cantabrian Pyrenees. Key findings include: (a) the Burgalesa Platform and the Alavesa Platform to southern limb of the Bilbao Anticlinorium are ramp‐syncline basins, with prekinematic rafts, that record Cretaceous thin‐skinned extension and translation over north‐dipping basement faults; (b) whereas Bakio and Villasana de Mena had early extensional triggers and long‐lived passive diapirism, Poza de la Sal and Salinas de Rosío began as salt anticlines, with the onset of steep passive diapirism in the late Albian and Cenozoic, respectively; (c) although Sopelana and Montorio were squeezed shut to form vertical welds, Villasana de Mena was not noticeably shortened; (d) the salt layer was still continuous after extension ceased; (e) the salt served as a ramp‐flat thrust fault during inversion; and (f) although the initiation and evolution of diapirs were influenced by basement faults, they are not located over those faults today. The deformation to the south of the Bilbao Anticlinorium was thus decoupled above and below a major north‐dipping salt décollement during both extension and contraction.