Role of inheritance during tectonic inversion of a rift system inbasement-involved to salt-decoupled transition: analogue modelling andapplication to the Pyrenean-Biscay system

The reactivation of former rift systems and passivemargins during tectonic inversion and their incorporation intofold-and-thrust belts result in significant structural differences not onlybetween internal and external domains, but also along-strike. TheBasque-Cantabrian and Asturian systems are among the best examples toaddress the role of along-strike changes in rift inheritance since they showa transition from salt to basement-inherited structures divided by atransition zone separating thick- from thin-skinned structural domains. Whileboth domains have been widely described in the literature, the transfersystem separating the two has not been sufficiently investigated due to poorseismic imaging and the lack of large-scale outcrops. This contribution aimsto address the linkage between basement-controlled (i.e. thick-skinned) andsalt-decoupled (i.e. thin-skinned) domains and to describe how deformationis accommodated in the transitional zone between these domains. Anexperimental programme based on analogue models has been designed that wasinspired by the transition from the thin-skinned Basque-CantabrianPyrenees to the east to the thick-skinned Asturian Massif to the west. Asobserved in nature, experimental results show that oblique structures (atlow angle with the shortening direction) form in the transitional domain,and their location depends on the linkage of the active structures occurringin both surrounding thick- and thin-skinned domains at different positions.Nevertheless, their orientation and evolution are controlled by theunderlying decoupling horizon (i.e. salt). The deformation in thethick-skinned domain produces significant topography over a narrowdeformation area due to the lack of effective decoupling levels. On thecontrary, deformation in the thin-skinned domain is more distributed due todecoupling, resulting in a wider deformation area of less topography. As aresult, syn-contractional sedimentation occurs mainly in the forelandbasin in front of the thick-skinned domain, whereas it is observed in theforeland but also in piggyback basins in the thin-skinned domain.

Automated summary

The reactivation of former rift systems and passive margins during tectonic inversion leads to structural differences between internal and external domains, as well as along-strike variations. The Basque-Cantabrian and Asturian systems demonstrate a transition from salt to basement-inherited structures, with a transitional zone separating thick- and thin-skinned domains. This study aims to investigate the connection between these domains and describe deformation in the transitional zone using analogue models.