Nature, Origin, and Evolution of the Pyrenean‐Cantabrian Junction

Abstract

AbstractWe investigate the present‐day orogenic architecture of the Pyrenean‐Cantabrian junction corresponding to a boundary between inverted rift segments using seismic interpretation, field data, and borehole information. This junction was formerly attributed to a major NNE‐SSW striking Pamplona transfer fault segmenting the Basque‐Cantabrian and Mauléon basins during both rifting and convergence. Our study shows that the orogenic architecture results from a strong decoupling between the thick‐skinned (basement‐involved) and the thin‐skinned (detached in the Upper Triassic evaporites) modes of deformation. The evaporites decoupling horizon was responsible for the transport and allochthony of the former rift basins over large distances on top of the Basque massifs and the Ebro and Aquitaine foreland basins. A crustal‐scale cross‐section depicts the allochthony of the Basque massifs forming a crustal wedge over the crusts of Iberian, Ebro, and Eurasian affinity. Three‐dimensional analysis of the present‐day architecture suggests that two phases of rifting and related basins can be recognized: the Late Jurassic‐Barremian and the Aptian‐Cenomanian basins. Furthermore, we show that during the Aptian‐Cenomanian, the Mauléon and Basque‐Cantabrian rift segments spatially overlapped north and south of the Basque massifs and were controlled by WNW‐ESE striking extensional faults. These results discard the existence of a major Pamplona transfer fault and argue for NNE‐SSW direction of extension during the mid‐Cretaceous. This study emphasizes the role of inheritance during rifting and reactivation and provides a new syn‐rift template, which controlled the Alpine reactivation. Finally, these results have major implications for the Iberia‐Eurasia plate boundary and the kinematics of the North Pyrenean basins.