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The Pyrenean domain records the development of a hyperextended system during the Early Cretaceous at Iberia/Eurasia plate-boundary. This rifting stage is controlled by the coeval development of N120° longitudinal and N20° transverse tectonic features. In the west-Pyrenean Mauléon basin, preserved in the heart of a N120° lithospheric pop-up, the Iholdy, Saison and Barlanès transverse structures are known to play a significant role during the Cretaceous hyperextension. Using a multidisciplinary approach combining Raman thermometry, paleostress reconstructions, seismic interpretations, 3D implicit geological modeling and passive seismic interpretation, we define these three N20° structures as syn-collisional transfer zones rooting at depth in the upper lithospheric mantle. These tectonic features significantly control the 3D structural architecture of the Mauléon basin pop-up. Indeed, the N120°-oriented thrust systems, defining the edges of the Mauléon basin pop-up, branch into these transfer zones and define corridors with differing amounts of shortening. This overall structural pattern defines drawer-like structures allowing the closure, by stages, of the former rift domain. Thus, this study clarifies the role of inherited lithospheric transfer zones in the reactivation of a hyperextended rift basin and bears upon the origin of the non-cylindrical shape of the West-Pyrenean belt. • Role of transfer zones during hyperextended rift inversion. • Drawer-like structures allowing the closure, by stages, of the former rift domain. • The non-cylindrical shape of the Pyrenean orogen driven by inherited segmentation. [ABSTRACT FROM AUTHOR]

The aim of this study is to unravel the tectono-sedimentary evolution of a hyper-thinned rift, based on the example of the Mauléon Basin, a basin filled by thick synrift deposits. The integrated study combines field data, detailed geological mapping and seismic interpretation. The field study focuses on the Iberian margin of the Mauléon Basin. Seismic interpretation and well calibration along a N S transect of the Mauléon Basin enable imaging the transition with the northern conjugate margin. The synrift records are very different on either side of the basin: the southern margin is composed of a proximal turbiditic s.l. siliciclastic system, whereas the northern margin is characterized by a carbonate system extending from the platform to the basin. We recognize the Mauléon rift as an apparent symmetric hyper-thinned rift, related to a southward dipping Albian detachment and a northward dipping Cenomanian one. Two stages of continental crustal thinning are inferred to explain the development of the Mauléon Basin. First, a Barremian to earliest Albian "ductile pure-shear thinning phase", responsible for the lower crustal thinning and the formation of a symmetric sag basin. Second, an Albian-Cenomanian simple-shear thinning phase, responsible for the onset of the southward dipping Saint-Palais detachment faulting and for evolution to an asymmetric basin. The Iberian margin appears as an upper plate and the European one as a lower plate during Albian time. At Early Cenomanian time, the basin was affected by structural changes of the margins resulting from shift in detachment direction, interpreted as "flip-flop detachment tectonics". • The Early Cretaceous Mauléon rift basin evolves from a symmetric sag basin to an asymmetric basin. • Basin asymmetry is recorded by different depositional profiles along the rift conjugate margins. • The symmetric sag basin is linked to lower crustal thinning without any brittle deformation of the upper crust. • The basin asymmetry and the hyper-thinned continental crust result from double verging detachment system. [ABSTRACT FROM AUTHOR]