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We document the role of sedimentary burial and salt tectonics in controlling the deformation style of continental crust during hyperextension. The Iberian-European boundary records a complex history of Cretaceous continental extension, which has led to the development of so-called smooth-slope type basins. Based on the review of the available geological constraints (crustal-balanced cross-sections, sedimentary profile evolution, RSCM thermometer, low-temperature thermochronology) and geophysical data (Bouguer anomaly, Moho depth, seismic reflection profiles and Vp/Vs velocity models) on the Tartas, Arzacq, Cameros, Parentis, Columbrets, Mauléon, Basque-Cantabrian and Internal Metamorphic Zone basins, we shed light on the main characteristics of this type of basin. This synthesis indicates that crustal thinning was influenced by two decoupling horizons: the middle crust and Triassic prerift salt, initially located between the basement and prerift sedimentary cover. These two horizons remained active throughout basin formation and were responsible for depth-dependent thinning of the crust and syn-rift salt tectonics. We therefore identify several successive deformation phases involving (a) pure shear dominated thinning, (b) simple shear dominated thinning and (c) continental breakup. In the first phase, distributed deformation resulted in the development of a symmetric basin. Field observations indicate that the middle and lower crust were under dominantly ductile conditions at this stage. In the second phase, deformation was localised along a crustal detachment rooted between the crust and the mantle and connecting upwards with Triassic prerift salt. During continental breakup, basin shoulders recorded the occurrence of brittle deformation, whereas the hyperextended domain remained under predominantly ductile thinning. The formation of smooth-slope-type extensional basins was intrinsically linked to the combined deposition of thick syn-rift and breakup sequences, and regional salt tectonics. They induced significant burial and allowed the continental crust and the prerift sequence to deform under high temperature conditions from the rifting to continental breakup stages. [ABSTRACT FROM AUTHOR]

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]

This study documents the sedimentary and structural response of continental crust in relatively hot lithosphere that is subjected to extension. We focus on the Permian rift system in the Western Pyrenees, where the narrow, post-orogenic intracontinental extensional Bidarray Basin is in contact with late Variscan granulites of the Ursuya massif. The western margin of the N-S trending Bidarray Basin preserves alluvial fans dominated by hyperconcentrated flows and interdigitating eastward into a N-S trending fluvial system. Structural analysis of the Ursuya granulites shows that they underwent orogen-parallel mid-crustal flow and were exhumed owing to strain localization during retrogressive metamorphism within an extensional shear zone flanking an E-W elongated domal structure. We show that the Bidarray Basin formed during Permian time on the hanging wall of a south-vergent detachment system that developed in response to the formation of an immature "a-type" metamorphic core complex (the Ursuya massif) under regional E-W extension, resulting in homogeneous thinning of the hot crust. This core complex was later exposed by denudation during Cenomanian time. The preservation of the Permian and Triassic paleogeography and structure indicates that there has been no lateral motion between Iberia and Europe in the study area. The Cretaceous Pamplona transfer zone, responsible for the shift of the Mesozoic rift axis, reactivated a N-S trending Permian crustal heterogeneity. • The N-S Bidarray basin is filled by E-W alluvial fans interdigitating with an N-S fluvial system. • The Permian basin formation and the exhumation of granulites are coeval, induced by a single E-W extensional phase. • The Ursuya gneiss dome is interpreted as an "a-type" metamorphic core complex. • Permian-Triassic paleogeographic and structural templates preservation despite Cretaceous rifting and Tertiary inversion. • Mesozoic strike-slip motion of Iberia may have been distributed within the Cretaceous rift or affect a more southern area. [ABSTRACT FROM AUTHOR]