(A) Bouguer gravity map of the western part of the Pyrenean Belt displaying a positive anomaly coinciding with the inverted hyperextended domain of the Mauléon Basin (Chevrot et al., 2018). The bold line is the location of the lithospheric profile of Figure 2D. Contour interval, 10 mgal; (B) Geologic map of the Mauléon Basin (modified from Saspiturry et al., 2019b). Major south-vergent thrust faults, shown in red, include the North Arbailles Thrust (NaT), South Arbailles Thrust (SaT), and Lakhoura Thrust (LakT). Major north-vergent thrust faults, shown in purple, include the Saint-Palais Thrust (StPT), Bellevue Thrust (BeT), Sainte-Suzanne Thrust (SsT), and North Pyrenean Frontal Thrust (NPFT). Teeth on upthrown side. St-E-B: Saint-Étienne-de-Baïgorry; Bi: Bidarray Permian Basin. Boreholes: Ai: Ainhice; Be: Bellevue; Oz: Orthez; Um: Uhart-Mixe; CA: Croissant d’Arberoue; CB: Chaînons Béarnais; (C) Structural map showing domains of the Early Cretaceous Mauléon Basin; (D) Lithospheric cross-section of the Mauléon Basin. The upper part corresponds to the crustal-scale balanced cross-section of Saspiturry et al. (2020a) and the lower part is derived from the Vp model of Wang et al. (2016) showing the presence at shallow depth of continental lithospheric mantle inherited from previous Cretaceous hyperextension. GR: Grand Rieu High; (E) Palinspastic restoration, to Santonian time, of the crustal cross-section shown in Figure 2D. Extensional structures: LAD: Lakhoura Detachment; NAD: North Arbailles Detachment; StPD: Saint-Palais Detachment; SsF: Sainte-Suzanne Normal Fault.