Résumé
We present an overview of the Mid-Cretaceous hyper-extended rift systemexposed in the northern part of the Pyrenean mountain range. Itsinversion during the Pyrenean orogeny allows for precious observationsof the deep-seated processes occurring at the foot of distal margins.Some peculiar aspects characterizing the pre-Alpine hyper-extended domainare examined throughout the 400 km long suture that is fossilizedin the North Pyrenean Zone (NPZ). The high temperature/low pressure(HT/LP) thermal imprint of the extensional event is studied thanksto a dataset of more than hundred peak temperature measurementsby Raman spectroscopy of the carbonaceous material (RSCM). Thepre- and syn-rift metasediments are characterized by an intense, synmetamorphicductile deformation. Focusing on several key-localitiesof the NPZ, we examine the emplacement conditions of the peridotitesin response to this extreme crustal thinning. Geological evidencessuch as the occurrence of peridotite bodies directly underlying metamorphicpre-rift sediments indicate an early attenuation of the rifted continentalcrust. Moreover, syn-rift, Albian-Cenomanian flysch sequenceswere deposited synchronously with the syn-metamorphic ductile deformationof the pre-rift sequences. All along the Internal MetamorphicZone (IMZ), the base of the flysch deposits also recorded the HT tectonicevent. Such a synchronicity between geological events, which aregenerally separated in time, is not common in mountain belts. We examinehow tectonics, metamorphism and sedimentation may be activein a single basin during extension. We propose an original mechanismfor the evolution of the basins involving continuous basal extraction ofthe pre-rift metamorphic sediments. This early HT deformation eventrelates to the « phase anté-Cénomanienne » described by Pyrenean geologistssince 1930.