In this field study we reinterpret the narrow eastern North Pyrenean Zone, France, as an inverted salt-rich transtensive rift system based on identification of halokinetic depositional sequences across rift platform to distal rift margin domains with a cumulative throw of >2.8 km on steep Cretaceous faults. The rift platform records extension on detached rotational faults above pre-rift Triassic evaporites to end Aptian with uplift and erosion during main Albian rifting. Transtensional Aptian-Albian minibasins align along the salt-rich rift margin fault zone. In the main rift large en echelon minibasins developed between salt walls during the Aptian-Albian, although Jurassic diapiric evolution is likely. Upper Cretaceous units locally record ongoing diapirism. Boucheville and Bas Agly depocentres, altered by syn-rift HT metamorphism, form the distal rift domain terminating south against the North Pyrenean Fault. The narrowness of the Pyrenean rift, the shape of minibasins, the en echelon oblique synclinal depocentres and folds coupled with a discontinuous distribution and intensity of HT metamorphism support a transtensional regime along the Iberia-Europe plate margin during Early and early Late Cretaceous. In this model, the distal European margin comprises deep faults limiting laterally discontinuous crustal domains and 'hot' pull-apart basins with mantle rocks directly beneath sedimentary cover.
Scientific editing by Stephen Daly