Comparative study of the Eastern Iberides (spain) and the Western Pyrenees (France) Mesozoic basins

Abstract

Three main periods characterize the geodynamic evolution of the Mesozoic basins located in the Eastern Iberides and the Western Pyrenees: 1. (1) From Triassic to Albian times, the breakup of the Hercynian basement led to the general formation of different-sized half-grabens. The regional distensional stress which generated such basins was oriented northwest-southeast (Triassic and Jurassic), then northeast-southwest (Early Cretaceous), with a high activity in the Early Triassic, the Early Lias, the Kimmeridgian, the Barremian and the Late Aptian. During the Early Cretaceous period, extensional tectonics induced block tilting, as well as halokinetic movements of the Triassic evaporites. 2. (2) The Albian period put an end to this common evolution. The rifting movements lessened considerably in the Eastern Iberian Basin where continental to coastal sandstones were deposited, whereas they accelerated in the West Pyrenean Basin, leading to flysch accumulations, related to the openning of the Bay of Biscay. 3. (3) The Late Cretaceous was characterized by the same opposed evolution of a shallow carbonate platform in the Eastern Iberides and a deep, terrigenous flysch basin in the Western Pyrenees. During Mesozoic times, both on the platforms and in the basins, the depositional sequence organisation was closely linked to eustatic sealevel changes. Nevertheless, the local extensional process generated important modifications in thickness, particularly within the Lower Triassic, the Liassic, the Kimmerdigian and the Aptian series as well as within the Pyrenean Middle and Upper Cretaceous deposits. The structural framework of both Eastern Iberian and Western Pyrenean areas was induced by the deformation of the Iberian Plate, related to relative sinistral movements of Africa with respect to Europe. The later structural evolution (Tertiary tectogenesis) was strongly influenced by the inherited Mesozoic framework, both in the Eastern Iberides, where the extensional structures are preserved and in the Western Pyrenees, where the important compressional stress led to generalized reversal tectonics.