3 research outputs found
Evolution of a low convergence collisional orogen: a review of Pyrenean orogenesis
The Pyrenees is a collisional orogen built by inversion of an immature rift system during convergence of the Iberian and European plates from Late Cretaceous to late Cenozoic. The full mountain belt consists of the pro-foreland southern Pyrenees and the retro-foreland northern Pyrenees, where the inverted lower Cretaceous rift system is mainly preserved. Due to low overall convergence and absence of oceanic subduction, this orogen preserves one of the best geological records of early orogenesis, the transition from early convergence to main collision and the transition from collision to post-convergence. During these transitional periods major changes in orogen behavior reflect evolving lithospheric processes and tectonic drivers. Contributions by the OROGEN project have shed new light on these critical periods, on the evolution of the orogen as a whole, and in particular on the early convergence stage. By integrating results of OROGEN with those of other recent collaborative projects in the Pyrenean domain (e.g., PYRAMID, PYROPE, RGF-Pyrénées), this paper offers a synthesis of current knowledge and debate on the evolution of this immature orogen as recorded in the synorogenic basins and fold and thrust belts of both the upper European and lower Iberian plates. Expanding insight on the role of salt tectonics at local to regional scales is summarised and discussed. Uncertainties involved in data compilation across a whole orogen using different datasets are discussed, for example for deriving shortening values and distribution
Evidence of decoupled deformation during Jurassic rifting and Cenozoic inversion phases in the salt-rich CorbiÚres-Languedoc Transfer Zone (Pyreneo-Provençal orogen, France)
A detailed field study of Jurassic tectono-stratigraphic architecture of the southwestern part of the CorbiÚres-Languedoc Transfer Zone (CLTZ, NE-SW oriented), between the Pyrenean and Provençal orogenic segments (N110 oriented) in SE France, document for the first time variations in thickness and stratigraphic geometries in relation to oblique extensional cover structures (NE-SW and N110 oriented). These structures (low-dip normal faults, salt rollers, rollovers, forced folds) formed during a Jurassic extension phase with strong decoupling between basement and cover on the Keuper pre-rift salt (Carnian-Norian evaporites). Some of these structures such as the Treilles Fault, the Valdria and the Terres Noires fold pairs, were previously interpreted as compressional and Pyrenean in origin (Late Santonian-Bartonian). Our study instead shows that these are Jurassic extensional and salt related structures, which were later affected by Pyrenean compression and Oligo-Miocene extension. Evidence of Jurassic extension is still observable in the field despite later rectivations, making these good field analogs for gently inverted extensional salt structures. During the Jurassic the interference between oblique structures above Keuper, leads to the formation of three dimensional growth strata observable at kilometric scale. Despite the mechanical decoupling effect of Keuper, we infer that their formation was linked to a strong interaction between oblique basement structures (NE-SW and N110) as the area lies during the Jurassic at the intersection between the eastern part of the Pyrenean E-W trending rift system and the NE-SW trending European margin of the Alpine Tethys rift. The decoupled deformation and the strong segmentation above and below Keuper detachement are here identified as Jurassic structural inheritence for later tectonic events, notably for the Nappe des CorbiÚres Orientales emplaced at the end of Pyrenean orogenesis. Associated to previous works, this study highlights that the CLTZ is a key area to better understand Pyreneo-Provençal system evolution along its whole Wilson cycle and to better understand the processes that govern the formation of a salt-rich transfer zone in a strongly pre-structured crust, its multiple reactivations and the decoupling role of salt
Evolution of a low convergence collisional orogen: a review of Pyrenean orogenesis
International audienceThe Pyrenees is a collisional orogen built by inversion of an immature rift system during convergence of the Iberian and European plates from Late Cretaceous to late Cenozoic. The full mountain belt consists of the pro-foreland southern Pyrenees and the retro-foreland northern Pyrenees, where the inverted lower Cretaceous rift system is mainly preserved. Due to low overall convergence and absence of oceanic subduction, this orogen preserves one of the best geological records of early orogenesis, the transition from early convergence to main collision and the transition from collision to post-convergence. During these transitional periods major changes in orogen behavior reflect evolving lithospheric processes and tectonic drivers. Contributions by the OROGEN project have shed new light on these critical periods, on the evolution of the orogen as a whole, and in particular on the early convergence stage. By integrating results of OROGEN with those of other recent collaborative projects in the Pyrenean domain (e.g., PYRAMID, PYROPE, RGF-PyrĂ©nĂ©es), this paper offers a synthesis of current knowledge and debate on the evolution of this immature orogen as recorded in the synorogenic basins and fold and thrust belts of both the upper European and lower Iberian plates. Expanding insight on the role of salt tectonics at local to regional scales is summarised and discussed. Uncertainties involved in data compilation across a whole orogen using different datasets are discussed, for example for deriving shortening values and distribution.Les PyrĂ©nĂ©es sont un petit orogĂšne de collision Ă faible convergence construit par inversion dâun systĂšme de rift immature au cours de la convergence des plaques ibĂ©rique et europĂ©enne du CrĂ©tacĂ© supĂ©rieur au CĂ©nozoĂŻque. La ceinture montagneuse comprend les PyrĂ©nĂ©es mĂ©ridionales (pro-avant-pays) et les PyrĂ©nĂ©es septentrionales (rĂ©tro-avant-pays), oĂč le systĂšme de rift hĂ©ritĂ© du CrĂ©tacĂ© infĂ©rieur est principalement prĂ©servĂ©. En raison de la faible convergence globale et de lâabsence de subduction ocĂ©anique, lâorogĂšne pyrĂ©nĂ©en conserve lâun des meilleurs enregistrements gĂ©ologiques de lâorogenĂšse prĂ©coce, de la transition de la convergence prĂ©coce Ă la collision principale et de la transition de la collision Ă la post-convergence. Ces pĂ©riodes de transition enregistrent des changements majeurs dans le comportement de lâorogĂšne, reflĂ©tant lâĂ©volution des processus lithosphĂ©riques et des moteurs tectoniques. Les contributions du projet OROGEN ont apportĂ© un nouvel Ă©clairage sur ces pĂ©riodes critiques, sur lâĂ©volution de lâorogĂšne dans son ensemble, et en particulier sur la phase de convergence prĂ©coce. En intĂ©grant les rĂ©sultats dâOROGEN aux rĂ©sultats dâautres projets de recherche collaboratifs rĂ©cents sur le domaine pyrĂ©nĂ©en (PYRAMID, PYROPE, RGF-PyrĂ©nĂ©es), cet article propose une synthĂšse des connaissances actuelles et des dĂ©bats sur lâĂ©volution de cet orogĂšne immature tel quâenregistrĂ© en particulier dans les bassins synorogĂ©niques et les chaĂźnes plissĂ©es des plaques europĂ©ennes et ibĂ©riques. LâĂ©largissement des connaissances sur le rĂŽle de la tectonique salifĂšre aux Ă©chelles locales et rĂ©gionales est rĂ©sumĂ© et discutĂ©. Les incertitudes impliquĂ©es dans la compilation des donnĂ©es sur lâensemble dâun orogĂšne Ă lâaide de diffĂ©rents ensembles de donnĂ©es sont discutĂ©es, par exemple pour estimer les valeurs de raccourcissement et sa distribution