Role of rift structural inheritance in orogeny highlighted by the Western Pyrenees case-study

International audienc

Extreme Mesozoic crustal thinning in the Eastern Iberia margin: The example of the Columbrets Basin (Valencia Trough)

Eastern Iberia preserves a complex succession of Mesozoic rifts partly or completely inverted during the Late Cretaceous and Cenozoic in relation with Africa-Eurasia convergence. Notably, the Valencia Trough, classically viewed as part of the Cenozoic West Mediterranean basins, preserves in its southwestern part a thick Mesozoic succession (locally ≈10 km thick) over a highly thinned continental basement (locally only ≈3.5 km thick). This subbasin, referred to as the Columbrets Basin, represents a Late Jurassic-Early Cretaceous hyperextended rift basin weakly overprinted by subsequent events. Its initial configuration is well preserved allowing us to unravel its 3-D architecture and tectonostratigraphic evolution in the frame of the Mesozoic evolution of eastern Iberia. The Columbrets Basin benefits from an extensive data set combining high-resolution seismic reflection profiles, drill holes, seismic refraction data, and expanding spread profiles. The interactions between halokinesis, involving the Upper Triassic salt, and extensional deformation controlled the architecture of the Mesozoic basin. The thick uppermost Triassic to Cretaceous succession displays a large-scale 'syncline' shape, progressively stretched and dismembered toward the basin borders. We propose that the SE border of the basin is characterized by a large extensional detachment fault acting at crustal scale and interacting locally with the Upper Triassic décollement. This extensional structure accommodates the exhumation of the continental basement and part of the crustal thinning. Eventually, our results highlight the complex interaction between extreme crustal thinning and occurrence of a prerift salt level for the deformation style and tectonostratigraphic evolution of hyperextended rift basins

Editorial: continental margins unleashed - from their early inception to continental breakup

It is clear from new state-of-the-art data that the processes responsible for ‘unleashing’ tectonic plates are distinct when moving across, and along, continental margins. There is simply no evolutionary sequence that applies to all continental margins, and even adjacent sedimentary basins on the same continental margins are known to record distinct geological processes during their formation. Of key importance to characterise their economic potential, the last tectonic pulses that fully separate, or rift, distinct continents have the potential to affect the thermal and structural evolutions of the areas where continental margins will soon form. This Special Issue presents new data from economically significant areas of continental margins where exploration work is ongoing, or just started, not only in terms of their hydrocarbon potential, but also as hosts of water, geothermal and mineral resources. Contributions to the Special Issue vary from tackling local, but important, sources of fluid in new frontier areas, to broad plate-scale geophysical modelling explaining continental breakup, and regional tectono-stratigraphic analyses of new frontier areas

Les reliques téthysiennes en Méditerranée orientale: les bassins Ionien, d'Hérodote et du Levant

National audienc

Reappraisal of the magma-rich versus magma-poor rifted margin archetypes

Abstract Rifted margins are commonly defined as magma-poor or magma-rich archetypes based on their morphology. We re-examine the prevailing model inferred from this classification that magma-rich margins have excess decompression melting at lithospheric breakup compared with steady-state seafloor spreading, while magma-poor margins have inhibited melting. We investigate the magmatic budget related to lithospheric breakup along two high-resolution long-offset deep reflection seismic profiles across the SE Indian (magma-poor) and Uruguayan (magma-rich) rifted margins. Resolving the magmatic budget is difficult and several interpretations can explain our seismic observations, implying different mechanisms to achieve lithospheric breakup and melt production for each archetype. We show that the Uruguayan and other magma-rich margins may indeed involve excess decompression melting compared with steady-state seafloor spreading but could also be explained by a gradual increase with an early onset relative to crustal breakup. A late onset of decompression melting relative to crustal breakup enables mantle exhumation characteristic of magma-poor margin archetypes (e.g. SE India). Despite different volumes of magmatism, the mechanisms suggested at lithospheric breakup are comparable between both archetypes. Considerations on the timing of decompression melting onset relative to crustal thinning may be more important than the magmatic budget to understand the evolution and variability of rifted margins.</jats:p

Rôle de l’hyper-extension lors de la formation de systèmes de rift et implication pour les processus de réactivation et de formation des orogènes : l’exemple du Golfe de Gascogne et des Pyrénées

Knowledge on lithosphere extensional mechanisms has greatly benefited from studies made both at presentday rifted margins and onshore fossil analogues. Nevertheless, the spatial and temporal evolution of the processes leading to continental break-up and oceanic crust formation remains poorly constrained. The Bay of Biscay and Pyrenees is used in this study as a natural laboratory to investigate the formation and reactivation of rift systems. A new offshore-onshore approach is developed and applied to identify, characterize and map the rift domains inherited from the Bay of Biscay opening and partly integrated into the Pyrenean orogen. This mapping reveals the complex architecture of European-Iberian plate boundary resulting from a strongly polyphased evolution. Several rift systems spatially distinct are preserved at different evolutionary stages. An important segmentation partially inherited from the pre-rift structuration controls the formation of the rift systems, an observation that has important implications for regional kinematic restorations. Several steps in compressional deformation can be distinguished and related to the rift inherited architecture. Reactivation is initiated in the exhumed mantle domain. Following the subduction of hyperthinned crust, continental collision processes are controlled by the proximal and necking domains acting as buttresses. These results emphasize the role of pre-rift inheritance for the spatial evolution of rift systems and the importance of the rift-related architecture to unravel the formation of collisional orogen.Les études couplant des observations provenant des marges passives actuelles et d’analogues fossiles ont permis de mieux appréhender les mécanismes d’extension de la lithosphère. Néanmoins, l’évolution spatiale et temporelle des processus de rupture continentale et de formation de croûte océanique reste mal contrainte. Le Golfe de Gascogne et les Pyrénées sont utilisés dans ce travail comme laboratoire naturel pour étudier la formation et la réactivation des systèmes de rift. Le développement et l’application d’une approche terre-mer a permis d’identifier, caractériser et cartographier les domaines de rift formés lors de l’ouverture du Golfe de Gascogne et partiellement intégrés à l’orogène Pyrénéenne. Cette cartographie révèle l’architecture complexe de la limite de plaque Ibérie-Europe résultant d’une évolution fortement polyphasée. Plusieurs systèmes de rift spatialement distincts sont préservés à des stades d’évolution différents. Une segmentation importante partiellement héritée de la structuration prérift contrôle la formation des systèmes de rift ce qui a des implications pour la cinématique régionale. Plusieurs étapes de la déformation compressive ont pu être distinguées et mises en relation avec l’architecture héritée du rift. La réactivation est initiée dans le domaine de manteau exhumé. Après lasubduction de croûte hyper-amincie, la collision continentale est contrôlée par les domaines proximaux et de necking qui jouent le rôle de buttoirs. Ces résultats soulignent l’interaction étroite entre l’héritage pré-rift et l’évolution spatiale des systèmes de rift ainsi que l’importance de l’architecture du rift pour comprendre la formation des orogènes

Rôle de l hyper-extension lors de la formation de systèmes de rift et implication pour les processus de réactivation et de formation des orogènes (l exemple du Golfe de Gascogne et des Pyrénées)

Les études couplant des observations provenant des marges passives actuelles et d analogues fossiles ont permis de mieux appréhender les mécanismes d extension de la lithosphère. Néanmoins, l évolution spatiale et temporelle des processus de rupture continentale et de formation de croûte océanique reste mal contrainte. Le Golfe de Gascogne et les Pyrénées sont utilisés dans ce travail comme laboratoire naturel pour étudier la formation et la réactivation des systèmes de rift. Le développement et l application d une approche terre-mer a permis d identifier, caractériser et cartographier les domaines de rift formés lors de l ouverture du Golfe de Gascogne et partiellement intégrés à l orogène Pyrénéenne. Cette cartographie révèle l architecture complexe de la limite de plaque Ibérie-Europe résultant d une évolution fortement polyphasée. Plusieurs systèmes de rift spatialement distincts sont préservés à des stades d évolution différents. Une segmentation importante partiellement héritée de la structuration prérift contrôle la formation des systèmes de rift ce qui a des implications pour la cinématique régionale. Plusieurs étapes de la déformation compressive ont pu être distinguées et mises en relation avec l architecture héritée du rift. La réactivation est initiée dans le domaine de manteau exhumé. Après lasubduction de croûte hyper-amincie, la collision continentale est contrôlée par les domaines proximaux et de necking qui jouent le rôle de buttoirs. Ces résultats soulignent l interaction étroite entre l héritage pré-rift et l évolution spatiale des systèmes de rift ainsi que l importance de l architecture du rift pour comprendre la formation des orogènes.Knowledge on lithosphere extensional mechanisms has greatly benefited from studies made both at presentday rifted margins and onshore fossil analogues. Nevertheless, the spatial and temporal evolution of the processes leading to continental break-up and oceanic crust formation remains poorly constrained. The Bay of Biscay and Pyrenees is used in this study as a natural laboratory to investigate the formation and reactivation of rift systems. A new offshore-onshore approach is developed and applied to identify, characterize and map the rift domains inherited from the Bay of Biscay opening and partly integrated into the Pyrenean orogen. This mapping reveals the complex architecture of European-Iberian plate boundary resulting from a strongly polyphased evolution. Several rift systems spatially distinct are preserved at different evolutionary stages. An important segmentation partially inherited from the pre-rift structuration controls the formation of the rift systems, an observation that has important implications for regional kinematic restorations. Several steps in compressional deformation can be distinguished and related to the rift inherited architecture. Reactivation is initiated in the exhumed mantle domain. Following the subduction of hyperthinned crust, continental collision processes are controlled by the proximal and necking domains acting as buttresses. These results emphasize the role of pre-rift inheritance for the spatial evolution of rift systems and the importance of the rift-related architecture to unravel the formation of collisional orogen.STRASBOURG-Bib.electronique 063 (674829902) / SudocSudocFranceF

Formation of the Alpine orogen by amagmatic convergence and assembly of previously rifted lithosphere

International audienceThe tectonic and magmatic characteristics of the Alps and Pyrenees during convergence are quite distinct from characteristics associated with classic Benioff-type oceanic subduction. From the initiation of subduction at passive margins until the onset of continental collision, the closure of the Western Tethys never produced a longlived magmatic arc. This is a consequence of the 3-D architecture of the Western Tethys (a series of hyper-thinned basins and continental blocks) and its narrow width (<500-700 km) prior to convergence. Subduction primarily involved the slow and amagmatic subduction of a narrow domain of dry lithospheric mantle. This type of congested Ampferer subduction led to the sequential and coherent accretion of inherited rifted domains which today form the Alpine and Pyrenean orogens

INVESTIGATING THE PLATE KINEMATICS OF THE BAY OF BISCAY USING DEFORMABLE PLATE TECTONIC MODELS

27 pages, 12 figures, 2 tables, supporting Information https://doi.org/10.1029/2020TC006467.-- Data Availability Statement: Data used to perform gravity inversions are available through Andersen (2010), Divins (2003), Smith and Sandwell (1997), Muller et al. (1997), Sandwell and Smith (2009), and Tugend et al. (2014). Archiving of GPlates data files used to create deformable plate models can be found in the Mendeley Data repository at https://www.doi.org/10.17632/k3kp22yxs7.1The plate kinematics of the Iberian plate and their implications on the plate tectonic evolution of the Bay of Biscay during rifting and subsequent opening of the southern North Atlantic continue to be topics of scientific discussion and debate. Constrained by previous plate reconstruction, geophysical, and geological studies, deformable plate tectonic reconstructions of the Bay of Biscay-Parentis rift system are created in this study using the GPlates software. These deformable plate models are used to investigate the kinematics of the Landes High, Le Danois High, and Ebro Block previously recognized as independent continental blocks within deformable regions. A comparison between results calculated via deformable plate models with previously published and newly presented gravity inversion crustal thickness estimates provided a good metric for delineating the most probable plate kinematic scenario for the Bay of Biscay-Parentis system and investigating the effect of the plate kinematic scenarios on the present-day structure. The preferred plate kinematic model implies a transtensional Bay of Biscay-Parentis rift system from the Jurassic to Early Cretaceous, with the onset of significant crustal thinning initiating during the Late Jurassic (∼150 Ma) induced by the motion of the Landes High and its interplay with the Ebro Block. Aside from demonstrating the role of the Landes High and its suggested interplay with structural inheritance on the deformation experienced within the Bay of Biscay, the timing and orientation of regional stress directions, and the velocities induced by the preferred deformable model provide good comparisons with previously calculated subsidence ratesFunding for this project was provided by Natural Sciences and Engineering Research Council of Canada (NSERC), Husky Energy, Nalcor Energy, and the Department of Environment, Climate, and Communications of IrelandWith the institutional support of the ‘Severo OchoaCentre of Excellence’ accreditation (CEX2019-000928-S)Peer reviewe