Initiation de l'accrétion continentale dans le domaine bétique

The thermo-chronological study of syn- to post-rift and syn-orogenic sediments makes it possible to reconstruct the time-temperature evolution of the basins at the different stages of the orogenesis. This study combined with structural and stratigraphic observations makes it possible to determine the spatial and temporal evolution of the passive margin from the early stages of its inversion to the final stages of the collision associated with the rapid exhumation of the metamorphic internal units. The Betic and Rif cordilleras belong to the western end of the peri-Mediterranean chains. The geodynamic history associated with the formation of the Betics since the Oligocene is deeply marked by a combination of processes of slab retreat, tearing and delamination of the continental and / or oceanic lithosphere in the context of convergence between Africa and Europe. In response, the crust that today forms the Alboran Basin and the internal areas of Betic and Rif has been subject to extension in the back arc area since the Oligocene. This extension phase was synchronous with the compressive deformations recorded in the Meso-Cenozoic coverage of the Iberian and North African margins and the formation of the pleated pre-country chains. The use of fission and (U-Th) / He low-temperature thermochronological analyzes on apatite applied to the Cretaceous and Tertiary flysch series of the Mauretanian and Massylian domains highlights the importance of a phase of Paleogene exhumation. Combined with structural and stratigraphic observations, it appears that this episode of exhumation is associated with the development of a foreland all along the Betic Cordillera for nearly 400 km. An examination of structural relationships between flyschs, subbetic series and the Triassic shows that salt tectonics played a major role. This observation leads to explain the current structure of the external zones of the Betics while decreasing the extent of the tectonic movements. Combined with detrital zircon U-Pb dating, which constrains Mesozoic and Cenozoic flysch units, between Iberian, Alboran and African sources, the results of this work have made it possible to specify the palaeogeographic and geodynamics of the Betics since the Western Transition Tethys-Atlantic, the collision stage Alpine, until its current evolution associated with the opening of the Western Mediterranean.L'étude thermo-chronologique des sédiments syn- à post-rift et syn-orogéniques permet de reconstituer l'évolution temps-température des bassins aux différent stades de l'orogenèse. Cette étude combinée à des observations structurales et stratigraphiques permet en effet de déterminer l'évolution spatial et temporelle de la marge passive depuis les premiers stades de son inversion jusqu'aux stades finaux de la collision associés à l'exhumation rapide des unités internes métamorphiques. Les Cordillères des Bétiques et du Rif appartiennent à l'extrémité occidentale des chaînes péri-méditerranéennes. L'histoire géodynamique, associée à la formation des Bétiques depuis l'Oligocène est marquée en profondeur par une combinaison de processus de retrait, de déchirement et de délamination de la lithosphère continentale et ou océanique dans le contexte de convergence entre l'Afrique et l'Europe. En réponse, la croûte qui forme aujourd'hui le bassin d'Alboran et les zones internes des Bétiques et du Rif a été soumise à une extension dans la zone d'arrière arc depuis l'Oligocène. Cette phase d'extension a été synchrone des déformations compressives enregistrées dans la couverture méso-cénozoïque des marges Ibérique et nord-africaine et la formation des chaines plissées d'avant pays. L'utilisation d'analyses thermochronologiques basse-température traces de fission et (U-Th)/He sur apatite appliquées aux séries de flyschs d'âge Crétacé et Tertiaire du domaine Maurétanien et Massylien met en evidence l'importance d'une phase d'exhumation Paléogène. Combiné aux observations structurales et stratigraphiques il apparaît que cette épisode d'exhumation est associé au développement d'un avant-pays tout le long des Cordillères Bétiques sur près de 400 km. L'examen des relations structurales entre les flyschs, les séries subbétiques et le Trias démontre que la tectonique salifère a joué un rôle majeur. Cette observation conduit à expliquer la structure actuelle des zones externes des Bétiques tout en diminuant l'ampleur des mouvements tectoniques. Combinées aux datations U-Pb sur zircons détritiques qui contraignent les provenances des unités de flyschs au Mésozoïque et au Cénozoïque, entre des sources Ibériques, d'Alboran et d'Afrique, les résultats de ce travail ont permis de préciser l'évolution paléogéographique et géodynamique des Bétiques depuis la transition Ouest Tethys-Atlantique, le stade collision Alpine, jusqu'à son évolution actuelle associée à l'ouverture de la Méditerranée Occidentale

Initiation of continental accretion in the betique rif domain

L'étude thermo-chronologique des sédiments syn- à post-rift et syn-orogéniques permet de reconstituer l'évolution temps-température des bassins aux différent stades de l'orogenèse. Cette étude combinée à des observations structurales et stratigraphiques permet en effet de déterminer l'évolution spatial et temporelle de la marge passive depuis les premiers stades de son inversion jusqu'aux stades finaux de la collision associés à l'exhumation rapide des unités internes métamorphiques. Les Cordillères des Bétiques et du Rif appartiennent à l'extrémité occidentale des chaînes péri-méditerranéennes. L'histoire géodynamique, associée à la formation des Bétiques depuis l'Oligocène est marquée en profondeur par une combinaison de processus de retrait, de déchirement et de délamination de la lithosphère continentale et ou océanique dans le contexte de convergence entre l'Afrique et l'Europe. En réponse, la croûte qui forme aujourd'hui le bassin d'Alboran et les zones internes des Bétiques et du Rif a été soumise à une extension dans la zone d'arrière arc depuis l'Oligocène. Cette phase d'extension a été synchrone des déformations compressives enregistrées dans la couverture méso-cénozoïque des marges Ibérique et nord-africaine et la formation des chaines plissées d'avant pays. L'utilisation d'analyses thermochronologiques basse-température traces de fission et (U-Th)/He sur apatite appliquées aux séries de flyschs d'âge Crétacé et Tertiaire du domaine Maurétanien et Massylien met en evidence l'importance d'une phase d'exhumation Paléogène. Combiné aux observations structurales et stratigraphiques il apparaît que cette épisode d'exhumation est associé au développement d'un avant-pays tout le long des Cordillères Bétiques sur près de 400 km. L'examen des relations structurales entre les flyschs, les séries subbétiques et le Trias démontre que la tectonique salifère a joué un rôle majeur. Cette observation conduit à expliquer la structure actuelle des zones externes des Bétiques tout en diminuant l'ampleur des mouvements tectoniques. Combinées aux datations U-Pb sur zircons détritiques qui contraignent les provenances des unités de flyschs au Mésozoïque et au Cénozoïque, entre des sources Ibériques, d'Alboran et d'Afrique, les résultats de ce travail ont permis de préciser l'évolution paléogéographique et géodynamique des Bétiques depuis la transition Ouest Tethys-Atlantique, le stade collision Alpine, jusqu'à son évolution actuelle associée à l'ouverture de la Méditerranée Occidentale.The thermo-chronological study of syn- to post-rift and syn-orogenic sediments makes it possible to reconstruct the time-temperature evolution of the basins at the different stages of the orogenesis. This study combined with structural and stratigraphic observations makes it possible to determine the spatial and temporal evolution of the passive margin from the early stages of its inversion to the final stages of the collision associated with the rapid exhumation of the metamorphic internal units. The Betic and Rif cordilleras belong to the western end of the peri-Mediterranean chains. The geodynamic history associated with the formation of the Betics since the Oligocene is deeply marked by a combination of processes of slab retreat, tearing and delamination of the continental and / or oceanic lithosphere in the context of convergence between Africa and Europe. In response, the crust that today forms the Alboran Basin and the internal areas of Betic and Rif has been subject to extension in the back arc area since the Oligocene. This extension phase was synchronous with the compressive deformations recorded in the Meso-Cenozoic coverage of the Iberian and North African margins and the formation of the pleated pre-country chains. The use of fission and (U-Th) / He low-temperature thermochronological analyzes on apatite applied to the Cretaceous and Tertiary flysch series of the Mauretanian and Massylian domains highlights the importance of a phase of Paleogene exhumation. Combined with structural and stratigraphic observations, it appears that this episode of exhumation is associated with the development of a foreland all along the Betic Cordillera for nearly 400 km. An examination of structural relationships between flyschs, subbetic series and the Triassic shows that salt tectonics played a major role. This observation leads to explain the current structure of the external zones of the Betics while decreasing the extent of the tectonic movements. Combined with detrital zircon U-Pb dating, which constrains Mesozoic and Cenozoic flysch units, between Iberian, Alboran and African sources, the results of this work have made it possible to specify the palaeogeographic and geodynamics of the Betics since the Western Transition Tethys-Atlantic, the collision stage Alpine, until its current evolution associated with the opening of the Western Mediterranean

Array of time reversal transceivers: An application to acoustic focusing

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Tectono‐Stratigraphic and Thermal Evolution of the Western Betic Flysch: Implications for the Geodynamics of South Iberian Margin and Alboran Domain

International audienceThe Betic-Rif orogen is a key region to understand the evolution of the plate boundary between Africa and Iberia/Europe. This study focuses on the Flysch Complex, which is considered the sedimentary cover of a domain originally positioned between the Iberian and Alboran margins. Based on stratigraphic and depositional evolution constraints, evidence for salt tectonics, combined with new apatite fission-tracks (AFT) and (U-Th-Sm)/He ages from the Flysch Complex and the Subbetic Zone, we propose a geodynamic interpretation for the formation of the Betic Cordillera, accounting for moderate N-directed transport of the Flysch Complex and synchronous exhumation between External and Internal Zones of the Betic. Early contraction between Africa and Iberia/Europe is reflected in the Cretaceous Flysch basin by a prolonged period of residence in the partial annealing zone for AFT and onset of foreland subsidence at 50 Ma. This stage lasted until the Early to Middle Miocene (20-15 Ma), marked by the rapid succession, in less than 5 Ma, of the deposition of Cenozoic flysch and their rapid exhumation. This event is interpreted to reflect the W-directed retreating mantle delamination between Africa and Iberia margins at the origin of the collapse of the proto-Betic orogenic domain and formation of the Alboran domain

Strain Partitioning and Exhumation in Oblique Taiwan Collision: Role of Rift Architecture and Plate Kinematics

International audienceTaiwan is an archetypal example of continental accretionary wedges. Yet the generally poor knowledge of three-dimensional strain distribution over time and role of architecture of the rifted margin shed doubt on the cylindrical two-dimensional kinematic models of Taiwan collision. Here we provide new field-based constraints on strain distribution, new Raman Spectroscopy on Carbonaceous Materials temperatures and apply mica-chlorite multiequilibrium approach to determine pressure-temperature in the Central Range of Taiwan. We identify three distinct structural domains that define zones of orthogonal shortening in the western Backbone Range and left-lateral ductile shearing overprinted by left-lateral transtensional brittle deformation in eastern Central Range. Field surveys show the lack of nappe stacking in the Backbone Range. Combining new temperature estimates with existing thermochronological constraints we emphasize that western Taiwan mostly inherited preorogenic thermal history. We show that metamorphic peak conditions of 5-6 kbar and 330-400 °C in the eastern Backbone Range and HP rocks of the Yuli Belt exhumed along the P-T paths related to transcurrent deformation. We propose a three-dimensional kinematic model of Taiwan accounting for the oblique motion of the Philippine Sea Plate relative to the plate boundary and the reactivation of a NS striking transform fault in the South China Sea rifted margin. Recent and ongoing strain partitioning in the Taiwan accretionary wedge is reflected by the coexistence of brittle left-lateral shear, oblique extension, and contraction. Our results have impact on orogen-based plate kinematic reconstructions that consider two-dimensional kinematic evolution of orogens

Rift-to-collision transition recorded by tectono-thermal evolution of the northern Pyrenees

International audienceThe impact of rift-related processes on tectonic and thermal evolution of collisional orogens is poorly documented. Here, we study the northern Pyrenees, a region that has preserved a geological record of the transition from rifting to collision. Using modeling of new low-temperature thermochronological data, including fission track and (U-Th)/He on apatite and zircon, we propose a temporal reconstruction of the inversion of the European rifted margin. Our data confirm that rifting and related cooling started in the Late Paleozoic-Triassic. Throughout the Jurassic and Early Cretaceous the European margin recorded slow heating during postrift subdsidence. Modeling of thermochronological data allows distinguishing subsidence and denudation controlled by south dipping normal faults in granitic massifs that reflect a second episode of crustal thinning at 130–110 Ma. Following onset of convergence at 83 Ma, shortening accumulated into the weak and hot Albian-Cenomanian rift basins floored by both hyperextended continental crust and exhumed subcontinental mantle. The lack of cooling during this initial stage of convergence is explained by the persistence of a high geothermal gradient. The onset of exhumation-related cooling is recognized in the whole Pyrenean region at 50–35 Ma. This timing reveals that the main phase of mountain building started when hyperextended rift basins closed and collision between proximal domains of the rifted margin occurred