A new look at old debates about the Corbières (NE-Pyrenees) geology: salt tectonics and gravity gliding

In the Corbières area, a large-scale nappe has been identified at the beginning of the 20th century: the “Nappe des Corbières Orientales” (NCO) resting over a thick Triassic sole. This geological object is located at the NE of the Pyrenees, close to the Gulf of Lions. At this place, the chain changes in orientation from E-W to NE-SW and presents in detail, a great complexity. The existence of the nappe itself has never been contested. However, due to its overall complexity, several controversies exist regarding the style and chronology of deformation of its substratum in the so-called the “Pinède de Durban” in particular. We show that the new concepts of salt tectonics can clarify these old debates. Indeed, the rise of the Triassic salt during Mesozoic rifting episodes results in the development of characteristic sedimentary sequences (halokinetic sequences) on top of salt walls. It is along one of these, coinciding with the prolongation of the Cévenole Fault System, that the NCO has been individualized. During its Cenozoic emplacement, a gravity-gliding component, explaining the importance of the observed translation, could result from an uplift preceding the rifting at the origin of the Gulf of Lions

Characterization and age of intraplate deformation in front of an orogen : from the North Pyrenean Frontal Thrust to the southern limit of the Massif Central, France

En géodynamique, l’essentiel des déformations est accommodé aux limites des plaques tectoniques. Pourtant, la propagation de la contrainte au-delà de ces frontières est à l’origine de déformations dites « intraplaques », d’intensité modérée mais qui contrôlent notamment des circulations de fluides et minéralisations. Ces déformations, et en particulier leur lien avec l’agenda tectonique établi en limite de plaque, sont aujourd’hui encore mal comprises : sont-elles antérieures, contemporaines, postérieures à la formation des orogènes ? S’agit-il d’épisodes uniques ou multiples, et sur quelle durée ? Les travaux présentés tentent de répondre à ces questions en s’appuyant sur la caractérisation du domaine intraplaque situé au Nord de la chaîne Pyrénéenne, dans la région des Corbières, du Languedoc et des Grands Causses. La méthode de datation U-Pb sur calcite de faille, développée en partie au laboratoire GEOPS au cours de ce travail, est couplée à une analyse structurale de chacune des zones afin de dater de manière absolue la déformation compressive dans les divers secteurs. Les résultats obtenus permettent ainsi de (1) préciser/établir les calendriers géodynamiques de chacun des secteurs (2) replacer ces déformations intraplaques dans le contexte géodynamique global et (3) établir le lien entre les déformations dans le domaine intraplaque et celles en bordure de plaque. Les travaux réalisés dans la région des Corbières, au front de l’orogène, mettent en évidence une phase de déformation au Lutétien, en décalage avec le paroxysme d’exhumation de la chaîne à l’Eocène supérieur. La région a également enregistré un évènement tectonique au Miocène, contemporain d’une phase d’exhumation de la chaîne, de la formation des surfaces « perchées » des Pyrénées et d’un épisode de déformation décrit sur le versant espagnol des Pyrénées. Le secteur du Languedoc, et en particulier le système de faille des Cévennes, enregistre une déformation associée à la compression pyrénéenne continue tout au long de l’Eocène. Par ailleurs les données U-Pb indiquent une activité à l’Albien de ce faisceau de failles, contemporaine de l’ouverture des bassins pyrénéens. Enfin, la région des Grands Causses correspondant au secteur d’étude le plus distal à la chaîne enregistre une déformation longue et continue du Crétacé inférieur à l’Eocène supérieur. L’ensemble de ces travaux démontre ainsi que la déformation en domaine intraplaque n’est pas limitée à l’enregistrement des phases paroxysmales de déformation en limite de plaque comme cela a pu être proposé auparavant, mais que le domaine intraplaque présente une grande sensibilité aux déformations en bordure de plaque, et donc une forte déformabilité sur des durées importantes avant, pendant et après la formation des orogènes en limite de plaque.In geodynamics, most of the deformation is accommodated at the edges of tectonic plates. However, the propagation of stress beyond these boundaries is at the origin of so-called "intraplate" deformations, which are of moderate intensity but control several processes, especially fluid circulations and mineralizations. These deformations, and in particular their link with the tectonic agenda established at the plate boundary, are still poorly understood today: are they anterior, coeval or posterior to the formation of the orogens? Are they single or multiple episodes, and over what duration? The work presented here aims to answer these questions by characterizing the intraplate domain located north of the Pyrenean Chain, in the Corbières, Languedoc and Grands Causses domains. The U-Pb geochronology on fault-related calcite, partly developed in the GEOPS laboratory during this work, is associated with a structural analysis of each domain in order to date its compressive deformation. The results obtained allow us to (1) clarify/establish the geodynamic timetables for each domain (2) place these intraplate deformations into the global geodynamic context and (3) establish the link between these deformations in the intraplate domain and those at the plate edges. Our results for the Corbières region, at the front of the orogen, reveal a phase of deformation during Lutetian times, offset from the paroxysm of exhumation in the chain at the Late Eocene. The region also records a miocene tectonic event coeval with the formation of the high elevation of low-relief surfaces of the Pyrenees and a deformation episode described on the Spanish side of the Pyrenees. The Languedoc area, and in particular the Cevennes Fault System, shows deformations associated with a continuous Pyrenean compression throughout the Eocene. In addition, U-Pb data indicate an albian activity of this fault system, coeval with the opening of the Pyrenean basins. Finally, the Grands Causses sector, corresponding to the study area farthest from the belt, shows a long and continuous deformation from the Lower Cretaceous to the Upper Eocene. All these results demonstrate that deformation in the intraplate domain is not limited to the paroxysmal phases of plate boundary deformation as previously proposed. Indeed, the intraplate domain presents a high sensitivity to plate edges deformation and thus, a strong deformability over important time periods, before, during and after the formation of plate boundary orogens

Expression et âge de la déformation intraplaque au front d’un orogène : du Chevauchement Frontal Nord Pyrénéen à la bordure sud du Massif Central, France

In geodynamics, most of the deformation is accommodated at the edges of tectonic plates. However, the propagation of stress beyond these boundaries is at the origin of so-called "intraplate" deformations, which are of moderate intensity but control several processes, especially fluid circulations and mineralizations. These deformations, and in particular their link with the tectonic agenda established at the plate boundary, are still poorly understood today: are they anterior, coeval or posterior to the formation of the orogens? Are they single or multiple episodes, and over what duration? The work presented here aims to answer these questions by characterizing the intraplate domain located north of the Pyrenean Chain, in the Corbières, Languedoc and Grands Causses domains. The U-Pb geochronology on fault-related calcite, partly developed in the GEOPS laboratory during this work, is associated with a structural analysis of each domain in order to date its compressive deformation. The results obtained allow us to (1) clarify/establish the geodynamic timetables for each domain (2) place these intraplate deformations into the global geodynamic context and (3) establish the link between these deformations in the intraplate domain and those at the plate edges. Our results for the Corbières region, at the front of the orogen, reveal a phase of deformation during Lutetian times, offset from the paroxysm of exhumation in the chain at the Late Eocene. The region also records a miocene tectonic event coeval with the formation of the high elevation of low-relief surfaces of the Pyrenees and a deformation episode described on the Spanish side of the Pyrenees. The Languedoc area, and in particular the Cevennes Fault System, shows deformations associated with a continuous Pyrenean compression throughout the Eocene. In addition, U-Pb data indicate an albian activity of this fault system, coeval with the opening of the Pyrenean basins. Finally, the Grands Causses sector, corresponding to the study area farthest from the belt, shows a long and continuous deformation from the Lower Cretaceous to the Upper Eocene. All these results demonstrate that deformation in the intraplate domain is not limited to the paroxysmal phases of plate boundary deformation as previously proposed. Indeed, the intraplate domain presents a high sensitivity to plate edges deformation and thus, a strong deformability over important time periods, before, during and after the formation of plate boundary orogens.En géodynamique, l’essentiel des déformations est accommodé aux limites des plaques tectoniques. Pourtant, la propagation de la contrainte au-delà de ces frontières est à l’origine de déformations dites « intraplaques », d’intensité modérée mais qui contrôlent notamment des circulations de fluides et minéralisations. Ces déformations, et en particulier leur lien avec l’agenda tectonique établi en limite de plaque, sont aujourd’hui encore mal comprises : sont-elles antérieures, contemporaines, postérieures à la formation des orogènes ? S’agit-il d’épisodes uniques ou multiples, et sur quelle durée ? Les travaux présentés tentent de répondre à ces questions en s’appuyant sur la caractérisation du domaine intraplaque situé au Nord de la chaîne Pyrénéenne, dans la région des Corbières, du Languedoc et des Grands Causses. La méthode de datation U-Pb sur calcite de faille, développée en partie au laboratoire GEOPS au cours de ce travail, est couplée à une analyse structurale de chacune des zones afin de dater de manière absolue la déformation compressive dans les divers secteurs. Les résultats obtenus permettent ainsi de (1) préciser/établir les calendriers géodynamiques de chacun des secteurs (2) replacer ces déformations intraplaques dans le contexte géodynamique global et (3) établir le lien entre les déformations dans le domaine intraplaque et celles en bordure de plaque. Les travaux réalisés dans la région des Corbières, au front de l’orogène, mettent en évidence une phase de déformation au Lutétien, en décalage avec le paroxysme d’exhumation de la chaîne à l’Eocène supérieur. La région a également enregistré un évènement tectonique au Miocène, contemporain d’une phase d’exhumation de la chaîne, de la formation des surfaces « perchées » des Pyrénées et d’un épisode de déformation décrit sur le versant espagnol des Pyrénées. Le secteur du Languedoc, et en particulier le système de faille des Cévennes, enregistre une déformation associée à la compression pyrénéenne continue tout au long de l’Eocène. Par ailleurs les données U-Pb indiquent une activité à l’Albien de ce faisceau de failles, contemporaine de l’ouverture des bassins pyrénéens. Enfin, la région des Grands Causses correspondant au secteur d’étude le plus distal à la chaîne enregistre une déformation longue et continue du Crétacé inférieur à l’Eocène supérieur. L’ensemble de ces travaux démontre ainsi que la déformation en domaine intraplaque n’est pas limitée à l’enregistrement des phases paroxysmales de déformation en limite de plaque comme cela a pu être proposé auparavant, mais que le domaine intraplaque présente une grande sensibilité aux déformations en bordure de plaque, et donc une forte déformabilité sur des durées importantes avant, pendant et après la formation des orogènes en limite de plaque

Expression et âge de la déformation intraplaque au front d’un orogène : du Chevauchement Frontal Nord Pyrénéen à la bordure sud du Massif Central, France

In geodynamics, most of the deformation is accommodated at the edges of tectonic plates. However, the propagation of stress beyond these boundaries is at the origin of so-called "intraplate" deformations, which are of moderate intensity but control several processes, especially fluid circulations and mineralizations. These deformations, and in particular their link with the tectonic agenda established at the plate boundary, are still poorly understood today: are they anterior, coeval or posterior to the formation of the orogens? Are they single or multiple episodes, and over what duration? The work presented here aims to answer these questions by characterizing the intraplate domain located north of the Pyrenean Chain, in the Corbières, Languedoc and Grands Causses domains. The U-Pb geochronology on fault-related calcite, partly developed in the GEOPS laboratory during this work, is associated with a structural analysis of each domain in order to date its compressive deformation. The results obtained allow us to (1) clarify/establish the geodynamic timetables for each domain (2) place these intraplate deformations into the global geodynamic context and (3) establish the link between these deformations in the intraplate domain and those at the plate edges. Our results for the Corbières region, at the front of the orogen, reveal a phase of deformation during Lutetian times, offset from the paroxysm of exhumation in the chain at the Late Eocene. The region also records a miocene tectonic event coeval with the formation of the high elevation of low-relief surfaces of the Pyrenees and a deformation episode described on the Spanish side of the Pyrenees. The Languedoc area, and in particular the Cevennes Fault System, shows deformations associated with a continuous Pyrenean compression throughout the Eocene. In addition, U-Pb data indicate an albian activity of this fault system, coeval with the opening of the Pyrenean basins. Finally, the Grands Causses sector, corresponding to the study area farthest from the belt, shows a long and continuous deformation from the Lower Cretaceous to the Upper Eocene. All these results demonstrate that deformation in the intraplate domain is not limited to the paroxysmal phases of plate boundary deformation as previously proposed. Indeed, the intraplate domain presents a high sensitivity to plate edges deformation and thus, a strong deformability over important time periods, before, during and after the formation of plate boundary orogens.En géodynamique, l’essentiel des déformations est accommodé aux limites des plaques tectoniques. Pourtant, la propagation de la contrainte au-delà de ces frontières est à l’origine de déformations dites « intraplaques », d’intensité modérée mais qui contrôlent notamment des circulations de fluides et minéralisations. Ces déformations, et en particulier leur lien avec l’agenda tectonique établi en limite de plaque, sont aujourd’hui encore mal comprises : sont-elles antérieures, contemporaines, postérieures à la formation des orogènes ? S’agit-il d’épisodes uniques ou multiples, et sur quelle durée ? Les travaux présentés tentent de répondre à ces questions en s’appuyant sur la caractérisation du domaine intraplaque situé au Nord de la chaîne Pyrénéenne, dans la région des Corbières, du Languedoc et des Grands Causses. La méthode de datation U-Pb sur calcite de faille, développée en partie au laboratoire GEOPS au cours de ce travail, est couplée à une analyse structurale de chacune des zones afin de dater de manière absolue la déformation compressive dans les divers secteurs. Les résultats obtenus permettent ainsi de (1) préciser/établir les calendriers géodynamiques de chacun des secteurs (2) replacer ces déformations intraplaques dans le contexte géodynamique global et (3) établir le lien entre les déformations dans le domaine intraplaque et celles en bordure de plaque. Les travaux réalisés dans la région des Corbières, au front de l’orogène, mettent en évidence une phase de déformation au Lutétien, en décalage avec le paroxysme d’exhumation de la chaîne à l’Eocène supérieur. La région a également enregistré un évènement tectonique au Miocène, contemporain d’une phase d’exhumation de la chaîne, de la formation des surfaces « perchées » des Pyrénées et d’un épisode de déformation décrit sur le versant espagnol des Pyrénées. Le secteur du Languedoc, et en particulier le système de faille des Cévennes, enregistre une déformation associée à la compression pyrénéenne continue tout au long de l’Eocène. Par ailleurs les données U-Pb indiquent une activité à l’Albien de ce faisceau de failles, contemporaine de l’ouverture des bassins pyrénéens. Enfin, la région des Grands Causses correspondant au secteur d’étude le plus distal à la chaîne enregistre une déformation longue et continue du Crétacé inférieur à l’Eocène supérieur. L’ensemble de ces travaux démontre ainsi que la déformation en domaine intraplaque n’est pas limitée à l’enregistrement des phases paroxysmales de déformation en limite de plaque comme cela a pu être proposé auparavant, mais que le domaine intraplaque présente une grande sensibilité aux déformations en bordure de plaque, et donc une forte déformabilité sur des durées importantes avant, pendant et après la formation des orogènes en limite de plaque

Age of the Fontainebleau sandstones: a tectonic point of view

The age of the cementation of the Fontainebleau sandstones, located in the upper part of the Rupelian Fontainebleau Sand Formation and largely outcropping in the south of the center of the Paris Basin, remains a matter of debate: did the silicification occurred at early times during Miocene, following sedimentation, or did it occurred during Quaternary cold climate episodes? In this work, we determined an orthogonal fracture network (main directions N115° ±5° and N025° ±5°) over an area of ∼6000 km2. The fractures are oblique to the adjacent valley orientation and to the quarry working face orientation, discarding a gravitational origin. This tectonic fracturing is superimposed on regional scale antiforms and synforms that may be at least partly controlled by inherited basement faults reactivation during Alpine episodes. The whole Fontainebleau Sand Formation seems to be folded, including the Fontainebleau sandstones. We establish a relative chronology of the various phenomena and propose that silicification at the origin of the Fontainebleau quartzite occurred during early or middle Miocene. Alpine stresses then induced Fontainebleau sand and quartzite folding and fracturing during late Miocene and Pliocene. Finally, the fracture network facilitated fluid circulations and secondary carbonate sandstones or quartzite precipitation probably during Quaternary cold climate episodes

A new look at old debates about the Corbières (NE-Pyrenees) geology: salt tectonics and gravity gliding

In the Corbières area, a large-scale nappe has been identified at the beginning of the 20th century: the “Nappe des Corbières Orientales” (NCO) resting over a thick Triassic sole. This geological object is located at the NE of the Pyrenees, close to the Gulf of Lions. At this place, the chain changes in orientation from E-W to NE-SW and presents in detail, a great complexity. The existence of the nappe itself has never been contested. However, due to its overall complexity, several controversies exist regarding the style and chronology of deformation of its substratum in the so-called the “Pinède de Durban” in particular. We show that the new concepts of salt tectonics can clarify these old debates. Indeed, the rise of the Triassic salt during Mesozoic rifting episodes results in the development of characteristic sedimentary sequences (halokinetic sequences) on top of salt walls. It is along one of these, coinciding with the prolongation of the Cévenole Fault System, that the NCO has been individualized. During its Cenozoic emplacement, a gravity-gliding component, explaining the importance of the observed translation, could result from an uplift preceding the rifting at the origin of the Gulf of Lions

How sensitive are intraplate inherited structures? Insight from the Cévennes Fault System (Languedoc, SE France)

International audienceABSTRACT Deformation in intraplate domains is usually considered as a consequence of tectonic events at plate boundaries. Nevertheless, the occurrence of intraplate earthquakes such as the recent Le Teil event in the south of France along the Cévennes Fault System (CFS), on 11 November 2019, Mw = 4.9, questions whether this far-field deformation only occurs during tectonic pulses at plate boundaries, or if it corresponds to low-intensity but regional continuous deformation through time. To address this question, we have coupled U–Pb geochronology of fault-related calcites with structural analysis along a major fault system (the CFS) in the South-East Basin, France. We evidence (1) an Albian activity of the CFS and (2) a continuous compressional activity of the CFS and satellite structures during the whole Eocene and probably during the Late Cretaceous – Palaeocene, including periods (e.g. Lutetian) usually considered as phases of tectonic quiescence. We thus demonstrate that the tectonic reactivation of this intraplate fault system is not restricted to periods of high rates of deformation at plate boundaries

When did the Pyrenean shortening end? Insight from U–Pb geochronology of syn‐faulting calcite (Corbières area, France)

International audienceAbstract Absolute dating helps to define the age and duration of orogen building. Here we present new U–Pb ages of syn‐faulting calcites collected in the northern foreland basin of the Pyrenees. The studied area underwent deformation during the Eocene growth of the belt. This orogenic growth is considered to have persisted until the Late Oligocene, after which post‐orogenic processes prevailed. Microstructural analysis coupled with U–Pb dating of syn‐faulting calcite confirms the well‐known NW‐SE to N–S main shortening stage of the Pyrenean orogen during the Eocene (from 48.7 ± 2.2 to 43.2 ± 5.3 Ma). But our data further reveal NE‐SW shortening during the Miocene, ca . 16 Ma ago, that has never been seen in the northern Pyrenean foreland. We propose that this tectonic phase, now identified on both sides of the Pyrenean Belt, is a consequence of a stronger coupling between Africa, Iberia and Europe at this time

Et s'il existait une phase de raccourcissement « tardi – pyrénéenne » à la transition Burdigalien - Langhien ... ?

International audienc

Multistage genesis of the late Cretaceous manganese karst-hosted Tasdremt deposit (High Atlas, Morocco)

International audienceThe eastern part of the Souss Basin (Morocco) contains several Mn deposits in the Tasdremt district. ThreeMn orebodies occur within the Cenomanian-Turonian dolostones and the Senonian (Coniacian to Maastrichtian) detrital series, the main orebody being located at the boundary between them. The Mn ores consist of coronadite group minerals, mostly coronadite and hollandite, in a karstified dolostone. New field observations, petrographic analyses, and geochemical data define the Tasdremt deposits as a karst-hosted accumulation (11–60 wt.% Mn), particularly enriched in Ba (1.5–8.2 wt.%) and Pb (1.0–5.0 wt.%) with poor contaminations in Al, Fe, and P. This study shows that the ore-forming process is similar to that occurring in the Imini C3 level, located ~ 100 kmto the northeast. Such similarities with the high-grade pyrolusite-bearing ore suggest that the Tasdremt deposit is a lateral equivalent of the Imini deposits. However, the scarcity of pyrolusite in Tasdremt results in lower Mn grades, the Tasdremt ores being considered an aborted/incomplete system in comparison with the Imini deposits. 40Ar/39Ar geochronology of K-bearing Mn oxides yields late Cretaceous ages, defining three phases at ~ 91.5 Ma, ~ 77.5–82 Ma, and ~ 65–67 Ma. Although the source of metals remains hypothetical, mineralizing fluids were carried by O2-free groundwater that mixed with O2-rich shallow meteoric waters at the Tasdremt depositional site. The dissolution of the host dolostones and the karst environment have provided suitable conditions for the precipitation of Mnoxides, causing the coeval increase of pH and Eh, respectively. The Early Atlasic deformation during the Late Cretaceous is associated with mineralization events and was responsible for creation of low stand reliefs from Tasdremt to Imini. This period enabled karstification and mineralization. Connecting the Tasdremt deposits to other African Mn deposits is difficult since the latter consist of laterite resting above PaleoproterozoicMn protores, and consequently formed under different conditions from karst-hosted deposits. It is likely that other Mn occurrences formed along the Atlas belt in similar settings