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4. Numerical simulation of a class of models that combine several mechanisms of dissipation: fracture, plasticity, viscous dissipation

Author

Bonnetier, Eric, Jakabcin, Lukas, Labbé, Stéphane, and Replumaz, Anne

Subjects
Mathematics - Numerical Analysis
Abstract

We study a class of time evolution models that contain dissipation mech- anisms exhibited by geophysical materials during deformation: plasticity, viscous dissipation and fracture. We formally prove that they satisfy a Clausius-Duhem type inequality. We describe a semi-discrete time evolu- tion associated with these models, and report numerical 1D and 2D traction experiments, that illustrate that several dissipation regimes can indeed take place during the deformation. Finally, we report 2D numerical simulation of an experiment by Peltzer and Tapponnier, who studied the indentation of a layer of plasticine as an analogue model for geological materials.

Published
2014
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8. A systematic study of mantle drag effect on subduction dynamics and overriding plate deformation

Author

Thomas Geffroy, Guillaume Benjamin, Replumaz Anne, Simoes Martine, Lacassin Robin, Kermarrec Jean-Jacques, Habel Tania, Géosciences Rennes (GR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), Institut des Sciences de la Terre de Paris (iSTeP), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique du Globe de Paris (IPG Paris), Institut de Physique du Globe de Paris (IPGP (UMR_7154)), Institut national des sciences de l'Univers (INSU - CNRS)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), and European Geosciences Union

Subjects
[SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics
Abstract

International audience; Plates and the convective mantle interact with each other over geological time scales, leading to mantle flow, plate motion, and deformation along plate boundaries. At convergent boundaries undergoing subduction, the role played by mantle drag remains poorly understood despite its potential impact on subduction dynamics, and in turn on the deformation regime of the overriding plate. Previous studies were generally conducted in two dimensions, limiting their ability to faithfully reproduce processes taking place on Earth. Instead, in this study, we present 11 three-dimensional analog models of subduction at the scale of the upper mantle, including an overriding plate, and in which we control mantle drag at the base of the lower or upper plate by imposing a controlled unidirectional background mantle flow perpendicular to the trench. We systematically vary the velocity and the direction of the imposed horizontal mantle flow and quantify its impact on horizontal and vertical upper plate deformations, plate and subduction velocities, and the geometry of the slab. The geometry of the slab is only marginally affected by the velocity and direction of the mantle flow. In the absence of mantle flow, slab rolls back and deformation is accommodated by trench-orthogonal stretching in the upper plate. Instead, the addition of a background flow dragging the lower or upper plate toward the trench systematically results either in the absence of upper plate deformation, or in trench-orthogonal shortening with strain rates that increase linearly with increasing mantle flow. We show that the upper plate strain rate is primarily controlled by the velocity of the free plate in the model, which itself results from the drag exerted by the mantle at the base of the plate. Coupling between mantle and plate is larger for models with flow directed toward the upper plate, resulting in strain rates that are about three times larger than for equivalent models with flow directed toward the lower plate. This systematic study provides a better understanding of the effect of mantle drag on plate displacements and deformation along subduction zones, leading to a better understanding of the ingredients required to form Andean-type mountain ranges.

Published
2023

12. Unravelling granulitic conditions in Early Triassic crustal xenoliths from NE-Qiangtang, Tibet

Author

Goussin, Fanny, Cordier, Carole, Oliot, Emilien, Guillot, Stephane, Poujol, Marc, Replumaz, Anne, Dupont-Nivet, Guillaume, Institut des Sciences de la Terre (ISTerre), Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Gustave Eiffel-Université Grenoble Alpes (UGA), Géosciences Montpellier, Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Université des Antilles (UA)-Centre National de la Recherche Scientifique (CNRS), Géosciences Rennes (GR), Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES), University of Potsdam, Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles (UA), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), University of Potsdam = Universität Potsdam, Sciencesconf.org, CCSD, and SGF, CNRS, Laboratoire de Géologie de Lyon ou l’étude de la Terre, des planètes et de l’environnement

Subjects
[SDU] Sciences of the Universe [physics], ICPMS U, corundum, [SDU]Sciences of the Universe [physics], [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, crustal xenolith, granulite, LA-ICPMS U-Pb zircon, Pb zircon, Tibetan Plateau, pseudomorph, LA, ComputingMilieux_MISCELLANEOUS
Abstract

National audience; Unlike most "wedge" orogens, the structure and the composition of theTibetan Plateau lower crust has kept being largely inaccessible otherwisethan by geophysical studies and by the few scattered sampling ofxenoliths brought to the surface by volcanism. In the Nangqian basin (NEQiangtangterrane), Eocene syn-contractional potassic lavas carrypartially molten foliated quartzo-feldspathic xenoliths. Zircon LA-ICPMSU-Pb dating of these crustal xenoliths yields a Lower Triassic age of ca.248.5 Ma, which is interpreted as the protolith crystallization age, withno evidence for any metamorphic zircon growth or resetting. The rarerelict ferro-magnesian minerals found (clinopyroxene, amphibole,phlogopite, garnet) are in textural and chemical disequilibrium, makingconventional thermobarometry methods inoperable. Nevertheless, thexenoliths have retained unusual metamorphic features which can helpunravelling their pre-entrapment metamorphic history. Pure anorthite"patches" with magnetite inclusions are interpreted as pseudomorphsafter garnet. Since these patches are often found in contact withclinopyroxene and rutile, these minerals may together represent a formerhigh-pressure assemblage that developed at 1.2-1.5 GPa and 620-730°C.Such pressure record would indicate that 80% of the present-day crustalthickness of the Tibetan Plateau was already acquired in Eocene times.Moreover, corundum-bearing assemblages, interpreted as pseudomorphsafter phlogopite, are best explained by kinetic disequilibrium underhigh-temperature granulitic conditions, suggesting a short-livedmetamorphic event. Taken together, this set of new petrological andgeochronological data suggests that crustal granulitic metamorphism maynot b e related to the onset of a general warming of the Tibetan crustsustained until the present, but rather to the punctual injection of mantlederivedmelts in the crust before Eocene eruption.

Published
2021

13. Strain partitioning estimation in the eastern part of the tibetan plateau from block models constrained by GPS measurements and automated FLATSIM time series analysis of Sentinel-1 InSAR data

Author

Lemrabet, Laëtitia, Lasserre, Cecile, Doin, Marie-Pierre, Métois, Marianne, Replumaz, Anne, Leloup, Philippe-Hervé, Jianbao, Sun, Chevalier, Marie-Luce, Université Claude Bernard Lyon 1 (UCBL), Université de Lyon, Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Institut des Sciences de la Terre (ISTerre), Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Gustave Eiffel-Université Grenoble Alpes (UGA), and SGF, CNRS, Laboratoire de Géologie de Lyon ou l’étude de la Terre, des planètes et de l’environnement

Subjects
Tibetan Plateau, InSAR, Seismic cycle, [SDU]Sciences of the Universe [physics], GPS, time series analysis, FLATSIM, Sentinel 1, block models
Abstract

International audience; The use of high spatial and temporal resolution data is a key condition for characterizinginterseismic deformation along major faults and understanding their roles in accommodatingthe deformation. Here we present an analysis using 4 years of Sentinel-1 InSAR data tocharacterize interseismic deformation along the Xianshuihe (XSH) fault system and theKunlun (KUN) fault in the eastern edge of the Tibetan plateau.Thanks to the NSBAS automated processing chain (Doin et al., 2011, Grandin, 2015),implemented at the CNES high-performance computing center in Toulouse as part of theFLATSIM project (ForM@Ter LArge-scale multi-Temporal Sentinel-1 Interferometryprocessing chain in Muscate), we automatically perform high-resolution time series analysisof 2014-2019 Sentinel-1 InSAR data set, acquired along 1200 km-long ascending anddescending orbits, over the study area. According to an elastic block model approach, InSARtimes series are combined to the latest published GPS velocity field and inverted using theblock modeling software TDEFNODE (McCaffrey., 2009) to model fault slip rates andcoupling distribution along these two major strike-slip faults and identify asperities andpotential creeping areas as well as analyze internal block deformation.Our models suggest the existence of a fault connecting the XSH fault and the KUN fault andaccomodating part of the deformation at a constant slip rate of 10 mm/yr. It shows that theslip rate on the XSH fault system increases from west to east, from 5 mm/yr to 14 mm/yrbetween latitudes 34.3°N and 29.3°N, while the slip rate on the Kunlun fault slightlydecreases from west to east from 10 mm/yr to 9 mm/yr. The slip deficit rate observed alongthe XSH fault system shows strong lateral variations, that we analyze with respect to theseismic history of the fault, and suggests the presence of shallow creep on the eastern part ofthe fault. The slip deficit rate observed along the Kunlun fault appears more homogeneous.However, we observe a strong deformation gradient that we interpret as a post-seismic signalat the eastern tip of the rupture of the 2001 Kokoxili earthquake and we analyze its temporalevolution.

Published
2021

17. Combining thermo-kinematic and mechanical modelling on thrust faults - a quantitative approach to crustal deformation history: Case study from SE Tibet

Author

Pitard, Paul, Replumaz, Anne, Doin, Marie-Pierre, Thieulot, Cedric, Chevalier, Marie-Luce, Leloup, Philippe-Hervé, Bai, Mingkun, Balvay, Mélanie, Haibing, Li, Sciencesconf.org, CCSD, Institut des Sciences de la Terre (ISTerre), Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Gustave Eiffel-Université Grenoble Alpes (UGA), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), and SGF, CNRS, Laboratoire de Géologie de Lyon ou l’étude de la Terre, des planètes et de l’environnement

Subjects
[SDU] Sciences of the Universe [physics], kinematic modelling, [SDU]Sciences of the Universe [physics], Formation Tibet, Tibetan Plateau, Crustal structure of Tibet, Muli thrust, Thermochronology, Thermo, Mechanical modelling, ComputingMilieux_MISCELLANEOUS, Yalong thrust belt
Abstract

International audience

Published
2021

18. Combining thermo-kinematic and mechanical modelling on thrust faults - a quantitative approach to crustal deformation history: Case study from SE Tibet

Author

Pitard, Paul, primary, Replumaz, Anne, additional, Doin, Marie-Pierre, additional, Thieulot, Cédric, additional, Chevalier, Marie-Luce, additional, Leloup, Philippe Hervé, additional, de Sigoyer, Julia, additional, Bai, Mingkun, additional, Haibing, Li, additional, and Balvay, Mélanie, additional

Published
2021
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24. Decoupling between upper crustal deformation of southern Tibet and underthrusting of Indian lithosphere.

Author

Wang, Shiguang, Replumaz, Anne, Chevalier, Marie‐Luce, and Li, Haibing

Subjects
*LITHOSPHERE, *FAULT zones, *RIFTS (Geology), *TOMOGRAPHY
Abstract

More accurate normal fault mapping and more recently constrained extension rates in southern and central Tibet allow to better discuss the mechanical processes responsible for the distribution of extension in Tibet. First, we show that the location of the rifts in southern Tibet south of the Karakorum‐Jiali fault zone (KJFZ) does not exactly correspond to that of the rigid Indian lower lithosphere flattening below southern Tibet (underthrusting) inferred by P‐waves global tomography, thus suggesting an absence of mechanical coupling between the two processes. Instead, E‐W extension south of the KJFZ appears primarily due to divergent, orthogonal thrusting along the curved Himalayan arc, as proposed earlier. North of the KJFZ however, lower amplitude extension, distributed on numerous scattered normal faults in the western Qiangtang terrane, absorbs distributed eastward extrusion, while eastern Qiangtang is extruded more rigidly by the Xianshuihe fault, following a slip‐line resulting from in‐plane forces due to the collision/indenter, visible as a major discontinuity in the GPS velocity field. [ABSTRACT FROM AUTHOR]

Published
2022
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28. Carbonated Inheritance in the Eastern Tibetan Lithospheric Mantle: Petrological Evidences and Geodynamic Implications

Author

Goussin, Fanny, primary, Riel, Nicolas, additional, Cordier, Carole, additional, Guillot, Stéphane, additional, Boulvais, Philippe, additional, Roperch, Pierrick, additional, Replumaz, Anne, additional, Schulmann, Karel, additional, Dupont‐Nivet, Guillaume, additional, Rosas, Filipe, additional, and Guo, Zhaojie, additional

Published
2020
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29. Tectonic Control on Rapid Late Miocene—Quaternary Incision of the Mekong River Knickzone, Southeast Tibetan Plateau

Author

Replumaz, Anne, primary, San José, Malwina, additional, Margirier, Audrey, additional, van der Beek, Peter, additional, Gautheron, Cécile, additional, Leloup, Philippe Hervé, additional, Ou, Xiong, additional, Kai, Cao, additional, Wang, Guo‐Can, additional, Zhang, Yuan‐Ze, additional, Valla, Pierre G., additional, and Balvay, Mélanie, additional

Published
2020
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30. Spatial Slip Rate Distribution Along the SE Xianshuihe Fault, Eastern Tibet, and Earthquake Hazard Assessment.

Author

Mingkun Bai, Chevalier, Marie-Luce, Hervé Leloup, Philippe, Haibing Li, Jiawei Pan, Replumaz, Anne, Shiguang Wang, Kaiyu Li, Qiong Wu, Fucai Liu, and Jinjiang Zhang

Abstract

The Xianshuihe (XSH) fault in eastern Tibet is one of the most active faults in China, with the next large earthquake most likely to occur along its SE part, where the fault splits into three parallel branches: Yalahe, Selaha and Zheduotang (ZDT). Precisely quantifying their slip rates at various timescales is essential to evaluate regional earthquake hazard. Here, we expand our previous work on the Selaha fault to the nearby ZDT and Moxi (MX) faults, and add observations on the Yalahe fault and on the newly discovered Mugecuo South fault zone. Using tectonic-geomorphology approaches with 10Be dating, we had previously determined average late Quaternary slip rates of 9.75 ± 0.15 and 4.4 ± 0.5 mm/yr along the NW and SE Selaha fault, respectively. Using the same methods here, we determine a slip rate of 3.4-4.8 mm/yr on the ZDT fault and of 9.6--13.4 mm/yr on the MX fault. This is consistent with the southeastward slip rate increase we had proposed along the XSH fault system from 6-8 mm/yr (Ganzi fault) to ~10 mm/yr (Selaha fault), and >9.6 mm/yr (MX fault). We propose a new model for the SE XSH fault, where the large-scale Mugecuo pull-apart basin lies within an even larger scale compressive uplift zone in a restraining bend of the XSH fault, where the highest peak in eastern Tibet is located (Gongga Shan, 7,556 m). Our slip rate determination helps to constrain a relatively high regional Mw ~7 earthquake hazard at present on the SE XSH fault. [ABSTRACT FROM AUTHOR]

Published
2021
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31. Hairpin loops and slip-sense inversion on southeast Asian strike-slip faults

Author

Lacassin, Robin, Replumaz, Anne, and Leloup, P. Herve

Subjects
Golden Triangle (Southeast Asia) -- Natural history, Strike-slip faults (Geology) -- Analysis, Geology, Stratigraphic -- Cenozoic, Earth sciences
Abstract

In the Golden Triangle region of southeast Asia (northern Thailand, Laos and Burma, southern Yunnan), the Mekong, Salween, and neighboring rivers show hairpin geometries where they cross active strike-slip faults. Restoration of young, left-lateral offsets of these rivers leaves residual right-lateral bends of many kilometers. We interpret these hairpins as evidence of late Cenozoic slip-sense inversion on these faults, about 5 to 20 Ma. Near the Red River fault, stress field and slip-sense inversion occurred ca. 5 Ma. This implies that the present course of these large rivers has existed for at least several million years. Pliocene-Quaternary slip rates, possibly on the order of 1 mm/yr, are inferred on each of the strike-slip faults of the Golden Triangle.

Published
1998

33. Collisional subduction: how it works

Author

Pitard, Paul, Replumaz, Anne, Funiciello, Francesca, Husson, Laurent, Faccenna, Claudio, Institut des Sciences de la Terre (ISTerre), Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Laboratory of Experimental Tectonics, Università degli Studi Roma Tre, and Università degli Studi Roma Tre = Roma Tre University (ROMA TRE)

Subjects
[SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, [SDU]Sciences of the Universe [physics], [SDU.STU]Sciences of the Universe [physics]/Earth Sciences
Abstract

International audience; Since several decades, the processes allowing for the subduction of the continental lithosphere less dense than the mantle in a collision context have been widely explored, but models that are based upon the premise that slab pull is the prominent driver of plate tectonics fail. The India–Asia collision, where several episodes of continental subduction have been documented, constitute a case study for alternative views. One of these episodes occurred in the early collision time within the Asian plate where continental lithosphere not attached to any oceanic lithosphere subducted southward in front of the Indian lithosphere during its northward subduction that followed the oceanic subduction of the Tethys ocean. This process, known as collisional subduction, has a counter-intuitive behavior since the subduction is not driven by slab pull. It has been speculated that the mantle circulation can play an important role in triggering collisional subduction but a detailed, qualitative analysis of it is not available, yet. In this work we explore the southward subduction dynamics of the Asian lithosphere below Tibet by means of analogue experiments with the aim to highlight how the mantle circulation induces or responds to collisional subduction. We found that during the northward oceanic subduction (analogue of Tethys subduction) attached to the indenter (Indian analogue), the main component of slab motion is driven vertically by its negative buoyancy, while the trench rolls back. In the mantle the convective pattern consists in a pair of wide convective cells on both sides of the slab. But when the indenter starts to bend and plunge in the mantle, trench motion reverses. Its advance transmits the far field forces to two upper plates (Asian analogues). The more viscous frontal plate thickens, and the less viscous hinterland plate, which is attached to the back wall of the box, subducts. During this transition, a pair of sub-lithospheric convective cells is observed on both sides of the Asian analogue slab, driven by the shortening of the frontal plate. It favors the initiation of the backwall plate subduction. Such subduction is maintained during the entire collision by a wide cell with a mostly horizontal mantle flow below Tibet, passively advecting the Asian analogue slab. Experimental results suggest that once the tectonic far-field force related to the forward horizontal motion becomes dominant upon the buoyancy forces, trench advancing and the transmission of the tectonic force to the upper and backwall plates are promoted. This peculiar condition triggers the subduction of the backwall plate, despite it is light and buoyant.

Published
2018

39. Long‐term exhumation history of the Gangdese magmatic arc: Implications for the evolution of the Kailas Basin, western Tibet.

Author

Shen, Tianyi, Wang, Guocan, Bernet, Matthias, Replumaz, Anne, Ai, Keke, Song, Bowen, Zhang, Kexin, Zhang, Pan, and Hu, J.

Subjects
TECTONIC exhumation, SEDIMENTATION & deposition, TOPOGRAPHY, ZIRCON, LAND subsidence
Abstract

Constraining the long‐term exhumation history of the Gangdese magmatic arc is critical for understanding the coupled evolution of orogenic exhumation and accumulation of basin sediments on the southern Tibetan Plateau. We present new zircon fission‐track (ZFT) data from sandstones in the Mt. Kailas area, western Tibet, to decipher the relation between source rock exhumation and sediment deposition in the basin. Two sedimentary members were recognized in the Kailas Basin which are the Eocene conglomerates in the hanging wall of the Great Counter Thrust and the Oligocene–Miocene Kailas Formation in the footwall. The Eocene conglomerates were mostly derived from the Lhasa Terrane to the north with recycling of pre‐Cenozoic sediments, containing zircons that experienced post‐magmatic cooling after the Indian–Asian collision and buried deeply later by the Oligocene–Miocene Kailas Formation. The ZFT analysis from the Kailas Formation illustrates significant cooling during the Oligocene (ca. 32 Ma) in the source region, indicating that the Gangdese magmatic arc rocks were eroded rapidly during that time. The alternate increasing and decreasing of the southernmost Gangdese magmatic arc progresses are linked to dynamic topography deflection induced by the northward subduction of the Indian Plate since the Oligocene and subsequent southward overturning of the Indian mantle slab. Basin subsidence and formation of the Kailas Formation seems also be driven by dynamic topography since the Oligocene. [ABSTRACT FROM AUTHOR]

Published
2020
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40. Xenoliths in Eocene lavas from Central Tibet record carbonatedmetasomatism of the lithosphere

Author

Goussin, Fanny, Cordier, Carole, Boulvais, Philippe, Guillot, Stéphanie, Roperch, Pierrick, Replumaz, Anne, Institut des Sciences de la Terre (ISTerre), Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Géosciences Rennes (GR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Centre National de la Recherche Scientifique (CNRS), European Geosciences Union, Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), and Dubigeon, Isabelle

Subjects
[SDU.STU] Sciences of the Universe [physics]/Earth Sciences, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, ComputingMilieux_MISCELLANEOUS
Abstract

International audience; no abstract

Published
2017

41. Wet tropical climate in SE Tibet during the Late Eocene

Author

Sorrel, Philippe, Eymard, Ines, Leloup, Philippe-Herve, Maheo, Gweltaz, Olivier, Nicolas, Sterb, Mary, Gourbet, Loraine, Wang, Guocan, Jing, Wu, Lu, Haijian, Li, Haibing, Yadong, Xu, Zhang, Kexin, Cao, Kai, Chevalier, Marie-Luce, Replumaz, Anne, Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement [Lyon] (LGL-TPE), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon)

Subjects
[SDU]Sciences of the Universe [physics], Science, ddc:550, Medicine, Article
Abstract

International audience; Cenozoic climate cooling at the advent of the Eocene-Oligocene transition (EOT), similar to 33.7 Ma ago, was stamped in the ocean by a series of climatic events albeit the impact of this global climatic transition on terrestrial environments is still fragmentary. Yet archival constraints on Late Eocene atmospheric circulation are scarce in (tropical) monsoonal Asia, and the paucity of terrestrial records hampers a meaningful comparison of the long- term climatic trends between oceanic and continental realms. Here we report new sedimentological data from the Jianchuan basin (SE Tibet) arguing for wetter climatic conditions in monsoonal Asia at similar to 35.5 Ma almost coevally to the aridification recognized northwards in the Xining basin. We show that the occurrence of flash-flood events in semi-arid to sub-humid palustrine-sublacustrine settings preceded the development of coal-bearing deposits in swampylike environments, thus paving the way to a more humid climate in SE Tibet ahead from the EOT. We suggest that this moisture redistribution possibly reflects more northern and intensified ITCZ-induced tropical rainfall in monsoonal Asia around 35.5 Ma, in accordance with recent sea-surface temperature reconstructions from equatorial oceanic records. Our findings thus highlight an important period of climatic upheaval in terrestrial Asian environments similar to 2-4 millions years prior to the EOT.

Published
2017

42. Contrasting exhumation histories and relief development within the Three Rivers Region (Southeast Tibet).

Author

Xiong Ou, Replumaz, Anne, and van der BeekInstitute of Geosciences, Potsdam University,Potsdam, 14476, Germany;vanderbeek@uni-potsdam.de, Peter

Subjects
*TECTONIC exhumation, *SOUND recordings, *NEOGENE Period
Abstract

The Three Rivers Region in Southeast Tibet represents a transition between the strongly deformed zone around Eastern Himalayan Syntaxis and the less deformed southeast Tibetan plateau margin in Yunnan and Sichuan. In this study, we compile and model published thermochronologic ages for two massifs facing each other across the Mekong River in the core of the Three Rivers Region, by using the thermo-kinematic code Pecube to constrain their exhumation and relief development history. Modelling results for the low-relief, mean-elevation BaimaXueshan massif, east of the Mekong River, suggest regional rock uplift at a rate of 0.25 km/Myr since ~ 10 Ma, following slow exhumation at a rate of 0.01 km/Myr since at least 22 Ma. River incision accounts for only 15 % of the total exhumation in the BaimaXueshan. Exhumation since ~ 10 Ma is significantly higher (2.5 km) than that estimated (~ 0.23 km) for the most emblematic low-relief or relict surfaces of Eastern Tibet, which are characterized by apatite (U-Th)/He ages older than the collision age (> 50 Ma). We conclude that the BaimaXueshan massif, which shows younger ages (< 50 Ma) that record significant rock uplift and exhumation during the Neogene, cannot be classified as a relict surface despite its low relief. Modelling results for the high-relief, high-elevation Kawagebo massif, to the west of the Mekong, imply a similar contribution of Mekong River incision (20 %) to exhumation, but much stronger local rock uplift at a rate of 0.45 km/Myr since at least 10 Ma, accelerating to 1.86 km/Myr since 1.6 Ma. We show that the age-elevation profiles for three thermochronometers are best modeled by rock uplift on a kinked westward-dipping thrust striking roughly parallel to the Mekong River, with a steep shallow segment flattening out at depth. Thus, the strong differences in elevation and relief that characterize these massifs are linked to variable exhumation histories due to a strongly differing tectonic imprint. [ABSTRACT FROM AUTHOR]

Published
2020
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45. Paleomagnetic constraints on the tectonicsof the Eastern border of the Qiangtangterrane (Tibetan Plateau) during theIndia-Asia collision

Author

Roperch, Pierrick, Dupont-Nivet, Guillaume, Guillot, Stéphane, Goussin, Fanny, Replumaz, Anne, Huang, Wentao, Zhang, Yang, Wacquier, Loris, Géosciences Rennes (GR), Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES), Institut des Sciences de la Terre (ISTerre), Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Department of Geosciences [Tucson], University of Arizona, Société Géologique de France, Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Centre National de la Recherche Scientifique (CNRS), Dubigeon, Isabelle, Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), and Department of Geosciences [University of Arizona]

Subjects
[SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], [SDU.STU.TE] Sciences of the Universe [physics]/Earth Sciences/Tectonics, tectonics, paleomagnetism, [SDU.STU.GP] Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], Tibet
Abstract

National audience; Paleomagnetism should be a useful tool to estimate northsouthconvergence across the Himalaya and Tibetan Plateau. Unfortunatelythe large negative inclination anomaly for most of theCenozoic rocks has been the subject of numerous controversies(non dipolar geomagnetic fields, inclination flattening in sedimentsor large scale continental deformation of Eurasia). We presentnew paleomagnetic results from two Cenozoic basins of the Easternpart of the Qiangtang terrane characterized by two short-livedvolcanic fields at ~37-38 Ma (Nangqian area) and 49-51 Ma (Xialaxiuarea). In the Nangqian basin, sites have been collected inred beds sediments, sills and dikes intruding the red beds and inextrusive volcanic rocks mainly found on top of the sedimentarysequence. A well-defined secondary component of magnetizationwith normal polarity was recovered in the red beds in the temperaturerange ~150-600C. 24 out of 25 sites in magmatic rocks,have a primary magnetization of normal polarity. The remagnetizationin the red beds is thus clearly related to the volcanic event.The paleomagnetic data confirm previous field interpretations indicatingthat volcanic activity occurred at the end of a phase ofdeformation in the syntectonic Nangqian basin. There is no inclinationanomaly in the mean paleomagnetic result (D=18.0,I=50.1 a95 =7.9) from 25 sites in volcanic rocks when comparedto the Eurasian reference pole. This paleomagnetic resultis confirmed by the remagnetization in red beds.In the Xialaxiu area, we sampled the volcanic field and red bedsfilling a basin 10 to 20 km farther north. Results from the red bedsconfirm the result (D=322.0, I=32.3, a95=9.5) previously obtainedat this location by Cogné et al. (1999). However, the meandirection from 21 sites in volcanic rocks is different (D=11.9,I=41.6, a95=8.0) from that in the red beds suggesting differentage of magnetization.In conclusion, the mean inclination in ~50 Ma volcanics at Xialaxiuis similar to that obtained by Dupont-Nivet et al. (2010) for theLhasa terrane at the same age suggesting about 1100 km ± 500N-S convergence with stable Eurasia. However, our results fromthe ~37 Ma Nangqian rocks yield a higher mean inclination implyinga paleolatitude similar to expected for Eurasia at this time.This suggests that significant N-S convergence detectable by paleomagnetismdid not occur north of the Qiangtang terrane after37 Ma. Taken at face values, our results rather suggest that mostof the ~1000 km convergence occurred north of the Qiangtangterrane before 37 Ma but we cannot exclude that this potentialinclination anomaly affected both ~50 Ma Qiangtang and Lhasaterrane results. Finally, despite most regional structures beingNW-SE oriented, there is no evidence for consistent clockwise rotationsas expected with a model of deformation implying a largecomponent of extrusion or dextral shear along the eastern marginof the Tibetan Plateau.

Published
2016

46. Nature and melting processes of the lithosphere beneath the North-East Qiangqtang terrane, Central Tibet, during Eocene times

Author

Goussin, Fanny, Guillot, Stéphane, Schulmann, Karel, Cordier, Carole, Oliot, Emilien, Replumaz, Anne, Roperch, Pierrick, Dupont-Nivet, Guillaume, Institut des Sciences de la Terre (ISTerre), Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Dynamique de la lithosphère et des bassins sédimentaires (IPGS) (IPGS-Dylbas), Institut de physique du globe de Strasbourg (IPGS), Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Géosciences Montpellier, Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Université des Antilles (UA)-Centre National de la Recherche Scientifique (CNRS), Géosciences Rennes (GR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Centre National de la Recherche Scientifique (CNRS), European Geosciences Union, Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles (UA), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), and Dubigeon, Isabelle

Subjects
[SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], [SDU.STU.GP] Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph]
Abstract

International audience; At the time of the collision with India (55Ma), the southern margin of Asia was a composite continental domainresulting from an already long history of successive accretions of different terranes having different rheologies.Knowledge about the structure, composition and thermal state of the Tibetan lithosphere through time is thusfundamental to understand the respective contributions of pre-Cenozoïc and Cenozoïc tectonics in the building ofthe Plateau to its present-day elevations.We focused on the boundary between the Qiangtang terrane to the south, and the Songpan-Ganze terrane to thenorth.We jointly studied deep crustal xenoliths and associated (ultra-)potassic magmatism from the Eocene basinsof Nangqian and Xialaxiu (Qinghai Province, China), north of the Qiangtang terrane. The aims were to retrievethe composition and the thermal state of the lower crust during Eocene times, to study the behavior of the lowercrust and lithospheric mantle of the Eastern Qiangtang terrane and the adjacent Songpan-Ganze terrane at the timeof the collision, and the link with the magmatic activity.Crustal xenoliths are of two types: biotite-rich, amphibole bearing metasediments; and garnet-bearing quartzofeldspathicgneisses. Such assemblages are typical of very high-grade amphibolite and granulite faciesmetamorphism; further study should allow us to quantify the pressures and temperatures those rocks experienceduntil the time they were sampled by their host lavas.Major element geochemistry places the c.a. 51-49 Ma (Spurlin et al., 2005) Xialaxiu volcanic field in a fairlydifferentiated (SiO265-70 wt%) high-K field of the calc-alcaline series. Trace element analysis suggests a strongcrustal contamination of the primary mantellic melts. C.a. 38-37 Ma (Spurlin et al., 2005) Nangqian magmaticbodies span across the alkaline series, with high to extreme (K2O6wt%) values. Complex major and traceelement patterns, coupled with high-resolution microprobe data on pyroxene xenocrysts, suggest that enrichmentoccurred at the source by metasomatism of the lithospheric mantle.Further work will precise which mechanisms could have accounted for such a metasomatism of the mantle beneaththe Northern Qiangtang terrane during Eocene, and whether the lower crust had an autochtonous or allochtonousnature.

Published
2016

47. Linking the P-T evolution of granulites andthe geochemistry of ultra-K volcanics fromBohemian Massif and Central Tibet

Author

Guillot, Stéphane, Goussin, Fanny, Maierova, Petra, Cordier, Carole, Schulmann, Karel, Roperch, Pierrick, Dupont-Nivet, Guillaume, Replumaz, Anne, Dubigeon, Isabelle, Institut des Sciences de la Terre (ISTerre), Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Dynamique de la lithosphère et des bassins sédimentaires (IPGS) (IPGS-Dylbas), Institut de physique du globe de Strasbourg (IPGS), Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Géosciences Rennes (GR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), Société Géologique de France, Université de Rennes 1 (UR1), and Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, volcanism, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, [SDU.STU.GC] Sciences of the Universe [physics]/Earth Sciences/Geochemistry, [SDU.STU.TE] Sciences of the Universe [physics]/Earth Sciences/Tectonics, thickening, granulites, Boehmia, Tibet
Abstract

National audience; Variscan orogeny is traditionally compared to Himalayan-Tibetan orogeny thanks to two main reasons: 1) Variscan orogenoriginated through progressive amalgamation of Gondwanaderived blocks which formed belt that was subsequently squeezedbetween two continental plates - Laurussia and Gondwana. Similarsequence of events is characteristic for Tibetan-Himalayan orogenyas well, where previously Gondwana accreted blocks were squeezedbetween Asian continent and India. Therefore, both orogens resultfrom similar reorganization of plates in Paleozoic and Mesozoic-Cenozoic times, which initiated rapid northward drift of Gondwanaderived blocks and their final collision with northern continentalmasses. 2) This process resulted in both cases in formation orogenicroot of double-crust thickness characterized by long lasting(HP) granulite facies metamorphism in lower crust followed byisothermal decompression still at granulite facies conditions. Inaddition, the granulites in central Tibet were transported by highpotassium lavas, with geochemical and isotopical signature correspondingto Mg-K granitoids typically associated to HP granulitesin the eastern part of the Variscan belt (the Bohemian Massif inparticular). In both cases, the origin of granulitic lower crust andassociated high potassium lavas are attributed to relamination andthermal maturation of lower crustal allochthon underthrust belowupper plate crust during collision. Based on above similaritieswe argue that the Devonian - Carboniferous evolution of the BohemianMassif may be a proxy of Eocene to recent crustal dynamicsof the Tibetan system. To better quantify similarities betweenboth orogens, we present a set of numerical models which reproducethe tectonic multistage scenario proposed for the Variscantectonics of Bohemian Massif. These models are subsequentlycompared with P-T data acquired from the Himalaya and southernTibetangranulites and xenoliths from central Tibet.

Published
2016

49. Reappraisal of the Jianchuan Cenozoic basin stratigraphy and its implications on the SE Tibetan plateau evolution

Author

Gourbet, Loraine, primary, Leloup, Philippe Hervé, additional, Paquette, Jean-Louis, additional, Sorrel, Philippe, additional, Maheo, Gweltaz, additional, Wang, GuoCan, additional, Yadong, Xu, additional, Cao, Kai, additional, Antoine, Pierre-Olivier, additional, Eymard, Inès, additional, Liu, Wei, additional, Lu, Haijian, additional, Replumaz, Anne, additional, Chevalier, Marie-Luce, additional, Kexin, Zhang, additional, Jing, Wu, additional, and Shen, Tianyi, additional

Published
2017
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50. Microseismicity of the Béarn range: reactivation of inversion and collision structures at the northern edge of the Iberian plate

Author

Dumont, Thierry, Replumaz, Anne, Rouméjon, Stéphane, Briais, Anne, Rigo, Alexis, Bouillin, Jean-Pierre, Institut des Sciences de la Terre (ISTerre), Université Joseph Fourier - Grenoble 1 (UJF)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-PRES Université de Grenoble-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Institut de Physique du Globe de Paris (IPGP), Centre National de la Recherche Scientifique (CNRS)-Université de La Réunion (UR)-Université Paris Diderot - Paris 7 (UPD7)-IPG PARIS-Institut national des sciences de l'Univers (INSU - CNRS), Géosciences Environnement Toulouse (GET), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), Laboratoire de géologie de l'ENS (LGENS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Centre National d'Études Spatiales [Toulouse] (CNES), Laboratoire de géologie de l'ENS (LGE), and École normale supérieure - Paris (ENS Paris)-École normale supérieure - Paris (ENS Paris)

Subjects
structural inversion, Microseimicity, Iberian plate margin, Western Pyrenees, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, deformation history, extensional reactivation
Abstract

International audience; The Béarn range, located to the north of the Axial Zone in the Western Pyrenees, is affected by numerous small magnitude seismic events. These events overlap an area characterised by specific geological structures which are interpreted to have resulted from multistage extensional and compressional deformation. An analysis of surface geology draped over DEM, together with field investigations, allow identification of two main shortening episodes with differing direction of contraction: D1 represents the inversion of the North-Pyrenean basin, whose Mesozoic infill was detached from highly extended crust and transported southwards over the necking zone and the northern margin of the Iberian plate; D2 corresponds to the collision stage, and is characterised in the study area by backfolding and backthrusting deformation coeval with uplift in the axial part of the chain due to thickening of the Iberian plate. The microseismicity appears to concentrate along the basal part of the inverted basin units (D1) where this initially low-angle thrust has been tilted and steepened during collision (D2). We propose that local steepening of this ancient inversion structure, which should not be named "North Pyrenean fault", provided the suitable dip for extensional solicitation in association with the present uplift of the Axial Zone, whatever the driving mechanism of this uplift could be.

Published
2015

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