Author: "Géosciences Rennes (GR)" / Publisher: american geophysical union (agu) - Searchworks@Jio Institute Digital Library Search Results

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28 results on '"Géosciences Rennes (GR)"'

1. Core Complex Segmentation in North Aegean, A Dynamic View

Author: Brun, Jean Pierre, Sokoutis, Dimitrios, Tectonics, 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 ), Department of Geosciences [Oslo], University of Oslo ( UiO ), Tectonics, Faculty of Mathematics and Natural Sciences [Oslo], University of Oslo (UiO)-University of Oslo (UiO), Institut Universitaire de France, The Netherlands Centre for Integrated Solid Earth Science, Géosciences Rennes (GR), 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: Aegean back-arc extension, 010504 meteorology & atmospheric sciences, North Anatolian Fault, Structural basin, 010502 geochemistry & geophysics, Neogene, 01 natural sciences, Paleontology, Geochemistry and Petrology, metamorphic core complex, 14. Life underwater, Clockwise, 0105 earth and related environmental sciences, [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, geography, geography.geographical_feature_category, Rift, Rhodope, Metamorphic core complex, wide rifting, [ SDU.STU.TE ] Sciences of the Universe [physics]/Earth Sciences/Tectonics, Sedimentary basin, Geophysics, Slab, acceleration of subduction rollback, Geology
Abstract: International audience; The core complexes of the North Aegean result from the gravity spreading of a thrust wedge, driven by the Hellenic slab rollback, since middle Eocene. The development of the Southern Rhodope Core Complex occurred in two stages: (i) core complex exhumation accommodated by the Kerdylion detachment and (ii) steep normal faulting controlling the deposition of Neogene sedimentary basins that segmented the core complex. Both stages have been controlled by a clockwise rotation of the detachment hanging wall. The bulk amount of extension along the Aegean coastline in Northern Greece reached 120 km. The transition between the two stages occurred in middle Miocene due to an increase in extensional displacement by a factor 5. This transition between two different modes of extension, from localized detachment (i.e., core complex mode) to distributed steep normal faulting (i.e., wide rift mode), occurred at Aegean scale as a result of an acceleration of slab rollback. The Neogene basins emplaced close to the detachment, where brittle upper crust was thin (around 7 km) but containing weak marble layers allowing the formation of ramp-flat extensional systems with rollover-type basin fill. Since Pliocene, the stretching direction changed, from NE-SW to NS, due to the propagation of the North Anatolian Fault in the North Aegean domain.
Published: 2018

2. From Long‐ to Short‐Term Inter‐Plate Coupling at the Subducted Carnegie Ridge Crest, Offshore Central Ecuador

Author: J.‐Y. Collot, J.‐N. Proust, J.‐M. Nocquet, C. Martillo, F. Michaud, J.‐F. Lebrun, L. Schenini, S. Popescu, M.‐J. Hernandez, G. Ratzov, Géoazur (GEOAZUR 7329), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), 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), Escuela Superior Politécnica del Litoral [Guayaquil] (ESPOL), 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), Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA), Géosciences Montpellier, Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles (UA)-Université de Montpellier (UM), Escuela Politécnica Nacional (EPN), Institut de Recherche pour le Developpement (IRD), Institut National des Sciences de l'Univers (INSU), Institut Francais pour l'Exploitation de la Mer (IFREMER), 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), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-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 Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles (UA)
Subjects: [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, Geophysics, Space and Planetary Science, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous)
Abstract: We investigate the relationship between the long-term (Quaternary) interplate coupling and the short-term geodetically derived interseismic coupling at the Central Ecuador subduction zone. At this nonaccretionary margin, the Cabo Pasado shelf promontory and coastal area are associated with two inter-plate geodetically locked patches. The deepest patch ruptured co-seismically during the Mw7.8-2016 Pedernales earthquake, while the shallowest underwent dominantly after-slip. Marine geophysical and chronostratigraphic data allow reconstructing the Quaternary tectonic evolution of the shelf promontory and substantiating variation of the long-term inter-plate coupling that led to the geodetically locked patches. Prior to ∼1.8 Ma, the outer-wedge inter-plate coupling was strong enough to activate trench-subparallel strike-slip faults. Then, between ∼1.8-0.79 Ma, shortening and uplift affected the shelf promontory, implying a locally increased inter-plate coupling. After a short, post-0.79 Ma period of subsidence, shortening and uplift resumed denoting a high inter-plate coupling that endured up to the present. The synchronicity of the structural evolution of the shelf promontory with the subduction chronology of two reliefs of the Carnegie Ridge crest suggests that the locked patches are caused by a geometrical resistance to subduction that propagates landward causing permanent deformation. In 2016, the deepest subducted relief localized stress accumulation and high seismic slip, while the shallowest relief, which is associated with a weakened outer-wedge, prevented updip rupture propagation. Thus, at nonaccretionary margins, active outer-wedge strike-slip faults might be considered a proxi of near-trench coupling, and subducted relief a cause of plate coupling but an obstacle to the tsunami genesis when the relief is shallow. Key Points A trench-parallel strike-slip fault and its earthquake-controlled fault scarps substantiate a pre-1.8 Ma, outer-wedge inter-plate coupling From 1.8 Ma, a robust shelf uplift caused by subducted reliefs highlights a long-term coupling that led to geodetically locked patches The shallowest subducted relief likely impeded the generation of a major tsunami during the Mw7.8, 2016 event Plain Language Summary The 2016-Ecuador earthquake ruptured a subduction fault segment previously locked for decades beneath the coastline. The rupture was arrested updip by another locked fault segment called locked patch, which instead slipped slowly. To understand the cause of the locked patches, their rupture behaviors, and whether the decadal fault locking and long-term subduction processes are related, we reconstructed the Quaternary tectonic evolution of the margin offshore Central Ecuador using geophysical data. We consider that tectonic deformation reflects the long-term inter-plate coupling, which is the ability of the fault to transfer long-term stress and strain to the margin. Prior to ∼1.8 Ma, a trench-subparallel fault accommodating lateral displacement indicates a shallow plate coupling, which increased locally between ∼1.8-0.79 Ma as shown by margin shortening. After a brief subsidence, shortening resumed, denoting a strong coupling that persisted until today in the form of the locked patches. Although many physical factors have been proposed to control plate coupling, here we find that the locked patches are caused by the subduction of two reliefs of a submarine ridge. Remarkably, in 2016, the deepest relief released high elastic strain, while the shallower relief, thrust under a weakened outer-margin, damped updip rupture propagation, impeding a significant tsunami.
Published: 2022

3. Hydro‐Geomorphic Metrics for High Resolution Fluvial Landscape Analysis

Author: Thomas G. Bernard, Philippe Davy, Dimitri Lague, 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), 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), Région Bretagne (Projet LIDAREAU, grant n°. 2020-701), Nantes-Rennes Topo-bathymetric LiDAR Platform of University Rennes 1, ANR-17-CE03-0011,PICS,PICS: vers une Prévision Immédiate intégrée des Impacts des Crues Soudaines(2017), ANR-17-LCV2-0012,eLabo,Monitoring et méthodes numériques pour les géosciences et l'environnement(2017), 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: Geophysics, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, Earth-Surface Processes
Abstract: International audience; Topographic metrics are designed to quantify scale-relevant relationships between geometric properties of landscapes to reveal the processes shaping them. They have long been derived from topographic flow routing algorithms, initially developed for coarse Digital Elevation Models (DEMs), whose resolution (≥ 30 m) and poor precision did not resolve correctly flow patterns and channel flow width. Since high resolution and precision DEMs make the description of meter-scale flow patterns possible, new methods are required to analyze high resolution landforms structures such as hillslope-channel connections, channel width or floodplains. Here, we investigate the potential of 2D hydraulic simulations based on the shallow water equations to replace the classical slope vs drainage area analysis, to analyse river morphology and to identify floodplains. We apply the Floodos model to the 1 m resolution DEM of the Elder Creek catchment, California, from which we derive three hydro-geomorphic metrics accounting for the river geometry: a specific drainage area extended to channels, an effective flow width and the hydraulic slope. We analyse the Elder Creek catchment through what we call the hydraulic slope-area diagram allowing a better identification of hillslope-channel connections than the slope-area approach. The effective flow width is analyzed along the drainage network and is characterized by a power-law relationship consistent with previous observations. We derive metrics based on a multi-runoff approach to automatically identify floodplains and evaluate along-stream variations in hydraulic geometry. The hydro-geomorphic metrics offer a geomorphic analysis suitable for high resolution DEMs and opens up new perspectives in fluvial landscape analysis.
Published: 2022

4. Dynamic Contributions of Stratified Groundwater to Streams Controls Seasonal Variations of Streamwater Transit Times

Author: Jean Marçais, Louis A. Derry, Luca Guillaumot, Luc Aquilina, Jean‐Raynald de Dreuzy, RiverLy - Fonctionnement des hydrosystèmes (RiverLy), Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Centre National de la Recherche Scientifique (CNRS), Cornell University [New York], 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), 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), ANR-17-MPGA-0009,CZ-TOP,Water, reactions and isotopes in the Critical Zone(2017), Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPC), 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: Particle tracking, CFC tracers, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, Travel time distributions, Boussinesq equations, Streamwater age, Groundwater age, Water Science and Technology
Abstract: International audience; Streamwater transit time distributions display a variable proportion of old waters ( ≥1 yr). We hypothesize that the corresponding long transit times result from groundwater contributions to the stream and that seasonal streamwater transit time variations result from 1) the variable contributions of different flowpaths (overland flow, seepage flow and baseflow) and 2) the stratification of groundwater residence times. We develop a parsimonious model to capture the groundwater contribution to the stream discharge and its effect on transient transit times. Infiltration is partitioned according to the aquifer saturation between Boussinesq groundwater flow and overland flow. Time-variable transit time distributions are obtained with a new 2D particle tracking algorithm. Hydraulic conductivity, total and drainable porosities are calibrated by using discharge and CFC tracer data on a crystalline catchment located in Brittany (France). The calibrated models succeed in reproducing CFCs concentrations and discharge dynamics. The groundwater flow contribution to the stream is controlled by the aquifer hydraulic conductivity, while its age is controlled by the drainable and total porosities. Old groundwater ( ≥1 yr) is the source for approximately 75 % of the streamflow with strong seasonal variations (between 40 and 95 %). Mean transit times are approximately 13 years, varying between 6 and 20 years, inversely proportional to the groundwater contribution. These seasonal variations are driven by the groundwater versus overland flow partitioning. The stratification of groundwater residence times in the aquifer plays a minor role in the streamwater transit times but is key for the transit time dynamics of the groundwater contribution to the stream.
Published: 2022

5. Sharp Transition to Strongly Anomalous Transport in Unsaturated Porous Media

Author: Andrés Velásquez-Parra, Yves Méheust, Matthias Willmann, Tanguy Le Borgne, Joaquin Jimenez-Martinez, Tomás Aquino, Swiss Federal Institute of Aquatic Science and5Technology, Department of Civil, Environmental and Geomatic Engineering [ETH Zürich] (D-BAUG), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), 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), National Science Foundation (SNF, grant Nr. 200021 178986, European Project: 792041, European Project: 648377,H2020,ERC-2014-CoG,ReactiveFronts(2015), 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 ETH-Bereich Forschungsanstalten
Subjects: Physics::Fluid Dynamics, Geophysics, Fluid Dynamics (physics.flu-dyn), FOS: Physical sciences, General Earth and Planetary Sciences, Physics - Fluid Dynamics, [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology
Abstract: The simultaneous presence of liquid and gas in porous media increases flow heterogeneity compared to saturated flows. However, the impact of saturation on flow and transport has so far remained unclear. The presence of gas in the pore space leads to flow reorganization. We develop a theoretical framework that captures the impact of that reorganization on pore-scale fluid velocities. Preferential flow is distributed spatially through a backbone, and flow recirculation occurs in flow dead-ends. We observe, and predict theoretically, that this previously identified flow structure induces a marked change in the scaling of the velocity probability density function compared to the saturated configuration and a sharp transition to strongly anomalous transport. We develop a transport model using the continuous time random walk theory that predicts advective transport dynamics for all saturation degrees. Our results provide a new modeling framework linking phase heterogeneity to flow heterogeneity in unsaturated porous media., Geophysical Research Letters, 49 (3), ISSN:0094-8276, ISSN:1944-8007
Published: 2022

6. Constraining Plateau Uplift in Southern Africa by Combining Thermochronology, Sediment Flux, Topography, and Landscape Evolution Modeling

Author: François Guillocheau, Roderick Brown, Jessica R. Stanley, Mark Wildman, Jean Braun, Romain Beucher, Cécile Robin, Rebecca M. Flowers, Guillaume Baby, University of Idaho [Moscow, USA], University of Potsdam, Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), 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 Colorado [Boulder], University of Glasgow, Research School of Earth Sciences [Canberra] (RSES), Australian National University (ANU), University of Potsdam = Universität Potsdam, 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), 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 Alexander von Humboldt-Stiftung
Subjects: epeirogeny, Landscape evolution model, 010504 meteorology & atmospheric sciences, 010502 geochemistry & geophysics, 01 natural sciences, Paleontology, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), Southern African Plateau, Epeirogenic movement, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, 0105 earth and related environmental sciences, geography, Plateau, geography.geographical_feature_category, 15. Life on land, erosion, Cretaceous, Thermochronology, Gondwana, Geophysics, 13. Climate action, Space and Planetary Science, Erosion, Cenozoic, Geology
Abstract: The uplift of the southern African Plateau with its average elevations of ~1000 m is often attributed to mantle processes, but there are conflicting theories for the timing and drivers of topographic development. Evidence for most proposed plateau development histories is derived from continental erosion histories, marine stratigraphic architecture, or landscape morphology. Here we use a landscape evolution model to integrate a large dataset of low-temperature thermochronometry, sediment flux rates to surrounding marine basins, and current topography for southern Africa. We explore three main hypotheses for surface uplift: 1) southern Africa was already elevated by the Early Cretaceous before Gondwana breakup, 2) uplift and continental tilting occurred during the mid-Cretaceous, or 3) uplift occurred during the mid to late Cenozoic. We test which of these three intervals of plateau development are plausible by using an inversion method to constrain the range in erosional and uplift model parameters that can best reproduce the observed data. Results indicate four regions of parameter space that fall into two families of uplift histories are most compatible with the data. Both uplift families have limited initial topography with some topographic uplift and continental tilting starting at ~90-100 Ma. In one acceptable scenario, nearly all of the topography, >1300 m, is created at this time with little Cenozoic uplift. In the other acceptable scenario, ~400-800 m of uplift occurs in the mid- Cretaceous with another ~500-1000 m of uplift in the mid-Cenozoic. The two model scenarios have different geodynamic implications, which we compare to geodynamic models.
Published: 2021

7. Long‐Period Astronomical Forcing of Westerlies' Strength in Central Asia During Miocene Climate Cooling

Author: Sietske J. Batenburg, Thomas Voigt, Jacek Raddatz, Silke Voigt, Konstantin Frisch, Iris Arndt, Erwin Appel, Axel Gerdes, Richard Albert, Yuki Weber, Verena Verestek, Goethe-Universität Frankfurt am Main, Institute of Geosciences [Frankfurt am Main], Eberhard Karls Universität Tübingen = Eberhard Karls University of Tuebingen, Friedrich-Schiller-Universität = Friedrich Schiller University Jena [Jena, Germany], Harvard University [Cambridge], 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), AP 34/41‐1, Deutsche Forschungsgemeinschaft, Voigt, Silke, 1 Institut für Geowissenschaften Goethe‐Universität Frankfurt Germany, Verestek, Verena, 2 Fachbereich Geowissenschaften Eberhard‐Karls‐Universität Tübingen Germany, Appel, Erwin, Albert, Richard, Gerdes, Axel, Arndt, Iris, Raddatz, Jacek, Voigt, Thomas, 3 Institut für Geowissenschaften Friedrich‐Schiller‐Universität Jena Germany, Weber, Yuki, 4 Department of Earth and Planetary Sciences Harvard University Cambridge MA USA, Batenburg, Sietske J., 5 Géosciences Rennes Université de Rennes 1 Rennes France, Harvard University, Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), and 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)
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, Orbital forcing, Central asia, Continental climate, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, continental climate, Central Asia, Long period, ddc:550, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, integrated stratigraphy, 0105 earth and related environmental sciences, orbital forcing, Miocene cooling, Astronomical forcing, Paleontology, Westerlies, 15. Life on land, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, 13. Climate action, Climatology, Geology
Abstract: The continental expression of global cooling during the Miocene Climate Transition in Central Asia is poorly documented, as the tectonically active setting complicates the correlation of Neogene regional and global climatic developments. This study presents new geochemical data (CaSO4 content, carbonate δ13C and δ18O) from the endorheic alluvial‐lacustrine Aktau succession (Ili Basin, south‐east Kazakhstan) combined with findings from the previously published facies evolution. Time series analysis revealed long‐eccentricity forcing of the paleohydrology throughout the entire succession, split into several facies‐dependent segments. Orbital tuning, constrained by new laser ablation U‐Pb dates and a preexisting magnetostratigraphy, places the succession in a 5.0 Ma long interval in the middle to late Miocene (15.6 to 10.6 Ma). The long‐term water accumulation in the Ili Basin followed the timing of the Miocene Climate Transition, suggesting increased precipitation in the catchment area in response to climate cooling and stronger westerly winds. This was paced by minima of the 2.4 Ma eccentricity cycle, which favored the establishment of a discharge playa (~14.3 Ma) and a perennial lake (12.6 to 11.8 Ma). Furthermore, low obliquity amplitudes (nodes) caused a transient weakening of the westerlies at ~13.7 to 13.5 Ma and at ~12.7 Ma, resulting in negative hydrological budgets and salinization. Flooding of the windward Ili Basin coeval with aridification in the leeward basins suggests that the Tian Shan was a climate boundary already in the middle Miocene. Our results emphasize the impact of climate fluctuations on the westerlies' strength and thus on Central Asian hydrology., Plain Language Summary: The global climate changed from an exceptional warm to a colder state in the middle Miocene epoch, representing a milestone in the evolution of today's climate. This study focuses on the, so far fragmentary, understanding of the Central Asian climate response to this global climate transition by investigating deposits of a former (salt) lake in the Ili Basin, southeast Kazakhstan. Regular sediment alternations represent cycles of low and high water level, overprinted by a long‐term lake expansion. Time series analysis of climate sensitive geochemical and environmental parameters, together with the determination of absolute rock ages, enabled the identification of sedimentary cycles (405 ka and 1.2 Ma long), which are equivalent to climate influencing variations of the Earth's orbit and tilt angle. We conclude that water level maxima are linked to periods of low seasonal climate differences reoccurring every 405 ka. The lake expansion is caused by more precipitation due to strengthened westerly winds, in response to global cooling. Westerly winds were transiently weakened during periods of low variability of the Earth's tilt angle, promoting high evaporation and salinization. Our results emphasize the impact of climate change on the westerlies' strength and thus on Central Asian moisture supply., Key Points: The endorheic Miocene Ili Basin features orbital control of its hydrological budget by long eccentricity and obliquity amplitude modulation. Obliquity amplitude modulation affected the westerlies' strength during the Miocene Climate Transition. The Miocene global cooling led to strengthening of the westerlies reflected by groundwater accumulation and lake expansion in the Ili Basin., Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659
Published: 2019

8. Retreat Pattern of Glaciers Controls the Occurrence of Turbidity Currents on High‐Latitude Fjord Deltas (Eastern Baffin Island)

Author: David Burgess, Jean-François Ghienne, Alexandre Normandeau, J. E. Hughes Clarke, W. D. Van Wychen, Pierre Dietrich, Patrick Lajeunesse, Geological Survey of Canada [Dartmouth] (GSC Atlantic), Geological Survey of Canada - Office (GSC), Natural Resources Canada (NRCan)-Natural Resources Canada (NRCan), 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 Johannesburg (UJ), University of New Hampshire (UNH), Université Laval [Québec] (ULaval), Geological Survey of Canada [Ottawa] (GSC Central & Northern Canada), 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 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 University of Johannesburg [South Africa] (UJ)
Subjects: geography, geography.geographical_feature_category, Turbidity current, 010504 meteorology & atmospheric sciences, Fjord, Glacier, 01 natural sciences, Geophysics, Oceanography, Arctic, 13. Climate action, [SDU.STU.ST]Sciences of the Universe [physics]/Earth Sciences/Stratigraphy, Erosion, Deglaciation, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology, 14. Life underwater, Glacial period, Ice sheet, Geology, 0105 earth and related environmental sciences, Earth-Surface Processes
Abstract: International audience; Glacier and ice sheet mass loss as a result of climate change is driving important coastal changes in Arctic fjords. Yet limited information exists for Arctic coasts regarding the influence of glacial erosion and ice mass loss on the occurrence and character of turbidity currents in fjords, which themselves affect delta dynamics. Here we show how glacial erosion and the production of meltwaters and sediments associated with the melting of retreating glaciers control the generation of turbidity currents in fjords of eastern Baffin Island (Canada). The subaqueous parts of 31 river mouths along eastern Baffin Island were mapped by high-resolution swath bathymetry in order to assess the presence or absence of sediment waves formed by turbidity currents on delta fronts. By extracting glaciological and hydrological watershed characteristics of these river mouths, we demonstrate that the presence and areal extent of glaciers are a key control for generating turbidity currents in fjords. However, lakes formed upstream during glacial retreat significantly alter the course of sediment routing to the deltas by forming temporary sinks, leading to the cessation of turbidity currents in the fjords. Due to the different deglaciation stages of watersheds in eastern Baffin Island, we put these results into a temporal framework of watershed deglaciation to demonstrate how the retreat pattern of glaciers, through the formation and filling of proglacial lakes, affects the turbidity current activity of deltas.
Published: 2019

9. How Do Continents Deform During Mantle Exhumation? Insights From the Northern Iberia Inverted Paleopassive Margin, Western Pyrenees (France)

Author: Yves Lagabrielle, Patrick Monié, Benjamin Corre, Riccardo Asti, Serge Fourcade, 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), Géosciences Montpellier, Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles (UA), Bureau de Recherches Géologiques et Minières, 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), and Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Université des Antilles (UA)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, geography, Rift, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Continental crust, Crust, Massif, 15. Life on land, 010502 geochemistry & geophysics, 01 natural sciences, Mantle (geology), Paleontology, Tectonics, Geophysics, Geochemistry and Petrology, Passive margin, Shear zone, Geology, 0105 earth and related environmental sciences
Abstract: International audience; Extreme crustal thinning associated with subcontinental mantle exhumation characterizes the distal domain of some current, magma‐poor continental passive margins. Since these domains lie at abyssal depths and are hardly accessible, their internal structure and the finite strain of the stretched crust are not directly observed and are only inferred. Detailed field study was conducted on exceptionally preserved Cretaceous distal margin analogues in two key areas of the western Pyrenees (North Pyrenean Zone): the Urdach and Saraillé ultramafic massifs in the Chaînons Béarnais range. A tight sampling allowed us to characterize the conditions of the ductile deformation of the continental crust exhumed together with the mantle. New 40Ar/39Ar dating on muscovite constrains the timing of the last deformation of the continental crust in relation with mantle exhumation to the late Albian. We propose a new reconstruction for the distal part of the North Iberian paleo‐passive margin based on the following constraints: (i) post‐Silurian Paleozoic rocks are never found in the distal domain; (ii) lower crustal levels are not found in the exhumed crustal units; (iii) extension in the pre‐Silurian series is accomplished by lenticular deformation and pervasive ductile flattening through anastomosing extensional mylonitic shear zones at temperatures of 350‐450°C; (iv) at the final step of exhumation, only pre‐Silurian crustal lenses remained welded on the exhumed mantle. Finally, we discuss the importance of the crustal structure inherited from previous Paleozoic and Mesozoic tectonic events and we state that mantle exhumation was partially achieved before the Cretaceous North Pyrenean rifting.
Published: 2019

10. Diachronous Growth of the Northern Tibetan Plateau Derived From Flexural Modeling

Author: Marc Jolivet, Yiduo Liu, Lin Wang, Xiangzhong Li, Feng Cheng, Zhaojie Guo, Changhao Zhang, Andrew V. Zuza, Peking University [Beijing], University of Nevada [Reno], 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 Houston, Yunnan University, PetroChina Compagny, Partenaires INRAE, National Science Foundation (NSF). Grant Number: EAR‐1914501, Key Laboratory of Deep‐Earth Dynamics of Ministry of Natural Resources, Institute of Geology, Chinese Academy of Geological Sciences. Grant Number: J1901, Natural Science Foundation of China. Grant Number: 41888101, 41930213, 41672163, CAS, IEE, CAS, State Key Laboratory of Loess and Quaternary Geology (SKLLQG, IEE CAS). Grant Number: SKLLQG1903, Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), and 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)
Subjects: [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, geography, Plateau, geography.geographical_feature_category, Paleoclimate, 010504 meteorology & atmospheric sciences, Qaidam basin, Paleoelevation, Diachronous, 15. Life on land, 010502 geochemistry & geophysics, 01 natural sciences, Tibetan plateau, Early Cenozoic, Paleontology, Geophysics, Flexural modeling, Flexural strength, 13. Climate action, Paleoclimatology, General Earth and Planetary Sciences, Geology, 0105 earth and related environmental sciences
Abstract: International audience; The early Cenozoic topography of the northern Tibetan plateau remains enigmatic because of the paucity of independent paleoelevation constraints. Long‐held views of northward propagating deformation imply a low Paleogene elevation, but this prediction is speculative. We apply flexural modeling to reconstructed Paleogene isopach data obtained from the Qaidam basin, which requires a larger topographic load in the Qilian Shan and a smaller load in the Eastern Kunlun Shan. Incorporating knowledge of proto‐Paratethys marine incursions in the Paleogene Qaidam basin, we infer a topographically low (0.4‐1.0 km) Eastern Kunlun Shan and a higher (0.4‐1.5 km) Qilian Shan during the Paleogene. This implied paleo‐relief contrasts with previous predictions and suggests more recently, Neogene surface uplift in the Eastern Kunlun Shan has been more significant than in Qilian Shan, highlighting diachronous growth of the northern Tibetan plateau. The low‐moderate paleoelevation implies a warmer and more humid climate in Northern Tibet during the Paleogene.
Published: 2021

11. A Re‐evaluation of the Plenus Cold Event, and the Links Between CO2, Temperature, and Seawater Chemistry During OAE 2

Author: Sietske J. Batenburg, Serginio R. C. Remmelzwaal, Stuart A. Robinson, Hugh C. Jenkyns, Andrew S. Gale, Lauren K. O'Connor, Ian J. Parkinson, University of Oxford [Oxford], University of Arizona, Department of Earth Sciences [Oxford], University of Bristol [Bristol], 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 Portsmouth, University College, Oxford, University of Oxford, Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), and 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)
Subjects: Neodymium, Atmospheric Science, 010504 meteorology & atmospheric sciences, Ocean chemistry, Excursion, Ocean current, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Paleontology, Context (language use), 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Carbon cycle, Plenus Cold Event, SSTs, Ocean circulation, Boreal, 13. Climate action, Upwelling, CO2, Seawater, 14. Life underwater, OAE2, 0105 earth and related environmental sciences
Abstract: International audience; The greenhouse world of the mid‐Cretaceous (~94 Ma) was punctuated by an episode of abrupt climatic upheaval: Oceanic Anoxic Event 2 (OAE 2). High‐resolution climate records reveal considerable changes in temperature, carbon cycling, and ocean chemistry during this climatic perturbation. In particular, an interval of cooling has been detected in the English Chalk on the basis of an invasive boreal fauna and bulk oxygen‐isotope excursions registered during the early stages of OAE 2—a phenomenon known as the Plenus Cold Event (PCE), which has tentatively been correlated with climatic shifts worldwide.Here we present new high‐resolution neodymium‐, carbon‐, and oxygen‐isotope data, as well as elemental chromium concentrations and cerium anomalies, from the English Chalk exposed at Dover, UK, which we evaluate in the context of >400 records from across the globe. A negative carbon‐isotope excursion that correlates with the original ‘PCE’ is consistently expressed worldwide, and CO2 proxy records, where available, indicate a rise and subsequent fall in CO2 over the Plenus interval. However, variability in the timing and expression of cooling at different sites suggests that, although sea‐surface paleo‐temperatures may reflect a response to global CO2 change, local processes likely played a dominant role at many sites. Variability in the timing and expression of changes in water‐mass character, and problems in determining the driver of observed proxy changes, suggest that no single simple mechanism can link the carbon cycle to oceanography during the Plenus interval and other factors including upwelling and circulation patterns were locally important. As such, it is proposed that the Plenus carbon‐isotope event is a more reliable stratigraphic marker to identify the Plenus interval, rather than any climatic shifts that may have been overprinted by local effects.
Published: 2020

12. Toward robust and predictive geodynamic modeling : the way forward in frictional plasticity

Author: Thibault Duretz, Laetitia Le Pourhiet, Philippe Yamato, René de Borst, 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), University of Sheffield [Sheffield], 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), NEEDS 2019, Centre National de la Recherche Scientifique, 664734, Seventh Framework Programme, 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), Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS), 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, 010504 meteorology & atmospheric sciences, Deformation (mechanics), Thermodynamic equilibrium, Mechanics, Geodynamics, Plasticity, 010502 geochemistry & geophysics, 01 natural sciences, Geophysics, numerical modeling, Rheology, Shear (geology), plasticity, General Earth and Planetary Sciences, tectonics, rheology, Sensitivity (control systems), geodynamics, Shear band, faulting, Geology, 0105 earth and related environmental sciences
Abstract: International audience; Strain localization is a fundamental characteristic of plate tectonics. The resulting deformation structures shape the margins of continents and the internal structure of tectonic plates. To model the occurrence of faulting, geodynamic models generally rely on frictional plasticity. Frictional plasticity is normally embedded in visco‐plastic (V‐P) or visco‐elasto‐plastic (V‐E‐P) rheologies. This poses some fundamental issues, such as the difficulty, or often inability, to obtain a converged equilibrium state, and a severe grid sensitivity. Here, we study shear banding at crustal‐scale using a visco‐elasto‐viscoplastic (V‐E‐VP) model. We show that this rheology allows to accurately satisfy equilibrium, leads to shear band patterns that converge upon mesh refinement and preserves characteristic shear band angles. Moreover a comparison with analytic models and laboratory data reveals that V‐E‐VP rheology captures first order characteristics of frictional plasticity. V‐E‐VP models thus overcomes limitations of V‐P and V‐E‐P models and appears as an attractive alternative for geodynamic modeling.
Published: 2020

13. Experimental and Model‐Based Investigation of the Effect of the Free‐Surface Flow Regime on the Detection Threshold of Warm Water Inflows

Author: Pascal Pichelin, Hugo Le Lay, Florentina Moatar, Zahra Thomas, François Rouault, Olivier Bour, Sol Agro et hydrosystème Spatialisation (SAS), Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-INSTITUT AGRO Agrocampus Ouest, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), GéoHydrosystèmes COntinentaux (GéHCO EA6293), Université de Tours (UT), 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), 2016‐0204, Agence de l'eau Loire-Bretagne, AGROCAMPUS OUEST, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), 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), UR RiverLy, Villeurbanne, INRAE, and Université de Tours
Subjects: 010504 meteorology & atmospheric sciences, Turbulence, 0208 environmental biotechnology, Flow (psychology), Soil science, Laminar flow, 02 engineering and technology, Inflow, 01 natural sciences, 6. Clean water, 020801 environmental engineering, Physics::Fluid Dynamics, Flume, [SPI]Engineering Sciences [physics], [SDU]Sciences of the Universe [physics], Free surface, [SDE]Environmental Sciences, Environmental science, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, Surface water, ComputingMilieux_MISCELLANEOUS, Groundwater, 0105 earth and related environmental sciences, Water Science and Technology
Abstract: International audience; Heat has been used as a tracer to identify and quantify groundwater inflows into streams. Over the last decade, a few methods have used fiber-optic distributed temperature sensing to facilitate assessment of such inflows into small streams. However, these methods focused mainly on the groundwater percentage and the thermal contrast between groundwater and surface water without considering the flow regime of the surface water. In this study, artificial water inflows into a controlled flume were examined using fiber-optic distributed temperature sensing to quantify the thermal anomalies induced as a function of the flow regime (turbulent or laminar). Computer simulations were then performed to widen the range of the parameters tested and provide insight into the physical processes involved. Experiments conducted under the turbulent regime were in accordance with results and uncertainties of previous studies. Under the laminar regime, however, the inflow-induced thermal anomalies were always smaller than those under the turbulent regime for a given inflow percentage. Therefore, the actual inflow percentage may be underestimated when using a classic method under a laminar regime.
Published: 2020

14. Pre-Alpine (Variscan) Inheritance: A Key for the Location of the Future Valaisan Basin (Western Alps)

Author: G. V. Dal Piaz, Michel Ballèvre, Paola Manzotti, 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), Institute of Geological Sciences [Bern], University of Bern, Universita degli Studi di Padova, Université de Rennes 1, 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 Università degli Studi di Padova = University of Padua (Unipd)
Subjects: [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Permian, Structural basin, Fault (geology), 010502 geochemistry & geophysics, 01 natural sciences, Paleontology, Geophysics, Basement (geology), Geochemistry and Petrology, Penninic, Carboniferous, Alpine orogeny, Shear zone, Geology, 0105 earth and related environmental sciences
Abstract: International audience; The boundary between the Helvetic and the Penninic (= Briançonnais) Zones has long been recognized as a major fault (“Penninic Front”) in the Western Alps. A narrow oceanic domain has been postulated at least along part of this boundary (the Valaisan ocean). However, the information provided by the pre-Triassic basement has not been fully exploited, and will be discussed here in detail. The igneous and metamorphic history of the pre-Triassic basement shows significant differences between the External Massifs from the Helvetic Zone, with abundant late Carboniferous granites, and the basement of the Briançonnais Zone, including the Internal Massifs (Dora-Maira, Gran Paradiso, Monte Rosa), devoid of Carboniferous granites. A major coal-bearing basin, the “Zone Houillère”, opened along this boundary. This limnic intramontane basin has never been properly investigated. The Zone Houillère is not comparable with the external, paralic, flexural, basins on both sides of the Variscan belt, but shows similarities with the Saar-Saale basin. Like the latter, we interpret the Zone Houillère as a transtensional basin opened along a major, crustal-scale, fault zone, namely the East Variscan Shear Zone. The Permian magmatism and sedimentation displays contrasting distributions, being absent or very localized in the Helvetic Zone, and widespread in the Penninic Zone. The above data indicate that the structural inheritance from the Variscan belt plays a major role in defining the future location of the Valaisan basin, i.e. the boundary between the European palaeomargin and the Briançonnais microcontinent.
Published: 2018

15. Neutrally buoyant tracers in hydrogeophysics: Field demonstration in fractured rock

Author: Niklas Linde, Tanguy Le Borgne, Marie-Françoise Gérard, Ludovic Baron, John S. Selker, Nicolas Lavenant, Olivier Bour, Alexis Shakas, Institut des sciences de la terre [Lausanne] (ISTE), Université de Lausanne = University of Lausanne (UNIL), Department of Biological and Ecological Engineering, Oregon State University (OSU), 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), 200021-146602, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, 1551483, National Science Foundation, French National Observatory H+, ANR-11-EQPX-0011, ANR project CRITEX, ANR-11-EQPX-0011,CRITEX,Parc national d'équipements innovants pour l'étude spatiale et temporelle de la Zone Critique des Bassins Versants(2011), Université de Lausanne (UNIL), 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: geography, Hydrogeology, geography.geographical_feature_category, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], Flow tracer, 0208 environmental biotechnology, Hydrogeophysics, Aquifer, Soil science, 02 engineering and technology, 020801 environmental engineering, Geophysics, Neutral buoyancy, TRACER, Ground-penetrating radar, General Earth and Planetary Sciences, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, Porosity, Geomorphology, Geology
Abstract: International audience; Electrical and electromagnetic methods are extensively used to map electrically conductive tracers within hydrogeologic systems. Often, the tracers used consist of dissolved salt in water, leading to a denser mixture than the ambient formation water. Density effects are often ignored and rarely modeled but can dramatically affect transport behavior and introduce dynamics that are unrepresentative of the response obtained with classical tracers (e.g., uranine). We introduce a neutrally buoyant tracer consisting of a mixture of salt, water, and ethanol and monitor its movement during push-pull experiments in a fractured rock aquifer using ground-penetrating radar. Our results indicate a largely reversible transport process and agree with uranine-based push-pull experiments at the site, which is in contrast to results obtained using dense saline tracers. We argue that a shift toward neutrally buoyant tracers in both porous and fractured media would advance hydrogeophysical research and enhance its utility in hydrogeology.
Published: 2017

16. Impact of saturation on dispersion and mixing in porous media: Photobleaching pulse injection experiments and shear‐enhanced mixing model

Author: Hervé Tabuteau, Yves Méheust, Tanguy Le Borgne, Joaquin Jimenez-Martinez, 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), Institut de Physique de Rennes (IPR), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), (project AO2014-906387), EC2CO program of INSU/CNRS, 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 Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [PHYS]Physics [physics], Materials science, Finite volume method, 010504 meteorology & atmospheric sciences, business.industry, 0208 environmental biotechnology, 02 engineering and technology, Mechanics, Dissipation, 01 natural sciences, Photobleaching, Fick's laws of diffusion, 020801 environmental engineering, Optics, TRACER, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, business, Porous medium, Porosity, Scaling, 0105 earth and related environmental sciences, Water Science and Technology
Abstract: The dynamics of solute dispersion and mixing in unsaturated flows is analyzed from photo-bleaching experiments in two-dimensional porous micro-models. This technique allows producing pulse line (delta-Dirac) injections of a conservative tracer by bleaching a finite volume of fluorescent without disturbing the flow field. The temporal evolution of the concentration field and the spatial distribution of the air and water phases can be monitored at pore scale. We study the dispersion and mixing of a line of tracer under different water saturations. While dispersion in saturated porous media follows an approximately Fickian scaling, a shift to ballistic scaling is observed as soon as saturation is lowered. Hence, at the time scale of observation, dispersion in our unsaturated flows is dominated by the ballistic separation of tracer blobs within the water phase, between trapped clusters and preferential flow paths. While diffusion plays a minor role in the longitudinal dispersion during the time scale of the experiments, its interplay with fluid deformation is apparent in the dynamics of mixing. The scalar dissipation rates show an initial stretching regime, during which mixing is enhanced by fluid deformation, followed by a dissipation regime, during which diffusion overcomes compression induced by stretching. The transition between these two regimes occurs at the mixing time, when concentration gradients are maximum. We propose a predictive analytical model, based on shear-enhanced diffusion, that captures the dynamics of mixing from basic unsaturated porous media parameters, suggesting that this type of model may be a useful framework at larger scales. This article is protected by copyright. All rights reserved.
Published: 2017

17. Connectivity, permeability, and channeling in randomly distributed and kinematically defined discrete fracture network models

Author: Philippe Davy, Caroline Darcel, J.-R. de Dreuzy, R. Le Goc, J. Maillot, 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), Itasca Consultants, 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), 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), and Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)
Subjects: 2. Zero hunger, Discrete fracture, 010504 meteorology & atmospheric sciences, 0208 environmental biotechnology, Nucleation, Geometry, 02 engineering and technology, Kinematics, Poisson distribution, 01 natural sciences, Physics::Geophysics, 020801 environmental engineering, Permeability (earth sciences), symbols.namesake, symbols, Geotechnical engineering, Length distribution, Area density, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, Geology, 0105 earth and related environmental sciences, Water Science and Technology, Network model
Abstract: International audience; A major use of DFN models for industrial applications is to evaluate permeability and flow structure in hardrock aquifers from geological observations of fracture networks. The relationship between the statistical fracture density distributions and permeability has been extensively studied, but there has been little interest in the spatial structure of DFN models, which is generally assumed to be spatially random (i.e. Poisson). In this paper, we compare the predictions of Poisson DFNs to new DFN models where fractures result from a growth process defined by simplified kinematic rules for nucleation, growth and fracture arrest (Davy et al, 2010, 2013). This so-called ‘kinematic fracture model' is characterized by a large proportion of T-intersections, and a smaller number of intersections per fracture. Several kinematic models were tested and compared with Poisson DFN models with the same density, length and orientation distributions. Connectivity, permeability and flow distribution were calculated for 3D networks with a self-similar power-law fracture length distribution. For the same statistical properties in orientation and density, the permeability is systematically and significantly smaller by a factor of 1.5 to 10 for kinematic than for Poisson models. In both cases, the permeability is well described by a linear relationship with the areal density p32, but the threshold of kinematic models is 50% larger than of Poisson models. Flow channeling is also enhanced in kinematic DFN models. This analysis demonstrates the importance of choosing an appropriate DFN organization for predicting flow properties from fracture network parameters.
Published: 2016

18. Elastic Properties of Fractured Rock Masses With Frictional Properties and Power Law Fracture Size Distributions

Author: Philippe Davy, D. Mas Ivars, R. Le Goc, Caroline Darcel, 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), Itasca Consultants, Swedish Nuclear Fuel and Waste Management Co (SKB), Royal Institute of Technology [Stockholm] (KTH ), Posiva Oy, Swedish Nuclear Fuel and Waste Management Co. (SKB), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), and 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)
Subjects: education.field_of_study, Materials science, 010504 meteorology & atmospheric sciences, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], Population, Modulus, Stiffness, Mechanics, Slip (materials science), 16. Peace & justice, 010502 geochemistry & geophysics, 01 natural sciences, Power law, Physics::Geophysics, Geophysics, Shear (geology), Space and Planetary Science, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), Exponent, medicine, Coulomb, medicine.symptom, education, 0105 earth and related environmental sciences
Abstract: International audience; We derive the relationships that link the general elastic properties of rock masses to the geometrical properties of fracture networks, with a special emphasis to the case of frictional crack surfaces. We extend the well-known elastic solutions for free-slipping cracks to fractures whose plane resistance is defined by an elastic fracture (shear) stiffness k s and a stick-slip Coulomb threshold. A complete set of analytical solutions have been derived for (i) the shear displacement in the fracture plane for stresses below the slip threshold and above, (ii) the partitioning between the resistances of the fracture plane on the one hand and of the elastic matrix on the other hand, and (iii) the stress conditions to trigger slip. All the expressions have been checked with numerical simulations. The Young's modulus and Poisson's ratio were also derived for a population of fractures. They are controlled both by the total fracture surface for fractures larger than the stiffness length l S (defined by k s and the intact matrix elastic properties) and by the percolation parameter of smaller fractures. These results were applied to power law fracture size distributions, which are likely relevant to geological cases. We show that if the fracture size exponent is in the range -3 to -4, which corresponds to a wide range of geological fracture networks, the elastic properties of the bulk rock are almost exclusively controlled by k s and the stiffness length, meaning that the fractures of size l S play a major role in the definition of the elastic properties.
Published: 2018

19. Is the Dupuit assumption suitable for predicting the groundwater seepage area in hillslopes?

Author: J.-R. de Dreuzy, Philippe Davy, Etienne Bresciani, 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), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), and 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)
Subjects: Hydrogeology, Groundwater flow, Hydraulic conductivity, Impervious surface, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Cutoff, Soil science, Geotechnical engineering, Groundwater recharge, Function (mathematics), Geology, Water Science and Technology, Groundwater seepage
Abstract: International audience; Many physically based hydrological/hydrogeological models used for predicting groundwater seepage areas, including topography-based index models such as TOPMODEL, rely on the Dupuit assumption. To ensure the sound use of these simplified models, knowledge of the conditions under which they provide a reasonable approximation is critical. In this study, a Dupuit solution for the seepage length in hillslope cross sections is tested against a full-depth solution of saturated groundwater flow. In homogeneous hillslopes with horizontal impervious base and constant-slope topography, the comparison reveals that the validity of the Dupuit solution depends not only on the ratio of depth to hillslope length d/L (as might be expected), but also on the ratio of hydraulic conductivity to recharge K/R and on the topographic slope s. The validity of the Dupuit solution is shown to be in fact a unique function of another ratio, the ratio of depth to seepage length d/LS. For d/LS0.2, it increases dramatically. In practice, this criterion can be used to test the validity of Dupuit solutions. When d/LS increases beyond that cutoff, the ratio of seepage length to hillslope length LS/L given by the full-depth solution tends toward a nonzero asymptotic value. This asymptotic value is shown to be controlled by (and in many cases equal to) the parameter R/(sK). Generalization of the findings to cases featuring heterogeneity, nonhorizontal impervious base and variable-slope topography is discussed.
Published: 2014

20. Does GRACE see the terrestrial water cycle 'intensifying'?

Author: Eicker, Annette, Forootan, Ehsan, Springer, Anne, Longuevergne, Laurent, Kusche, Jürgen, Institute of Geodesy and Geoinformation [Bonn] (IGG), Rheinische Friedrich-Wilhelms-Universität Bonn, 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), German Research Foundation DFG, HPSC Terrsys, 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), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), and 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)
Subjects: [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology
Abstract: International audience; Several researchers have postulated that, under a changing climate due to anthropogenic forcing, an intensification of the water cycle is already under way. This is usually related to increases in hydrological fluxes as precipitation (P), evapotranspiration (E), and river discharge (R). It is under debate, however, whether such observed or reconstructed flux changes are real and on what scales. Large-scale increase or decrease of the flux deficit (P-E-R), i.e. flux changes that do not compensate, would lead to acceleration or deceleration of water storage anomalies potentially visible in GRACE data. In agreement with earlier studies, we do find such accelerations in global maps of gridded GRACE water storage anomalies over 2003-2012. However, these have been generally associated with interannual and decadal climate variability. Yet, we show that even after carefully isolating and removing the contribution of El Nino that partially masks long-term changes, using a new method, accelerations of up to 12mm/yr2 remain in regions such as Australia, Turkey, and Northern India. We repeat our analysis with flux fields from two global atmospheric reanalyses that include land surface models (ERA-Interim, MERRA-Land). While agreeing well with GRACE on shorter time scales, they fall short in displaying long-term trends corresponding to GRACE accelerations. We hypothesize that this may be due to time-varying biases in the reanalysis fluxes as noticed in other studies. We conclude that even though its data record is short, GRACE provides new information that should be used to constrain future reanalyses towards a better representation of long-term water cycle evolution.
Published: 2016

21. Identification of sources of potential fields with the continuous wavelet transform: Complex wavelets and application to aeromagnetic profiles in French Guiana

Author: Claude Delor, Pascal Sailhac, Frédérique Moreau, Dominique Gibert, Armand Galdeano, Institut de Physique du Globe de Paris (IPGP), 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), 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), and Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)
Subjects: Atmospheric Science, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Soil Science, Inverse, Aquatic Science, Oceanography, Exploration Geophysics: Computational methods, potential fields, Magnetization, Continuous wavelet, Wavelet, Mathematical Geophysics: Inverse theory, Geochemistry and Petrology, Homogeneity (physics), Earth and Planetary Sciences (miscellaneous), Exploration Geophysics: Magnetic and electrical methods, Continuous wavelet transform, Earth-Surface Processes, Water Science and Technology, Remote sensing, Ecology, Paleontology, Forestry, Geophysics, Magnetic field, Space and Planetary Science, Geomagnetism and Paleomagnetism: Magnetic anomaly modeling, Geology, Aeromagnetic survey
Abstract: International audience; A continuous wavelet technique has been recently introduced to analyze potential fields data. First, we summarize the theory, which primarily consists of interpreting potential fields via the properties of the upward continued derivative field. Using complex wavelets to analyze magnetic data gives an inverse scheme to find the depth and homogeneity degree of local homogeneous sources and the inclination of their magnetization vector. This is analytically applied on several local and extended synthetic magnetic sources. The application to other potential fields is also discussed. Then, profiles crossing dikes and faults are extracted from the recent high-resolution aeromagnetic survey of French Guiana and analyzed using complex one dimensional wavelets. Maps of estimated depth to sources and their magnetization inclination and homogeneity degree are proposed for a region between Cayenne and Kourou.
Published: 2000

22. Multiagent simulation of evolutive plate tectonics applied to the thermal evolution of the Earth

Author: C. Grigne, Clinton P. Conrad, Marc Parenthoën, M. Combes, Jacques Tisseau, S. Le Yaouanq, C. Tisseau, Laurent Husson, École Nationale d'Ingénieurs de Brest (ENIB), Centre Européen de Réalité Virtuelle (CERV), Laboratoire des sciences et techniques de l'information, de la communication et de la connaissance (UMR 3192) (Lab-STICC), Université européenne de Bretagne - European University of Brittany (UEB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Institut Brestois du Numérique et des Mathématiques (IBNM), Université de Brest (UBO)-Télécom Bretagne-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS), Domaines Océaniques (LDO), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Observatoire des Sciences de l'Univers-Institut d'écologie et environnement-Centre National de la Recherche Scientifique (CNRS), Systèmes Tectoniques, Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-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)-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), Department of Geology and Geophysics [Mānoa], University of Hawai‘i [Mānoa] (UHM), Lab-STICC_ENIB_CID_IHSEV, Laboratoire des sciences et techniques de l'information, de la communication et de la connaissance (Lab-STICC), École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Télécom Bretagne-Institut Brestois du Numérique et des Mathématiques (IBNM), Université de Brest (UBO)-Université européenne de Bretagne - European University of Brittany (UEB)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Télécom Bretagne-Institut Brestois du Numérique et des Mathématiques (IBNM), Université de Brest (UBO)-Université européenne de Bretagne - European University of Brittany (UEB)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Informatique des Systèmes Complexes (LISYC), École Nationale d'Ingénieurs de Brest (ENIB)-Université de Brest (UBO)-Institut Brestois du Numérique et des Mathématiques (IBNM), Université de Brest (UBO)-Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne), Université européenne de Bretagne - European University of Brittany (UEB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Télécom Bretagne-Institut Brestois du Numérique et des Mathématiques (IBNM), Université de Brest (UBO)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS), 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)-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), Université européenne de Bretagne - European University of Brittany (UEB)-École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Télécom Bretagne-Institut Brestois du Numérique et des Mathématiques (IBNM), Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-Université européenne de Bretagne - European University of Brittany (UEB)-École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Télécom Bretagne-Institut Brestois du Numérique et des Mathématiques (IBNM), and Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 010504 meteorology & atmospheric sciences, Mantle wedge, mobile plate boundaries, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, 010502 geochemistry & geophysics, 01 natural sciences, Physics::Geophysics, multiagent systems, mantle convection, Mantle convection, Geochemistry and Petrology, Lithosphere, Geothermal gradient, Plume tectonics, 0105 earth and related environmental sciences, Subduction, Geophysics, plate tectonics, Earth's thermal history, Plate tectonics, 13. Climate action, driving forces, Slab window, Geology
Abstract: International audience; [1] The feedback between plate tectonics and mantle convection controls the Earth's thermal evolution via the seafloor age distribution. We therefore designed the MACMA model to simulate time-dependent plate tectonics in a 2D cylindrical geometry with evolutive plate boundaries, based on multiagent systems that express thermal and mechanical interactions. We compute plate velocities using a local force balance and use explicit parameterizations to treat tectonic processes such as trench migration, subduction initiation, continental breakup and plate suturing. These implementations allow the model to update its geometry and thermal state at all times. Our approach has two goals: (1) to test how empirically- and analyticallydetermined rules for surface processes affect mantle and plate dynamics, and (2) to investigate how plate tectonics impact the thermal regime. Our predictions for driving forces, plate velocities and heat flux are in agreement with independent observations. Two time scales arise for the evolution of the heat flux: a linear long-term decrease and high-amplitude short-term fluctuations due to surface tectonics. We also obtain a plausible thermal history, with mantle temperature decreasing by less than 200 K over the last 3 Gyr. In addition, we show that on the long term, mantle viscosity is less thermally influential than tectonic processes such as continental breakup or subduction initiation, because Earth's cooling rate depends mainly on its ability to replace old insulating seafloor by young thin oceanic lithosphere. We infer that simple convective considerations alone cannot account for the nature of mantle heat loss and that tectonic processes dictate the thermal evolution of the Earth.
Published: 2012

23. Inversion of polar motion data: Chandler wobble, phase jumps, and geomagnetic jerks

Author: Jean-Louis Le Mouël, Dominique Gibert, Géosciences Rennes (GR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre Armoricain de Recherches en Environnement-Centre National de la Recherche Scientifique (CNRS), Institut de Physique du Globe de Paris (IPGP), 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), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre Armoricain de Recherches en Environnement-Centre National de la Recherche Scientifique (CNRS), and Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], Soil Science, Perturbation (astronomy), Aquatic Science, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Physics::Geophysics, Geochemistry and Petrology, Core–mantle boundary, Earth and Planetary Sciences (miscellaneous), phase jumps, polar motion, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, Physics, Ecology, Turbulence, Chandler wobble, Paleontology, Forestry, Geophysics, Geodesy, Secular variation, Earth's magnetic field, Amplitude, Space and Planetary Science, Physics::Space Physics, Polar motion
Abstract: International audience; We reconsider the analysis of the polar motion with a method totally different from the wavelet analysis used in previous papers. The total polar motion is represented as the sum of oscillating annual and Chandler terms whose amplitude and phase perturbations are inverted with a nonlinear simulated annealing method. The phase variations found in previous papers are confirmed with the huge phase change (—3p/2) occurring in the 19261942 period and another less important one (—p/3) in the 19701980 epoch. The best Chandler period, Tc, is found to be 434 ± 0.5 mean solar days. The epochs of significant phase changes found in the Chandler wobble are also those where important geomagnetic jerks occur in the secular variation of the geomagnetic field. Turbulent viscous friction produced by small-scale topography at the core-mantle boundary might be responsible for the observed phase jumps.
Published: 2008

24. Reply to comment by A. Fiori et al. on 'Asymptotic dispersion in 2D heterogeneous porous media determined by parallel numerical simulations'

Author: Jocelyne Erhel, Anthony Beaudoin, Jean Raynald de Dreuzy, Géosciences Rennes (GR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre Armoricain de Recherches en Environnement-Centre National de la Recherche Scientifique (CNRS), Simulations and Algorithms on Grids for Environment (SAGE), Inria Rennes – Bretagne Atlantique, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-SYSTÈMES LARGE ÉCHELLE (IRISA-D1), Institut de Recherche en Informatique et Systèmes Aléatoires (IRISA), Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université de Bretagne Sud (UBS)-École normale supérieure - Rennes (ENS Rennes)-Institut National de Recherche en Informatique et en Automatique (Inria)-Télécom Bretagne-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université de Bretagne Sud (UBS)-École normale supérieure - Rennes (ENS Rennes)-Institut National de Recherche en Informatique et en Automatique (Inria)-Télécom Bretagne-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche en Informatique et Systèmes Aléatoires (IRISA), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université de Bretagne Sud (UBS)-École normale supérieure - Rennes (ENS Rennes)-Télécom Bretagne-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS), Grid'5000, Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre Armoricain de Recherches en Environnement-Centre National de la Recherche Scientifique (CNRS), CentraleSupélec-Télécom Bretagne-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut National de Recherche en Informatique et en Automatique (Inria)-École normale supérieure - Rennes (ENS Rennes)-Université de Bretagne Sud (UBS)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-CentraleSupélec-Télécom Bretagne-Université de Rennes 1 (UR1), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-Institut de Recherche en Informatique et Systèmes Aléatoires (IRISA), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-École normale supérieure - Rennes (ENS Rennes)-Université de Bretagne Sud (UBS)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), and Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)
Subjects: 010504 meteorology & atmospheric sciences, [SDE.MCG]Environmental Sciences/Global Changes, Mathematical analysis, 0207 environmental engineering, 02 engineering and technology, Dispersion coefficient, 01 natural sciences, Dispersion (optics), Calculus, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, 020701 environmental engineering, Porous medium, 0105 earth and related environmental sciences, Water Science and Technology, Mathematics
Abstract: International audience; The comment by A. Fiori, G. Dagan, and I. Jankoviæ[Fiori et al., 2008] compares numerical results [de Dreuzy etal., 2007] on the longitudinal asymptotic dispersion coefficientto a self-consistent solution [Fiori et al., 2003]
Published: 2008

25. Kinematic analysis of the Pakuashan fault tip fold, west central Taiwan: Shortening rate and age of folding inception

Author: Manoj K. Jaiswal, Chien Ying Wang, Yu-Chang Chan, Martine Simoes, Ashok K. Singhvi, Jean Philippe Avouac, Yue-Gau Chen, Sylvain Bernard, 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-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Géosciences Rennes (GR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre Armoricain de Recherches en Environnement-Centre National de la Recherche Scientifique (CNRS), Department of Geosciences, National Taiwan University, Department of Geosciences, Planetary and Geosciences Division [Ahmedabad], Physical Research Laboratory [Ahmedabad] (PRL), Indian Space Research Organisation (ISRO)-Indian Space Research Organisation (ISRO), Department of Earth Sciences and Institute of Geophysics, National Central University [Taiwan] (NCU), Institute of Earth Sciences [Tapei] (IES Sinica), Academia Sinica, 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 de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre Armoricain de Recherches en Environnement-Centre National de la Recherche Scientifique (CNRS), Institut de Physique du Globe de Paris, Tectonics Observatory, and California Institute of Technology (CALTECH)
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Soil Science, Kinematics, Active fault, Aquatic Science, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), Thrust fault, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, Ecology, Anticline, Paleontology, Forestry, Fold (geology), Pure shear, Tectonics, Geophysics, Space and Planetary Science, Far East, Seismology, Geology
Abstract: International audience; The Pakuashan anticline is an active fault-tip fold that constitutes the frontalmost zone of deformation along the western piedmont of the Taiwan Range. Assessing seismic hazards associated with this fold and its contribution to crustal shortening across central Taiwan requires some understanding of the fold structure and growth rate. To address this, we surveyed the geometry of several deformed strata and geomorphic surfaces, which recorded different cumulative amounts of shortening. These units were dated to ages 2 ranging from ~ 19 ka to ~ 340 ka using Optical Stimulated Luminescence (OSL). We collected shallow seismic profiles and used previously published seismic profiles to constrain the deep structure of the fold. These data show that the anticline has formed as a result of pure shear with subsequent limb rotation. The cumulative shortening along the direction of tectonic transport (N118E) is estimated to be 1010 +/- 160 m. An analytical fold model derived from a sandbox experiment [Bernard, et al., in press] is used to model growth strata. This yields a shortening rate of 16.3 +/- 4.1 mm/yr and constrains the time of initiation of deformation to 62.2 +/- 9.6 ka. In addition, the kinematic model of Pakuashan is used to assess how tectonics, sedimentation and erosion have sculpted the present-day fold topography and morphology. The fold model, applied here for the first time on a natural example, appears promising in determining the kinematics of fault-tip folds in similar contexts and therefore in assessing seismic hazards on blind thrust faults.
Published: 2007

26. Slip rates on the Chelungpu and Chushiang thrust faults inferred from a deformed strath terrace along the Dungpuna river, west central Taiwan

Author: Jean Philippe Avouac, Yue-Gau Chen, Martine Simoes, 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), 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)-Centre Armoricain de Recherches en Environnement-Centre National de la Recherche Scientifique (CNRS), Tectonics Observatory, California Institute of Technology (CALTECH), Department of Geosciences, National Taiwan University [Taiwan] (NTU), Institut de Physique du Globe de Paris, Department of Geosciences, National Taiwan University, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), and Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre Armoricain de Recherches en Environnement-Centre National de la Recherche Scientifique (CNRS)
Subjects: Return period, Atmospheric Science, 010504 meteorology & atmospheric sciences, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Soil Science, Thrust, Slip (materials science), Aquatic Science, Induced seismicity, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), Thrust fault, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, Décollement, Ecology, Paleontology, Forestry, Foyer, Geophysics, Space and Planetary Science, Far East, Seismology, Geology
Abstract: International audience; The Chelungpu fault produced the September 1999 Mw=7.6 ChiChi earthquake, central Taiwan. The shortening rate accommodated by this structure, integrated over several seismic cycles, as well as its contribution to crustal shortening across the Taiwanese range has remained unresolved. To address this issue, we focus our study on the Chelungpu and Chushiang thrust faults within the southernmost portion of the ChiChi rupture area. Structural measurements and available seismic profiles are used to infer subsurface geometry of structures. The Chushiang and Chelungpu faults appear as two splay faults branching onto a common ramp that further north connects only to the Chelungpu surface trace. We survey a deformed strath terrace along the Dungpuna river, buried under a 11,540 +/- 309 cal yr old fill deposit. Given this age, the dip angles of the faults and the vertical throw determined from the offset of the strath across the surface fault traces, we estimate slip rates of 12.9 +/- 4.8 mm/yr and 2.9 +/- 1.6 mm/yr on the Chelungpu and Chushiang faults respectively. These yield a total shortening rate of 15.8 +/- 5.1 mm/yr to be absorbed on the common 2 decollement at depth within our study area. This total value is an upper bound on the slip rate on the Chelungpu fault further north, where the Chushiang fault disappears and transfers shortening to adjacent faults. Combining these results with the recently constrained shortening rates on the most frontal Changhua blind thrust reveals that all these frontal faults presently absorb most of the long-term horizontal shortening across the Taiwanese range. They thus stand as the major sources of seismic hazard in this heavily populated area. The return period of earthquakes similar to the ChiChi event over a ~80 km long stretch of the Western Foothills is estimated to be ~64 yr. This value is an underestimate because it assumes that all the faults locked during the interseismic period slip only during such large events. Comparison with historical seismicity suggests that episodic aseismic deformation might also play a major role in accommodating shortening
Published: 2007

27. Identification of sources of potential fields with the continuous wavelet transform: Two-dimensional ridgelet analysis

Author: Dominique Gibert, H. Boukerbout, Géosciences Rennes (GR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre Armoricain de Recherches en Environnement-Centre National de la Recherche Scientifique (CNRS), 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)-Centre Armoricain de Recherches en Environnement-Centre National de la Recherche Scientifique (CNRS)
Subjects: Discrete wavelet transform, Atmospheric Science, 010504 meteorology & atmospheric sciences, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], Stationary wavelet transform, potential field, Soil Science, Aquatic Science, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Wavelet packet decomposition, Wavelet, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), Complex wavelet transform, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, Ecology, Second-generation wavelet transform, wavelet analysis, Paleontology, Wavelet transform, Forestry, Geophysics, Space and Planetary Science, inverse problem, Harmonic wavelet transform, Algorithm, Geology
Abstract: 11 p.; International audience; A method based on the wavelet transform is used to localize the causative sources of potential field anomalies. In previous studies we introduced a particular class of analyzing wavelets belonging to the Poisson semigroup and such that the analyzed anomaly has a conical signature in the wavelet domain with its apex pointing at the location of the causative homogeneous source. In the present paper we apply this formalism to the special case of anomalies produced by elongated sources like faults and dikes. We show that, for this particular type of anomalies, the two-dimensional (2-D) wavelet transform corresponds to the ridgelet analysis and reduces to the 1-D wavelet transform applied in the Radon domain. A complete synthetic example is used to illustrate all steps of the analysis method: Radon transform of the anomaly map, selection of the Radon signature of elongated anomalies, complex wavelet transform, and source localization with the conical signature in the wavelet domain. The azimuthal filtering performed in the Radon domain leads to high signal-to-noise ratio and good localization of the sources both horizontally and vertically. The synthetic example is completed by an application of the method to a real aeromagnetic survey acquired in Britanny (France) and the results are compared with source depth determinations made with the Euler deconvolution method.
Published: 2006

28. Topographic characteristics of the submarine Taiwan orogen

Author: Char-Shine Liu, Niels Hovius, Dimitri Lague, L.A. Ramsey, Bullard Laboratories, University of Cambridge, Madingley Road, Cambridge CB3 0EZ, UK (BULLARD LABORATORIES,UNIVERSITY OF CAMBRIDGE), University of Cambridge [UK] (CAM), Department of Earth Sciences [Cambridge, UK], 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)-Centre Armoricain de Recherches en Environnement-Centre National de la Recherche Scientifique (CNRS), Institute of Oceanography [Taipei], National Taiwan University [Taiwan] (NTU), and Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre Armoricain de Recherches en Environnement-Centre National de la Recherche Scientifique (CNRS)
Subjects: Atmospheric Science, Turbidity current, 010504 meteorology & atmospheric sciences, Soil Science, Fluvial, Aquatic Science, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), Bathymetry, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, 14. Life underwater, Geomorphology, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, geography, geography.geographical_feature_category, Ecology, Bedrock, Paleontology, Submarine, Forestry, Landslide, Geophysics, 13. Climate action, Space and Planetary Science, Subaerial, Submarine pipeline, Geology
Abstract: International audience; A complete digital elevation and bathymetry model of Taiwan provides the opportunity to characterize the topography of an emerging mountain belt. The orogen appears to form a continuous wedge of constant slope extending from the subaerial peaks to the submarine basin. We compare submarine channel systems from the east coast of Taiwan with their subaerial counterparts and document a number of fundamental similarities between the two environments. The submarine channel systems form a dendritic network with distinct hillslopes and channels. There is minimal sediment input from the subaerial landscape and sea level changes are insignificant, suggesting that the submarine topography is sculpted by offshore processes alone.We implement a range of geomorphic criteria, widely applied to subaerial digital elevation models, and explore the erosional processes responsible for sculpting the submarine and subaerial environments. The headwaters of the submarine channels have steep, straight slopes and a low slope-area scaling exponent, reminiscent of subaerial headwaters that are dominated by bedrock landslides. The main trunk streams offshore have concave-up longitudinal profiles, extensive knickpoints, and a slope-area scaling exponent similar in form to the onshore fluvial domain. We compare the driving mechanisms of the likely offshore erosional processes, primarily debris flows and turbidity currents, with subaerial fluvial incision. The results have important implications for reading the geomorphic signals of the submarine and subaerial landscapes, for understanding the links between the onshore and offshore environments, and, more widely, for focusing the future research of the submarine slope
Published: 2006

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28 results on '"Géosciences Rennes (GR)"'

1. Core Complex Segmentation in North Aegean, A Dynamic View

2. From Long‐ to Short‐Term Inter‐Plate Coupling at the Subducted Carnegie Ridge Crest, Offshore Central Ecuador

3. Hydro‐Geomorphic Metrics for High Resolution Fluvial Landscape Analysis

4. Dynamic Contributions of Stratified Groundwater to Streams Controls Seasonal Variations of Streamwater Transit Times

5. Sharp Transition to Strongly Anomalous Transport in Unsaturated Porous Media

6. Constraining Plateau Uplift in Southern Africa by Combining Thermochronology, Sediment Flux, Topography, and Landscape Evolution Modeling

7. Long‐Period Astronomical Forcing of Westerlies' Strength in Central Asia During Miocene Climate Cooling

8. Retreat Pattern of Glaciers Controls the Occurrence of Turbidity Currents on High‐Latitude Fjord Deltas (Eastern Baffin Island)

9. How Do Continents Deform During Mantle Exhumation? Insights From the Northern Iberia Inverted Paleopassive Margin, Western Pyrenees (France)

10. Diachronous Growth of the Northern Tibetan Plateau Derived From Flexural Modeling

11. A Re‐evaluation of the Plenus Cold Event, and the Links Between CO2, Temperature, and Seawater Chemistry During OAE 2

12. Toward robust and predictive geodynamic modeling : the way forward in frictional plasticity

13. Experimental and Model‐Based Investigation of the Effect of the Free‐Surface Flow Regime on the Detection Threshold of Warm Water Inflows

14. Pre-Alpine (Variscan) Inheritance: A Key for the Location of the Future Valaisan Basin (Western Alps)

15. Neutrally buoyant tracers in hydrogeophysics: Field demonstration in fractured rock

16. Impact of saturation on dispersion and mixing in porous media: Photobleaching pulse injection experiments and shear‐enhanced mixing model

17. Connectivity, permeability, and channeling in randomly distributed and kinematically defined discrete fracture network models

18. Elastic Properties of Fractured Rock Masses With Frictional Properties and Power Law Fracture Size Distributions

19. Is the Dupuit assumption suitable for predicting the groundwater seepage area in hillslopes?

20. Does GRACE see the terrestrial water cycle 'intensifying'?

21. Identification of sources of potential fields with the continuous wavelet transform: Complex wavelets and application to aeromagnetic profiles in French Guiana

22. Multiagent simulation of evolutive plate tectonics applied to the thermal evolution of the Earth

23. Inversion of polar motion data: Chandler wobble, phase jumps, and geomagnetic jerks

24. Reply to comment by A. Fiori et al. on 'Asymptotic dispersion in 2D heterogeneous porous media determined by parallel numerical simulations'

25. Kinematic analysis of the Pakuashan fault tip fold, west central Taiwan: Shortening rate and age of folding inception

26. Slip rates on the Chelungpu and Chushiang thrust faults inferred from a deformed strath terrace along the Dungpuna river, west central Taiwan

27. Identification of sources of potential fields with the continuous wavelet transform: Two-dimensional ridgelet analysis

28. Topographic characteristics of the submarine Taiwan orogen

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28 results on '"Géosciences Rennes (GR)"'

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