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17 results on '"Pierre G. Valla"'

1. Modelling alpine glacier geometry and subglacial erosion patterns in response to contrasting climatic forcing

Author

Fabio Magrani, Pierre G. Valla, David Egholm, Institut für Geologie [Bern], Universität Bern [Bern] (UNIBE), 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), Department of Geoscience [Aarhus], Aarhus University [Aarhus], and ANR-18-MPGA-0006,MAGICLIM,Climat de montagne, glaciers et dynamique du paysage(2018)

Subjects
glacier geometry, 010504 meteorology & atmospheric sciences, Geography, Planning and Development, numerical modelling, 15. Life on land, 010502 geochemistry & geophysics, 01 natural sciences, climatic forcing, 13. Climate action, (paleo-)ELA, Earth and Planetary Sciences (miscellaneous), subglacial erosion patterns, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, ice dynamics, 0105 earth and related environmental sciences, Earth-Surface Processes
Abstract

Climate exerts a primary control on glacier mass balance, driving changes in ice flux, which affects basal sliding and subglacial erosion. Although past glacier reconstructions have been widely used as paleo-climate proxies, extracting quantitative temperature/precipitation data from paleo-glaciers is still challenging. The iSOSIA ice model was used over a synthetic landscape to quantitatively investigate the non-linear dependence of glacier geometry and ice dynamics on climate forcing, as well as to analyse how spatial patterns of subglacial erosion and erosion rates vary between the accumulation and ablation zones for different climatic settings. We performed 10 calibrated climatic scenarios with different combinations of temperature and precipitation rate in two separate sets of simulations [maintaining either same equilibrium line altitude (ELA) or same ice extent; SA and ST, respectively]. Our results reinforce the role of climate and the importance of ice flux in conditioning glacier geometry. In SA simulations, contrasting climatic scenarios showed a major influence on glacier length and thickness. In ST simulations, calibrated ELAs presented a variability of over 300 m in order to maintain similar ice extent, but showed reduced changes in glacier thickness. These results highlight the importance of ice flux to predict glacier geometry, when compared to the overall mass balance from an ELA estimate. Subglacial abrasion and quarrying showed notable differences between the accumulation and ablation zones for varying climatic forcing, with multimodal erosion distributions for increased precipitation/temperature, shifting erosion towards higher-elevation tributaries and connecting erosion patches in the ablation zone. Such trends highlight the role of subglacial hydrology and ice-bed contact (cavitation) in dictating patterns of subglacial erosion, while the depth of erosion relates closely to ice flux and climate inputs. Our results have potential implications for paleo-climate reconstructions based on glacier geometry and provide insights on how subglacial erosion can help estimate paleo-climatic conditions from paleo-glacial records.

Published
2022
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2. Evaluating post-glacial bedrock erosion and surface exposure duration by coupling in situ optically stimulated luminescence and 10Be dating

Author

R.H. Biswas, Benjamin Lehmann, Pierre G. Valla, Frédéric Herman, and Georgina E. King

Subjects
010506 paleontology, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Optically stimulated luminescence, Bedrock, Glacier, 15. Life on land, 01 natural sciences, Geophysics, Surface exposure dating, 13. Climate action, Erosion, Glacial period, Cosmogenic nuclide, Quaternary, Geomorphology, Geology, 0105 earth and related environmental sciences, Earth-Surface Processes
Abstract

Assessing the impact of Quaternary glaciation at the Earth's surface implies an understanding of the long-term evolution of alpine landscapes. In particular, it requires simultaneous quantification of the impact of climate variability on past glacier fluctuations and on bedrock erosion. Here we present a new approach for evaluating post-glacial bedrock surface erosion in mountainous environments by combining terrestrial cosmogenic nuclide 10Be (TCN) and optically stimulated luminescence (OSL) surface exposure dating. Using a numerical approach, we show how it is possible to simultaneously invert bedrock OSL signals and 10Be concentrations into quantitative estimates of post-glacial exposure duration and bedrock surface erosion. By exploiting the fact that OSL and TCN data are integrated over different timescales, this approach can be used to estimate how bedrock erosion rates vary spatially and temporally since glacier retreat in an alpine environment.

Published
2019
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3. How Climate, Uplift and Erosion Shaped the Alpine Topography

Author

Pietro Sternai, Pierre G. Valla, Matthew Fox, 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), Università degli Studi di Milano-Bicocca = University of Milano-Bicocca (UNIMIB), University College of London [London] (UCL), ANR-18-MPGA-0006,MAGICLIM,Climat de montagne, glaciers et dynamique du paysage(2018), Valla, P, Sternai, P, Fox, M, Università degli Studi di Milano-Bicocca [Milano] (UNIMIB), and Department of Earth Sciences, University College London

Subjects
010504 meteorology & atmospheric sciences, Mountain geodynamics, Climate, geochronology, modeling, 15. Life on land, 010502 geochemistry & geophysics, topographic evolution, 01 natural sciences, erosion & sediment yield, Glaciation, Erosion, 13. Climate action, Geochemistry and Petrology, [SDE]Environmental Sciences, Earth and Planetary Sciences (miscellaneous), climate and glaciations, Mountain geodynamic, Geomorphology, Geology, geodetic uplift, 0105 earth and related environmental sciences
Abstract

International audience; Decades of scientific research on the European Alps have helped quantify the vast array of processes that shape the Earth’s surface. Patterns in rock exhumation, surface erosion and topographic changes can be compared to sediment yields preserved in sedimentary basins or collected from modern rivers. Erosion-driven isostatic uplift explains up to ~50% of the modern geodetic rock uplift rates; the remaining uplift reveals the importance of internal processes (tectonics, deep-seated geodynamics) and external processes (glacial rebound, topographic changes). We highlight recent methodological and conceptual developments that have contributed to our present view of the European Alps, and we provide suggestions on how to fill the gaps in our understanding.

Published
2021
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4. Late-Pleistocene catchment-wide denudation patterns across the European Alps

Author

Hella Wittmann, Naki Akçar, Christoph Glotzbach, Pierre G. Valla, Jean L. Dixon, Fritz Schlunegger, Stéphane Molliex, Kevin Norton, Bernhard Salcher, Florian Kober, Kristina Hippe, Romain Delunel, Marcus Christl, Institute of Geological Sciences [Bern], University of Bern, 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), Montana State University (MSU), Institut für Geowissenschaften [Tübingen], Eberhard Karls Universität Tübingen = Eberhard Karls University of Tuebingen, Ion Beam Physics [ETH Zürich], Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), National Cooperative for the Disposal of Radioactive Waste (Nagra), Laboratoire Géosciences Océan (LGO), Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Victoria University of Wellington, Universität Salzburg, GeoForschungsZentrum - Helmholtz-Zentrum Potsdam (GFZ), Université de Bretagne Sud (UBS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), and ANR-18-MPGA-0006,MAGICLIM,Climat de montagne, glaciers et dynamique du paysage(2018)

Subjects
010504 meteorology & atmospheric sciences, Pleistocene, Geomorphology, Denudation rates, Cosmogenic nuclides, Catchment, Data compilation, Surface uplift, European Alps, Lithology, Fluvial, 15. Life on land, 010502 geochemistry & geophysics, 01 natural sciences, Denudation, 13. Climate action, [SDU]Sciences of the Universe [physics], [SDE]Environmental Sciences, General Earth and Planetary Sciences, Common spatial pattern, Physical geography, Glacial period, Cosmogenic nuclide, Surface runoff, Geology, 550 Earth sciences & geology, 0105 earth and related environmental sciences
Abstract

We compile detrital 10Be concentrations of Alpine rivers, representing the denudation rates pattern for 375 catchments across the entire European Alps. Using a homogeneized framework, we employ state-of-the-art techniques for inverting in-situ 10Be concentrations into denudation rates. From our compilation, we find that (i) while lithologic properties and precipitation/runoff do influence erosion mechanisms and rates at the scale of individual catchments and in some specific Alpine regions, such controls do not directly stand for the entire Alps, (ii) as also previously suggested, catchment-wide denudation rates across the entire European Alps closely follow first-order Alpine topographic metrics at the scale of individual catchments or selected Alpine sub-regions. However, in addition to previous local-scale studies conducted in the European Alps, our large-scale compilation highlights a functional relationship between catchment-wide denudation and mean catchment slope angle. Catchment-wide denudation positively correlates with mean catchment slope up to a threshold angle (25–30°). Above this threshold, any correlation between catchment-wide denudation and slope as well as other catchment metrics breaks apart. We can reconcile these systematic patterns by proposing a regional erosion model based on diffusive-transport laws for catchments located below the slope threshold angle. In oversteepened catchments situated above-threshold slopes, erosion is stochastic in nature, as glacial carving likely caused a partial decoupling between hillslope and fluvial domains with complex topographic relationships and sediment connectivity patterns. Finally, we identify a first-order positive relationship between modern geodetic rock uplift and catchment-wide denudation for the European Alps. The observed spatial pattern is highly variable and possibly reflects the surface response to deep geodynamic mechanisms prevailing in the different Alpine regions. We conclude that today's topography and geomorphic features of the entire Alps are the result of a millenial-scale geomorphic response to past glacial processes and active rock uplift, highlighting a link between external and internal drivers for mountain erosion. ISSN:0012-8252 ISSN:1872-6828

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

Author

Yuan-Ze Zhang, Cécile Gautheron, Philippe Hervé Leloup, Xiong Ou, Malwina San José, Cao Kai, Guocan Wang, Mélanie Balvay, Audrey Margirier, Pierre G. Valla, Peter van der Beek, Anne Replumaz, Institut des Sciences de la Terre (ISTerre), Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Gustave Eiffel-Université Grenoble Alpes (UGA), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Grenoble Alpes (UGA)-Université Gustave Eiffel-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry]), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement [Lyon] (LGL-TPE), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF), German Research Centre for Geosciences - Helmholtz-Centre Potsdam (GFZ), Géosciences Paris Saclay (GEOPS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut de Physique du Globe de Paris (IPGP), 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), State Key Laboratory of Geological Processes and Mineral Resources [Wuhan] (GPMR), China University of Geosciences [Wuham] (CUG), Laboratoire de Géodynamique des Chaines Alpines (LGCA), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut des Sciences de la Terre (ISTerre), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR), Centre National de la Recherche Scientifique (CNRS)-Université de La Réunion (UR)-Université Paris Diderot - Paris 7 (UPD7)-IPG PARIS-Institut national des sciences de l'Univers (INSU - CNRS), China University of Geosciences [Wuhan] (CUG), and 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)

Subjects
[SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, geography, Plateau, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Massif, 15. Life on land, Late Miocene, 010502 geochemistry & geophysics, 01 natural sciences, Mekong Valley, Thermochronology, Paleontology, Tectonics, Geophysics, Tectonic uplift, 13. Climate action, Geochemistry and Petrology, [SDU]Sciences of the Universe [physics], [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, Quaternary, Geology, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract

International audience; The incision history of the Three Rivers (Salween, Mekong, and Yangtze) region in the Southeast Tibetan Plateau has been linked to both tectonic and climatic controls. In this study, we report new apatite (U‐Th)/He and fission‐track thermochronology data from the >6,000‐m‐high Kawagebo massif, which forms the edge of the high plateau on the western flank of the steepened knickzone reach of the middle Mekong River valley. Thermal‐history modeling of a thermochronological age‐elevation profile shows rapid cooling since ~1.5 Ma and suggests a mean Quaternary exhumation rate of >1 km/Myr at the valley bottom. The amount of Quaternary exhumation is too high to be caused by fluvial incision alone and requires additional tectonic uplift. Comparing our data from the western flank of the Mekong River valley with published data from the eastern flank shows differential exhumation across the valley in the late Miocene, with the western flank undergoing more exhumation, but relatively uniform exhumation in the Quaternary. We relate rapid exhumation since the late Miocene on the western flank of the Mekong valley and the high topography of the Kawagebo massif to localized tectonic uplift associated with a restraining (left stepping) overstep between the still‐active right‐lateral Parlung and Zhongdian strike‐slip faults. The pattern of river steepness index across the knickzone also indicates that it results from locally focused uplift. Our results demonstrate the importance of detailed thermochronologic studies in this very active region to constrain the complex multiphase tectonic history before invoking any potential climatic forcing of river incision.

Published
2020
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6. Cretaceous and late Cenozoic uplift of a Variscan Massif: The case of the French Massif Central studied through low-temperature thermochronometry

Author

Massimiliano Zattin, Kevin Manchuel, Olivier Bellier, Maria Laura Balestrieri, Cécile Gautheron, Pierre G. Valla, Claudio Faccenna, Rosella Pinna-Jamme, Valerio Olivetti, Vincent Godard, Olivetti, V., Balestrieri, M. L., Godard, V., Bellier, O., Gautheron, C., Valla, P. G., Zattin, M., Faccenna, C., Pinna-Jamme, R., and Manchuel, K.

Subjects
Topography, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Geology, Thermochronology, Massif, 15. Life on land, 010502 geochemistry & geophysics, 01 natural sciences, Mantle (geology), Cretaceous, Massif Central, Paleontology, Upwelling, Extensional tectonics, Foreland basin, Cenozoic, 0105 earth and related environmental sciences
Abstract

Located in the foreland domain of the Alpine and Pyrenean mountain belts, the French Massif Central presents enigmatic topographic features—reaching elevations of ∼1700 m above sea level and ∼1000 m of relief—that did not originate from Alpine compressional nor from extensional tectonics. Similar to other Variscan domains in Europe, such as the Bohemian, Rhenish, and Vosges/Black Forest Massifs, a Cenozoic uplift has been postulated, although its timing and quantification remain largely unconstrained. With respect to the other Variscan Massifs, the French Massif Central is wider and higher and shows a more intense late Cenozoic volcanism, suggesting that deep-seated processes have been more intense. In this study, apatite fission-track and (U-Th)/He thermochronometry were applied to investigate the long-term topographic evolution of the Massif Central. Our new thermochronological data come from the eastern flank of the massif, where sampling profiles ran from the high-elevation region down to the Rhône River valley floor with a total elevation profile of 1200 m. Age-elevation relationships, mean track-length distributions, and thermal modeling indicate a two-step cooling history: (1) a first exhumation event, already detected through previously published thermochronology data, with an onset time during the Cretaceous, and (2) a more recent Cenozoic phase that is resolved from our data, with a likely post-Eocene onset. This second erosional event is associated with relief formation and valley incision possibly induced by a long-wavelength domal uplift supported by mantle upwelling.

Published
2020
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7. Postglacial erosion of bedrock surfaces and deglaciation timing: New insights from the Mont Blanc massif (western Alps)

Author

Marcus Christl, Olivia Steinemann, Benjamin Lehmann, Frédéric Herman, Susan Ivy-Ochs, Georgina E. King, Pierre G. Valla, R.H. Biswas, Institut des Dynamiques de la Surface Terrestre [Lausanne] (IDYST), Université de Lausanne (UNIL), 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), Institute of Geological Sciences [Bern], University of Bern, Ion Beam Physics [ETH Zürich], Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Université de Lausanne = University of Lausanne (UNIL), and Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])

Subjects
geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Bedrock, Geochemistry, Geology, 15. Life on land, 010502 geochemistry & geophysics, Mont blanc massif, 01 natural sciences, 13. Climate action, [SDE]Environmental Sciences, Deglaciation, Erosion, 0105 earth and related environmental sciences
Abstract

Since the Last Glacial Maximum, ∼20 k.y. ago, Alpine glaciers have retreated and thinned. This transition exposed bare bedrock surfaces that could then be eroded by a combination of debuttressing or local frost cracking and weathering. Quantification of the respective contributions of these processes is necessary to understand the links between long-term climate and erosion in mountains. Here, we quantified the erosion histories of postglacial exposed bedrock in glacial valleys. Combining optically stimulated luminescence and terrestrial cosmogenic nuclide (TCN) surface exposure dating, we estimated the erosion rate of bedrock surfaces at time scales from 101 to 104 yr. Bedrock surfaces sampled from the flanks of the Mer de Glace (Mont Blanc massif, European Alps) revealed erosion rates that vary from 3.5 ± 1.2 ⋅ 10−3 mm/yr to 4.3 ± 0.6 mm/yr over ∼500 m of elevation, with a negative correlation between erosion rate and elevation. The observed spatial variation in erosion rates, and their high values, reflect morphometric (elevation and surface slope) and climatic (temperature and snow cover) controls. Furthermore, the derived erosion rates can be used to correct the timing of deglaciation based on TCN data, potentially suggesting very rapid ice thinning during the Gschnitz stadial.

Published
2019
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8. Present-day uplift of the European Alps: Evaluating mechanisms and models of their relative contributions

Author

Pierre G. Valla, Laurent Jolivet, Carole Petit, Sean D. Willett, Sébastien Castelltort, Pietro Sternai, Andrea Walpersdorf, Jean-Mathieu Nocquet, Thorsten W. Becker, Laurent Husson, Giorgio Spada, Christian Sue, Andrea Di Giulio, Enrico Serpelloni, Claudio Faccenna, Sternai, Pietro, Sue, Christian, Husson, Laurent, Serpelloni, Enrico, Becker, Thorsten W., Willett, Sean D., Faccenna, Claudio, Di Giulio, Andrea, Spada, Giorgio, Jolivet, Laurent, Valla, Pierre, Petit, Carole, Nocquet, Jean-Mathieu, Walpersdorf, Andrea, Castelltort, Sébastien, Laboratoire Chrono-environnement - CNRS - UBFC (UMR 6249) (LCE), Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC), Institut des Sciences de la Terre (ISTerre), Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Istituto Nazionale di Geofisica e Vulcanologia - Sezione di Roma (INGV), Istituto Nazionale di Geofisica e Vulcanologia, Department of Earth Sciences [Swiss Federal Institute of Technology - ETH Zürich] (D-ERDW), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Laboratory of Experimental Tectonics, Università degli Studi Roma Tre, Dipartimento di Scienze della Terra e dell'Ambiente [Pavia], Università degli Studi di Pavia, Dipartimento di Scienze di Base e Fondamenti, Università degli Studi di Urbino 'Carlo Bo', Institut des Sciences de la Terre de Paris (iSTeP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Géoazur (GEOAZUR 6526), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-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)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), University of Geneva, Laboratoire Chrono-environnement - UFC (UMR 6249) (LCE), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF), Department of Earth Sciences [ETH Zürich] (D-ERDW), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology in Zürich [Zürich] (ETH Zürich), Università di Pavia, Laboratoire de Géodynamique des Chaines Alpines (LGCA), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut des Sciences de la Terre (ISTerre), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR), Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Géophysique Interne et Tectonophysique (LGIT), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Laboratoire Central des Ponts et Chaussées (LCPC)-Institut des Sciences de la Terre (ISTerre), Sternai, P, Sue, C, Husson, L, Serpelloni, E, Becker, T, Willett, S, Faccenna, C, Di Giulio, A, Spada, G, Jolivet, L, Valla, P, Petit, C, Nocquet, J, Walpersdorf, A, and Castelltort, S

Subjects
European Alps Vertical displacement rate Deglaciation Erosion Lithospheric structural changes Mantle flow, Vertical displacement rate, 010504 meteorology & atmospheric sciences, European Alp, Present day, 010502 geochemistry & geophysics, 01 natural sciences, Paleontology, Lithospheric structural changes, Mantle convection, Lithosphere, Deglaciation, ddc:550, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, Mantle flow, 15. Life on land, Lithospheric structural change, Tectonics, 13. Climate action, Erosion, Slab, General Earth and Planetary Sciences, Upwelling, European Alps, Earth and Planetary Sciences (all), Surface mass, Geology
Abstract

Recent measurements of surface vertical displacements of the European Alps show a correlation between vertical velocities and topographic features, with widespread uplift at rates of up to ~2–2.5 mm/a in the North-Western and Central Alps, and ~1 mm/a across a continuous region from the Eastern to the South-Western Alps. Such a rock uplift rate pattern is at odds with the horizontal velocity field, characterized by shortening and crustal thickening in the Eastern Alps and very limited deformation in the Central and Western Alps. Proposed mechanisms of rock uplift rate include isostatic response to the last deglaciation, long-term erosion, detachment of the Western Alpine slab, as well as lithospheric and surface deflection due to mantle convection. Here, we assess previous work and present new estimates of the contributions from these mechanisms. Given the large range of model estimates, the isostatic adjustment to deglaciation and erosion are sufficient to explain the full observed rate of uplift in the Eastern Alps, which, if correct, would preclude a contribution from horizontal shortening and crustal thickening. Alternatively, uplift is a partitioned response to a range of mechanisms. In the Central and Western Alps, the lithospheric adjustment to deglaciation and erosion likely accounts for roughly half of the rock uplift rate, which points to a noticeable contribution by mantle-related processes such as detachment of the European slab and/or asthenospheric upwelling. While it is difficult to independently constrain the patterns and magnitude of mantle contributions to ongoing Alpine vertical displacements at present, future data should provide additional insights. Regardless, interacting tectonic and surface mass redistribution processes, rather than an individual forcing, best explain ongoing Alpine elevation changes.

Published
2019
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9. Glacial overdeepenings in the Swiss Alps and foreland: Spatial distribution and morphometrics

Author

Pierre G. Valla, Natacha Gribenski, Fabio Magrani, Elena Serra, Institute of Geological Sciences [Bern], University of Bern, Institut des Sciences de la Terre (ISTerre), Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Gustave Eiffel-Université Grenoble Alpes (UGA), and Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Grenoble Alpes (UGA)-Université Gustave Eiffel-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])

Subjects
010506 paleontology, Archeology, Global and Planetary Change, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Landform, Bedrock, Fluvial, Geology, Glacier, 15. Life on land, 01 natural sciences, Headward erosion, [SDU]Sciences of the Universe [physics], 13. Climate action, [SDE]Environmental Sciences, Glacial period, Meltwater, Geomorphology, Foreland basin, Ecology, Evolution, Behavior and Systematics, 0105 earth and related environmental sciences
Abstract

International audience; Overdeepenings (ODs) are erosional features that have been excavated below the regional sea/fluvial base level to produce closed topographic basins. Accessing bedrock topography and OD volume is often challenging. Hence, despite constituting major landscape features and being widespread in (paleo-) glaciated regions, ODs have been overlooked and the subglacial processes involved in their evolution have remained debated. In the Swiss Alpine foreland and valleys, ODs are commonly found filled with water or large volumes of sediment. Using a GIS-Matlab approach based on topographic datasets and bedrock contour-curves, we mapped the spatial distribution of ODs in Switzerland and adjacent areas in the ice-free Alpine areas. The majority of the mapped ODs occurs in very-low bedrock erosional resistance , where ODs are larger, wider and shallower than in medium to high bedrock erosional resistance domains, evidencing a strong lithological control on OD geometry. Longitudinal asymmetry and hyp-sometric integral suggest a dominance of quarrying during OD evolution and, for selected glacial catchments, headward erosion propagation or high sediment evacuation efficiency. OD surface data (surface and length) can be tentatively used for extracting OD subsurface metrics (depths, nested valleys and first-order volume estimates). Our data seem to indicate that ODs may initiate as multiple small nested valleys and progress to a single and connected depression. Transversal cross-sections also suggest a negative feedback between the erosion potential for deep carving and the presence of low-resistance bedrock, where subglacial meltwater infiltration could have played a key role in OD evolution. Although insightful relationships have been evidenced for ODs in the Swiss Alps and foreland, we have also observed a high spatial variability in key OD metrics such as surface area and depth. This results in general (first-order) interpretations at regional scale, but currently prevent to quantitatively constrain physical subglacial processes at their origin. Comparisons with existing OD datasets under present-day ice (Greenland, Antarctica and modern Swiss glaciers) place our results in a broader context and allow a step forward in our understanding of the complex patterns and mechanisms of (sub-)glacial erosion and resulting landforms.

Published
2020
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10. Pedo-sedimentary constituents as paleoenvironmental proxies in the Sudano-Sahelian belt during the Late Quaternary (southwestern Chad Basin)

Author

David Sebag, Nathalie Diaz, Pierre Deschamps, Geoffroy de Saulieu, Yannick Garcin, Pierre G. Valla, Eric P. Verrecchia, Georgina E. King, Frédéric Herman, Fabienne Dietrich, Alain Durand, Morphodynamique Continentale et Côtière (M2C), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS), Hydrosciences Montpellier (HSM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), University of Bern, Institut des Sciences de la Terre (ISTerre), Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Laboratoire de Chimie Physique Macromoléculaire (LCPM), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Institute of Earth and Environmental Science [Potsdam], University of Potsdam = Universität Potsdam, Patrimoines Locaux et Gouvernance (PALOC), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD), Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Research School of Earth Sciences [Canberra] (RSES), Australian National University (ANU), Faculté de Géosciences et Environnement, Université de Lausanne = University of Lausanne (UNIL), Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Lorraine (UL), University of Potsdam, Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Collège de France (CdF (institution))-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA), Université de Lausanne (UNIL), Centre National de la Recherche Scientifique (CNRS)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU), Institut de Recherche pour le Développement (IRD)-Université Montpellier 2 - Sciences et Techniques (UM2)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Collège de France (CdF)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Institut National de la Recherche Agronomique (INRA), and Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD)-Université Montpellier 2 - Sciences et Techniques (UM2)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)

Subjects
010506 paleontology, Archeology, 010504 meteorology & atmospheric sciences, [SHS.ARCHEO]Humanities and Social Sciences/Archaeology and Prehistory, EAU DU SOL, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, PALEOENVIRONNEMENT, Vertisol, 01 natural sciences, DATATION, law.invention, chemistry.chemical_compound, VERTISOL, law, ddc:550, CARBONATE, Radiocarbon dating, Ecology, Evolution, Behavior and Systematics, 0105 earth and related environmental sciences, QUATERNAIRE, Global and Planetary Change, PEDOGENESE, Soil organic matter, Geology, Last Glacial Maximum, 15. Life on land, ISOTOPE RADIOACTIF, Pedogenesis, chemistry, PALEOCLIMAT, 13. Climate action, LUMINESCENCE, [SDE]Environmental Sciences, Carbonate, Sedimentary rock, Institut für Geowissenschaften, Physical geography, MOUSSON, Quaternary
Abstract

Climate and environmental changes since the Last Glacial Maximum in the tropical zone of West Africa are usually inferred from marine and continental records. In this study, the potential of carbonate pedo-sedimentary geosystems, i.e. Vertisol relics, to record paleoenvironmental changes in the southwestern part of Chad Basin are investigated. A multi-dating approach was applied on different pedogenic organo-mineral constituents. Optically stimulated luminescence (OSL) dating was performed on the soil K-rich feldspars and was combined with radiocarbon dating on both the inorganic (C-14(inorg)) and organic carbon (C-14(org)) soil fractions. Three main pedo-sedimentary processes were assessed over the last 20 ka BP: 1) the soil parent material deposition, from 18 ka to 12 ka BP (OSL), 2) the soil organic matter integration, from 11 cal ka to 8 cal ka BP (C-14(org)), and 3) the pedogenic carbonate nodule precipitation, from 7 cal ka to 5 cal ka BP (C-14(inorg)). These processes correlate well with the Chad Basin stratigraphy and West African records and are shown to be related to significant changes in the soil water balance responding to the evolution of continental hydrology during the Late Quaternary. The last phase affecting the Vertisol relics is the increase of erosion, which is hypothesized to be due to a decrease of the vegetation cover triggered by (i) the onset of drier conditions, possibly strengthened by (ii) anthropogenic pressure. Archaeological data from Far North Cameroon and northern Nigeria, as well as sedimentation times in Lake Tilla (northeastern Nigeria), were used to test these relationships. The increase of erosion is suggested to possibly occur between c. 3 cal ka and 1 cal ka BP. Finally, satellite images revealed similar geosystems all along the Sudano-Sahelian belt, and initial C-14(inorg) ages of the samples collected in four sites gave similar ages to those reported in this study. Consequently, the carbonate pedo-sedimentary geosystems are valuable continental paleoenvironmental archives and soil water balance proxies of the semiarid tropics of West Africa. (C) 2018 Elsevier Ltd. All rights reserved.

Published
2018
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11. Spatial variability of 10 Be-derived erosion rates across the southern Peninsular Indian escarpment: A key to landscape evolution across passive margins

Author

Sanjay Kumar Mandal, Jean-Pierre Burg, Pierre G. Valla, Maarten Lupker, Marcus Christl, and Negar Haghipour

Subjects
geography, geography.geographical_feature_category, Bedrock, Escarpment, 15. Life on land, Tectonics, Geophysics, Space and Planetary Science, Geochemistry and Petrology, Passive margin, Earth and Planetary Sciences (miscellaneous), Erosion, Spatial variability, Cosmogenic nuclide, Geomorphology, Channel (geography), Geology
Abstract

The persistence of significant topography in ancient, tectonically inactive orogenic belts remains one of the outstanding questions in geomorphology. In southern Peninsular India, the impressive topographic relief of the Western Ghat Mountains in tectonic quiescence since at least ca. 65 Ma has raised important questions concerning the long-term mechanism of topographic evolution. Quantifying the distribution of erosion in space and time is critical to understanding landscape evolution. Although the long-term erosion rates are reasonably well known, the short-term erosion rates and the relative importance of factors controlling erosion in southern Peninsular India are less well constrained. We present a new suite of catchment-averaged and local erosion rates using in situ produced 10Be concentrations in river sediments and exposed bedrock samples in southern Peninsular India. Catchment-averaged erosion rates vary from 9.6 ± 0.8 m Ma − 1 in the highlands to 114.3 ± 13.8 m Ma − 1 on the escarpment side. Bedrock erosion rates range from 2.4 ± 0.2 m Ma − 1 in the ridge-top to 143.4 ± 25.4 m Ma − 1 in active channel beds of the highlands. Catchment-averaged erosion rates derived from the across-escarpment, westward-draining catchments are significantly higher than those derived from the eastward-draining, over highland catchments. The difference indicates that long-term down-wearing of the highland proceeds at lower rates than in the escarpment zones. Catchment-averaged erosion rates are moderately correlated with mean hillslope angles and local relief whereas they are strongly correlated with catchment-averaged channel steepness index. This suggests that topographic steepness is the major control on the spatial variability of erosion while strong rainfall gradient is of minor importance in this area. 10Be-derived average erosion rates in highlands are consistent with previous long-term erosion rate estimated from thermochronometry. These results collectively point to large-scale steady-state topography, only decaying slowly with time. Steady state likely reflects the balance between erosion and isostatically driven uplift of the southern Peninsular India.

Published
2015
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12. Late-Cenozoic relief evolution under evolving climate: A review

Author

fred Herman, Pierre G. Valla, and Jean-Daniel Champagnac

Subjects
Topographic relief, Frost weathering, Climate change, 15. Life on land, Spatial distribution, Geophysics, 13. Climate action, Erosion, sense organs, Glacial period, Physical geography, Cosmogenic nuclide, Cenozoic, Geomorphology, Geology, Earth-Surface Processes
Abstract

The present review paper is an attempt to summarize quantitative evidence of Late Cenozoic changes in topographic relief. Different meanings of the word “relief”, as it is commonly used, and detail the metrics used to quantify it. We then specify methodological tools used to quantify relief change (primarily low-temperature thermochronometry and terrestrial cosmogenic nuclides), and analyze published evidence for different regions. Our review first shows that relief changes and rates of changes are more important at mid-, than high- or low-latitudes, and appear to be insensitive to mean precipitation rates. It also show that relief change is positive (relief increases) in most of the reported cases (~ 80%). We subsequently define two functional relationships between relief and erosion, depending on the chosen definition of relief, and propose a conceptual model of landscape memory. We conclude, following others, that erosion rates depend non-linearly on relief evolution, itself being a function of the spatial distribution and rates of erosion. The relief increases documented in this review may be to erosion rate increases during the same timescales. Lastly, we discuss the importance of glacial and periglacial processes on Late Cenozoic relief and erosion rate changes, and stress the importance of frost shattering and glacial erosion at mid- and high-latitudes.

Published
2014
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13. Spatial and temporal variations of glacial erosion in the RhÔne valley (Swiss Alps): Insights from numerical modeling

Author

Pierre G. Valla, Pietro Sternai, Jean-Daniel Champagnac, Frédéric Herman, Institut des Sciences de la Terre d'Orléans - UMR7327 (ISTO), Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Geological Institute [ETH Zürich], Department of Earth Sciences [Swiss Federal Institute of Technology - ETH Zürich] (D-ERDW), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich)- Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Institute of Earth Sciences, Université de Lausanne (UNIL), Sternai, P, Herman, F, Valla, P, and Champagnac, J

Subjects
010504 meteorology & atmospheric sciences, Glacial landform, [SDE.MCG]Environmental Sciences/Global Changes, Numerical modeling, Fluvial, 010502 geochemistry & geophysics, 01 natural sciences, glacial erosion, sediment yield, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), Glacial period, Geomorphology, Geophysic, 0105 earth and related environmental sciences, [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, geography, geography.geographical_feature_category, Landform, 15. Life on land, U-shaped valley, Geophysics, numerical modeling, Space and Planetary Science, Interglacial, Erosion, topographic relief, Geology
Abstract

Pietro Sternai : Now at: the Institut desSciences de laTerre d'Orléans - (ISTO), University of Orléans,France. Tel.: 33 631910242. E-mail addresses: pietro.sternai@univ-orleans.fr, pietro.sternai@erdw.ethz.ch; International audience; The present-day topography of the European Alps shows evidence of intense glacial reshaping. However, significant questions regarding Alpine landscape evolution during glaciations still persist. In this study, we focus on the Rhône valley (Swiss Alps), and use a numerical model to estimate patterns and magnitudes of glacial erosion. Comparing modeling results on a reconstructed pre-glacial topography and the present-day landforms, we find that the landscape response to glaciation is more complex than a simple "buzzsaw" mechanism (by which glacial erosion sets the height of mountain ranges) or increase of relief due to localized valley incision. Instead, glacial erosion propagates headward as the landforms evolve from a fluvial to a glacial state, leading to an initial increase of local relief followed by subsequent erosion at high elevations. It has also been proposed that the mid-Pleistocene climatic transition of glacial/interglacial oscillations from periods of 40 kyr (with symmetric shapes) to periods of 100 kyr (with asymmetric shapes) promoted glacial erosion within the Alps. Although this change of climate periodicity may have contributed to enhance glacial erosion, our results suggest that other factors such as an increase in rock uplift and/or progressive climate cooling are required to explain enhanced glacial carving at View the MathML source∼1Ma.

Published
2013
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14. Significant increase in relief of the European Alps during mid-Pleistocene glaciations

Author

Pierre G. Valla, Peter van der Beek, David L. Shuster, Tectonique reliefs et bassins, Institut des Sciences de la Terre (ISTerre), Université Joseph Fourier - Grenoble 1 (UJF)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-PRES Université de Grenoble-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-PRES Université de Grenoble-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Berkeley Geochronology Center (BGC), and US National Science Foundation (EAR-0720225 grant to D.L.S.) Ann and Gordon Getty Foundation France-Berkeley Fund

Subjects
010504 meteorology & atmospheric sciences, Pleistocene, Structural geology, Geomorphology, tectonics and geodynamics, 15. Life on land, 010502 geochemistry & geophysics, 01 natural sciences, U-shaped valley, 13. Climate action, General Earth and Planetary Sciences, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, Physical geography, Glacial period, Geology, 0105 earth and related environmental sciences
Abstract

International audience; Some of Earth's greatest relief occurs where glacial processes act on mountain topography1, 2. This dramatic landscape is thought to be an imprint of Pleistocene glaciations3, 4. However, whether the net effect of glacial erosion on mountains is to increase5, 6, 7 or decrease8, 9, 10 relief remains disputed. It has been suggested that in the European Alps, the onset of widespread glaciation since the mid-Pleistocene climate transition11 led to the growth of large, long-lived and strongly erosive alpine glaciers12, 13 that profoundly influenced topography14. Here we use 4He/3He thermochronometry15 and thermal-kinematic models to show that the Rhône Valley in Switzerland deepened by about 1-1.5 km over the past one million years. Our results indicate that while the valley was incised and back-cut, high-altitude areas were preserved from erosion. We find an approximately two-fold increase in both local topographic relief and valley concavity, which occurred around the time of the mid-Pleistocene transition. Our results support the proposed link12, 13, 14 between the onset of efficient glacial erosion in the European Alps and the transition to longer, colder glacial periods at the middle of the Pleistocene epoch.

Published
2011
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15. Deciphering neotectonics from river profile analysis in the karst Jura Mountains (northern Alpine foreland)

Author

Vincent Bichet, Urs Eichenberger, Jacques Mudry, Nicolas Carry, Pierre G. Valla, Mickael Rabin, Jean-Daniel Champagnac, Christian Sue, Laboratoire Chrono-environnement - CNRS - UBFC (UMR 6249) (LCE), Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC), Institute of Earth Surface Dynamics [Lausanne], Université de Lausanne (UNIL), Geological Institute [ETH Zürich], Department of Earth Sciences [Swiss Federal Institute of Technology - ETH Zürich] (D-ERDW), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich)- Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Institut Suisse de Spéléologie et de Karstologie (ISSKA), Institut Suisse de Spéléologie et de Karstologie, Laboratoire Chrono-environnement ( LCE ), Université Bourgogne Franche-Comté ( UBFC ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Franche-Comté ( UFC ), Institute of Earth Surface Dynamics, University of Lausanne, Lausanne, Switzerland, Geological Institute ( ETH ), Swiss Federal Institute of Technology in Zürich ( ETH Zürich ), Institut Suisse de Spéléologie et de Karstologie ( ISSKA ), Laboratoire Chrono-environnement - UFC (UMR 6249) (LCE), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Department of Earth Sciences [ETH Zürich] (D-ERDW), and Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology in Zürich [Zürich] (ETH Zürich)-Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology in Zürich [Zürich] (ETH Zürich)

Subjects
geography, geography.geographical_feature_category, Bedrock, [ SDU.STU.TE ] Sciences of the Universe [physics]/Earth Sciences/Tectonics, Geology, Post-glacial rebound, 15. Life on land, Karst, Neotectonics, Tectonics, 13. Climate action, Lithosphere, [ SDU.ENVI ] Sciences of the Universe [physics]/Continental interfaces, environment, Quaternary, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, Geomorphology, Foreland basin, ComputingMilieux_MISCELLANEOUS
Abstract

The study of the neotectonic activity in the Jura Mountains (northwestern most belt of the European Alps) represents a challenge in the application of quantitative geomorphology to extract landscape metrics and discuss potential coupling between tectonic, climatic and lithospheric mechanisms during the evolution of this mountain belt. The Jura Mountains are characterized by a karst calcareous bedrock, slightly affected by Quaternary glaciations, and by moderated uplift rates (

Published
2015
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16. Rethinking low-temperature thermochronology data sampling strategies for quantification of denudation and relief histories: A case study in the French western Alps

Author

Pierre G. Valla, Jean Braun, Peter van der Beek, Tectonique reliefs et bassins, Institut des Sciences de la Terre (ISTerre), Université Joseph Fourier - Grenoble 1 (UJF)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-PRES Université de Grenoble-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-PRES Université de Grenoble-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), European Project, and Centre National de la Recherche Scientifique (CNRS)-PRES Université de Grenoble-Université Joseph Fourier - Grenoble 1 (UJF)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-PRES Université de Grenoble-Université Joseph Fourier - Grenoble 1 (UJF)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])

Subjects
010504 meteorology & atmospheric sciences, Numerical modeling, 010502 geochemistry & geophysics, 01 natural sciences, inversion, Data sampling, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), low-temperature thermochronology, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, Transect, Geothermal gradient, Geomorphology, 0105 earth and related environmental sciences, Inversion (meteorology), 15. Life on land, Thermochronology, sampling and modeling strategies, Model resolution, Geophysics, numerical modeling, Denudation, 13. Climate action, Space and Planetary Science, relief development, exhumation, Geology
Abstract

International audience; We assess the importance of thermochronometric data sampling and modeling strategies for correctly estimating mountain belt exhumation. Thermochronological age-elevation profiles have been widely used to infer orogenic exhumation histories; however, recent studies have shown that this sampling strategy may not be the most pertinent for quantifying both denudation and relief history. Here, we investigate the ability of combining different thermochronology data sampling schemes with numerical modeling to better constrain denudation rates and relief changes. We produce synthetic thermochronology datasets for real Alpine topography under a specific exhumation and relief scenario using the thermal-kinematic model Pecube. We then adopt an inverse approach based on the Neighborhood Algorithm to quantitatively assess the resolution of different thermochronology datasets collected following elevation profiles, long transects and valley bottom sampling. We also test the effect of the modeling approach on denudation and relief predictions, in particular the influence of the topographic grid resolution and of potential constraints on the geothermal gradient. Our results show that sampling along a single elevation profile does not allow to quantitatively constrain both denudation and relief histories. Numerical outputs clearly evidence tradeoffs that limit the capacity of simultaneously resolving denudation rates and relief change. Quantitative predictions are only slightly different when combining elevation profiles along different valleys, but are highly improved when using long transects or valley-bottom samples combined with an elevation profile. The resolution with which relief evolution can be predicted may be increased by a factor of 2 by using spatially distributed datasets. Results of thermal parameter inversions suggest that the geothermal gradient may be better estimated using elevation profiles or long-transect sampling rather than using valley bottom samples. Simulations with different model topography resolutions show that degrading the resolution for computational efficiency may result in a loss of quantitative information on denudation rates and relief history. In summary, we highlight that both thermochronological sampling strategies and the choice of thermal parameters or model topography resolution have a significant influence on predicted denudation and relief histories. Ideally, the sampling strategy should be designed using preliminary modeling of expected denudation and relief histories, and a sensitivity study on assumed thermal parameters and model resolution should be performed when modeling the data. Although our modeling is based on a particular case study of relief evolution in the French western Alps, we believe that these inferences have general relevance for thermochronological studies within mountain belts.

Published
2011
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17. Frost-cracking control on catchment denudation rates: Insights from in situ produced 10Be concentrations in stream sediments (Ecrins-Pelvoux massif, French Western Alps)

Author

Pierre G. Valla, Julien Carcaillet, Didier Bourlès, Romain Delunel, Peter van der Beek, Laboratoire de Géodynamique des Chaines Alpines (LGCA), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut des Sciences de la Terre (ISTerre), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR), Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Collège de France (CdF)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Institut National de la Recherche Agronomique (INRA), ANR-08-BLAN-0303-01,ANR-08-BLAN-0303-01, Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), ANR-08-BLAN-0303,ERD-Alps,Erosion and Relief Development in the Western Alps(2008), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Collège de France (CdF (institution))-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA), and Erosion and Relief Development in the Western Alps, ANR-08-BLAN-0303-01,Erosion and Relief Development in the Western Alps, ANR-08-BLAN-0303-01

Subjects
Hypsometry, 010504 meteorology & atmospheric sciences, [SDE.MCG]Environmental Sciences/Global Changes, Drainage basin, 010502 geochemistry & geophysics, 01 natural sciences, Tectonic uplift, Geochemistry and Petrology, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, Earth and Planetary Sciences (miscellaneous), [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, Cosmogenic nuclide, Geomorphology, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, 10Be, Glacier, Massif, frost cracking, 15. Life on land, catchment denudation rates, Tectonics, Geophysics, Denudation, 13. Climate action, Space and Planetary Science, European Alps, Geology
Abstract

International audience; The potential tectonic and climatic controls on erosion rates in the European Alps and other mountain belts remain strongly debated. We have quantified denudation rates at catchment scales using in situ produced cosmogenic nuclides (10Be) in stream sediments, sampled at the outlets of twelve variously sized (27-1072 km2) catchments of the Ecrins-Pelvoux massif (French Western Alps), with average elevations ranging from 1700 to 2800 m. Spatially-averaged denudation rates, corrected for potential shielding by Little Ice Age glaciers, vary from 0.27 ± 0.05 to 1.07 ± 0.20 mm/yr on millennial timescales. Our results exhibit a correlation (ρ2 = 0.56) between denudation rate and mean catchment elevation, in the absence of significant correlation with any other morphometric parameters (relief, slope, catchment size, hypsometry, etc). Although such variations in erosion rates have been previously linked to variations in tectonic uplift rate, the relatively small size and tectonic homogeneity of our study area exclude a strongly variable tectonic control. We interpret the increase in erosion rate with elevation as the effect of frost-controlled processes, which are strongly temperature-dependent. We use a one-dimensional heat-flow model driven by high-resolution instrumental temperature records from the study area to correlate the variability in denudation rates with the integral of the absolute temperature gradient within the frost-cracking window (‑ 3 to ‑ 8 °C), a proxy of the frost-cracking intensity, for each catchment. The results imply that the efficiency of frost cracking constitutes a major control on catchment-wide denudation rates in the study area, explaining more than half the measured variability in these rates. Our study shows that present-day denudation of the Ecrins-Pelvoux massif is controlled by a climatically driven factor and suggests that frost-cracking processes impose an important control on the post-glacial topographic evolution of mid-latitude mountain belts.

Published
2010
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