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1. Source‐To‐Sink Sedimentary Budget of the African Equatorial Atlantic Rifted Margin

Author

Delphine Rouby, Jing Ye, Dominique Chardon, Artiom Loparev, Mark Wildman, and Massimo Dall'Asta

Subjects
West African craton, equatorial Atlantic rifted margin, denudation history, accumulation history, sediment routing system, source‐to‐sink, Geophysics. Cosmic physics, QC801-809, Geology, QE1-996.5
Abstract

Abstract Despite their very low relief and erosion rates, non‐orogenic (i.e., cratonic) continental domains account for over 60% of the Earth's exposed lands. Therefore, they contribute significantly to the clastic sediments and solutes exported to the ocean and should be accounted for in global studies. Nonetheless, they have been much less studied than orogenic domains. In this study, we establish the source‐to‐sink sedimentary budget of the sub‐saharan West African cratonic domain and its Equatorial Atlantic rifted margin using published low‐temperature thermochronological data to estimate onshore denudation and regional geological cross‐sections to estimate offshore accumulation. We show that during and immediately following rifting (130‐94 Ma), the build‐up and subsequent erosion of rift‐related relief resulted in a transient, 100–200 km wide strip along the margin recording high denudation rates (>50 m/Myr), while the inland domain underwent steady and very low denudation (

Published
2023
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2. The sediment routing systems of Northern South America since 250 M

Author

Flora Bajolet, Dominique Chardon, Delphine Rouby, Massimo Dall’Asta, Artiom Loparev, Renaud Couëffe, Jean-Yves Roig, Géosciences Environnement Toulouse (GET), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), TotalEnergies, and Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)

Subjects
[SDU]Sciences of the Universe [physics], Paleogeography, [SDU.STU.ST]Sciences of the Universe [physics]/Earth Sciences/Stratigraphy, Source-to-sink, General Earth and Planetary Sciences, Atlantic rifted margin, Andes, Intracratonic basin
Abstract

International audience; The present study is a contribution to the understanding of continental-scale source-to-sink sedimentary systems over geological time scales. The northern half of South America is taken as a case study to explore the relations between (i) continental tectonic boundary conditions (active / passive margin, orogenic activity) and intracontinental deformation, (ii) the spatial distribution of clastic sediment sources and sinks over the continent and its margins and (iii) the configuration of the main sediment routes. To do that, the evolving surface configuration of northern South America is investigated through a series of 10 paleo-geological maps compiled for key periods of the Meso-Cenozoic. The maps display (i) sedimentation areas and their depositional environments, (ii) sediment transport routes based on paleocurrent measurements and provenance studies, (iii) magmatic occurrences, (iv) active faults, (v) denudation/burial histories deduced from low-temperature thermochronology studies and (vi) areas of extensive Cenozoic lateritic cover.Three main successive continental-scale regimes of the source-to-sink systems are documented. An early erosional regime until ca. 125 Ma is attested to by a major sedimentary hiatus over a long-lasting asthenosphere-supported eroding superswell at the scale of northern South America and northwestern Africa. Sediments were routed from the superswell to the proto-Andean marginal basins, the Central Atlantic rifts/rifted margin basins and the Saharan cratonic basin. After ca. 125 Ma, a cratonic regime of mixed erosion/deposition established and maintained until the onset of the Andean orogeny at ca. 85 Ma. During this period, sediment routes from eroding cratonic domains to the proto-Andean margin basins were episodically closed by inherited Paleozoic structures (i.e., “arches”), whilst sediment fluxes to cratonic or rifted margin basins were partitioned by Atlantic rift shoulders / marginal upwarps of evolving amplitude that formed transient continental divides. After ca. 85 Ma, an Andes-dominated regime installed, in which Andean retro-foreland basins became the main sinks for orogenic sediment fluxes, while exchanges with cratonic basins were controlled by the topographic expression of foreland basins forebulges. Under that regime, cratonic domains mainly acted as by-pass zones for clastic sediments, and their extensive Paleogene and Lower Neogene lateritic covers argue for limited clastic exports from areas exposed to erosion. Very-long wavelength (x 1000 km) asthenospheric support, long-wavelength (x 100 km) lithospheric-scale deformation / vertical movements and climate-controlled erosion processes interacted to regulate cratonic sediment source-to-sink regimes of northern South America since 250 Ma.

Published
2022
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3. Weathering history and landscape evolution of Western Ghats (India) from 40 Ar/ 39 Ar dating of supergene K–Mn oxides

Author

Pierre-Etienne Mathé, Amandine Jean, Mudlappa Jayananda, Anicet Beauvais, Nicolas Arnaud, Dominique Chardon, Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-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)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Aix Marseille Université (AMU), Institut de Recherche pour le Développement (IRD [France-Sud]), Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD), Géosciences Environnement Toulouse (GET), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Université Joseph Ki-Zerbo [Ouagadougou] (UJZK), 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), University of Hyderabad, IFCPAR (5007-1)programme TelluS-SYSTERIRD, Cenozoic Denudation of South India, Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Institut National de la Recherche Agronomique (INRA), Ecologie marine tropicale des océans Pacifique et Indien (ENTROPIE [Nouvelle-Calédonie]), Université de la Nouvelle-Calédonie (UNC)-Institut de Recherche pour le Développement (IRD [Nouvelle-Calédonie]), Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Météo France-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS), Bangalore University, 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), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Université des Antilles (UA)-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), Université de Toulouse (Université de Toulouse), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Centre National d'Études Spatiales [Toulouse] (CNES), Université Ouaga 1 Pr Joseph Ki-Zerbo [Ouagadougou, Burkina Faso], Institut de Recherche pour le Développement (IRD [Nouvelle-Calédonie]), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), and Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Supergene (geology), 010504 meteorology & atmospheric sciences, [SDE.MCG]Environmental Sciences/Global Changes, Archean, 40Ar/39Ar geochronology, Geochemistry, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Escarpment, 010502 geochemistry & geophysics, Neogene, 01 natural sciences, Lateritic weathering, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, Deccan Traps, [SDU.STU.AG]Sciences of the Universe [physics]/Earth Sciences/Applied geology, Indian Western Ghats, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, Plateau, Manganese oxides, Cenozoic, Geology, Denudation, Geochronology, [SDU.STU.MI]Sciences of the Universe [physics]/Earth Sciences/Mineralogy
Abstract

International audience; Laterites preserved on both sides of the Western Ghats Escarpment of Peninsular India have formed by long-term lateritic weathering essentially after India-Seychelles continental break up following Deccan Traps emplacement (c. 63 Ma ago). Supergene manganese ores of the Western Ghats were formed on Late Archean manganese protores. Among Mn oxides composing the ores, cryptomelane (K-rich Mn oxide) was characterized and dated by 40Ar/39Ar geochronology. Measured ages complement those previously obtained in other South-Indian manganese ores from the hinterland plateau (Bonnet et al., 2016) and further document three major weathering periods, c. 53-44 Ma, c. 39-22 Ma, and c. 14-10 Ma, the later being documented for the first time in India. These periods coincide with global paleoclimatic proxies and date the lateritic weathering of three successive paleolandscapes of the Western Ghats that evolved under slow denudation (c. 8 m/myr) over the last 44 Myr and were mostly incised during the Neogene (< 22 Ma). That indicates the Western Ghats are a relict of a South Indian plateau preserved at the headwaters of very long east-flowing river systems and above the Western Ghats escarpment. Topography and denudation history of this landscape do not require Neogene tilt of the Peninsula as recently proposed.

Published
2019
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4. Superimposed Rifting at the Junction of the Central and Equatorial Atlantic: Formation of the Passive Margin of the Guiana Shield

Author

Delphine Rouby, Massimo Dall’asta, Dominique Chardon, Artiom Loparev, Jing Ye, Fabien Paquet, François Sapin, Flora Bajolet, Géosciences Environnement Toulouse (GET), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), TotalFinaElf, Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), and Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)

Subjects
geography, Rift, Plateau, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Continental crust, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, 15. Life on land, 010502 geochemistry & geophysics, 01 natural sciences, Gondwana, Paleontology, Geophysics, [SDU]Sciences of the Universe [physics], Geochemistry and Petrology, Lithosphere, Oceanic crust, Passive margin, Magmatism, 14. Life underwater, Geology, 0105 earth and related environmental sciences
Abstract

The passive margin of the Guiana Shield formed at the junction of the Central and Equatorial Atlantic Oceans that developed successively by a complex rifting process that achieved the final dispersal of Western Gondwana. Yet, the resulting spatial distribution of crustal thinning along the margin remains to be mapped and its controlling parameters deciphered. We used subsurface data to map the variability of crustal thinning along the margin. We show that the margin segments width primarily depends on their obliquity to rifting extension direction. The necking domain of the transform/oblique margin segments is much narrower (

Published
2021
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6. 3D model related to the publication: A fossil terrestrial fauna from Tobène (Senegal) provides a unique early Pliocene window in western Africa

Author

Sylvain Adnet, Moustapha Thiam, Rodolphe Tabuce, Fabrice Lihoreau, Lionel Hautier, Bernard Sambou, Renaud Lebrun, Jean-Renaud Boisserie, Jeremy E. Martin, Raphaël Sarr, Dominique Chardon, Institut des Sciences de l'Evolution de Montpellier (UMR ISEM), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Montpellier (UM)-Institut de recherche pour le développement [IRD] : UR226-Centre National de la Recherche Scientifique (CNRS), Université Cheikh Anta Diop [Dakar, Sénégal] (UCAD), Géosciences Environnement Toulouse (GET), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Laboratoire de paléontologie, évolution, paléoécosystèmes, paléoprimatologie (PALEVOPRIM ), Université de Poitiers-Centre National de la Recherche Scientifique (CNRS), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-École pratique des hautes études (EPHE), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), and Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)

Subjects
010504 meteorology & atmospheric sciences, Pliocene, Fauna, Carnivora, Window (geology), 3d model, 010502 geochemistry & geophysics, 01 natural sciences, Senegal, Paleontology, Geography, Lutrinae, Femur, [SDU.STU.PG]Sciences of the Universe [physics]/Earth Sciences/Paleontology, 0105 earth and related environmental sciences
Abstract

International audience; The present contribution contains the 3D virtual restoration of a Pliocene right femur belonging to a Lutrinae indet. (Carnivora) from Tobène, Senegal, described and figured in Lihoreau et al. (2021) : "A fossil terrestrial fauna from Tobène (Senegal) provides a unique early Pliocene window in Western Africa ".

Published
2021
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7. Post-rift stratigraphic architectures along the African margin of the Equatorial Atlantic: Part I the influence of extension obliquity

Author

Delphine Rouby, François Guillocheau, Jean Noël Ferry, Jing Ye, Cécile Robin, Massimo Dall’asta, Dominique Chardon, Géosciences Environnement Toulouse (GET), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Centre scientifique et Technique Jean Feger (CSTJF), TOTAL FINA ELF, 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), Total Oil and Gas Company, Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), 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), 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
010504 meteorology & atmospheric sciences, 010502 geochemistry & geophysics, 01 natural sciences, Divergence, Sierra leone, Paleontology, Lithosphere, Vertical displacements, Equatorial, Rifting Extension obliquity, 0105 earth and related environmental sciences, Earth-Surface Processes, [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, Extension obliquity, Equatorial Atlantic, Rift, Post-rift stratigraphy, Rifting, Margin segmentation, Subsidence, Cretaceous, Geophysics, Stratigraphy, Atlantic, Erosion, Geology
Abstract

International audience; We investigated the variability of the first-order crustal structure and early post-rift stratigraphy of six segments of the African Equatorial Atlantic margin using sub-surface data (seismic and wells). Extension obliquity of the segments varies from 0° for the West Ivory Coast and Ghana transform segments to 30° for the Togo-Benin oblique segment and 75° for the East Ivory Coast normally divergent segment. The Sierra Leone and Liberia segments underwent probably deformation during both the early Jurassic rifting of the Central Atlantic and the early Cretaceous rifting of the Equatorial Atlantic with contrasted divergence obliquities. For segments that underwent a single rifting, we show that, the higher the obliquity, the wider the crustal thinning domain. This has a major influence on the first-order geometry of all the post-rift horizons, including the present-day slope: the lower the obliquity, the larger the differential subsidence across the margin and the steeper the present-day slopes of post-rift horizons. This also has a major influence on the flexural isostatic response of the lithosphere to thermal- and erosion/sedimentation- driven (un)loads during the early post-rift. Narrow (transform) segments underwent higher flexural (and/or thermal) uplifts in the proximal domain than wider divergent segments. Along the same margin, divergent segments therefore may preserve early post-rift deposits in their proximal domains, whereas they are not preserved on nearby transform segments.

Published
2019
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8. The Equatorial Atlantic Laboratory: sediment routing systems and lithosphere deformation

Author

Dominique Chardon, Flora Bajolet, Artiom Loparev, Massimo Dall’asta, Delphine Rouby, and Jing Ye

Subjects
Routing (hydrology), Lithosphere, Sediment, Deformation (meteorology), Geomorphology, Geology
Abstract

We summarize the results of a 7 years study of the sediment routing systems of the West African Craton transporting its erosional products to the Central and Equatorial Atlantic passive margins at geological time scale. We used paleogeograhic maps to define the geodynamics framework of this routing system with in particular the propagation of the Equatorial Atlantic oblique rift separating the West African and Amazonian Cratons. We used sub-surface data to evaluate the evolution of lithosphere necking distribution along the conjugated African and South American margins of the rift system. We estimated the long-term denudation pattern at continental scale from low temperature thermochronology measures of samples from 3 transects perpendicular to the Atlantic margin. We used the exceptional preservation of geomorphologic markers to reconstruct the drainage system of the craton since 45 Ma, and estimate the associated denudation and exports of terrigeneous sediments to the Atlantic margin. Finally, we estimated the accumulation history in the passive margin basins and compare them with the estimated denudation histories from thermal histories and geomorphologic markers. We show that the modes of preservation of sedimentary export in the passive margin basins are highly variable in time (immediate post roft versus late post-rift) and space (transform/oblique versus divergent margin segments). We show that the present day drainage of the West African Craton as been stable since 30 Ma when it underwent a major reorganization driven by the growth of the relief associated with the Hoggar mantle plume. We show that accumulation in the passive margin basins fall within the same order of magnitude than denudation on the craton at the scale of the Meso-Cenozoic. This allows us to argue to the relevance of using the stratigraphic architecture of passive margin basins to estimate the denudation history of their continental domains.

Published
2020
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9. Reappraisal of Variscan tectonics in the southern French Massif Central

Author

Damien Roques, Markus Aretz, Dominique Chardon, GET (GET), and Ecole Nationale Supérieure des Télécommunications de Bretagne

Subjects
010504 meteorology & atmospheric sciences, Iberian-Armorican syntax, Nappe tectonics, 010502 geochemistry & geophysics, 01 natural sciences, Transpression, Nappe, Paleontology, Wildflysch, Sheath fold, Foreland basin, 0105 earth and related environmental sciences, Earth-Surface Processes, geography, geography.geographical_feature_category, Cevennes fault, Transtension, Massif, Fold (geology), Geophysics, Sinistral and dextral, Montagne Noire, Shear (geology), [SDU]Sciences of the Universe [physics], Geology
Abstract

The comprehensive kinematic analysis of the Variscan fold nappes and associated wildflysch in the Southeastern Montagne Noire shows that the nappes were thrust northeastwardly along the Cevennes fault as a result of strike-slip-dominated sinistral transpression between 340 and 323 Ma. Macro- and map-scale recumbent folding and nappe stacking were achieved by ENE-directed, strike-parallel thrust shearing. The recumbent folds evolved into sheath folds by interplay of continued strike-parallel thrust shearing and strike-normal shortening manifested by north-verging folds that grew during wildflysch sedimentation. These results call for a tectonic reassessment of the southern side of the Variscides. The foreland basin was decoupled from the hinterland along orogen-scale sinistral fault(s) trending at a high angle to the orogenic trend, which interacted with a variety of hinterland-ward thrust systems. The shift from sinistral transpression to dextral transtension along the Cevennes fault after 317 Ma accompanied the closure of the Iberian-Armorican syntax by accommodating northeastward escape and gravitational collapse of the northern limb of the syntax. These results illustrate the impact of the shift from plate convergence-controlled to escape-controlled kinematics on shear sense reversal and lower crust exhumation along long-lived strike-slip fault systems.

Published
2020
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10. Landform-regolith mapping in the West African context

Author

Benjamin Sawadogo, Ousmane Bamba, Dominique Chardon, Université Joseph Ki-Zerbo [Ouagadougou] (UJZK), GET (GET), and Ecole Nationale Supérieure des Télécommunications de Bretagne

Subjects
Detrital duricrust, Pediment, 020209 energy, Earth science, Geochemistry, Context (language use), 02 engineering and technology, 010502 geochemistry & geophysics, 01 natural sciences, Duricrust, Chart, Prospectivity mapping, Geochemistry and Petrology, 0202 electrical engineering, electronic engineering, information engineering, Mineral exploration, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, Landform, Weathering profile, Bedrock, Sampling (statistics), Geology, 15. Life on land, Regolith, Field (geography), [SDU]Sciences of the Universe [physics], Economic Geology
Abstract

In this paper, we present an integrated landform-regolith mapping protocol/chart for West Africa developed using a case from Central Burkina Faso. The chart accounts for (i) the specificities of the ubiquitous, duricrust-capped remnants of the regional paleolandsurfaces – particularly the residual or detrital character of the Fe duricrusts – and (ii) the diversity of the remaining, non-duricrusted portions of the landscape, with an emphasis on the pitfalls encountered in determining the in-situ or transported character of the regolith. The paper also provides field identification criteria and illustrations of the typical West African landform-regolith associations. The landform-regolith mapping chart is integrated into a prospectivity chart, which is used to define exploration guides: (i) defining sampling strategies, (ii) interpreting potential geochemical anomalies and (iii) targeting lateral extensions of known bedrock mineralizations. The mapping protocol further allows for the definition of a class of landform-regolith association propitious to supergene mineral concentrations. The mapping protocol is shown to be transposable to wetter contexts and, more generally, to other tropical shield provinces.

Published
2020
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11. Stabilization of large drainage basins over geological time scales: Cenozoic West Africa, hot spot swell growth, and the Niger River

Author

Frédéric Christophoul, Anicet Beauvais, Jean-Louis Grimaud, Delphine Rouby, and Dominique Chardon

Subjects
geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Drainage basin, Continental divide, Sedimentary basin, 010502 geochemistry & geophysics, 01 natural sciences, Paleontology, Geophysics, Geologic time scale, Geochemistry and Petrology, Passive margin, 14. Life underwater, Paleogene, Cenozoic, Palaeogeography, Geology, 0105 earth and related environmental sciences
Abstract

Reconstructing the evolving geometry of large river catchments over geological timescales is crucial to constraining yields to sedimentary basins. In the case of Africa, it should further help deciphering the response of large cratonic sediment routing systems to Cenozoic growth of the basin-and-swell topography of the continent. Mapping of dated and regionally correlated lateritic paleolandscape remnants complemented by onshore sedimentological archives allows the reconstruction of two physiographic configurations of West Africa in the Paleogene. Those reconstructions show that the geometry of the drainage stabilized by the Late Early Oligocene (29 Ma) and probably by the end of the Eocene (34 Ma), allowing to effectively link the inland morphoclimatic record to offshore sedimentation since that time, particularly in the case of the Niger catchment – delta system. Mid-Eocene paleogeography reveals the antiquity of the Senegambia catchment back to at least 45 Ma and suggests that a marginal upwarp forming a continental divide preexisted Early Oligocene connection of the Niger and Volta catchments to the Equatorial Atlantic Ocean. Such a drainage rearrangement was primarily enhanced by the topographic growth of the Hoggar hot spot swell and caused a major stratigraphic turnover along the Equatorial margin of West Africa.

Published
2016
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12. Long-term evolution of the West African Transform margin : estimates of denudation from Benin using apatite thermochronology

Author

Damien Huyghe, Delphine Rouby, Massimo Dall’asta, david webster, Dominique Chardon, Mark Wildman, Jing Ye, Roderick Brown, 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 Glasgow, Géosciences Environnement Toulouse (GET), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), Institut de Recherche pour le Développement (IRD), TOTAL S.A., TOTAL FINA ELF, Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), 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, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Transform fault, Geology, Sedimentary basin, Structural basin, 010502 geochemistry & geophysics, 01 natural sciences, Thermochronology, Gondwana, Paleontology, Denudation, Continental margin, 13. Climate action, Cenozoic, 0105 earth and related environmental sciences
Abstract

The Benin continental margin was formed during the breakup of Gondwana through oblique rifting along transform faults. The evolution of topography following breakup directly affects the evolution of sedimentary basins, which has major implications for hydrocarbon exploration in the region. Quantitative constraints on erosion across Benin are limited to the Cenozoic, based on analysis of dissected lateritic palaeolandscapes. To resolve the Mesozoic erosion history, we have obtained apatite fission-track and single-grain (U–Th–Sm)/He data from 18 samples collected across a 600 km long transect through Benin. We invert these data, including available geological and geomorphological constraints, to obtain time–temperature paths, which are used to estimate magnitudes of denudation over the last 200 myr. Our study suggests that denudation was focused over a c. 300 km long seaward sloping limb of the marginal upwarp and at the southern margin of the interior Iullemmeden Basin from 140 to 100 Ma with lower magnitudes of denudation characterizing the continental interior and post-Cretaceous evolution of the margin. Models are consistent with modest burial (c. 1 km) of the Iullemmeden Basin between 120 and 85 Ma, and of the continental margin between 85 and 45 Ma. By the Eocene the first-order relief of Benin had developed, with regional erosion rates Supplementary information: Full details of the analytical data and modelling results, including the various constraints, and further data on denudation and burial magnitudes and rates are available at https://doi.org/10.6084/m9.figshare.c.4220804

Published
2019
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13. West African lateritic pediments: Landform-regolith evolution processes and mineral exploration pitfalls

Author

Jean-Louis Grimaud, Anicet Beauvais, Ousmane Bamba, Dominique Chardon, Géosciences Environnement Toulouse (GET), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), Centre de Géosciences (GEOSCIENCES), MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), 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), Aix Marseille Université (AMU), Institut de Recherche pour le Développement (IRD [France-Sud]), Centre National de la Recherche Scientifique (CNRS), Université Joseph Ki-Zerbo [Ouagadougou] (UJZK), IRD (JEAI FasoLith), TopoAfrica project [ANR-08-BLAN-572 0247-02], West African exploration Initiative (WAXI), CNRS, TS2P (Transform Source-to-Sink Project) - Total Exploration and Production, AMIRA International, Geological Surveys/Departments of Mines in West Africa [P934A], Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), MINES ParisTech - École nationale supérieure des mines de Paris-PSL Research University (PSL), 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), Université de Ouagadougou, Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Centre National d'Études Spatiales [Toulouse] (CNES), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Mines Paris - PSL (École nationale supérieure des mines de Paris), and 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)

Subjects
Pediment, 010504 meteorology & atmospheric sciences, Outcrop, Glacis, Geochemistry, Weathering, 010502 geochemistry & geophysics, 01 natural sciences, Regolith, Landform evolution processes, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, Mineral exploration, [SDU.STU.AG]Sciences of the Universe [physics]/Earth Sciences/Applied geology, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, Landform, Mega-geomorphology, Bedrock, 15. Life on land, 13. Climate action, Clastic rock, General Earth and Planetary Sciences, Geology
Abstract

International audience; This paper is a contribution to the understanding of surface dynamics of tropical shields over geological timescales. Emphasis is put on the fundamental and applied implications of regolith production and dispersion processes through the formation, dissection and preservation of landforms. It is based on the case study of sub Saharan West Africa, which recorded Neogene (24-3 Ma) stepwise dissection of its topography through the emplacement of three lateritic pediment systems, which still occupy most of its surface. Pediments are erosional/transportation slopes having been weathered and duricrusted. Pediment-regolith associations therefore depend on the parent rock, transport dynamics and preservation of the material having transited on their surface as well as on the intensity of their weathering/duricrusting. Iron oxy-hydroxide-cemented clastic sediments (detrital ferricretes) and unconsolidated clastic sediments are the dominant outcropping material, and as such represent a challenge for mineral exploration that relies on surface geochemical sampling to detect metal concentration in the bedrock. Landform-regolith mapping beyond the scale of modern interfluves combined with paleolandscape reconstitution are relevant to provide exploration guides for (i) interpreting geochemical anomalies on pediments, (ii) tracing their potential source when they have been “transported” on pediments and (iii) targeting suspected ore bodies concealed beneath pediment(s). Past and present latitudinal climatic zonation of pedimentation and weathering patterns suggests a gradation of pedimentation process across the intertropical zone and explains why pediments may have been overlooked in equatorial environments, with implications for mineral exploration. Successive pediment systems adapted to uneven, knickzone bearing river networks, producing a spatially consistent and reduced (

Published
2018
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14. Multi-scale strainfield analysis using geostatistics : investigating the rheological behavior of the hot Variscan crust of the Pyrenees (Axial Zone)

Author

Benjamin Le Bayon, Dominique Chardon, Yoann Denèle, Bryan Cochelin, Charles Gumiaux, Géosciences Environnement Toulouse (GET), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), Institut des Sciences de la Terre d'Orléans - UMR7327 (ISTO), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)-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)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Géodynamique - UMR7327, Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)-Institut des Sciences de la Terre d'Orléans - UMR7327 (ISTO), 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)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (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)-Centre National de la Recherche Scientifique (CNRS), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Institut de Recherche pour le Développement (IRD), ANR-10-LABX-0100,VOLTAIRE,Geofluids and Volatil elements – Earth, Atmosphere, Interfaces – Resources and Environment(2010), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), and 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)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)

Subjects
[SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, 010504 meteorology & atmospheric sciences, Hot orogen, Geology, Crust, Pure shear, 010502 geochemistry & geophysics, 01 natural sciences, Transpression, Strain partitioning, Lineation, Tectonics, Kriging interpolation, Variogram analysis, Kkriging interpolation, Shear zone, Variogram, Petrology, 0105 earth and related environmental sciences
Abstract

International audience; The present study provides a quantitative way to analyze and interpolate strainfields from ductile fabric field measurements using geostatistics. Based on variogram analysis and kriging interpolations, the developed methodology allows computing automatic cleavage and lineation trajectory maps at different scales from a same field structural dataset. For the example provided by the hot Variscan crust of the Pyrenees, the analysis of cleavage/stretching lineations orientation and kinematic data document pure shear conditions recorded during convergence. Strain was vertically partitioned between an upper crust submitted to homogeneous thickening responding to N-S (orogen-normal) shortening and a hot and partially molten mid-lower crust affected by horizontal longitudinal (orogen-parallel) flow. The emplacement of plutons and gneiss domes generated heterogeneities in the upper crust and induced strain localization into steep anastomosed transpressional shear zones flanking those structures. The results show that geostatistics applied to structural geology are powerful tools for retrieving tectonic regimes of large orogenic segments by identifying and quantifying perturbations in the strainfields induced by protracted and potentially complex tectonic histories. The variogram analysis also gives first order clues to evaluate whether the considered structural domains underwent single continuous ductile or polyphased brittle-ductile deformation.

Published
2018
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15. Cenozoic sediment budget of West Africa and the Niger delta

Author

Delphine Rouby, Jean-Louis Grimaud, Anicet Beauvais, Dominique Chardon, Centre de Géosciences (GEOSCIENCES), MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Géosciences Environnement Toulouse (GET), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), 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), Aix Marseille Université (AMU), Institut de Recherche pour le Développement (IRD), Centre National de la Recherche Scientifique (CNRS), WAXI. Grant Number: P934ACNRSgOcad consortium, ANR-08-BLAN-0247,TOPOAFRICA,Evolution of the African topography over the last 250 My from the sedimentary record to mantle dynamics(2008), Mines Paris - PSL (École nationale supérieure des mines de Paris), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), 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), MINES ParisTech - École nationale supérieure des mines de Paris-PSL Research University (PSL), Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-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), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Centre National d'Études Spatiales [Toulouse] (CNES)

Subjects
010504 meteorology & atmospheric sciences, Drainage basin, Geochemistry, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, 010502 geochemistry & geophysics, 01 natural sciences, Sedimentary depositional environment, Continental margin, continental margin, 14. Life underwater, Sedimentary budget, Geomorphology, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, River delta, Cenozoic, Source-to-sink, Geology, craton, Denudation, Clastic rock, Africa, Sedimentary rock, sediment flux
Abstract

International audience; Long-term (106–7 yr) clastic sedimentary fluxes to the ocean provide first-order constraints on the response of continental surfaces to both tectonic and climatic forcing as well as the supply that builds the stratigraphic record. Here, we use the dated and regionally correlated relict lateritic landforms preserved over Sub-Saharan West Africa to map and quantify regional denudation as well as the export of main catchments for three time intervals (45–24, 24–11 and 11–0 Ma). At the scale of West Africa, denudation rates are low (ca. 7 m Myr−1) and total clastic export rate represents 18.5 × 103 km3 Myr−1. Export rate variations among the different drainage groups depend on the drainage area and, more importantly, rock uplift. Denuded volumes and offshore accumulations are of the same magnitude, with a noticeably balanced budget between the Niger River delta and its catchment. This supports the establishment of the modern Niger catchment before 29 Ma, which then provided sufficient clastic material to the Niger delta by mainly collecting the erosion products of the Hoggar hotspot swell. Accumulations on the remaining Equatorial Atlantic margin of Africa suggest an apparent export deficit but the sediment budget is complicated by the low resolution of the offshore data and potential lateral sediment supply from the Niger delta. Further distortion of the depositional record by intracontinental transient storage and lateral input or destabilization of sediments along the margin may be identified in several locations, prompting caution when deducing continental denudation rates from accumulation only.

Published
2018
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16. MESO-CENOZOIC ACCUMULATION HISTORY OF THE AFRICANMARGIN OF THE EQUATORIAL ATLANTIC

Author

Loparev, Artiom, Rouby, Delphine, Dominique, Chardon, Dall’asta, Massimo, Guillocheau, François, Robin, Cécile, Al., Et, Géosciences Environnement Toulouse (GET), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), TOTAL S.A., TOTAL FINA ELF, 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), Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), 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.ST]Sciences of the Universe [physics]/Earth Sciences/Stratigraphy, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology
Abstract

International audience; The objective of the Transform Source to Sink Project (TS2P) is to link the dynamics of the erosion ofthe West African Craton to the offshore sedimentary basins of the African margin of the Equatorial Atlanticat geological time scales. This margin, alternating transform and oblique segments from Guinea to Nigeria,shows a strong structural variability in the margin width, continental geology and relief, drainage networksand subsidence/accumulation patterns. We analyzed this system combining onshore geology andgeomorphology as well as offshore sub-surface data.We defined offshore basins stratigraphic architectures of the 3 sub-basins (Sierra Leone /Liberia, IvoryCoast and Ghana / Togo / Benin) and used these to establish their terrigeneous accumulation histories includingthe whole depositional system (from the shoreline to the most distal deposits onto the oceanic crust). We thencorrected these from remaining porosity after compaction as well as in-situ production (mainly carbonates)established from well-data. We included uncertainties related to the time to depth conversion, biostratigraphy,porosity and in-situ production corrections. We discuss our results in terms of Saddler effect for the most recenttime periods. Accumulations in the three basins show increased rates during the Cenomanian, Maastrichtianand Oligocene.We compare these accumulation histories to paleogeographic maps established at the scale of WestAfrica spanning the continental domain and offshore basins since 200 Ma and discuss their source to sinkimplications during the opening of Equatorial Atlantic. The Cenomanian accumulation may be related to theerosion of the remaining rift-shoulder following continental break-up. The Maastrichian increase inaccumulation could be related to either the tectonic inversion of western Africa at the time or to climatic changeaffecting erosion capacity in the continental drainage area. The Oligocene peak is contemporaneous of a majordrainage reorganization in West Africa following the rise of the Hoggar and the major sea-level fall at the time.Some uncertainties remain to be addressed in the Ghana / Togo / Benin basin on the contribution of theneighboring Niger Delta developing throughout the Neogene as well as the shredding effect of Mass TransportDeposits affecting this segment of the margin.

Published
2017

17. Strike-slip metamorphic core complexes: Gneiss domes emplaced in releasing bends

Author

Damien Roques, Pierre Barbey, Yoann Denèle, Jérôme Ganne, Dominique Chardon, Sonia Rousse, Géosciences Environnement Toulouse (GET), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), Centre de Recherches Pétrographiques et Géochimiques (CRPG), and Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)

Subjects
010504 meteorology & atmospheric sciences, Metamorphic core complex, Geochemistry, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Geology, 010502 geochemistry & geophysics, Strike-slip tectonics, 01 natural sciences, [SDU]Sciences of the Universe [physics], Petrology, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Gneiss
Abstract

We investigate the development of a Neoproterozoic metamorphic core complex (MCC) in the Marbat area (southern Arabian Peninsula). The MCC is a gneiss dome emplaced in a releasing bend along a dextral strike-slip fault system. Dome emplacement-related extension was at a high angle to the long axis of the dome and 65 degrees from the strike-slip fault system. Shortening is recorded in the upper plate of the MCC in a direction normal to the extension direction. Extensional emplacement of the gneiss dome accommodated lower crust exhumation and contributed to the formation of a ductile strike-slip releasing bend from an initial fault step. The Marbat example allows defining transversal stretching-dominated strike-slip MCCs, which would represent the early development stages of longitudinal stretching-dominated strike-slip MCCs. Conversely, longitudinal stretching-dominated strike-slip MCCs produced at low finite extension would result from strike-slip-dominated transtension. This study bears important implications for lower crust exhumation under pulla-part basin systems in obliquely convergent or divergent settings.

Published
2017
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18. Modes, tempo, and spatial variability of Cenozoic cratonic denudation: The West African example

Author

Dominique Chardon and Anicet Beauvais

Subjects
geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Context (language use), 15. Life on land, 010502 geochemistry & geophysics, 01 natural sciences, Craton, Paleontology, Geophysics, Denudation, 13. Climate action, Geochemistry and Petrology, Clastic rock, Erosion, Sedimentary rock, Epeirogenic movement, Sea level, Geology, 0105 earth and related environmental sciences
Abstract

[1] Quantifying long-term erosion of tropical shields is crucial to constraining the role of lateritic regolith covers as prominent sinks and sources of CO 2 and sediments in the context of long-term Cenozoic climate change. It is also a key to understanding long-term landform evolution processes operating over most of the continental surface and their control onto the sediment routing system. We study the surface evolution of West Africa over three erosion periods (~ 45–24, ~ 24–11 and ~ 11–0 Ma) recorded by relicts of three subcontinental-scale lateritic paleolandsurfaces whose age is bracketed by 39 Ar/ 40 Ar dating of lateritic K-Mn oxides. Denudation depths and rates compiled from 380 field stations show that despite heterogeneities confined to early-inherited reliefs, the subregion underwent low and homogeneous denudation (~ 2–20 m Ma –1) over most of its surface whatever the considered time interval. This homogeneity is further documented by a worldwide compilation of cratonic denudation rates, over long-term, intermediate and modern Cenozoic time scales (10 0 –10 7 yr). These results allow defining a steady state cratonic denudation regime that is weathering-limited, i.e., controlled by the thickness of the (lateritic) regolith available for stripping. Steady state cratonic denudation regimes are enabled by maintained compartmentalization of the base levels between river knick points controlled by relief inheritance. Under such regimes, lowering of base levels and their fossilization are primarily imposed by long-term eustatic sea level fall and climate rather than by epeirogeny. The expression of steady state cratonic denudation regimes in clastic sedimentary fluxes remains to be investigated. Components: 9,200 words, 13 figures, 2 tables.

Published
2013
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19. Vertical strain partitioning in hot Variscan crust: Syn-convergence escape of the Pyrenees in the Iberian-Armorican syntax

Author

Benjamin Le Bayon, Bryan Cochelin, Charles Gumiaux, Yoann Denèle, Dominique Chardon, Géosciences Environnement Toulouse (GET), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), 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), Métallogénie - UMR7327, 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)-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 de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC), 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)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Géodynamique - UMR7327, 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)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC), and 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)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)

Subjects
010504 meteorology & atmospheric sciences, Orocline, syntaxe, 010502 geochemistry & geophysics, 01 natural sciences, Transpression, dôme gneissique, gneiss dome, Variscan, hot orogen, Lithosphere, Petrology, orogène chaud, Foreland basin, syntax, orocline, 0105 earth and related environmental sciences, Pyrénées, [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, Varisque, Pyrenees, lcsh:QE1-996.5, Geology, Crust, 15. Life on land, lcsh:Geology, Delamination (geology), Magmatism, Shear zone, transpression
Abstract

International audience; A new structural map of the Paleozoic crust of the Pyrenees based on an extensive compilation and new kinematic data allows for the evaluation of the mechanical coupling between the upper and lower crust of the abnormally hot foreland of the Variscan orogen of SW Europe. We document partitioning between coeval lower crustal lateral flow and upper crustal thickening between 310 and 290 Ma under an overall dextral transpressive regime. Partitioning also involved syn-convergence transtensional gneiss domes emplacement during this period. Late orogen-normal shortening of the domes and strain localization in steep crustal-scale transpressive shear zones reflects increasing coupling between the lower crust and the upper crust. The combination of dextral transpression and eastward flow in the Pyrenees results from the shortening and lateral escape of a hot buoyant crust along the inner northern limb of the closing Cantabrian orocline at the core of the Iberian-Armorican arc between ca. 305 and 295 Ma. Delamination or thermal erosion of the lithosphere enhanced orocline closure and explains (1) the switch from crust-to mantle-derived magmatism in the Iberian-Armorican arc and (2) the abnormally hot and soft character of the Pyrenean crust that escaped the closing syntax.; Une nouvelle carte structurale harmonisée et une série de coupes de la croûte paléozoïque des Pyrénées sont présentées sur la base d'une compilation et de nouvelles observations de terrain. Cette carte permet d'évaluer les modalités du couplage mécanique entre la croûte supérieure et la croûte inférieure de l'avant-pays anormalement chaud de l'orogène varisque. La croûte inférieure a flué latéralement pendant l'épaississement de la croûte supérieure dans un contexte transpressif dextre entre 310 et 290 Ma. Dans ce contexte convergent et grâce à un couplage crustal partiel, la croûte inférieure a pu être partiellement exhumée dans des dômes gneissiques transtensifs. Le serrage tardif des dômes et la localisation progressive de la déformation dans des zones de cisaillement transpressives d'ampleur régionale attestent de l'augmentation du degré de couplage entre croûtes supérieure et inférieure pendant le refroidissement régional. La combinaison de la transpression dextre et du fluage latéral de la croûte des Pyrénées résulte du raccourcissement et de l'échappement du matériau piégé dans la syntaxe ibéro-armoricaine lors de son amplification et la fermeture de l'orocline cantabrique en son coeur entre 305 et 295 Ma. L'érosion thermique ou la délamination du manteau lithosphérique a permis (1) la transition entre un magmatisme crustal et un magmatisme mantellique ou hybride dans la syntaxe et (2) la fermeture de l'orocline et l'échappement contemporain du matériel pyrénéen chaud qu'elle contenait.

Published
2017
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20. Cenozoic lateritic weathering and erosion history of Peninsular India from 40 Ar/ 39 Ar dating of supergene K-Mn oxides

Author

Nicolas Arnaud, Anicet Beauvais, Nicolas Bonnet, Mudlappa Jayananda, Dominique Chardon, Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), 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), Aix Marseille Université (AMU), Institut de Recherche pour le Développement (IRD), Centre National de la Recherche Scientifique (CNRS), Géosciences Montpellier, Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Université des Antilles (UA)-Centre National de la Recherche Scientifique (CNRS), Géosciences Environnement Toulouse (GET), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), Bangalore University, Cefipra project 5007-1, IRD, INSU, 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), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles (UA), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Centre National d'Études Spatiales [Toulouse] (CNES), 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), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), and Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Supergene (geology), 010504 meteorology & atmospheric sciences, Archean, Geochemistry, India, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Weathering, Escarpment, 010502 geochemistry & geophysics, 01 natural sciences, Lateritic weathering, Mn-ore deposits, Geochemistry and Petrology, Deccan Traps, 40Ar-39Ar geochronology, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, Plateau, Cenozoic, Supergene Mn-oxides, Geology, 15. Life on land, Geochronology
Abstract

International audience; Since Deccan Traps extrusion ~ 65 Ma ago, thick weathering mantles have developed over Peninsular India on both the western coastal lowland and adjacent plateau separated by the Western Ghats Escarpment. Manganiferous lateritic profiles formed by supergene weathering of Late Archean manganiferous protores are exposed on paleolandsurface remnants on both sides of the escarpment. Petrological and geochemical characterizations of samples from those Mn lateritic profiles allowed identifying cryptomelane (K-Mn oxide) dated by 40Ar/39Ar geochronology. The ages obtained document major weathering periods, ca. 53-50 Ma, and ca. 37-23 Ma in the highland, and ca. 47-45 Ma, ca. 24-19 Ma and discrete weathering pulses at ~ 9 Ma and ~ 2.5 Ma in the lowland. Old ages of the highland (53-50 Ma) and the lowland (47-45 Ma) indicate synchronous lateritic weathering across the escarpment at a time the peninsula started to drift across the equatorial belt. Intense weathering periods at ca. 53-45 and ca. 37-23 Ma are interpreted to reflect the Early Eocene climatic optimum and the onset of Asian monsoon regimes, respectively. The ages further indicate that most of the dissection of the highland must have taken place after ~ 23 Ma, whereas the lowland was weakly incised essentially after ~ 19 Ma. Our results also document divergent erosion and weathering histories of the lowland and the highland after the Eocene, suggesting installation of a dual climatic regime across the Western Ghats escarpment.

Published
2016
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21. WEATHERING AND DENUDATION OF THE WESTERN CONTINENTAL MARGIN OF PENINSULAR INDIA: THE 40 Ar/ 39 Ar DATING OF LATERITIC K-RICH MANGANESE OXIDES

Author

Nicolas, Bonnet, BEAUVAIS, Anicet, Arnaud, Nicolas, Dominique, Chardon, Guillaume, Dupont-Nivet, 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), Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), 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 Montpellier (UM), Géosciences Environnement Toulouse (GET), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), Université de Rennes (UNIV-RENNES), 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 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), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Université de Rennes (UR), 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), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Centre National d'Études Spatiales [Toulouse] (CNES), and Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)

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

International audience; The Cenozoic weathering of peninsular India has been advocated as a major driver of global cooling, however, its timing remains virtually unconstrained such that proposed links between tropical weathering of the Deccan Traps, regional monsoonal intensity and global climate remains speculative. To solve this conundrum we present here a revised weathering chronology based on the identification of lateritic paleosurfaces and their dating using 40 Ar/ 39 Ar on su-pergene K-rich manganese oxides. We focus on the Indian western passive margin where the Western Ghats Escarpment (WGE) – a ~1000 m high topographic barrier resulting from the continental break up of Greater India – exposes exceptionally preserved weathering profiles from the western coastal lowlands to the eastern highland plateaus above the WGE. Four main lateritic paleosurfaces have been identified: Three in the highland; a high landsurface (Al-Fe mostly bauxite) at elevation 1200-1000 m asl, an intermediate landsurface covered by a Fe-duricrust at 1000-900 m asl and a lower pediment landsurface at 850-600 m asl; and one in the coastal lowland underneath a pediment landsurface at 150-50 m asl. The 40 Ar/ 39 Ar ages document three major weathering periods over the Cenozoic. The oldest weathering period (W1) is recorded between 53 Ma to 45 Ma both in the highland and the lowland. This correlates to the Global Eocene climatic Optimum, and allows defining a bauxitic paleolandsurface across the escarpment. Intense bauxitic weathering between ~ 45 and 47 Ma in the lowland indicate that the WGE was stabilized before ~ 47 Ma on its margin and also implies low denudation rate at the foot of the WGE (

Published
2016

22. Cenozoic surface dynamics of West Africa: Drainage, hot spot swell growth, erosion budget and offshore sedimentary record

Author

Dominique Chardon, Delphine Rouby, Jean-Louis Grimaud, Damien Huyghe, Anicet Beauvais, François Guillocheau, Cécile Robin, Ye Jing, Massimo Dall'Asta, Géosciences Environnement Toulouse (GET), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Mines Paris - PSL (École nationale supérieure des mines de Paris), Université Paris sciences et lettres (PSL), Institut de Recherche pour le Développement (IRD), Aix Marseille Université (AMU), 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), TOTAL FINA ELF, TotalFinaElf, Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), MINES ParisTech - École nationale supérieure des mines de Paris, 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.ST]Sciences of the Universe [physics]/Earth Sciences/Stratigraphy
Abstract

International audience; Mapping of dated and regionally correlated lateritic paleolandscape remnants allowed reconstructing two Paleogene physiographic configurations of West Africa. Topographic reconstructions were corrected from flexural isostasy due to the erosion paleolandscapes have undergone since their abandonment. The reconstructions show that the drainage stabilized by 29 Ma and probably 34 Ma, allowing to link the inland geomorphic record to offshore sedimentation since that time. Mid-Eocene paleogeography further suggests that a marginal upwarp forming a continental divide preexisted Early Oligocene connection of the Niger and Volta catchments to the Equatorial Atlantic Ocean. Drainage rearrangement was primarily enhanced by the topographic growth of the Hoggar hot spot swell and must have caused a major stratigraphic turnover along the Equatorial margin of West Africa. Differential elevations of reconstructed regional paleolandsurfaces geometries provide the spatial distribution of denudation for 3 time-increments (45-24, 24-11, 11-0 Ma). Volumetric erosional exports to the Equatorial Atlantic margin of Africa were then estimated for the drainage basins of constrained geometry for each time increment. Taking into account the continental bedrock lithologies and associated type regoliths, first-order mineralogical and granulometric composition of clastic yie lds are estimated for each drainage basin and for each erosion periods. Interpretation of offshore seismic lines allows for the evaluation of the stratigraphic expression of the continental erosion fluxes and documentation of the contrasted vertical mobility histories of margin's segments since 45 Ma. Confrontation of offshore clastic sediment volume estimates to continental erosion fluxes permits the source-to-sink investigation of a unique case study where both onshore erosion and offshore accumulations may be compared over geological time scales.

Published
2016

23. Cenozoic Source-to-Sink of the African margin of the Equatorial Atlantic

Author

Delphine Rouby, Dominique Chardon, Damien Huyghe, François Guillocheau, Cécile Robin, Artiom Loparev, Jing Ye, Massimo Dall’asta, Jean-Louis Grimaud, Géosciences Environnement Toulouse (GET), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), 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), TOTAL PAU, St Anthony Falls Laboratory (SAFL), University of Minnesota [Twin Cities] (UMN), University of Minnesota System-University of Minnesota System, European Geosciences Union, Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), 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), 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
[SDU.STU.ST]Sciences of the Universe [physics]/Earth Sciences/Stratigraphy
Abstract

International audience; The objective of the Transform Source to Sink Project (TS2P) is to link the dynamics of the erosion of theWest African Craton to the offshore sedimentary basins of the African margin of the Equatorial Atlantic atgeological time scales. This margin, alternating transform and oblique segments from Guinea to Nigeria, showsa strong structural variability in the margin width, continental geology and relief, drainage networks and subsidence/accumulation patterns. We analyzed this system combining onshore geology and geomorphology as well asoffshore sub-surface data.Mapping and regional correlation of dated lateritic paleo-landscape remnants allows us to reconstruct twophysiographic configurations ofWest Africa during the Cenozoic.We corrected those reconstitutions from flexuralisostasy related to the subsequent erosion. These geometries show that the present-day drainage organizationstabilized by at least 29 Myrs ago (probably by 34 Myr) revealing the antiquity of the Senegambia, Niger andVolta catchments toward the Atlantic as well as of the marginal upwarp currently forming a continental divide.The drainage rearrangement that lead to this drainage organization was primarily enhanced by the topographicgrowth of the Hoggar swell and caused a major stratigraphic turnover along the Equatorial margin of West Africa.Elevation differences between paleo-landscape remnants give access to the spatial and temporal distribution ofdenudation for 3 time-increments since 45 Myrs. From this, we estimate the volumes of sediments and associatedlithologies exported by the West African Craton toward different segments of the margin, taking into accountthe type of eroded bedrock and the successive drainage reorganizations. We compare these data to Cenozoicaccumulation histories in the basins and discuss their stratigraphic expression according to the type of marginsegment they are preserved in.

Published
2016

24. Very long-term stability of passive margin escarpment constrained by 40 Ar-39 Ar dating of K-Mn oxides

Author

Anicet Beauvais, Nicolas Arnaud, Nicolas J. Bonnet, Mudlappa Jayananda, Dominique Chardon, 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), Géosciences Environnement Toulouse (GET), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Centre National d'Études Spatiales [Toulouse] (CNES), 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), Bangalore University, Cefipra project 5007-1, INSU, IRD, Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-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), Aix Marseille Université (AMU), Institut de Recherche pour le Développement (IRD), Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), 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), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), 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
geography, Supergene (geology), geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Geology, Escarpment, 010502 geochemistry & geophysics, Fission track dating, Neogene, 01 natural sciences, Thermochronology, Paleontology, Continental margin, Denudation, 13. Climate action, Passive margin, 0105 earth and related environmental sciences
Abstract

The post-rift denudation history of high-elevation divergent continental margins is central to deciphering source-to-sink systems across such margins and to unraveling their topographic evolution. We performed 40Ar-39Ar dating of supergene K-Mn oxides from supergene manganese ore deposits in order to constrain the age of in situ formed laterites on both the lowland and highland sides of the Western Ghats Escarpment of Peninsular India. Documentation of laterites as old as 53 Ma on the highland and 47 Ma at the foot of the escarpment shows that the escarpment stabilized before 47 Ma (possibly 60 Ma). The topographic setting of the dated weathering mantles also constrains denudation of the lowland and the highland since ca. 50 Ma to maximums of 5 m/m.y. and 15 m/m.y., respectively. Our results challenge denudation rates derived from apatite fission track thermochronology by documenting the topography and relief longevity of the southwest Indian margin and its hinterland. The results preclude large-magnitude uplift of Peninsular India after the Eocene, and more generally argue against late Neogene uplift and topographic rejuvenation of continental shields.

Published
2016
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25. Active oblique ramp faulting in the Southern Tunisian Atlas

Author

Aymen Saïd, Jamel Ouali, Dominique Chardon, and Patrice Baby

Subjects
Seismic gap, geography, geography.geographical_feature_category, Active fault, Fault (geology), Induced seismicity, Fault scarp, Strike-slip tectonics, Geophysics, Seismic hazard, Basement (geology), Geology, Seismology, Earth-Surface Processes
Abstract

The Gafsa fault is the longest and most active structure of the fold-and-thrust belt achieving southeastward propagation of the Atlas belt of Eastern North Africa onto the Saharan platform. The Gafsa fault is a 75-km long dextral-oblique basement fault ramp that poses a sizable challenge in earthquake hazard assessment because the post-Paleozoic sedimentary cover is decoupled from its basement above the basement fault. In this study, we combine seismic lines interpretation, tectonic geomorphology and paleoseismological investigations to assess the level of seismic hazard of this fault and evaluate its role in the geodynamic framework of the Central Mediterranean. We show that despite a moderate instrumental and historical seismicity, the fault has produced M ≥ 6 earthquakes with a return period of ca. 500–5000 years during the Late Quaternary. The latest large event having produced a surface rupture on the fault occurred around 8000 yr BP, suggesting an M ≥ 6 earthquake is overdue on the fault. The fault has a minimum reverse component of slip rate of 0.21–0.34 mm/yr over the past 50 Ka. The occurrence of M ≥ 7 paleoearthquakes on the fault may be suspected but not established. Such very strong earthquakes would require transient coseismic linkage of the buried basement fault with the overlying listric fault ramping off the decollement layer. The level of seismic hazard may be underestimated on the Gafsa fault. Indeed, given the geometry of the basement–cover fault system, a number of earthquakes generated in the basement would have led to coseismic surface folding instead of to surface rupture. The Gafsa fault is a major structure accommodating eastward extrusion / spreading of the Atlas belt onto the Saharan and Pelagian plateforms above the retreating Ionian lithospheric slab.

Published
2011
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26. Application of Lu–Hf garnet dating to unravel the relationships between deformation, metamorphism and plutonism: An example from the Prince Rupert area, British Columbia

Author

Dominique Chardon, Christopher L. Andronicos, D. E. Wolf, Michael R. Mansfield, and Jeffery D. Vervoort

Subjects
Geophysics, Batholith, Pluton, Metamorphic rock, Geochemistry, Metamorphism, Suture (geology), Shear zone, Geomorphology, Plutonism, Geology, Transpression, Earth-Surface Processes
Abstract

The tectonic history of the Prince Rupert area is marked by profound crustal thickening from thrusting that produced inverted metamorphic field gradients and transpression in crustal-scale shear zones. Syn-tectonic garnet in the Prince Rupert area has Lu–Hf ages of 102.6 ± 3.7 Ma and 108.3 ± 4.1 Ma (2 σ ). Porphyroblast–matrix relationships in these samples, and samples from the same outcrops, indicate syn-tectonic garnet growth. These relationships imply that the garnet ages directly date the development of the metamorphic foliations. A third sample of migmatitic garnet amphibolite from the contact aureole of the 94–90 Ma Ecstall pluton had complex isotope systematics interpreted to indicate a garnet growth episode ∼ 105 Ma, similar to the ages obtained from the other samples and a growth or equilibration event at ∼ 94 Ma during pluton emplacement. The data show that the older Lu–Hf garnet ages date prograde metamorphism during foliation development and modification during pluton emplacement. The Ecstall pluton was emplaced 10 to 15 m.y. after regional metamorphism and thrust stacking in the Prince Rupert area. In order to place our samples in a regional tectonic context we compare our results to patterns of regional deformation, metamorphism and plutonism throughout the North American Cordillera in the time period between 110 and 85 Ma. Contractional and transpressional deformation occurred throughout much of the North American Cordillera at this time, from southeastern Alaska to the Baja Peninsula in Mexico. Left-lateral transpression dominated the Canadian Cordillera, whereas, right-lateral transpression affected areas south of the Idaho–Salmon River suture zone, including the Sierra Nevada batholith. This reversal in kinematics in the northern and southern cordillera within coeval magmatic belts appears to be a first-order feature of the geology of the North American Cordillera during the Cretaceous.

Published
2010
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27. Planation, bauxites and epeirogeny: One or two paleosurfaces on the West African margin?

Author

Violaine Chevillotte, Bruno Boulangé, Georges Grandin, Dominique Chardon, and Anicet Beauvais

Subjects
Peneplain, Gondwana, Paleontology, Planation surface, Passive margin, Phanerozoic, Epeirogenic movement, Cenozoic, Paleogene, Geology, Earth-Surface Processes
Abstract

Mapping of lateritic bauxites over the West African rifted margin and analysis of the geomorphic properties of these bauxites, combined with available geological data lead to a discussion of the presence of either two Meso-Cenozoic planation surfaces or a single Eocene surface to account for the morphotectonic and paleoclimatic evolution of the Guinean landforms. At large scale, two stepped bauxitic levels are documented. Ongoing or episodic uplift following Gondwana breakup and Meso-Cenozoic climate change are proposed to have allowed the formation and abandonment of an Early mid-Cretaceous surface today preserved as the higher bauxitic level, and the setting of an Eocene planation surface bearing a second generation of bauxites, making the lower bauxitic level. The single Eocene surface hypothesis requires that Paleogene bauxitization preserved large pre-existing relief to explain two stepped bauxitic levels of the same age. The two-surface hypothesis is favored because it would explain rebauxitization of alluvial pebbles of bauxites under the lower lateritic level.

Published
2006
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28. Long-term tropical morphogenesis of New Caledonia (Southwest Pacific): Importance of positive epeirogeny and climate change

Author

Violaine Chevillotte, Fabrice Colin, Dominique Chardon, Pierre Maurizot, Anicet Beauvais, 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)-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)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), and Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)

Subjects
epeirogeny, Paleoclimate, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Climate change, planation surface, Laterite, Neogene, Planation surface, Epeirogeny, Peneplain, Oceanography, New Caledonia, laterite, paleoclimate, Paleoclimatology, Epeirogenic movement, Cenozoic, Paleogene, Geology, Earth-Surface Processes
Abstract

International audience; Extensive mapping of relict lateritic landsurfaces over the 1600 m of relief of mainland New Caledonia is used to evaluate long-term morphogenesis of the island since its emergence in the Oligocene. The results support the interpretation of the lateritic levels as abandoned, stepped remnant landsurfaces that may be grouped into eight island-scale erosion levels recording episodic lowering of base level. The separation of the erosion levels results from the combination of positive epeirogenic movements of the New Caledonia continental ridge and long-term Neogene climate variability, which is recorded by the contrasted erosion and weathering patterns of the three youngest levels and tentatively correlated with known global and regional paleoclimatic events.

Published
2006
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29. 2.61Ga potassic granites and crustal reworking in the western Dharwar craton, southern India: Tectonic, geochronologic and geochemical constraints

Author

Jean-Jacques Peucat, Mudlappa Jayananda, R. Capdevila, Dominique Chardon, 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), 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
[SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Archean, Pluton, Geochemistry, Partial melting, Geology, 010502 geochemistry & geophysics, Granulite, 01 natural sciences, Dharwar Craton, Craton, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, Geochemistry and Petrology, Mafic, Petrology, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Zircon
Abstract

We present combined field, structural data and spot image analysis, petrographic data, U–Pb zircon ages, Nd isotopes and whole-rock geochemical data for the late Archaean granite plutons from Arsikere–Banavara (AB suite) and Chitradurga–Jampalnaikankote–Hosdurga (CJH suite), in the western Dharwar craton (WDC). AB plutons are syn-kinematic with respect to the development of dome-and-basin patterns resulting from partial crustal diapiric overturn (D1), whilst CJH suite plutons show deformation patterns resulting from the superimposition of large-scale regional strike-slip shearing (D2) onto D1 syn-emplacement fabrics. SIMS U–Pb zircon ages of 2614 ± 10 Ma for the Chitradurga pluton (CJH) and of 2617 ± 3 Ma for the Arsikere pluton (AB) define the minimum age of the D1 strain pattern. The CJH and AB suites are mainly high-K granites whose origin is to be sought in partial melting of an old (>3.0 Ga) depleted lower crust of intermediate composition. The CJH and AB suites correspond mainly to the CA1- and CA2-types of Archaean calc-alkaline granites and some facies to the transitional TTG. Their heterogeneous chemical compositions indicate involvement of various sources and also significantly different depths of partial melting to produce these granites. These results allow documenting regional partial reworking of the WDC 2615 Ma ago, requiring an HT event to have taken place before 2.61 Ga and thus different from the 2.55 to 2.51 Ga granulite facies metamorphic episode associated to regional-scale strike-slip shearing (D2) that affected the entire craton. Partial reworking of the older lower crust at 2.61 Ga and associated deformation would result from heat advection and/or crustal thickening that may relate to voluminous mafic greenstone volcanism and moderate shortening at that time.

Published
2006
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30. Morphotectonic evolution of the New Caledonia ridge (Pacific Southwest) from post-obduction tectonosedimentary record

Author

Dominique Chardon and Violaine Chevillotte

Subjects
normal faulting, Subduction, Pacific Plate, fault slip data, Transtension, tricision, planation surface, Neogene, transtension, Obduction, Geophysics, New Caledonia, Planation surface, Extensional tectonics, Sedimentary rock, seismic reflection, Seismology, Geology, aggradation, Earth-Surface Processes
Abstract

The tectonostratigraphic and geomorphic study of two post-obduction fluvial sedimentary systems on mainland New Caledonia and imaged offshore on seismic reflection lines provides a new perspective on the post-orogenic evolution of the New Caledonia ridge. Relations between sedimentary sequence boundaries, erosion surfaces and faults, both on land and on offshore seismic reflection profiles indicate that an episode of extensional tectonics initiated in the Early Neogene led to the disruption and collapse of the island landsurface previously shaped during a Latest Oligocene phase of planation. Microtectonic analysis further suggests early slip on the normal faults was associated with ridge-normal extension. A later set of faults accompanied ridge-parallel to ridgeoblique extension that is,interpreted to result from a shift toward a transtensional regime driven by the initiation of east-verging subduction of the Australian plate beneath the Pacific plate starting at least in the late Mid-Miocene. (c) 2006 Elsevier B.V. All rights reserved.

Published
2006
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31. Role of the Kazerun fault system in active deformation of the Zagros fold-and-thrust belt (Iran)

Author

Christine Authemayou, Olivier Bellier, Zaman Malekzade, Dominique Chardon, and Mohammad Abassi

Subjects
Global and Planetary Change, Focal mechanism, geography, geography.geographical_feature_category, Slip (materials science), Active fault, Fault (geology), Geodesy, Strike-slip tectonics, Sinistral and dextral, Epicenter, General Earth and Planetary Sciences, Zagros fold and thrust belt, Seismology, Geology
Abstract

Field structural and SPOT image analyses document the kinematic framework enhancing transfer of strike-slip partitioned motion from along the backstop to the interior of the Zagros fold-and-thrust belt in a context of plate convergence slight obliquity. Transfer occurs by slip on the north-trending right-lateral Kazerun Fault System (KFS) that connects to the Main Recent Fault, a major northwest-trending dextral fault partitioning oblique convergence at the rear of the belt. The KFS formed by three fault zones ended by bent orogen-parallel thrusts allows slip from along the Main Recent Fault to become distributed by transfer to longitudinal thrusts and folds. To cite this article: C. Authemayou et al., C. R. Geoscience 337 (2005).

Published
2005
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32. Géométrie et cinématique post-oligocène des failles d'Aix et de la moyenne Durance (Provence, France)

Author

Pierre Guignard, Dominique Chardon, and Olivier Bellier

Subjects
Stress field, Global and Planetary Change, geography, geography.geographical_feature_category, General Earth and Planetary Sciences, Slip (materials science), Fault (geology), Geomorphology, Geology
Abstract

Geometry and post-Oligocene kinematics of the Aix and Moyenne Durance faults (Provence, France). The southern termination of the left-lateral ‘Moyenne Durance’ Fault (FMD) consists in several segments, some being connected to WSWtrending south-verging reverse faults. To the south, the Aix fault is reactivated in a post-Oligocene strike-slip movement showing that these two faults might belong to the same system. This system seems to transfer, in turn, slip to the east-trending, southverging Trevaresse reverse fault, allowing southward propagation of the Alpine deformation front in western Provence. Fault kinematics analysis shows lateral stress field change between the two faults. Strike-slip stress state is characterized by an average N150 ◦ E trending σ 1 near the FMD termination, whilst strike-slip and reverse faulting stress states show north-trending σ1 to

Published
2005
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33. Geological boundary conditions of the 1909 Lambesc (Provence, France) earthquake : structure and evolution of the Trévaresse ridge anticline

Author

Dominique Chardon and Olivier Bellier

Subjects
Tectonics, geography, geography.geographical_feature_category, Seismotectonics, Anticline, Geology, Thrust fault, Diachronous, Fold (geology), Fault (geology), Fault scarp, Seismology
Abstract

Keywords. - SE France, Reverse faulting, Folding, Neogene-Quaternary, Seismotectonics. Abstract. - The 06/11/1909, Lambesc, M=6 earthquake is the strongest instrumental seismic event recorded in French history. A review of the geology of the epicentral area combined with detailed field mapping and structural analysis al- lows constraining the tectonic and geomorphic evolution of the Trevaresse ridge anticline and associated fault that rup- tured during the 1909 event. The Trevaresse fold is a WNW-trending, southerly-verging forced ramp anticline developed above the Trevaresse reverse fault during late Miocene and Pliocene times, and possibly after the early Pleistocene. Over the last 11 Ma, the Trevaresse reverse fault records an average reverse slip rate of 0.03 ± 0.02 mm/yr consistent with a homogeneous N005 - N010 trending shortening direction. The fault is segmented into two major segments (the eastern one being linked to a possibly active frontal blind thrust fault) separated by a relay fault zone associated with an en-echelon fold pattern con- sistent with a slight left-lateral component on the easternmost segment. Our structural analysis combined with recent es- timates of the source parameters of the Lambesc earthquake indicates that the fault has to reach at least the basement- cover interface, at a minimum depth of 6 km. The westward longitudinal decrease in morphological maturity of the re- lief of the Trevaresse ridge anticline and its associated fault scarp suggests a westward propagation of the fold during partly diachronous activation of the two segments of the fault.

Published
2003
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34. Strain partitioning and batholith emplacement at the root of a transpressive magmatic arc

Author

Dominique Chardon

Subjects
Strain partitioning, Sinistral and dextral, Back-arc basin, Oceanic crust, Batholith, Geology, Shear zone, Petrology, Geomorphology, Plutonism, Transpression
Abstract

An integrative study of the high-pressure Ecstall batholith and its country rocks (Prince Rupert area, British Columbia) reveals the interplay of deformation and plutonism produced in the largest Cordilleran magmatic arc (i.e. the Coast Plutonic Complex) during mid-Cretaceous convergence between the Farallon oceanic plate and North America. The results emphasize the interference between three strain fields: (1) an early (>92 Ma) crustal wedge produced by orogen-perpendicular, SW-vergent thrusting, (2) an orogen-parallel sinistral strike-slip shear zone active until 87 Ma, and (3) the lateral expansion of the batholith (93–91 Ma) against the shear zone. The batholith expanded in a direction oblique with respect to the shear zone trend (+20°) by extruding country rocks against its head in a direction normal to its expansion direction during sinistral, strike-slip partitioned transpression. The batholith's emplacement combined far-field batholith boundary-normal translation, extrusion-related rotation and radial and concentric elongation in its structural aureole. This case study may typify the process by which a modern magmatic arc grows longitudinally at depth during transpression, the direction and sense of growth being determined by the direction of plate motion relative to the magmatic arc and the degree of strike-slip partitioning of transpression.

Published
2003
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35. Neogene cratonic erosion fluxes and landform evolution processes from regional regolith mapping (Burkina Faso, West Africa)

Author

Anicet Beauvais, Jean-Louis Grimaud, Dominique Chardon, Ousmane Bamba, Václav Metelka, Géosciences Environnement Toulouse (GET), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Centre National de la Recherche Scientifique (CNRS), Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), 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), Aix Marseille Université (AMU), Institut de Recherche pour le Développement (IRD), Université Joseph Ki-Zerbo [Ouagadougou] (UJZK), ARC Linkage Project LP110100667WAXI project (P934A)Centre National de la Recherche Scientifique (CNRS) France, Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT), 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), Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-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), Université de Ouagadougou, WAXI, CNRS, ANR-08-BLAN-0247,TOPOAFRICA,Evolution of the African topography over the last 250 My from the sedimentary record to mantle dynamics(2008), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Centre National d'Études Spatiales [Toulouse] (CNES)

Subjects
Pediment, 010504 meteorology & atmospheric sciences, EROSION, Lithology, CRATON, Drainage basin, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, 010502 geochemistry & geophysics, SEDIMENT, 01 natural sciences, Regolith, Landform evolution processes, NEOGENE, REGOLITHE, Geomorphology, LATERITE, CARTOGRAPHIE, 0105 earth and related environmental sciences, Earth-Surface Processes, geography, geography.geographical_feature_category, Landform, Bedrock, Sediment routing system, Source to sink, TELEDETECTION SPATIALE, GEOMORPHOLOGIE, TOPOGRAPHIE, Denudation, Clastic rock, Erosion, Geology
Abstract

The regionally correlated and dated regolith-paleolandform sequence of Sub-Saharan West Africa offers a unique opportunity to constrain continental-scale regolith dynamics as the key part of the sediment routing system. In this study, a regolith mapping protocol is developed and applied at the scale of Southwestern Burkina Faso. Mapping combines field survey and remote sensing data to reconstruct the topography of the last pediplain that formed over West Africa in the Early and Mid-Miocene (24-11 Ma). The nature and preservation pattern of the pediplain are controlled by the spatial variation of bedrock lithology and are partitioned among large drainage basins. Quantification of pediplain dissection and drainage growth allows definition of a cratonic background denudation rate of 2 m/My and a minimum characteristic timescale of 20 Ma for shield resurfacing. These results may be used to simulate minimum export fluxes of drainage basins of constrained size over geological timescales. Background cratonic denudation results in a clastic export flux of similar to 4 t/km(2)/year, which is limited by low denudation efficiency of slope processes and correlatively high regolith storage capacity of tropical shields. These salient characteristics of shields' surface dynamics would tend to smooth the riverine export fluxes of shields through geological time. Published by Elsevier B.V.

Published
2015
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36. Paleo- to Mesoarchean TTG accretion and continental growth in the western Dharwar craton, Southern India: Constraints from SHRIMP U–Pb zircon geochronology, whole-rock geochemistry and Nd–Sr isotopes

Author

Tushipokla, Christopher Fanning, Jean-Jacques Peucat, Dominique Chardon, Mudlappa Jayananda, University of Delhi, Géosciences Environnement Toulouse (GET), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), 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), Research School of Earth Sciences [Canberra] (RSES), Australian National University (ANU), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), 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
Geochemistry, Geology, Oceanic plateau, Crust, engineering.material, Nd–Sr isotopes, Mantle (geology), Dharwar Craton, SHRIMP U–Pb zircon ages, Continental growth, Geochemistry and Petrology, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, engineering, Dharwar craton, Island arc, Whole rock geochemistry, 14. Life underwater, Mafic, Petrology, Archean TTG, Zircon, Hornblende
Abstract

International audience; A multidisciplinary study involving field, petrographic, SHRIMP U–Pb zircon/titanite ages, whole rock geochemical and Nd–Sr isotope data is presented for the Peninsular Gneisses and associated plutons forming core of the Dharwar craton. Two major periods (3350–3280 Ma and 3230–3200 Ma) of crustal growth through TTG accretion sub-contemporaneous with greenstone volcanism are documented. Elemental and Nd–Sr isotope data suggest that the TTGs originated by low and high pressure melting of heterogeneous mafic sources (thickened island arc or oceanic plateau crust) at different depths. Among the early accreted TTGs, magmatic protoliths of low-Al gneisses formed by low-pressure (10–12 kbar) melting of a depleted mafic source at shallow levels (island arc type crust) with plagioclase + amphibole ± ilmenite in the residue, whilst high-Al gneisses were probably produced by high pressure melting (14–18 kbar) of a chondritic or a less depleted mafic source with garnet ± amphibole ± pyroxene + ilmenite in the residue (base of Island arc crust or thickened oceanic plateau). The 3230–3200 Ma trondhjemitic plutons marking the second accretion event derived by higher pressure (14–16 kbar) melting of a mafic source (island arc type crust with garnet ± plagiocalse ± hornblende + ilmenite) with a minor involvement of previously accreted TTGs. This plutonism was coeval with a major phase of crustal-scale diapiric overturn that had a major imprint on crustal reworking. A later magmatic episode at ca. 3100 Ma produced granitic plutons derived from crustal melting and leucocratic gneisses derived from a depleted mafic source in the lower crust. Documentation of depleted shallow and deep mantle reservoirs during 3350–3280 Ma magmatism implies massive differentiation of the mantle during an earlier episode of crust formation around 3800–600 Ma, as substantiated by Nd model ages and published Pb-isotope data, as well as U–Pb detrital zircon ages with in situ Hf isotope data.

Published
2015
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37. Very long-term incision dynamics of big rivers

Author

Dominique Chardon, Anicet Beauvais, Jean-Louis Grimaud, Géosciences Environnement Toulouse (GET), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Centre National d'Études Spatiales [Toulouse] (CNES), 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), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT), 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), Aix Marseille Université (AMU), Institut de Recherche pour le Développement (IRD), ARC Linkage Project LP110100667WAXI project (P934A)Centre National de la Recherche Scientifique (CNRS), France, Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), Université Fédérale Toulouse Midi-Pyrénées, and 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)

Subjects
EOCENE, CENOZOIQUE, DRAINAGE, INCISION, LITHOGENESE, Inversion (geology), PALEOGEOMORPHOLOGIE, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, DYNAMIQUE, Routing (hydrology), Paleontology, VARIATION TEMPORELLE, PROFIL EN LONG, non-orogenic, NIVEAU DE L'EAU, Continental margin, Geochemistry and Petrology, incision dynamics, Shield, Earth and Planetary Sciences (miscellaneous), SEDIMENTATION FLUVIATILE, river long profiles, Geomorphology, Cenozoic, CONFIGURATION DU LIT, Sediment, 15. Life on land, TOPOGRAPHIE, ETALONNAGE, MODELISATION, Swell, Ocean surface topography, COURS D'EAU, Geophysics, 13. Climate action, Space and Planetary Science, VARIATION SPATIALE, Africa, knickzones, PALEODRAINAGE, Geology, TECTONIQUE
Abstract

International audience; Constraining large-scale incision dynamics of shield and post-rift margin domains is key to understanding the sediment routing system over the overwhelming part of the continental surface. Based on dated and regionally correlated incision markers from West Africa, we reconstruct for the first time the entire paleo-long profiles of big rivers such as the Niger at ca. 24, 11 and 6 Ma, as well as the Eocene topography those rivers have dissected. The results provide boundary conditions and calibration for surface process models and paleodrainage dynamics. Though spatially and temporally variable, incision remained mostly below 10 m/my with a mean around 5 m/my. The spatial stability of both the river outlets and divides imposed maintenance or increasing concavity of the river long profiles through time, resulting from spatially contrasted adjustment of river segments bounded by recurrent lithogenic knickzones that persisted since 24 Ma. Drainages evolved preferentially by very slow slope decrease or uniform incision in between the stationary knickzones of evolving amplitude, with apparently no relation to base level change. Therefore, knickzone height or position may not simply reflect the transient response of big rivers to base level fall as predicted by stream-power incision river models. This may also challenge uplift histories of deep continental interiors retrieved from river long profiles inversion relying on such models. Very slow incision allowed amplification of the Hoggar hot spot swell and flexural uplift of the continental margin to be recorded by river long profiles, emphasizing the potential of big non-orogenic rivers as gauges of dynamic topography.

Published
2014
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38. Large-scale transpressive shear zone patterns and displacements within magmatic arcs: The Coast Plutonic Complex, British Columbia

Author

Christopher L. Andronicos, Dominique Chardon, and Lincoln S. Hollister

Subjects
Paleontology, Geophysics, Sinistral and dextral, Shear (geology), Geochemistry and Petrology, Back-arc basin, Batholith, Plate reconstruction, Shear zone, Geology, Seismology, Transpression, Terrane
Abstract

The Coast Plutonic Complex is the largest magmatic arc of the North American Cordillera, extending from northwestern Washington State to eastern Alaska. It forms the transition between two tectonic domains that are suspected to have undergone several phases of large (several thousands of kilometers) orogen-parallel displacement during the Mesozoic and early Cenozoic. A compilation of fabric data, published isotopic ages, and new structural observations shows that the western Coast Plutonic Complex was affected by subvertical, orogen-parallel, crustal-scale shear zones. These shear zones mainly reflect sinistral transpression and were sequentially active from ∼110 to 87 Ma during the intrusion of voluminous batholiths. Sinistral shearing was roughly coeval with the development of the thrust belts flanking the Coast Plutonic Complex (between ∼101 and ∼85 Ma), suggesting plate-scale transpression was a first-order process in the construction of the Coast Mountains orogen. These shear zones separate panels with distinct plutonic and cooling histories, suggesting the sinistral displacements between crustal blocks were large (greater than tens to hundreds of kilometers). This transpressive shear system likely reflects the Jurassic to early Late Cretaceous migration of outboard Cordilleran terranes to the south suggested by paleomagnetic evidence and plate reconstruction models. This example from the Coast orogen shows how transpression is partitioned between a thermally weakened magmatic arc and outwardly vergent fold-and-thrust belts. Our analysis further shows that the ∼2000-km-long Late Cretaceous to early Tertiary Coast shear zone has a minimum extent toward the south to at least 51°30′N.

Published
1999
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39. Kinematics and tectonic significance of transpressive structures within the Coast Plutonic Complex, British Columbia

Author

Cameron Davidson, Dominique Chardon, Lincoln S. Hollister, and Christopher L. Andronicos

Subjects
Shearing (physics), geography, geography.geographical_feature_category, Geology, Overprinting, Transpression, Paleontology, Lineation, Sinistral and dextral, Sill, Shear zone, Seismology, Terrane
Abstract

Structural data from the Coast Plutonic Complex, near Prince Rupert, British Columbia, are consistent with a deformational history dominated by dextral transpression from Campanian to Paleocene time. Penetrative east-side-up, southwest-directed, ductile shearing produced moderately northeast-plunging overturned kilometer-scale isoclinal folds. These folds are dextrally sheared and refolded into kilometer-scale upright northwest-plunging folds and steeply dipping transposed foliations with moderate to shallow northwest-plunging lineations along their western side. An east-side-up component to the transcurrent shearing is kinematically compatible with east-side-up shearing found within the Great Tonalite Sill. Kinematic and geometric gradients and the spatial distribution of the finite stretching direction are interpreted to result from partitioning of transpression. The location of these structures and overprinting relationships suggest the Great Tonalite Sill intruded late-kinematically into a crustal-scale dextral transpressive shear zone. These results indicate this shear zone could form part of the Baja-B.C. fault system that would have accommodated large northward displacements of the terranes making up western British Columbia and southeast Alaska. This conclusion is based on: (1) It is favorably located to accommodate the proposed displacements; (2) Deformation occurred during the time period of proposed large displacement (83–59 Ma); (3) The 15-km thickness of the shear zone indicates it records large displacements.

Published
1999
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40. Sinking of the Dharwar Basin (South India): implications for Archaean tectonics

Author

Pierre Choukroune, Mudlappa Jayananda, and Dominique Chardon

Subjects
geography, Underplating, geography.geographical_feature_category, Continental crust, Geochemistry, Geology, Greenstone belt, Geophysics, Dharwar Craton, Craton, Tectonics, Basement (geology), Continental margin, Geochemistry and Petrology
Abstract

Archaean tectonic regimes can be constrained by structural analysis of greenstone belts and adjacent granite-gneiss masses. The late Archaean Bababudan greenstone belt (Dharwar craton, South India) contains a low-grade volcanosedimentary basin sequence (the Dharwar Supergroup) which unconformably overlies a previously eroded basement made up mainly of granite and gneiss. Fabric trajectories, kinematic indicators and superimposed deformation patterns show that greenstones have undergone a radial converging downward flow with respect to underlying basement rocks, as well as strike-slip shearing. This is attributed to the progressive sagduction (gravity-sinking) of the greenstone belt into its basement along a decollement horizon and to late transcurrent shearing. We propose a deformation model for the Bababudan belt that may explain common features of many greenstone belts (such as decollements and superimposed upright fold patterns) which are attributed to the progressive sinking of the supracrustals into their basement. The results of our study and other field investigations in the crust of the Dharwar craton, as well as structural evidence from other cratons (Zimbabwe and Pilbara), raise the possibility that a unique continental tectonic regime existed during the Archaean, controlled by the emplacement of dense volcanic traps, mantle underplating and thermal blanketing of the continental crust. This tectonic regime differs from that observed within the modern lithosphere as it is characterized by the pervasive development of gravity (i.e. Rayleigh-Taylor) instabilities between the volcanic traps and the rest of the continental crust. It allowed heat and material transfer through the crust and has to be seen as an efficient recycling mechanism for the young continental crust during periods of mantle underplating. The diapiric phenomenon is independent of the boundary forces acting at the limits of the protocontinents and is associated in time and space with large-scale accretion events of the continental crust, perhaps in hot-spot environments.

Published
1998
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41. First 40Ar/39Ar dating of intense Late Palaeogene lateritic weathering in Peninsular India

Author

Nicolas J. Bonnet, Anicet Beauvais, Mudlappa Jayananda, Dominique Chardon, Nicolas Arnaud, Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), 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), Aix Marseille Université (AMU), Institut de Recherche pour le Développement (IRD), Centre National de la Recherche Scientifique (CNRS), Géosciences Montpellier, Université des Antilles et de la Guyane (UAG)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Géosciences Environnement Toulouse (GET), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), Department of Geology, Centre of Advanced Studies, University of Delhi, IRD, INSU, 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), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Centre National d'Études Spatiales [Toulouse] (CNES), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-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), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)

Subjects
Supergene (geology), PALEOGENE, CRATON, Geochemistry, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Weathering, Neogene, DATATION, Geochemistry and Petrology, lateritic paleolandsurface, Earth and Planetary Sciences (miscellaneous), Deccan Traps, ANALYSE ISOTOPIQUE, LATERITE, supergene Mn-ore deposits, geography, geography.geographical_feature_category, Plateau, ALTERATION, South India, 40Ar/39Ar radiometric dating, 15. Life on land, cryptomelane, Sandur greenstone belt, Craton, Geophysics, 13. Climate action, Space and Planetary Science, Outwash plain, Paleogene, Geology
Abstract

International audience; Lateritic surface processes have shaped large platform and cratons of the tropical belt. Constraining the timing of such processes is crucial to decipher their role in cratonic morphogenesis and their response to long-term climatic change and lithospheric deformation. Weathering histories have been documented for South America, Africa and Australia, but precise time constraints of the lateritic weathering processes in South India are still lacking. We present 40Ar/39Ar ages of supergene cryptomelane (K-Mn oxide) formed in the Sandur Mn ore deposits exposed on the highest lateritic paleolandsurface that once covered the Mysore plateau and the adjacent Deccan Traps. Significant 40Ar/39Ar ages are estimated between ~ 36 and ~ 26 Ma from well-defined plateaus in step heating 39Ar release spectra and from best-fitted inverse isochrones. These ages constitute firm time constraints that document intense late Eocene-Oligocene lateritic weathering over Peninsular India under the influence of warm and wet climate comparable to that prevailing in tropical humid forests. These results imply that Southern India was weathered between ~ 36 and 26 Ma and may have been dissected mostly in the Neogene.

Published
2014
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44. The lower crust of the Dharwar Craton, southern India: patchwork of Archean granulitic domains

Author

Mudlappa Jayananda, C. Mark Fanning, Dominique Chardon, Ramon Capdevila, Jean-Louis Paquette, Jean-Jacques Peucat, Terre, Temps, Traçage, 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)-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), Department of Geology, University of Dehli, Laboratoire des Mécanismes et Transfert en Géologie (LMTG), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Research School of Earth Sciences [Canberra] (RSES), Australian National University (ANU), Laboratoire Magmas et Volcans (LMV), Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-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), 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), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet [Saint-Étienne] (UJM)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), and Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
U-Pb geochronology, Paleoarchean, Archean, Geochemistry, Metamorphism, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, 010502 geochemistry & geophysics, 01 natural sciences, Dharwar Craton, Geochemistry and Petrology, 010503 geology, Petrology, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, Crustal recycling, South India, Structure, Geology, Orogeny, Massif, Neoarchean, 15. Life on land, Granulite, Granulites, Shear zone
Abstract

International audience; U-Pb geochronological, major and trace element and isotope geochemical data identify crustal domains of contrasted petrological origins and histories in the lower crust of the Dharwar Craton, all affected by granulite facies metamorphism and deformation in the Neoarchean. Four lower crustal domains have been identified and investigated across the Neoarchean amphibolite to granulite facies transition zone. (1) In the southern part of the Western Dharwar Craton (WDC), high-grade metamorphism affects rocks formed before 3.0 Ga. High-grade metamorphism is recorded at ca 2.51 Ga, followed by possible complex cooling and/resetting until 2.2 Ga. (2) The BR Hills-MM Hills domain represents the lower crust of the Central Dharwar Province (CDP) which is here defined as a transitional crust between the old (>3 Ga) WDC and the Eastern Dharwar Province (EDP), not older than 2.7 Ga. This granulitic domain contains the oldest rocks of the Dharwar Craton with TTG suites formed at ca 3.4 Ga and ca 2.6 Ga suites of probable crustal recycling origin. Both suites are involved in 2513±5Ma granulite facies metamorphism. (3) The Nilgiri granulitic domain is tectonically juxtaposed with the deepest level of the WDC as a consequence of Neoarchean dextral slip along the Moyar shear zone. The massif consists of rocks of orogenic affinities formed between 2.70 and 2.56 Ga and overprinted by granulite facies metamorphism at 2518±10 Ma. (4) The Krishnagiri domain exposes the deepest levels of the Eastern Dharwar Craton. It is composed of TTG and calc-alkaline igneous protoliths formed between 2.55 and 2.53 Ga. Migmatization in the upper part of the domain took place at 2507±6Ma and granulite facies overprint in the deepest parts of the domain is constrained at 2516±5 Ma. The Krishnagiri domain was magmatically accreted to the lower crust of both the CDP and EDP by interaction with mafic magmatism, inducing reworking of the 2.7-2.6 Ga or older overlying crust. The Nilgiri granulites share several temporal and petrological properties with the Madras granulites that make the easternmost outcrop of the Dharwar Craton. We tentatively suggest that the Nilgiri and Madras granulites evolved as parts of a common Madras domain in the lower crust of the EDP before activation of the Moyar shear zone. In this sense, the Nilgiri massif may be considered as an allochtonous unit in a context of Neoarchean ultra hot orogeny in South India.

Published
2013
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45. Neoarchean greenstone volcanism and continental growth, Dharwar craton, southern India: Constraints from SIMS U-Pb zircon geochronology and Nd isotopes

Author

Mudlappa Jayananda, B. Krishna Rao, Dominique Chardon, Christopher Fanning, Fernando Corfu, J-J Peucat, Department of Geology, University of Dehli, Terre, Temps, Traçage, 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)-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), Laboratoire des Mécanismes et Transfert en Géologie (LMTG), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Research School of Earth Sciences [Canberra] (RSES), Australian National University (ANU), 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 de Toulouse (UT)-Université de Toulouse (UT)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)

Subjects
010504 meteorology & atmospheric sciences, Archean, Geochemistry, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Greenstone belt, 010502 geochemistry & geophysics, 01 natural sciences, Dharwar Craton, Continental growth, Geochemistry and Petrology, Nd isotopes, Petrology, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, Felsic, Geology, Neoarchean, 15. Life on land, Volcanic rock, Craton, SIMS zircon geochronology, Dharwar craton, Mafic, Felsic volcanics, Zircon
Abstract

International audience; We present SIMSU-Pbzircon ages andNdisotope data for the felsic volcanic rocks from seven Neoarchean greenstone belts of the Eastern Dharwar craton (EDC) and from the Chitradurga greenstone belt in the Western Dharwar craton (WDC). Zircon ages show bimodal age distribution of felsic volcanism. The ca. 2.70-2.65 Ga felsic volcanic event is contemporaneous with 2.7 Ga mafic greenstone volcanism and emplacement of juvenile tonalitic to granodioritic crust, while 2.58-2.54 Ga felsic volcanics are coeval and spatially (and probably genetically in some cases) linked to the major episode calc-alkaline magmatic accretion in the EDC. The Chitradurga and Veligallu greenstone belts host felsic volcanics of the first generation, the latter showing inheritance at ca. 2.95 Ga. Four of the five greenstone belts hosting the second generation of felsic volcanics (Chitradurga, Kolar, Kadiri, Hutti) show crustal inheritance at ca. 2.6, 2.7, 2.9, 3.0, 3.1 and 3.3 Ga. åNdt indicate derivation of the felsic volcanics from juvenile sources or short-lived crustal sources with minor influence of older crust. The new and existing data are consistent with two-stage growth of the Dharwar craton in the Neoarchean. First-stage accretion led to the growth of a 2.7-2.6 Ga juvenile crustal province of mafic volcanics and felsic plutons along the eastern margin of the WDC. Second-stage accretion (2.58-2.52 Ga) led to the emplacement of TTG and calc-alkaline plutons and felsic volcanics throughout the Eastern Dharwar craton. An active margin context could apply for the two-stage accretion scenario considering a west-dipping subducting slab beneath the craton in the framework of long-lived ultra-hot accretionary orogen. But the great width of influence of magmatic accretion and/or reworking, particularly during the second stage, would suggest large-scale mantle flow reorganization that would have generated large plume(s).

Published
2013
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46. Strain patterns in Archaean dome-and-basin structures: The Dharwar craton (Karnataka, South India)

Author

Pierre Choukroune, Hugues Bouhallier, and Dominique Chardon

Subjects
geography, geography.geographical_feature_category, Continental crust, Archean, Crust, Diapir, Dharwar Craton, Dome (geology), Craton, Geophysics, Space and Planetary Science, Geochemistry and Petrology, Finite strain theory, Earth and Planetary Sciences (miscellaneous), Petrology, Seismology, Geology
Abstract

Models simulating the role of gravity in the Earth's crust are the main source of criteria used for the field identification of diapirs. After a short review of the distribution of finite strain in experimental diapir models, we describe an example where differential erosion of a tilted craton has provided 3D geometrical information on patterns in a diapiric system at various depths (from greenschist to granulitic facies conditions) within the Archaean continental crust of the Dharwar craton, South India. Diapirs and anti-diapirs (‘sagducted’ greenstones) are observed at different levels: structures and strain are consistent with all the field identification criteria inferred from experimental simulation, but some peculiar structural features are also observed which are not predicted by the models. These features, such as strain trajectory triple junctions, result from (i) the progressive deformation of diapiric domes or sagducted basins, (ii) interferences between diapiric structures (body forces) and (iii) the superimposition of diapiric strain fields on regional horizontal shortening (boundary forces).

Published
1995
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47. Structure, paleogeographic inheritance, and deformation history of the southern Atlas foreland fold and thrust belt of Tunisia

Author

Jamel Ouali, Patrice Baby, Dominique Chardon, and Aymen Saïd

Subjects
geography, Décollement, geography.geographical_feature_category, Rift, Fault (geology), Neogene, Graben, Paleontology, Tectonics, Geophysics, Geochemistry and Petrology, Fold and thrust belt, Foreland basin, Geology, Seismology
Abstract

[1] Structural analysis of the southern Tunisian Atlas was carried out using field observation, seismic interpretation, and cross section balancing. It shows a mix of thick-skinned and thin-skinned tectonics with lateral variations in regional structural geometry and amounts of shortening controlled by NW-SE oblique ramps and tear faults. It confirms the role of the Late Triassic–Early Jurassic rifting inheritance in the structuring of the active foreland fold and thrust belt of the southern Tunisian Atlas, in particular in the development of NW-SE oblique structures such as the Gafsa fault. The Late Triassic–Early Jurassic structural pattern is characterized by a family of first-order NW-SE trending normal faults dipping to the east and by second-order E-W trending normal faults limiting a complex system of grabens and horsts. These faults have been inverted during two contractional tectonic events. The first event occurred between the middle Turonian and the late Maastrichtian and can be correlated with the onset of the convergence between Africa and Eurasia. The second event corresponding to the principal shortening tectonic event in the southern Atlas started in the Serravalian-Tortonian and is still active. During the Neogene, the southern Atlas foreland fold and thrust belt propagated on the evaporitic decollement level infilling the Late Triassic–Early Jurassic rift. The major Eocene “Atlas event,” described in hinterland domains and in eastern Tunisia, did not deform significantly the southern Tunisian Atlas, which corresponded in this period to a backbulge broad depozone.

Published
2011
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48. Lateral constrictional flow of hot orogenic crust: Insights from the Neoarchean of south India, geological and geophysical implications for orogenic plateaux

Author

Jean-Jacques Peucat, Mudlappa Jayananda, and Dominique Chardon

Subjects
geography, Plateau, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Archean, Transtension, Crust, Geophysics, 010502 geochemistry & geophysics, 01 natural sciences, Dharwar Craton, Tectonics, 13. Climate action, Geochemistry and Petrology, Lithosphere, Geology, 0105 earth and related environmental sciences, Zircon
Abstract

This study provides an in situ geological perspective on fabrics produced by synconvergence lateral crustal flow of hot orogens. It is based on the example of the Neoarchean orogen of the Dharwar craton (India) and combines structural analysis and ion microprobe U-Pb zircon geochronology. We document a pervasive, three-dimensional flow mode of the lower crust, called lateral constrictional flow (LCF), which combines orogen-normal shortening, lateral constrictional stretching, and transtension. LCF achieves gravity-driven flow, lateral escape, and 3-D mass redistribution in a viscous lower crust submitted to convergence. LCF tends to mechanically and thermally homogenize the lower crust and efficiently compensates topographic relief at a shallow level in the crust. Three type-geodynamic contexts are envisaged for LCF: plateau interiors, inner parts of collisional crustal wedges or plateau edges, and throughout wide ultrahot orogens such as the Neaoarchean orogen of south India. LCF makes the lower crust act as a strain gauge between lateral gravitational collapse or tectonic thickening of the upper crust, thrust stacking in the lowermost crust (collisional crustal wedge case), crustal shortening, and/or lateral flow of the upper mantle. In the case of plateau interiors or ultrahot orogens, LCF of a thick lower crust enables coupling of upper crustal deformation with upper mantle flow through a hot and thin lithosphere being shortened coherently. LCF generates a subhorizontal lamination that should produce the strong seismic reflectivity and lateral anisotropy of the Tibetan Plateau and a variety of hot orogens.

Published
2011
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49. Quaternary slip-rates of the Kazerun and the Main Recent Faults: active strike-slip partitioning in the Zagros fold-and-thrust belt

Author

Bernard Angeletti, Olivier Bellier, Christine Authemayou, Christelle Claude, M. R. Abbassi, Lucilla Benedetti, Zaman Malekzade, Dominique Chardon, Esmaeil Shabanian, 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), Université européenne de Bretagne - European University of Brittany (UEB), 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), Laboratoire des Mécanismes et Transfert en Géologie (LMTG), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), International Institute of Earthquake Engineering and Seismology, 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 Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut d'écologie et environnement-Observatoire des Sciences de l'Univers-Université de Brest (UBO)-Institut national des sciences de l'Univers (INSU - 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 Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, Continental tectonics: strike-slip and transform, 010504 meteorology & atmospheric sciences, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], Continental neotectonics, [SDE.MCG]Environmental Sciences/Global Changes, [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], Slip (materials science), STREAMS, Seismicity and tectonics, 010502 geochemistry & geophysics, Strike-slip tectonics, 01 natural sciences, Geophysics, Sinistral and dextral, Tectonics and landscape evolution, Geochemistry and Petrology, Gps data, Zagros fold and thrust belt, Quaternary, Geology, Seismology, 0105 earth and related environmental sciences, Slip rate
Abstract

International audience; The aim of this work is to constrain the Late Quaternary activity of two major dextral strike-slip faults of the Zagros fold-and-thrust belt of Southern Iran, within the framework of right-oblique convergence between Arabia and Eurasia. The NW-trending Main Recent fault marks the rear of the belt along two thirds of its length. Its southeastern tip connects to the northern termination of the N-trending Kazerun Fault, which affects the entire width of the belt. Horizontal slip rates have been estimated on these two faults over the last 140 ka from lateral offsets of streams and fans and in situ cosmogenic 36Cl exposure dating of cobbles sampled on the surface of these geomorphic features. Compared to GPS data, the obtained minimum slip rate of 3.5–12.5 mm yr−1 on the Main Recent Fault implies strike-slip partitioning of the convergence along this fault. Minimum slip rate of the Kazerun Fault is 2.5–4 mm yr−1 for its northern strand, 1.5–3.5 mm yr−1 for its central segment and is negligible for its southern segment. These results are consistent with southward distribution of the slip from along the Main Recent Fault to the longitudinal thrusts and folds of the fold-and-thrust belt through the Kazerun Fault, with a decrease of slip from the southeastern tip of the Main Recent Fault towards the southern termination of the Kazerun Fault. The Kazerun and associated faults form the horsetail termination of the Main Recent fault and may be seen as the propagating southeastern front of the fault system that accommodates indentation of Eurasia by Arabia.

Published
2009
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50. Precambrian continental strain and shear zone patterns: South Indian case

Author

Mudlappa Jayananda, Dominique Chardon, T.R.K. Chetty, and Jean-Jacques Peucat

Subjects
Atmospheric Science, 010504 meteorology & atmospheric sciences, Archean, Soil Science, Aquatic Science, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Transpression, Mantle (geology), Dharwar Craton, Precambrian, Geochemistry and Petrology, Lithosphere, Earth and Planetary Sciences (miscellaneous), Petrology, Geomorphology, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, geography, geography.geographical_feature_category, Ecology, Paleontology, Forestry, Craton, Geophysics, Space and Planetary Science, Shear zone, Geology
Abstract

This study addresses the tectonic and mechanical significance of crustal-scale strain and shear zone patterns in the South Indian Precambrian lithosphere. It is based on a tectonic map of the Dharwar craton derived from LANDSAT imagery, existing documentation, and our own field observations. We document the contrasted responses of the two main parts of the craton to late Archean (2.56­2.51 Ga) shortening. The old (>3 Ga) lithosphere of the Western Dharwar craton stabilized at 2.61 Ga underwent moderate shortening and strain localization along spaced shear zones. The Eastern Dharwar craton, rejuvenated by late Archean juvenile magmatic accretion, responded to shortening by flowing laterally against the Western Dharwar craton. Shortening operated without significant thickening because of the high buoyancy of the juvenile crust and the very low strength of its mantle lithosphere. The late Archean crustal-scale shear zone network did not accommodate large displacements and only contributed to smoothing out of strain heterogeneities during the latest stages of flow. The shear zone pattern only reflects the symmetry of the regional finite strain field of a wide hot orogen. It does not result from terrain amalgamation but accompanies crustal flow and does not compare with those of modern active margins, which accommodate unidirectional transpression. Our analysis further suggests that the shear zones bounding the craton did not record large horizontal displacements during final assembly of Gondwana but rather transverse shortening and vertical extrusion.

Published
2008
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