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7. Differentiated Neogene bauxitization of volcanic rocks (westernCameroon): Morpho-geological constraints on chemical erosion (vol 194,104685, 2020)

Author

Momo, Mathieu Nouazi, Beauvais, Anicet, Tematio, Paul, Yemefack, Martin, Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), and 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)

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

National audience

Published
2021
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8. Chemical and physical transfers in an ultramafic rock weathering profile: part 2. dissolution vs. accumulation of platinum group minerals

Author

Traore, Daouda, Beauvais, Anicet, Auge, Thierry, Parisot, Jean Claude, Colin, Fabrice, and Cathelineau, Michel

Subjects
Rocks, Ultrabasic -- Chemical properties, Rocks, Ultrabasic -- Mechanical properties, Weathering -- Research, Earth sciences
Abstract

The chemical weathering of ultramafic rocks has resulted in eluvial concentration of Pt-group minerals (PGM) in lateritic weathering profiles of southern New Caledonia. The Pt mineralization interpreted as being primary consists of Pt-group minerals included within chromite crystals. The occurrence of PGM as free particles in the weathering profile results from the supergene dissolution of Pt-bearing chromite (Traore et al. 2008). Following their release in the profile, supergene dissolution processes variably affect the PGM particles. The behavior of Pt-group elements in the weathering profile is characterized by significant loss of Pd and relative enrichment of Pt indicating that Pd is more mobile than Pt in the exogenous cycle. Unstable Pt-Fe-Cu-Pd alloys and PGE oxides undergo chemical and mineralogical changes to acquire the chemical configuration ofisoferroplatinum ([Pt.sub.3]Fe), which is the most stable Pt phase in a lateritic environment. The isoferroplatinum phase may also be dispersed throughout the weathering mantle and/or accumulated in the lower parts of profiles according to a translocation mechanism of residual Pt-rich fine particles driven by percolation of water through the connected pore spaces. Keywords: Platinum group minerals, platinum group elements, lateritic weathering, ultramafic rocks, New Caledonia

Published
2008

9. Chemical and physical transfers in an ultramafic rock weathering profile: Part 1. Supergene dissolution of Pt-bearing chromite

Author

Traore, Daouda, Beauvais, Anicet, Chabaux, Francois, Peiffert, Chantal, Parisot, Jean-Claude, Ambrosi, Jean-Paul, and Colin, Fabrice

Subjects
Rocks, Ultrabasic -- Chemical properties, Rocks, Ultrabasic -- Mechanical properties, Chromite -- Properties, Weathering -- Research, Earth sciences
Abstract

Chemical weathering and supergene dissolution processes of Pt-bearing chromite have been studied in a lateritic weathering profile developed on ultramafic rocks in New Caledonia (southwest Pacific). The chemical distributions of alkaline earth, transition metals, and precious metals (including Pt and Pd) were determined in a weathering profile varying from bedrock at the base upward through coarse and fine saprolites, and capped by a mottled zone and a lateritic colluvial nodular horizon. Chemical analyses and mass-balance calculations suggest that progressive weathering of the parent rock is characterized by an enrichment of Fe, Co, and Mn, a segregation of Ni at the boundary between the bedrock and the coarse sapolite and in the lower part of the fine saprolite, and a depletion of Mg, Ca, Si, Al, and Cr. The higher concentration of transition metals at the interface between the coarse and fine saprolite is due to vertical transfer and precipitation at the base of the weathering profile. In such a lateritic environment, the Pt-bearing chromite grains are progressively dissolved and the Pt-group minerals (PGM) are released in the weathering mantle with a preferential depletion of Pd with regard to Pt. Keywords: Lateritic weathering, ultramafic rocks, mass-balance calculation, Pt-chromite, New Caledonia

Published
2008

16. Weathering history and landscape evolution of Western Ghats (India) from 40Ar/39Ar dating of supergene K-Mn oxides

Author

Jean, A., Beauvais, Anicet, Chardon, Dominique, Arnaud, N., Jayananda, M., and Mathe, P.E.

Abstract

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 myrago). 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 and further documentthree major weathering periods,c.53-44,c.39-22 andc.14-10 Ma, the last being documented for the first time in India. These periods coincide with global palaeoclimatic proxies and date the lateritic weathering of three successive palaeolandscapes of the Western Ghats that evolved under slow denudation (c.8mMa-1) over the last 44 myr and were mostly incised during the Neogene (

Published
2020

17. Are channel networks statistically self-similar?

Author

Beauvais, Anicet A. and Montgomery, David R.

Subjects
Channels (Hydraulic engineering) -- Research, River channels -- Research, Earth sciences
Abstract

Scaling properties of both field-mapped and threshold-delineated channel networks were studied by applying the box-counting method to three drainage basins in the western United States. This method involves (1) examination of power-law relations between the box size, [Epsilon], and the number of boxes, N, that intersect channel segments across a range of box sizes appropriate for the method and then (2) examining the standardized residuals for the least squares linear regressions of log N vs. log [Epsilon] used to calculate a fractal dimension (D). For each channel network, the slope of the log N vs. log [Epsilon] relation varies from 1 at small length scales to 2 at large length scales, a range that defines the limits to the applicability of the box-counting method. At length scales below which this slope equals 1, the plots simply record the linear aspect of streams; the length scale defining an upper limit to the application of the box-counting method corresponds to a box size large enough to intersect a channel in each box. Although a fractal dimension may be meaningfully defined only between these upper and lower length scales, neither the field-mapped nor the artificially delineated networks that we examined exhibit discrete fractal dimensions within this range. Instead, the slope of the log-log plot systematically varied with box size. The consistent lack of log-linear plots for the networks that we examined violates a fundamental requirement for fractal geometry and contrasts with general assertions about the fractal nature of river networks. A strong correlation between mean source-area size and the length scale above which the slope of plots implies D = 2 indicates that, although channel networks are not statistically self-similar, they are space filling at length scales greater than twice the mean source-basin length.

Published
1997

20. Lateritic weathering of trachyte, and bauxite formation in West Cameroon : morphological and geochemical evolution

Author

Momo, M. N., Beauvais, Anicet, Tematio, P., Ambrosi, J. P., Yemefack, M., Yerima, B. P. K., and Yongue-Fouateu, R.

Subjects
Lateritic weathering, Bauxite, Gibbsite, Neogene, Cameroon, Rare earth elements
Abstract

Bauxites and Fe laterites were formed on Neogene volcanics from Fongo-Tongo region in the highlands of western Cameroon, and are distributed on plateaus, slopes and downslope surfaces. Bauxitic profiles result from intense in-situ weathering of trachytes that implied depletion of silica and labile elements from the saprolite, while alumina relatively accumulated from parent minerals pseudomorphosis by primary gibbsite formation. During ongoing lateritization and bauxite maturation, important leaching and illuviation processes resulted in secondary gibbsite crystallizations. Late incision and dissection of upper bauxitic plateau resulted in degradation and dismantling of bauxitic duricrusts with Fe-depletion and increasing silica. Compared to trachyte, bauxitic duricrusts are relatively enriched in Nb, Zr, Ga, Ni, Cu, Co, V, Cr, As, Pb, Th, Hf, U and Ta, while Y, Sr, Rb, Ba and Zn are depleted. Trace elements contents depend on relative proportions of gibbsite, kaolinite, iron oxides and anatase and their affinity with these minerals across the weathering sequence. The overall REE composition and C1-Chondrite normalized REE patterns highlight significant fractionations with enrichment in the upslope profile and labile behavior in other profiles of the sequence. REE behavior and Eu/Ce anomalies are controlled by intensity of weathering and lateritic processes during the evolution of profiles. Our results document two major bauxitic phases in the Fongo-Tongo area, i.e., mid-Miocene primary in situ bauxitic weathering of trachyte and late Miocene secondary bauxitization of previously formed bauxitic profiles that led to alumina enrichment up to 53.50 wt%. Combined together, the morphological distribution and geochemical composition of the studied bauxitic profiles constitute guides for bauxite exploration, and more generally document the dynamics and morphogenetic evolution of lateritic landforms in West Cameroon.

Published
2019

21. Lateritic landsurface-regolith differentiation on Pan-African granitic basement of Adamaoua highland, Cameroon.

Author

Nouazi Momo, Mathieu, Beauvais, Anicet, Ntchantcho, Romaric, and Tematio, Paul

Subjects
*RARE earth metals, *REGOLITH, *BASEMENTS, *UPLANDS, *GEOCHEMISTRY, *EROSION
Abstract

• Epirogeny maintained per-humid climate for laterization on Adamaoua, West Africa. • Three stepped lateritic landsurfaces differentiated on granitoids of Adamaoua. • Eocene and Mid-Miocene volcanisms bound periods of lateritic surfaces formation. • Lateritic remains from etch-plain type Paleosurface in landsurfaces regolith. • Pediplain formed downslope the first two etch-plain type landsurfaces. The aim of this paper is to describe and discuss the laterization pattern and the structuration mode of land-surfaces formed over the Pan-African granitic basement of Adamaoua highland. Paleocene to mid-Eocene epeirogeny compartmentalized the regional topography of Adamaoua on which lateritic landsurfaces have been formed over granitoids of comparable geochemistry. Regional scale geomorphological observations and petro-geochemical characterization of lateritic duricrusted regolith allow to distinguish three distinct lateritic landsurfaces, which are compared to lateritic surfaces from West Africa. Regolith of the upper and middle landsurfaces incorporate composite lateritic duricrusts including old bauxites and ferricretes, which are petrological heritages from former regolith of etch-plain type Paleogene African Surface. On Pan-African granitic basement of Adamaoua, the upper and middle landsurfaces formed on granitoids before mid-Miocene basaltic-andesitic outpourings that locally cover them, while the lower landsurface also formed on grantic rocks has been mostly shaped over late Neogene. The geochemical compositions of lateritic duricrusts of upper and middle landsurfaces are clearly distributed between aluminous, ferruginous and kaolinite poles that typifies lateritic regolith of the bauxitic and (Fe-rich) intermediate etch-plains surfaces similarly as lateritic regolith of the Paleogene West-African sequence. Geochemical compositions of lateritic regolith on lower landsurface are mostly distributed between silica, kaolinite and iron, suggesting that more or less evolved or duricrusted horizons have been exposed by differential erosion of this landsurface. Lateritic regoliths of the three landsurfaces are also typified and differentiated by their index of laterization (IOL) and fractionation patterns of some trace (Cr, V, Zr, Ti, Nb, Th, Y, Ta, Ga) and rare earth elements (HREE, Eu/Eu*, (Gd/Yb) N). Though Neogene volcanic epirogenic uplift effects on landscape cannot be totally excluded, erosion and down-wasting of Paleogene landscape mostly evolved to a degraded lateritic etch-plain and late formation of a lower pediplain on Pan-African basement of Adamaoua highland under long-lasting per-humid climatic conditions over Cenozoic. [ABSTRACT FROM AUTHOR]

Published
2024
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23. Morphotectonic of Regolith Landsurfaces in Cameroon (Central Africa): Weighting the Evidences of Late Cretaceous Uplift and Climatic Deep Weathering and Stripping

Author

Nouazi Momo, Mathieu, Beauvais, Anicet, Tematio, Paul, Université de Dschang, 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), Institut de Recherche pour le Développement (IRD), Centre National de la Recherche Scientifique (CNRS), Aix Marseille Université (AMU), and IAG

Subjects
climate variability, epeirogeny, gravitational collapses, regolith landsurfaces, Cameroon, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment
Abstract

International audience; In the last few decades, a range of regolith-related issues highlighted their usefulness on assessing landform dynamics for better understanding and quantifying earth surface processes. A model for the evolution of weathered landsurfaces in Cameroon is developed using available data on their morphology and petrogeochemical patterns, tectonic evidences, geophysical anomalies and sedimentological data. On deformed orogens, the model demonstrates the pivotal role of uplift, consequent volcanic cover and rheology-dependent gravitational collapses in inducing large scale compartmentalization. In areas of tectonic quiescence, it enhances a well known predominance of deep weathering and striping resulting in morphogenetic sequences similar to that of climate-dependent dynamics on the West African craton. These schemes in accordance with regional correlations allow assuming four regolith landsurfaces recognizable with their actual relicts and their specific petrogeochemical patterns. These are the high glacis, the widespread Intermediate ferricrete, the African bauxitic surface, and the modern bauxites developed on Neogene volcanics across the so-called Cameroon Volcanic Line. These findings provide a unique geomorphic record resulting in interplay between late Cretaceous epeirogeny, heterogeneity of uplifted basement, and climate variability. It stands as an input in understanding the dynamics of the complex geomorphic system of the African tropical belt, and specifically in Central Africa where no tectonic input were considered in old issues. It is also a basis for assessing denudation rates and their comparison with weathering-limited steady cratonic denudation of West Africa, and to investigate Cenozoic drainage rearrangement and stabilization as a consequence of uplift.

Published
2017

27. Reconstruction of Post-Deccan topographies from mapping of relict lateritic paleosurfaces: Implications for long-term denudation of Peninsular India

Author

Jean, Amandine, Beauvais, Anicet, Chardon, Dominique, Bonnet, Nicolas, Jayananda, Mudlappa, Janwari, Shazia, Mathe, P.-E., Aix Marseille Université (AMU), Institut de Recherche pour le Développement (IRD), Centre National de la Recherche Scientifique (CNRS), 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), 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 de Rennes (UR), Géosciences Rennes (GR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), University of Hyderabad, and Centre for Earth and Space Sciences [Hyderabad]

Subjects
[SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment
Abstract

International audience; Cenozoic topographic rejuvenation of divergent continental margins and their cratonic hinterland is a matter ofdebate. For instance, continental scale tilt has been advocated as a cause of Late Cenozoic relief growth of theIndian Peninsula. Our work aims at providing independent geomorphological constraints to test such assertions.The western margin of the Peninsula bears theWestern Ghats Escarpment (WGE), which carves both Precambrianrocks and 65 Ma old Deccan Traps. The escarpment separates a narrow coastal lowland plain drained to the ArabianSea from a highland plateau drained towards the Bengal Sea. Alternating and coupled chemical weatheringand erosion led to formation and dissection of lateritic paleolandscapes preserved both sides of the WGE. In thehighland, the relicts of three distinctive lateritic surfaces are recognized. They formed successively from 53Ma to 23 Ma on the basis of ages obtained by Ar-Ar dating of K-rich manganese oxides [1]. The first surfaceis topped by a duricrust rich in Al (bauxite) forming mesas at altitudes of 960 to 1400 m. The second surfacecalled "Intermediate" is mantled by a ferricrete, whose relicts remain 100 m below the bauxite at altitudes of 850 to 1250 m. The third surface corresponds to the relicts of a lateritic pediment, which may be capped by aferricrete at altitudes of 600 to 900 m. Three lateritic surfaces have been documented in the lowland. The Ar-Arages obtained indicate common lateritic weathering in both the highland and the lowland between at 53-45 Ma,then a divergence later on [1]. The oldest remnants of lateritic surface in the lowland are preserved at maximumelevation of 400-500 m close to the WGE and correspond to a pediment. This ancient landform was re-altered at24-19 Ma to form residual hills of the “Intermediate” relief (ca. 350-200 m). A younger pediment formed aroundthe residual hills and is preserved at ca. 150-50 m elevation.Relicts’ elevations of the three surfaces have been retrieved in both the lowland and the highland to reconstructsuccessive topographies across the WGE and estimate relief evolution and erosion budgets for major time steps.The results suggest that the denudation did not exceed 10 m/my in the Highland since 45 Ma, and is less than 11m/my since mitigation of chemical weathering ca. 23 Ma ago. In the lowland, denudation was limited to 5 m/mysince 45 Ma and less than 6 m/my since 19 Ma, implying negligible reworking of the WGE, which stabilizedat least 50 Ma ago [2]. These results have major implications for relief evolution of South India. They implyvery low relief growth since the Eocene and do not require a tilt of the Peninsula. They further put constraints onsedimentary supplies to both margins of the Peninsula over the last 50 Ma.[1] Bonnet et al., 2016, Chemical Geology 446, 33-53.[2] Beauvais et al., 2016, Geology 44, 299-302.

Published
2017
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28. Weathering and denudation history of the western continental margin of India constrained by combined Ar-Ar dating and paleomagnetism

Author

Jean, Amandine, Mathe, P.-E., Beauvais, Anicet, Chardon, Dominique, Demory, François, Janwari, Shazia, 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), Institut de Recherche pour le Développement (IRD), Centre for Earth and Space Sciences [Hyderabad], University of Hyderabad, and Beaussier, Catherine

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

International audience

Published
2017
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29. WEATHERING AND DENUDATION OFTHE WESTERN CONTINENTAL MARGIN OF PENINSULAR INDIA:THE 40Ar/39Ar DATING OF LATERITIC K-RICH MANGANESE OXIDES

Author

Bonnet, Nicolas J., Beauvais, Anicet, Arnaud, Nicolas, Chardon, Dominique, Dupont-Nivet, Guillaume, 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 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), 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), Institute of Earth and Environmental Sciences, Universität Potsdam, Géosciences-Rennes, 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-Centre National d'Études Spatiales [Toulouse] (CNES)-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), 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 national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles (UA), Université de 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 University of Potsdam = Universität Potsdam

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

International audience; The Cenozoic weathering of peninsular India has been advocated as a major driver of globalcooling, however, its timing remains virtually unconstrained such that proposed links betweentropical weathering of the Deccan Traps, regional monsoonal intensity and global climate remainsspeculative. To solve this conundrum we present here a revised weathering chronologybased on the identification of lateritic paleosurfaces and their dating using 40Ar/39Ar on supergeneK-rich manganese oxides. We focus on the Indian western passive margin where theWestern Ghats Escarpment (WGE) – a ~1000 m high topographic barrier resulting from thecontinental break up of Greater India – exposes exceptionally preserved weathering profilesfrom the western coastal lowlands to the eastern highland plateaus above the WGE. Four mainlateritic paleosurfaces have been identified: Three in the highland; a high landsurface (Al-Femostly bauxite) at elevation 1200-1000 m asl, an intermediate landsurface covered by a Feduricrustat 1000-900 m asl and a lower pediment landsurface at 850-600 m asl; and one inthe coastal lowland underneath a pediment landsurface at 150-50 m asl. The 40Ar/39Ar agesdocument 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 correlatesto the Global Eocene climatic Optimum, and allows defining a bauxitic paleolandsurface acrossthe escarpment. Intense bauxitic weathering between ~ 45 and 47 Ma in the lowland indicatethat the WGE was stabilized before ~ 47 Ma on its margin and also implies low denudation rateat the foot of the WGE (

Published
2016

30. 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

31. Regolith and landscape evolution in Peninsular India and West Africa: Morphoclimatic evolution of the two continents over the Cenozoic

Author

BEAUVAIS, Anicet, Chardon, D, Jean, A, Jayananda, Mudlappa, Shazia, Janwary, Bonnet, Nicolas, 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), 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 for Earth and Space Sciences [Hyderabad], University of Hyderabad, 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-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), 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), 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
[SDU.STU]Sciences of the Universe [physics]/Earth Sciences
Abstract

International audience; Shields’ surfaces of the tropical belt have been continuously shaped over the Cenozoic under thecombined or alternating effects of chemical weathering and mechanical erosion that left steppedrelict lateritic paleolandsurfaces exposing different generations and type of regolith in today’ssceneries. These lateritic paleolandscape remnants are well preserved in West Africa and in highlandPeninsular India, particularly on Deccan Traps. The stepped character of such paleolandscaperemnants allows to describing a common geomorphic sequence of three successive sub-continentalscale lateritic paleolandsurfaces on the two sub regions. The first surface is defined by the oldestremnants, which are generally topped by Al-Fe (mostly bauxitic) lateritic duricrusts upon distant kmscalemesas or as larger provinces on high relictual topographic massifs (e.g., Fouta Djalon in WestAfrica or Nilgiri hills in South India). The relict bauxitic landforms generally dominate from less thanca. 300 m the relicts of a second geomorphic level (so-called “intermediate” surface), which ismantled by ferruginous lateritic duricrusts. The third and last paleolandsurface remnants lie less thanca. 400 m below the bauxitic landforms, and consist in a weathered lateritic pediment that is locallycapped by a ferricrete.The ages of these continental-scale lateritic paleolandsurfaces may be bracketed using 40Ar/39Ardating of K-Mn oxides (cryptomelane) formed in their underlying weathering profiles in the Africanand Indian contexts [1,2,3]. The first surface is Eocene and correlates with the Eocene climaticoptimum (ca. 50 Ma) that is recorded throughout the tropical belt by the production of bauxite. InSouth India, the Intermediate surface has evolved by dominant chemical weathering since the LateEocene (ca. 37 Ma) and records peak weathering activity in the Late Oligocene. In West Africa, thatpaleolandsurface seems to have only record the late Oligocene interval (ca. 29-24 Ma) of intenseweathering. Abandonment of the Intermediate landscape as a result of its dissection by the rivernetwork took place in the Latest Oligocene on both continents. By contrast, the later pedimentseems to have been shaped quite rapidly (ca. 32-29 Ma) and was weathered around the Oligocene-Miocene boundary (ca. 29-24 Ma) in India, whereas it took longer to form (ca. 24-18 Ma) and wasweathered mostly during the Mid-Miocene (ca. 18-11 Ma) in West Africa. The contrasts in themorphoclimatic record of the two sub regions are linked to the spatial diversification of climaticregimes after the Eocene climatic optimum. However, the combination of the ages with the elevationdifferences between each lateritic paleolandsurface documents denudation rates with comparableand very low amplitudes (5-15 m/m.y.) in these two continents over the last 50 Ma.[1] Beauvais A and Chardon D (2013) Geochem Geophys Geosyst 14:1590-1608, doi:10.1002/ggge.20093.[2] Bonnet NJ et al. (2014) Earth Planet Sci Lett 386:126-137, doi:10.1016/j.epsl.2013.11.002[3] Bonnet NJ et al. (2016) Chem Geol, in press.

Published
2016

32. Tempo of lateritic weathering and erosion of Peninsular India over the Cenozoic: Morphoclimatic implications

Author

Bonnet, Nicolas, Beauvais, Anicet, Chardon, D, Arnaud, N, 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), 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 Montpellier (UM), 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), 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), 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
[SDU.STU]Sciences of the Universe [physics]/Earth Sciences
Abstract

International audience; Most shields of the tropical belt show extended lateritic landform relicts, which result fromconjugated chemical weathering and mechanical erosion processes over the Cenozoic. After DeccanTraps extrusion ca. 65 m.y. ago, Peninsular India has been shaped by successive periods of lateriticweathering and erosion on both sides of the Western Ghats escarpment (WGE), which separates acoastal lowland from a highland plateau. The weathering periods are documented from 40Ar/39Ardating of K-Mn oxides (cryptomelane, Kx Mn8-xIV MnxIII O16, nH2O) formed in Mn ore deposits and Fe-Mn lateritic weathering profiles, which are developed from Archean supracrustal rocks and exposedon stepped remnants of paleolandsurfaces on either side of the escarpment. The 40Ar/39Ar agesobtained document three major weathering periods [1], ca. 53-45 Ma both in the highland and thelowland, ca. 37-24 Ma only in the highland [2], and ca. 24-19 Ma only in the lowland [3]. These ages’series document evolving geomorphic and climatic patterns on either side of the WGE over theCenozoic.The intense lateritic weathering at 53-45 Ma and 37-24 Ma reflect the Early Eocene optimum and theonset of Asian monsoon regimes, when the peninsula drifted across the equatorial belt. Synchronousearly Eocene weathering on both sides of the WGE and the preservation of laterites as old as 47 Maon its piedmont attests to the stabilization of this marginal escarpment before that time, and furtherdocuments a slow denudation of the lowland since then [3]. The ages series also indicate that thehighland landsurfaces were mostly dissected after ca. 24 Ma, while little incision affected thelowland after ca. 19 Ma. Finally, the 40Ar/39Ar ages document a divergent erosion and weatheringhistory on either side of the escarpment suggesting a dual climatic regime across this topographicbarrier after the Eocene climatic optimum.[1] Bonnet NJ et al. (2016) Chem Geol, in press.[2] Bonnet NJ et al. (2014) Earth Planet Sci Lett 386:126-137, doi:10.1016/j.epsl.2013.11.002[3] Beauvais A et al. (2016) Geology, in press, doi:10.1130/G37303.1

Published
2016

33. Regolith in the sediment routing system: a view from tropical shields

Author

Chardon, D, Rouby, D, Grimaud, J, Huyghe, D, Beauvais, Anicet, Bamba, O, 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 National de la Recherche Scientifique (CNRS), GET (GET), Ecole Nationale Supérieure des Télécommunications de Bretagne, 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), Institut de Recherche pour le Développement (IRD), Aix Marseille Université (AMU), and Université Joseph Ki-Zerbo [Ouagadougou] (UJZK)

Subjects
[SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment
Abstract

International audience; Production and remobilization of regolith are key processes controlling the availability of clastic sediments and solutes for river systems. Over the shields of the tropical belts, thick lateritic regolith mantles were repeatedly produced by weathering and remobilized by mechanical erosion during the Cenozoic (e.g., Figure 1). Shields represent continental surfaces of very large areal extent (ca. 60 % of the emerged lands) and have been influenced by repeated widening of the inter-tropical climatic zone during the Cenozoic. In this contribution, we show how integrated quantitative investigation of landform-regolith evolution processes, from the landscape scale to that of tropical shields, contributes to the understanding of the long-term (1-100 My) dynamics of non-orogenic surfaces and their clastic delivery to the world ocean. Such an approach allows (1) reconstructing landforms, regional topography, drainage networks and catchments through time, (2) quantifying the evolving continental denudation and clastic sedimentary yields of shields, (3) estimating the mineralogical and granulometric nature of such yields to be delivered to continental margins’ basins and (4) evaluating the links between drainage evolution and sedimentary yields. Such outcomes are based on the study of the West African sub region, which hosts a dense distribution of dated and regionally correlated regolith-landform markers. Methodology involved (1) regolith-landform mapping on a local (1-10 km) and regional (100-1000 km) scale, (2) geomodeling assisted construction of paleolandscapes and regional paleotopographies and (3) compilation of petrological and physical characteristics of regolith.Results from West Africa open new perspectives on intercontinental regolith correlations as well as on the evaluation the global causes and consequences of tropical shields’ regolith production, stripping and exports over Cenozoic timescales.

Published
2016

34. Stabilization of large drainage basins over geological timescales : Cenozoic West Africa, hot spot swell growth and the Niger River

Author

Chardon, Dominique, Grimaud, Jean-Louis, Rouby, Delphine, BEAUVAIS, Anicet, Christophoul, Frédéric, 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 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), Aix Marseille Université (AMU), Institut de Recherche pour le Développement (IRD), Centre National de la Recherche Scientifique (CNRS), WAXI, CNRS, IRD, ANR-08-BLAN-0247,TOPOAFRICA,Evolution of the African topography over the last 250 My from the sedimentary record to mantle dynamics(2008), 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), 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 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 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
[SDU.STU]Sciences of the Universe [physics]/Earth Sciences
Abstract

International audience; 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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35. Very long-term stability of passive margin escarpment constrained by 40Ar/39Ar dating of K-Mn oxides

Author

Beauvais, Anicet, Bonnet, N.J., Chardon, Dominique, Arnaud, N., and Jayananda, M.

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

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

Author

Bonnet, N.J., Beauvais, Anicet, Arnaud, N., Chardon, Dominique, and Jayananda, M.

Abstract

Since Deccan Traps extrusion ~ 65 Ma ago, thick weathering mantles have developed over Peninsular India on both the western coastal lowland and adjacent eastern 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

37. Nickal : typologie des minerais latéritiques de Nouvelle-Calédonie et facteurs de concentrations de cobalt et nickel (rapport scientifique)

Author

Bailly, Laurent, Ambrosl, J.P, Barbarand, J., BEAUVAIS, Anicet, Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Géosciences Paris Sud (GEOPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), 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 [Nouvelle-Calédonie]), CNRT 'Nickel et son environnement', 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
Latérite jaune, Datations U-Th/He, Isotopes Stables, Extraction, K/Ar, Cobalt, Nouvelle-Calédonie, Typologie, Paléomagnétisme, Datations, Nickel, Datations Ar/Ar, Sélective, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, [SDU.STU.AG]Sciences of the Universe [physics]/Earth Sciences/Applied geology
Abstract

Le projet Nickal, d’une durée initiale de 3 ans (36 mois), répond à l’appel à projet du CNRTnickel et son environnement intitulé « Facteurs de minéralisation des latérites » sur le volet« Typologie des minéralisations liées à l’altération des péridotites en Nouvelle-Calédonie etconcentrations du cobalt dans les latérites ». Ce projet multidisciplinaire implique le BRGM,l’IRD (CEREGE), le CSIRO, les universités de Paris Sud, de Rennes 1, de Namur et deNouvelle-Calédonie, la DIMENC et plus particulièrement le SGNC.Ce projet s’intéresse aux facteurs et mécanismes d’enrichissement en nickel et cobalt dans lesminerais latéritiques (saprolite fine ou latérite jaune) développés ou non au-dessus des mineraissilicatés (saprolite grossière). Il s’articule autour de neuf tâches.

Published
2016

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

Author

Chardon, Dominique, Grimaud, J.L., Rouby, D, Beauvais, Anicet, and Christophoul, F.

Abstract

Reconstructing the evolving geometry of large river catchments over geological time scales 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 is 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 stratigraphic turnover along the Equatorial margin of West Africa.

Published
2016

40. Formation de corrugations hydrothermales lors de l'altération des roches ultramafiques

Author

Guillou-Frottier, Laurent, Beauvais, Anicet, Wyns, Robert, Bailly, Laurent, Augé, Thierry, Audion, Anne-Sophie, 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), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), 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), Vingtièmes journées techniques du Comité Français d’Hydrogéologie de l’Association Internationale des Hydrogéologues, 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), 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), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (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), 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 Guillou-Frottier, Laurent

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

International audience; During shallow subsurface (< 200 m depth) weathering processes, temperatures may reach several tens of °C as a result of exothermic chemical reactions, such as hydration of olivine in ultramafic rocks or chloritization of biotite in granitic rocks. These mineralogical transformations enhance mineral fracturing, and the growth of fracture networks leads to further reactions and increases the permeability. The subsequent deepening of the weathering front creates new reactions, thus self-maintaining the weathering process over several million years (Myr). For more than 20 Myr, the peridotite massifs of New Caledonia have undergone intense weathering that has produced thick lateritic weathering mantles. The observable undulations of the weathering front and the protrusions of unweathered peridotite, from several meters to several tens of meters high, attest to a corrugated bedrock topography, which may result from inhomogeneous fluid circulation patterns within the coarse, permeable and porous (30-50%) saprolite layer. Combined together, the excess heat (up to ≈ 100°C) and high permeability (10-14 to 2  10-13 m²) within lateritic weathering mantles could potentially trigger hydrothermal convection (buoyancy-driven flow). This was numerically modeled by accounting for temperature-dependent fluid density and viscosity, and for time-dependent and spatially varying parameters simulating the deepening of the weathering front. Modeling the transient evolution of the thermal and flow velocity fields over 10 Myr reveals that hydrothermal convection can be triggered in the weathering lateritic mantles of New Caledonia, even on sloped surfaces where topography-driven flow prevails. Convective cells develop above the weathering front, and the amplitudes of thermal undulations are enhanced when feedback mechanisms between permeability and temperature are accounted for. The models also allow definition of the most probable zones of mineralization and reveal two-dimensional corrugations below which weathering is no longer efficient.

Published
2015

45. Aquifères de socle : le point sur les concepts et les applications opérationnelles

Author

Guillou-Frottier, L., Beauvais, Anicet, Wyns, R., Bailly, L., Augé, T., and Audion, A.S.

Subjects
MODELE MATHEMATIQUE, POROSITE, CHIMIE DE L'EAU, HYDROTHERMALISME, FRACTURE, PERMEABILITE, ECOULEMENT SOUTERRAIN, ROCHE MAGMATIQUE, CONVECTION, EVALUATION, HYDROGEOLOGIE, CORRUGATION, AQUIFERE, ALTERATION CHIMIQUE, ROCHE ULTRABASIQUE, FLUX THERMIQUE
Published
2015

47. Nickal - Typologie des minerais latéritiques de Nouvelle-Calédonie et facteurs de concentration de Co et Ni. Rapport scientifique final. Les gisements de nickel latéritique de Nouvelle-Calédonie, volume II

Author

Bailly, Laurent, Ambrosi, Jean-Paul, Barbarand, Jocelyn, Beauvais, Anicet, Cluzel, Dominique, Lerouge, Catherine, Prognon, François, Quesnel, Florence, Ramanaïdou, Erick, Ricordel-Prognon, Caroline, Ruffet, Gilles, Sevin, Brice, Wells, M., Yans, J., Alizert, Lilian, Audion, Anne-Sophie, Gautheron, C., Winninger, Jean-Edouard, Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Centre National de la Recherche Scientifique (CNRS), 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), 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), Aix Marseille Université (AMU), Université de la Nouvelle-Calédonie (UNC), Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), Université de Rennes (UR), Gouvernement de la Nouvelle-Calédonie, DIMENC/SGNC (SGNC), CNRT Nickel et son environnement, Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Collège de France (CdF (institution))-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA), and Université de Rennes (UNIV-RENNES)

Subjects
Datation Ar/Ar, NICKEL, Latérite jaune, Isotope stable, Extraction sélective, Cobalt, Nouvelle-Calédonie, Typologie, EXPLOITATION DU SOUS SOL, DATATION, Paléomagnétisme, Datation K/Ar, Nickel, PALEOMAGNETISME, TYPOLOGIE, ISOTOPE, COBALT, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, Datation, Datation U-Th/He, [SDU.STU.AG]Sciences of the Universe [physics]/Earth Sciences/Applied geology, LATERITE
Published
2014

48. Nickal - Typologie des latérites de Nouvelle-Calédonie. Gisements de nickel latéritique, volume II

Author

Bailly, Laurent, Ambrosi, Jean Paul, Barbarand, Jocelyn, BEAUVAIS, Anicet, Cluzel, Dominique, Lerouge, Catherine, Prognon, François, QUESNEL, Yoann, Ramanaïdou, Erick, Ricordel-Prognon, Caroline, Ruffet, Gilles, Sevin, Brice, Wells, M., Yans, J., Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), 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 de la Nouvelle Calédonie (UNC), Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), Université de Rennes (UNIV-RENNES), Centre National de la Recherche Scientifique (CNRS), DIMENC/SGNC (SGNC), and CNRT 'Nickel et son environnement'

Subjects
latérite jaune, nickel, extraction sélective, datation, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, Nouvelle-Calédonie, cobalt, [SDU.STU.AG]Sciences of the Universe [physics]/Earth Sciences/Applied geology, typologie, paléomagnétisme, isotope stable
Published
2014

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