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Les sols humifères des "Hautes Terres" du massif des Nilgiri en Inde du Sud. Formation d'andosols sur une ancienne couverture ferrallitique en relation avec les évolutions climatiques des derniers millénaires

Abstract : High elevation humiferous soils from the Nilgiri Hills may be considered as the result of a polycyclic genesis: the ferrallitic regoliths corresponding to an old pedogenesis under a tropical wet and hot climate ; the present pedogenesis concerning only the surface humiferous horizons. The most humiferous soils are marked by the presence of high amounts of organo-metallic complexes and verify the criteria of identification of Andosols in recent soils classifications and are moreover non-allophanic. The Nilgiri Andosols developed on an ancient ferrallitic material present and original pedogenesis. In the absence of volcanic glasses and any other weatherable minerals the potential sources of aluminium and iron to form the organometallic complexes are the secondary oxides. Gibbsite and iron oxides, considered as stable minerals of ferrallitic weathering, are instable in acidic conditions and in presence of organic matter. Due to high amounts of oxides the organo-metalllic associations are provided with a substantial metallic charge which leads to the emergence of andic properties. [exponent14] C datings and [delta exponent 13]C of soil organic matter revealed that the formation of the organic matter-rich horizons was related to the existence of a cold period at the transition Pleistocene / Holocene with grassland vegetation. The study of these soils gives information on the processes of organic matter accumulation in soils at different periods and show that the characterisation of the organo-metallic complexes at different scales allows to understand the interactions of the organic matter with metallic-cations which is the key process of its stabilisation.
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http://docnum.univ-lorraine.fr/prive/SCD_T_2000_0009_CANER.pdf
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https://hal.univ-lorraine.fr/tel-01746419
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Submitted on : Thursday, March 29, 2018 - 10:37:23 AM
Last modification on : Wednesday, January 6, 2021 - 2:19:08 PM

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Laurent Caner. Les sols humifères des "Hautes Terres" du massif des Nilgiri en Inde du Sud. Formation d'andosols sur une ancienne couverture ferrallitique en relation avec les évolutions climatiques des derniers millénaires. Sciences de la Terre. Université Henri Poincaré - Nancy 1, 2000. Français. ⟨NNT : 2000NAN10009⟩. ⟨tel-01746419⟩

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