Reatto Braga A. auteur aut IRD Bruand A. auteur aut IRD De Souza Martins E. auteur aut IRD Muller F. auteur aut IRD Medrado da Silva E. auteur aut IRD Abilio de Carvalho O. auteur aut IRD Brossard Michel auteur aut IRD Richard G. auteur aut IRD text journalArticle eng text/pdf born digital access Brazilian Latosols are characterized by low activity clay, little horizon differentiation, a weak macrostructure and a strong microgranular structure. The development of the latter that was reported as being possibly related to the. ne material mineralogy, location in the landscape, parental material and biological activity is still under discussion. The aim of this study is to discuss the origin of the microgranular structure of Latosols located in the Brazilian Central Plateau. Ten Latosols (L) developed in different parent materials were selected along an approximately 350-km long regional toposequence across the South American Surface (SAS) (L1 to L4) and Velhas Surface (VS) (L5 to L10). The structure of the Latosols was studied in the field and samples of the diagnostic Bw horizons were collected for laboratory analyses. Basic soil characterization was performed on the <2-mm material according to the Brazilian standard procedures. The SiO2, AL(2)O(3), Fe2O3 and TiO2 content was determined after dissolution with 1:1 H2SO4. The microstructure was studied in optical microscopy and scanning electron microscopy in thin sections. The results showed a varying compound strong microgranular structure and weak to moderate medium sub-angular blocky structure independently of the landscape position as well as the parental material, except for the Latosol developed on a quartzite. The Latosols were classified as gibbsitic-sesquioxidic, kaolinitic non-sesquioxid, or kaolinitic-sesquioxid Latosols but there was no relationship between their composition and the development of the microgranular structure in the Bw horizon. The analyses showed indeed several types of microgranular structure with different proportions but without any relationship with their texture and mineralogy. Actually, the types of microgranular structure appeared to be mainly related to soil bioturbation by termites and eventually secondarily by ants. Thus, the weak macrostructure and strong microgranular structure of the Latosols studied, the little vertical differentiation of the horizons, and the lack of a clear relationship between their landscape position and parent material characteristics would result from long-term biotic action with high probability. specialized STRUCTURE DU SOL MICROSTRUCTURE ANALYSE MINERALOGIQUE ANALYSE PHYSICOCHIMIQUE ARGILE KAOLINITE GIBBSITE FAUNE DU SOL TERMITE BRESIL 068PROSOL 76 2 122-134 2009 0341-8162 https://www.documentation.ird.fr/hor/fdi:010045564 10.1016/j.catena.2008.10.003 0341-8162 [F B010045564] https://www.documentation.ird.fr/hor/fdi:010045564 https://www.documentation.ird.fr/intranet/publi/depot/2009-03-25/010045564.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2009-03-23 2010-01-07 fdi:010045564 fre