CHARACTERISTICS OF CLAYS IN AN OXISOL-- SPODOSOL TOPOSEQUENCE IN AMAZONIA (BRAZIL)

摘要: The clay fraction of soils from a toposequence developed on sandy Tertiary sediment in the Brazilian Amazonia was studied. Clayey Acrorthox located at upper part sequence have transformed progressively into Tropohumods down slope. Along slope important chemical and mineralogical changes linked to modifications weathering conditions were observed. In hydrolysis process largely prevails is composed mainly Fe-rich kaolinite. Fe AI amorphous compounds become increasingly abundant along Spodosols, acidocomplexo- lysis processes both been effective, fractions contain not only more gibbsite, but also materials which are particularly Bh horizons. area near Manaus (Brazil), (sols ferrallitiques), Paleudult ferrallitiques A diff6renciation texturale) Tropohumod (podzols) associated soil toposequences. According Klinge (1965), podzols covering valley bottoms, clayey has settled plateau surfaces. Chauvel et al. (1987) Lucas demonstrated that whole derived same parent material, known as Barreiras sediment. From lower sequence, through destruction clays leaving quartzose residual material. (kaolinite gibbsite) weathered by acido- complexolysis (podzolization) involves complexing organic acids removal A1 profile. However, considered previous impoverishment ferrallitic material necessary before podzolization. purpose this paper geochemical characterization (< 2/zm) order obtain information about conditions, respective roles podzolization development toposequence.