Three-dimensional organization of a pedological cover, comprising study of the geometrical relationship between horizons and, in particular, concordance/discordance relationship makes it possible to reproduce certain steps of a landscape development. The studied slope, in the humid tropical zone (Atlantic Brazil), shows a very thick latosolic cover (> 10 m) with subhorizontal horizons upslope. The upper part of this cover is intersected by a thinner pedological differentiation which corresponds to the present day topography. The latter has developed, along the slope, throughout the successive horizons of the thick latosolic cover down to the depth of the substratum. When the substratum is reached, lithodependant soils develop successively on sandstones, siltstones and sandy clays of the Tubarao Formation (Permo-Carboniferous). This discordance between the superficial differentiation and the horizons of the latosolic cover suggests that the former is more recent than the latter. Further downslope a thick cover reappears which may be related to the one found upslope, by means of the study in the horizontal plane. Considering that the geometry of this latosolic cover (limits between horizons and between soil and saprolite) is approximatively parallel to the surface topography which occurred at the time of its formation, we may reconstitute the past topography. The reconstitution seems to show that present topography is partially embedded in the past topography. Key-words : Ferrallitic soils, landscape development, geometrical relationship between horizons, Brazil.
Sommaire.
Les oscillations climatiques quaternaires sont responsables de la formation d'un certain nombre de glacis, emboîtés sur les versants de surfaces préquaternaires. Celles-ci sont souvent recouvertes par des formations superficielles, parfois assez épaisses. La photo-interprétation permet la définition et la cartographie de ces surfaces d'érosion et de certaines formations superficielles. L'étude des sols a montré une corrélation assez étroite entre les types de profil, définis par leur degré d'altération, les surfaces d'érosion et leurs dépôts corrélatifs. Des études et recherches entrepris actuellement permettent une cartographie géologique, géomorphologique et pédologique de détail, ainsi que l'interprétation des processus responsables de l'évolution du paysage.
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