This paper deals with the genesis of hydromorphic sandy soils with spodosol morphology found in extensive flat surfaces, in which isolated zones with undulating relief emerge, containing well drained oxisols. The objective of this study was to explain the existence of pedogenetic relationship in an oxisol-spodosol system, and to verify the possible development of the sandy materials as a consequence of oxisol transformation. For this purpose, we characterized the morphology of the soils and their physical, chemical and mineralogical attributes. The studied soils showed autochthonous development and filiation to granitic rock of the crystalline basement, displaying lateral genetic relationship between them. Thus, we can admit the occurrence of oxisol transformation, verified in a metric scale, caused by increasing waterlogging conditions. As a result, soil yellowing was found, followed by gleization near the edge of the hill. In this zone, clay depletion was evidenced in the subsuperficial soil layer, extending laterally towards the plain, with the appearance of sandy materials (white sands) near the hill, followed by hydromorphic spodosol. This disposition suggests that evolution of the spodosol occurred after sand formation occurred later. The main pedogeochemical process involved in clay removal would be acidolysis, which causes gibbsite and kaolinite dissolution. Thus, soil transformation would probably have played a preponderant role in the landscape evolution resulting in overall relief planation.
hydromorphic soils; morphogenesis; podzolization; spodosol; tropical soil