This study defines some aspects of superficial alteration processes and their reflexes on the Quaternary pedogeomorphology in the sub-basin of the upper Maracujá River, in the Complexo Bação, ferriferous zone, State of Minas Gerais, Brazil. Characteristics related to the dynamic evolution of three gneiss-underlayered toposequences (1, 2, and 3) at different erosion stages were investigated. In the top slope segments of the toposequences 1 and 2 the soil profiles are little developed and present an in situ evolution. In toposequence 3, the soil profile of the same top slope segment is a well developed Oxisol with allochthonous features. Similarly, in the mid slope segments of the three toposequences, the soil profiles are thick, Latosolic, originated from the colluvial sediments that descended from the top slope. However, there is a rupture in the sediment transport and deposition process in the low slope segments. The soil profile of toposequence 2 is an autochthonous Cambic Oxisol, while the toposequences 1 and 3 profiles were developed from alluvial - colluvial materials deposited on the gneiss saprolite basement. Despite the fact that dynamic evolution of the top and mid slope segments of the three toposequences corroborate the tropical geomorphological models up to the mid slope segment, the rupture in colluvial deposition to the lower slope segments suggests a recent morphodynamic imbalance. Besides, the micromorphological and mineralogical features do not present any correlation with the differentiated erosive susceptibility verified in the area.
weathering; micromorphology; gneiss soils
