Gênese de depressões fechadas em vertentes associadas à couraça aluminosa na porção sul da Serra do Caparaó, Minas Gerais/Espirito Santo

Abstract

The origin of the closed depressions associated with the aluminous duricrust occurring on the tops of the hills and along the hillslope in the region of Espera Feliz city, Minas Gerais state, bordering the Espírito Santo state, was investigated through a geophysical survey of soil cover associated with the morphological analysis (macro and micro) in soil profi les. Geophysical survey by GPR held in two sections along a slope, covered two consecutive depressions and was followed by systematic survey of soil cover through the opening 5 profi les (N1, L1, L2, N2 and L3), where deformed samples were collected for chemical, physical and mineralogical analysis and undisturbed samples for micromorphological analysis. Humic Neosols were found inside the closed depressions and Humic Ferralsols were found between the closed depressions. The side analysis performed by GPR and the joint interpretation of the soil properties reveals a persistent pedological system from top to bottom of the slope. So the morphological diff erences that would lead to consider two soil classes are related to the occurency of mass moviments. The origin of the horizon (Bw and A) are related to the vertical advance of bauxite degradation conducted by bioturbation. The aluminous duricrust and its transformation into soil are understood as preceding stages of erosive features formation. Thus, the bauxite in the region would have formed under hot and humid weather conditions and removing parts of the cover in later dry weather conditions.