Uso de atributos pedológicos na compreensão da gênese de superfícies geomorfológicas escalonadas da borda oeste do planalto do Espinhaço Meridional / Minas Gerais - Brasil

Abstract

Field investigations carried out on a stretch of the western border of the Southern Espinhaço Plateau proved that its relief is organized in stairways, whose levels modeled in siliciclastic rocks, confi gure distinct geomorphological units. This organization raised questions about the degree of weathering of the soils that cover these geomorphological units, as well as the possible relationship between this degree and the genesis and dynamics of the relief. In order to answer these questions, twenty-nine soil samples were collected in three profi les in Geomorphological Unit I, whose approximate altitude is 1400m, and four samples in Unit IV, positioned at an average altitude of 1250m. The collections took place in similar lithologies in both units in order to make the comparative analysis between the results of the soil samples of the soil samples feasible. In such samples, granulometry, mineralogical, pH, fertility, sulfuric attack, free iron extraction and forms of low crystallinity of irom were analyzed.In addition, this study used methods of analyzing micromorphology and obtaining images in a petrographic microscope and SEM, used in the investigation of the structure of the aggregates and the organization of the pores of soil layers of the diagnostic horizons of three soils of Unit I and six of Unit IV. The results of the silt / clay, Ki and Fed / Fes relationships indicate that the soils developed in Unit I register a greater degree of weathering and, consequently, signals its more advanced stage when compared to those present in Unit IV. Through micromorphological analysis it was observed that the organization and formation of porosity and the development of the plasma structure of the soils of Unit I, especially the horizons 2C2 of P1 and C5 of P2, suggest that these are more evolved when compared to the soils of Unit IV. These results reinforce the hypothesis that there is a morphogenetic relationship between these geomorphological units, so that the surface positioned at a lower altimetry originated from the denudational dismantling of the summit surface under strong conditioning of the regional geological structure.