Análise de coberturas superficiais e sua correlação com a geodinâmica na bacia do Ribeirão Chiqueiro - Serra do Espinhaço Meridional MG

Abstract

The regolith constitutes in geomorphology a key to the interpretation of the landscape because it contains information about the processes that were once involved in the dynamics of the relief evolution. On the basis of this principle this research has the objective to identify at least part of the Chiqueiro creek slope dynamics. The Chiqueiro is affluent of the Paraúna River which forms the main drainage system in the Municipality of Gouveia, located at the Espinhaço Meridional mountain range, in Minas Gerais State, Brazil. It takes into account the relation between fluvial energy, slope processes and regolith characteristics. Initially, the Hack Index values were extracted to identify differences in energy distribution along the subbasins. Together with the analysis of the main rivers longitudinal profiles they were used to establish associations between the Hack Index and the morphological characteristics of the water courses in order to identify seven sampling slopes. In each of them geomorphological sites were identified in the middle of which soil profiles were opened, observed, described, and samples collected for the following laboratory analyses of particle size and simple fertility. Pedo-geomorphological index was applied to the following laboratory results: sand/gravel relation, uniformity value, silt/clay relationship, pH delta and CTC helping to verify the degree of change and evolution of the regolith. Most of the basin shows low values of the Hack Index. The higher values are associated with lithologiccharacteristics of the area mainly at the edges of the Gouveia Depression, a zone of lithological contact formed predominantly by quartzite. Longitudinal profiles analysis allowed assuming that the majority of the river course is in dynamic-equilibrium state, given that no significant break of slope occurs along the entire river profile. Results seem to indicate that the basin area is not affected by significantly enough uplift or subsidence rates to create knick points. The analysis of the regolith shows the presence of very weathered material, indicating a high level of evolution, suggesting that the older material is located in the upper slopes, while younger material is located in the lower portions. In the creek drainage basin of the Chiqueiro stream the lithological factors were the main benchmarks associated with the variation of the Hack index values being primarily responsible for morphological abnormalities of the longitudinal profiles.