Interação nível de base e dissecação de bacias hidrográficas no sudeste de Minas Gerais - Brasil

Abstract

The hydrographic basins of the eastern portion of the Brazilian territory present a remarkable dimensional scalar discrepancy.Those basins located in the interior of the continent have large extensions, unlike those that occupy coastal position that have smaller area drained.These distinct sets of basins are separated by a Great Escarpment, inheritance of tectonic and denudational processes that occurred during the opening of the South Atlantic in the Mesocenozoic. In the southeast of the state of Minas Gerais this escarpment separates hydrographic basins that are adjusted and organized, in plan and profile, to stepped steps clearly recognized and mapped here using geotechnologies. The current geomorphodynamics in these steps responds to the different levels of base to which its hydrographic basins are articulated. The analyzes elaborated in this work are based on mappings that aim to express the close relationship between the regional dimension of relief and the organization of the drainage network. It is demonstrated here that, in addition to the fact that different levels of base strongly influence continental denudation in the southeast of Minas Gerais, the Great Escarpment forms a prominent and important frontier that separates two geomorphological domains in which there are discrepant conditions regarding the behavior in space and time incision of the regional hydrographic network. The river channels that integrate the inner basins reveal significantly lower altimetric slopes than those of the rivers that go directly to the ocean. In those coastal basins, the relief dissection is spatially organized according to staggered steps of subregional extension, which are absent in the interior basins.