Influência de níveis de base nas características morfossedimentares das bacias dos rios das Velhas e Jequitaí (MG)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2010

RESUMO

The Velhas and Jequitaí river basins have together an asymmetric shape that drain northward from Quadrilátero Ferrífero to the northern Minas Gerais State. These two basins are affluent of São Francisco river in its right margin. The headwaters of Velhas and Jequitaí rivers are dominated by quartzites ridges structured during the Brazilian orogenic cycle. Less deformed metalimestones and metapelites are drained downstream. In response to these lithostructural contrasts, sensible variations of the rivers depositional or erosive pattern are seen. Many works point to the Cenozoic reactivation of ruptile structures along the two basins, however the investigated points are spatially disconnected and the research procedures are not the same. The integration of this knowledge could be possible by the study of fluvial systems since they are able to register the morphosedimentary effects of structural reactivations along their evolution. In this work the main baselevels of Velhas and Jequitaí river basins were identified by using tridimensional slope models generated from SRTM (Shutte Radar Topography Mission) images. Topographic maps in 1:100.000 scale were also used. After that, the fluvial morphologies of the accessible baselevels were surveyed in 1:500 scale. A log profile was described when possible. The number of mapping points defined in the Velhas and Jequitaí river basins were 14 and 12, respectively. The main morphotectonic and geologic aspects of the points sorroundigs were compiled in 1:50.000, 1:100.000 and 1:250.000 scales. In each point, the obtained morphologic map and log profile were analysed in relation to the neighborhood main lithologies, structures and Cenozoic reactivation zones. This step allows the establishment of some hypothesis about the morphosedimentary evolution of all studied points. The understanding of local fluvial dynamics resulted in a whole evolutive model to the two basins. The great number of baselevels of Velhas river basin has origin related to Cenozoic reactivation of ruptile structures. Nevertheless the heterogenic carstic collapse is the main responsible by the generation of the Jequitaí river basin baselevels. The results point to an eastward gradual tilt of the Velhas river basin, due to the reactivation of Brazilian structures. The northern and southern portions of Jequitaí river basin are tilting to the center, where is the main channel of Jequitaí river, draining the trough of the Jequitaí graben.

ASSUNTO(S)

geologia estratigráfica - cenozóico geomorfologia tectônica de placas engenharias

ACESSO AO ARTIGO

Documentos Relacionados