A rede de drenagem e seu significado geomorfológico: anomalias de drenagens e tectônica recente na bacia do rio Formoso, Tocantins

Abstract

This study has sought to identify the drainage anomalies in the basin of Formoso river as geomorphological evidence of tectonic action in the middle Araguaia. The study area is located in the southwestern portion of the state of Tocantins, established on granulitic Complete mobile tracks, and sedimentary covers. For the study, we made the use of GIS, storage, processing, classification and comparative and correlative analysis. From the interpretation of satellite images, it was made vectorization of the drainage system and basin watersheds and sub-basins, and regional subdivision of the relief via Digital Image Processing (DIP) with TOPODATA data, and measurement the hydrographical and geomorphological components. The study area was divided into 36 sub-basins, with higher than 5th order systems. The data collected indicate that this system is 8th order and has an area of 21,593 km² and a drainage network with 20,628 km of channels. The relief classification morfoesculturas scored four and eleven morphological units. morphometric indices drainage density (Dd), area density (Dh) and Sinuosity (Is), and geomorphic indices Asymmetry Factor Drainage Basin (FABD) and Factor Symmetry Cross Topographic (FSTT) were applied. The correlation Da and Dh indicated a strong linear correlation between the indexes, where the whole basin drainage density is prevalent median (0.5-1.5 km / km²), with river density of 0.5 channels / km² , which was considered very low, indicating difficulty in renewing the river network. The geomorphic indexes pointed out that the catchment area of the river Formoso has 76% of its area to the right of the main channel (East) area that features gently undulating and heavily undulating reliefs. The application of the parameters for sub-basins showed a strong degree of asymmetry of the streams of 5th order Grota da Mata and Green Water, located in the lower course. The structural data suggest that most of the failures are associated with lineament Transbrasilian SW-NE axis, and lineament Tocantins in SE-NW axis. fault systems were identified transcurrent most notably in the high course, extensional faults in medium and low current Cenozoic covers, and compressional faults imbricated with the lithological contact Neoproterozoic rocks in the Middle Depression Araguaia. It was possible to notice the (re) accommodation of fluvial channels on these structural assemblies that determine features of drainage anomalies, such as segments and straight stretches, river catches, segments with elbows right angles and abrupt inflections of channels. It was also noted, long stretches without a clear indication of the topographic watershed of rivers Formoso and Javaés on Quaternary coverage. Noteworthy is anomalous as conduits Sewage Snail among Javaés Rivers and Formoso, and another between the river and its tributary Formoso river Dueré, which indicated the establishment of river catches at different stages.