Análise morfoestrutural da porção média da Bacia do Rio Tibagi - PR

Abstract

The present study perfoms a morphostructural analysis of the middle portion of the Tibagi River basin (PR), located between the municipalities of Tibagi (PR) and Telemaco Borba (PR), through morphometric indexes applied along 16 direct tributary basins of this river, with the purpose to establish the main types of controls acting on the general ways, such as the drainage network and types of valleys. For the purpose of conducting a general analysis of the drainage network, properties of drainage were established, so that it was possible to conclude that most of the study area covers a drainage network lattice with the main NW-SE direction, controlled by brittle structures, especially diabase dikes in the same direction. In some places it was recorded a three-way projection, supporting the hypothesis that some channels of NE-SW, N-S and E-W are controlled by faults and breaks. In addition to anomalous forms such as elbows and inflections on the Tibagi River, courses with paleo channels in flood plains were also identified, probably caused by tectonic uplift with tilting. In order to identify brittle structures along the tributary rivers studied, the Slope-Length index (SL) and Distance-Slope (DS) were applied which contributed to this identification and enabled to classify the areas by anomalies, and these demonstrated structural control for these rivers (NW-SE dikes), and a tectonic control to the Tibagi river (faults and breaks NE-SW). In order to identify the tilting in the tributary basins, the Transverse Topographic Symmetry Factor (FSTT) and Symmetry of the Valley Factor (FSV) were applied. The FSV was more effective to be used in embedded rivers, demonstrating there are possibly tilting blocks on the order of kilometers to NW, probably exercised by a process of uplift of the eastern border of the Paraná Sedimentary Basin along the axis of the Ponta Grossa Arch (where the search area is located) which causes an extensional regime in this same direction. This uplift process was also demonstrated by the Valley-Floor index (Vf) which revealed there is a proportionate amount of valleys in "V" closed for valleys in "V" open and in "U". Thus, it was perfomed a structural analysis by means of extraction and orientation of lineaments and determination of fractures in the field, in which especially vertical and subvertical fractures were identified, which strengthen the theory of an extensional regime of the region