Morphostructural Analisys of Relief’s Hydrographic Region of Várzea River – High Uruguay River (RS)

Morphometric Analisys of Várzea's Hydrographic Region – Upper Uruguay River (RS)

Abstract

This paper presents the results of the analysis of morphometric data from the hydrographic region of the Várzea River - north of the Rio Grande do Sul State -, in the context of the upper Uruguay River basin and the Paraná Sedimentary Basin. The aim of this article was to evaluate whether the morphometric indices are indicative of the maturity of the relief and the quaternary tectonic influence in the region. The methodology relies on a morphostructural approach through the analysis of longitudinal and swath profiles, morphometric parameters and isobase surfaces. The main results showed that: (i) the hypsometric curves are predominantly convex and representative of a morphology that undergoes active denudation, for instance, the Guarita and Várzea rivers, lajeado Bonito and lajeado Grande; (ii) an erosive wave in the southern direction of the hydrographic region broadens the denudation of the upper plateaus (Planalto das Missões and Campos Gerais); (iii) there are erosive slopes, incision of the valleys and elaboration of the surface of the Dissected Plateau of the Uruguay River on which the greatest slopes are concentrated; (iv) there is a coincidence between the compressions of the isolines (therefore, of the topographic anomalies) and the limits of the plateau compartments depicted in the geomorphological mapping of the region (RADAM BRASIL, 2018). The morphogenesis of the relief in the region is coherent with the action of tectonic structural factors that lead the Uruguay River to be confined and yielded an erosive wave that is expressed in the drainage network.

Keywords: structural morphology, longitudinal profiles, fluvial dissection