Morphotectonics in intraplate setting: The case of the western border of the São Paulo Basin – Southeastern Brazil

In the last decades, many researches have highlighted the role of Neotectonics on landforms in intraplate settings. However, the low magnitude seismicity and the action of erosion and weathering, which obliterates traces of tectonic activity, present great challenges to recent tectonic studies in some regions, such as in the Precambrian basement of South and Southeast Brazil. In this way, the objective of this research is to explore the Neotectonic activity and its relationships with landforms in the transition between the western border of the São Paulo Basin (Paleogene) and the Precambrian basement. In order to achieve this aim, topographic and aeromagnetic lineaments were traced in Shuttle Radar Topography Mission (spatial resolution: 30 m) and aeromagnetic data, respectively, and compared with seismicity data. Structural data were surveyed in outcrops, and paleostresses were computed by the fault-slip inversion with Daisy 3 software. Morphometric indices (Stream Length-Gradient Index, Basin Shape, Asymmetry Factor) were calculated in order to evaluate possible tectonic signatures on landforms, especially in the drainage network. In addition, a detailed morphotectonic map of a subset of the study area was done. The results of this work indicate that the study area shows several traces of tectonic activity (rectilinear water divisors and streams, elbows, asymmetrical valleys, right-angle confluences, knickpoints, elongated drainage basins, triangular facets and hillslope breaks). However, there is not structural data supporting the hypothesis that old shear zones have been reactivated in the current tectonic environment. The strong tectonic control on the landscape seems to reflect particularly an adaptation of the fluvial system to ancient inherited structures printed in the Precambrian basement.