The Rio Bonito fault belongs to the group of Precambrian shear zones with direction NE-SW, reactivated by the extensional tectonic event associated with rupture of the Gondwana continent, which structures are responsible for the evolution of the Brazilian south-southeastern landforms. This fault is a bend of the Taxaquara fault developed near to Campos da Cunha (RJ) that, following the strike NE, crosses adjacent to the São José do Barreiro (SP), up to Volta Redonda (RJ), limiting the homonymous basin at northwest. Geomorphologic elements, configuring morphotectonic features, observed along the fault, exhibit indications that the reactivation is still in course, associated with the compressive couple NW-SE. The main features of reactivation are slickensides, asymmetries of the Barreiro de Baixo river valley that fit along to this fault, drainage anomalies and specific landforms. Outstanding features can be observed like lateral stream migrations associated with tilting of blocks to NW and SE, knick points, meander scars belts that eventually becomes to oxbows lakes, belts of well defined meanders, ruptures of terraces, drainage captures creating elbows and wind gaps, deflection and offsets drainage along the line of strike slip fault NE-SW and E-W. The morphotectonic features are identified by aligned suspended hollows, shutter ridges, gullies and triangular facets with evolution associated with the Holocene erosion of the fault scarp. The erosion was responsible for a large deposition of alluvium-colluvium sediments along both valleys and hollows. Active compressible stress are suggested by the abrupt vertical incision of the drainage in the floodplain of Barreiro de Baixo river, terraces and, eventually, in Holocene colluvium fans. This tectonics promotes warping in the area, as well as the rearrangement of alternate blocks, as observed in the Brazilian Platform.
*Supported by FAPESP, process 95/04417-3.