Gondwana paleosurfaces in the state of rio grande do sul, Southern Brazil

Abstract

Abstract Several papers in Brazil have identified the importance of the planation surfaces in the evolution of the landscape, particularly those referring to the Gondwana Surface and the “Sul-Americana” Surface. These works were especially common between the 1950s and 1970s. Starting with the 1980s, such contributions became much scarcer. More recently, several, more appropriate dating techniques stimulated again the publication of papers related with these themes. This study has the aim of reviewing the knowledge about the paleosurfaces of the state of Rio Grande do Sul. The investigation discusses the summit surfaces named by Ab’Sáber as the Vacaria Surface and the Caçapava do Sul Surface. The Vacaria Surface is carved into Mesozoic effusive rocks, whereas the Caçapava do Sul Surface has a much more complex evolution, basically eroded on Precambrian rocks. Contrarily to other areas of Brazil, the surface carved in the oldest rocks is located at intermediate elevations. The Vacaria Surface evolved during the Late Cretaceous and the Paleogene, whereas the Caçapava do Sul Surface has an even older development, typically corresponding in this area to the Gondwana Surface, with some particular characteristics which are unique in regional terms, as remnants of Triassic sedimentary rocks on top and evidence of lateritic profiles, which today occur only in the lowest parts of these sections, but which had influence on the development of some landforms until today.