An Assessment of Basement Inheritance in SE Brazil

Abstract

SE Brazil, especially the Central Segment of the Ribeira belt, in theory is an ideal place to investigate reactivation of pre-existing structures or basement-influenced faulting due to its position on the South Atlantic margin and large area of basement exposure, however it offers several obstacles due to its high rates of weathering and erosional processes, and amongst others, difficulty in correlating the brittle history with neotectonic processes.
This project focused on finding at outcrop scale evidence for basement inheritance or basement influence in the deformation processes of the area and present day tectonics. Fieldwork and remote sensing analysis were used as well as alternative solutions to acquire data and these results were integrated with previous publications.
The area displays predominantly steeply dipping fault structures that are consistent with its main basin architecture and in particular the Santos basin which sits parallel to the study area. The area has a geological history that differs from its surroundings due to its geological setting. The Central segment of the Ribeira belt is where the Continental Rift of SE Brazil Tertiary basins are localised. These basins are evidence of relatively recent deformation histories and are great assets to investigating local control to geological structures. Many outcrops were visited, and at the end only the ones offering a good display of information were used provide evidence support inheritance/influence of the basement and are described in this report. Few structures displayed reactivation evidence, whereas basement influence could be observed throughout the area considering the criteria necessary to infer it. More time and resources would be necessary to uncover reactivation evidence for the onshore continental margin, this would be also vital to understand intraplate seismic activity in the area and beyond.