Influence of preexisting structures on the variation of neotectonic paleostress orientation in an area of the Southeastern Brazilian Margin

Abstract

The Southeastern Brazilian Margin presents a NE-SW-striking structural framework, which is characteristic of the Neoproterozoic Ribeira Belt. Other important structural trends along the area are associated with E-W and NW-SE-striking structures, being most related to the Mesozoic-Cenozoic tectonic evolution. A succession of Cenozoic tectonic events has been described by many authors in the Southeastern Brazilian. Among those Cenozoic tectonic events, a Neogene to Quaternary E-W dextral strike-slip regime (EW-DT) shows a wide distribution, presenting some variations in the stress field orientation. This research investigates the influence of the preexisting structural framework on the variation of the paleostress field orientation associated with the EW-DT tectonic event in a selected area in the onshore continental margin of the Southeastern Brazil. The study was carried out in three main stages: lineament analysis, paleostress field analysis, and numerical mechanical modeling. The paleostress field related to the EW-DT tectonic event in the studied area presents: NNW-SSE-striking maximum horizontal stress, and counterclockwise rotation influenced by the structural framework. Regarding this, the regional variation of the paleostress field is influenced by a preferential reactivation of NE-SW-striking structures while sets of approximately E-W-striking structures are the main local control of counterclockwise rotation of the stress field.