Intraplate Strike-Slip Corridor within South America (NE Border of the Paraná Basin) Unveiled by Structural Analysis of Faults and Fracture Swarms

Abstract

We present the effect of neotectonics in intracratonic settings as revealed by the surface, brittle deformation associated to a regionally-sized shear corridor, which affects Southeastern Brazil. The deformation zone is characterized by the presence of nearly orthogonal fracture sets, interpreted as systematic and non-systematic joints often cutting Quaternary deposits. An original methodology of fault and joint inversion by the Monte Carlo converging approach is used to infer multiple paleostress fields. The method provides the best orientation of the principal paleo-stresses responsible for the observed fracturing. At each step of the inversion process, structures are uniquely associated to the stress tensor that provides the lowest error. The results showed the poly-phased tectonic history of the shear corridor studied and paleostresses compatible with a regional strike-slip motion. Specifically, an E-W, left-lateral shear was followed by an E-W, right-lateral kinematics related to the post-Paleogene drifting of South American Plate and its clockwise rotation. The latter tectonic event is presently responsible for brittle deformation observed in Quaternary deposits. The proposed deformation corridor may represent the Cenozoic reactivation of an ancient weakness zone. We speculate that the described intraplate strike-slip deformation belt represents the continental prosecution of the Rio de Janeiro fracture zone.

Multiple Reactivations of the Rennick Graben Fault System (Northern Victoria Land, Antarctica): New Evidence From Paleostress Analysis

“…Fault inversions show a variability in the found vertical principal component of the stress tensor. This can be interpreted as the interaction of the far field stress, of the local stress field (related to the RGF system kinematics) and of the overburden that may produce exchanges in the principal components (e.g., Cianfarra et al., 2022) yet always leaving the proper horizontal components congruent with the strike‐slip fault kinematics and therefore rather independent of the transtension/transpression conditions of the fault kinematics.…”

“…A specific approach was used to reveal the regional paleostresses within the expected scattered fault data (e.g., Cianfarra et al., 2022; see Text S3 and S4 in Supporting Information S1). The deformation measured in each investigated site results from the contribution of regional tectonic stresses and from local stresses that are negligible in the preparation of the regional tectonic evolutionary model of the studied area.…”

“…Fault inversions show a variability in the found vertical principal component of the stress tensor. This can be interpreted as the interaction of the far field stress, of the local stress field (related to the RGF system kinematics) and of the overburden that may produce exchanges in the principal components (e.g., Cianfarra et al, 2022) yet always leaving the proper horizontal components congruent with the strike-slip fault kinematics and therefore rather independent of the transtension/transpression conditions of the fault kinematics. Specifically, in the following tectonic interpretations, we consider the regional strike-slip motion along the RGF system as the main deformation producing local stress affecting the investigated area in the recent/since the late Mesozoic (Salvini et al, 1997;Tessensohn, 1994).…”