Of special interest is the South Atlantic, because the bounding continents have very different recent geological histories, with Africa experiencing continental rifting whereas South America is influenced by subduction on the Pacific side.It is not clear to what extent the Atlantic continental margins are subject to the same stresses and vertical motions as the main continents.The Pirambóia and Botucatu Formations are composed of quartz sandstones and subordinated siltstones.The Serra Geral Formation comprises tholeiitic basalt lava flows and associated intrusive rocks.The results of NW Namibia differ from known compressional stress tensors in western South Africa, post-dating 90 Ma.To address this problem, we performed a paleostress analysis of two originally adjacent areas, i.e. Both areas are covered by the ~ 133-Ma-old Paraná-Etendeka extrusives that were emplaced shortly before or during the onset of the Atlantic rifting.Thus, the volcanics serve as a time marker for syn- or post-rift deformation.SE/S Brazil was mostly affected by strike-slip faulting, with compression oriented E-W and SW-NE.
Descriptive and kinematic structural analyses reveal the imprint of two brittle deformation phases: D1, controlled by the activation of an extensional system of regional faults that represent a progressive deformation that generated discontinuous brittle structures and dike swarm emplacement along a NW–SE trend, and D2, which was controlled by a strike-slip (transtensional) deformation system, probably of Late Cretaceous–Tertiary age, responsible for important fault reactivation along dykes and deformation bands in sandstones.
ABSTRACT: The “passiveness” of passive continental margins across the globe is currently under debate since several studies have shown that these margins may experience a variety of stress states and undergo significant vertical movement post-breakup.
Collected fault slip data in the volcanics reveal remarkable differences between the two correlating areas.
NW Namibia was dominated by extension in ENE-WSW and SW-NE directions, and by minor strike-slip movement with NW-SE directed compression.
The integration of structural analyses of outcrops, aerial photographs, satellite images, aeromagnetometric data, and digital terrain models can establish the structural framework and paleostress trends related to the evolution of Ponta Grossa Arch, one of the most important structures of the Paraná Basin in southern Brazil.
In the study area, the central-northern region of Paraná State, Brazil, the arch crosses outcropping areas of the Pirambóia, Botucatu, and Serra Geral Formations (São Bento Group, Mesozoic).