Asymmetric continental deformation during South Atlantic rifting along southern Brazil and Namibia

Salomon, E., Passchier, C. and Koehn, D. (2017) Asymmetric continental deformation during South Atlantic rifting along southern Brazil and Namibia. Gondwana Research, 52, pp. 170-176. (doi: 10.1016/j.gr.2017.08.001)

Abstract

Plate restoration of South America and Africa to their pre-breakup position faces the problem of gaps and overlaps between the continents, an issue commonly solved with implementing intra-plate deformation zones within South America. One of these zones is often positioned at the latitude of SE/S Brazil. However, geological evidence for the existence of a distinct zone in this region is lacking, which is why it remains controversial and is not included in all modeling studies. In order to solve this problem we present a study of multiple geological aspects of both parts of the margin, SE/S Brazil and its conjugate part NW Namibia at the time of continental breakup. Our study highlights pronounced differences between these regions with respect to Paraná-Etendeka lava distribution, magmatic dyke emplacement, basement reactivation, and fault patterns. In Namibia, faults and dykes reactivated the rift-parallel Neoproterozoic basement structure, whereas such reactivation was scarce in SE/S Brazil. Instead, most dykes, accompanied by small-scale grabens, are oriented margin-perpendicular along the margin from northern Uruguay to São Paulo. We propose that these differences are rooted in large-scale plate movement and suggest a clockwise rotation of southern South America away from a stable northern South America and Africa, in a similar way as proposed by others for a Patagonian continental section just prior to South Atlantic rifting. This rotation would produce margin-parallel extension in SE/S Brazil forming margin-perpendicular pathways for lava extrusion and leading to the asymmetric distribution of the Paraná-Etendeka lavas. NW Namibia instead remained relatively stable and was only influenced by extension due to rifting, hot spot activity, and mantle upwelling. Our study argues for significant margin-parallel extension in SE/S Brazil, however not confined to a single distinct deformation zone, but distributed across ~ 1000 km along the margin.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Koehn, Dr Daniel
• Authors: Salomon, E., Passchier, C., and Koehn, D.
• College/School: College of Science and Engineering > School of Geographical and Earth Sciences > Earth Sciences
• Journal Name: Gondwana Research
• Publisher: Elsevier
• ISSN: 1342-937X
• ISSN (Online): 1878-0571
• Published Online: 07 August 2017
• Copyright Holders: Copyright © 2017 International Association for Gondwana Research
• First Published: First published in Gondwana Research 51:170-176
• Publisher Policy: Reproduced in accordance with the publisher copyright policy