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

Salomon E, Passchier C, Koehn D (2017)


Publication Status: Published

Publication Type: Journal article

Publication year: 2017

Journal

Publisher: ELSEVIER SCIENCE BV

Book Volume: 51

Pages Range: 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 Parana-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 Sao 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 Parand-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. (C) 2017 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

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APA:

Salomon, E., Passchier, C., & Koehn, D. (2017). Asymmetric continental deformation during South Atlantic rifting along southern Brazil and Namibia. Gondwana Research, 51, 170-176. https://dx.doi.org/10.1016/j.gr.2017.08.001

MLA:

Salomon, Eric, Cees Passchier, and Daniel Koehn. "Asymmetric continental deformation during South Atlantic rifting along southern Brazil and Namibia." Gondwana Research 51 (2017): 170-176.

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