Testing Early Cretaceous Africa–South America fits with new palaeomagnetic data from the Etendeka Magmatic Province (Namibia)

Abstract

We provide an independent test for the proposed pre-breakup fits between the South American and African continental margins based on new palaeomagnetic data. In the course of modelling the opening of the South Atlantic Ocean, several reconstructions have been proposed, which correspond to different estimates of the amount of pre-drift extension in the South American and African continental margins, and amounts of displacement along intracontinental accommodation zones. The Paraná–Etendeka Large Igneous Province erupted during a brief time interval between ~136 and ~131Ma, just prior to opening of the South Atlantic, and has magmatic products on both the African (Etendeka lavas) and South American (Paraná lavas) plates. Here we provide new palaeomagnetic constraints on the Etendeka volcanic rocks. These yield a declination of D±∆Dx=314.4±7.0° and inclination of I±∆Ix=−42.7±8.3° (Plat=47.5, PLon=88.9, K=26.1, A95=6.3, n=21). When our results are combined with another recently published dataset, we obtain an Etendeka palaeopole at 49.1° S, 87.6° E (D±∆Dx=315.9±3.8°, I±∆Ix=−43.9±4.4°, K=23.4, A95=3.5, n=75). We compare three recent models for South Atlantic Ocean opening, discuss which of the models best fits the palaeomagnetic data, and present a revised reconstruction for West Gondwana during the Early Cretaceous.