Volcanic constraints on the unzipping of Africa from South America: Insights from new geochronological controls along the Angola margin

Abstract

The breakup of Africa from South America is associated with the emplacement of the Paraná-Etendeka flood basalt province from around 134 Ma and the Tristan da Cunha plume. Yet many additional volcanic events occur that are younger than the main pulse of the Paraná-Etendeka and straddle the rift to drift phases of the main breakup. This contribution reports on new geochronological constraints from the Angolan part of the African Margin. Three coastal and one inland section have been sampled stretching across some 400 Km, with 39Ar/40Ar, U-Pb and Palaeontology used to provide age constraints. Ages from the new data range from ~100 to 81 Ma, with three main events (cr. 100, 91 and 82–81 Ma). Volcanic events are occurring within the Early to Late Cretaceous, along this part of the margin with a general younging towards Namibia. With the constraints of additional age information both onshore and offshore Angola, a clear younging trend at the early stages of rift to drift is recorded in the volcanic events that unzip from North to South. Similar age volcanic events are reported from the Brazilian side of the conjugate margin, and highlight the need to fully incorporate these relatively low volume volcanic pulses into the plate tectonic breakup models of the South Atlantic Margin.