Unravelling the along-strike variability of the Angola–Gabon rifted margin: a mapping approach

Abstract

Abstract We summarize here observations from the South Atlantic Angola–Gabon rifted margin. Our study was based on the interpretation of a selection of deep penetration depth-migrated seismic reflection profiles. We describe here the large-scale dip architecture of the margin under five structural domains (proximal, necking, distal, outer and oceanic) and list their characteristics. We investigated the necking domain further and discuss the architecture of the distal domain as a combination of hyper-extended crust and possible exhumed mantle. The mapping and characterization of these domains, at the margin-scale, allow us to illustrate the along-strike structural and stratigraphic variability of the margin. We interpret this variability as the result of a shift from an upper plate setting to a lower plate setting. This shift is either sharp, typified by a major regional normal fault on the northern flank of a residual hanging-wall block, identified offshore Cabinda–Zaire, or more diffuse to the south. First-order screening of conjugate profiles confirmed the segmentation and structural characteristics of the transfer zones. The dataset studied also allowed the identification of key sections that can be considered as type examples of upper plate and lower plate margins and which allow us to discuss the characteristics of these end-member settings.