Summary Seismic reflection profiles and gravity anomaly data have been used to determine the structure and evolution of the Namibian continental margin. In comparison to other margins, the gravity anomaly at the Namibian margin shows a number of distinctive features. It lacks an offshore gravity ‘low’, and, despite the presence of up to 9 km of sediments, the gravity ‘high’ is displaced landwards of the maximum sediment thickness. In an attempt to explain these features, the Early Cretaceous–Recent stratigraphic record is analysed using a combined 3‐D backstripping and gravity modelling tech‐nique that enables constraints to be placed on the long‐term mechanical properties of the lithosphere. A neutral depth of necking and a relatively high flexural rigidity (or equivalent elastic thickness, Te, of ~ 25 km) can explain part of the anomaly, at least in the south of the margin. However, large residual anomalies exist that can be reduced by the presence of pre‐rift low‐density sediments within the zone of maximum stretching, south of 22° S, high‐density volcanic material at the eastern pinch‐out of the lower rift sequence and a lateral sediment density variation across the shelf, slope and rise. In addition, the presence of a magmatic body at the base of the crust, provided that the flexural strength of the margin is high, significantly improves the fit between observed and calculated gravity anomalies. Recovered stretching factors enable predictions of the geometry of the Moho to be made. Palaeobathymetry is estimated along the entire margin through time by comparing the subsidence determined from backstripping to that predicted by simple models of rifting. These estimates are within the errors of observed palaeowater depths where well control exists. The requirement of high Te rather than Te that increases with time suggests that stretched continental crust extends offshore for some distance and the continent–ocean boundary occurs in relatively deep water near magnetic anomaly M4. Reconstruction of the gravity field of the South Atlantic at 100 Ma illustrates that, in terms of their gravity signature, the South Atlantic margins are asymmetric.

Seismic stratigraphic analysis of the post-rift megasequence of the Namibian passive continental margin has enabled depositional features to be interpreted in terms of the likely controls on their formation. The scale of the information derived from this manner of depositional system analysis is fundamental in understanding processes of sedimentation on passive margins; processes which may not be so readily apparent at field or well-log scale studies. Inner shelf channel forms are interpreted as incised valleys, created during a fall in relative sea level. The horizontal nature of the seismic facies infilling these valleys suggests that they filled during progressive periods of rising relative sea level, implying late lowstand or transgressive sediments. A series of low mounded features can also be identified on the shelf, which may be interpreted as palaeodune fields, carbonate build-ups or longshore clastic mounds. The outer shelf and upper slope positions reveal interpreted canyon and channel forms. The infill to these features contrasts with that of the incised valleys by having a more draped from (sometimes with a chaotic unit below); a geometry consistent with submarine origins. The submarine canyons may be termed attached or detached depending on whether they can be shown to link back into fluvial systems on the shelf; attached canyons will be more likely to be able to support the development of deepwater, sand-rich submarine fans. In the slope/base of slope area both regionally extensive and more localized mounds can be interpreted as mass transport deposits, the trigger for which may be attributed to a relative sea-level fall (due to their connection to the valley and canyon systems), though a transgressive origin may also be consistent in some cases. The mounds seen in positions deepest in the basin have a markedly different seismic facies to those at the base of slope and a different depositional system may be invoked, perhaps that dominated by distal turbidity currents or waning bottom currents.

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