The synrift Etjo Sandstone Formation is a 200m thick eolian/fluvial succession exposed in the Huab Basin of northwestern Namibia. Eruption of Etendeka flood basalts ‘drowned' the erg and, in doing so, preserved in situ dunes with amplitudes and wavelengths of up to 80m and 2km, respectively. The Etjo thus provides a unique opportunity to relate complex bounding surface geometries to the bedforms responsible for creating them. In order to reconstruct the geometry of the system, architectural element analysis has been used to construct 12km of cross-sections, enabling deposits to be placed within the structural framework of the basin. Differential rates of subsidence have been fundamental in controlling preserved bedform thickness.

The basal 0-30m of the succession comprises mixed eolian/fluvial deposits which reflect a gradual increase in eolian sand supply to the basin center and a corresponding migration of fluvial facies towards the basin margins. These deposits are bounded at their top by a regionally extensive supersurface that represents a significant reorganization of the depositional system related to either a reduction in accommodation space or in extrabasinal sediment supply. The overlying main eolian succession is characterized by 200-500m wide troughs exposed in sections orientated perpendicular to the paleowind. These relate to gently climbing migration surfaces in sections parallel to the wind and are interpreted to represent draa-scale transverse bedforms with crescentic slipfaces, the preserved thicknesses of which are controlled by syndepositional rates of accommodation space creation. The onshore Etjo Formation is a direct analogue for the Kudu gas field, offshore southern Namibia.