The geology of the Owambo Basin is known from outcrops along its margins, from interpretation of seismic, aeromagnetic and gravity surveys and from a few widely spaced wells. The Owambo Basin is floored by mid-Proterozoic crustal rocks of the Congo Craton and contains possibly as much as 8000 m of sedimentary rocks of the Nosib, Otavi and Mulden Groups of the late-Proterozoic Damara Sequence, 360 m of Karoo rocks and a blanket of semi-consolidated to unconsolidated Cretaceous to Recent Kalahari Sequence sediments up to 600 m thick. Deposition of Nosib fluviatile sandstones began about 900 Ma ago during intracontinental rifting to the south and west and ended with local glacial deposition. As rifting evolved to spreading, the region of the Owambo Basin became a stable platform (Northern Platform of the Damara Orogen) marginal to oceans to the south and west. Carbonates of the Otavi Group were deposited between about 730 and 700 Ma on this platform. Two cycles of carbonate deposition (Abenab and Tsumeb Subgroups), each starting with quiet, relatively deep water (stromatolite-poor, laminated rocks) that became progressive shallower with time (stromatolites, oolites, evaporite(?) minerals), were separated by a widespread glacial episode (Chuos Formation). Reversal of plate motion in the adjoining oceans culminated in subduction and continental collision in the branches of the Damara orogen to the south and west. Erosion products of D1 uplift in the west were deposited as an upward-fining molasse (Mulden Group) in the Owambo Basin between 650 and 600 Ma. D2 deformation folded Mulden and Otavi rocks together and produced the uplifted, folded western and southern margins of the Owambo Basin that give it its present form. After extensive erosion, a Lower Permian ice sheet north of and within the Owambo Basin deposited the Dwyka Formation tillite. As this ice sheet retreated, Lower Permian basin plain and fluvio-glacial sediments and low-grade coals of the Prince Albert Formation accumulated. Middle Permian to Lower Triassic sediments are absent from the Karoo succession and, rather than having been removed by intra-Karoo erosion, may never have been deposited in this region. Prince Albert rocks are overlain in the Nanzi well by Upper Triassic aeolian sandstone of the Etjo Formation, the only known occurrence in the Owambo Basin. Basalts, probably correlates of the Kalkrand Formation of southern Namibia, occur only in the far eastern parts of the basin.