Mapping of this area, 6 500 km² in extent lying 70 km north-west of Omaruru, South West Africa, has revealed the following sequence of rocks, listed oldest to youngest: (I) gneiss of the Huab Complex; (2) the Damara Sequence comprising (a) Late Nosib to Early Swakop Naauwpoort Formation alkaline rhyolites, which are more than 6600 m thick and are characterised by very high K, high Ba, low Sr contents and an Rb deficiency (K/Rb=349), the extrusion of which was associated with block-faulting; it is suggested that the magma was generated by partial melting of chemically and mineralogically suitable deep crustal rocks, (b) Swakop Group of metasedimentary rocks consisting of 100 to 1 100 m of carbonate (Ugab Subgroup and Karibib Formation) overlain by almost 10000 m of schist (Kuiseb Formation), and (c) Mulden Group schist; (3) the porphyritic Salem Suite which has a border facies of diorite in the south-east; (4) the medium- rained Sorris-Sorris Granite, intrusive mainly into the Salem granite; (5) Karoo Sequence sedimentary rocks and sills and dykes of alkaline feldspar porphyry; (6) Karoo dolerite dykes and sills; (7) a previously undescribed intra- or post-Karoo stock of alkali granite and granite porphyry (Otjohorongo Granite) with associated ring dykes and cone sheets of quartz porphyry. The central granite stock is very highly differentiated (K/Rb=77) in relation to the outermost cone sheets (K/Rb=185); (8) the post-Karoo Okenyenya Complex; (9) the post-Karoo Kwaggaspan Carbonatite.