The early Cambrian Kuboos-Bremen Igneous Province, of northwestern South Africa and southern Namibia, comprises a series of intrusive bodies that collectively encompass virtually the entire range of alkaline rock types. Two of these bodies, the Grootpenseiland and Marinkas Kwela Complexes, lie immediately north of the Orange River and are amongst the few that show this wide lithological range on a local scale. The rocks of both complexes are overwhelmingly felsic in composition. The oldest are nepheline-bearing syenites, which form the southwestern most intrusive phases. The sequence of intrusion in both complexes is to the northeast and to more siliceous rocks. Large granitic stocks form the youngest and most northeasterly intrusive phases. The same lithological range and intrusive sequence also occurs at Kanabeam, approximately 5 km to the northeast of Marinkas Kwela, indicating a close commonality in the origin and geological evolution of complexes in that region.