The almost circular Roter Kamm impact crater, in 1200 Ma granitic gneiss of the Namaqua Metamorphic Complex of the southern Namib Desert, has a diameter of 2.5 km and an age of 4–5 Ma. A variable orientation of the foliation in the rim gneisses is suggestive of large-scale brecciation of the rim. Along some parts of the rim, the average orientation of the foliation in the rim gneisses is tangential, along other parts it is radial, and along still other parts it is random. New analyses of large samples of the rim gneisses demonstrate a large-scale chemical heterogeneity of the target rocks. Black cataclasite veins, although mineralogically identical to their host gneisses, are almost invariably more potassic than the latter. The ejecta apron outside the crater was deposited on the earliest, fossil-bearing, eolian sands of the Pliocene to Holocene Sossus Sand Formation. Subsequent calcretization cemented the apron, but erosion and redeposition of the ejecta have not been significant in the desert environment of the southern Namib. Younger Sossus Formation sands now fill the crater and partly cover the rim and the ejecta apron. Ejecta outside the crater are most abundant in an outward-fanning apron extending from the north-northwest to the west of the crater. Blocks between 20 cm and 1.5 m in size are concentrated in this main apron in concentrically and radially orientated swaths. The longest of the latter extends 5.5 km to the northwest of the crater. Sizes of fragments on the crater rim and mappable features in the rim that can be followed and fan out into the ejecta apron, together with a slight asymmetry of the crater, suggest that the trajectory of the impacting body was northwesterly.

The sand sea that composes a large part of the Namib Desert in South West Africa covers approximately 34,000 km 2 and extends from the Great Escarpment on the east to the Atlantic Ocean on the west, south of the Kuiseb River. This sand sea, or erg, contains most of the principal dune types that have been recognized throughout the world, many of them of great height and separated by broad, flat interdunes. The dominant type and by far the most common form is the linear (seif, longitudinal) dune that extends as a series of long, nearly parallel ridges with north-south orientation across the length of the dune field. Studies of dune structure were made largely by trenching the various dune types to expose sections of cross-strata in selected parts. The trenches showed that those dunes attributed to unidirectional winds—barchan, barchanoid ridge, and transverse—with low-angle foresets on the windward sides and high angles on the lee sides, are mostly located along a narrow belt on the Atlantic Coast. The large interior dunes of linear type showed high-angle dips on both sides of the ridges and are believed to result from alternating two-directional winds. Because the genesis of these dunes has long been controversial, a review is given of the other principal hypotheses—deflation, helical roll, modification of simple dune forms, and outcrop-controlled lee-side accumulation—and evidence is presented for and against each. The most complex of dune types, in which arms radiate from a central point, is referred to as a star dune and is fairly numerous in various parts of the sand sea, especially near the vleis and along the northern dune margin. Such dunes are considered, both on the basis of data from trenching and from records of measured winds, to be the product of wind from three or more directions. Star dunes form along the ridges of linear dunes and also as isolated mounds on the desert floor, and they attain considerable heights. Minor dune types that are described and briefly discussed are those controlled by vegetation and referred to as coppice dunes. Also the small types known as dome dunes and blowouts, both of which were structurally analyzed, are discussed.