Abstract The southwestern part of the Karoo basin, South Africa is comprised of two mountain chains (Figures 1,2). The southern branch (Witteberg Swartberg Range) runs east-west, and the western branch (Cedarberg Range) is more or less north-south. Where the two meet is a northeast-trending syntaxis with two anticlinoria. This structural area encloses two foredeep areas, known as the Laingsburg subbasin and the Tanqua Karoo subbasin. The east-west running Laingsburg subbasin is a typical elongated foredeep. Later tectonic activities tilted this basin, with the result that the layers are close to vertical. Between the western branch and the anticlinoria is the location of the Tanqua Karoo subbasin. The outcrops of this basin now cover an area of 650 km2 (250 mi2). The basin is Permian age ( Figure 3 ; Wickens and Bouma, 2000 ). Gradual sinking of the basin has resulted in a 7–8-km (4.36–5.0-mi)-thick package of younger deposits overlying the deep-water sediments. A later rebound eroded overburden, with the result that the Permian deep-water deposits became exposed. The outcropping area is about 34 km (21 mi) long and has no tectonic dip in the north-south direction. The visible width varies from 8 to 12 km (5–7.5 mi), and shows 1–3° tilt to the east. Lack of vegetation exposes large outcrops along the western and southern sides, as well as in the middle along the Gemsbok River ( Figure 5 ). The outcrops make it possible to observe the depositional changes in the downslope direction. The subbasins formed during the Permian compressional collision