Slope Development on the Clarens Sandstone Formation in the Northeastern Orange Free State

The landscape on the Clarens Sandstone Formation in the Golden Gate Highlands National Park (northeastern Orange Free State) is characterised by slope forms exhibiting rectilinear elements. In general, such slopes are of two types: cliff-talus slope combinations on which both elements are rectilinear, and bedrock slopes inclined at angles of 30°–35° which constitute entire valley sides. Vertical and near-vertical cliffs are strength eqUilibrium forms in that their gradients are in equilibrium with the mass strength of the sandstone. Lower-angled rectilinear bedrock slopes are not in strength equilibrium, and they are not structurally controlled. Consequently their forms are determined by the action of denudational processes. Analyses of slope forms, the mechanical characteristics of the bedrock, and the nature of debris on the slopes indicate that different forms reflect a sequence of stages in slope development, and that the rectilinear bedrock slopes are equilibrium transport slopes which have developed by replacement.