SLOPE DEVELOPMENT IN THE KLERKSPRUIT VALLEY, ORANGE-FREE-STATE, SOUTH-AFRICA

Recently published research results have shown that slope forms on the Clarens Sandstone Formation have evolved as a result of slope replacement. Further research east of the Golden Gate Highlands National Park, which has involved the surveying of slope profiles and the determination of rock resistance, has indicated that different modes of slope development have prevailed in various structural settings. That slopes developed entirely on the Clarens Sandstone Formation have evolved by slope replacement is confirmed, and a second phase of replacement which produces low-angle (14-degrees) bedrock slopes replacing the Richter-type (30-degrees-35-degrees) slopes is revealed. Further, it is shown that where fluvial incision has progressed into the underlying Elliot and Molteno Formations, slopes tend to maintain their form as they develop. The evidence suggests that slopes develop by parallel retreat where the Clarens Sandstone Formation acts as a caprock.