Weathering of rock art at two sites in the KwaZulu-Natal Drakensberg, southern Africa

Sediments of the Karoo Basin in southern Africa represent one of the world's finest laboratories for investigating sandstone weathering. The natural breakdown of these sandstones, most notably in the Clarens Formation, is destroying much of the indigenous rock art heritage that exists there. In an attempt to elucidate the operative weathering processes, a range of micro-climatic, rock temperature, rock moisture, rock chemistry, and rock property data have been monitored over a 15 year period at two sites in the KwaZulu-Natal Drakensberg. Results suggest that rock moisture regimes and to a lesser extent, rock thermal regimes exert the most damaging influence on San paintings. It is argued that granular disintegration and the enlargement of existing sandstone pores and bedding planes close to the rock surface, facilitate an increasingly dynamic moisture regime, which leads to an accelerating rate of weathering. Recent technological advances in data collection suggest that a re-evaluation of environmental controls may be necessary before weathering, at a scale appropriate to the deterioration of rock art, can be fully understood. The continued existence of indigenous rock art in southern Africa depends on investigations aimed at the development of techniques for its preservation.