APPLICATION OF RELATIVE-AGE DATING METHODS TO OPENWORK DEBRIS FLOW DEPOSITS IN THE CEDERBERG MOUNTAINS, WESTERN CAPE, SOUTH AFRICA

ABSTRACT

Boulder-surface dating techniques have been applied in many mountain and high-latitude environments, but have not yet been explored in the southern African region. This paper reports on the results of a pilot study to provide relative ages for openwork debris flow deposits in a part of the Cederberg mountains. Field techniques used included rock surface hardness assessment using a Schmidt hammer, lichenometry, and the determination of weathering rind thickness and weathering pit diameters. Within the eleven deposits investigated two age populations are successfully identified. Despite inherent weaknesses, analysis of the results show that the Schmidt hammer, weathering rind thickness and total percentage lichen give statistically significant results. Although the Schmidt hammer technique appears most objective on its own, it is the combined assessment of the various techniques that provides the most reliable results.