Debris ridges along the southern Drakensberg escarpment as evidence for Quaternary glaciation in southern Africa

Abstract

Considerable geomorphological work has been undertaken on periglacial and possible glacial landforms found in the eastern Lesotho highlands. However, the origin of several of these landforms remains controversial and differences in opinion concerning their original process mechanisms and associated climatic implications is unresolved. Debris ridges were recently found on south-facing slopes along the Tsatsa-La-Mangaung and Leqooa Ranges in the southern Drakensberg. The objective is to use a variety of approaches to test a number of possible hypotheses to their origin. These include an analysis of topographic and spatial positioning, geomorphology, sedimentology, AMS dating and palaeo-climatological extrapolations. A variety of possible geomorphological process origins for particular deposits are tested against the results of the above-mentioned approaches. The possible origins considered include debris flows (water flow), pronival ramparts (seasonal/perennial snow patches), glacial moraine (permanent glacier/ice) and variations in landscape denudation (i.e. erosional remnant; e.g. valley fill). The results support the contention that the ridges are moraines, which relate to the former presence of small glaciers.