Periglacial phenomena in Basutoland and the Drakensberg of Natal

Abstract

Article in French.

ORIGINAL TITLE: Phénomènes périglaciaires dans le Basoutoland et le Drakensberg du Natal

The north-eastern, highest part of the Drakensberg Mountains (over 3,000 m), lies at approximately 30° south latitude and is, in a sense, equivalent to the Atlas Mountains. Relatively heavy snowfall and over 180 days of frost occur there. Currently, no significant ground freezing is observed. Surface runoff from melting snow causes size sorting of the surface material, which is significantly enhanced by the impermeable basalt bedrock and its weathering products. Fossil periglacial terrain forms are numerous. Near the summits, on moderately sloping slopes, solifluction deposits appear, causing asymmetry in the shallow valleys. Sandstones and layered scree cover the steeper slopes. In the valleys, located over 1,000 m below the summits, alluvial fans extend that are composed of very large rock fragments, which in turn are products of frost weathering at higher elevations. The interpenetration of sediments indicates two relatively recent cold periods. Under favourable conditions, the youngest cones are covered by much finer sediments, meaning they were deposited under much less harsh climatic conditions.