Dune systems an palaeoenvironments in southern Africa

Abstract

Extensive systems of fixed linear dunes occur throughout the Kalahari. Together the dunes form a semicircular arc with a radius of 1 000 km which corresponds approximately with the pattern of outblowing winds around the South African anticyclone. The dunes were formed by a wind regime broadly similar to that existing today. However, differences between dune alignments and present-day potential resultant sand flows in the northern part of the system suggest that shifts in the position and strength of the South African anticyclone may have taken place since these dunes were formed. Comparison of the extent of fixed dunes with that of the presently active dunes indicates that the extent of the arid zone in southern Africa has altered substantially in the past. Evidence exists for at least two periods of much greater aridity in the subcontinent, but their dating remains uncertain.