Modes of linear dune activity and their palaeoenvironmental significance: an evaluation with reference to southern African examples

Abstract

Abstract Supposedly relict continental desert sand dunes have frequently been used as palaeoenvironmental indicators. Often the argument has been, first, that vegetated dunes are fixed relicts, and second, that fixed dunes indicate past aridity. Recent work suggests that neither of these maxims is necessarily true. Using the example of the linear dunes of southern Africa, this paper examines the extent to which we can continue to support a simple assumption that vegetated dunes are inactive relicts. In particular, it addresses the problem of what constitutes activity on linear dunes, and suggests some hypotheses for investigating the ‘grey’ area between active, unvegetated dunes and densely wooded, inactive dunes. The concept of episodic activity is introduced in the context of partially vegetated linear dune forms.