Valley-marginal sand dunes in the south-west Kalahari: their nature, classification and possible origins

This paper considers the nature, classification and possible origin of a va riety of desert sand dunes which occur in association with ephemeral draina ge features in the south-west Kalahari. The dune forms, which we term valle y-marginal dunes, are found at the top of valley flanks, and are narrow, el ongate forms with arcuate and straight planform elements which mirror the c ourse of extant and ancient channels. Following a discussion of the major s chemes used to classify different dune types, we describe the morphology an d situation of these valley-marginal dunes. We suggest that whilst the basi c morphometry of these dunes is similar to many other dune types, the topog raphic setting in which they occur is relatively unusual. We conclude that valley-marginal dunes are a previously unrecognized landform which cannot b e fitted into current classificatory schemes. It is suggested that one reas on for this may be the lack of an explicit temporal dimension in most dune classifications. (C) 2000 Academic Press.