Dynamics of late Cenozoic aeolian deposition along the South African coast: a record of evolving climate and ecosystems
Dune systems along the South African coast are sensitive barometers of fluctuations in palaeoenvironments, as archived in their orientation, geometry, internal architecture, composition, granulometry, diagenesis, palaeontology and archaeological content. Presently, the pronounced climatic/oceanographic gradients around the southern African coastline, including the west coast Mediterranean climate type, with cold upwelling to progressively warmer in terms of climate and sea temperatures eastwards, are mirrored by variations in these parameters. Here, we review and contribute new information concerning their fluctuations from the Miocene to the present to track changes in the bio-, hydro- and geospheres through time. West coast dunes take the form of dune plumes, which have an orientation since the Miocene that mirrors the southerlies of the South Atlantic Anticyclone (SAA), muted during the warm Pliocene, as reflected by intense bioturbation. Shoreline-parallel, vertically aggraded dune cordons dominate along the southern and eastern coasts, formed by (winter) polar westerlies since the Miocene. The contrasting dunefield morphologies relate to seasonality of wind strength and precipitation. Subtropical east coast dunes are profoundly weathered – on the shelf, glacial-period dunes indicate different atmospheric circulations. The long-term stability of the warm Agulhas Current contrasts with variability in the Benguela. The aeolianites host a rich human and faunal archive, including human ichnofossils.