Evolution of the northern Kwazulu-Natal coastal dune cordon, South Africa; Evidence from clays

The coastal dune cordon of northern KwaZulu-Natal is amongst the highest in the world reaching heights in excess of 180 m and up to 2 km in width. It comprises a complex system of Quaternary stacked dunes of various geomorphologies, types and ages. The dunes contain economic heavy minerals which are currently exploited similar to20 km north of Richards Bay. Although mining of these ore sands has been in operation for the last two decades, little work has been undertken on the clay-fraction (<2 mum). The distribution of clay assemblages includes kaolinite-illite-smectite-random interstratifications and the accessory minerals quartz, goethite, calcite, feldspars, fluoroapatite and Fe-Ti oxides, provide a basis for subdividing the dune complex into distinct units. A sedimentological interpretation based on field relations, and geochronological studies show that smectite dominated dune units are younger than the older kaolinite dominated units.