Weathering of Coastal Dunes in Northern KwaZulu-Natal, South Africa

Abstract

Abstract This paper identifies and quantifies the clay assemblage within coastal dunes of northern KwaZulu-Natal, South Africa, and proposes a model for clay distribution and abundance. Distinct dune units identified by previous authors on the basis of the sand fraction are redefined on the basis of the composition of the clay fraction. The most mature dune unit is classified as Unit 0 (250–350? ka) and is characterised by a clay assemblage rich in kaolinite and goethite. Units 1 and 2 (19–250 ka) are of intermediate maturity and comprise kaolinite, interstratified clays, quartz, and goethite. The relatively immature Units 3 and 4 (Recent to 19 ka) are characterised by calcite, quartz, vermiculite, and montmorillonite. The relative abundance of clay minerals in dune units allows weathering and postdeposition alteration processes within the dunes to be investigated. From these, a simplified weathering sequence with increasing maturity can be summarised as follows: quartz + feldspars + calcite + heavy miner...