Linear Dunes Near the Orange River

Abstract

Abstract The sands of the linear dunes studied in the vicinity of the Orange River were probably produced and deposited during arid climatic conditions. The presence of unstable heavy minerals of the pyroxene-amphibole suite as well as the red colouring of the sand indicate that the detrital material was produced and deposited during arid climatic conditions. The mineralogical similarity between the dunes to the north and to the south of the Orange River indicates that the sand was able to cross the river. probably during the arid phase(s) of the Quaternary. The original lithological source of the dune sand is uncertain but the mainly quartzose nature of the sediment points to a granitic and/or sandstone source. The presence of small amounts of unstable minerals suggests some addition of material from local weathering. A few small brown dunes near the Orange River apparently are formed by sand being blown from the banks of the river. Mineralogically the reddish and yellowish dunes to the south of the Oran...