Some Swaziland Examples of Localised Control of Base Levels: The Middle Ngwempisi Basin

From similarities in topography, climate, vegetation and soils, an enclosed basin of undulating country along the middle, reaches of the Swaziland Ngwempisi is considered to be an isolated outlier of the Western Middleveld physiographic region. However, the occurrence of massive ferricrete and old alluvial deposits indicate that Quaternary base level depression was slower and more spasmodic in the Ngwempisi basin than elsewhere in the Western Middleveld. This hiatus is attributed to the obstruction to the upstream migration of a nickpoint by the hard ultra basic rocks outcropping in the Ngwempisi Gorge area downstream of the basin.