Sedimentology, isotopes and palynology of late Holocene cores from Lake Sibaya and the Kosi Bay system (KwaZulu-Natal, South Africa)

Abstract

This study documents a multi-proxy palaeoecological record spanning 2000 years for the northern KwaZulu-Natal coastal plain. Data are presented from cores recovered from Lake Sibaya and the northernmost coastal flats of the Kosi lake system. Sedimentation rates are higher in the dated Sibaya core than in the Kosi core. Carbon isotopic values from all three cores suggest that C3 plants have been the dominant biomass, with some C4 plant input at certain depths/times in the cores. Low nitrogen isotopic data in the cores suggest that nitrogen fixation processes occur in both systems. Due to high sample distance and often low pollen concentration, palynological data are restricted to a single core at Lake Sibaya. The pollen assemblages reflecting changes from greater forest abundances to greater savanna grassland abundances support results from a previous palynological study at the lake. The relative proportion of carbon in the samples decreases during the same time frame, potentially reflecting a decline in biomass volumes at the two ecosystems. Human impact is evidenced by the appearance of pine and probable maize pollen in the upper section of the core.