Holocene palynology and palaeoenvironments in the Savanna Biome at Tswaing Crater, central South Africa

Abstract

A radiocarbon dated pollen and microscopic charred particle record from the Holocene section of the Tswaing Crater in the Savanna Biome of South Africa give new evidence for environmental changes during the period c. 9400–1800calyears BP. Pollen grains are scarce or absent in layers dating from before 9400calyears BP but deposits rich in pollen occur in overlying layers. The section dated between 9400calyears BP and c. 7200calyears BP contains grass, Asteraceae and dry savanna pollen types that suggest fluctuating but generally dry moisture conditions. Later between c. 7200 and 1800calyears BP, broad leaved savanna woodland elements and local swamp pollen indicate relatively stable vegetation and wetter mildly fluctuating climatic conditions, which is consistent with previously published biomarker analysis. Between c. 6200 and 5500calyears BP, the numbers of charred particles increased slightly. This indicates burning activity, which can probably be attributed to dry season ignition of denser fuel under relatively moist conditions. A decrease of local swamp pollen between c. 3600 and 3500calyears BP suggests that conditions became briefly drier again as pollen of woody elements declined in favour of open grassland pollen. A comparison between the Tswaing pollen profile and various other sequences within the central interior of South Africa suggests generally similar conditions over the central interior of the sub-continent during the Holocene deviating from sequences further afield along the coastal areas of southern Africa. Between 9400calyears BP and ca. 7200calyears BP, the western and southern coasts were probably controlled by different atmospheric and oceanic circulation regimes under the influence of a strong westerly winter–rain system while the north-eastern area where, Tswaing is situated, experienced weaker precession and less summer rain from the Intertropical Convergence Zone.