The palynology of two overlapping Holocene cores from Lake Sibaya in KwaZulu-Natal elucidates the relationship between climate, vegetation and human impact in the region. By means of twenty-one AMS 14C dates, loss on ignition, and palynological results we established a composite profile. Pollen assemblages include elements of swamp forest (e.g. Rauvolfia, Macaranga), dune forest (e.g. Mimusops), mangrove vegetation (Bruguiera), palmveld (e.g. Phoenix) and bushveld (e.g. Spirostachys, Sclerocarya). Poaceae, aquatics and Cyperaceae are abundant, and fynbos elements like Ericaceae and Restionaceae are rare. Based on comparisons between palynological and archaeological/historical data, the radiocarbon dates seem to show an age error of 50-550 yr, which is probably due to a hardwater reservoir effect. Applying the mean of this error range to our age model suggests that the oldest sediments represent ~ 6750-7100 cal yr BP, that a > 5000 yr hiatus occurs ca. 253 cm depth, and that the upper 253 cm of the composite profile covers the period between ~ 1300-1500 cal yr BP (~ 450-650 AD, Early Iron Age), and 2004 AD. The Middle Holocene is characterized by high tree pollen values (especially Phoenix) suggesting warm humid conditions. The Early Iron Age is characterized by high Podocarpus percentages that indicate moist but possibly cooler climatic conditions. The upper part of the pollen sequence is characterized by the decrease of Podocarpus, Isoglossa and Celtis and a rise in Spirostachys. Increasing values of cereal pollen and algae might reflect human activity. Zea mays appears ~ 150-300 cal yr BP in the pollen sequence according to the radiocarbon chronology and both archaeological and historical evidence. The curve of Pinus pollen rises to 50-70% at the top of the diagram, reflecting the spread of pine plantations since the 1920's, and Poaceae values decrease. Stoebe and the introduction of neophytes like Ambrosia and Casuarina suggest recent human disturbance.
Bibliographical noteFunding Information:
We gratefully acknowledge financial support from the United States National Science Foundation (Earth Systems History grants ATM-9808972 and ATM-01117170), from Paul Smith's College and from the South African National Research Foundation (grants for F. Neumann and L. Scott). Any opinions, findings, and conclusions are those of the authors and the NRF does not accept any liability in regard thereto. The manuscript has benefitted from discussions with Brian Chase, Janusz Zwolinski, Johan Grobbelaar, Gavin Whitelaw, Thomas N. Huffman and numerous members of the SASQUA 2007 conference. We also thank Rodney Maud, Rio Leuci, Wade Kidwell, Tim Partridge, Johann du Preez, Charles Barker, Petrus Chakane and Steve Norton for logistical and technical support. Jason Fitzpatrick, Matthew Hazzard, and Jerome Madson helped to collect the cores and conducted preliminary microfossil analyses on the cores.
Copyright 2008 Elsevier B.V., All rights reserved.
- South Africa
- vegetation history