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A Holocene sequence of vegetation change at Lake Eteza, coastal KwaZulu-Natal, South Africa |
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| Authors: | Frank H Neumann Louis Scott L van As |
| Institution: | a Bernard Price Institute for Palaeontology, University of the Witwatersrand, Private Bag 3, Wits 2050 (Johannesburg), South Africa b Department of Plant Sciences, University of the Free State, P.O. Box 339, Bloemfontein 9300, South Africa c Steinmann-Institut für Geologie, Mineralogie und Paläontologie, Nussallee 8, 53115 Bonn, Germany d Department of Anthropology and Center for Archaeological Studies, Texas State University—San Marcos, San Marcos, Texas 78666, USA e School of Geography, Archaeology and Environmental Studies, University of the Witwatersrand, Johannesburg 2050, South Africa f Department of Zoology and Entomology, University of the Free State, P.O. Box 339, Bloemfontein 9300, South Africa |
| Abstract: | Palynological and sedimentological data from a core extracted from Lake Eteza shed new light on the Holocene vegetation and climate history in KwaZulu-Natal and can be linked to regional and global climate change. A 2072 cm core with nineteen radiocarbon dates and chronological extrapolation to the bottom of the sequence suggests that sedimentation started ca. 10 200 cal yrs BP. Between ca. 10 200 and 6800 cal yrs BP pollen indicators point to a change from intermediately humid conditions to comparatively drier grassy environments. This is in good agreement with Sea Surface Temperature (SST) fluctuations from a core in the Mozambique Channel which influence precipitation in coastal KwaZulu-Natal, and the beginning of the Holocene Thermal Maximum ca. 10 500 cal yrs BP. The lower section of the core corresponds to gradually increasing Holocene sea levels along the coast and development of freshwater or estuarine conditions at Lake Eteza. The middle Holocene (ca. 6800-3600 cal yrs BP), when the sea level reached its highest stand and SST peak, indicate humid climatic conditions that favoured an increase of forest trees, e.g. Podocarpus, and undergrowth plants like Issoglossa. As a consequence of higher precipitation and increase of the water table, conditions were favourable for the spread of mangrove, swamp and possibly riverine forest. During the late Holocene after ca. 3600 cal yrs BP a decrease of Podocarpus and other trees as well as an increase of Chenopodiaceae/Amaranthaceae, grasses and Phoenix coincide with a return to lower sea levels and drier conditions. The decrease of all trees including Phoenix at ca. 700 cal yrs BP, accompanied by rapid sedimentation rates, possibly reflect forest clearing and upland erosion induced by activities of Iron Age settlers. A dry period at the globally recognized onset of the Little Ice Age might have contributed to these changes. Late Iron Age settlers have probably already introduced Zea mays, which was detected in the profile since ca. 210 BP. The appearance of neophytes like Pinus, Casuarina and pollen of Ambrosia-type in the youngest sediments indicates increased disturbance of European settlements and land use since ca. 100 cal yrs BP. |
| Keywords: | forest reconstruction vegetation history Southern Hemisphere African coast human impact |
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