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Reconstruction of environmental and climate changes at Braamhoek wetland, eastern escarpment South Africa, during the last 16 000 years with emphasis on the Pleistocene-Holocene transition
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
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2009 (English)In: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, Vol. 271, 270-258 p.Article in journal (Refereed) Published
Abstract [en]

A paleo-environmental record covering the last 16 ka (16 000 cal yrs BP) from the eastern areas of the summer rainfall region in South Africa is presented. This area is until now sparsely investigated due to the lack of well preserved natural archives. For this study, we used a peat section from a wetland situated close to the Drakensberg escarpment, where the high annual rainfall amounts supported a continuous peat accumulation since c. 16 ka. One peat core was analysed in terms of fossil pollen composition, carbon and nitrogen content, isotope composition (δ13C, δ15N) and microscopic charcoal concentration. The greatest degree of temporal resolution was achieved from the late Pleistocene and early Holocene section, where proxy-records indicate relatively dry conditions between ca. 16-13.7 ka, 12.8-10.5 ka, 9.5-8.2 ka, and wet conditions between c. 13.7-12.8 ka and 10.5-9.5 ka. A weak moisture signal is also evident at c. 8.2-7.5 ka. The late Pleistocene to early Holocene period was relatively cool, while conditions became generally warmer after 11-8 ka. The interpretation of the mid- and late-Holocene sequence is limited due to a slow accumulation and low sample resolution, but the available data suggest relatively dry conditions until c. 1.5 ka, followed by more humid conditions until c. 0.5 ka. We suggest that the millennial scale variability within the record can be attributed to shifts in the circulation systems dominating the region, i.e. the latitudinal movements of the inter-tropical convergence zone (ITCZ) and the dynamics of the mid-latitude low pressure belts.

Place, publisher, year, edition, pages
Elsevier , 2009. Vol. 271, 270-258 p.
Keyword [en]
paleoclimate, South Africa, palynology, Holocene
URN: urn:nbn:se:su:diva-24705DOI: doi:10.1016/j.palaeo.2008.10.018ISI: 000263013200005OAI: diva2:198147
Available from: 2011-01-17 Created: 2008-02-15 Last updated: 2011-01-17Bibliographically approved
In thesis
1. Late Quaternary climate and environmental change in the summer rainfall region of South Africa: A study using trees and wetland peat cores as natural archives
Open this publication in new window or tab >>Late Quaternary climate and environmental change in the summer rainfall region of South Africa: A study using trees and wetland peat cores as natural archives
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis contributes with information on past climate and environmental changes in South Africa’s summer rainfall region. The study is based on multi-proxy analyses on wetland peat cores and analyses of stable isotope composition (δ13C, δ18O) and wood anatomy in cross sections from subtropical trees (Breonadia salicina). The peat archive covers the last 16 ka (ka; 1000 cal yrs BP) and was analysed in terms of fossil pollen, charcoal, diatoms, phytoliths and stable isotope composition. The peat record infers relatively wet climate conditions at c. 13.7-12.8 ka, 10.5-9.5 ka and 2.5-0.5 ka, and drier conditions at c. 16-13.7 ka, 12.8-10.5 ka and during mid-Holocene. Tentatively, cooler late Pleistocene temperatures shifted towards warmer after c. 9.5 ka. The study of B. salicina demonstrates the paleo-climatic value of subtropical trees despite absence of annual tree rings. An age model was constructed from radiocarbon dating and calibration by wiggle matching. δ13C in B. salicina shows a co-variation with annual rainfall amounts, suggesting that it may be considered a regional climate-proxy. δ18O is mainly influenced by local factors, but acts as a useful complement when interpreting δ13C. Together with other regional, high-resolution records, the 600 year long δ13C-record suggests dry climate conditions in northern South Africa during the 1700s and mid-1500s AD. Inferred climate and environmental changes are suggested being a response to expansion, contraction and latitudinal shifts of the tropical, subtropical and mid-latitude atmospheric circulation cells. An observed inverse humidity pattern between southern and equatorial Africa suggests that ENSO-like teleconnections may be a possible forcing mechanism in a decadal to centennial time perspective.

Place, publisher, year, edition, pages
Stockholm: Institutionen för naturgeografi och kvartärgeologi, 2008. 108 p.
Dissertations from the Department of Physical Geography and Quaternary Geology, ISSN 1653-7211 ; 11
paleoclimate, Late Quaternary, pollen, stable isotopes, diatoms, phytoliths, dendroclimatology, South Africa
National Category
Physical Geography
Research subject
Physical Geography
urn:nbn:se:su:diva-7375 (URN)978-91-7155-581-6 (ISBN)
Public defence
2008-03-17, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 8 A, Stockholm, 13:00
Available from: 2008-02-25 Created: 2008-02-15Bibliographically approved

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Norström, Elin
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