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Rainfall Reconstruction Using Wood Charcoal from Two Archaeological Sites in South Africa

Published online by Cambridge University Press:  20 January 2017

ED C. February*
Affiliation:
Water Research Project, South African Museum, P.O. Box 61, Cape Town 8000, South Africa

Abstract

Major components of most southern African archaeological sites are stone, bone, and charcoal. A new technique for climate reconstruction utilizes measurements of vessel size and frequency in the cross-sectional xylem anatomy of archaeological charcoal from Collingham Shelter and Mhlwazini Cave in the Natal Drakensberg. Previous wood anatomical studies have shown that links exist among vessel diameter, vessel frequency and climate. The present study demonstrates that in relation to rainfall, vessel diameter in the species Protea caffra and Protea roupelliae correlated positively, whereas vessel frequency correlated negatively. In P. roupelliae, mean vessel diameter increases from 46 to 62 μm along a rainfall gradient ranging from 760 to 1665 mm. The significant correlations between rainfall and tangential vessel diameter for a charred sample of P. roupelliae suggest that such measures on an archaeological charcoal sample may be used to reconstruct rainfall patterns through time. Using nine assemblages of archaeological charcoal, generalized patterns of wetter and drier periods can be postulated. Comparison with contemporary values indicates that at 200 and 2400 yr B.P. the area near the archaeological sites was wetter than at present. A dry phase occurred between 1300 and 300 yr B.P. Values for the contemporary wood sample are the lowest observed, indicating that present conditions are much drier than those at any time within the last ca. 2000 yr. Dating resolution however, is insufficient to allow more-detailed interpretation of rainfall conditions over the past 2000 yr.

Type
Research Article
Copyright
University of Washington

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