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Karl Ljung

Karl Ljung

Lecturer

Karl Ljung

Late Holocene multi-proxy records of environmental change on the South Atlantic island Tristan da Cunha

Author

  • Karl Ljung
  • Svante Björck
  • Dan Hammarlund
  • Lena Barnekow

Summary, in English

Sediment stratigraphies from three sites, one lake, one overgrown lake, and an exposed section, on the island Tristan da Cunha in the temperate South Atlantic were analysed by means of pollen analysis, total carbon, nitrogen and sulphur content determination, magnetic susceptibility measurements and detailed radiocarbon dating. The aim of these studies was to reconstruct the late Holocene vegetation and climatic variations. The oldest sediment sequence extends back to 2300 cal. years BP. The vegetation was relatively stable up to the arrival of humans in the 17th century. The appearance of the introduced taxon Rumex acetosa/acetosella at c. 300 cal. years BP and a subsequent decline in forest cover on the lowland plain provide evidence of substantial human influence on the vegetation well before the establishment of the first permanent settlement in the 19th century. Before the first anthropogenic influence centennial-scale fluctuations in the proxy records are interpreted as reflections of local hydrological changes, probably caused by variations in precipitation. As inferred mainly from changing proportions of pollen derived from telmatic and terrestrial taxa and corresponding changes in the deposition of mineral matter by fluvial erosion, lake levels were low between c. 1450 and 1050 cal. years BP, and high between c. 1050 and 300 cal. years BP. These variations coincide with known climatic changes in Southern Africa and in the North Atlantic, suggesting that the inferred hydrological changes on Tristan da Cunha were related to large-scale variations in the general oceanic and atmospheric circulation in the Atlantic region.

Department/s

  • Quaternary Sciences

Publishing year

2006

Language

English

Pages

539-560

Publication/Series

Palaeogeography, Palaeoclimatology, Palaeoecology

Volume

241

Issue

3-4

Document type

Journal article

Publisher

Elsevier

Topic

  • Geology

Keywords

  • pollen analysis
  • Late Holocene
  • vegetation history
  • hydrological
  • changes
  • South Atlantic Ocean
  • Tristan da Cunha

Status

Published

ISBN/ISSN/Other

  • ISSN: 1872-616X