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A multiproxy palaeolimnological investigation of Holocene environmental change, between c. 10 700 and 7200 years BP, at Holebudalen, southern Norway

Environmental Change Research Centre, University College London, Gower Street, London WC1E 6BT, UK, v.n.panizzo{at}ucl.ac.uk

V.J. Jones

Environmental Change Research Centre, University College London, Gower Street, London WC1E 6BT, UK

H.J.B. Birks

Environmental Change Research Centre, University College London, Gower Street, London WC1E 6BT, UK, Department of Biology, University of Bergen, Allégaten 41, N-5007 Bergen, Norway

J.F. Boyle

Department of Geography, The University of Liverpool, Roxby Building, Liverpool L69 7ZT, UK

S.J. Brooks

Department of Entomology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK

M.J. Leng

NERC Isotope Geosciences Laboratory, British Geological Survey, Keyworth, Nottingham NG12 5GG, UK, School of Geography, University of Nottingham, University Park, Nottingham NG7 2RD, UK

Geochemical analyses (x-ray fluorescence, ¹³C and C/N ratios) were used to reconstruct early Holocene environments (between 10685 and 7260 cal. yr BP) at a small lake near Holebudalen, southern Norway. Results show a period of increasing stability, with reduced catchment inwash (shown by titanium and potassium minerals), vegetation stabilization and increasing aquatic productivity (C/N ratios). However, periods of instability (loss on ignition (LOI) decrease) are also seen (most notably at c. 9060 cal. yr BP). Chironomid-inferred July temperature (CI-T) reconstructions show a cooling of c. 2°C (RMSEP = 1.0°C) between c. 8400 and 8000 cal. yr BP and so high-resolution (5 mm; c. 20 yr) diatom analyses were conducted between 8675 and 7830 cal. yr BP in order to further investigate this change. Between c. 8270 and 8000 cal. yr BP there were large reductions (> 50%) in the abundance of tychoplanktonic diatoms (eg, Aulacoseira species) and absolute increases in periphytic diatom communities (eg, Navicula pupula, Pinnularia mesolepta). The multiproxy analyses suggest a period of increased lake ice cover with associated reductions in turbulence during this time. Diatom flora changes are concomitant with a fall in percent LOI and increased catchment erosion at the site and other evidence of regional climatic perturbations in the early Holocene. Therefore, superimposed upon an early Holocene warming trend at Holebudalen, there are climatic perturbations, for example reflected between c. 8200 and 8000 cal. yr BP by diatom communities.

Key Words: Palaeolimnology • palaeoclimate • early Holocene • `8.2 ka event' • diatoms • isotopes • geochemistry • southern Norway.

The Holocene, Vol. 18, No. 5, 805-817 (2008)
DOI: 10.1177/0959683608089217


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