Resurrecting lost forests – speleothems inform on environmental changes in northern Scotland during MIS 5e
- 1Northumbria University, Faculty of Engineering and Environment, Department of Geography and Environmental Sciences, Newcastle upon Tyne, United Kingdom of Great Britain – England, Scotland, Wales (sebastian.breitenbach@northumbria.ac.uk)
- 2Department Chemie, Johannes Gutenberg-Universität Mainz, Duesbergweg 10-14, 55128 Mainz, Germany
- 3Department of Earth Sciences, University of Oxford, South Parks Road, OX1 3AN Oxford, UK
- 4Department of Biological and Geographical Sciences, University of Huddersfield, Queensgate, Huddersfield HD1 3DH, UK
- 5Grampian Speleological Group, Edinburgh
- 6University College London, Department Earth Sciences, Gower Street London WC1E 6BT, UK
Modern Northern Scotland is a largely barren landscape, with most of the natural temperate rainforest that covered the Atlantic side of Great Britain lost to active deforestation and overgrazing, mainly by sheep and deer (Shrubsole 2022). Pockets of relic temperate rainforest are reminders of the significant changes induced by the arrival of humans and their domestic animals. However, little is known about early Holocene and previous interglacial environmental conditions, and here we propose an unorthodox archive of natural vegetation cover of Scotland.
We present a new U-Th dated speleothem from the previous interglacial (MIS 5e/Ipswichian) and use stable oxygen and carbon isotope ratios, in tandem with lignin, a biopolymer with three monomers, to gain insight into last interglacial environmental conditions in Assynt, NW Scotland. The lignin monomer ratio provides information about relative changes between gymnosperm vs. angiosperm plant communities, and thus on changes in vegetation (e.g., from pine forest to moorland or grassland).
Flowstone TJL20080901 was found broken and recovered in 2008 from Rana Hole, a cave at 352 m above sea level overlain by heather moorland overlying blanket peat (Lawson & Dowswell 2022). Seven U-Th dates, analysed at Oxford University, show that this calcite flowstone was deposited between 127 and 119 ka BP during Marine Isotope Stage 5e, with an average growth rate between 20 and 40 μm/yr.
We suggest that speleothem δ13C indicates local infiltration and vegetation and soil composition, whereas δ18O reflects the history (source, temperature, seasonality) of the moisture feeding the cave stream from which the flowstone was precipitated. The lignin composition directly relates to local vegetation cover.
Our new multi-proxy record provides unique insights into environmental conditions in Assynt during MIS 5e, and the history of vegetation developing without human interference.
References
Homann et al. (2022) Linked fire activity and climate whiplash in California during the early Holocene. Nature Communications 13:7175
Lawson T. J. & Dowswell P. N. F. (2022) Caves of Assynt (3rd edition). Grampian Speleological Group. Edinburgh, 211 pages, ISBN 987-1-7397635-0-3
Shrubsole G. (2022) The lost rainforests of Britain. HarperCollins Publishers, 336 pages, ISBN 9780008527952
How to cite: Breitenbach, S. F. M., Homann, J., Couper, H., Fox, B. R. S., Kwiecien, O., Lawson, T. J., Hoffmann, T., Henderson, G. M., and Atkinson, T. C.: Resurrecting lost forests – speleothems inform on environmental changes in northern Scotland during MIS 5e, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-9362, https://doi.org/10.5194/egusphere-egu23-9362, 2023.
