Raised peat bogs are closely coupled to the atmosphere and oceans due to their ombrotrophic state. They record variations within the peat layers and accumulate at a high rate (~5/10 years cm-1) offering reliable, high resolution palaeoenvironmental archives. Their archive records can be reconstructed using a range of techniques. In the past palaeoclimate reconstructions were commonly based on either biological or geochemical data. There are, however, problems such as preservation and mobility respectively associated with each of these techniques. Combining biological and geochemical tools can compensate for such weaknesses and help gain a more accurate picture of past palaeoclimate changes. However, few studies to date have embraced the advances of genuine multiproxy analyses.
The objective of our study conducted at the University of Aberdeen is to apply biological and geochemical proxies together to gain an improved understanding of past climate change. We aim to explore potential correlations between wet as well as dry indicators of either proxy type.
We are studying three different sites along the West coast of the British Isles with varying degrees of exposure to the North Atlantic. The first site, Tyndrain, is located in the Northwest of Wales in the Snowdonia National Park. The depth of the deposit is up to 4 m with the raised phase starting around 2.50 m. This depicts the change from minerotrophic (groundwater influence) to ombrotrophic (atmospheric influence only).
The other sites are Annaholty, a raised bog deposit in Clare, SW Ireland, and Raeburn Flow, a deposit on the Solway Firth, S Scotland.
For biological data we look at plant macrofossils, using the Quadrat & Leaf Count technique as well as Testate amoebae specimen counts. As geochemical proxies we investigate the distribution of lithogenic versus marine derived elements as well as anthropogenic elements. Chronologies are based on 14C and 210Pb dating.
The first results for Tyndrain show that the botanical and geochemical fen-bog transition are located at different depths in the profile. The geochemical transition is distinctively higher up. We can however, pick up a big shift in all proxies around ~2800 cal BP. This coincides well with a wetshift recognisable in numerous deposits all over the world.
As for the desired correlations, we have contradicting results. However, it is possible to see some matching peaks for the various proxies in terms of wetshifts and droughts throughout the profile. An important factor influencing the distribution of lithogenic elements and their interpretation is land use.
Our palaeoclimate reconstructions for the Tyndrain raised bog deposit show that analysing just one proxy may mask changes in bog surface wetness. However, combining biological and geochemical data can improve insight as well as raise more questions. It is therefore crucial to conduct more studies to determine consistent patterns.
Furthermore, one important denouement is that even within relatively short distances there can be high intrasite variability within peat bog ecosystems.
Anke Küttner, Dmitri Mauqouy, Tim Mighall, Eva Krupp, College of Physical Sciences, University of Aberdeen, Aberdeen, Scotland, UK.