DATING RECENT PEAT ACCUMULATION IN EUROPEAN OMBROTROPHIC BOGS

This study compares age estimates of recent peat deposits in 10 European ombrotrophic (precipitation-fed) bogs produced using the C-14 bomb peak, Pb-210, Cs-137, spheroidal carbonaceous particles (SCPs), and pollen. At 3 sites, the results of the different dating methods agree well. In 5 cores, there is a clear discrepancy between the C-14 bomb peak and Pb-210 age estimates. In the upper layers of the profiles, the age estimates of C-14 and Pb-210 are in agreement. However, with increasing depth, the difference between the age estimates appears to become progressively greater. The evidence from the sites featured in the study suggests that, provided aboveground plant material (seeds, leaves) is selected for dating, the C-14 bomb peak is a reliable dating method, and is not significantly affected by the incorporation of old carbon with low C-14 content originating from sources including air pollution deposition or methane produced by peat decomposition. Pb-210 age estimates that are too old may be explained by the enrichment of Pb-210 activity in the surface layers of peat resulting from a hypothesized mechanism where rapidly infilling hollows, rich in binding sites, may scavenge Pb-210 associated with dissolved organic matter passing through the hollow, as part of the surface drainage network. Until further research identifies and resolves the cause of the inaccuracy in Pb-210 dating, age estimates of peat samples based only on Pb-210 should be used with caution.