Radiocarbon dating of historic mudflat sediments at Airth in the inner Forth estuary and the impact on the estuary of nineteenth century agricultural improvements

ABSTRACT The results of sediment-stratigraphic, diatom and pollen analyses, and AMS 14C dating of salt marsh sediments at Higgin’s Neuk, Airth in the inner Forth estuary in central Scotland are reported. Engineering borehole records of abundant peat within mudflat sediments encouraged work to establish rates of mudflat accretion over the last several centuries. However, six 14C assays on peat closely associated with buried archaeological structures of likely eighteenth century age record later prehistoric and early historic age-estimates. The assays are thought to be correct. The peat is not in situ. It probably originated from the well-documented, extensive late eighteenth and early nineteenth century clearance of raised mosses in the River Forth for agriculture. The sediment-stratigraphic evidence is important because it confirms the scale of the impacts of peat clearance on the inner estuary derived from contemporary documents. The peat may act as a marker horizon in mudflat and salt marsh sediments from which rates of post-eighteenth century mudflat accretion can be derived. At Higgin’s Neuk these were probably very high, given uncertainties in dating controls, around 0.8 cm/yr (1.2 yrs/cm) for the last ca. 150 years, a finding which accords with other studies around the North Sea.