A multiproxy (micro-XRF, pollen, chironomid and stable isotope) lake sediment record for the Lateglacial to Holocene transition from Thomastown Bog, Ireland

Abstract

A multiproxy Lateglacial environmental record is presented for a ca. 3.5-m lacustrine sequence retrieved from a small basin (ca. 2km2) at Thomastown Bog in County Meath, Ireland. Sediment chemistry, pollen, chironomid and stable isotope data provide a detailed picture of catchment and lake system changes from the end of the last glacial (GS-2a) to the early Holocene that correspond closely to existing local and regional models of climate change. Concomitant adjustments in independent proxy records are matched to the NGRIP oxygen isotope curve giving 12 event-episodes ranging from major climatic shifts to lower amplitude, centennial- to sub-centennial-scale adjustments, including a previously unreported regressive period of landscape instability during the north-west European 'Rammelbeek Phase'. The study emphasizes the potential of palaeoenvironmental reconstruction from sediment chemistry where the sediment mixing system reflects autochthonous versus allochthonous inputs. The investigation also indicates problems of interpreting isotope data derived from bulk marl due to possible lag effects controlling the delivery of soil and groundwater and multiple sources of HCO3- (aq.). These research findings have implications for core site selection and for studies attempting to use stable isotopes for correlation purposes.