A mid to late Holocene chironomid-inferred temperature record from northwest Ireland

Abstract

This study provides the first mid to late Holocene chironomid-inferred temperature (C-IT) model for northwest Ireland, creating a valuable climatic context for the development of Irish society during the Neolithic and Bronze Age. Using a lake sediment core from an isolated catchment, Lough Meenachrinna in northwest Ireland, a multi-proxy approach of chironomid (Diptera: Chironomidae) subfossils, sediment geochemistry (δ13C, δ15N, C:N) and pollen analysis was used to assess any potential limnological impact from prehistoric human activity in the region and provide a quantitative summer temperature estimate for the late Mesolithic to the Iron Age (7050–2050 cal yr BP). The pollen record provides a local signal of human activity, showing low levels of pastoral indicators in the early Neolithic, with increased evidence for pastoral and arable farming during the Bronze Age and in particular the Iron Age. Human activity does not appear to be a driving force in lake system change at Lough Meenachrinna, as peaks in farming indicators (e.g. pastoral pollen indicators and increased δ15N values) were not concurrent with major fluctuations in the chironomid assemblages. C-ITs provide evidence of multiple fluctuations in temperature during the mid to late Holocene with a cold phase during the late Mesolithic (6800–5890 cal yr BP), followed by a warming period during the early Neolithic (5890–5570 cal yr BP). C-ITs reflect a relatively warm climate during the middle Neolithic, with a substantial warming from the late Neolithic into the early Bronze Age (4630–3810 cal yr BP). C-ITs show a general cooling trend from the Bronze Age into the Iron Age, with a cold event occurring at 3340 cal yr BP during the middle Bronze Age and second cold event at 2430 cal yr BP during the Iron Age. The multi-proxy approach has proven an effective strategy for untangling human and climate influences on the chironomid record, and is recommended as a methodological approach in future Holocene climatic reconstructions where prehistoric human influence is a factor.