Lateglacial and early Holocene palaeoenvironmental ‘events’ in Sluggan Bog, Northern Ireland: comparisons with the Greenland NGRIP GICC05 event stratigraphy

A multi-proxy Lateglacial environmental record is described from Sluggan Bog in County Antrim, Northern Ireland. Pollen, plant macrofossil, charcoal, sediment chemistry, stable isotope and sedimentological data provide a multi-faceted picture of local and regional environmental changes during the transition from the Last Cold Stage to the beginning of the present interglacial, and enable a series of distinctive palaeoenvironmental ‘events’ to be identified. A combination of radiometric and AMS radiocarbon dates on both humic and humin sediment fractions, and on charcoal fragments and plant macrofossils, provides one of the most closely-constrained radiocarbon timescales for any Lateglacial site in the British Isles. The evidence suggests that an initial period of warm conditions, beginning in the Sluggan record around 14.2 ka b2k (before AD 2000), and when open Salix-Betula woodland was locally present, was succeeded first by a heathland phase, then by a re-establishment of wood and scrub, before this was replaced during the later part of the Lateglacial (Woodgrange) Interstadial by species-rich grassland. In terms of timing, this sequence corresponds very closely to the GI-1e, GI-1d, GI-1c series of events in the Greenland NGRIP ice core. A short-lived Betula phase towards the end of the interstadial in the Sluggan sequence may reflect the short-lived climatic warming of GI-1a, although the radiocarbon age model suggests that it occurred prior to that event. There is a similar age discrepancy between the two sequences at the end of the interstadial with the onset of the Nahanagan (Younger Dryas) Stadial in Sluggan appearing to predate that in NGRIP by up to 200 yrs. By contrast, there is a very close correspondence between the date on the onset of the Holocene inferred from the pollen record in Sluggan (11.69 ka b2k) and the age of the Pleistocene–Holocene boundary (11.7 ka b2k) in NGRIP. While uncertainties remain over the climatic signals in the later interstadial, the evidence suggests that during the early and mid-interstadial and at the onset of the Holocene, Northern Ireland and Greenland appear to have been broadly phase-locked in their response to hemispherical climate change.