BIRM-166’s Interstadial Witness
Archived: 27 September 2026
Around 30,597 BCE, Ireland was in Marine Isotope Stage 3, an unstable phase of the Late Pleistocene, rather than a datable year. At Derryvree, County Fermanagh, organic freshwater sediments between glacial tills, radiocarbon dated as BIRM-166, record a cold, ice-free interval. Pollen, plants, mosses and beetles indicate shallow water, wet margins and sparse, treeless tundra-like vegetation. Cave faunas demonstrate open-country ecosystems supporting herbivores, predators and scavengers, although remains span different periods. A possibly cut-marked reindeer bone suggests brief human presence, not settlement. Lower sea levels altered routes, while shifting ice and terrain restricted movement. Evidence reveals ecosystems amid changing ice.