The Birm-166 Horizon
Archived: 15 September 2026
Labelled 31,690 BCE, this period is better understood as a broad MIS 3 interval rather than a datable year. At Derryvree, County Fermanagh, the Birm-166 organic silts, enclosed between glacial tills, record cold freshwater wetlands, tundra vegetation, insects and unevenly advancing ice. Radiocarbon calibration places them broadly 36,900–31,700 years before present. Castlepook Cave, County Cork, yielded a diverse fauna including mammoth, reindeer, giant deer, hyena and lemmings, indicating open Ice-Age habitats and functioning food webs. A cut-marked reindeer bone may indicate an early human visit, but lacks secure context. Permanent settlement, social institutions and continuous occupation remain unproven in Ireland.