BIRM-166’s Organic Interlude
The closest important chronological anchor is BIRM-166, a radiocarbon determination from organic sediments found at Derryvree, near Maguiresbridge in County Fermanagh. Roadworks in 1969 cut through a drumlin and exposed freshwater silts and fine sands trapped between two distinct sheets of glacial till. The original result was 30,500 radiocarbon years before present, with a substantial laboratory uncertainty. “Before present” conventionally means before 1950, not before the present calendar year. Because atmospheric carbon-14 has varied through time, such results must be calibrated rather than read as calendar dates.