Freshwater Beneath the Drumlin
Modern BCE notation can imply a precision that the evidence does not possess. Radiocarbon laboratories report ages in years before present, conventionally before AD 1950, and such measurements must be calibrated because atmospheric carbon levels have varied over time. The Derryvree organic sediments produced the important conventional determination BIRM-166, 30,500 radiocarbon years BP, with a substantial uncertainty of +1,170 and −1,030 years. Modern calibration places that evidence broadly within roughly 36,900–31,700 calibrated years BP, rather than at one fixed calendar point.