Derryvree’s Fossil Bogbean
The difficulty begins with chronology. Radiocarbon determinations are not calendar dates: they measure the remaining carbon-14 in organic material and must be calibrated against changing atmospheric carbon levels. For periods more than 30,000 years ago, the resulting calendar ranges can be broad. The most relevant Irish reference point is the Derryvree freshwater deposit near Maguiresbridge in County Fermanagh. Organic silts and fine sands there produced a conventional radiocarbon age of 30,500 years BP, with a substantial uncertainty range. Modern calibration places such an age within a several-thousand-year calendar interval rather than at a single securely identifiable year.