Derryvree’s Permafrost Herbarium
In 1969, road works cut through the drumlin at Derryvree and revealed silts and fine sands containing organic material between two distinct sheets of glacial till. The sandwiching tills are crucial: they show that a freshwater environment existed at this spot between phases of glacier activity. A conventional radiocarbon determination from the organic deposit was 30,500 radiocarbon years BP, with a substantial uncertainty of +1,170 and −1,030 years. It is a measurement of an ancient sample, not a timestamp for a single episode.