Derryvree’s Freshwater Window
This was the later part of Marine Isotope Stage 3, a long and climatically unstable interval of the Late Pleistocene. Ireland was approaching, but had not yet reached, the fullest expansion of the last British–Irish Ice Sheet. Modern reconstructions show that ice growth and retreat were uneven between regions rather than one simple island-wide advance. The principal maximum came later, broadly between about 27,000 and 23,000 calibrated years before present, although individual sectors behaved differently. Around the notional year in question, ground in some areas was still available to plants and animals, while glaciers and ice masses were expanding elsewhere.