Late Pleistocene mountain glacier response to North Atlantic climate change in South West Ireland

There is clear geomorphological and dating evidence to suggest that the mountains of western Ireland were sensitive to North Atlantic cooling episodes throughout the Lateglacial period. In the mountains of the Macgillycuddy’s Reeks of southwest Ireland we have reconstructed the dimensions and former Equilibrium Line Altitudes (ELAs) of two sets of palaeoglaciers which readvanced following the end of the Last Glacial maximum. The most extensive glacier readvance, the Outer Local Glaciation, produced valley glaciers covering an area of around 11.2 km2. Cosmogenic nuclide exposure ages from two boulders on the Hags Teeth moraine marking this event provide ages of 17.1 ± 1.3 and 22.9 ± 1.5 ka. The difference in the two ages probably reflects cosmogenic nuclide inheritance in the sampled boulders. The less extensive readvance, the Inner Local Glaciation, formed cirque glaciers covering an area of 1.56 km2. Cosmogenic nuclide exposure ages from two boulders on moraines marking this event provide ages of 15.1 ± 1.0 ka and 14.9 ± 1.8 ka. We hypothesise that these ages either represent a glacial response to cooling during the Lateglacial Interstadial (during the Older Dryas cold phase) or reflect inherited boulder ages from a paraglacial episode of enhanced rockfall following glacier recession of valley glaciers, and the moraines are Younger Dryas in age. These data provide the first examples in the British Isles where two Lateglacial advances are reconstructed and indicate the dynamic nature of glaciation in this area.