Examining the nature and timing of deglaciation in Britain: new evidence from the Arenigs, Brecon Beacons and South Wales Valleys

New ¹⁰Be exposure ages from the Arenig mountains, North Wales have been obtained to complement ³⁶Cl ages and help constrain the timing of deglaciation in NE Wales. The last phase of cirque glaciation is dated to the Younger Dryas and this is consistent with previous assumptions of deglaciation in Wales. In South Wales, in the Brecon Beacons, the last cirque glaciers were higher than those in the north, which is consistent with increasing cirque altitude with lower latitude. Radiocarbon dating from bogs inside of moraines in these cirques also supports a Younger Dryas age for the last phase of glaciation. However, further south in the South Wales Valleys, the last former cirque glaciers were at some of the lowest altitudes in Wales. The glaciers occupied cirques that are lower than in the nearby Brecon Beacons and these cirques represent an anomalous population of low-lying cirques compared with the rest of Wales. Reasons for this are either because 1) wetter conditions existed the South Wales Valleys than the rest of Wales leading to lower cirque glaciation during the Younger or 2) the last cirque glaciers were present and formed moraines prior to the Younger Dryas, possibly when the Welsh Ice cap covered Wales north of the Brecon Beacon watershed divide. Ongoing work will apply ¹⁰Be exposure dating from moraine boulders and ¹⁴C dating from bogs inside of moraines in the cirques of the Brecon Beacons and South Wales Valleys to test these hypotheses further.