A LATE PLEISTOCENE INTERTIDAL BOULDER PAVEMENT FROM AN ISOSTATICALLY EMERGENT COAST, DUNDALK BAY, EASTERN IRELAND

Late Pleistocene sequences around Dundalk Bay, eastern Ireland, record glaciomarine sedimentation near the margin of a grounded ice lobe aro und 15 ka sp. A coastal exposure at Cooley Point consists of four majo r facies deposited outside this ice limit. (1) A basal mud facies depo sited from sediment plumes accumulated following the initial ice margi nal retreat inland. It contains a well-preserved Arctic microfauna dom inated by the foram Elphidium clavatum and the ostracod Roundstonia gl obulifera. (2) A flat to undulating boulder facies (pavement), mostly one clast thick, is found pressed into the mud and is characterized by bevelled and striated upper clast surfaces. Pavement attributes are a result of intertidal activity in a cold climate. The boulder source i s due to rafting by ice flees from glacigenic debris deposited during an ice advance. (3) Laminated sand facies drape the pavement and are a result of variable current activity. (4) The overlying gravel facies is separated from the sand facies by a marine erosion surface. The gra vel facies is subaqueous, channelized and is overlain by late glacial raised beach ridges. Locally the gravels have been deformed by ice pre ssure from partially floating ice flees. Facies changes record terrest rial submergence and provide evidence for changes in relative sea leve l during part of the last deglacial cycle. The boulder pavement and de formed gravel facies suggest that ice flees and sea ice effects may be more common within stratigraphies along emergent coasts than previous ly thought, though they have a low preservation potential. Extreme con ditions during the deglacial favoured opportunistic microfaunas during mud deposition. This event may be related to a major meltwater event within the Irish Sea Basin.