COASTAL PEATS FROM NORTHWEST IRELAND - IMPLICATIONS FOR LATE-HOLOCENERELATIVE SEA-LEVEL CHANGE AND SHORELINE EVOLUTION

Peat and organic rich sediments at coastal sites in extreme northwest Ireland have accumulated in a wide variety of environments, often stro ngly influenced by late Holocene changes in relative sea level and by geomorphic processes. A deep peat sequence on the coast of Aranmore Is land accumulated initially in a lake and subsequently in a freshwater marsh environment. The long pollen record serves as a template for reg ional events. It extends over much of the Holocene and shows relativel y high levels of Pinus pollen up to just before the disappearance of t his taxon at c. 3600 BP. Coastal peat occurrences elsewhere are much t hinner and have accumulated over shorter periods, they contain further evidence to show that coastal areas were well-wooded compared with to day, and that Pinus was an important woodland component prior to c. 40 00 BP. At sites in Gweebarra Bay intertidal peats record the closure o f small estuaries by geomorphological events during the past 5000 year s. Coastal sites at Ballyness, Clonmass. and Trawenagh display regress ive stratigraphies- minerogenic marine sediments are overlain by silty peats capped by highly organic freshwater peats. Basal radiocarbon da tes range from 4500 to 3300 BP. The silty peats are interpreted as hav ing formed in salt-marsh environments and contain distinctive pollen s pectra, marked by high levels of Pinus and Compositae Liguliflorae pol len. The data suggest that relative sea level attained levels close to that of today by the mid-Holocene in this region. The pattern of rela tive sea-level change agrees well with that predicted by geophysical m odelling.