LATE-GLACIAL VEGETATION AND ENVIRONMENT IN IRELAND - 1ST RESULTS FROM 4 WESTERN SITES

First results of investigations that include pollen and chemical analyses of lateglacial lake sediments from four sites in western Ireland are presented, and the evidence for environmental change from these and previously published studies is reviewed. Fresh evidence is presented for a period with a cold. arid, continental-type climate immediately after deglaciation. This period is informally defined as the Pre-interstadial. It is represented by a Pinus-Artemisia-Gramineae pollen assemblage, with a high proportion of long-distance transported pollen, recorded in highly minerogenic sediments immediately overlying outwash gravels and sands. The interval between this and the Younger Dryas Stadial, informally defined as the Lateglacial Interstadial, is characterised in the early part by maximum tall shrub development, consisting mainly of Juniperus; tall shrub vegetation is subsequently replaced by Gramineae and Cyperaceae-dominated open vegetation at many sites. It is argued that the Lateglacial Interstadial is characterised by a number of climatic oscillations, the most severe and sustained being responsible for this general shift in favour of herbaceous taxa at mid-Interstadial (ca. 12 ka BP). Prior to the onset of die Younger Dryas deterioration, a modest expansion of Juniperus at several sites and Betula at some sites suggests a period of ameliorating climate. The severity of climatic conditions during the Younger Dryas Stadial is well expressed in the pollen, lithological and chemical data. There is some evidence to suggest that vegetation development in terrestrial environments at the transition to the Holocene lagged behind developments in aquatic habitats and the thermal environment generally.