Multidisciplinary investigations, including stable-isotope studies, of thick late-glacial sediments from Tory Hill, Co. Limerick, western Ireland

Multidisciplinary investigations of a 10-m-long, marl-rich, Late-glacial co re from Tory Hill, Co. Limerick, have enabled environmental change, includi ng estimates of summer temperature (ST), to be reconstructed for the Late-g lacial period, The sequence opens with fine, partially laminated silt/clay that has varve-like microstructure. A cold steppic environment from the fin al phase of the pleniglacial is represented here. It is estimated to span a lmost 2000 years (ca, 16.9-15 cal. ka B.P; ca. 14.6-12.7 ka B.P.). Substant ial development of woody vegetation is limited to the early part of the Lat e-glacial interstadial (cf. Bolling). This consists mainly of juniper and b irch, including tree birch (Betula pubescens), as well as herb-dominated co mmunities. These developments in vegetation and also the evidence from a va riety of other proxies, including stable-isotope records (delta(18)O and de lta(13)C), show that the thermal maximum was achieved early in the intersta dial bur ST probably did not exceeded 14 degrees C. Within this relatively warm period, the various biological, chemical and physical proxies suggest at least one substantial but short-lived climatic oscillation, The later pa rt of the Bolling/Allerod interstadial (after ca. 14 cal. ka B.P.; ca. 12 k a B.P.) began with a considerable and more or less sustained fall in temper ature. The low temperature regime was maintained until immediately before t he Younger Dryas when a modest but distinct amelioration is recorded by all proxies. This feature, referred to as a 'pre-Younger Dryas warming' (pYDw) and which is seen in land, ocean and Greenland ice-core records from the n ortheast Atlantic region, has not been previously highlighted in the litera ture. The Younger Dryas stadial, when ST may have fallen to ca. 6 degrees C , has a distinctive pollen assemblage characterised mainly by Gramineae, Th alictrum and Artemisia, but, for reasons not readily explainable, the early part of the stadial is not well defined in the stable-isotope record. As i n most records from the northeast Atlantic region, the transition to the Ho locene is sharp and clearly recorded. The importance of Juniperus in the Ir ish Late-glacial record, as an indicator of temperature change, is discusse d and also the possible role played by Ephedra and Secale species at Tory H ill. The apparent absence of temperature gradients within Ireland is commen ted on, and the evidence for much lower ST in Ireland compared with Great B ritain is discussed. (C) 1999 Elsevier Science B.V. All rights reserved.