Multi-proxy stable isotopic evidence for Holocene climate change in Western Ireland.
by
Martin Collett
Department of Earth Science, University of Liverpool, UK.
Coauthors: Dr. Jim Marshall (Department of Earth Science, University of Liverpool, UK.), Dr. Jan Bloemendal (Department of Geography, University of Liverpool, UK.), Dr. Jonathan Holmes (Environmental Change Research Centre, University College London, UK.), Dr. Karen Molloy (Palaeoenvironmental Research Unit, National University of Ireland, Galway.)

Despite the growth of Irish Holocene palaeoenvironmental archives, studies of lacustrine sedimentary records report extremely variable and often contradictory palaeoclimatic conditions. Questions remain on the palaeoenvironmental conditions in Western Ireland, and the sequence of events leading to present day conditions. High-resolution multi-proxy studies can provide systematic data that can help resolve long and short-term environmental change. The current study aims to synthesise high-resolution multi-proxy palaeoclimatic data and contribute to an enhanced understanding and refinement of the direction, magnitude and variability of Holocene regional climate in Western Ireland.

A comprehensive and well-studied suite of environmental proxies has been systematically evaluated from a single core from the lacustrine sediments of Mooghaun Lough, County Clare, Western Ireland. By combining isotopic evidence from authigenic carbonate sediment, benthic and planktic ostracods, Chara, and gastropods with palaeoecological and mineral magnetic data it has been possible to decouple the effects of natural and anthropogenic environmental change.

The wide variety of proxies analysed facilitates a breakdown of the spatial and temporal geochemical composition of the lake into the individual component habitats in which each species lives. Comparison of isotopic and trace-element signatures of planktic and benthic species enables the evaluation of lake stratification throughout the Holocene. Furthermore, comparison of isotopic and trace element signatures of ostracod species with season-specific calcification periods (e.g. Candona candida and Limnocythere inopinata) enables the evaluation of the direction and magnitude of changing Holocene seasonality. On the longer, millennial, time scales, the isotopic records generally display a relatively strong degree of coherence, however, over shorter time scales some divergence of the records occurs. Such divergence is attributed to either one or a combination of the following: habitat micro effects; biological vital effects (i.e. metabolic effects); calcification during periods of variable lake stratification, and/or differential seasonal calcification.

The dataset provides a more thorough understanding of the geochemical makeup and systematics of Mooghaun Lough, which has aided in the synthesis of a less-ambiguous Holocene palaeoenvironmental reconstruction. Coupled isotopic and trace element signatures enable the reconstruction of Holocene palaeosalinities and palaeotemperatures, whilst combined pollen and mineral magnetic data facilitate the reconstruction of Holocene local land use and catchment stability.

Date received: April 29, 2001

Copyright © 2001 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # cahi-50.