Quaternary Science Reviews 23 (2004) 901–918 Palaeo-climate reconstruction from stable isotope variations in speleothems: a review Frank McDermott* Department of Geology, University College Dublin, Belfield, Dublin 4, Ireland Received 30 April 2003; accepted 13 June 2003 Abstract Speleothems are now regarded as valuable archives of climatic conditions on the continents, offering a number of advantages relative to other continental climate proxy recorders such as lake sediments and peat cores. They are ideal materials for precise U-series dating, yielding ages in calendar years, thereby circumventing the radiocarbon calibration problems associated with most other continental records. Stable isotope studies in speleothems have shifted away from attempting to provide palaeo-temperature reconstructions to the attainable goal of providing precise estimates for the timing and duration of major O isotope-defined climatic events characterised by high signal to noise ratios (e.g. glacial/interglacial transitions, Dansgaard–Oeschger oscillations, the ‘8200- year’ event). Unlike the marine records, speleothem data sets are not ‘tuned’, and their independent chronology offers opportunities to critically assess leads and lags in the climate system, that in turn can provide important insights into forcing and feedback mechanisms. Improved procedures for the extraction and measurement of stable isotope ratios in fluid inclusions trapped in speleothems are likely to provide, in the near future, a much enhanced basis for the quantitative interpretation of O isotope ratios in speleothem calcite. The latter developments open up once again the tantalising prospect of palaeo-temperature estimates, but more importantly perhaps, provide a direct test for a new generation of general circulation models whose hydrological cycles will incorporate the ‘water isotopes’. The literature is reviewed briefly to provide for the reader a sense of the current state-of-the-art, and to provide some pointers for future research directions. r 2004 Elsevier Ltd. All rights reserved. 1. Introduction Increasingly there is a need for well-dated high- resolution palaeo-climate records from continental settings to test and validate general circulation models (GCMs) at a higher spatial resolution, and to investigate possible leads and lags between different components of the climate system. Speleothems are multi-proxy palaeo- climate archives with the potential to provide such data. In carefully chosen sites they can record key aspects of climate variability such as mean annual temperature, rainfall variability, atmospheric circulation changes and vegetation response in a variety of measurable para- meters that include stable isotope ratios, inter-annual thickness variations of growth laminae, growth-rate changes, variations in trace element ratios, organic acid contents and the nature of trapped pollen grains. This review focuses on the use of stable isotopes in speleothems as palaeo-climatic indicators, and the emphasis is on developments and data sets that have been reported since previous reviews of the subject (Schwarcz, 1986; Gascoyne, 1992). The focus is primar- ily on oxygen isotopes, but carbon isotopes are included whenever they have contributed significantly to palaeo- climatic interpretations. Several unresolved issues re- main, but recently there have been important insights into the interactions between component parts of the system (e.g. marine sources, isotopic evolution in the hydrological system and isotopic effects during infiltra- tion through the unsaturated zone) that now underpin the interpretation of O isotopes in speleothems. Systematic studies of stable isotopes in speleothems commenced more than three decades ago (Hendy and Wilson, 1968; Thompson et al., 1974), but progress was hampered by the need for large samples (ca 10 g) for alpha-spectrometric U-series dating. The development of thermal ionisation mass-spectrometry (TIMS) tech- niques to measure U-series isotope ratios rejuvenated the subject (Edwards et al., 1988; Li et al., 1989). TIMS ARTICLE IN PRESS *Tel.: +353-1-706-2328; fax: +353-1-283-7733. E-mail address: frank.mcdermott@ucd.ie (F. McDermott). 0277-3791/$-see front matter r 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.quascirev.2003.06.021