Paleoclimate Information from Speleothems: The Present as a Guide to the Past

Speleothems are the secondary mineral deposits formed in caves. The most common type of speleothems are the calcium carbonate (CaCO3) stalactites, stalagmites, and flowstones which are a ubiquitous feature of caves worldwide. Variations in the18O/16O and 13C/12C ratios in calcite speleothems can provide important information about terrestrial paleoclimate, if deposition occurred under equilibrium conditions because (i) they contain a well-defined internal stratigraphy, (ii) their absolute age of deposition can be determined accurately with high precision through mass spectrometric U-series disequilibrium geochronology (Edwards et al., 1987; Li et al., 1989), (iii) variations in their internal chemical and isotopic composition are determined by the environmental conditions at the time of deposition, (iv) they may trap surface-derived dust, pollen, and organic acids as the calcite layers are sequentially deposited and (v) they tend to behave as geochemically closed systems (see e.g. Schwarcz, 1986; Gascoyne, 1992).