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1 Geological Quarterly

1 2005

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Opportunities and constraints for reconstructing palaeoenvironments from stable light isotope ratios in fossils

Lee-Thorp J. A., Sponheimer M.

Geological Quarterly

2005

Vol. 49, No. 2

195-204

Stable light isotope ratios (13C/12C and 18O/16O) in fossilteeth provide key archives for understanding ecology of past faunal communities and the evolution of environments during the Plio-Pleistocene. Given the inevitable processes of diagenesis during fossilisation, the integrity of isotopic in formation and the degree of detailed in formation that can be extracted, remain important issues in all fossil studies. The most appropriate tests are those in trinsic to isotopic abundances in ecosystems. They are easier to develop for 13C/12C in savanna environments where large 13C/12C differences exist between C4 tropical grasses and C3 trees and shrubs. Validating 18O/16O ratios in fossil carbonate or phosphate is more difficult, but patterned variability, mainly tracking water-related behaviour, within modern faunal communities has been replicated in several fossil as semblages. The identification of seasonal variation in 13C/12C and 18O/16O along the growth axis of a tooth crown, also applicable in areas composed solely of C3 plants, fills a dual role as a test and for providing data on seasonal amplitude. The results of studies from low- and mid-latitude African sites suggest that isotopic variation in rain fall on short timescales and ecological differences amongst animals, dominate over smaller differences in 18O16O composition due to temperature.