Oxygen Isotopes in Enamel Carbonate and their Ecological Significance

Stable carbon isotope analysis of fossil tooth enamel carbonate, and oxygen isotope analysis of bone or enamel phosphate, are established tools for palaeodietary and palaeoclimatic reconstruction, respectively. C/C ratios provide evidence of an animal’s diet and phosphate-based O/O values are used to establish palaeotemperature proxies. Recent studies of fossil enamel suggest that biogenic O/O signals are also retained in the carbonate compartment, despite assumptions thatO/O ratios from apatite carbonate are highly susceptible to exchange during fossilization. Here, we re-examine existing enamel carbonate O/O data from the rich fossil assemblages of Swartkrans and Equus Cave. We find patterns that can be interpreted in terms of drinking behaviour, diet, and physiology. In general, herbivores that drink little are more enriched than those that drink frequently, while carnivores are depleted compared with herbivores. Thus, we can increase our knowledge of the ecology of fossil taxa by coupling carbon and oxygen isotope ratio data. ? 1999 Academic Press