ISOTOPIC RECORD FROM FOSSIL TOOTH ENAMEL: SERIAL SAMPLING TECHNIQUES

Vertebrate teeth provide a high fidelity carbon and oxygen isotope record useful in resolving a variety of paleobiological and paleoclimatological questions. Methods for extracting isotopic data from tooth enamel include two single sampling strategies (spot and bulk) and three serial sampling strategies (block, line, and point). Depending upon the specific research question, the selection of teeth and analytical technique become critical. Conical teeth and those with multi-month growth intervals will provide strongly biased results for single sampling and block serial sampling strategies. Teeth with thick enamel or irregular growth patterns may provide partially homogenized results in large sample techniques. Line sampling provides resolution of approximately 2 weeks depending upon individual tooth growth rate. Point sampling techniques offer high resolution but do collect multiple sources of oxygen. As an example, data from modern and fossil archosaur teeth indicate 1 to 7 per mil isotopic variability using a line sampling technique. Spot or bulk samples from these same teeth can incorporate up to an 80% error in estimating the annual isotopic mean.