USING OXYGEN ISOTOPIC ANALYSES OF BISON TOOTH ENAMEL AS A PROXY FOR RECONSTRUCTING THE OXYGEN ISOTOPIC RATIOS OF SURFACE WATER
I analyzed the oxygen isotopic ratios of carbonate from bulk samples of tooth enamel from modern bison. Teeth were collected from 11 sites located in California, Montana, Oklahoma, Nebraska, North Dakota, South Dakota, Utah, and Wyoming. I examined the variability of oxygen isotopes within and among different populations and compared the average oxygen isotopic values of each population to previous measurements of the average values of local surface waters. I found that the oxygen isotopic values of individual bison within a given population vary less than 5; average standard deviations for a population was 1.2 (1σ). No significant differences in variability were found among bison populations from different environments. Although individuals within a population displayed a range of values, the average oxygen isotopic values of bison enamel showed a good correlation with the values of local surface waters (R2 > 0.8, p < .05). Therefore, analyzes of the average oxygen isotopic values of bison tooth enamel should serve as a good proxy for reconstructing the oxygen isotope ratios of local surface waters.