As interest grows in deciphering the factors that influence the Earth's climate, researchers have developed several proxies useful for reconstructing ancient environmental conditions. One of the most promising tools for reconstructing short-term (seasonal to annual) environmental fluctuations is isotopic analysis of vertebrate fossils. Analyses of fossil bison hold particular promise for such research. However, the precision of paleoenvironmental reconstructions based on analyses of fossil bison is currently limited because: (1) the rate of enamel biomineralization within bison teeth has not been studied in detail, and (2) the precise relationship between the d18O and d13C values of modern bison and local environmental conditions has not been precisely quantified. The purpose of this project is to quantify how precisely isotopic analyses of bison can be used to reconstruct paleoenvionemtal conditions. The first part of this study will document the patterns of biomineralization and isotope variations preserved within bison tooth enamel in order to develop an optimal sampling strategy. The second part of this study will quantify how well the d18O and d13C values of modern Great Plains bison correlate with environmental changes including: average temperature, seasonal temperature range, precipitation, relative humidity, and grassland composition (i.e., C3/C4 ratio). This study will thus quantify how precisely analyses of the d18O and d13C values of bison can be used to reconstruct annual and seaonal variations in local environments. It will produce a map of the isotope gradients in modern bison, which will serve as a baseline for interpreting the isotope signals preserved in fossil bison as well as other herbivores. This study will thus greatly increase the precision and accuracy of paleoclimatic and paleovegetation reconstruction based on isotope analyses of fossil herbivores.
