SPATIAL AND TEMPORAL BIASES IN THE OXYGEN ISOTOPE SYSTEMATICS OF LAND SNAIL SHELLS

Land snails are a useful tool for studying paleoclimate because their shells are widely distributed and well-preserved in the Quaternary geological and archeological record. The oxygen isotope composition of land snail shells is commonly used to infer that of the local precipitation. Despite the empirical and theoretical research conducted so far, paleoclimate reconstructions using oxygen isotopes of snail shells remains challenging because (1) multiple atmospheric variables apart from precipitation impact the snail oxygen isotope budget; and (2) most published studies focus on few species with limited spatial and temporal coverage. The present research attempts to better understand the environmental meaning of land snail shell oxygen isotope systematics at a broad spatial and temporal scale by compiling and analyzing all published oxygen isotope data to date.

All published oxygen isotope data (n=1,909 datapoints), both from modern specimens and fossil shells, were compiled, standardized into a database and mapped on a global scale. Results show significant spatial biases with most research concentrated in the middle latitudes of the Northern Hemisphere. Snail oxygen isotope data is either limited or nonexistent in polar and tropical latitudes, and the Southern Hemisphere. Hence, available snail paleoenvironmental equations are merely based on data from middle latitudes, whereas extreme environments remain to be calibrated in detail. Finally, significant temporal biases were also documented in the published literature. 75% of published data on fossil land snails are dated to the Holocene (< 12,000 B.P.). The remaining published work includes isotopic data from late Pleistocene shells, and only one study has looked at Miocene land snails. In this presentation, we present spatial and temporal snail oxygen isotope trends at global scale and discuss possible environmental factors driving these patterns.