Clumped isotopes analyses in modern land snail shells are reported and used to interpret shell oxygen isotopes within the context of terrestrial paleo-climatology. Carbonate clumped isotopes thermometry is a new technique for estimating the temperature of formation of carbonate minerals. It is most powerful as an indicator of environmental parameters in combination with δ18O, allowing the partitioning of the δ18O signal into its temperature and water components. Results indicate that snail shell calcification temperatures are typically higher than either the mean annual or the snail activity season ambient temperatures. Small inter- and intra-snail variability suggests that shell aragonite forms at isotopic equilibrium so that the derived temperatures are an eco-physiological parameter reflecting snail body temperature at the time of calcification. We attribute these higher body temperatures to snail eco-physiological adaptations through shell color, morphology, and behavior. In combination with shell oxygen isotope composition, these temperatures allow us to calculate snail body water composition, which is in turn interpreted as a paleo-hydrological indicator, reflecting isotopic composition of local precipitation modified by local evaporation.
Bibliographical noteFunding Information:
We thank Eric Lazo-Wasem and Lourdes Rojas from the Yale Peabody Museum of Natural History for sharing samples and Adam Baldinger from the Harvard University Museum of Comparative Zoology for assistance in snail species identification. We thank Sharon Reinhart, Dominic Colosi and the Earth System Center for Stable Isotope Studies of the Yale Institute for Biospheric Studies. We thank K. Huntington, M. Daëron and C. Yapp for their thorough review and helpful comments. The work was supported by the National Science Foundation Grant NSF-EAR-0842482 to H.P.A.