109-6 Ca Isotopes in Tooth Enamel: Physiology, Trophic Level and Environmental Reconstruction

Session: Working Up an Apatite: Teeth as Paleo -Ecological and -Climatological Archives (Posters)

Poster Booth No.: 219

Presenting Author:

Lauren Gilmore

Authors:

Gilmore, Lauren D¹, Gili, Stefania², Hagge, Perrin³, Akhtar, Alliya A⁴, Hoppe, Kathryn A.⁵, Niespolo, Elizabeth⁶, Higgins, John A ⁷

(1) Geosciences, Princeton University, Princeton, NJ, USA, (2) Geosciences, Princeton University, Princeton, NJ, USA, (3) Geosciences, Princeton University, Princeton, NJ, USA; Nicholas School of the Environment, Duke University, Durham, North Carolina, USA, (4) Geosciences, Princeton University, Princeton, NJ, USA, (5) Green River College, Auburn, WA, USA, (6) Geosciences, Princeton University, Princeton, NJ, USA, (7) Geosciences, Princeton University, Princeton, NJ, USA,

Abstract:

Calcium (Ca) isotopes in tooth enamel have been interpreted as proxies for diet, trophic level, nursing practices, and ecosystem structures—particularly when paired with δ¹³C—in terrestrial systems. However, questions remain about how and why Ca fractionates in ecological and biological systems. The American bison (Bison bison) is a model organism for investigating environmental and physiological controls on Ca isotopes (δ^44/40Ca) in enamel, owing to its broad habitat range and the opportunity to sample associated Ca reservoirs across entire ecosystems. Improving our understanding of Ca isotopes in modern bison enamel will aid interpretations of Ca isotope signals in other ungulate fossil assemblages.We aim to refine our understanding of Ca source pathways and isotope incorporation into enamel by integrating enamel isotope data with environmental samples—including water, soil, and vegetation. To this end, we analyzed Ca isotopes in modern bison teeth and corresponding environmental samples from nine localities across the United States. We find that Ca fractionates from surface water, to the exchangeable soil reservoir, to vegetation, to enamel. Lighter Ca is preferentially taken up with each trophic level, resulting in progressively lighter δ^44/40Ca values, though the vegetation and the exchangeable soil reservoir have considerable overlap. Modern bison tooth enamel exhibits total variability of ~1.5‰ in δ^44/40Ca across all nine sites; a subset of four sites show greater (~1.2‰) variability. This variability may be partially influenced by local differences in %C₄ biomass– indicated by a negative correlation between δ^44/40Ca and δ¹³C values. However, the small differences in δ^44/40Ca values between C₃ and C₄ whole plant and leaf samples from these four sites are insufficient to fully explain the variability seen in the enamel. This suggests other process(es)–potentially related to the metabolism or soil interactions–could account for the increased variability. 

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-6927

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