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Triple oxygen isotope distribution in modern mammal teeth and potential geologic applications
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  • Sophie Lehmann,
  • Naomi Levin,
  • Benjamin Passey,
  • Huanting Hu,
  • Thure Cerling,
  • Joshua Miller,
  • Laura Arppe,
  • Emily Beverly,
  • Kathryn Hoppe,
  • Julie Luyt,
  • Judith Sealy
Sophie Lehmann
Department of Geology and Environmental Science, University of Pittsburgh

Corresponding Author:[email protected]

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Naomi Levin
Department of Earth and Environmental Sciences, University of Michigan
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Benjamin Passey
Department of Earth and Environmental Sciences, University of Michigan
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Huanting Hu
School of Oceanography, Shanghai Jiao Tong University
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Thure Cerling
Department of Biology and Department of Geology and Geophysics, University of Utah
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Joshua Miller
Department of Geology, University of Cincinnati
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Laura Arppe
Finnish Museum of Natural History, University of Helsinki
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Emily Beverly
Department of Earth and Atmospheric Sciences, University of Houston
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Kathryn Hoppe
Green River College and Burke Museum, University of Washington
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Julie Luyt
Department of Archaeology, University of Cape Town
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Judith Sealy
Department of Archaeology, University of Cape Town
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Reconstructing water availability in terrestrial ecosystems is key to understanding past climate and landscapes, but there are few proxies for aridity that are available for use at terrestrial sites across the Cenozoic. The isotopic composition of tooth enamel is widely used as paleoenvironmental indicator and recent work suggests the potential for using the triple oxygen isotopic composition of mammalian tooth enamel (∆’17Oenamel) as an indicator of aridity. However, the extent to which ∆’17Oenamel values vary across environments is unknown and there is no framework for evaluating past aridity using ∆’17Oenamel data. Here we present ∆’17Oenamel and δ18Oenamel values from 50 extant mammalian herbivores that vary in physiology, behavior, diet, and water-use strategy. Teeth are from sites in Africa, Europe, and North America and represent a range of environments (humid to arid) and latitudes (34S to 69N), where mean annual δ18O values of meteoric water range from -26.0‰ to 2.2‰ (VSMOW). ∆’17Oenamel values from these sites span 146 per meg (-283 to -137 per meg, where 1 per meg = 0.001‰). The observed variation in ∆’17Oenamel values increases with aridity, forming a wedged-shape pattern in a plot of aridity index vs. ∆’17Oenamel that persists regardless of region. In contrast, the plot of aridity index vs. δ18Oenamel for these same samples does not yield a distinct pattern. We use these new ∆’17Oenamel data from extant teeth to provide guidelines for using ∆’17Oenamel data from fossil teeth to assess and classify the aridity of past environments. ∆’17Oenamel values from the fossil record have the potential to be a widely used proxy for aridity without the limitations inherent to approaches that use δ18Oenamel values alone. In addition, the data presented here have implications for how ∆’17Oenamel values of large mammalian herbivores can be used in evaluations of diagenesis and past pCO2.