PP21A-2208
Triple oxygen isotopes and clumped isotopes in modern vertebrate and dinosaur biominerals: Records of paleoecology, paleoaridity, and paleo-carbon-cycling

Tuesday, 15 December 2015
Poster Hall (Moscone South)
Huanting Hu1, Benjamin H Passey2, Sophie Butler Lehmann2, Naomi E. Levin3, Shaena Montanari4, Karen Chin5 and Beverly J Johnson6, (1)Johns Hopkins University, Baltimore, MD, United States, (2)Johns Hopkins University, Department of Earth and Planetary Sciences, Baltimore, MD, United States, (3)Johns Hopkins Univ-EPS, Baltimore, MD, United States, (4)American Museum of Nat History, New York, NY, United States, (5)University of Colorado at Boulder, Department of Geological Sciences and Curator of Paleontology, Boulder, CO, United States, (6)Bates College, Lewiston, ME, United States
Abstract:
The parameter Δ17O describes the departure of δ17O from an expected equilibrium relationship with δ18O, which can be caused by factors such as evaporation of parent waters, and photochemical reactions among oxygen-bearing gases in stratosphere. Hence, the Δ17O of water records information about environmental aridity, and the Δ17O of atmospheric O2 is related to atmospheric concentrations of CO2 and O2, and gross primary productivity (GPP). Vertebrates incorporate Δ17O signals of input water (e.g. drinking water and free food water) and atmospheric O2 into body water through respiration, and biominerals forming in equilibrium with body water can preserve this signal over geological timescales. The preservation of fossil biominerals can be evaluated by clumped isotopes as they record the temperature of mineralization, be it primary mineralization in the living animal (at body temperature), or secondary mineralization during diagenesis. We can distinguish the alteration of samples from the deviation between observed clumped isotope temperatures and plausible body temperatures. Meanwhile, diagenesis tends to moderate Δ17O of biominerals towards Δ17O of meteoric waters, such that measured Δ17O values reflect the minimum anomaly in fossil samples. Thus, preservation of anomalous Δ17O indicates at least partial preservation of the original signal.

We present Δ17O data from both modern vertebrate and fossil dinosaur biominerals. We use a 17O-enabled body water model to explore the influence of aridity and dietary ecology on animal Δ17O, and to predict the degree of dilution of the atmospheric O2 Δ17O signal by other sources of oxygen to the animal. We observe: 1) animals consuming more leaf water than drinking water are “evaporation sensitive” (ES) animals, and have lower Δ17O relative to “evaporation insensitive” animals in the same climates; 2) ES animals from arid climates have lower Δ17O values compared to ES animals from humid climates, which forms the basis of a paleoaridity proxy; and 3) anomalously low body water Δ17O values are observed for some of the dinosaur samples, indicating a significantly different carbon cycle during that time, with pCO2 up to 3250±1250 ppm during late Jurassic assuming present day GPP and pO2.