Goldschmidt 2019 Conference abstractsÂÂ
Rise of dinosaurs linked to increasing oxygen levels
New constraints on ancient atmospheric oxygen concentrations and the Late Triassic rise of the first North American dinosaurs
MORGAN F. SCHALLER, ELIZABETH PETTITT, TODD KNOBBE, DANIEL O. BREECKER
We have developed a new proxy for ancient atmospheric oxygen concentrations based on the composition of soil carbonate-hosted fluid inclusions. Fluid inclusions form in equilibrium with the soil pore space gas during inclusion closure. Based on modern soil gas measurements, we show that the atmospheric gases liberated from soil carbonate-hosted inclusions closely reflect soil gas concentrations and contain all the major atmospheric species. The concentration of O2 in soil pore space gas is controlled by respiration and diffusion-mediated exchange with the atmosphere, and we show that profiles of fluid inclusion compositions can be used along with production-diffusion modeling to reconstruct atmospheric pO2. An inversion of the diffusion model can be solved iteratively to predict atmospheric O2 from the gases hosted in modern soil carbonates and reproduces modern atmospheric pO2. The model is then applied to Late Triassic paleosols from cores taken through two contemporaneous sedimentary sequences that formed >1000 km apart across the Pangean supercontinent: the Colorado Plateau and Newark Basin Coring Projects (CPCP and NBCP). Combined results from the Colorado Plateau and Newark Basin show a secular increase in pO2 that corresponds to a decrease in pCO2, coinciding with the appearance of the very first North American dinosaur, Chindesaurus.
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Estimation of Dinosaur Body Temperature From Late Cretaceous Sauropod Eggshell From India Using Carbonate Clumped Isotopes
YOGARAJ BANERJEE, PROSENJIT GHOSH, RAJEEV PATNAIK, SYED A JAFAR, ASHOK SAHNI ÂÂ
The thermal physiology of saurischian dinosaurs is a subject of research interest over the years. Here in this study, we have carried out clumped isotope investigation on well preserved late Cretaceous Sauropod eggshell from India. Our preliminary investigation reveals a Î47 based temperature of 39 (Â2)ÂC in CDES scale, similar to the Titanosurid eggshell investigated by [1] and theoritically predicted value [2]. Clumped isotope study on co eval Crocodile egg shell reveals a temperature of 28 (Â4)ÂC. We have also carried out similar investigation on the Australian Emu, Egyptian Ostrich and Antarctic Penguin eggshells of recent to subrecent time frame, which yielded temperatures around 42 (Â2)ÂC. It is interesting to note that the Î18Owater derived from the sauropod egg shell shows an enriched signature of 4.59â in VSMOW scale similar Titanosurid eggshell investigated by [1]. On contrary co eval Crocodile eggshell captures a freshwater Î18Owater signature. Possible scenarios related to palaeo physiological processes and disequillibrium isotope effect will be discussed during presentation to explain the obtained temperature and Î18Owater information.
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