Collaborative Research: Using Ca, Sr, Mg, and Fe isotope proxies to constrain redox and continental weathering during Ocean Anoxic Event 2

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Rapid increases of carbon dioxide in the atmosphere can lead to changes in the global ocean, including increased acidification, lower oxygen, and significantly reduced plant and animal life. This project’s scientists are interested in changes in ocean chemistry and global climate 94 million years ago when the atmosphere had up to 5 times more carbon dioxide than Earth’s present atmosphere, and the concentrations varied dramatically. The researchers are measuring isotopes of strontium, calcium, magnesium, and iron in rocks from the Eagle Ford Group in Texas that formed from an ancient seabed. The results are leading to a better understanding of the factors that led to and sustained that period of global warming, and they are revealing implications for present-day climate change. This research is aiding the career development of a Ph.D. student from an underrepresented group and an early career female scientist. A museum exhibit on climate and energy is being created to outreach to the public about this work.The Late Cretaceous Ocean Anoxic Event 2 (OAE2) was a sustained period of high atmospheric carbon dioxide and consequent warming of the global climate. How global warming is related to volcanic activity, and the cascading effects on continental weathering and global ocean chemistry, remain open questions. A complete stratigraphic section through OAE2 from the Eagle Ford Group in Texas is being examined for Sr, Ca, Mg, and Fe isotopes. Each of these element systems record distinct chemical information on the global ocean environment and on changing climate. Numerical mass balance models based on the isotope data are being employed to constrain the inputs and outputs to the global ocean and the feedback between volcanic activity and continental weathering. Results are providing a framework for further examination of the causes of ocean anoxia and substantial climate change in the geological past, and are allowing a better understanding of the factors contributing to future climate change. Broader impacts of this project include mentoring and training students from underrepresented groups and public outreach about the links between climate and energy.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.