Collaborative Research: The Rise and Fall of the Neoproterozoic Era in Siberia: Connections between Tectonics, Ocean Chemistry, and Biologic Innovation

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The co-evolution of life and environment is one of the most compelling stories in Earth's 4.5 billion year history. For eons, simple, single-celled organisms dominated the Earth's oceans, until the first organisms with a cell nucleus began to proliferate about a billion years ago. Then, in the geologic blink of an eye approximately 550 million years ago, complex animals burst onto the scene. The timing of these two extraordinary evolutionary events has been one of the most enduring mysteries in the natural sciences. In this proposal, the principal investigators test an intriguing hypothesis that both of these evolutionary transitions were catalyzed by major mountain-building events that delivered nutrients to the oceans, and changed the amount of biologically-critical oxygen available for use by marine organisms. To test this hypothesis, the science team will measure minute differences in the masses of the chemical elements lithium (Li) and uranium (U) preserved in ancient limestone deposits from Siberia. These rocks from Siberia preserve a spectacular record of life in the oceans across these two evolutionary transitions, and new data generated from this project aim to provide a fresh look at the fundamental processes that drive evolutionary change on Earth. The researchers will also lead a broad outreach program aimed at bringing field geology and university internships to high school students in Maryland and Virginia. Specifically, spectaculargeologic formations exposed in West Virginia will be presented to students both virtually and in person, with the broad goal of training the next generation of geoscientists.The 'big bang of eukaryotic evolution' across the Mesoproterozoic-Neoproterozoic transition, and the subsequent proliferation of animals across the Ediacaran-Cambrian transition, mark two of the most critical biological transformations in Earth history. Intriguingly, both of these evolutionary events are associated with intense periods of global mountain-building, which may have delivered nutrients and changed the redox balance of the ocean-atmosphere system. To test the linkages between global tectonics, ocean oxygenation, and biological innovation, this project will measure the isotopic composition of lithium (Li) and uranium (U) in marine carbonate successions from Siberia that span each of these critical transitions in Earth history. Li isotopes are a sensitive barometer for the silicate weathering system, and U isotopes are a powerful new tool for ocean redox quantification. Pairing these isotopes with sedimentological and paleontological data from fossil-rich successions in Siberia promises to provide new insights into the environmental conditions that accompanied early eukaryotic and animal evolution on Earth.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.