NSFGEO-NERC: Collaborative Research: Developing a new Lower Cretaceous time scale: Foundation for the next generation of paleoceanographic and biogeochemical studies

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The Cretaceous was a time of global warming during which atmospheric carbon dioxide levels surpassed 800 ppm, similar to those predicted for 2100 by “business-as-usual” emission scenarios. Cretaceous rocks record high sea levels, high biological productivity, massive volcanism, and major perturbations of the carbon cycle during several ocean anoxic events (OAEs). Understanding these phenomena can provide deep-time analogs for future greenhouse scenarios. Marine sediments that record these crises are globally widespread but weaving these records into a common temporal framework is essential if they are to reveal the causes. This project aims to generate a new temporal framework spanning 125 to 93 million years ago during which several major OAEs occurred. This will permit examination of repeated deteriorations of marine ecosystems across the Pacific, Atlantic, and Mediterranean oceans. The team will be involved in novel outreach, international collaboration, and training of future earth science leaders. They will bring deep-time science to the public via presence at the Sturgis Motorcycle Rally. The favored hypothesis for ocean anoxic events involves volcanic initiation leading to a cascade of processes amplifying global marine production; key factors are the nature of volcanism and the source of increased nutrients. Yet geographic differences in proxy records (Carbon and Osmium isotopes) indicate additional complexities, such as sea level and ocean circulation. The goals for the project are to establish: (1) A new time scale for global geochemical and paleobiologic datasets; (2) Chemostratigraphic correlation of the new time scale to European sections using isotope stratigraphy, and (3) A new global time scale for improved understanding of major biogeochemical perturbations. The team will: (i) Determine radioisotopic ages of rhyolitic tuffs in sediments of Japan, (ii) Integrate these new ages with new Osmium and Carbon isotope chemostratigraphy in Europe, (iii) Compile global geochemical proxy data for OAE 1a within a common temporal and stratigraphic framework, and analyze trends and patterns from the Pacific to Europe, (iv) Evaluate the volcanic versus climatic/orbital hypotheses for OAE initiation, and (v) Explore the significance of geography in the timing and magnitude of geochemical signals.This is a project that is jointly funded by the National Science Foundation’s Directorate of Geosciences (NSF/GEO) and the National Environment Research Council (UKRI/NERC) of the United Kingdom (UK) via the NSF/GEO-NERC Lead Agency Agreement. This Agreement allows a single joint US/UK proposal to be submitted and peer-reviewed by the Agency whose investigator has the largest proportion of the budget. Upon successful joint determination of an award, each Agency funds the proportion of the budget and the investigators associated with its own investigators and component of the work.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.