Nitrogen cycle changes across the Cretacous-Paleogene mass extinction event

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The mass extinction event at the Cretaceous-Paleogene (K-Pg) boundary was one of the largest such events during the Phanerozoic and was following by a period of drastic changes in ecological and biogeochemical conditions. This research is the first to investigate changes in the nitrogen cycle across the extinction event. The PI applies a previously established a relationship between nitrogen isotopes and the oxidation state of the environment based on the predominant nitrogen reactions and their associated isotopic fractionation. They will measure the bulk, kerogen, and porphyrin d15N values across the K-Pg boundary for several cores to determine nitrogen cycling and paleoredox reactions before, during, and after the mass extinction event. The PI will test the hypothesis that the oxygen concentration in the deep waters decreased following the impact event, and that cores located in different ocean basins will record different d15N profiles as dictated by the deep water redox state at each location. The results will provide important information about the processes of global mass extinction and the subsequent recovery of biogeochemical systems. Funding supports a new female PI and a graduate student. Further broader impacts include collaboration with the COSEE-NOW (Center for Ocean Sciences Education Excellence Networked Ocean World) to develop educational products aimed at improving ocean literacy. Funding support is provided by the Marine Geology and Geophysics Program of NSF's Ocean Science Division and by the Experimental Program to Stimulate Competitive Research (EPSCoR).