Nitrogen cycle changes across the Cretacous-Paleogene mass extinction event

白垩纪-古近纪（K-Pg）界的生物大灭绝事件是显生宙最大的生物大灭绝事件之一，随之而来的是生态和生物地球化学条件的剧烈变化。这项研究首次调查了灭绝事件中氮循环的变化。PI应用了先前建立的氮同位素与环境氧化态之间的关系，该关系基于主要的氮反应及其相关的同位素分馏。他们将测量几个岩心在K-Pg边界上的体积、干酪根和卟啉d15N值，以确定大灭绝事件之前、期间和之后的氮循环和古氧化还原反应。PI将测试深海中的氧浓度在撞击事件发生后下降的假设，并且位于不同海洋盆地的岩心将根据每个位置的深水氧化还原状态记录不同的d15N剖面。研究结果将为全球大灭绝过程和生物地球化学系统的恢复提供重要信息。资金支持一名新的女PI和一名研究生。更广泛的影响包括与COSEE-NOW（海洋科学卓越教育网络海洋世界中心）合作，开发旨在提高海洋素养的教育产品。资金支持由美国国家科学基金会海洋科学部的海洋地质和地球物理计划以及刺激竞争性研究的实验计划（EPSCoR）提供。

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).