GSA Annual Meeting in Indianapolis, Indiana, USA - 2018

Paper No. 283-12
Presentation Time: 4:40 PM


SONG, Huyue1, ALGEO, Thomas J.2, SONG, Haijun1, TONG, Jinnan1, SHEN, Shuzhong3, CHEN, Xinming4, ROMANIELLO, Stephen J.4, ZHU, Yuanyuan5, SHAN, Huasheng1, WEI, Hengye6 and ANBAR, Ariel D.7, (1)State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan, 430074, China, (2)Department of Geology, University of Cincinnati, Cincinnati, OH 45221-0013, (3)State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, 39 East Beijing Road, Nanjing, 210008, China, (4)School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, (5)Wuhan Institute of Geology and Mineral Resources, Wuhan, 430205, (6)School of Earth Science,, East China University of Technology, Nanchang, 330013, China, (7)School of Earth and Space Exploration and Department of Chemistry & Biochemistry, Arizona State University, Tempe, AZ 85287-1404

The Capitanian (late Middle Permian) mass extinction was a major Phanerozoic biocrisis yet its timing and causation remain poorly understood. Here, we generated a high-resolution U-isotopic (δ238U) profile for the mid-Capitanian to lower Wuchiapingian of the Penglaitan section (Middle/Upper Permian GSSP) to explore the causal relationship between the mass extinction and contemporaneous oceanic anoxic events (OAEs). This profile documents two distinct negative δ238U excursions, the first recording the mid-Capitanian OAE-C1 and the second the end-Capitanian OAE-C2. Box modeling indicates that the anoxic/euxinic sink for seawater U increased from <40 % to >80 % of the total U flux during these OAEs. Each of these OAEs coincided with a mass extinction pulse and a positive δ13C excursion and volcanic eruptions of the Emeishan LIP. We propose that volcanic eruptions enhanced nutrient availability and primary productivity, resulting in positive δ13C excursions and oceanic anoxic events. Furthermore, each OAE coincided with a phase of biotic extinction, providing the first evidence of a causal relationship between oceanic anoxia and mass extinction during the Capitanian. Our finding challenges hypotheses based on cooling or volcanic winter scenarios for this biotic crisis.