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DOI	10.1016/j.gca.2020.01.032
	Two distinct episodes of marine anoxia during the Permian-Triassic crisis evidenced by uranium isotopes in marine dolostones
	Zhang, Feifei; Shen, Shu-zhong; Cui, Ying; Lenton, Timothy M.; Dahl, Tais W.; Zhang, Hua; Zheng, Quan-feng; Wang, Wenqian; Krainer, Karl; Anbar, Ariel D.
通讯作者	Zhang, FF ; Shen, SZ (通讯作者)
发表日期	2020
ISSN	0016-7037
EISSN	1872-9533
起始页码	165
结束页码	179
卷号	287
英文摘要	The end-Permian mass extinction (EPME; ca. 251.94 Ma) is the most severe mass extinction in the geological record. Detailed paleobiological investigations show a very rapid EPME event, and recently published delta U-238 data show a large negative excursion and thus a massive shift to globally expanded anoxia at the main extinction phase in the latest Permian. The negative shift in delta U-238 is in correlation with a globally characterized negative delta C-13 excursion near the Permian-Triassic boundary (PTB). In some highly expanded PTB carbonate sections, however, there are two distinct negative delta C-13 excursions whereas uranium isotopes (delta U-238) from such sections have not yet been examined, leaving a gap in the understanding of the global perturbations of marine redox conditions immediately following the EPME. Here, we present a new delta U-238 study of syndepositional dolostones from a well-characterized and highly expanded drill core, which recorded two pronounced negative delta C-13 excursions across the PTB, from the Carnic Alps, Austria. This drill core extends 331-meters across the PTB and provides a unique opportunity to explore the detailed timing, duration, and extent of marine redox chemistry changes before, during, and immediately after the EPME. Our new delta U-238 record shows two negative shifts, which are correlated with the two negative delta C-13 excursions. The first negative delta U-238 excursion preceding the EPME confirms the recently published delta U-238 records from across the EPME and support that syndepositional marine dolostones can record delta U-238 trends of seawater similar to that of limestones. Modeling of uranium isotope cycling in the latest Permian and earliest Triassic oceans suggests two distinct stages of expanded marine anoxia separated by a brief interval (similar to 100 kyr) of reoxygenation across the PTB. The first anoxic episode lasted for 60 kyr while anoxic seafloor area expanded to cover >18% of the entire seafloor, coeval with the main EPME horizon, agreeing with marine anoxia as a proximate kill mechanism for the EPME. The second anoxic event was less intense compared to the first anoxic pulse but sustained for a longer duration. A global modeling of coupled C, P, and U cycles show that two pulses of volcanic carbon injection that drives global warming and increased phosphorus weathering rate can reasonably reproduce our data to match two phases of anoxia. The model also demonstrates that the loss of terres-trial vegetation in the EPME is crucial to generating an intervening interval of oxygenated ocean. Our new study adds to a growing body of evidence that the global marine redox conditions underwent rapid oscillations during the EPME event and continued afterward, which may have played a central role in delaying the marine ecosystem recovery in the Early Triassic. (c) 2020 Elsevier Ltd. All rights reserved.
关键词	GLOBAL CARBON-CYCLE MASS EXTINCTION OCEANIC ANOXIA SOUTH CHINA WEATHERING RATES BOUNDARY U-238/U-235 PALEOREDOX RECORDS MIDDLE
英文关键词	Permian-Triassic; End-Permian mass extinction; Marine anoxia; Uranium isotopes; Mass balance model; Biogeochemical model
语种	英语
WOS研究方向	Geochemistry & Geophysics
WOS类目	Geochemistry & Geophysics
WOS记录号	WOS:000570270000010
来源期刊	GEOCHIMICA ET COSMOCHIMICA ACTA
来源机构	中国科学院青藏高原研究所
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/260080
推荐引用方式 GB/T 7714	Zhang, Feifei,Shen, Shu-zhong,Cui, Ying,et al. Two distinct episodes of marine anoxia during the Permian-Triassic crisis evidenced by uranium isotopes in marine dolostones[J]. 中国科学院青藏高原研究所,2020,287.
APA	Zhang, Feifei.,Shen, Shu-zhong.,Cui, Ying.,Lenton, Timothy M..,Dahl, Tais W..,...&Anbar, Ariel D..(2020).Two distinct episodes of marine anoxia during the Permian-Triassic crisis evidenced by uranium isotopes in marine dolostones.GEOCHIMICA ET COSMOCHIMICA ACTA,287.
MLA	Zhang, Feifei,et al."Two distinct episodes of marine anoxia during the Permian-Triassic crisis evidenced by uranium isotopes in marine dolostones".GEOCHIMICA ET COSMOCHIMICA ACTA 287(2020).