Quantifying the Seawater Sulfate Concentration in the Cambrian Ocean

Although the earliest animals might have evolved in certain “sweet spots” in the last 10 million years of Ediacaran (550–541 Ma), the Cambrian explosion requires sufficiently high levels of oxygen (O2) in the atmosphere and diverse habitable niches in the substantively oxygenated seafloor. However,...

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Autores principales:	Guangyou Zhu, Tingting Li, Tianzheng Huang, Kun Zhao, Wenbo Tang, Ruimin Wang, Xianguo Lang, Bing Shen
Formato:	article
Lenguaje:	EN
Publicado:	Frontiers Media S.A. 2021
Materias:	sulfur isotope pyrite iron speciation Tarim block Yurtus formation Science Q
Acceso en línea:	https://doaj.org/article/3230decff280431690d5ef916eaf4a07
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spelling	oai:doaj.org-article:3230decff280431690d5ef916eaf4a072021-11-18T09:27:47ZQuantifying the Seawater Sulfate Concentration in the Cambrian Ocean2296-646310.3389/feart.2021.767857https://doaj.org/article/3230decff280431690d5ef916eaf4a072021-11-01T00:00:00Zhttps://www.frontiersin.org/articles/10.3389/feart.2021.767857/fullhttps://doaj.org/toc/2296-6463Although the earliest animals might have evolved in certain “sweet spots” in the last 10 million years of Ediacaran (550–541 Ma), the Cambrian explosion requires sufficiently high levels of oxygen (O2) in the atmosphere and diverse habitable niches in the substantively oxygenated seafloor. However, previous studies indicate that the marine redox landscape was temporally oscillatory and spatially heterogeneous, suggesting the decoupling of atmospheric oxygenation and oceanic oxidation. The seawater sulfate concentration is controlled by both the atmospheric O2 level and the marine redox condition, with sulfide oxidation in continents as the major source, and sulfate reduction and pyrite burial as the major sink of seawater sulfate. It is thus important to quantify the sulfate concentration on the eve of the Cambrian explosion. In this study, we measured the pyrite contents and pyrite sulfur isotopes of black shale samples from the Yurtus Formation (Cambrian Series 2) in the Tarim Block, northwestern China. A numerical model is developed to calculate the seawater sulfate concentration using the pyrite content and pyrite sulfur isotope data. We first calibrate some key parameters based on observations from modern marine sediments. Then, the Monte Carlo simulation is applied to reduce the uncertainty raised by loosely confined parameters. Based on the geochemical data from both Tarim and Yangtze blocks, the modeling results indicate the seawater sulfate concentration of 8.9–14 mM, suggesting the seawater sulfate concentration was already 30–50% of the present level (28 mM). High seawater sulfate concentration might be attributed to the enhanced terrestrial sulfate input and widespread ocean oxygenation on the eve of the Cambrian explosion.Guangyou ZhuTingting LiTianzheng HuangKun ZhaoWenbo TangRuimin WangXianguo LangBing ShenFrontiers Media S.A.articlesulfur isotopepyriteiron speciationTarim blockYurtus formationScienceQENFrontiers in Earth Science, Vol 9 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	sulfur isotope pyrite iron speciation Tarim block Yurtus formation Science Q
spellingShingle	sulfur isotope pyrite iron speciation Tarim block Yurtus formation Science Q Guangyou Zhu Tingting Li Tianzheng Huang Kun Zhao Wenbo Tang Ruimin Wang Xianguo Lang Bing Shen Quantifying the Seawater Sulfate Concentration in the Cambrian Ocean
description	Although the earliest animals might have evolved in certain “sweet spots” in the last 10 million years of Ediacaran (550–541 Ma), the Cambrian explosion requires sufficiently high levels of oxygen (O2) in the atmosphere and diverse habitable niches in the substantively oxygenated seafloor. However, previous studies indicate that the marine redox landscape was temporally oscillatory and spatially heterogeneous, suggesting the decoupling of atmospheric oxygenation and oceanic oxidation. The seawater sulfate concentration is controlled by both the atmospheric O2 level and the marine redox condition, with sulfide oxidation in continents as the major source, and sulfate reduction and pyrite burial as the major sink of seawater sulfate. It is thus important to quantify the sulfate concentration on the eve of the Cambrian explosion. In this study, we measured the pyrite contents and pyrite sulfur isotopes of black shale samples from the Yurtus Formation (Cambrian Series 2) in the Tarim Block, northwestern China. A numerical model is developed to calculate the seawater sulfate concentration using the pyrite content and pyrite sulfur isotope data. We first calibrate some key parameters based on observations from modern marine sediments. Then, the Monte Carlo simulation is applied to reduce the uncertainty raised by loosely confined parameters. Based on the geochemical data from both Tarim and Yangtze blocks, the modeling results indicate the seawater sulfate concentration of 8.9–14 mM, suggesting the seawater sulfate concentration was already 30–50% of the present level (28 mM). High seawater sulfate concentration might be attributed to the enhanced terrestrial sulfate input and widespread ocean oxygenation on the eve of the Cambrian explosion.
format	article
author	Guangyou Zhu Tingting Li Tianzheng Huang Kun Zhao Wenbo Tang Ruimin Wang Xianguo Lang Bing Shen
author_facet	Guangyou Zhu Tingting Li Tianzheng Huang Kun Zhao Wenbo Tang Ruimin Wang Xianguo Lang Bing Shen
author_sort	Guangyou Zhu
title	Quantifying the Seawater Sulfate Concentration in the Cambrian Ocean
title_short	Quantifying the Seawater Sulfate Concentration in the Cambrian Ocean
title_full	Quantifying the Seawater Sulfate Concentration in the Cambrian Ocean
title_fullStr	Quantifying the Seawater Sulfate Concentration in the Cambrian Ocean
title_full_unstemmed	Quantifying the Seawater Sulfate Concentration in the Cambrian Ocean
title_sort	quantifying the seawater sulfate concentration in the cambrian ocean
publisher	Frontiers Media S.A.
publishDate	2021
url	https://doaj.org/article/3230decff280431690d5ef916eaf4a07
work_keys_str_mv	AT guangyouzhu quantifyingtheseawatersulfateconcentrationinthecambrianocean AT tingtingli quantifyingtheseawatersulfateconcentrationinthecambrianocean AT tianzhenghuang quantifyingtheseawatersulfateconcentrationinthecambrianocean AT kunzhao quantifyingtheseawatersulfateconcentrationinthecambrianocean AT wenbotang quantifyingtheseawatersulfateconcentrationinthecambrianocean AT ruiminwang quantifyingtheseawatersulfateconcentrationinthecambrianocean AT xianguolang quantifyingtheseawatersulfateconcentrationinthecambrianocean AT bingshen quantifyingtheseawatersulfateconcentrationinthecambrianocean
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Quantifying the Seawater Sulfate Concentration in the Cambrian Ocean

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