TY - JOUR
T1 - Interaction of Shibantan Biota and environment in the terminal Ediacaran ocean
T2 - Evidence from I/(Ca+Mg) and sulfur isotopes
AU - Huang, Kaiqi
AU - Cheng, Meng
AU - Algeo, Thomas J.
AU - Hu, Jun
AU - Wang, Haiyang
AU - Zhang, Zihu
AU - Dodd, Matthew S.
AU - Wu, Yan
AU - Guo, Wei
AU - Li, Chao
N1 - Funding Information:
We thank Bao Li, Wei Shi, Jie Fang and Wei Wang for their helps on sample collection or helpful discussions. We also sincerely thank three anonymous reviewers and the guest editor Dr. Xingliang Zhang for their constructive comments and suggestions, which greatly improved the manuscript. We are grateful for the supply of I/(Ca+Mg) data of the Xiaotan section by Drs. Hongfei Ling, Zunli Lu and Da Li. This study was funded by the National Natural Science Foundation of China (Grants #41821001 , #41825019 , #42072335 and #42130208 ) and the 111 Project of China (Grant #BP0820004 ).
Publisher Copyright:
© 2022
PY - 2022/9/1
Y1 - 2022/9/1
N2 - The terminal Ediacaran (∼551–539 Ma) was a crucial period in Earth's history that witnessed the first appearance of skeletonized animals and complex ecosystems (e.g., the Shibantan Biota) in the ocean. However, the trigger for such biological innovations and their feedbacks to the environment are still poorly understood. In this study, to explore possible interactions between the Shibantan Biota and the oceanic environment, we carried out an integrated investigation of I/(Ca+Mg) along with sulfur isotopes of carbonate-associated sulfate (δ34SCAS) and pyrite (δ34Spy) in the Shibantan Member of the Dengying Formation at Wuhe (South China) where the Shibantan Biota was recovered. Our I/(Ca+Mg) profile yields fluctuating values in the range of 0.03 to 1.86 μmol/mol, corresponding to oxygen concentrations between 1–3 μM and 20–70 μM in the water column of the study area. This result indicates that the oxygen levels in shallow-water environments of the terminal Ediacaran ocean were generally low and the Shibantan Biota must have had low physiological requirements of oxygen. Variably high δ34SCAS values (+31.8‰ to +55.7‰, mean ± 1σ: +41.0 ± 5.2‰) were observed in studied unit, implying low sulfate concentrations in the terminal Ediacaran ocean, consistent with contemporaneous expansion of seawater anoxia. Furthermore, isotopically superheavy pyrites (i.e., δ34Spy > δ34SCAS) are present in the lower Shibantan Member, concurrent with the occurrence of bioturbation in the sediments, suggesting controls by microbial sulfate reduction (MSR) in sulfate-limited porewaters followed by preferential re-oxidation of 32S-riched H2S under the influence of burrowing organisms. This finding supports that burrowing activity of infaunas of the Shibantan Biota may have enhanced sediment porewater oxygenation, thus likely expanding the ecosystem space available to early animals. Our study thus provides new insights into the coevolution of early animals and terminal Ediacaran ocean environments.
AB - The terminal Ediacaran (∼551–539 Ma) was a crucial period in Earth's history that witnessed the first appearance of skeletonized animals and complex ecosystems (e.g., the Shibantan Biota) in the ocean. However, the trigger for such biological innovations and their feedbacks to the environment are still poorly understood. In this study, to explore possible interactions between the Shibantan Biota and the oceanic environment, we carried out an integrated investigation of I/(Ca+Mg) along with sulfur isotopes of carbonate-associated sulfate (δ34SCAS) and pyrite (δ34Spy) in the Shibantan Member of the Dengying Formation at Wuhe (South China) where the Shibantan Biota was recovered. Our I/(Ca+Mg) profile yields fluctuating values in the range of 0.03 to 1.86 μmol/mol, corresponding to oxygen concentrations between 1–3 μM and 20–70 μM in the water column of the study area. This result indicates that the oxygen levels in shallow-water environments of the terminal Ediacaran ocean were generally low and the Shibantan Biota must have had low physiological requirements of oxygen. Variably high δ34SCAS values (+31.8‰ to +55.7‰, mean ± 1σ: +41.0 ± 5.2‰) were observed in studied unit, implying low sulfate concentrations in the terminal Ediacaran ocean, consistent with contemporaneous expansion of seawater anoxia. Furthermore, isotopically superheavy pyrites (i.e., δ34Spy > δ34SCAS) are present in the lower Shibantan Member, concurrent with the occurrence of bioturbation in the sediments, suggesting controls by microbial sulfate reduction (MSR) in sulfate-limited porewaters followed by preferential re-oxidation of 32S-riched H2S under the influence of burrowing organisms. This finding supports that burrowing activity of infaunas of the Shibantan Biota may have enhanced sediment porewater oxygenation, thus likely expanding the ecosystem space available to early animals. Our study thus provides new insights into the coevolution of early animals and terminal Ediacaran ocean environments.
KW - Bioturbation
KW - Dengying Formation
KW - Dissolved oxygen
KW - South China
KW - Sulfate
KW - Superheavy pyrite
UR - http://www.scopus.com/inward/record.url?scp=85138835250&partnerID=8YFLogxK
U2 - 10.1016/j.precamres.2022.106814
DO - 10.1016/j.precamres.2022.106814
M3 - Article
AN - SCOPUS:85138835250
SN - 0301-9268
VL - 379
JO - Precambrian Research
JF - Precambrian Research
M1 - 106814
ER -