TY - JOUR
T1 - SIMS and NanoSIMS analyses of well-preserved microfossils imply oxygen-producing photosynthesis in the Mesoproterozoic anoxic ocean
AU - Peng, Xiaotong
AU - Guo, Zixiao
AU - House, Christopher H.
AU - Chen, Shun
AU - Ta, Kaiwen
N1 - Funding Information:
We thank Qiuyue Jia for the expert sample preparation at Peking University, Jialong Hao, Jianchao Zhang, Guoqiang Tang and Yu Liu for the assistance with the NanoSIMS and IMS-1280 at the Institute of Geology and Geophysics, Chinese Academy of Sciences (IGGCAS). We also thank Kevin Lepot from the NASA Astrobiology Institute and Kenichiro Sugitani from the Nagoya University for communication before the carbon isotope analysis. We are grateful for constructive comments from Kenneth H. Williford and an anonymous reviewer which have significantly improved the manuscript. Funding for this study was provided by the Strategic Priority Research Program of the Chinese Academy of Sciences ( XDB06020000 ), the National Key Basic Research Program of China ( 2015CB755905 ), and the National Natural Science Foundation of China (grant 41172309 ).
Publisher Copyright:
© 2016 Elsevier B.V.
PY - 2016/11/21
Y1 - 2016/11/21
N2 - Well-preserved microfossils in the stromatolitic cherts from the Gaoyuzhuang Formation (~ 1500 Ma), which have one of the best state of preservation in the Proterozoic Era, may play key roles in systematizing information about the evolution of early life in the Proterozoic Ocean. Here, a combination of light microscopy (LM), scanning electron microscopy (SEM), nano-scale secondary ion mass spectrometry (NanoSIMS), secondary ion mass spectrometry (SIMS) and geochemical techniques was employed to characterize the morphology, elemental distributions and carbon isotope values of individual Gaoyuzhuang microfossils, and their growing environment. Light microscopy analyses show that abundant filamentous and coccoid microfossils, classified as oscillatoriacean and chroococcacean cyanobacteria, respectively, are exceptionally well preserved in chert. NanoSIMS analyses show that metabolically important elements, such as 12C−, 13C−, 12C14N−, 32S−, and 34S−, are concentrated in these microfossils and that the variations in the concentrations of these elements are similar to each other, establishing the elemental patterns in undoubtedly biogenic microstructures. The carbon isotope (δ13C) values of individual microfossils range from − 31.7‰ ± 0.9‰ to − 23.1‰ ± 1.0‰ (weighted mean = − 28.5‰ ± 0.1‰), consistent not only with a Calvin Cycle-based photosynthesis, but typically for chroococcacean cyanobacteria as well. Our results, for the first time, provide the element distributions and cell specific carbon isotope values on convincing Mesoproterozoic cyanobacterial fossils, supporting sustained oxygen-producing photosynthesis in the Proterozoic Ocean. The geochemical data indicate these fossil microorganisms may grow in an anoxic seawater, potentially supporting the delayed oxygenation on the Earth. In this regard, this integrated approach may be a step towards a more comprehensive picture of the evolution of early life on the Earth.
AB - Well-preserved microfossils in the stromatolitic cherts from the Gaoyuzhuang Formation (~ 1500 Ma), which have one of the best state of preservation in the Proterozoic Era, may play key roles in systematizing information about the evolution of early life in the Proterozoic Ocean. Here, a combination of light microscopy (LM), scanning electron microscopy (SEM), nano-scale secondary ion mass spectrometry (NanoSIMS), secondary ion mass spectrometry (SIMS) and geochemical techniques was employed to characterize the morphology, elemental distributions and carbon isotope values of individual Gaoyuzhuang microfossils, and their growing environment. Light microscopy analyses show that abundant filamentous and coccoid microfossils, classified as oscillatoriacean and chroococcacean cyanobacteria, respectively, are exceptionally well preserved in chert. NanoSIMS analyses show that metabolically important elements, such as 12C−, 13C−, 12C14N−, 32S−, and 34S−, are concentrated in these microfossils and that the variations in the concentrations of these elements are similar to each other, establishing the elemental patterns in undoubtedly biogenic microstructures. The carbon isotope (δ13C) values of individual microfossils range from − 31.7‰ ± 0.9‰ to − 23.1‰ ± 1.0‰ (weighted mean = − 28.5‰ ± 0.1‰), consistent not only with a Calvin Cycle-based photosynthesis, but typically for chroococcacean cyanobacteria as well. Our results, for the first time, provide the element distributions and cell specific carbon isotope values on convincing Mesoproterozoic cyanobacterial fossils, supporting sustained oxygen-producing photosynthesis in the Proterozoic Ocean. The geochemical data indicate these fossil microorganisms may grow in an anoxic seawater, potentially supporting the delayed oxygenation on the Earth. In this regard, this integrated approach may be a step towards a more comprehensive picture of the evolution of early life on the Earth.
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U2 - 10.1016/j.chemgeo.2016.08.011
DO - 10.1016/j.chemgeo.2016.08.011
M3 - Article
AN - SCOPUS:84981492528
SN - 0009-2541
VL - 441
SP - 24
EP - 34
JO - Chemical Geology
JF - Chemical Geology
ER -