The nitrogen isotope compositions (δ15N) of sedimentary rocks can provide information about the nutrient N cycling and redox conditions that may have played important roles in biological evolution in Earth's history. Although considerable δ15N data for the Precambrian have been published, there is a large gap during the Early Neoproterozoic that restrains our understanding of the linkages among N cycling, ocean redox changes and biological evolution during this key period. Here, we report bulk δ15N and organic carbon isotope (δ13Corg) compositions as well as the total nitrogen (TN) and total organic carbon (TOC) contents from the Tonian fossiliferous Liulaobei Formation in the southern part of the North China Platform. The δ15N in the study section is dominated by very stable values centering around +4.3‰, which is moderately lower than that in modern sediments (～ +6‰). These positive δ15N values were attributed to partial denitrification under low primary productivity (scenario 1) and/or denitrification coupled with dissimilatory nitrate reduction to ammonium (DNRA) (scenario 2). In either case, the availability of fixed nitrogen may have provided the nutrient N required to facilitate facilitated eukaryotic growth. Our study highlights the pivotal role of nutrient N in the evolution of eukaryotes.

Ting Yang;Xinqiang Wang;Dongtao Xu;Xiaoying Shi;Yongbo Peng

School of Earth Science and Resources,China University of Geosciences,Beijing 100083,China;State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences,Beijing 100083,China;International Center for Isotope Effect Research,Nanjing University,Nanjing 210023,China;School of Earth Sciences and Engineering,Nanjing University,Nanjing 210023,China

地球科学学刊（英文版）

[1]Ting Yang;Xinqiang Wang;Dongtao Xu;Xiaoying Shi;Yongbo Peng-.Nitrogen Isotopes from the Neoproterozoic Liulaobei Formation, North China:Implications for Nitrogen Cycling and Eukaryotic Evolution)[J].地球科学学刊（英文版）,2022(05):1309-1319

Liulaobei,Tonian

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