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Pioneer organisms after F-F mass extinction in Dushan region,Guizhou Province,and their significance in establishing new ecosystem

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Science china {1. {2. 2006年第5期49卷 449-460页

作者： wang yue1,{1.,{2., beijing 100083. china 2. school of resources and Environment, Guizhou university, Guiyang 550003, china school of {1. {2. and resources China University of Geosciences Beijing China school of {1. and Environment Guizhou University Guiyang China

After mass extinctions, most areas became “ecologically barren areas” lacking or even without ecosystem over an extensive region. Studying the pioneer organisms and the reconstruction process of a new ecosystem in the “ecologically barren area” is very important for revealing the evo- lution after bio-mass extinctions. In the Dushan region, Guizhou Province, china, the trace fossils appeared and flourished evidently earlier than body fossils after Frasnian-Famennian (F-F) mass extinction. The pioneer organisms and pathfinders in the “ecologically barren areas” are the trace-makers that are deposit-feeders with relatively simple structure and conformation on or near the deposit surface. The trace-makers have undergone an evolutionary process that their trace structures changed from simple to complex, and their living and moving areas and spaces enlarged from linear to planar and then to three-dimension spaces. Those characters show that the ability of the trace-makers to deposits and their efficiency of looking for food have been enhanced gradually and that those trace-makers constructed gradually a base for the new ecosystem. This process is similar to that of the trace fossils near the Precambrian-Cambrian boundary. In the Dushan area, only the recovery intervals have been identified for the Famennian body fossils, with no eminent radiation interval recognizable due to the Devonian-Carboniferous (C-D) mass ex- tinction. However, both the recovery and radiation intervals may be clearly recognized in the Famen- nian trace fossils based on their conformation and diversity. The evolution and diversification of the trace fossils in the “ecologically barren area” is considered to have played a role of necessary foun- dation for the recovery of body fossils in the ecological chain. With the gradual disappearance of the unfavourable environment factors resulting in the F-F mass extinction, a new ecosystem was reconstructed in the “ecologically barren area” through a three-

关键词： pioneer organisms, reconstruction of ecosystem, trace fossils, F-F mass extinction, Later Devonian, Dushan region, Guizhou Province, china.

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Spatio-temporal carbon isotope variation during the Ediacaran period in South china and its impact on bio-evolution

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Science china {1. {2. 2009年第10期52卷 1520-1528页

作者： wang XinQiang1 & shi {2.,2.1 school of earth Science and Mineral resources, china university of geosciences, beijing 100083. china 2.State Key Laboratory of Geological Processes and Mineral resources, beijing 100083. china school of {1. Science and Mineral {2. China University of Geosciences Beijing China State Key Laboratory of Geological Processes and Mineral resources Beijing China

The Ediacaran period is characterized by the extremely negative carbon isotope anomalies and great biotic evolution in earth history. At least four negative carbon isotope anomalies have been reported from this interval in South {1. so far. It is traditionally argued that the isotope variations can be used as a useful tool for global correlation of Ediacaran succession; however, more and more researches argued against this idea. We reviewed the previously published carbon isotope data in South {1., and distributed the mean values of a certain time to the paleogeographic maps. The results show that the carbon isotope values (δ1.C) vary greatly in different environments, but a clear tendency of becoming lighter from shallow platform to deep basin, with a maximum variation up to 1. Moreover, the important changes in Ediacaran biota, marked by the introducing of new taxa or ecologic groups, seemed to always postdate the negative anomalies but coincide with the positive shift. If the negative excursions represented the oxidation of a large dissolved organic carbon (DOC) reservoir in the ocean, the diverse Ediacaran organisms and the carbon isotope anomalies may suggest totally different environments: oxic and anoxic/euxinic. We also suggest that the elimination of euxinic state through precipitation of pyrites is one of the important environment factors in prompting the Ediacaran bio-evolution.

关键词： Ediacaran South china carbon isotope spatio-temporal variations bio-evolution

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Nitrogen Isotopes from the Neoproterozoic Liulaobei Formation,North china:Implications for Nitrogen Cycling and Eukaryotic Evolution

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Journal of earth Science 2022年第5期33卷 1309-1319页

作者： Ting Yang Xinqiang wang Dongtao Xu {1. {2. Yongbo Peng school of {1. Science and {2. China University of GeosciencesBeijing100083China State Key Laboratory of Biogeology and Environmental Geology China University of GeosciencesBeijing100083China International Center for Isotope Effect Research Nanjing UniversityNanjing210023China school of {1. {2. and Engineering Nanjing UniversityNanjing210023China

The nitrogen isotope compositions(δ^(1.)N )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 *** considerableδ^(1.)N 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 ***,we report bulkδ^(1.)N and organic carbon isotope(^(δ)1.C_(org))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 {1. ***δ^(1.)N 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 positiveδ^(1.)N 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 *** study highlights the pivotal role of nutrient N in the evolution of eukaryotes.

关键词： Neoproterozoic Tonian Liulaobei Formation nitrogen isotopes eukaryotic evolution nutrient limitation geochemistry

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