The beginning of the Phanerozoic was marked by abundant phytoplankton,the occur-rence of animals and a newly established ecosystem structure,which in turn,resulted in different modes of organic matter(OM)cycling and preservation.In this study,we present an integrated paleontological and geochemical study of the Lower Cambrian Yanjiahe and Shuijingtuo formations in the Three Gorg-es area,South China.Rock samples were analyzed for major and trace elements,in order to evaluate the marine productivity.Fossil samples were recovered using palynological methods,destructive analytical techniques,SEM analysis and thin section microscopy.The organic-walled microfossils in the investigat-ed sections include marine microphytoplankton,linings of sponge spicules,small shelly fossils and some unnamed sheet-like and net-like microfossils(animal parts).Additionally,fecal structures and coprolites fossils were found.Three intervals in the Luojiacun Section were proposed to discuss the links among mi-crofossil assemblages and their influence on OM cycling and preservation.We found that the marine mi-crophytoplankton was the main source of OM in the investigated sections.The appearance of fecal struc-tures groups and massive appearance of animals in the pelagic zone indicate a higher transfer efficiency of OM aggregates through the water column.Oxygenated conditions in the water-column would have led to a moderate to low preservation of OM,an effect which would have been further enhanced by the po-tential presence of bioturbators.Overall,our study reveals the contribution of various organisms to the sedimentary OM and highlights the links and feedbacks among microfossil assemblages,OM recycling efficiency and OM preservation in the tipping point of the Phanerozoic"new world".

Shucan Zheng;Qinglai Feng;Sebastiaan van de Velde;Shan Chang;Lei Zhang;Bo Gao

School of Architectural Engineering,Huanggang Normal University,Huanggang 438000,China;State Key Laboratory of Geological Processes and Mineral Resources,School of Earth Sciences,China University of Geosciences,Wuhan 430074,China;Department of Earth and Planetary Sciences,University of California,Riverside,CA 92521,USA;Petroleum Exploration and Production Research Institute,SINOPEC,Beijing 100083,China

地球科学学刊（英文版）

[1]Shucan Zheng;Qinglai Feng;Sebastiaan van de Velde;Shan Chang;Lei Zhang;Bo Gao-.Microfossil Assemblages and Indication of the Source and Preservation Pattern of Organic Matter from the Early Cambrian in South China)[J].地球科学学刊（英文版）,2022(03):802-819

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