REE and trace element patterns from organic-rich rocks of the Ediacaran–Cambrian transitional interval |
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| Institution: | 1. Institute of Geographic Science and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China;2. Key Laboratory of Marine Mineral Resources, Guangzhou Marine Geological Survey, Ministry of Land and Resources, Guangzhou 510075, China;3. Institute of Applied Geosciences, Technical University Berlin, Ackerstr. 76, 13355 Berlin, Germany;4. Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China;1. State Key Laboratory of Biogeology and Environmental Geology, Beijing 100083, China;2. School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China;3. Science Research Institute, China University of Geosciences, Beijing 100083, China;1. School of Energy Sources, China University of Geosciences, Haidian, Beijing 100083, China;2. Key Laboratory of Marine Reservoir Evolution and Hydrocarbon Accumulation Mechanism, Ministry of Education, China University of Geosciences, Beijing 100083, China;3. Department of Geology, University of Cincinnati, Cincinnati, OH 45221-0013, USA;4. State Key Laboratories of BGEG and GPMR, China University of Geosciences, Wuhan 430074, China |
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| Abstract: | It has been established that important changes in the marine environment and the biosphere occurred during the Cambrian. However, the relationships between the so-called “Cambrian Explosion” and the concomitant environmental changes are not yet fully understood. This study presents new geochemical data from the black shale successions from different facies belts of the Yangtze Platform in South China. Variations in the concentrations of REE and trace elements (varying Ce/Ce*, Th/U, V/Sc, and V/Cr ratios) in kerogen as well as in bulk rocks from different depositional environments along a transect from platform to basin indicate two oxidation events, which led to the oxygenation of the water column in shallow-marine environments and euxinic conditions (weak correlation between TOC, V, U, and Mo) in the deeper sea. During the first oxidation event in the late Terreneuvian, anoxic conditions in bottom waters rapidly changed to euxinic conditions. Subsequently, the second oxidation event during the early Epoch 2 of the Cambrian led to oxic–suboxic conditions in deeper seawater. |
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