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Fig. 8 | Progress in Earth and Planetary Science

Fig. 8

From: Authigenic carbonate precipitation at the end-Guadalupian (Middle Permian) in China: Implications for the carbon cycle in ancient anoxic oceans

Fig. 8

Schematic diagram representing differences in the form of authigenic carbonate precipitation between the oxic and anoxic oceans, proposed in this study. In the oxic oceans, the redoxcline is generally below the sediment–water interface and a small amount of authigenic carbonate is generated within the sediments. The δ13Ccarb value of the carbonate is relatively low as a result of weak mixing between the remineralized carbon released from sedimentary organic matter and seawater DIC. In contrast, in the anoxic oceans, the redoxcline is above the sediment–water interface and large amounts of authigenic carbonate precipitate near the seafloor. The δ13Ccarb value of the carbonate is relatively high due to the strong mixing of remineralized organic carbon and the large DIC pool in the water column. Ω the carbonate saturation index

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