[Objective]The Neoproterozoic Struttin Glaciation(～717-660 Ma)developed widely across the world and was well recorded in the Nanhua Basin,but the study of carbon cycling during this period is lacking.To investi-gate the carbon cycle process during the Sturtian Glaciation,the carbon isotope compositions of the Tiesi'ao Forma-tion precipitated during the glacial interval were systematically studied.[Methods]This study focuses on drillcore ZK2115,located in Gaodi Manganese Deposit,Songtao area,eastern Guizhou province,China.We analyzed high-resolution organic and inorganic carbon isotopes(δ13Corg and δ13Ccarb)from the syn-Sturtian Tiesi'ao Formation.[Results]The results show that the Tiesi'ao Formation is characterized by negative carbon isotope excursions,rang-ing between-9.29‰ and-3.37‰(mean-7.24‰).The δ13Corg values vary between-33.63‰ and-23.35‰(mean-29.29‰).There is a positive correlation between the δ13Corg and δ13Ccarb values,indicating that the inorganic carbon isotope compositions are not affected by diagenesis and can be used to reflect the original carbon isotope signals of the Dissolved Inorganic Carbon(DIC)reservoir in the Nanhua Basin.Organic matter preserved in the Tiesi'ao Formation was generated through photosynthesis,and the carbon fixed in the organic matter was sourced from the DIC reservoir in seawater.[Conclusions]Combined with the low Total Organic Carbon(TOC)content(mean 0.2%)of the Tiesi'ao Formation,our results indicate that photosynthesis still occurred under the extreme glacial conditions at a low rate,although only a small amount of organic matter was generated.The study of carbon isotope compositions in glacial sediments can be used to explore carbon cycling during the Sturtian Glaciation,and to provide evidence for the paleo-marine environment and biogeochemical cycle under extreme climatic conditions.
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