The positive S-isotopic excursion of carbonate-associated sulfate (δ34SCAS) is generally in phase with the Steptoean positive carbon isotope excursion (SPICE), which may reflect widespread, global, transient increases in the burial of organic carbon and pyrite sulfate in sediments deposited under large-scale anoxic and sulphidic conditions. However, carbon-sulfur isotope cycling of the global SPICE event, which may be controlled by global and regional events, is still poorly understood, especially in south China. Therefore, the δ13CPDB, δ18OPDB,δ34SCAS, total carbon (TC), total organic carbon (TOC) and total sulfate (TS) of Cambrian carbonate of Waergang section of Hunan Province were analyzed to unravel global and regional controls on carbon-sulfur cycling during SPICE event in south China.
The δ34SCAS values in the onset and rising limb are not obviously higher than that in the preceding SPICE, meanwhile sulfate (δ34SCAS) isotope values increase slightly with increasing δ13CPDB in rising limb and near peak of SPICE (130–160 m). The sulfate (δ34SCAS) isotope values gradually decrease from 48.6‰ to 18‰ in the peak part of SPICE and even increase from 18‰ to 38.5% in the descending limb of SPICE. The abnormal asynchronous C-S isotope excursion during SPICE event in the south China was mainly controlled by the global events including sea level change and marine sulfate reduction, and it was also influenced by regional events such as enhanced siliciclastic provenance input (sulfate), weathering of a carbonate platform and sedimentary environment. Sedimentary environment and lithology are not the main reason for global SPICE event but influence the δ13CPDB excursion-amplitude of SPICE. Sea level eustacy and carbonate platform weathering probably made a major contribution to the δ13CPDB excursion during the SPICE, in particularly, near peak of SPICE. Besides, the trilobite extinctions, anoxia, organic-matter burial and siliciclastic provenance input also play an important role in the onset, early and late stage of SPICE event.