黔中新元古代-早寒武世含磷岩系δ^(13)C变化及其古海洋意义

δ^(13)C Excursions of Phosphorite-bearing Rocks in Neoproterozoic-Early Cambrian Interval in Guizhou,South China:Implications for Palaeoceanic Evolutions

通过对贵州瓮安大塘剖面和织金戈仲伍剖面含磷地层的碳同位素研究,探讨了新元古代-早寒武世过渡时期含磷岩系的成因及其古海洋意义.研究结果表明,新元古代Marinoan冰期结束后沉积的盖帽碳酸盐岩、上覆的磷块岩,以及早寒武世戈仲伍组磷块岩的δ13C负异常,是上升洋流将深海13C“耗尽”的有机质携带到浅水区域沉积所致.此外,深部洋流上涌,不但导致了δ13C负漂移,而且为磷块岩沉积提供了磷质来源.

Carbon isotopic compositions of carbonate in phosphorite-bearing rocks in Weng＇an Datang Section and Zhijing Gezhongwu Section in Guizbou, South China were studied to better understand the genesis of phosphorites and coeval palaeoceanic evolutions. The research results indicates that the negative δ^13C anomalies of the ＂cap carbonate＂ deposited soon after the termination of Neoproterozoic Marinoan glaciation, the overlying pbosphorites, as well as the phospborites in Early Cambrian Gezbongwu Formation are resulted from the upwelling, which carried ^13C depleted organic materials from deep ocean and then deposited as carbonate or phosphorite in shallow water areas. The upwelling of deep seawater not only contributed to the negative δ^13C excursions, but also provided phosphorus sources to phosphorite.