湖北宜昌樟村坪埃迪卡拉系陡山沱组C同位素变化及成因

以宜昌樟村坪地区万家沟和白鹭垭2个陡山沱组剖面为研究对象,开展了黄陵背斜北缘浅水沉积区埃迪卡拉系陡山沱组C稳定同位素研究。建立了黄陵背斜北缘陡山沱组C稳定同位素曲线,并识别出4次负漂移(ZN1~ZN4),3次正漂移事件(ZP1~ZP3)。其中3次负漂移可以全球对比,1次负漂移(ZN3)在峡东地区可以显著识别。确认了ZN4与DOUNCE事件的对应关系,且该区缺失峡东典型剖面陡山沱组四段。认为ZN1是全球性甲烷渗漏事件的反映;ZN2是区域性海平面下降的反映,与全球WANCE事件有很好的对应关系,而对应年代值要远比Gaskeris冰期时间早;ZN3应当是区域性洋流上升带来贫13C沉积物引起的;ZN4则可以非常好地用埃迪卡拉纪海洋有机碳库氧化来解释。

Carbon isotope variations and genetic analysis of the Doushantuo Formation of the Edia-caran system in Zhangcunping,Yichang

For the purpose of systematic analysis of the Ediacaran carbon stable isotope curve from the shallow marine facies Doushan-tuo Formation on the northern limbs of the Huangling anticline,the authors chose Zhangcunping and Bailuya sections in Yichang of Hubei Province as the study objects.The results indicate that four remarkable negative (ZN1~ZN4) and three positive carbon isotope anomalies (ZP1~ZP3) exist in the strata.As for negative excursions,the three negative carbon isotope excursions could be compared well with those from the other global typical sections;and the other one could be well recognized in eastern Yangtze Gorges.Further-more,it is held that ZN4 corresponds to DOUNCE event and the typical fourth member of Doushantuo Formation section has not been deposited in the area;ZN1 is a reflection of the global methane leakage incident;ZN2 was caused by regional lowered sea level,which was mich earlier than the Gaskeris glaciation and could be correlated with WANCE event;ZN3 resulted from the regional up-welling,which carried ¹³C depleted organic materials from deep ocean;ZN4 can be explained by the oxidation of organic carbon pool of the Ediacaran Ocean.