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湖北宜昌三峡地区埃迪卡拉系-寒武系界线位置尚存争议,跨越这一界线的岩家河组地层的分段工作也缺乏统一的意见。对岩家河剖面开展岩相学和碳同位素地层学研究,揭示其碳同位素演化可与扬子板块内滇东北老林剖面和肖滩剖面对比,即自下而上在该界线附近存在一个大的δ13C负漂移、一个稍小的δ13C负漂移和一个大的δ13C正漂移。结合该剖面小壳化石首次出现的层位位于碳同位素大的负漂移之上的生物地层学证据,建议将埃迪卡拉系-寒武系界线置于δ13C大负漂移顶部和小壳化石出现层位的底部。埃迪卡拉系-寒武系界线附近的这一负漂移具有全球对比性,可作为三峡地区乃至全球范围内埃迪卡拉系-寒武系界线划分的标志之一。此外,根据碳同位素演化、岩石地层学和小壳化石资料以及与板块内滇东北地层剖面的对比,将岩家河剖面岩家河组划分为3段,它们分别相当于滇东北的朱家箐组的待补段、中谊村段和大海段。
There is still controversy about the location of the Edicar-Cambrian-Cambrian boundary line in the Three Gorges area of Yichang, Hubei Province. There is also a lack of consensus on the staging of the Yanjiahe Formation across this boundary. The study of lithofacies and carbon isotope stratigraphy on the Yanjiahe section reveals that the carbon isotope evolution can be compared with the Laoling section and the Xiaotan section in the northeastern Yunnan and Yunnan provinces in the Yangtze Plate, that is, there is a large δ13C near the boundary from the bottom up Negative drift, a slightly negative δ13C drift and a large δ13C positive drift. Combined with the biostratigraphic evidence that the first occurrence of small shell fossils in this section lies above a large negative excursion of carbon isotopes, it is suggested that the Edicala-Cambrian boundary be placed at the top of δ13C large negative drift and the appearance of small shell fossils The bottom of the bit. This negative drift near the Edicala-Cambrian boundary is globally comparable and can be used as one of the hallmarks of the Edicala-Cambrian boundary division in the Three Gorges area and globally. In addition, according to the carbon isotope evolution, lithostratigraphy and small shell fossil data, and the comparison with the northeastern Yunnan and Yunnan stratigraphic sections, the Yanjiahe Formation of the Yanjiahe Section is divided into three sections, which are respectively equivalent to the Zhujiawan Formation in Northeast Yunnan To be complements, in the village section and the sea section.