A sedimentary environment analysis of black shales based on fossil assemblage characteristics:A case study of Cambrian Niutitang Formation in Changyang area, western Hubei
A sedimentary environment analysis of black shales based on fossil assemblage characteristics:A case study of Cambrian Niutitang Formation in Changyang area, western Hubei
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发表时间：
2013
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通讯作者：
Zhao Ming-shen
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作者：
Zhao Ming-shen
鄂西地区寒武系地层分布广泛。湖北省长阳县天祝地区寒武系牛蹄塘组下部黑色碳质页岩中发现了大量的Sunella（Bradoriida）、Perspicaris（大型双壳节肢动物）、宏观藻类、hyolithes和（？）Sinospongia（可疑海绵）。此外，黑色页岩中还可见分散的黄铁矿。通过对古生态和化石保存特征的详细研究，得出鄂西长阳县牛蹄塘组沉积早期，宏观生物生活在浅水环境中，底部缺氧，上部好氧，透光性好，相对平静，海底表面位于氧化还原界面附近。此外，在快速沉积的背景下，页岩中嵌入了大量的水和死去的生物体，沉积水与外界水的水交换量逐渐减少，沉积过程中腐烂生物产生H2S气体，在沉积物中形成强烈的还原环境，使有机质得以保存，最终形成黑色页岩。
The Cambrian strata are widely distributed in western Hubei area. Abundant Sunella(Bradoriida), Perspicaris(large bivalved arthropods), macroscopic algal, hyolithes and(?)Sinospongia(Suspicious sponges) have been found in the lower black carbonaceous shale of the Cambrian Niutitang Formation from Tianzhu area of Changyang County, Hubei Province. In addition, scattered pyrite is seen in black shale. Based on a detailed study of palaeoecology and the characteristics of fossils preservation,the authors have reached the conclusion that, during the early sedimentary stage of Niutitang Formation in Changyang County of western Hubei Province, macro organism lived in an environment of shallow water which was suboxic at the bottom, oxic in the upper part characterized by good light transmission and relative calmness, and that the sea bottom surface was located nearby the redox interface. Besides, under the background of rapid deposition, large amounts of water and dead biological-bodies were embedded in shale, the amount of water exchange between the depositional water and the external water decreased gradually, and H2 S gas was generated by rotton organism in the process of deposition, forming a strong reduction environment in sediments, so that organic matter could be preserved, which eventually formed black shale.