Acanthomorph Biostratigraphic Succession of the Ediacaran Doushantuo Formation in the East Yangtze Gorges, South China
Acanthomorph Biostratigraphic Succession of the Ediacaran Doushantuo Formation in the East Yangtze Gorges, South China
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DOI：
10.1111/j.1755-6724.2011.00398.x
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发表时间：
2011-04
期刊：
影响因子：
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通讯作者：
C. Yin;Pengju Liu;S. Awramik;Shouming Chen;F. Tang;Linzhi Gao;Zi-qiang Wang;L. A. Riedman
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文献类型：
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作者：
C. Yin;Pengju Liu;S. Awramik;Shouming Chen;F. Tang;Linzhi Gao;Zi-qiang Wang;L. A. Riedman
在我国南方的湖北省长江三峡东部、贵州省瓮安等地的埃迪卡拉纪陡山沱组硅质岩中发现了大型棘状疑源类化石。然而，他们的潜力，埃迪卡拉纪继承的生物地层细分和对比是有限的相控制，埋藏的偏见，和分类问题。长江三峡地区陡山沱组可划分为四个岩性段。然而，在瓮安地区，陡山沱组仅包括由陡山沱中部侵蚀面分隔的下部和上部。在长江三峡漳村坪剖面，陡山沱序列与瓮安相似。到目前为止，长江三峡和瓮安地区以及其他地区之间的相关性一直是一个争论的问题。为了解决这一争论，我们在长江三峡地区选取了8个剖面，对陡山沱组的硅质结核进行了系统取样，特别是对陡山沱组上部进行了取样。我们的数据证实了两个不同的组合分别出现在第二和第三成员，这是由负δ 13 C偏移（EN 2）分开。下部组合以天柱山化石和一套大型刺形疑源类为特征。上组合与下组合的区别在于：（1）没有天柱山化石;（2）出现了丰富的100-150 μm的光滑壁球形微体化石;（3）出现了高度多样的棘形疑源类，包括从第二段延伸的种和该段的新变型;（4）出现了未命名的原生生物新变型;（5）管状微体化石Sinocyclocylicus guizhouensis的出现。由于澳大利亚没有以Tianzhushania为主的组合，似乎只有上部的棘状组合，因此在澳大利亚缺少下部的陡山沱棘状组合。
Large acanthomorphic acritarchs have been found in chert of the Ediacaran Doushantuo Formation at several localities in South China, including the East Yangtze Gorges of Hubei Province, Weng'an area of Guizhou Province, and elsewhere. However, their potential for biostratigraphic subdivision and correlation of Ediacaran successions is limited by facies control, taphonomic biases, and taxonomic problems. In the Yangtze Gorges, the Doushantuo Formation is generally subdivided into four lithologic members. However, in the Weng'an area, the Doushantuo Formation comprises just a lower and upper part separated by a mid‐Doushantuo erosional surface. In the Yangtze Gorges at the Zhangcunping section, the Doushantuo succession is similar to that at Weng'an. So far, the correlation between the Yangtze Gorges and Weng'an area, and elsewhere has been an issue of debate. To resolve the debate, we selected eight sections in the Yangtze Gorges area and systemically sampled chert nodules of the Doushantuo Formation, focusing in particular on the upper Doushantuo Formation. Our data confirm two different assemblages appearing separately in the second and third members, which are separated by a negative δ13C excursion (EN2). The lower assemblage is characterized by Tianzhushania and a diverse suite of large acanthomorphic acritarchs. The upper assemblage is distinguished from the lower assemblage, by (1) absence of Tianzhushania; (2) occurrence of abundant, 100–150 μm, smooth‐walled spherical microfossils; (3) occurrence of highly diverse acanthomorphic acritarchs including species extending from the second member and new forms in this member; (4) occurrence of unnamed new forms of protist; and (5) occurrence of the tubular microfossil Sinocyclocylicus guizhouensis. Since the Tianzhushania‐dominated assemblage is not present in Australia, it seems that only the upper acanthomorph assemblage is present and thus the lower Doushantuo acanthomorph assemblage is missing in Australia.