| 浙西开化上奥陶统复理石中的环形迹 |
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| 引用本文： | 夏邦栋,吕洪波,熊斌辉,何永明,胡宝生.浙西开化上奥陶统复理石中的环形迹[J].沉积学报,1987,5(2):71-80. |
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| 作者姓名： | 夏邦栋 吕洪波 熊斌辉 何永明 胡宝生 |
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| 作者单位： | 南京大学地质系 |
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| 摘 要： | 开化环形迹产于浙西开化上奥陶统复理石中,为发育于泥质岩顶面的椭圆形多圈水平旋槽,一般3-5圈。椭圆长轴可达35厘米,短轴可达18.5厘米。椭圆个体之长轴均沿北东方向平行分布,且和古水流方向一致,是造迹动物在水底觅食时选取最佳方向以减小水流推力所致。痕迹化石和大量的浅海沉积构造共生,说明痕迹产生于浅水环境。
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| 关 键 词： | 开化环形迹 复理石 上奥陶统 浅海 |
SPIRODESMOS KAIHUAENSIS IN THE UPPER ORDOVICIAN FLYSCH IN THE KAIHUA COUNTY,WEST PART OF ZHEJIANG PROVINCE |
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| Institution: | Department of Geology, Nanjing University |
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| Abstract: | The Yuqian group (or Changwu group) in the west part of Zhejiang province is a set of flysch formation with thickness about 2,000m, in which many kinds of trace fossils are found. In this paper, we only discuss the new species ( Spirode-smos kaihuaensis ) found in kaihua County ( Fig. l ). Spirodesmos kaihuaensis, distributed along the bedding surface, is elliptical, multi-annular, with 3-5 rings. The major axis( A) of the ellipse is up to 35cm, the minor axis ( B ) is up to 18.5cm, and ratio ( A/B ) is about 2. All of the major axis of the elliptical traces are parallel to each other in the NE direction. The authors consider that the traces were produced by some animals which have no hard shells. The animals ploughed sediments in a round way, depending on their innate thigmotaxis and strophotaxis and developing the ringlike traces when they were looking for food. The major axes of the elliptical trace are parallel to the direction of water flow as a result of the pushing force of water flow on the organism, the animals prefered to move in the direction parallel to the water flow rather than perpendicular to it so as to reduce the pushing force of water flow. The trace fossils coexist with many kinds of sedimentary structures, such as symmetric wave marks, interference wave marks, foreset beddings, lenticular beddings etc. , showing a shallow water environment. From all kinds of data, authors concluded that Spirodesmos Kaihuaensis was formed in a subtidal zone of a gulf, which was situated in the north side of the southwest part of the Early palaeozoic sedimentary basin in the west part of Zhe-jiang province. This area was near to an old land which supplied an abundence of organic matter to the basin. In the area there existed a bottom current with lower kinetic energy, flowing in a uniform direction. The water bottom was influenced by wave accasionally. Such an environment benefited trace fossils. |
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