| 广西泗顶泥盆系上统融县组中核形石的类型及其环境意义 |
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| 引用本文： | 曾允孚,张锦泉,林文球,叶亚平.广西泗顶泥盆系上统融县组中核形石的类型及其环境意义[J].沉积学报,1983,1(1):42-49. |
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| 作者姓名： | 曾允孚 张锦泉 林文球 叶亚平 |
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| 作者单位： | 成都地质学院 |
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| 摘 要： | 广西泗顶泥盆系上统融县组中含有丰富的核形石,通过岩相剖面,100多块核形石手标本及50多块核形石薄片,对核形石的形态、纹层和核心等特征进行了详细的研究。核形石是由含粘液的藻类生长并捕获和粘结沉积物围绕核心而形成的颗粒。核形石的形态及纹层特征能反映它形成的条件。核形石不限定在动荡环境,如帽状、花瓣状核形石形成于浅水低能间歇性弱搅动的沉积环境。核形石的堆积环境与形成环境可以一致,也可以不一致。
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| 收稿时间： | 1982-04-13 |
TYPES AND ENVIRONMENTAL SIGNIFICANCE OF ONCOIDS FROM YONGXIAN FORMATION OF THE UPPFR DEVONIAN IN SIDING,GUANGXI |
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| Institution: | Chengdu College of Geology |
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| Abstract: | Oncoids occur abundantly in the calcarenite and the pelletal limestone in the lower part of the third limestone member from Yongxian formation of the upper Devonian in Siding, Guangxi. The content of the oncoids is about 15-30%. They are mostly elliptical bodies with diameters ranging from 0.5 to 2 cm, even up to 65 cm in maximum. On the basis of the microscopic study, they are all of algal origin. They are mainly of four species such as algae-Ortonell sp, Mitcheldeania sp, Rothopletzella sp and Lithophyllum sp. Four main types of internal laminae of the oncoids may be recognized: ( 1 ) micritic lamina, ( 2 ) grumose lamina, ( 3 ) organism-bearing lamina and ( 4 ) algal lamina. They were basically formed by micritic and algal lamina surrounding an intraclast or a bioclast, or by the interlayers of micritic, grumose and algal lamina surrounding a bioclast or an intraclast. According to the characteristics of the shapes,they may be divided into the cap-form, petal-form and subellipsoidal-form. The laminae of cap-form grew upward so as to pile up and those of petal-form grew irregularly. They were all formed into inconsecutive laminae.The laminae of subellipsoidal-form grew continuously. The growth of the laminae was controlled by the movement of water body. The algae always grew towards the sunshine. If the water body persisted in agitation and oncoids turned over continuously, the oncoids formed continuous laminae. If the water body agitated weakly and oncoids rested or turned over intermittently, the oncoids formed inconsecutive laminae. Thus the oncoids of cap-form and petal-form were formed in the environment of shallow water with weak agitation and low energy. The oncoids of subellipsoidal-form were formed in the environment of persistent agitation and high energy. Oncoids of cap-form and petal-form mainly occur in pelletal limestone and subellipsoidal-form ones occur in calcarenite.It is suggested that the environment of the formation of the oncoids coincided with that of accumulation. |
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