| 桂林附近中泥盆统东岗岭组发现生物礁 |
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| 引用本文：翁金桃,罗贵荣.1983.桂林附近中泥盆统东岗岭组发现生物礁[J].地球学报,5(1):. |
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| 中文摘要:<正> 在桂林南郊约九公里、唐家湾公路以北约300米处的中泥盆统东岗岭组下部有一个碳酸盐岩隆,其两侧岩层产状相反,上面被一水平岩层覆盖。过去都认为其下部为一个小型背斜构造,其上部的水平岩层是逆掩断层造成的。 1980年底,笔者在该岩隆中发现了大量造礁生物,含量多达60—80％。1981年以来我们对该地碳酸盐岩进行了详细的野外工作和室内研究。除了在岩隆顶部上覆岩层中见到一组垂直层面的破劈理外,没有发现明显的断裂构造现象;岩隆两侧岩层产状的不同实系礁体两翼的原始倾伏;在岩隆内部找到了几个斑礁块体及造礁生物原地生长的痕迹和生物包裹构造等。 |
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| DISCOVERY OF BIOHERM IN DONGGANGLING FORMATION OF MIDDLE DEVONIAN NEAR GUILIN, GUANGXI |
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| Abstract:In 1980, an organic reef was found to the north of Tangjiawan Road on the southern suburbs of Guilin, Guangxi. Field and laboratory studies made it clear to be as the lower part of the Middle Devonian Donggangling Formation (D_22) and in more detail, an organic bank reef-acomplex of knoll and patch reefs developed on. an organic bank. This organic bank reef erects like a dome, with an outcrop of 60 mthick and a latitudinal width of 300 m (hence a ratio of about 1:5 between them). The strata at its western flank dip NW, thofe at estern dipSE, and all have a dip angle of 20-25°.The strata in the reef core dipnorthward with angle of 10-15°. Its main building organisms are spherical, semispherical or pear form Stromatopora, Tabulata and Tetracoralla. Sixty to eighty per cent of its total is made up of organisms with skeletal structure.The stromatoporas have an average size of 20 cm, with a few exceptions expanding to40 cm. Although most of them were displaced, quite a large quantity ofpear form ones keep an upgrowth in their original places, and somesemispherical ones are marked by a lateral or upward growth. (Actinostroma clathratum Nicholson, Gerronostroma Kitatense Yavorsky,…) TheTabulatas and Tetracorallas have both colonial and solitary forms. Thecolonial corals take the shape of massive, branching and cluster, and often have an enclosed structure within stromatoporas. (Sanophyllum sp.,S. typicum wang,…) Brachiopods and Gastopods are the chief organismsattached to the reef. It is an uplifted reef, the lithology of which is characterized by medium thin-bedded biomicrite in the base, patched or brecciated calcicdolomite at the flanks, mottled dolomite at the top, and a reef cap ofbranched Amphipora micritic limestones derived from lagoonal sediments. It could be concluded that the bank reef was formed at the beginning of late Middle Devonian when reef-building organisms like stromatopora and corals were flourishing, under the strong hydrodynamic condition, on the windward side of the submarine domes dotted on the carbonate platform. |
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