| 桂林附近中泥盆统东岗岭组发现生物礁 |
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| DISCOVERY OF BIOHERM IN DONGGANGLING FORMATION OF MIDDLE DEVONIAN NEAR GUILIN, GUANGXI |
| 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. |
| WENG Jin-tao,LUO Gui-rong.1983.DISCOVERY OF BIOHERM IN DONGGANGLING FORMATION OF MIDDLE DEVONIAN NEAR GUILIN, GUANGXI[J].Acta Geoscientica Sinica,5(1):. |
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