桂林唐家湾地区上泥盆统桂林组碳酸盐岩微相

广西桂林唐家湾地区上泥盆统桂林组发育8种微相类型,即灰泥岩、球粒-泥粒岩/颗粒岩、生物屑粒泥岩、棘皮-泥粒岩、枝状层孔虫-颗粒岩、层孔虫-棘皮-泥粒岩/颗粒岩、枝状层孔虫-棘度-泥粒岩/漂砾灰岩、鲕粒-球粒泥粒岩/颗粒岩。由于海平面变化及水体盐度变化形成3种沉积旋回类型。桂林组碳酸盐岩是在地形平坦的浅水台地或台隆上沉积的。由于受台盆相间的古地理格局的控制,只出现过短暂的风暴潮高能沉积,并导致生物组合分异度低。

FACIES OF UPPER DEVONIAN CARBONATES IN TANGJIAWAN PROFILE, GUILIN GUANGXI

This is a part of cooperative project between the Ministry of Geology and Mineral Resources of China and the Ministry of Science and Art of Niedersaehsen, Germany. Eight microfacies types exist in the Guilin Formation of Upper Devonian :i. e. mudstone, peloid-packstone/grainstone, Echinoderm-packstone, Amphipora-grainstone, Stromatopora-Echinoderm packstone/grainstone, Amphipora-Echinoderm packstone/floatstone, ooid-peloid-packstone/grainstone. Because of the change of sea level and salinity 3 types of sedimentary cycles occur. The carbonates of Guilin Formation were formed on the geomorphologically even platform of shallow water. The palaeogeographic framework characterized by a series of adjacent rises and troughs provided a restricted shallow water environment. Only some short time tempestites of higher energy existed. The evaporites and early diagenetic dolomites are absent in the Guilin Formation. This indicates that the shallow subtidal and tidal flat deposition underwent meteoric influence. And it is assumed for a humid subtropical climate. The separation of platforms and basins reveals a low fauna diversity.