平果地区孤立碳酸盐台地风暴特征及展布规律

FEATURES AND DISTRIBUTION LAW OF TEMPETITE IN THE ISOLATED CARBONATE PLATFORM OF PERMIAN TO LOWER TRIASSIC, PINGGUO, GUANGXI PROVINCE

广西平果地区二叠纪,早三叠世发育了众多的孤立碳酸盐台地。孤立碳酸盐台地内的风暴岩至少可分出三类。Ⅰ类由下亚段粒序层和上亚段具叶状藻灰泥岩或具遗迹化石灰泥岩组成,形成在高能风暴流条件下.Ⅱ类由下亚段粒序层,中亚段纹层段和上亚段灰泥岩组成,其形成水能较Ⅰ类弱.Ⅲ类由具定向生物化石的泥粒岩组成,它是风暴流到达台地边缘后产生的回流形成的。不同类型风暴岩形成于不同环境。孤立碳酸岩台地上的风暴岩与开阔陆架风暴岩有一定差别.

Many isolated carbonate platforms were developed from Permain to Early Triassic in Pingguo arca.The tempctite in the isolated carbonate platform can be divided into at least three types.Type I is generally composed of graded bedding limestone in its lower subdivision and mudstonc with phylloin or trace fossils in the upper subdivision.This type of tempctite was formed under the condition of high energy storm current. Type II is compascd of graded bedding in the lower subdivision,wave ripple-cross-lamination in the middle subdivision and mudstone in the upper subdivision.The water energy of forming Type II is weaker than that of Type I .Type HI is composed of wackstone with many directional fossils.The case of this type is due to back current which was formed when storm current reached the platform rim. Different types of tempetitc were formed in different environments of the isolated platform. It must be pointed out that the tempctite in the isolated carbonate platform is different from that of continental sheft.