广西中部二叠系乐平统层序地层研究

通过对分别位于台地、斜坡和盆地的广西合山马滩剖面、来宾铁桥剖面和来宾蓬莱滩剖面的廊带式追索研究，将二叠系乐平统地层自下而上划分为Ｌｐ１、Ｌｐ２、Ｌｐ３、Ｌｐ４、Ｌｐ５和Ｌｐ６６个三级层序，并建立了相应的海平面变化曲线。结合原有和最新的生物地层资料，对这３个剖面的层序地层划分实现了精确对比，从而将原有地层对比精度提高了１倍。主张以牙形石Ｃｌａｒｋｉｎａｓｕｂｃａｒｉｎａｔａ的初现作为长兴阶和吴家坪阶的分界，这一界线与上述三级层序Ｌｐ６的首次海泛面一致。长期被当作长兴阶下部带化石的Ｇａｌｏｗａｙｉｎｅｌａｍｅｉｔｉｅｎｅｎｓｉｓ和Ｐａｌａｅｏｆｕｓｕｌｉｎａｍｉｎｉｍａ可向下延入依据牙形石定义的吴家坪阶。

SEQUENCE STRATIGRAPHY OF PERMIAN LOPINGIAN STRATA IN CENTRAL GUANGXI

The uppermost Yangsingian and Lopingian strata in central Guangxi is subdivided into one second order sequence, namely the Leping Sequence, and its six component third order sequences, and the corresponding sea level change curves are established, based on a comparative study on a carbonate platform section, namely the Matan Section at Heshan, a slope section, namely the Tieqiao Section at Laibin and a basinal section, namely the Penglaitan Section to the east of Laibin. The third order sequences are named in ascending order as Lp1, Lp2, Lp3, Lp4, Lp5 and Lp6. Precise correlation of these sequences among these three sections is realized, with aid of renewed biostratigraphic data. As a result,the resolution of previous correlation is raised by at least two times. It is suggested to define the Wuchiapingian Changhsingian boundary by the first appearance of a conodont species, i.e., Clarkina subcarinata. This horizon is found to be in accordance with the first flooding surface of the third order sequence Lp6. Gallowayinella meitienensis and Palaeofusulina minima , which have long been regarded as typify of the lower Changhsingian, are found ranging into the underlying Wuchiapingian.