瓜德鲁普统(Guadalupian)-乐平统(Lopingian)全球界线层型剖面和点(GSSP)

乐平统底界全球界线层型(GSSP)已经被确定在中国广西来宾县的蓬莱滩剖面,这一界线以牙形类化石Clarkina postbitteri postbitteri Mei&Wardlaw的首次出现为标志,位于蓬莱滩剖面的茅口组顶部来宾灰岩的6k层之底,层型剖面点位于C.postbitter hongshuiensis至C.dukouensis的演化谱系内,大致与阿布萨罗卡巨层序(Absaroka Megasequenses)的中部与上部之间的界线相当。层型剖面点位所在的来宾灰岩代表了一套界于茅口组和合山组之间的低水位沉积,在这一界线附近,类、腕足类、珊瑚类和菊石类等动物群均发生了重大更替;同时,δ13C值和87Sr/86Sr同位素比值也有一个明显的降低。从瓜德鲁普世晚期的磁性正常极性带向吴家坪早期反向极性带的转变也发生在这一界线附近,因此,这一界线可以很好地用于进行全球海陆相地层的对比。

THE GLOBAL STRATOTYPE SECTION AND POINT (GSSP) FOR THE BOUNDARY BETWEEN THE GUADALUPIAN AND LOPINGIAN SERIES (PERMIAN)

The Global Stratotype Section and Point (GSSP) for the boundary between the Capitanian and Wuchiapingian stages, also the boundary between the Guadalupian and Lopingian Series is defined at the First Appearance Datum (FAD) of the conodont Clarkina postbitteri postbitteri at the base of Bed 6k in the Penglaitan Section along the Hongshui River in Guangxi, South China. This point is within a chronomorphocline from Clarkina postbitteri hongshuiensis to C. dukouensis and nearly coincides with the Middle-Upper Absaroka Megasequence boundary and as such is documented within a continuously deposited carbo-nate lowstand succession with deep-water facies of the Maokou Formation below and deep-water facies of the Heshan Formation above. Furthermore, this point also coincides with a major extinction of various Permian fossils including ammonoids, brachiopods, corals, and fusulinaceans. The proximity to an appa-rently global major sequence boundary and extinction event will serve as a means of correlation of this GSSP into other regions in which the defining taxon is not present because of profound provincialism du-ring the Middle and Upper Permian. Carbon isotopic trends and magnetostratigraphic signatures are also provided to help correlate this GSSP into other regions, including those with continental facies successions. The Tieqiao Section near the county town of Laibin is also described as a supplementary reference section.