石炭系全球界线层型研究进展

ACHIEVEMENTS IN THE ESTABLISHMENT OF THE CARBONIFEROUS GSSPs

早石炭世晚期开始的全球大规模构造运动和冈瓦纳大陆的冰川,为石炭系的地层划分和对比带来了困难。通过国际石炭系分会的努力,近年来石炭系各阶的界线层型研究取得了显著的进展。维宪阶已有了古生物学界线定义,即有孔虫Eoparastaffella simplex的首现,其余各阶也有了意向性的界线定义,它们均以牙形刺作为主导化石类群。其中,谢尔普霍夫阶以L ochriea ziegleri的首现为底界;莫斯科阶以Idiognathoides postsulcatus或Declinognathodus donetzianus的首现为底界;卡西莫夫阶的底界为Idiognathodus sagittalis的首现层位;格舍尔阶的底界是Idiognathodus

Great achievements have been obtained recently in seeking for GSSPs within the Subcommission on Carboniferous Stratigraphy although many difficulties caused by the onset of the moderate- to high-amplitude glacial-eustatic sea level changes characteristic of the Late Misissippian and Pennsylvanian. The Task Group for the Tournaisian-Visean boundary is now in the final stage of submitting an official propo- sal to the SCCS after the boundary-defining taxon was formally approved in 2002. Other task groups have also had unambiguous work plans in searching for fossil event markers. The evolutionary appearance of a taxon in a lineage within the Lochriea group of species could be suitable for defining a GSSP close to the current Visean-Serpukhovian boundary. Two independent conodont events, namely the evolutionary origin of Declinognathodus donetzianus from D. marginodosus and the evolutionary origin of Idiognathoides postsulcatus from I. sulcatus are in high potential in defining the Bashkirian-Moscovian boundary. The short range and worldwide distribution of the conodont Idiognathodus sagittalis make its first appearance a significant candidate for the biostratigraphic marker level for the correlation of the Moscovian-Kasimovian boundary. Conodont Idiognathodus simulator is possibly a marker taxon at the base of the Gzhelian.