Conodont evolution and stratotype sign of carboniferous Tournaisian-Visean boundary in South China
Conodont evolution and stratotype sign of carboniferous Tournaisian-Visean boundary in South China
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DOI：
10.1360/04yd0223
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发表时间：
2005-12
期刊：
影响因子：
--
通讯作者：
Shugang Tian;M. Coen
中科院分区：
文献类型：
--
作者：
Shugang Tian;M. Coen
根据华南地区剖面沉积学、牙形石相和牙形石成因的研究，提出了中国南方杜奈阶-维先阶界线的层型剖面、界线点和牙形石标志。选取了代表扬子板块边缘和内部的两个区域和三个不同相带，即广西柳州龙甸山台地相带、云南施甸玉洞斜坡相带和广西柳州彭冲盆地相带。通过对碳酸盐岩相和旋回的系统研究，建立了两地区的地层格架。通过对牙形石的种类、数量、丰度的统计，研究了牙形石的相分布和古生态条件，并选择了一种分布广泛的亚热带牙形石--有颌类，从中筛选出标志化石，通过统计和过渡型研究，补充或建立了7个牙形石谱系。早石炭世牙形刺的演化可划分为3个阶段，即Siphonodella阶段、Gnathodus typicus阶段和Gnathodus bilineatus阶段。后两个阶段之间的转换面可作为图尔奈期-维先期界线。最后，本文提出彭冲剖面可作为杜奈阶-维先阶界线的层型候选者，界线点应置于58层底部，牙形石层型标志应为Gnathodus semiglaber分支的Gnathodus praebilineatus的首次出现。
A stratotype section, boundary point and conodont sign have been recommended for GSSP of the Tournaisian-Visean boundary, based on studies of sectional sedimentology, conodont facies and phylogeneses in South China. Two areas representing margin and inner of the Yangtzi Plate and three sections of different facies were chosen, i.e. the Longdianshan section of the platform facies in Liuzhou of Guangxi, the Yudong section of the ramp facies in Shidian of Yunnan and the Pengchong section of the basin facies in Liuzhou of Guangxi. Stratigraphic frameworks of two areas were set up by systematical studies of carbonate facies and cycles. Conodont facies-distribution and paleoecologic conditions were researched on statistics of fossil variation and richness, and a kind of planktonic conodont, gnathodids that were widespread, is chosen to select the sign-fossil from it. Seven conodont pedigrees were supplemented or erected by studies of statistics and transitional forms. Conodont evolution in the Early Carboniferous could be divided into three stages, i.e. the Siphonodella stage, the Gnathodus typicus stage and the Gnathodus bilineatus stage. The transform-surface between the later two stages could be put as the Tournaisian-Visean boundary. Finally, this paper proposes that the Pengchong section can be the stratotype candidate of the Tournaisian-Visean boundary, the boundary point be put at the bottom of bed 58 and the stratotype sign of conodont be the first occurrence of Gnathodus praebilineatus of the Gnathodus semiglaber branch.