扬子区奥陶纪末赫南特亚阶的生物地层学研究

Biostratigraphy of the Hirnantian Substage in the Yangtze Region

重新研究了宜昌王家湾 ,宜昌分乡 ,桐梓红花园和松桃陆地坪 4条上奥陶统上部至志留系底部的连续采集剖面。1999年 6月在捷克召开的第 8届国际奥陶系大会上提名宜昌王家湾和桐梓红花园剖面分别为赫南特亚阶的全球层型候选剖面 (GSSP)和辅助剖面。对赫南特亚阶及其上、下地层的生物带重新厘定 ,自下而上为 Foliomena-N ankinolithus/D.complanatus,D.complexus带 ,P.pacificus带 (包括下部亚带 ,T.typicus亚带和 Diceratograp-tus mirus亚带 ) ,N.extraordinarius- N.ojsuensis带 ,N.persculptus带 ,A.ascensus带和 P.acuminatus带。

Ashgill to early Llandovery strata are distributed widely on the Yangtze Platform where they crop out in many continuous sections. Since 1995, we have recollected a variety of fossils from four critical sections, bed by bed, at Wangjiawan and Fenxiang (Yichang, W Hubei) as well as Honghuayuan (Tong zi, N Guizhou) and Ludiping (Songtao, NE Guizhou). We consider the Wangjiawan and Honghuayuan sections as the two most important because they represent contrasting deeper and shallower water facies types, respectively, in the Hirnantian. These two sections are proposed here as a candidate stratotype and auxiliary section for the Hirnantian Substage respectively. The biozones within the interval between Ashgill to earliest Llandovery in descending order are as follows: Parakidograptus acuminatus Zone Akidograptus ascensus Zone [BHDWG1*2,WK26ZQ0,KZQ1W] Normalograptus persculptus Zone Hirnantia Normalograptus extraordinarius N. ojsuensis Zone fauna Paraorthograptus pacificus Zone Diceratograptus mirus Subzone Tangyagraptus typicus Subzone Lowere Subzone Dicellograptus complexus Zone Foliomena Nankinolithus/Dicellograptus complanatus Zone