吉林大阳岔及其邻近地区奥陶纪最早期笔石的序列与对比

The sequence and correlation of the earliest Ordovician graptolites from Dayangcha and its surrounding area,Jilin Province,China

在前人研究的基础上，通过对吉林大阳岔及其邻近地区寒武系—奥陶系剖面的笔石研究，修正了该地区奥陶纪最早期（特马豆克期）的笔石序列，自下而上分为４个笔石带：１）Ｒｈａｂｄｉｎｏ－ｐｏｒａｆｌａｂｅｌｉｆｏｒｍｉｓｐａｒａｂｏｌａ带，２）Ａｎｉｓｏｇｒａｐｔｕｓｍａｔａｎｅｎｓｉｓ带，３）Ｐｓｉｇｒａｐｔｕｓ带和４）Ａｄｅｌ－ｏｇｒａｐｔｕｓ－Ｃｌｏｎｏｇｒａｐｔｕｓ带；并与国内外主要地区的笔石带作了较为详细的对比。笔者认为Ｒ．ｆ．ｐａｒａｂｏｌａ带为我国奥陶纪最早的一个笔石带，但与纽芬兰ＧｒｅｅｎＰｏｉｎｔ剖面和挪威Ｎｒｓｎｅｓ剖面相比，大阳岔及其邻近地区在Ｒ．ｆ．ｐａｒａｂｏｌａ带之下缺少了以较小个体Ｒ．ｐｒａｅｐａｒａｂｏｌａ和Ｓｔａｕｒｏｇｒａｐｔｕｓｄｉｃｈｏｔｏｍｕｓ发育为特征的Ｒ．ｐｒａｅｐａｒａｂｏｌａ带。

On the basis of the studies of graptolites across the Cambrian Odovician boundary sections from Dayangcha and its surrounding area,Jilin Province,China,the four earliest Ordovician graptolite zones can be ascendingly recognized in this area as follows: Rhabdinopora flabelliformis parabola Zone, Anisograptus matanensis Zone, Psigraptus Zone and Adelograptus Clonograptus Zone.A precise worldwide correlation of the four earliest Ordovician graptolite zones has been done in this paper.The author considers that the Rhabdinopora praeparabola Zone,which was recognized in Green Point (Newfoundland) and Nrsnes (Oslo) and is under the domination of R.praeparabola and Staurograptus dichotomus, is absent below the R.f.parabola Zone in the Dayangcha section.