乌当地区奥陶系湄潭组的地层学研究

贵阳市乌当地区处于黔北早古生代沉积区及黔南晚古生代地层沉积区交界处,具有独特的地质及地层发育特征,其中奥陶系湄潭组地层发育,但研究程度不高。结合前人的研究成果,作者等测制了6条湄潭组地层剖面,对该组的岩石地层、生物地层及年代地层进行研究,并与黔北地区的湄潭组、大湾组进行了比较。研究结果显示,乌当地区的湄潭组特别是上段明显有别于黔北地区标准的湄潭组上段及大湾组,建议用"湄潭组上段"来表示该段地层。乌当湄潭组的笔石地层研究较好,可建5个笔石带及一个层位;本文把中奥陶统底界暂放在湄潭组上段底部硅质岩之下,说明湄潭组是一个跨时的岩石地层单元。乌当地区是贵州大学等高校的地质实习基地,湄潭组的地层学研究不仅具有学术意义,也有助于实习基地的建设。

Stratigraphy Study of the Ordovician Meitan Formation in Wudang,Guiyang

The Ordovician stratigraphy of Wudang,Guiyang laying the interface of the north and the south Guizhou deposit area is well exposed,but its study degree is in a low.On basis of the previous research,we conducted a study which related to the stratigraphy,biostratum,chronostratigraphic unit after measuring 6 sections of the Meitan Formation in Wudang area,and compared with the Meitan Formation,the Dawan Formation in the north of Guizhou province.The results suggest that the Meitan Formation especially the Upper Members in Wudang area is obviously different from its coeval stratigraphy in North Guizhou.We suggest that the ＂Upper Member of the Meitan Formation＂ should be the right member name in Wudang area.Besides,five graptolite zones and a graptolite layer have been known to the Meitan Formation in Wudang area.In the paper the Ordovician bottom are momentarily posted on the bottom of the siliceous rocks of the ＂Upper Member of the Meitan Formation＂ and find that the Meitan Formation here is a diachronism stratigraphic unit.Wudang area as the geological exercitation base of Guizhou University,its stratigraphic study has not only academic significance,but also helps to the base construction.of field study.