摘要
本文以河北蔚县地区为代表,对冀西北寒武—奥陶系的分界及牙形石动物群序列作一论述。根据区内寒武一奥陶系剖面牙形石动物群形态特征、垂直分布规律、演化系列及时限范围并参考其岩性岩相变化,自上寒武统凤山组至下奥陶统治里组划分为五个牙形石带:1.Prooneotodus-Proconodontus 带;2.Cordylodus proavus 带;3.Cordy-lodus intermedius-Drepanodus simplex 带;4.Oneotodus variabilis-Utahconus beimodaoensis 带;5.Scolopodus quidraplicatus 带.通过牙形石演化阶段分析,并与国内外同层位对比,将区内寒武—奥陶系的界线置于Cordylodus proavus 带与 Cordylodus intermedius-Drepanodus simplex 带之间。
Taking Yuxian area of Hebei as an example this paper has discussed the Cambrian-Ordovician boundary and the sequence of conodont faunas of northweatern Hebei.According to the morpho- logical features,vertical distribution evolutionary series and time limits of the Cambrian-Ordovician conodont fauna from the area,the following 5 conodont zones from Upper Cambrian Fengshan Formation to the Lower Ordovician Yeli Formation have been recognized: 1)Prooneotodus-Proconodontus Zone; 2)Cordylodus proavus Zone; 3)Cordylodus intermedius-Drepandus simplex Zone; 4)Oneotodus variabilis-Utahconus beimadaensis Zone; 5)Scolopodus quadraplicatus Zone; By the analysis of conodont evolutionary stage and the inter- national correlation the Cambrian-Ordovician boundary of this area has been established between the Cordylodus proavus Zone and the Cordylodus intermedius-Drepanodus simplex Zone.
