陕西韩城寒武纪三叶虫生物地层

陕西韩城寒武系出露良好 ,化石丰富 ,假整合覆盖于厚约 2 0 m的霍山组石英砂岩之上 ,从下寒武统上部至奥陶系为沉积连续。本区寒武系主要以紫色和黄色泥页岩、泥灰岩、灰岩和白云质灰岩为主 ,从下到上可划分为馒头组、毛庄组、徐庄组、张夏组和三山子组。根据在本区寒武系发现的三叶虫化石 ,韩城地区寒武系可划分为 14个生物带 ,自上而下为 :Blackwelderia带 ,Damesella带 ,L iopeishania带 ,Dorpyge richthofeni带 ,Crepicephalina带 ,Manchuriella带 ,Poriagraulos带 ,Inouyops带 ,Sunaspis带 ,H suchuagia带 ,Shantungaspis带 ,Probowmaniella带 ,Weijiaspis带和 Redlichia murakamii带。

CAMBRIAN TRILOBITE BIOSTRATIGRAPHY OF HANCHENG REGION, SHAANXI

The Cambrian strata are well developed in the Hancheng region, Northeast Shaanxi and consist chiefly of purple and yellow shale, marl, limestone and dolomitic limestone. They disconformably overlie the quartz sandstone (Huoshan Formation, about 20m thick) and conformably underlie the Ordovician limestone. Based on the study of trilobite faunal succession and the depositional characters from two Cambrian sections in Hancheng, the formation and trilobite zones in Hancheng region are as follow:The lower part of the Cambrian here consists mainly of purple and yellow shale, the Manto Formation, which is overlain conformably by the Maozhuang Formation and disconformably overlies the quartz sandstone. The trilobite zones in the Maozhuang Formation are in descending order Weijiaspis and Redlichia murakamii Zones. The Maozhuang Formation, which is overliain conformably by the Xuzhuang Formation, is composed of thin bedded marl intercalated with purple and yellow sandy shale. The trilobite zones in the Maozhuang Formation are in descending order, Shantungaspis and Probowmaniella Zones and the trilobite zones in the Xuzhuang Formation are Poriagraulos , Inouyops , Sunaspis and Hsuchangia Zones(in descending order too). The Zhangxia Formation, which is overlain conformable by the Sanshanzi Formation and overlies the Xuzhuang Formation, is composed of thick bedded limestone and oolitic limestone. The trilobite zones in this formation are Damesella , Liopeishania , Dorypyge richthofeni , Crepicephalina and Manchuriella Zones. The Sanshanzi Formation, which is overlain conformably by Ordovician limestone and overlies the Zhangxia formation, is composed of thick bedded dolomitic limestone intercalated with thin bedded marl and lime dolomite, we have collected the fossils—? 獴lackwelderia sp., Damesops convexus and Cyclolorenzella parabola in the lower part of this Formation. The trilobite zone of this Formation is Blackwelderi Zone.