华北地台西缘的上奥陶统

<正> 二十年前,关于华北地台的上奥陶统是否存在,几乎一无所知。一般都认为华北地台无晚奥陶世的沉积。但是,近二十年来,在华北地台西缘的许多地区不断地发现了上奥陶统。这些发现对阐明华北地台古地理、海水进退和构造运动等方面都有重要意义。 1960前,王钰、穆恩之、卢衍豪曾提出华北地台可能有上奥陶统的看法。1960年,俞昌民根据陕西耀县(原文为富平县)、宁夏固原县产有与祁连山扣门子组相同种的珊瑚Catenipora uniforma(C.M.Yu),初步肯定含该化石的地层年代为晚奥陶世。

THE UPPER ORDOVICIAN OF THE WESTERN BORDER OF NORTH CHINA PLATFORM

The Upper Ordovician of the western border of North China Platform may be subdivided into two formations. Taoqupo Formation (upper part of the Caradoc Stage) and Beiguoshan Formation (lower part of the Ashgill Stage).In the upper part of Upper Ordovician, one of the most characteristic features of the Coral faunas is the considerable development and distribution of Agetolitids (Agetolites, Agetolitella, Subagetolites) and Proporids (Plasmo-porella), mixed with the Baltic Sarcinula and the North American-Siberian Calapoecia, Rhabdotetradium and the abundant genus Favistella.During Upper Ordovician the transgression in North China platform was from the Southwest to the Northeast.