龙门山北段志留纪地层研究

STUDY ON SILURIAN STRATA IN THENORTHERN SECTION OF THE LONGMEN MOUNTAIN

作者通过对龙门山北段志留纪牙形石和笔石的研究,自下而上初步建立了该区的牙形石带:Paraspothognothodus obesus 带,Paraspothognathodus parahassi-P．guizhoweusis 组合带,Pterospathogwa-wodus oelloui 带:笔石带:Demirastriles (?) 带,Spirograptus (?) 带和 Streptograptus nodifer 带.在此基础上,将该区地层自下而上划分为:龙马溪组、磨刀垭组、后蒿坪组和宁强组,其中磨刀垭组和后蒿坪组为2个新建组。本区绝大部分地层为下志留统,只有宁强组上部可能为中志留统。

Conodonts zones and Graptolites zones of the Silurian in the northern of Longmen mountain have been set up by recently study. From lower to upper, the Conodonts zones are Paraspatho-gnathodus obesus zone, Paraspathognathodus parahassi - P. guizhovensis assemblage zone, Pterospathoguathodus celloni zone ; the Graptolites zones are Demirastrites cunvolutus zone; Spirograptus turriculatus zone and Streptograptus nodifer zone. On the basis of Conodonts zones and Graptolites zones, the stratigraphic division in this area from lower to upper is: Longmaxi Formation, Modaoya Formation, Houhaop-ing Formation and Ningqiang Formation, among them, Modaoya Formation and Houhaoping Formation are two new Formations. Unless the upper part of Ningqiang Formation maybe belongs to Middle Silurian, the others belong to lower Silurian.