扬子北缘京山-钟祥地区下奥陶统地层序列及其区域对比  

Lower Ordovician Stratigraphic Sequence in Jingshan-Zhongxiang Area at Northern Margin of Yangtze and Regional Correlation

作　　者：刘浩[1,2] 邓新[1] 金鑫镖 曾庆銮[1,2] 徐大良[1] 张维峰[1] 彭练红[1] Liu Hao;Deng Xin;Jin Xinbiao;Zeng Qingluan;Xu Daliang;Zhang Weifeng;Peng Lianhong(Wuhan Center of China Geological Survey,Wuhan 430205,China;Key Laboratory of Paleontology and Coevolution of Life and Environment,China Geological Survey,Wuhan 430205,China)

机构地区：[1]中国地质调查局武汉地质调查中心,湖北武汉430205 [2]中国地质调查局古生物与生命-环境协同演化重点实验室,湖北武汉430205

出　　处：《地球科学》2021年第4期1359-1373,共15页Earth Science

基　　金：中国地质调查局地质调查项目(Nos.DD20160030,DD20190050)。

摘　　要：湖北京山-钟祥一带的下奥陶统特征与毗邻的峡东及随南地区存在明显差异,在此开展了岩石地层和生物地层研究对比有助于更好地了解扬子北缘早奥陶世的古地理特征及演化.通过详细的剖面测制和地层对比研究,将钟祥-京山地区下奥陶统自下而上分为娄山关组、温峡口组(新建)、钟祥组(新建)和大湾组.新建的温峡口组以竹叶状灰岩、鲕粒灰岩、生物碎屑灰岩为主,属于台地边缘浅滩-浅水陆棚相沉积.根据温峡口组中所产的腹足、腕足和头足类化石,认为其沉积时代为特马豆克期中-晚期至弗洛期早期.钟祥组为灰色-灰黑色笔石页岩夹薄层粉砂岩及少量生物碎屑灰岩透镜体,产丰富的腕足、三叶虫、海百合茎、笔石、头足类等生物化石,属于深水陆棚区沉积,其地质时代为早奥陶世弗洛期.通过区域地层对比,温峡口组与峡东南津关组、分乡组、红花园组和随南高家湾组底部层位相当,而钟祥组则与峡东大湾组下段的下部和随南高家湾组中-上部可以对比.The characteristics of the Lower Ordovician in the Jingshan-Zhongxiang area are significantly different from those in the Three Gorges and southern Suizhou. Therefore,correlation of lithostratigraphy and biostratigraphy between them is helpful to understanding the paleogeograpghy as well as the geological evolution during the Early Ordovician in the northern margin of the Yangtze platform. Based on detailed study on the lithostratigraphy and the fossil assemblage, the Wenxiakou Formation and Zhongxiang Formation of the Lower Ordovician are established. The Wenxiakou Formation consists predominantly of flat pebble limestone, oolitic limestone and bioclastic limestone, which belongs to shoal facies of platform margin to shallow shelf facies.According to the fossils such as gastropods, cephalopods and brachiopods, this formation is confirmed as a deposition from MiddleLate Tremadocian to Early Florian, which is underlain conformably by the Loushanguan Formation. This succession can be correlated to the Nanjinguan Formation,Fenxiang Formation and Honghuayuan Formation in Three Gorges area,and can also be compared with the bottom of Gaojiawan Formation in southern Suizhou area. The Zhongxiang Formation is characterized by grey or dark grey shales with some siltstones and lenticular bioclastic limestone and is assumed to have been deposited in the neritic continental shelf zone. Based on the abundant fossils such as brachiopods, trilobites, crinoid stems, graptolite and cephalopods,this formation is considered to be formed at the age of Floian and has a conformable contact with the Wenxiakou and Dawan formations. It can be compared with the lowest part to Dawan Formation in Three Gorges and the middle-upper part of the Gaojiawan Formation in southern Suizhou,respectively.

关 键 词：扬子陆块 奥陶系 弗洛阶 特马豆克阶 温峡口组 钟祥组 笔石 地层学 

分 类 号：P535[天文地球—古生物学与地层学]