摘要
扬子地台纱帽组的地质年代归属一直存在争议。鄂西地区纱帽组主体由砂泥岩组成,但在顶部出现一套夹生物屑灰岩透镜体的碎屑岩。在恩施地区纱帽组灰岩段之下发现了一套斑脱岩,通过对斑脱岩的锆石U-Pb测年,得到加权平均年龄为(424.5±6.4)Ma,由此认为纱帽组顶部的沉积时限为文洛克世。考虑到纱帽组下部为早志留世,综合分析认为纱帽组是一跨时代的地层单元。该层斑脱岩产于含生物屑灰岩团块或条带的岩性段的下部,因此认为以灰岩的出现作为文洛克统沉积的开始;同时,认为该层斑脱岩为加里东运动在华南活动的产物。
There are big disputes of the chronostratigraphic division of the Shamao Formation on the research of Yangtze block in recent years.The main body of Shamao Formation in western Hubei is composed of sand and mudstone,but at the top is formed by the clastic rock with bioclastic limestone.The age of bentonite found in the Upper Shamao Formation can represents the age of sedimentation.By means of the U-Pb zircon dating on this bentonite,we obtained the weight mean age 424.5±6.4Ma,indicating that the sedimentation occurred in the Wenlock.In addition,our dating on the bentonite suggests the Shamao Formation is cross-time stratigraphic unit and belongs to Early-Middle Silurian.The occurrence of this bentonite in the lower section of the biostromal limestone mass or band indicates the limestone is the start of the Middle Silurian.
作者
李朋
胡正祥
吴龙
杜小锋
宗维
周峰
毛启曦
Li Peng Hu Zhengxiang Wu Long Du Xiaofeng Zong Wei Zhou Feng Mao Qixi(Hubei Institute of Geological Survey, Wuhan 430034, Chin)
出处
《地质科技情报》
CSCD
北大核心
2017年第4期1-9,共9页
Geological Science and Technology Information
基金
中国地质调查局地质大调查项目(12120114066101)
中国地质调查局"扬子工程湘西-鄂西成矿带神农架-花垣地区地质矿产调查"二级项目(DD20160029)
关键词
纱帽组
斑脱岩
年代学
Shamao Formation
bentonite
geochronology
