湖北宜昌志留系龙马溪组几丁虫及其年代和生物复苏意义  

Chitinozoans of the Silurian Longmaxi Formation in Yichang,Hubei Province and its Significance for Choronostratigraphy and Biorecovery

作　　者：陈孝红[1] 危凯[1] 张淼[1] 张保民[1] 周鹏[1] 

机构地区：[1]中国地质调查局武汉地质调查中心,武汉430205

出　　处：《地质学报》2017年第12期2595-2607,共13页Acta Geologica Sinica

基　　金：国土资源部公益性行业科研专项(项目号201311062);国家自然科学基金项目(编号41472031);中国地质调查局调查项目(编号1212011121103)资助的成果

摘　　要：调查分析了位于湖北省宜昌市分乡的一口志留系钻孔,在龙马溪组下段至上段下部的进尺约100 m的岩芯中采取了313件样品进行几丁虫分离,其中165件炭质泥岩和泥岩样品中共发现保存完整的早志留世几丁虫化石917枚。自下而上识别出Belonechitina?postrobusta,Conochitina alargada,Armoricochitina sp.和Conochitina emmastensis生物带。几丁虫生物带的组合特征和时代意义,及其与全球其它地区同期几丁虫对比,暗示几丁虫Conochitina alargada的始限位置与笔石Monograptus triangularis的始限位置接近,可以作为埃隆期底界界线划分的生物化石参考标志之一。志留纪龙马溪组几丁虫多样性最早发生在鲁丹期末期,在埃隆期晚期出现丰度和分异度的明显升高。微量元素组成的环境意义研究显示龙马溪组下段下部黑色页岩与下段上部深灰色页岩和上段下部黄绿色页岩形成于氧化环境,龙马溪组下段下部黑色页岩中几丁虫属种稀少不是环境所致,而是奥陶纪生物大绝灭之后志留纪几丁虫生物复苏之前几丁虫生物残存复苏阶段的产物,暗示奥陶纪大绝灭之后志留纪几丁虫生物复苏开始于鲁丹期晚期,并在埃隆期中-晚期发生辐射。The study carried out an investigation for a drilling core of the Silurian System in Fengxiang town, Yichang, Hubei Province. 313 samples were collected from about 100 m long core consisting of the Lower Member and the lower Upper Member of Silurian Longmaxi Formation. Among them, 165 samples of black shales and dark mudstones produce well preserved Early Silurian chitinozoans. Four chitinozoan biozones were recognized, which include Belonechitina？ postrobusta, Conochitina alargada, Armoricochitina sp. nov. and Conochitina emmastensis biozones in an ascending order. Each chitinozoan biozone was diverse and includes new species occurring with well known species, and can be correlated with chitinozoan biozones found from the contemporary strata of the Latvia, Estonia and other areas. The relationships between the chitinozoan biozones and the graptolite in the Silurian of the Yichang area indicate that the FAD of the chitinozoan Conochitina alargada is the same as that of the graptolite Monograptus triangularis, and can be regarded as one of the biomarks which defined the basal boundary of the Aeronian stage.

关 键 词：几丁虫 生物地层学 龙马溪组 志留系 湖北 

分 类 号：Q915[天文地球—古生物学与地层学]