川东南古蔺铁索桥剖面志留系石牛栏组上段生物-沉积相特征  

BIOTIC AND SEDIMENTARY CHARACTERISTICS OF THE SILURIAN UPPER SHIHNIULAN FORMATION AT THE TIESUOQIAO SECTION OF GULIN,SOUTHEASTERN SICHUAN

作　　者：孙豪飞 戴鑫 周刚[1] 陈骁[1] 明盈 徐唱 苑保国 徐亮[1] 张云峰[2] 屈海洲[2] 张园园[3] 李越[3] SUN Haofei;DAI Xin;ZHOU Gang;CHEN Xiao;MING Ying;XU Chang;YUAN Baoguo;XU Liang;ZHANG Yunfeng;QU Haizhou;ZHANG Yuanyuan;LI Yue(Research Institute of Exploration&Development,PetroChina,Chengdu 610041,China;School of Geoscience and Technology,Southwest Petroleum University,Chengdu 610500,China;State Key Laboratory of Palaeobiology and Stratigraphy,Center for Excellence in Life and Paleoenvironment,Nanjing Institute of Geology and Palaeontology,Chinese Academy of Sciences,Nanjing 210008,China)

机构地区：[1]中国石油天然气股份有限公司西南油气田分公司勘探开发研究院,成都610041 [2]西南石油大学地球科学与技术学院,成都610500 [3]现代古生物学和地层学国家重点实验室,中国科学院生物和古环境卓越创新中心,中国科学院南京地质古生物研究所,南京210008

出　　处：《微体古生物学报》2023年第3期216-226,共11页Acta Micropalaeontologica Sinica

基　　金：国家自然科学基金(编号:41702122);中国科学院战略性先导科技专项B类(编号:XDB26000000)的资助。

摘　　要：川东南古蔺铁索桥剖面志留系兰多维列统沉积时的古地理位置处于滇黔桂古陆之北的陆表海环境。埃隆阶上部石牛栏组从下段薄层泥状灰岩形成之后,相变为上段的生屑-砂屑灰岩夹含少量粉砂质泥岩,展示海水深度变浅的过程。本文基于该剖面露头和灰岩薄片鉴定,专述石牛栏组上段生物-沉积类型并分析浅海环境指标。石牛栏组上段粉砂质泥岩中大化石稀少,而灰岩层中底栖型后生动物壳相化石具有中等多样性,少量出现能鉴定属级的大化石密集层,可识别3种不同水动力强度改造的腕足类介壳滩;该段上部赋存珊瑚-层孔海绵原地格架生长建造的小型点礁,标定了该时期最接近滇黔桂古陆的后生动物造礁群落生态域分布点。石牛栏组上段不同粒度的壳相生屑颗粒与泥状灰岩砂屑构成灰岩的重要组分;海底环境指标,特别是不同水动力强度作用主导了灰岩中颗粒与灰泥含量的差异。Depositional sequences of the Llandovery(Silurian)at the Tiesuoqiao section of Gulin,southeastern Sichuan Province was situated in the epicontinental sea of northern Dian-Qian-Gui land palaeogeographically.The upper Aeronian Shihniulan Formation shows lithofacies overturn from thin-bedded micritic limestone of the lower member to bioclastic and intraclastic limestones intercalated with less silty claystones of the upper member due to an upward shallowing tract.Biotic and sedimentary types with special references on their palaeoenvironmental parameters from the upper member are concerned in present paper.Macrofossil abundance is very low in silty claystone.Benthic shelly fossils of the metazoan biota are medium biodiverse in limestones.Macrofossil concentrations with palaeontological identifications of genus are occurred from several beds.Three types of banks are recognized,which were formed by the brachiopod coquinas in different turbulent conditions.A small patch reef with in situ coralstromatoporoid frameworks occurs from the upper member indicating the southernmost ecological realm of the metazoan reef.Shelly bioclasts with diverse grain-sizes and intraclasts of lithified micritic limestones are key components in limestone units.Changeable ratios of grain and matrix of limestones were essentially attributed to hydrodynamic varieties on the marine-floor.

关 键 词：生物-岩相 石牛栏段灰岩 志留系 古蔺 上扬子区 

分 类 号：P618.13[天文地球—矿床学]