黔北仁怀核桃湾志留系石牛栏组滨岸灰岩的古生态学  

PALAEOECOLOGY OF THE SILURIAN SHIHNIULAN FORMATION AT THE COASTAL HETAOWAN SECTION,RENHUAI OF NORTHERN GUIZHOU

作　　者：郭伟[1] 李启剑 赵萌 梁萍萍[1] 王南[1] 李越[2] GUO Wei;LI Qijian;ZHAO Meng;LIANG Pingping;WANG Nan;LI Yue(PetroChina Research Institute of Exploration&Development,Beijing 100083,P.R.China;Center for Excellence in Life and Paleoenvironment,State Key Laboratory of Palaeobiology and Stratigraphy,Nanjing Institute of Geology and Palaeontology,Chinese Academy of Sciences,Nanjing 210008,P.R.China;Southwest Oil&Gasfield Company of PetroChina,Chengdu 610000,P.R.China)

机构地区：[1]中国石油勘探开发研究院,北京100083 [2]现代古生物学和地层学国家重点实验室,中国科学院生物演化与环境卓越创新中心,中国科学院南京地质古生物研究所,南京210008 [3]中国石油西南油气田分公司,成都610000

出　　处：《微体古生物学报》2022年第4期307-315,共9页Acta Micropalaeontologica Sinica

基　　金：西南油气田分公司项目(编号:XNS25JS2020);中国科学院青促会项目(编号:2019310);中国科学院战略性先导科技专项B类(编号:XDB26000000)资助。

摘　　要：本文展示的华南板块上扬子区黔中古陆滨岸带志留系灰岩地层具有独特的古生态学指标。黔北仁怀核桃湾剖面兰多维列统艾隆阶石牛栏组沉积时的古地理位置靠近海岸线,厚度约30 m,未经历远岸区石牛栏组下部松坎段含泥质粉砂瘤状灰岩的过渡,浅海生屑灰岩就直接整合覆盖于龙马溪组黑色笔石页岩之上,此滨岸带生物-岩相的急剧转折表明从龙马溪组缺氧变为石牛栏组富氧海底是快速发生的。核桃湾滨岸附近无河流携带陆源碎屑注入而影响海水盐度和清澈度,潮汐影响弱。腕足类、珊瑚-海百合粗颗粒碎片可形成薄层生屑滩灰岩,灰岩微相显示细颗粒生屑化石的生物多样性组成均为常见的底栖壳相动物类型,但不栖居钙质微生物或后生动物造礁生态群落。桐梓上升事件导致石牛栏组顶部沉积相单元缺失,海退过程中可能出现的蒸发白云岩坪以及潮间带交错层理记录因滨岸带露出海底时间长而被完全剥蚀。Palaeoecological parameters of the Silurian limestones are special at the coastal belt of the Qianzhong Oldland,upper Yangtze region of the South China Block.The late Aeronian(Llandovery) Shihniulan formation with thickness of 30 m at the Hetaowan section of Renhuai,northern Guizhou province was situated along the coastline.Muddy and silty nodual limestones of the Songkan member,lower Shihniulan formation are absent;shallow marine bioclastic limestones of the Shihniulan formation conformably overlay on the graptolitic black shales of the Lungmachi formation.Such a lithological succession suggests that the ecological units from the dyoxic Lungmachi formation to the oxygenated Shihniulan formation was dramatically happened.The limestones of the Shuhniulan formation were deposited in a normal salinity and high clarity shallow marine-floor without fluvial terrigenous input nearby;and the tidal sedimentary structure is not notable.Coaser-grained brachiopods and coral-crinoid are both occurred from the thinbedded bank units.Fine-grained bioclasts viewed from microfacies are commonly of benthic shelly taxa,without reefbuilding community.Regessional records of the evapritic dolostones and the cross-bedding of tidal flat likely occurred from the top of the formation were completely eroded during the Tongzi uplift event.

关 键 词：滨岸带沉积 石牛栏组灰岩 志留系 黔北仁怀 

分 类 号：P534.43[天文地球—古生物学与地层学] Q911[天文地球—地质学]