低能环境下核形石组构特征及成因——以中15井上奥陶统良里塔格组核形石为例  

Fabric Characteristics and Genesis of Oncoids in a Low-Energy Environment:A case study from the Upper Ordovician Lianglitage Formation in well Zhong-15

作　　者：耿锋 杨瑞召[1] 唐雨[4] 沙旭光 孙尧斌[4] 王振宇 张云峰[4] GENG Feng;YANG RuiZhao;TANG Yu;SHA XuGuang;SUN YaoBin;WANG ZhenYu;ZHANG YunFeng(College of Geoscience and Surveying Engineering,China University of Mining and Technology(Beijing),Beijing 100083,China;Exploration and Development Research Institute,Northwest Oilfield Branch,SINOPEC,Urumqi 830011,China;Key Laboratory of Deep Geology and Resources,SINOPEC,Beijing 102206,China;School of Geoscience and Technology,Southwest Petroleum University,Chengdu 610500,China)

机构地区：[1]中国矿业大学(北京)地球科学与测绘工程学院,北京100083 [2]中国石化西北油田分公司勘探开发研究院,乌鲁木齐830011 [3]中国石化深部地质与资源重点实验室,北京102206 [4]西南石油大学地球科学与技术学院,成都610500

出　　处：《沉积学报》2024年第1期84-94,共11页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目(41702122)。

摘　　要：【目的】奥陶纪时期全球发生了一次生物大辐射,核形石研究对于揭示该期古环境特征及演化具有重要意义。【方法】以塔里木盆地塔中地区中15井核形石为研究对象,通过详细地岩心观察和室内薄片、扫描电镜鉴定,统计、分析核形石宏观形态、微观组构特征,探讨了其形成环境、成因及地质意义。【结果】塔里木盆地塔中地区中15井上奥陶统良里塔格组泥质条带灰岩段为开阔台地的台内洼地沉积,中上部发育一套厚约12.3 m的深灰色含泥质条带核形石灰岩、含生屑泥晶核形石灰岩,核形石粒径大、丰度高。核心为早期台缘生屑、团块;包壳厚度大,富含细菌纹层;基质中多充填灰泥、细生屑,普遍发育泥质条带;代表了一种水体搅动及搬运作用不强烈的原地或近距离搬运沉积成因。核形石可分为球状、帽状、板条状、椭球状等四类,以帽状、球状为主。垂向上为三个核形石发育段,单个旋回含量、粒度呈变大趋势。【结论】球状、帽状核形石形成于水体搅动和静止相交替状态的环境,板条状核形石形成于弱搅动的低能环境。中15井核形石的产出受奥陶纪全球海平面上升以及生物大辐射影响,具体为丰富的核心物质来源(相邻台缘带生屑、团块)、发育程度高的细菌黏附生长、稳定或弱波动的沉积环境等因素的有机耦合。[Objective]A global biological radiation occurred during the Ordovician period,which could be poten-tially revealed by analyzing the oncolites formed during this period.[Methods]Taking the oncoids of well Zhong 15 in Tazhong area of Tarim Basin as the research object,through detailed core observation,thin section and scanning electron microscope identification,the macroscopic morphology and microscopic fabric characteristics of oncoids were counted and analyzed,and their formation environment,genesis and geological significance were discussed.[Results]Further confirming that the argillaceous banded limestone member of the Lianglitage Formation in well Zhong-15,Tazhong area,Tarim Basin represents open-platform deposition in an intra-platform depression.A set of dark gray and bioclastic argillaceous banded oncolitic limestones with a thickness of approximately 12.3 m are devel-oped in the middle and upper parts of this member,with a large particle size and high abundance of oncoids.The core consists of the early platform-margin bioclasts and intraclasts.The oncoid cortex is thick and rich in bacterial lamina.The matrix is primarily filled with plaster and fine biological fossil fragments,with commonly seen argillaceous bands.It represents a sedimentary origin of in-situ or little transportation with weak water agitation.The oncoids can be divided into four types based on shape:spherical,dome-like,strip-shaped,and ellipsoidal,in which dome-like and spherical are dominant.Vertically,there are three sequences of oncolitic development,within each of which the content and particle size of oncoids tend to increase from the bottom to the top.[Conclusions]Spherical and domelike oncoids are formed in the environment where the water body is in an alternating state of agitation and stasis,while strip-shaped oncoids are formed in the low-energy environment with weak agitation.The oncoids of well Zhong-15 result from various factors,such as global sea level rise in Ordovician,biological radiation attributed to organic coupling

关 键 词：核形石 形成环境 中15井 良里塔格组 上奥陶统 塔中西部 

分 类 号：P512.2[天文地球—地质学]