塔里木盆地塔中台地上奥陶统良里塔格组核形石成因研究  

Origin of oncolites from the Upper Ordovician Lianglitage Formation,Tazhong Platform,Tarim Basin,NW China

作　　者：姜红霞 刘超飞 孙晓芳 吴亚生[3] 裴礽奕 Jiang Hongxia;Liu Chaofei;Sun Xiaofang;Wu Yasheng;Pei Naiyi(Hebei Key Laboratory of Strategic Critical Mineral Resources,Hebei GEO University,Shijiazhuang 050031;Zhengzhou University,Zhengzhou 450001;Key Laboratory of Cenozoic Geology and Environments,CAS,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029)

机构地区：[1]河北省战略性关键矿产资源重点实验室,河北地质大学古生物研究院,石家庄050031 [2]郑州大学,郑州450001 [3]中国科学院地质与地球物理研究所,北京100029

出　　处：《地质科学》2023年第2期677-696,共20页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家自然科学基金青年基金项目(编号:4190020681)资助。

摘　　要：塔里木盆地塔中台地上奥陶统良里塔格组礁滩相中核形石大量发育。本文选取5口钻井取心样品,从核形石形态、粒径大小、纹层磨损度、圆度几个方面进行镜下统计分析。镜下观察核形石有长条状、扁平状、偏心椭圆形、椭圆形、卵圆形、圆形等形状,平均粒径在0.1~2.5 cm之间,核心颗粒以生屑颗粒为主。核形石的纹层磨损度在泥粒岩中为轻度,在颗粒岩中为重度,泥粒—颗粒岩居中。研究认为,促使塔中台地上奥陶统核形石形成的因素包括水动力能量、微生物、碎屑颗粒的累积量等,其中水动力能量占主导地位。能量过低,核形石扁平;能量适合,核形石纹层均匀且厚;能量过强,核形石处于磨蚀状态。水流的强烈冲刷作用会破坏微生物对颗粒的黏附作用,使砂屑生屑核形石滩转变为砂屑生屑滩。Oncolites are rich in the Upper Ordovician Lianglitage Formation in the Tazhong Platform,Tarim Basin.Statistical analysis of the oncolites in thin sections of core samples from 5 drilling wells was performed,in terms of the shape,size,degree of lamina abrasion,roundness degree of the oncoids.The main shapes of the oncoids include elongate,irregular oval,oval,and rounded.The oncoid size ranges from 0.1~2.5 cm.The cores of the oncoids are mainly bioclastic debris.The degree of lamina abrasion is slight in the packstone,severe in the grainstone,moderate in the pack-grainstones.This result suggests that the factors promoting the formation of Upper Ordovician oncolites in the Tazhong Platform include hydrodynamic energy,types of microorganism,and availability of bioclastic particles.The main factor is hydrodynamic energy.The oncoids are elongate and irregular in low hydrodynamic environment,have thick uniform laminae in moderate hydrodynamic environment,and are abrased in high hydrodynamic environment.However,the highest hydrodynamic energy with strong washing can destroy the adhesion of microorganisms to particles and translate the oncolite beach into sand beach.

关 键 词：塔里木盆地 塔中台地 上奥陶统 核形石 磨损度 

分 类 号：P534.42[天文地球—古生物学与地层学] P588.248[天文地球—地质学]