拉萨地块措勤地区早三叠世牙形石生物地层学新进展  

NEW PROGRESS ON THE EARLY TRIASSIC CONODONT BIOSTRATIGRAPHY IN THE COQEN AREA,LHASA TERRANE

作　　者：李涌溪 纪占胜[1] 武桂春[3] LI Yongxi;JI Zhansheng;WU Guichun(Chinese Academy of Geological Sciences,Beijing 100037,China;Chinese University of Geosciences,Beijing 100083,China;Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China)

机构地区：[1]中国地质科学院,北京100037 [2]中国地质大学(北京),北京100083 [3]中国地质科学院地质研究所,北京100037

出　　处：《微体古生物学报》2021年第4期334-351,共18页Acta Micropalaeontologica Sinica

基　　金：国家自然科学基金(41972034);中国地质科学院基本科研业务费项目(JKY202017)资助。

摘　　要：牙形石生物地层学研究表明,拉萨地块发育海相下三叠统沉积,根据岩性可分为白云岩和灰岩。白云岩中的牙形石齿体粗壮,属种单一,属于Pachycladina-Hadrodontina序列;而灰岩中的牙形石属种分异度大,以齿片型牙形石为主,属于Neospathodus-Novispathodus序列。Neospathodus-Novispathodus序列因分布广、划分精细,在地层划分对比中得到了更为广泛的关注。然而,在前期对拉萨地块的研究中,该序列在划分精度上明显不足,Dienerian亚阶至Smithian亚阶牙形石带尚未建立,不利于与其他地区的下三叠统进行精确对比。为了完善拉萨地块早三叠世的Neospathodus-Novispathodus牙形石序列,本文对措勤地区敌布错剖面的下三叠统进行重新采样研究,取得了新的认识:首次确定牙形石种Eurygnathodus costatus在敌布错剖面的存在;识别并建立了Dienerian亚阶至Smithian亚阶的2个牙形石生物带,自下而上为Neospathodus dieneri带和Novispathodus waageni-Eurygnathodus costatus组合带。本研究表明拉萨地块灰岩相的早三叠世序列比较完整,可与华南等地区的牙形石带进行很好的对比。Research on conodont biostratigraphy shows that the lower Triassic deposits have been well developed in the Lhasa Terrane.In lithology,they are differentiated into dolomite and limestone.Different types of conodonts were also recognized.In the dolomite,the conodonts,characterized by the robust specimens with a low diversity,belong to the Pachyladina-Hadrodontina succession.In the limestone,the conodonts are dominated by the abundant and diverse blade-like specimens that belong to Neospathodus-Novispathodus succession.Since the latter succession has been well established worldwide,it is more important in stratigraphic correlation than the other one.However,the conodont zones from the Dienerian to the Smithian in the Lhasa Terrane remained unclear.This situation is unfavorable for the accurate correlation between the Lhasa Terrane and the other regions.To better understand the Neospathodus-Novispathodus succession in the Lhasa Terrane,we re-studied the Dibuco Section in the Coqen Area.The following progresses are made:the species Eurygnathodus costatus is firstly found to be present in the Lhasa Terrane;2conodont zones ranging from the Dienerian to the Smithian are differentiated,ascendingly,they are Neospathodus dieneri Zone and Novispathodus waageni-Eurygnathodus costatus Zone.This study indicates that the Early Triassic conodont succession from the limestone facies in the Lhasa Terrane is much complete,and it could be well correlated to that in the South China Terrane.

关 键 词：Eurygnathodus costatus Neospathodus-Novispathodus 牙形石带 早三叠世 拉萨地块 措勤地区 

分 类 号：Q913.85[天文地球—古生物学与地层学]