北秦岭地区三叠纪南召盆地演化及成因机制探讨  

Discussion on evolution and formation mechanisms of Triassic Nanzhao Basin in North Qinling tectonic belt

作　　者：许艳华 何登发[1,2] 成祥 苟钧壹 Xu Yanhua;He Dengfa;Cheng Xiang;Gou Junyi(School of Energy Resources,China University of Geosciences(Beijing),Beijing 100083;Key Laboratory of Marine Reservoir Evolution and Hydrocarbon Enrichment Mechanism,Ministry of Education,Beijing 100083)

机构地区：[1]中国地质大学(北京)能源学院,北京100083 [2]中国地质大学(北京),海相储层演化与油气富集机理教育部重点实验室,北京100083

出　　处：《地质科学》2023年第1期214-225,共12页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：中国石油长庆油田公司科技攻关项目(编号:ZDZX2021-01);中央高校基础研究经费项目(编号:2-9-2021-071)资助。

摘　　要：秦岭造山带作为中国中央造山带的重要组成部分,还原其复杂、漫长的演化历史始终是地质科学的研究焦点,也是亟待解决的关键科学问题。前人从构造地质学、变质岩石学等方面展开了丰富的讨论,但始终缺乏造山带内同沉积记录的精细研究。南召盆地作为北秦岭造山带唯一保存的三叠纪的地层,为研究秦岭造山带印支期的构造环境提供了最直接可靠的证据。因此本文基于精细的地质图分析,野外地质观察,利用盆地构造沉降和构造年代格架的分析方法,系统研究三叠纪南召盆地的沉积充填和沉降特征,总结出南召盆地的伸展裂陷沉积序列:底部砾岩向上迅速水体加深,形成以灰黑色页岩为主的深湖相,随后向上变为以黄褐色砂岩夹灰黑色泥岩为特征的湖泊三角洲—辫状河相;明确了快速—缓慢沉降的伸展型盆地沉降特征;厘定了南召地区的8个主要不整合面,其中,中-上三叠统太山庙组的底部为一个763~121.9 Ma的穿时不整合面;确定了南召盆地4期主要演化阶段。研究表明:南召盆地是一个伸展裂陷盆地,形成于加里东运动、印支运动共同作用产生的造山带复合基底之上,发育于印支期北秦岭造山带两次重要隆升事件之间,代表晚三叠世卡尼阶的北秦岭造山带构造活动的暂停。As an important part of the central orogenic belt in China, restoring the complex and long evolutionary history of the Qinling orogenic belt has always been the focus of geological research and a key scientific problem to be solved urgently. The predecessors have carried out abundant discussions from the aspects of structural geology and metamorphic petrology, but there is still a lack of detailed study on the synsedimentary record in orogenic belts. Nanzhao Basin, as the only preserved Triassic strata in the North Qinling orogenic belt, provides the most direct and reliable evidence for the study of the Indosinian tectonic environment of the Qinling orogenic belt. Therefore,based on detailed geological map analysis, field geological observation, and basin tectonic subsidence and chronostratigraphic framework analysis methods, this paper systematically studied the sedimentary filling and subsidence characteristics of the Triassic Nanzhao Basin. The sedimentary sequence of extensional rifting in Nanzhao Basin is summarized as follows: the bottom conglomerate alluvial fan changed upward to deep lacustrine facies dominated by gray black shale,and then changes upward to lacustrine delta-braided river facies characterized by yellowish brown sandstone mixed with gray black mudstone. The subsidence characteristics of extensional basins with rapid-slow subsidence are clarified. Eight main unconformities in Nanzhao area are identified,among which the bottom of the Upper Triassic Taishanmiao Formation is a time-transgressive unconformities of 763~121.9 Ma. Four main evolutionary stages of Nanzhao Basin were determined.The results show that Nanzhao Basin is an extensional rift basin, which was formed on the composite basement of orogenic belt produced by Caledonian movement and Indosinian movement, and developed between two important uplift times of North Qinling orogenic belt in Indosinian period,representing the suspension of tectonic activity of North Qinling orogenic belt in Late Triassic Carnian stage.

关 键 词：秦岭造山带 构造沉降 构造演化 印支运动 南召盆地 

分 类 号：P542[天文地球—构造地质学]