大兴安岭南段陆相二叠系-三叠系界线地层序列及其意义：来自锆石U-Pb年代学和生物地层学的证据  

Advance in Study of Terrestrial Permian-Triassic Boundary Stratigraphic Sequence in Southern Great Xing’an Range and Its Significance:Constraints from Zircon U-Pb Chronology and Biostratigraphy

作　　者：张渝金[1] 张超[1] 谭红艳[1] 李伟[1] 杨晓平[1] 杨涛[2] 马永非[1] 刘淼[1] 司秋亮[1] 汪岩[1] Zhang Yujin;Zhang Chao;Tan Hongyan;Li Wei;Yang Xiaoping;Yang Tao;Ma Yongfei;Liu Miao;Si Qiuliang;Wang Yan(Shenyang Center of Geological Survey,China Geological Survey,Shenyang 110034,China;College of Paleontology,Shenyang Normal University,Shenyang 110034,China)

机构地区：[1]中国地质调查局沈阳地质调查中心,辽宁沈阳110034 [2]沈阳师范大学古生物学院,辽宁沈阳110034

出　　处：《地球科学》2019年第10期3314-3332,共19页Earth Science

基　　金：国家青年自然科学基金(No.41702032);中国地质调查局项目(Nos.DD20190039-06,DD20160048-04);国家重点研发计划项目（No.2017YFC0601305-01)

摘　　要：陆相二叠纪-三叠纪地层划分与对比研究对认识该时期全球性重大生物和环境事件具有重要意义.以大兴安岭南段阿鲁科尔沁旗坤都地区新发现的下三叠统老龙头组为研究对象,重点对二叠系-三叠系接触关系开展详细调查研究,系统采集了界线上下的古生物化石,对老龙头组火山岩进行了锆石U-Pb同位素测试分析,并确定了老龙头组与下伏林西组呈平行不整合接触关系,两者之间存在短暂沉积间断.生物地层显示林西组时代为晚二叠世晚期,老龙头组古生物匮乏,可能与二叠系-三叠系之交的生物灭绝事件有关.而老龙头组中3个同位素年龄值分别为251.5±2.2 Ma、249.7±2.5 Ma和249.5±1.8 Ma,时代指示为早三叠世,然而二叠系-三叠系界线的准确位置还需进一步研究.大兴安岭南段普遍存在可能与古亚洲洋闭合有关的早三叠世岩浆事件,古亚洲洋沿着西拉木伦河缝合带发生碰撞闭合,其闭合时限至少持续至早三叠世,老龙头组是两大板块拼贴碰撞作用的产物.The identification and comparation of terrestrial Permian-Triassic have great significance to the understanding of coeval major global biological and environmental events.In this paper,it focuses on the newly discovered Lower Triassic Laolongtou Formation in Kundu area of Arkhorqin Banner,southern Great Xing’an Range.The contact relationship of Permian-Triassic stratigraphy was studied in particular,plant fossils and palynological fossils above and below the boundary were collected,and the zircon isotopic U-Pb analysis from the volcanic interlayer in the Laolongtou Formation were also analyzed.It is confirmed that there is a parallel unconformity contact relationship between the Laolongtou Formation and the underlying Linxi Formation,and there is a short sedimentary gap between them.The biostratigraphic records show that the Linxi Formation was formed in the Late Permian,however,the Laolongtou Formation was lack of fossil evidence,which may be related to the extinction event at the intersection of the Permian and Triassic.Three isotopes ages from Laolongtou Formation were 251.5±2.2 Ma,249.7±2.5 Ma and 249.5±1.8 Ma,indicating that they formed at Early Triassic.However,the exact location of the Permian-Triassic boundary needs further study.The Early Triassic magmatic events which widely outcropped at southern Great Xing’an Range area probably related with the closure of Paleo-Asian Ocean.The Paleo-Asian Ocean finally closed along the Xilamulun River suture zone at least until the Early Triassic,and the sedimentary of Laolongtou Formation is the product of collision at its both sides.

关 键 词：晚二叠世 早三叠世 林西组 老龙头组 锆石U-PB年代学 生物地层学 大兴安岭南段 

分 类 号：P534[天文地球—古生物学与地层学]