西藏措勤地区敌布错组时代重新厘定  

The Age Re⁃Determination of the Dibucuo Formation in Cuoqin Area,Xizang

作　　者：刘函[1,3] 李俊 高睿[2] 苟正彬[1] 张士贞[1] Liu Han;Li Jun;Gao Rui;Gou Zhengbin;Zhang Shizhen(Chengdu Center,China Geological Survey,Chengdu 610081,China;College of Earth Sciences,Chengdu University of Technology,Chengdu 610059,China;School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China)

机构地区：[1]中国地质调查局成都地质调查中心,四川成都610081 [2]成都理工大学地球科学学院,四川成都610059 [3]中国地质大学地球科学与资源学院,北京100083

出　　处：《地球科学》2024年第9期3071-3088,共18页Earth Science

基　　金：中国地质调查局项目(Nos.DD20240032,D20221635,DD20221811);科技部青藏科考项目(No.2019QZKK0706).

摘　　要：措勤地区上二叠统敌布错组与区域上古生物及地层研究进展存在矛盾,需要加强对其时代的厘定以准确理解其地质意义.基于锆石U-Pb定年,并结合野外调查与区域地层对比,将敌布错组重新归并为3类时代不同的岩石地层单元.敌布错组A以含砾砂板岩及晚古生代植物化石为特征,碎屑锆石年龄谱与拉嘎组类似,为拉嘎组或者昂杰组.敌布错组B为海陆交互相碎屑岩,获得系列早白垩世早期年龄值,结合被早白垩世岩体侵位的特征将其厘定为则弄群下部.敌布错组C完全由早白垩世晚期火山岩与火山碎屑岩组成,与则弄群上部一致.结合区域资料,认为措勤地区中二叠世‒晚三叠世为连续的碳酸盐岩沉积,没有受到晚古生代岛弧造山作用的影响,早白垩世班公湖‒怒江残余海盆的南界在措勤地区较之前的认识向南推进了约50 km.The Upper Permian Dibucuo Formation in Cuoqin area is subject to age redetermination to accurately understand its geological significance since it is contradicted by the research progress of regional paleontology and stratigraphy.Based on field survey,regional stratigraphic correlation and detrital zircons U-Pb dating,the Dibucuo Formation is reclassified into three lithostratigraphic units of different ages.The Dibucuo Formation A is characterized by conglomerate-bearing sand-slate and Late Paleozoic plant fossils,and similar clastic zircons age spectrum with the Laga Formation,which should be classified into Laga Formation or Angjie Formation.Dibucuo Formation B is mainly composed of marine-continental clastic rocks,which is determined as the lower part of the Lower Cretaceous Zenong Group according to the Early Cretaceous clastic zircons and its emplacement by Early Cretaceous intrusive rocks.Dibucuo Formation C is almost completely composed of the late Early Cretaceous volcanic and pyroclastic rocks,consistent with the upper part of the Lower Cretaceous Zenong Group.Combined with the regional data,it is believed that the Cuoqin area was a continuous carbonate deposit from the Middle Permian to the Late Triassic,which was not affected by the Late Paleozoic Gangdese island arc orogenesis.The Early Cretaceous southern boundary of Bangongco-Nujiang residual sea basin in Cuoqin area is pushed about 50 km southward compared with the previous understanding.

关 键 词：冈底斯 敌布错组 晚二叠世 早白垩世 措勤 地层学 岩石学. 

分 类 号：P535[天文地球—古生物学与地层学]