柴达木盆地北缘早二叠世凝灰岩的发现及其地质意义  

Discovery of Permian tuff from the northern margin of the Qaidam Basin and its geological implications

作　　者：刘佳 钱涛[2,3,4] LIU Jia;QIAN Tao(Coal and Chemical Industry College,Shaanxi Energy Institute,Xianyang 712000,Shaanxi,China;Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081,China;Key Laboratory of Paleomagnetism and Tectonic Reconstruction of Ministry of Natural Resources,Beijing 100081,China;Key Laboratory of Petroleum Geomechanics,China Geological Surveys,Beijing 100081,China)

机构地区：[1]陕西能源职业技术学院煤炭与化工产业学院,陕西咸阳712000 [2]中国地质科学院地质力学研究所,北京100081 [3]自然资源部古地磁与古构造重建重点实验室,北京100081 [4]中国地质调查局油气地质力学重点实验室,北京100081

出　　处：《地质力学学报》2023年第2期290-300,共11页Journal of Geomechanics

基　　金：中国地质调查局地质调查项目(DD20221810);陕西能源职业技术学院2022年度校级科学研究计划项目(2022KY15KJP);中国地质科学院基本科研业务项目(DZLXJK202004)。

摘　　要：柴达木盆地北缘地区是否存在早二叠世沉积记录依旧是一个悬而未决的问题。现有区域地质资料普遍认为二叠系并未沉积或已完全被剥蚀。这分歧起源于对现有的古生物化石形成年代认识的不同。此次研究对柴达木盆地北缘东段旺尕秀地区的石炭系克鲁克组和扎布萨尕秀组开展详细的野外地质调查和剖面实测工作,在东大沟剖面扎布萨尕秀组底部鉴别出数层凝灰岩,并采集锆石U-Pb年代学样品。通过锆石LA-ICP-MS U-Pb测年,首次获得295±2 Ma(MSWD=0.035)的高质量年代学数据。此次发表的数据,明确了柴达木盆地北缘早二叠世沉积地层的存在。该研究成果为后续柴达木二叠系含油气系统勘探提供了重要的基础地质资料支撑,并为今后开展石炭纪—二叠纪全球气候变化、海平面升降等方面的研究工作提供了重要的年代学约束。Whether the Permian sedimentary records are still preserved in the northern Qaidam Basin is an open issue with various viewpoints.Most regional geological correlations imply that those Permian successions have been wholly eroded or that there is no Permian deposition in this area.These arguments were partly derived from the contrasting interpretations of the age of the fossils obtained from the Zhabusagaxiu formation.Other scholars consider that the lower unit of the Zhabusagaxiu formation,composed of alternating sandstone,mudstone,and limestone,belongs to the Carboniferous.In contrast,its upper limestone member should be assigned an early Permian sedimentary age,hinting that Permian successions are preserved in the northern Qaidam Basin.Therefore,it is still unclear whether the Permian sedimentary records are still preserved in the northern Qaidam Basin.In this study,the Keluke and Zhabusagaxiu formations in the Wanggaxiu-Dongdagou section were investigated in the field and measured in detail,and several volcanic tuff interbeddings were identified.Zircon LA-ICP-MS U-Pb geochronological studies were undertaken on zircons retrieved from a collected tuff sample.A high-precision weighted mean age of 295±2 Ma(MSWD=0.035)was obtained for the first time.This firstly reported age estimate solidly constrains the existence of the Permian strata in the northern Qaidam Basin.This clue will provide new insight into the following oil-gas exploration concerning the Permian successions and also provide a crucial limit on the studies of Carboniferous-Permian global climate change and sea level change.

关 键 词：早二叠世 扎布萨尕秀组 锆石定年 柴达木盆地北缘 凝灰岩 

分 类 号：P534.4[天文地球—古生物学与地层学] P535[天文地球—地质学] P56