上新世以来北京平原NBT1孔记录的地层沉积及构造指示  

Stratigraphic deposition and tectonic indication recorded by NBT1 borehole in Beijing Plain since Pliocene

作　　者：赵勇[1] 李瑞杰[1] 杨誉博 王纯君 杨吉龙[2,3] 王强[2,3] 李莉[1] ZHAO Yong;LI Ruijie;YANG Yubo;WANG Chunjun;YANG Jilong;WANG Qiang;LI Li(Beijing Geological Survey Institute,Beijing 100195,China;Tianjin Center,China Geological Survey Bureau,Tianjin 300170,China;Key Laboratory of Muddy Coast Geo-Environment,China Geological Survey(CGS),Tianjin 300170,China)

机构地区：[1]北京市地质调查研究院,北京100195 [2]中国地质调查局天津地质调查中心,天津300170 [3]中国地质调查局泥质海岸带地质环境重点实验室,天津300170

出　　处：《地质学报》2023年第2期553-564,共12页Acta Geologica Sinica

基　　金：中国地质调查局项目(编号12120114007701);国家自然科学基金项目(编号41972196);北京市地质矿产勘查开发局项目(编号PXM2019_158203_000005)联合资助的成果。

摘　　要：磁性地层学结合宇宙成因核素、AMS14C测年为晚新生代可靠的长序地质年代框架建立提供了有效快捷手段。在北京平原东南部钻取的NBT1全取芯钻孔进行了详细的磁性地层学研究,400 m钻孔335块样品识别出10个正极性和9个负极性时段,记录了布容(Brunhes)、松山(Matuyama)、高斯(Gauss)、吉尔伯特(Gilbert)极性时,孔底进入到4.2 Ma的Gilbert负极性时。以岩性组合、26Al/10Be、AMS14C年代学为基础,结合测井沉积相分析,判断钻孔上新世晚期地层底界位于319.60 m,第四系下更新统、中更新统、上更新统底界分别位于214.80 m、70.60 m、59.25 m。在上新世约4.2~3.5 Ma发育了6期明显的冲洪积扇的快速沉积过程,第四纪早更新世以曲流河沉积体系为主,中更新世以湖沼沉积为主,夹分支河道沉积,沉积厚度相对较薄,晚更新世以分支河道-湖沼沉积为主,其顶部末次盛冰期浊黄橙色硬质黏土发育。钻孔包含了3个沉积速率较高(>150 m/Ma)的时期,分别为3.58~3.33 Ma、1.945~1.778 Ma和0.126~0.010 Ma,与上新世以来青藏高原隆升扩展及华北地区晚更新世构造活化在时间上具有一致性,揭示了华北地区的沉积构造演化对青藏高原隆升具有一定响应。Magnetostratigraphy,combined with cosmogenic and AMS14C dating,provides an effective method to establish reliable geochronological framework for the late Cenozoic Era.In this paper,the authors present the results of magnetostratigraphic investigations in drill hole NBT1 in southeast of Beijing Plain.In the NBT1 magnetostratigraphy,containing 335 samples collected from the borehole at an interval of 0.2~0.4 m,except for the sand and gravel lay,with reliable ChRMs,10 normal and 9 reverse magnetozones were identified.The strata recorded the palaeomagnetic Brunhes,Matuyama,Gauss and Gilbert polarity chrons,and the bottom horizon was near 4.2 Ma on the palaeomagnetic polarity column.The analysis of the lithology,26Al/10Be,AMS14C,log facies and sedimentary facies for the borehole suggests the strata between 319.00~214.80 m belongs to late Pliocene,and the upper strata of 214.80 m,which is the significant lithologic interface,belongs to Quaternary.At about 4.2~3.5 Ma,six periods of rapid deposition of alluvial and diluvial fans occurred.The Early Pleistocene(214.80~70.60 m)was dominated by a meandering river system.The middle Pleistocene was mainly composed of lacustrine deposits with branched channel deposits,and the sedimentary thickness was relatively thin.The Late Pleistocene was dominated by branched channels-lacustrine deposits,and the top developed hard clay during the Last Glacial Maximum.Given the chronostratigraphic scale,three stages of relatively high sedimentation rate(>150 m/Ma)can be revealed from drill hole NBT1,i.e.,3.58~3.33 Ma,1.945~1.778 Ma and 0.126~0.010 Ma,respectively.They have good comparability on the time scale with extension and uplift of the Tibetan Plateau and Late Pleistocene tectonic activation in North China.It is suggested that the uplift of plateau might also have had a significant impact on sedimentary and tectonic movement for the North China Plain.

关 键 词：磁性地层 上新世 冲洪积扇 宇宙成因核素测年 第四系 北京平原 

分 类 号：P548[天文地球—构造地质学] P539.3[天文地球—地质学]