宁夏清水河盆地晚更新世两期湖相沉积物的形成时代、沉积环境及构造背景  

Age,sedimentary environment and tectonic setting of two lacustrine sediments of the Late Pleistocene in Qingshuihe Basin,Ningxia

作　　者：李明涛 李黎明 田景雄 梁志荣 谈震 陆茂欣 LI Mingtao;LI Liming;TIAN Jingxiong;LIANG Zhirong;TAN Zhen;LU Maoxin(School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China;Ningxia Institute of Geological and Mineral Resources Survey,Yinchuan 750021,Ningxia,China;Ningxia Institute of Basic Geological Survey,Yinchuan 750021,Ningxia,China)

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]宁夏回族自治区矿产地质调查院,宁夏银川750021 [3]宁夏回族自治区基础地质调查院,宁夏银川750021

出　　处：《地质通报》2022年第2期306-314,共9页Geological Bulletin of China

基　　金：中国地质调查局项目《特殊地质地貌区填图试点》(编号:DD20160060)。

摘　　要：为了解宁夏清水河盆地晚更新世以来的沉积、构造演化规律,采用钻探、粒度分析、光释光测年等技术,对盆地中部发现的2期晚更新世湖相地层进行了沉积学、年代学研究。结果表明,下部湖相地层萨拉乌苏组的形成时代为76~63 ka,上部湖相地层水洞沟组形成时代为25~11 ka,二者之间存在明显的侵蚀面。根据沉积证据和粒度分析结果,将萨拉乌苏组自下而上划分为4个沉积阶段,构成了一个完整的湖进-湖退序列,代表了一期温暖湿润的气候环境;而水洞沟组为干冷环境下形成的浅湖。构造、环境对比分析表明,清水河盆地2期古大湖的形成、消亡指示该地区晚更新世经历了拉张-挤压-拉张的构造转换。两次拉张作用是萨拉乌苏湖和水洞沟湖形成的主要因素,古大湖发育的间断期存在的强烈构造隆升事件是导致萨拉乌苏湖消亡的根本原因,末次冰期MIS4和MIS2晚期的异常寒冷气候也是古湖衰退的原因之一。清水河盆地2期古湖的演化规律,为研究青藏高原周缘晚更新世古大湖形成与演化、古气候变迁及青藏高原的隆升提供了重要的证据。The sedimentology and chronology of the two Late Pleistocene lacustrine strata discovered in the middle of the basin were studied by means of drilling,grain size analysis and optically released luminescence dating in order to understand the sedimentary and tectonic evolution since the Late Pleistocene in Qingshuihe Basin,Ningxia.The results show that the lower part is the Salawusu Formation and the upper part is Shuidonggou Formation,which were formed at 76~63 ka and 25~11 ka,respectively.In addition,there is an obvious erosion surface between them.According to sedimentary evidence and grain size analysis results,the Salawusu Formation can be divided into four sedimentary stages from bottom to top,which constitute a complete set of lacustrine prograding and lacustrine recession sequence,representing a warm and humid climate environment.The Shuidonggou formation is a shallow lake formed in cold and dry environment.The comparative analysis of structure and environment shows that the formation and disappearance of the two ancient lakes in the late Pleistocene in Qingshuihe Basin indicate the transition of extensional-compression-extensional tectonic activity.The two extensional events were the main factors for the formation of Salawusu Lake and Shuidonggou Lake.The strong tectonic uplift event in the discontinuous period of the development of the ancient lake is the fundamental cause of the demise of the Salawusu Lake,and the abnormal cold in the late MIS 4 and MIS 2 of the last glacial period is also one of the reasons for the decline of the ancient lake.The evolution of the two ancient lakes in Qingshuihe Basin provides important evidence for the study of the formation and evolution of the ancient lakes,paleoclimate changes and uplift of the Tibetan Plateau during the late Pleistocene.

关 键 词：晚更新世 青藏高原东北缘 清水河盆地 古湖泊 古环境演化 地质调查工程 

分 类 号：P534.631[天文地球—第四纪地质学] P597.3[天文地球—古生物学与地层学]