青藏高原东北缘红寺堡盆地晚更新世沉积物元素地球化学特征及其环境指示意义  

Elemental geochemical characteristics and environmental significance of Late Pleistocene sediments in the Hongsibu Basin,northeastern margin of the Qinghai–Tibet Plateau

作　　者：刘博华 吴芳[2,3,4] 张绪教 崔加伟[2,3,4] 董晓朋 LIU Bohua;WU Fang;ZHANG Xujiao;CUI Jiawei;DONG Xiaopeng(School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China;Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081,China;Key Laboratory of Paleomagnetism and Tectonic Reconstruction,Ministry of Natural Resources,Beijing 100081,China;Key Laboratory of Active Tectonics and Geological Safety,Ministry of Natural Resources,Beijing 100081,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]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]自然资源部活动构造与地质安全重点实验室,北京100081

出　　处：《地质通报》2024年第1期33-45,共13页Geological Bulletin of China

基　　金：中国地质调查局项目《黄河流域中游重要发展区区域地质调查》(编号:DD20221644)和《武威-固原地貌边界带基础地质调查》(编号:DD20190018)。

摘　　要：红寺堡盆地位于青藏高原东北缘弧形构造带最前缘与鄂尔多斯高原西部的交界位置,区域生态环境脆弱,但由于地表覆盖严重,缺乏完整的露头剖面,一直制约着生态环境演变过程的研究。本文基于红寺堡盆地窑山凹陷ST1钻井序列,采用光释光测年的方法,建立了晚更新世地层年代格架,同时系统分析了70个样品的主量、微量元素组成,依据地球化学指标重建晚更新世以来的气候环境演变过程。研究认为:马兰黄土与萨拉乌苏组的界限年龄约为67.57±7.88 ka,预示着由古湖向风成环境的过渡,区域生态环境逐步恶化。元素地球化学特征也记录了该时期的气候环境变迁过程,CIA值、Al_(2)O_(3)/Na_(2)O、K_(2)O/Na_(2)O值及粘土矿物含量指示了红寺堡盆地晚更新世经历了干旱-温暖-干旱的古气候演化过程;Rb/Zr、Sr/Ba值反映红寺堡盆地萨拉乌苏组沉积时期为封闭的湖盆环境,沉积水体深度自萨拉乌苏组一段开始加深,在萨拉乌苏组二段达到最大深度,萨拉乌苏组三段水体逐步变浅直至马兰黄土沉积时期古湖彻底消亡。该研究成果从元素地球化学的角度为青藏高原东北缘晚更新世地层的沉积环境演化提供了新依据。The Hongsibu Basin is located at the junction of the forefront of the arc-shaped structural belt on the northeastern margin of the Qinghai–Tibet Plateau and the western part of the Ordos Plateau.The regional ecological environment is fragile,yet the lack of complete outcrop profiles due to extensive surface coverage has long hindered research into the evolution of the ecological environment.This study,based on the drilling sequence of Well ST1 in the Yaoshan Sag of the Hongsibu Basin,employs optically stimulated luminescence dating to establish a Late Pleistocene stratigraphic chronology. Additionally, it systematically analyzes themajor and trace element compositions of 70 samples and reconstructs the climatic and environmental evolution processes since the LatePleistocene based on geochemical indicators. The study suggests that the boundary age between the Malan loess and the SalawusuFormation is approximately 67.57 ± 7.88 ka, indicating a transition from an ancient lake to an aeolian environment, accompanied by agradual deterioration of the regional ecological environment. The geochemical characteristics of elements also recorded the climatic andenvironmental changes during this period. Geochemical indicators such as the CIA value, Al_(2)O_(3)/Na_(2)O, K_(2)O/Na_(2)O ratios, and claymineral content indicate a paleoclimatic evolution process of arid-warm-arid in the Hongsibu Basin since the Late Pleistocene. Rb/Zrand Sr/Ba values reflect a closed lake basin environment during the deposition of the Salawusu Formation in the Hongsibu Basin. Thedepth of the sedimentary water body increased from the first section of the Salawusu Formation, reaching its maximum depth in thesecond section, and gradually became shallower in the third section until the complete disappearance of the ancient lake during thedeposition of the Malan loess. The research results provide a new basis for the sedimentary environment evolution of the LatePleistocene in the northeastern margin of the Qinghai–Tibet Plateau from the perspective

关 键 词：晚更新世 沉积环境 马兰组 萨拉乌苏组 元素地球化学 红寺堡盆地 青藏高原 

分 类 号：P595[天文地球—地球化学] P534.631[天文地球—地质学]