若尔盖盆地黄河第二级阶地沉积序列及其记录的河湖演变过程  

Sedimentary stratigraphy of the second terrace of the Yellow River and its implications for the evolution of river-lake system within the Zoige Basin,NE Tibetan Plateau

作　　者：朱艳 王思凯 张玉柱 王宁练 黄春长 庞奖励 金瑶 曹鹏鹏 黄晓玲 肖奇立 周晋鹏 李孟停 ZHU Yan;WANG Sikai;ZHANG Yuzhu;WANG Ninglian;HUANG Chunchang;PANG Jiangli;JIN Yao;CAO Pengpeng;HUANG Xiaoling;XIAO Qili;ZHOU Jinpeng;LI Mengting(Shaanxi Provincial Key Laboratory of Earth Surface System and Environmental Carrying Capacity,College of Urban and Environmental Sciences,Northwest University,Xi'an 710127,China;School of Geography and Tourism,Shaanxi Normal University,Xi'an 710119,China)

机构地区：[1]西北大学城市与环境学院陕西省地表系统与环境承载力重点实验室,西安710127 [2]陕西师范大学地理科学与旅游学院,西安710062

出　　处：《地理学报》2025年第3期758-777,共20页Acta Geographica Sinica

基　　金：国家自然科学基金项目(42277449,42271046,42171092);西北大学2024年研究生科研创新项目(CX2024179)。

摘　　要：河流阶地沉积序列是记录区域河流水系演变和环境变迁的重要信息载体。通过对青藏高原东北部若尔盖盆地开展广泛细致的野外调查,在盆地中心黄河第二级阶地上发现了层序清晰完整的沉积序列。在野外对娘伊曲(NYQ-A)剖面进行系统地层划分和样品采集的基础上,结合室内粒度、地球化学元素、古生物和光释光(OSL)/AMS^(14)C测年等分析结果,揭示了剖面中不同成因类型沉积层的特征及其记录的环境信息,并探究了剖面中若尔盖古湖相沉积层所记录的湖泊水位变化及其成因。研究结果表明:①该剖面沉积序列由下到上依次为若尔盖古深湖相A沉积层、若尔盖古浅湖相A沉积层、若尔盖古深湖相B沉积层、若尔盖古浅湖相B沉积层、黄河漫滩相古洪水泛滥沉积层、风成黄土层和现代草甸土层。②古深湖相A沉积层记录的古深湖环境发育在(51.82±2.34)ka之前,处于深海氧同位素3c阶段(MIS 3c)暖湿期,因该时段气候温暖湿润,使得湖泊流域内降水和冰川积雪融水丰富,古湖水位较高。古浅湖相A沉积层记录的古浅湖环境发育在(51.01±2.19)~(39.54±1.72)ka,对应于MIS 3b冷干期,因该时段湖泊流域水热组合条件差,气候相对冷干,导致古湖水位降低。古深湖相B沉积层所记录的古深湖环境发育在(39.18±2.03)~(36.77±1.66)ka,对应于MIS 3a暖湿期,湖泊流域内因为气候温暖湿润,丰富的降水和冰川积雪融水又重新汇入盆地,导致古湖水位再次升高。③值得注意的是,古浅湖相B沉积层记录了若尔盖古湖在(36.77±1.66)ka(处于MIS 3a暖湿期),由古深湖环境向着浅水湖沼草地环境发生了突变。结合前人关于若尔盖古湖发展演变的研究成果,进一步有力地证实了在暖湿的气候背景和东昆仑大断裂东段强烈的构造运动影响下,使得古黄河溯源侵蚀和下切侵蚀作用加剧。在37 ka左右,古黄河袭夺了若尔盖古湖,造成湖水Based on extensive and detailed field investigations in the Zoige Basin on the NE Tibetan Plateau,the Niangyiqu(NYQ-A)section was found on the second terrace of the Yellow River in the basin.Through systematic stratigraphic division and sample collection in the field,combined with laboratory analysis of grain size,geochemical elements,paleontology,and OSL/AMS^(14)C dating,different sedimentary layers in the section and its paleoenvironmental significance were identified.Furthermore,this study focuses on investigating the lake level changes of the Zoige paleolake recorded by the lacustrine deposits and their causes.The results show that:(1)The sedimentary stratigraphy of the section,from bottom to top,consists of the following layers:deep lacustrine deposits A,shallow lacustrine deposits A,deep lacustrine deposits B,shallow lacustrine deposits B,overbank flood deposits of the Yellow River,aeolian loess,and modern meadow soil.(2)The deep lacustrine deposits A,dating to 51.82±2.34 ka,records a deep lake environment of the Zoige paleolake during the(Marine isotope stages)MIS 3c period.During this period,warm and wet climate conditions led to high precipitation and glacial meltwater inflow,resulting in a high paleo-lake level.The shallow lacustrine deposits A formed between 51.01±2.19 and 39.54±1.72 ka,indicating a shallow lake environment of the Zoige paleolake during the MIS 3b period.During this period,cold and dry climate conditions caused a lowered paleo-lake level.The deep lacustrine deposits B accumulated between 39.18±2.03 and 36.77±1.66 ka,inferring a deep lake environment of the Zoige paleolake during the MIS(Marine isotope stages)3a period.During this period,warm and wet climate conditions led to increased precipitation and glacial meltwater,raising the paleo-lake level once again.(3)Notably,shallow lacustrine deposits B records a sudden transition of the Zoige paleolake from a deep lake environment to a shallow marshy environment at 36.77±1.66 ka during the MIS 3a period.Based on the previous studies

关 键 词：若尔盖盆地 黄河阶地 河湖演变 河流袭夺 环境变化 

分 类 号：P534.6[天文地球—古生物学与地层学]