渭河盆地南缘早更新世风成相和湖相沉积环境演化  

Sedimentary evolution revealed by aeolian and lacustrine depositions in the southern margin of the Weihe Basin during the Early Pleistocene

作　　者：王婷 张航[1,4] 孙有斌 Wang Ting;Zhang Hang;Sun Youbin(State Key Laboratory of Loess and Quaternary Geology,Institute of Earth Environment,Chinese Academy of Sciences,Xi′an 710061,China;Center for Excellence in Quaternary Science and Global Change,Institute of Earth Environment,Chinese Academy of Sciences,Xi′an 710061,China;Hubei Engineering University,Xiaogan Hubei 432000,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院地球环境研究所黄土与第四纪地质国家重点实验室,西安710061 [2]中国科学院地球环境研究所第四纪科学与全球变化卓越创新中心,西安710061 [3]湖北工程学院,湖北孝感432000 [4]中国科学院大学,北京100049

出　　处：《地质科技通报》2023年第6期95-105,共11页Bulletin of Geological Science and Technology

基　　金：中国科学院战略性先导科技专项(B类)(XDB40000000);黄土与第四纪地质国家重点实验室开放基金(SKLLQG1831);孝感市自然科学计划项目(XGKJ2023010065)。

摘　　要：受地球轨道参数诱导的太阳辐射变化和两极冰盖消长的共同影响,第四纪气候环境演化表现出阶段性变冷及显著的冰期-间冰期波动特征。位于亚洲季风区关键地带的渭河盆地堆积了新生代以来巨厚的河湖相沉积以及风成沉积,是研究第四纪环境演化的重要区域。盆地堆积的下更新统三门组河湖相地层被认为和古三门湖有密切联系,但目前对于三门组地层年龄和古三门湖演化及其与区域活动演化是否有联系尚未达成共识。相比单一沉积载体研究,选取渭河盆地南缘阎峪风成相黄土和武家堡湖相沉积2种沉积载体进行对比分析,探讨了同期异相沉积记录的粒度和磁化率变化特征,重建了渭河盆地南缘早更新世(距今2.6~1.6 Ma)沉积环境演化。结果表明,阎峪记录的黄土-古土壤序列平均粒径和磁化率变化良好地记录了东亚冬、夏季风的盛衰演化历史;武家堡指示的盆地南缘沉积环境在距今1.95 Ma由湖相转变为风成相沉积,湖相沉积粒径和磁化率变化呈正相关关系,敏感响应湖平面高低波动。风成相与湖相记录揭示了渭河盆地边缘早更新世环境演化经历了[2.6,1.95)Ma的湖盆演化和[1.95,1.6]Ma的湖盆萎缩-风成相堆积,湖盆萎缩受黄河贯通影响强烈。The Quaternary climate is characterized by a notable cooling and significant glacial-interglacial fluctuations driven by the influence of orbital-induced insolation and bipolar ice-volume variability.The Weihe Basin,located in the critical zone of the Asian monsoon region,accumulated thick fluvial-lacustrine deposition and aeolian deposition since the Cenozoic,which is a key placeto explore the environmental evolution during the Quaternary period.The fluvial-lacustrine strata of the Sanmen Formation in the Weihe Basin are considered to be closely related to Palaeo-Sanmen Lake.However,the relationship among the stratigraphic age of the Sanmen Formation,the evolution of the palaeolake as well as the evolution of regional tectonics is still under much debated.In this work,the magnetic susceptibility and grain size records from two sections(Yanyu and Wujiabu)in the southern margin of the Weihe Basin have been generated to investigate sedimentary evolution during the interval of 2.6-1.6 Ma.The mean grain size(MGS)and magnetic susceptibility(MS)of the Yanyu loess exhibit large-amplitude variations as proxies for the East Asian winter and summer monsoons.The MGS and MS variations in theWujiabu section show that lithology changes from lacustrine to aeolian facies occurred at 1.95 Ma in the southern margin of the Weihe Basin.In lacustrine environments,MGS is positively correlated with MS and is sensitive to fluctuations in lake level linked with monsoonal precipitation.Overall,the climatic characteristics on the margin of the Weihe Basin during the early Pleistocene can be divided into two intervals:①the lake level frequently fluctuated during 2.6-1.95 Ma,②the lake shrank from 1.95 to 1.6 Ma.We suggest that the disappearance of Palaeo-Sanmen Lake was affected by the development and integration of the Yellow River.

关 键 词：渭河盆地 早更新世 湖相沉积 风成黄土 古三门湖 

分 类 号：P618.13[天文地球—矿床学]