玛曲谷地晚全新世风成黄土化学风化程度与气候变化  

Chemical weathering degree of the Late Holocene aeolian loess and climate change in Maqu Valley

作　　者：王忻宇 庞奖励 黄春长 周亚利 查小春 李瑜琴 赵晓康 翟颖 孙雪晴 WANG Xinyu;PANG Jiangli;HUANG Chunchang;ZHOU Yali;ZHA Xiaochun;LI Yuqin;ZHAO Xiaokang;ZHAI Ying;SUN Xueqing(School of Geography and Tourism,Shaanxi Normal University,Xi'an 710119,China)

机构地区：[1]陕西师范大学地理科学与旅游学院,西安710119

出　　处：《地理研究》2024年第7期1911-1928,共18页Geographical Research

基　　金：国家自然科学基金项目(42271046、42277449、41971116、42071112)。

摘　　要：本文以若尔盖盆地玛曲黄河一级阶地覆盖的老桥西(LQX)剖面为研究对象,对其粒度、磁化率、元素含量及地球化学参数进行研究,用光释光方法进行测年断代,在构建剖面地层年代框架基础上,试图揭示晚全新世以来风成黄土的化学风化特征及记录的环境变化特征。结果显示:(1) LQX剖面地层年代框架为:河流相砂层FS(>3.0 ka)→风沙层AS(3.0~2.5 ka)→下部黄土层L_(02)(2.5~2.3 ka)→土壤层MS_(1)(2.3~1.6 ka)→上部黄土层L_(01)(1.6~0.4 ka)→表土层MS_(0)(0.4 ka~至今)。(2) LQX剖面处于以斜长石风化为主的低等化学风化阶段,且不同地层单元风化成壤强度顺序为L_(02)较弱→MS_(1)最强→L_(01)略有减弱→MS_(0)增强。(3)玛曲谷地晚全新世以来经历了冷干期(3.0~2.5 ka)-凉干期(2.5~2.3 ka)-暖湿期(2.3~1.6 ka)-冷干期(1.6~0.4ka)-暖湿期(0.4 ka~至今)的气候变化,与青藏高原及其他地区古气候信息记录吻合度较高。After extensive and detailed field investigation in the Zoige Basin,a Late Holocene aeolian loess-paleosol section at Laoqiaoxi(LQX)site on the first river terrace(T1)of the Yellow River in the Maqu reach was selected for research.The grain-size distribution,magnetic susceptibility,the distribution characteristics of major elements and the geochemical behavior of the loess surface(such as CIA,alkali degradation coefficient,leaching coefficient,residual coefficient,calcium magnesium ratio,sodium potassium ratio,rubidium strontium ratio,etc.)are studied.Based on the stratigraphic-chronological framework by using OSL dating of aeolian loess in the first order terrace of the Yellow River,this paper attempts to reveal the characteristics of chemical weathering processes of aeolian loess and recorded environmental changes since the Late Holocene.The results showed that:(1)LQX section was formed in the Late Holocene,and its stratigraphic-chronological framework is:Fluvial sand(FS,>3.0 ka)→Aeolian sand(AS,3.0-2.5 ka)→Lower loess(L_(02),2.5-2.3 ka)→Lower soil(MS_(1),2.3-1.6 ka)→Upper loess(L_(01),1.6-0.4 ka)→Surface soil(MS_(0),0.4 ka-present).(2)LQX profile is in the lower chemical weathering stage dominated by the weathering of plagioclase,and the order of intensity of weathering and pedogenesis in different stratigraphic units is:AS is the weakest layer→L_(02) gets weaker→MS_(1) is the strongest layer→L_(01) slightly gets weaker→MS_(0) gets stronger.(3)Since the Late Holocene,the Maqu Valley has experienced the climatic changes:cold and dry period(3.0-2.5 ka),cool and dry period(2.5-2.3 ka),warm and wet period(2.3-1.6 ka),cold and dry period(1.6-0.4 ka),warm and wet period(0.4 ka-present),which is in good agreement with the paleoclimatic information records of the Tibetan Plateau and other areas.This findings provide the first evidence for constructing the trajectory of climate evolution in the region since the Late Holocene,and further enrich the paleoclimate research content in the northeastern Tibe

关 键 词：黄河一级阶地 常量元素 晚全新世 气候变化 LQX剖面 

分 类 号：P534.632[天文地球—第四纪地质学] P512.12[天文地球—古生物学与地层学] P467[天文地球—地质学]