甘肃天水全新世黄土—古土壤序列化学风化特征及其古气候意义  

Chemical Weathering Characteristics and Its Climate Significance of Holocene Loess-paleosol Sequence in Tianshui of Gansu Province

作　　者：刘俊余 查小春 黄春长 庞奖励 周亚利 李洋 LIU JunYu;ZHA XiaoChun;HUANG ChunChang;PANG JiangLi;ZHOU YaLi;LI Yang(School of Geography and Tourism,National Experimental Teaching Demonstration Center,Shaanxi Normal University,Xi'an 710062,China)

机构地区：[1]陕西师范大学地理科学与旅游学院地理学国家级实验教学示范中心,西安710062

出　　处：《沉积学报》2018年第5期937-945,共9页Acta Sedimentologica Sinica

基　　金：中央高校基本科研业务费专项基金(GK201601006);国家自然科学基金项目(71471071)~~

摘　　要：对甘肃天水地区师家崖典型黄土—古土壤剖面化学元素的测定和分析结果表明:该剖面中氧化物SiO_2、Fe_2O_3、K_2O和Al_2O_3含量变化趋势基本一致,均在古土壤层(S_(0上)和S_(0下))中较高,黄土层(L_0、L_1和L_t)中较低;而氧化物CaO和Na_2O变化呈相反趋势;根据钙镁比(Ca/Mg)、钾钠比(K/Na)、淋溶系数、退碱系数、残积系数和化学蚀变系数(CIA)等化学参数的统计分析结果,揭示了古土壤层形成时期风化成壤作用强烈,黄土层堆积时期风化成壤作用微弱的规律;以Ti为参比,Si、Fe、K和Al相对富集,而Na和Ca发生不同程度的淋溶,总体处于脱Ca、Na的低等化学风化阶段;SJY剖面全新世以来的沉积环境分为化学风化较弱期、波动增强期和减弱期,记录了该区域气候经历了早全新世温凉、中全新世温暖湿润但不稳定,晚全新世凉干的演变过程,对天水地区的古气候变化具有重要意义。The analysis of major elements in samples from the Shijiaya(SJY)profile in Tianshui of Gansu Province,China showed the similar curves trend of SiO 2,Fe 2 O 3,K 2 O,and Al 2 O 3,with relatively high concentration all in the paleosol layer while lower in the loess.However,the variation tendency of CaO and Na 2 O were different from that of SiO 2,Fe2O3,K2O and Al 2 O 3.Some typically chemical parameters in the SJY Profile such as K/Na radio,Ca/Mg radio,residual coefficient,leaching coefficient,the chemical index of alteration(CIA)indicated that chemical weathering was strong during the paleosol deposition and weak during the loess loading.Chemical activity of various elements on the section showed obvious variability.Compared to the stable element Ti,other major elements such as Ca and Na were migrated and leached,while the elements Si、Fe、K and Al were enriched,probably indicating some incipient stage of chemical weathering.The chemical weathering process of the Shijiaya profile could be divided into three stages,the stage of regional chemical weathering was relatively weaker,then it was unstedaily stronger and finally became weaker and weaker.The climate was cool in early Holocene(11 500-8 500 a B.P.),generally warm and humid during mid Holocene(8 500-3 100 a B.P.),and then became no stable with climatic fluctuation at 7 000-6 000 a B.P..In the late Holocene(3 100 a B.P.-today),the climate entered a period of relatively cool with less rain.

关 键 词：黄土-古土壤 地球化学 师家崖 常量元素 

分 类 号：P532[天文地球—古生物学与地层学]