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渭河流域全新世古洪水滞流沉积物地球化学特征 被引量:7

Geochemical Characteristics of Holocene Palaeoflood Slackwater Deposits in Weihe River Basin
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摘要 对渭河流域野外实地详细调查,在渭河中游发现了具有典型古洪水滞流沉积物(SWD)的全新世黄土-古土壤沉积剖面。根据地层学对比和OSL测年,确定渭河流域在3200-2800aB.P.发生了特大古洪水事件。对沉积物地球化学特征分析表明,SWD为典型的古洪水滞流沉积物,各化学元素和氧化物的变异系数大,元素数据分布较为分散;Fe2O3、Al2O3、Ba、Cr、Cu、V、Rb含量高于S0和L0,SiO2、Zr含量低于S0和L0;化学元素粒度效应表明,SWD粒径小、粘粒强,是在滞流环境的水动力条件下沉积而成;通过气候指标Rb/Sr和Ba/Sr分析,认为古洪水滞流沉积物(SWD)记录的3200-2800aB.P.的特大古洪水事件,是在全新世大暖期结束之际,因夏季风减弱、气候系统不稳定、降水变率较大所导致的。 On the basis of field exploration,Holocene palaeoflood slackwater deposits existing in loess-paleosols profile were found in middle reaches of Weihe river.According to stratigraphic configuration and OSL dating for slackwater deposits and Loess-paleosol samples,the age of the extreme palaeoflood is fixed between 3200 a B.P.and 2800 aB.P..Analysis of chemical elements shows that that the slackwater deposits were typical in the study area,and the chemical elements and oxide,variation coefficient of slackwater deposits was comparatively large,elements distribution was comparatively dispersed.The contents of Fe2O3,Al2O3,Ba,Cr,Cu,V,Rb in palaeoflood slackwater deposits were higher than that in paleosol and modern loess formation,and the content of SiO2,Zr in palaeoflood slackwater deposits were lower than that in paleosol and modern loess formation,according to the effect of element size,slackwater deposits,size fraction was small and its clay particle was relatively more,so the slackwater deposits deposited in weak hydrodynamic condition.Though climatic index analysis such as Rb/Sr and Ba/Sr,revealing that the extreme palaeoflood recorded between 3200 a B.P.and 2800 a B.P.occurred in the late Holocene megathermal period.In that period,climate environment is unstable,the summer monsoon remitted,and the rainfall variability is high.
出处 《水土保持学报》 CSCD 北大核心 2012年第1期106-111,共6页 Journal of Soil and Water Conservation
基金 国家自然基金项目(41030637) 中央高校基本科研业务费专项(GK200901007)
关键词 渭河流域 全新世 古洪水流沉积物 地球化学特征 Weihe river basin Holocene palaeoflood slackwater deposits geochemical characteristics
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