末次冰期山西洪洞高分辨率粒度和磁化率记录的H5事件及其气候演化意义  

Heinrich-5Event revealed by high-resolution grain-size and magnetic susceptibility records and its significance of climate evolution in the last glacial at Hongtong,Shanxi,China

作　　者：卫蕾华[1] 蒋汉朝[2] 何宏林[3] 徐岳仁[4] 高伟[3] 魏占玉[3] WEI Leihua;JIANG Hanchao;HE Honglin;XU Yueren;GAO Wei;WEI Zhanyu(Geophysical Exploration Center,China Earthquake Administration,Zhengzhou 450002,China;State Key Laboratory of Active Tectonics and Volcano,Institute of Geology,China Earthquake Administration,Beijing 100029,China;State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China;Institute of Earthquake Science,China Earthquake Administration,Beijing 100036,China)

机构地区：[1]中国地震局地球物理勘探中心,郑州450002 [2]中国地震局地质研究所地震动力学国家重点实验室,北京100029 [3]中国地震局地质研究所活动构造与火山重点实验室,北京100029 [4]中国地震局预测研究所,北京100036

出　　处：《海洋地质与第四纪地质》2018年第4期193-202,共10页Marine Geology & Quaternary Geology

基　　金：地震行业科研专项项目"霍山山前断裂带1/5万地质填图"(200908001);驻马店市活断层探测与地震危险性评价项目

摘　　要：源于北大西洋的末次冰期千年尺度波动的Heinrich事件在东亚地区不同气候记录中得到较为广泛的识别。但是,哪一次事件对东亚乃至北半球影响最显著还不清楚。山西临汾盆地作为中国东部的山间盆地保存了较为广泛的黄土沉积。本次研究对山西洪洞县洞峪沟剖面末次冰期厚10.5m的黄土进行光释光测年,0.5cm间距的粒度测量、磁化率测量。结果显示,该剖面跨越67.7~13.0ka,粒度和磁化率记录所反映的气候特征可以以H5事件(47.3ka)为分界点分为前后两个时期。其中,早期(67.7~47.3ka)粗粉砂(20~63μm)和砂含量(>63μm)整体较低而磁化率较高,反映该时期亚洲冬季风较弱而夏季风较强;晚期(47.3~13.0ka)粗粉砂含量和砂含量整体较高而磁化率较低,反映该时期亚洲冬季风明显增强而夏季风明显减弱。山西洪洞以H5事件(约47.3ka)为分界点的末次冰期气候演化模式在东亚、东地中海乃至北美均可以对比,可能是北极地区冰量在这一时期得到显著发展,导致东亚乃至北半球气候向寒冷方向发生显著变化。这一认识对理解东亚MIS3气候演化趋势具有一定意义。The millennial-scale fluctuations of Heinrich events during the last glacial stage initiated from the North Atlantic have been widely discovered in East Asia.However,which event has the most remarkable impact on East Asia or even the Northern Hemisphere remains unclear.There are widely distributed loess deposits,the best climate proxies,in the Linfen Basin,Shanxi province.In this study,we collected OSL dating samples and powder samples at a 0.5 cm intervals to analyze grain size and magnetic susceptibility for a 10.5 m thick loess sequence at Dongyugou of Hongtong,Shanxi.Dating results show that the section is in an age range from67.7~13.0 ka.Grain size and susceptibility data suggest an obvious H5 climate event of the last glacial at the depth of 47.3 ka.Therefore,this cores could be divided into two parts.In the early time（67.7~47.3 ka）,the content of coarse silt（20~63μm）and sand fraction（〉63μm）was overall low,but magnetic susceptibility was relatively high.On the contrary,in the later time（47.3~13.0 ka）,the content of coarse silt and sand fractions increases,while magnetic susceptibility is low.This implies that Asian winter monsoon was weak and summer monsoon was strong in the early time,while in the later period,Asian winter monsoon substantially enhanced and summer monsoon significantly weakened.The evolution models of last glacial climate demarcated by H5（~ 47.0 ka）are comparable in East Asia,EasternMediterranean and even North America.It is supposed that ice accumulation in the Arctic in this period led to climate changed colder in East Asia and the Northern Hemisphere.This cognition plays an important role in deep understanding of the evolution trend of MIS3 climate in East Asia.

关 键 词：粒度 磁化率 光释光测年 黄土 H5事件 临汾盆地 

分 类 号：P532[天文地球—古生物学与地层学]