约900 ka前后冰期夏季风降水减弱:东北平原湖相沉积物的粒度证据  

Decreasing summer monsoon precipitation during glacial at ca.900 ka:Evidence from grain size variation of lacustrine deposits from the Northeast Plain of China

作　　者：詹涛 曾方明[4] 杨业[1,2] 葛俊逸 马永法[1,2] 张俊 姜侠 黄荣富 梁彦霞 李峨 王逊 周鑫 邓成龙[3] Zhan Tao;Zeng Fangming;Yang Ye;Ge Junyi;Ma Yongfa;Zhang Jun;Jiang Xia;Huang Rongfu;Liang Yanxia;Li E;Wang Xun;Zhou Xin;Deng Chenglong(The General Institute of Ecological Geology Survey and Research of Heilongjiang Province,Harbin 150030,Heilongjiang;Key Laboratory of Black Soil and Water Resources Research of Heilongjiang Province,Harbin 150036,Heilongjiang;State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029;Qinghai Institute of Salt Lakes,Chinese Academy of Sciences,Xining 810008,Qinghai;Institute of Vertebrate Paleontology and Paleoanthropology,Chinese Academy of Sciences,Beijing 100044;Heilongjiang Bureau of Geology&Mineral Resources,Harbin 150036,Heilongjiang;School of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026,Anhui)

机构地区：[1]黑龙江省生态地质调查研究总院,黑龙江哈尔滨150030 [2]黑土地水土资源研究省级重点实验室,黑龙江哈尔滨150036 [3]中国科学院地质与地球物理研究所,岩石圈演化国家重点实验室,北京100029 [4]中国科学院青海盐湖研究所,青海西宁810008 [5]中国科学院古脊椎动物与古人类研究所,北京100044 [6]黑龙江省地质矿产局,黑龙江哈尔滨150036 [7]中国科学技术大学地球和空间科学学院,安徽合肥230026

出　　处：《第四纪研究》2020年第6期1431-1440,共10页Quaternary Sciences

基　　金：国家自然科学基金项目(批准号:41888101和41822707);黑龙江省国土资源科研类项目(批准号:201407);自然资源部公益性科研专项项目(批准号:201311137)共同资助。

摘　　要：中更新世转型(mid-Pleistocene Transition,简称MPT)期间,除了冰量周期由40 ka向100 ka的特征转变之外,约900 ka以后,高纬冰量、全球海平面和大气CO2/大洋碳库的变幅也都发生了明显变化,这些因素对东亚夏季风的演化产生了深远影响。但关于此时期东亚夏季风降水的变化趋势及其驱动机制,目前尚存在不同看法。本文在前期古地磁和光释光(optically stimulated luminescence,简称OSL)年代框架的基础上,基于东北平原QAL钻孔上部71 m的沉积物粒度重建了夏季风降水演化序列。结果表明:1)时间跨度为1180~450 ka的林甸组和令字组均为较细颗粒的湖相沉积,且林甸组明显较令字组颗粒粗;2)粒度粗的层位代表低湖面阶段,反映降水少,为冰期,反之亦然;3)小波分析显示约900 ka后,100 ka周期特征明显,为通过与深海氧同位素对比获得更精细的年龄序列奠定基础;4)约900 ka后,冰期的降水有明显减弱的趋势。高纬冰量扩张造成的全球海平面下降导致更多陆地暴露出海平面,增加了大洋水汽的输送距离,可能是降水减少的一个影响因素。大西洋经向翻转流(Atlantic Meridional Overturning Circulation,简称AMOC)减弱,热带太平洋区域"热带辐合带"(Intertropical Convergence Zone,简称ITCZ)南移,可能是东亚夏季风降水减弱的另一重要原因。古湖相沉积能够用来重建长尺度夏季风降水变化,未来应加强东亚季风区不同区域古湖泊沉积研究,进而弥补长尺度夏季风演化研究存在的不足,这将有助于更好理解轨道尺度夏季风演化的动力机制。The mid-Pleistocene transition(MPT)is characterized by not only the transition of the ice cycles from 40 ka to 100 ka,but also changes in amplitude of high latitude ice sheet,global sea level and CO2/ocean carbon storage after ca.900 ka,which exert profound influence on the evolution of the East Asian summer monsoon.However,there are different views on the trend of the East Asian summer monsoon precipitation(EASMP)during this period and its driving mechanism.Previous studies based on grain size and pollen percentages in loess indicate a decreasing trend of the EASMP after MPT,which is supported by pollen record from alluvial sediments in North China.This trend was linked to the expansion of global ice volume.On the contrary,results of magnetic susceptibility,carbonate content,minerals and chemical weathering indices of loess show that the EASMP after MPT increased gradually.The increasing trend of the EASMP was related to different forcing factors,including the uplift of the Tibetan Plateau,and the increasing of the sea surface temperature variability in the tropical East-West Pacific Ocean and the frequency of La Niña phenomenon.Upon published chronology from paleomagnetism and OSL(optically stimulated luminescence)dating,a new EASMP record was reconstructed in this paper on the basis of grain size in sediments from Core QAL(44°49'04″N,123°48'46″E),with 120.54 m drilling depth.The grain size of the samples from 0~71 m were analysed with 10 cm intervals.The results show that:(1)There are relative fine-grained lacustrine sediments(19.5~71.0 m)during 1180~450 ka,with coarser grains,whose average value in silty sand layer is median particle size 36μm,>32μm percentage content 53%,>63μm percentage content 29.7% in Lindian Formation and finer ones,whose average value in silty sand layer is median particle size 32μm,>32μm percentage content 46%,>63μm percentage content 26.7% in Lingzi Formation;(2)Grain size of the sediments increased during the glacial periods,showing low lake levels and less EASMP;(3)100-

关 键 词：中更新世转型 东亚夏季风降水 东北平原 湖相沉积 粒度 

分 类 号：P532[天文地球—古生物学与地层学] P534.631[天文地球—地质学]