摘要
对黄土高原中部洛川黄土堆积进行了系统的粒度和磁化率测量，以黄土－古土壤中的粗颗粒组分，即＞３０μｍ颗粒的百分含量作为冬季风强度代用指标，根据一个独立的时间标尺，发现在１４５～１６５、２４０～２８０、３２０～３５０、３９０～４４０、６００～６４０、８６０～８９０、９００～９３０和１３３０～１４００ｋａＢ．Ｐ．东亚冬季风强度存在千年尺度快速变化的特征，冬季风加强事件的持续时间在１．４～７．２ｋａ之间，变化幅度也不相同；周期分析结果表明，这些古气候变化存在１．８９～４．０ｋａ之间的周期，由于时间标尺的精度还有待于进一步提高，在这里没有把冬季风强度变化与北大西洋沉积物记录的古气候事件进行对比，但是，实验结果证明在早。
Grain size and magnetic susceptibility measurements on samples from a typical loess palaeosol sequence on the Loess Plateau of Central China are used to reconstruct the Pleistocene East Asian monsoon climate.The coarse grained fraction,i.e.the weight percentage >30μm of the bulk grain size distribution,is used as a sensitive proxy index of the East Asia winter monsoon strength.On the basis of an absolute time scale,time series variations of this proxy show that winter monsoon strengths varied on millennial time scales during the periods of 145～165,240～280,320～350,390～440,600～640,860～890,900～930 and 1 330 ～ 1 400 kaB.P.The wavelength of these climatic oscillations varied between 1.89 and 4.0 ka,as is shown by spectral analysis using the multi taper method.Although numerical simulation experiments show that high frequencies also can arise from measurement errors in the grain size analysis,the frequencies prove to be sufficiently stable when the spectral analysis is repeated with a different number of tapers.For the time being,we do not correlate these climatic oscillations with paleoclimatic records in the North Atlantic deep sea sediments because both time scales should be further improved.However,our data certainly demonstrate that millennial scale East Asian winter monsoon variations in the last 1.4 million years can be detected from terrestrial loess records.
出处
《海洋地质与第四纪地质》
CAS
CSCD
北大核心
1999年第2期75-83,共9页
Marine Geology & Quaternary Geology
基金
中国科学院"九五"重大项目
关键词
古气候
季风
风强度
东亚季风
早更新世
East Asia winter monsoon millennial time scale variability Middle and Early Pleistocene
