敦化盆地晚全新世泥炭沉积中植硅体古气候记录的时频分析

沉积地层中古气候参数的多层次性以及解释过程中的人为性使古气候重建结果带有一定的误差。采用Morlet一维连续小波变换对敦化盆地吉祥和榆树剖面中植硅体记录的古气候参数进行时频分析,探讨植硅体反演的古气候变化过程。结果表明,吉祥剖面在频率域尺度a≥30时的小波变换系数波谱及能量变化与榆树剖面在a≥20时存在相似性,且均具有6个不同能量聚集区域,因此把敦化盆地晚全新世以来的古气候变迁分为6个阶段：公元前730年以前为温暖降温期;公元前730—公元前205年为温和湿润并逐渐变凉时期;公元前205—公元255年为温暖时期;公元255—525年为降温变冷时期;公元525—1220年为温暖湿润时期;公元1220年以来进入气候波动比较频繁时期。Morlet一维连续小波变换可以有效处理古气候信息的叠加,减小人为性分析带来的误差,在古气候分析中具有很大应用潜力。

Time-frequency Analysis on Palaeoclimate Recorded by Phytolith at the Late Holocene Peat Deposits in Dunhua Basin

Diversity of palaeoclimate parameters in sedimentary stratigraphy and its artificiality in interpretation process bring some inevitable errors.Based on Morlet one-dimensional continue wavelet transform,palaeoclimate parameters recorded by phytolith at Jixiang and Yushu profiles in Dunhua Basin were analyzed by time-frequency,change of palaeo-climat was discussed.The results showed that the wavelet spectrum and energy change at Jixiang profile with no less than 30 frequency scales were similar with that at Yushu profile with no less than 20 frequency scales,and both profiles had six different energy aggregation regions.Changes of palaeoclimate since the Late Holocene in Dunhua Basin was divided into six stages： before BC 730,warm and cooling period;BC 730-BC 205,mild,humid,and gradually cooling period;BC 205-AD 255,warm period;AD 255-525,cooling period;AD 525-1220,warm and humid period;after AD 1220,a stage with more frequent fluctuations.Morlet one-dimensional continue wavelet transform could deal with the superposition of palaeoclimate records effectively and reduce the artificial error,enjoy huge potential for application in palaeoclimate research.