敦化盆地晚全新世泥炭沉积中化学元素记录的古气候分析

Plaeo-climate analysis of the geochemical element records in the Late Holocene peat deposits of Dunhua Basin,NE China

在对敦化吉祥泥炭剖面的Na、K、Mg、Ca、Fe、Cr、Mn、Sr、Ba和Pb等元素进行分析的基础上,采用Morlet一维连续小波分析其时频变化,将剖面晚全新世以来的古气候过程分为6个阶段:公元前730年前的温暖降温期;公元前730年～公元前205年的温和湿润期;公元前205年～公元255年早期温暖湿润,之后变凉干;公元255年～公元525年气候寒冷时期;公元525年～1220年的温暖湿润时期;以及公元1220年～现在的气候波动频繁阶段。为本区泥炭古气候重建及综合对比分析提供了重要的基础素材。

NE China is a transitional zone of the eastern Siberia and the Pacific Ocean,which is between the semiarid and semi humid areas and sensitive to the global changes.Dunhua Basin is located in the mountains between Zhangguangcai Mountain and Changbai Mountain in NE China.The local climate is sensitive to the regional climate changes.Serial records of paleoclimate changes since the Last Glacial Period have been recorded in some uninterrupted peat deposits.This made the Dunhua Basin become one of the important studied areas for the Holocene climate researches in NE China in the past decades.At present,the mean palaeo-research methods here on the peat deposit profiles are almost spore analysis,C-O isotopes analysis,etc.Geochemical element research for the palaeo-climate changes is being more and more practiced,and is being an important way for palaeo-climate research in China.Analysis on the geochemical elements of the peat profile in Dunhua basin will provide some effective evidence for the local palaeo-climate reconstruction.It is one kind of the basic materials for the calculation of the academic model of climate evolution and is helpful to the palaeo-environment study in NE Asia.Geochemical elements Na,K,Mg,Ca,Fe,Cr,Mn,Sr,Ba and Pb of the peat profile in Jixiang,Dunhua area were analyzed and their time-frequency changes were calculated through Morlet wavelet analysis.On the basis of these,the palaeo-climatic process on the studied profile is divided into 6 stages: before 730 BC,warm but cooling;730 BC-205 BC,warm and humid;205 BC-255 AD,warm and humid,but becoming cold in the end;255 AD-525 AD,cold;525 AD-1220 AD,warm and humid;1220 AD-present,changing frequently.This is an important complementarity for the recent Holocene climate research methods in Dunhua basin.Although some unexpected phenomena on some element records might indicate that an urgent study is necessary for the elemental geochemical behaviors in peat deposits,the results of Morlet wavelet analysis showed more impersonal changing information than other analysis,which suggesting its extensive function in the reconstruction researches of the Holocene paleo environment researches.