本溪王家崴洞10500～5000aBP石笋记录及区域气候意义

基于典型东亚季风区辽宁省本溪市2支石笋样品(W6与W4),通过9个230 Th年龄和386个氧同位素数据,重建了10 500～5 000aBP期间平均分辨率为12～34a的氧同位素时间变化序列。研究时段石笋δ18 O相对振幅为2.0‰,在平均值约-8.5‰上下波动,指示了早全新世东亚季风强度的长期趋势变化和百年尺度振荡信息。相同时段本溪王家崴洞、湖北三宝洞、贵州董哥洞石笋δ18 O记录对比结果表明,全新世石笋δ18 O长期增加趋势类似于北半球太阳辐射能量变化曲线,但东北地区石笋δ18 O大约在10 500a已达到最大值,早于长江流域以南地区约1 000a,这可能表明全新世亚洲季风降水并不同步变化,可能与热带、亚热带季风系统差异响应于区域大气环流有关。功率谱分析W6石笋δ18 O时间序列发现其存在显著的225和91a的周期,与树轮Δ14 C周期(208和88a)基本一致,揭示了中全新世百年尺度东亚季风变化可能主要响应于太阳活动。

THE MID-HOLOCENE CLIMATE VARIATION INFERRED FROM A DATED STALAGMITE RECORD FROM WANGJIAWEI CAVE,NORTHEAST CHINA

Presented in this paper are the oxygen stable isotope records of the stalagmite dated with 230Th-dating method for Wangjiawei Cave in Liaoning Province,northeastern China.The records provided a clue to the history of Asian summer monsoon for the period of 10.5~5.0 kaBP.There are a series of abrupt and rapid shifts superimposed on a gradually increasing trend,indicating that the East Asian monsoon was unstable during the early Holocene.A comparison of our records to precisely dated contemporaneous stalagmite records from other caves shows that the Wanjiawan record resembles other Holocene speleothem records from subtropical locations.All of these δ18O profiles follow insolation changes,further supporting the idea that insolation is the primary factor inffuencing the Asian summer monsoon.However,a peak monsoon intensity during the early Holocene commenced as early as ~10.5 kaBP in northern China,for example in Wangjiawei and Nuanhe Caves,while this shift appeared 1 000 years later,about ~9 kaBP in Sanbao Cave and Dongge Cave at lower latitudes.It suggests an asynchronous change in summer monsoon precipitation in East Asia during the early Holocene,and the response of the East Asian summer monsoon precipitation to regional atmospheric circulations varied from the south to north due to monsoon intensity changes,resulting from the complex geographical configuration.The spectral analysis of δ18O time series shows cycles around 225a and 91a which are similar with the tree ring cycles of 208a and 88a by Δ14C isotopic data,indicating that solar changes may be,at least partially,responsible for changes in the intensity of the East Asian Monsoon on the centennial time scale during the early Holocene.