辽宁本溪庙洞石笋氧同位素记录的距今4-3千年东亚夏季风演化历史

摘要

Much attention has been paid to the variability in East Asian Summer Monsoon(EASM)during the first few thousand years of late Holocene,due to its potential connection with Chinese civilization development.In this study,a stalagmite MD11 from the Miaodong cave,Benxi,Liaoning province has been employed to reconstruct a high resolution δ18O record during time period between 4.09 ka BP and 2.84 ka BP.The variability in MD11 δ18O is explained to be a proxy index of EASM and(or)local summer monsoon precipitation,with more negative value indicating stronger EASM or more summer precipitation.During 4.09-3.85 ka BP,the EASM was relatively stable,similar to some stalagmite records from southern China,indicating that the well known "4.2 ka" cold event(failure EASM)maybe occurred at least earlier than 4.1 ka BP.In general term,δ18O value is much less negative from 3.85 ka BP until 2.84 ka BP.This observation is together with much lower deposition rate,revealing a long term weakening of EASM.It should be known that a short term(several decades)rebound in intensity of EASM occurred at around 3.05 ka BP.Our observation coincides with that of history document that weak EASM and drought in northern China dominate the time period of 4-3 ka BP.%距今4-3千年正值中华文明确立和发展的重要时期,这个时段的气候变化资料有利于深入理解环境与人类文明发展的相互关系.本研究利用辽宁本溪庙洞石笋MD11,通过230Th定年和高分辨率氧同位素分析,重建了4.09-2.84 ka BP东北地区南部夏季风降水变化历史.4.09-3.85 ka BP时段,东亚夏季风较为稳定,期间在约3.95 ka BP前后出现短暂的夏季风小幅度减弱,与亚洲季风区石笋记录类似,推测4.2 ka事件应早于4.1 ka BP,支持早前南方石笋记录的结论;3.85-2.84 ka BP时段,庙洞石笋沉积速率显著降低,氧同位素整体偏正,说明这段时间内东亚季风总体偏弱,辽宁东部地区夏季风降水偏少,期间只在3.05 ka BP先后出现持续时间约为数十年的夏季风增强过程.