福建宁化天鹅洞2100～590aBP石笋记录及区域气候意义

2100～590 ABP STALAGMITE STABLE ISOTOPE RECORDS FROM TIAN'E CAVE AND THEIR REGIONAL CLIMATE SIGNIFICANCE

选择位于典型东亚季风区我国东南部福建省宁化县天鹅洞一支石笋样品(TE2),通过3个30 Th年龄和96组稳定同位素测试,重建了2 100～590aBP期间平均分辨率为17年的氧碳同位素时间变化序列。整段石笋δ18 O振幅达2.1‰,在平均值约-6.8‰上下波动,指示了此时期东亚夏季风强度的长期演化趋势和百年尺度振荡信息。该δ18 O记录在2 100～700aBP时段整体呈现出偏正的趋势,这也与同位于东亚季风区的长江中游和尚洞石笋记录趋势一致,共同记录了此时段夏季风强度总体减弱的过程。在百年尺度上,太阳活动减弱时期对应于石笋氧同位素偏正时期,支持在百年尺度上太阳活动对季风强度的驱动机制。石笋碳同位素最显著的特征是在870～730aBP期间从-10‰偏负到-14‰,振幅达到4‰,说明区域植被发生了明显的改变,人类活动干扰有可能是造成这种变化的原因。

We present in this paper the 230Th-dated stalagmite stable isotope record from Tian＇e Cave in Fujian province,Southeast China.This record provides an Asian Monsoon（AM） history during a time interval from 2 100~590 aBP.In the TE2 δ18O record,the long-term decreasing trend correlates well with the Heshang Cave δ18O change,supporting that the Asian Monsoon intensity is controlled by the migration of Inter-tropical Convergence Zone（ITCZ）.A comparison between the stalagmite δ18O record and the Total Solar Irradiance record provides strong evidence for solar forcing of East Asian monsoon on centennial to multi-decadal time-scales.An important characteristic of the TE2 isotopic record is an abrupt large shift of the carbon isotopic ratio（4‰）,suggesting intensified soil erosion occurred on the overlain soil due to the destruction of the climax vegetation as a result of constant human disturbance.