13ka以来东亚夏季风演变过程和全新世适宜期问题

基于湖北神农架三宝洞石笋SB43的21个230Th年龄和486个氧同位素数据，建立了13．0-0．2ka时段东亚夏季风强度演化序列，其长期演化趋势与33°N太阳辐射变化基本一致。通过对比三宝洞、董歌洞、阿曼Qunf洞及和尚洞石笋δ18O记录，发现东亚和印度季风强度在轨道尺度上呈同相位变化。石笋SB43、D4 δ18O值与Cariaco盆地Ti含量曲线整体变化一致，相关系数高达0．8，表明热带辐合带（ITCZ）的南北移动可能对亚洲中低纬季风强度起放大作用；全新世适宜期在亚洲季风区不存在显著穿时性，起止时间大体一致，约为10．2～5．7ka。早、中全新世季风强度与极地温度变化趋势一致，相关系数高达0．9，表明当时高纬冰量边界条件可能对亚洲季风强度变化（包括ITCZ的平均位置）具有贡献作用。

Long-term trend of East Asian summer monsoon over the last 13 ka and a preliminary discussion on Holocene Optimum

An independently-dated, high-resolution oxygen-isotope record from stalagmite SB43, collected from Sanbao Cave, Shennongjia, reflects the evolution of East Asian summer monsoon over the last 13 ka. Twenty one sub-samples were dated by Finnigan MAT 262-PRQ type meter at the Isotope Laboratory of Geology and Geophysics Department, Minnesota University, USA, and 486 δ18O data were conducted with MAT 253 mass spectrometer linked with automatic equipment at Isotope Lab, Nanjing Normal University. The results provide mean 26-yearresoluton paleoelimate record of East Asian summer monsoon, and the long trend of δ18O record generally follows changes in summer insolation at 33°N latitude. A comparison between four stalagmite records that they have consistent δ18O pattern from Asian continental interior, shows that Indian Ocean monsoon and East Asian summer monsoon may share the same climatic driving mechanism at the orbital timescale, such as the Intertropical Convergence Zone （ITCZ）. During early- and mid-Holocene, a decrease in δ18O values indicates a northward shift in the mean position of the ITCZ and the associated Asian summer rainfall belt. During late Holocene, the ITCZ migrated southward and summer monsoon intensity decreased gradually in response to a reduction in boreal solar insolation. Furthermore, the previously reported time-transgressive Holocene Optimum isn＇t further supported by our record, because our comparison shows that Holoeene Optimum in Asian continent identically lasts from 10.2 to 5.7 ka, when relatively negative δ18O values indicate a period of high summer monsoon intensity in spite of latitudinal difference. The correlation of the intensity of East Asian summer monsoon with changes in arctic temperature in early- and mid-Holocene suggests high-latitude glacial boundary conditions may play an important role in the intensity of summer monsoon and the mean position of the ITCZ, which potentially acts as an amplifier for the rapid climate variations.