基于黔北三星洞石笋(SX29)9个铀钍年龄和420个氧同位素分析,获得了113.60.3~106.20.4 ka BP(相对于1950年)10年际分辨率的delta~(18)O时间序列. 该石笋delta~(18)O时间序列记录了MIS 5d/5c 转换时亚洲夏季风强度变化的突变过程. 根据突变过程中间点的年龄确定 MIS 5d/5c突变时间为108.10.3 ka BP. 石笋记录对MIS 5d/5c突变时间的精确标定可以作为MIS 5阶段重要的年龄控制点, 用以校正南北极冰芯记录和深海沉积记录的时间标尺. 季风 MIS 5d/5c转换阶段也表现为类似过去4个冰消期的2个阶段变化过程: 阶段Ⅰ为夏季风较弱时期,而南极温度缓慢上升; 阶段Ⅱ为夏季风快速增强时期, 与甲烷浓度突变同步, 南极温度则上升至最高值.
英文摘要:
From nine high-precision ~(230) Th ages and 420 oxygen isotope data points, a stalagmite from Sanxing Cave in northern Guizhou Province reveals the precipitation history of the Asian Summer Monsoon (ASM) from 113.60.3 to 106.20.4 ka BP (relative to AD 1950). The decadal-scale high-resolution delta~(18) O record shows an abrupt transitional from Marine Isotope Stage (MIS) 5d to 5c. The stalagmite-inferred time interval of the ASM abrupt transition at MIS 5d/5c is between 108.3 and 107.9 ka BP with a 2sigma uncertainty of 0.3 ka; the mid-point of this transition is 108.10.3 ka BP. The well-dated MIS 5d/5c abrupt transition can be used as an age marker for chronological calibration of bipolar ice cores and marine records. The ASM underwent a two-phase process during the transition,similar to those for the last four deglaciations. Phase I involved a weak monsoon stage that lasted for several millennia, concurrent with an Antarctic temperature rise. Phase II was marked by rapid intensification of monsoonal precipitation, synchronous with increasing atmospheric CH_4 concentration and high thermal conditions in Antarctica.