黔西南石笋记录MIS3/2阶段百年尺度季风演变和H事件特征  

ASIAN MONSOON CHANGES ON CENTENNIAL-SCALE AND CHARACTERS OF HEINRICH EVENTS DURING THE MIS 3/2 TRANSITION FROM A STALAGMITE RECORD IN SOUTHWEST CHINA

作　　者：赵侃[1] 汪永进[1] 

机构地区：[1]南京师范大学地理科学学院,南京210046

出　　处：《海洋地质与第四纪地质》2011年第2期121-128,共8页Marine Geology & Quaternary Geology

基　　金：国家自然科学重点基金项目(40631003)

摘　　要：基于黔西南雾露洞石笋(Wu32)12个230 Th年龄和371个氧同位素分析,获得了末次冰期29～20.8kaBP分辨率约20年的亚洲夏季风演变序列。该石笋δ18 O时间序列与南京葫芦洞记录在重叠时段基本一致,更为详细地记录了深海氧同位素3阶段向2阶段(MIS3/2)转换时期亚洲夏季风强度的变化过程。MIS3/2转换期季风强度伴随北半球太阳辐射强度变化,呈逐步减弱趋势,并在此趋势上叠加了数个千年至百年尺度事件。其中弱夏季风事件与格陵兰粉尘浓度增加相对应,表明大气环流对气候信号的全球快速传输具有重要作用,同时指示末次冰期亚洲夏季风和冬季风在千年至百年尺度上存在反相位关系。石笋δ18 O值在24.2和25.7kaBP左右明显正偏,振幅达1.5‰,指示两次显著的弱夏季风事件,对应于北大西洋冰漂碎屑事件H2的双峰结构。这一结构特征和末次冰消期H1事件一致,说明H1和H2事件可能受控于共同的驱动因素。A high-resolution stalagmite oxygen isotope record from the Wulu Cave,based on 371 oxygen isotope measurements and 12 precise 230Th dates,has provided a detailed Asian summer monsoon（ASM） history from 29 to 20.8 kaBP,spanning the marine isotope stage 3 and 2.The calcite δ18O records are essentially similar with the previously reported Hulu record formed during the same stage,although they are geographically far away（about 1,000 kilometers between the two sites）.This supports the idea that changes in speleothem δ18O may represent variations in isotopic composition of precipitation associated with large-scale summer monsoon circulation over a large portion of China.Stalagmite Wu32 exhibits a first order increasing trend of δ18O values,which follows the changes in northern summer insolation.Superimposed on the long-term trend are a number of centennial-millennial scale monsoon events.The distinct positive excursions in δ18O exhibit a striking correlation with the Greenland Ca2＋ record and ice-rafting events in the North Atlantic.This indicates that atmospheric circulation changes are important in transmitting abrupt climate signals globally and implies that the Asian summer monsoon is likely anti-phased with the winter monsoon on centennial to millennial-scales.Two remarkable weak summer monsoon events at 25.7 and 24.2 kaBP,indicated by a large abrupt 1.5 shift in δ18O,are coincident with H2b and H2a in the North Atlantic within error.The two peaks in H2 event are identical to those in H1,suggesting a common driving force of the H1 and H2 events.

关 键 词：石笋 亚洲季风 H2事件 MIS3/2阶段 

分 类 号：P532[天文地球—古生物学与地层学]