DO4事件的精确定年及亚旋回特征:来自福建龙岩仙云洞石笋的证据

Precise dating of the Dansgaard-Oeschger event 4 and its sub-cycles:Evidence from a stalagmite from Xianyun Cave in Longyan City,Fujian Province

DO4事件(Dansgaard-Oeschger event 4,简称DO4事件)是发生在MIS3阶段后期的1次明显升温事件。根据福建仙云洞石笋(编号XYⅢ-28) 300~500 mm层段6个高精度230Th年龄和188个氧同位素数据,获得了29.13~27.94 kyr B.P.时期平均分辨率达7 yr的东亚夏季风强度的演变过程数据。该石笋δ^18O记录的DO4事件起止时间为28.83±0.06~28.46±0.06 kyr B.P.,持续时间为0.37±0.06 kyr。相对基于GICC05年层计数时标NGRIP冰芯δ^18O记录在DO4开始阶段的突变特征,仙云洞石笋记录的DO4事件开始阶段δ^18O值在145±60 yr内偏负0.4‰,表现为相对缓慢的变化特征,这说明仙云洞所处的中国东南沿海地区有可能受到热带低纬海气耦合的影响。此外,仙云洞石笋δ^18O记录揭示了在DO4事件内部及附近存在一系列的百年至十年际尺度夏季风增强事件,与格陵兰冰芯δ^18O记录、阿拉伯海海盆反照率记录的DO4事件亚旋回结构在定年误差范围内相对应,表明东亚夏季风强度与北高纬温度变化和ITCZ (赤道辐合带)位置移动在百年至十年际尺度上存在紧密的联系。

The Dansgaard-Oeschger event 4( DO4 event) is a significant warming event that occurred in the late Marine Isotope Stage 3. At present,there are different understandings about the detailed characteristics and internal structures of the DO4 event. Based on 6 precisely-dated 230Th ages and 188 oxygen isotope data of a stalagmite( No. XYⅢ-28) from the Xianyun Cave,Fujian Province,we present δ^18O time series with an average resolution of 7 yr from 29. 13 to 27. 94 kyr B. P. Our new stalagmites δ^18O records uncover the detailed processes of the DO4 event. The onset and end time of the DO4 event recorded by the stalagmite δ^18O is 28. 83±0. 06 and 28. 46±0. 06 kyr B. P.,respectively,and the duration is 0. 37±0. 06 kyr. Differential with abrupt change of NGRIP ice core δ^18O record at the onset of DO4 based on the GICC05 layer count time scale,the Xianyun Cave δ^18O shows a relatively slow change. The Xianyun stalagmite δ^18O values negatively shift by 0. 4‰ within 145 ± 60 yr,which indicates that the Xianyun Cave was likely affected by the ocean-atmosphere coupling of the tropical. In addition,the Xianyun stalagmite δ^18O reveals a series of sub-million-scale summer monsoon enhancement events in and around the DO4 event,corresponding to the NGRIP ice core δ^18O record and the Arabian Sea basin record. Our results suggest that the East Asian summer monsoon is related to the north-high latitude temperature and the ITCZ position changes on the sub-millennium-scale event.