“8.2ka”事件的湖北神农架高分辨率年纹层石笋记录  

THE ASIAN MONSOON VARIABILITY AROUND 8.2ka B.P.RECORDED BY AN ANNUALLY-LAMINATED STALAGMITE FROM Mt.SHENNONGJIA,CENTRAL CHINA

作　　者：邓朝[1] 汪永进[1] 刘殿兵[1] 张振球[1] 

机构地区：[1]南京师范大学地理科学学院,南京210023

出　　处：《第四纪研究》2013年第5期945-953,共9页Quaternary Sciences

基　　金：国家自然科学基金重点项目(批准号:2007105GZ10033);江苏省2011年度普通高校研究生科研创新计划立项项目(批准号:CXLX11_0872)共同资助

摘　　要：基于湖北神农架青天洞1支长179mm石笋的8个^(230)Th年龄、890条纹层和445个氧同位素数据,建立了早全新世8.8~7.9kaB.P.时段平均分辨率为2a的亚洲季风气候记录。结果显示,8.34~8.10kaB.P.期间石笋δ^(18)O明显正偏,指示了一次持续约240a的弱夏季风事件。该弱夏季风事件与同期格陵兰冰芯记录的中心事件(在8.21kaB.P.,持续70a)及淡水注入模拟结果基本一致,表明"8.2ka"事件与淡水注入导致的大西洋经向翻转流减弱或关闭有关。然而,"8.2ka"事件发生前约120a,亚洲季风已开始逐渐减弱,与太阳活动明显减弱时间相对应,据此推测太阳活动可能对"8.2ka"事件具有一定的触发作用。The Qingtian cave（31°30＇N,110°22＇E; 1630m above sea level）is located at Mt.Shengnongjia,Hubei Province.The terrain is averagely 1500m a.s.l.and generally become lower from SW to NE.The local annual precipitation averagely is between 1500mm and 2000mm,most of which falls between June and September.The relative humidity and temperature in the cave are about 100% and 15.5℃,respectively.One stalagmite（QT40）was collected deep in the cave.This sample is 179mm in height,with a diameter from 65mm to 76mm.The stalagmite is composed of pure calcite deposition,without evident porous on the polished surface.We identified a potential hiatus between the depth of 3mm and 19mm,supported by 230Th dating and annual lamina counting results.So we focused our oxygen isotope analysis on the section below the depth of 19mm.Nine samples for 230Th dating were conducted at the Isotope Laboratory of Geology and Geophysics Department Minnesota University,USA.A total of 445 samples for δ18O measurements were analyzed with on-line automated carbonate preparation system（KIEL CARBONATE DEVICE）linked to Finnigan MAT -253 ratio mass spectrometer at the Isotope Laboratory of College of Geography Science,Nanjing Normal University.A 2-year-resolution δ18O record between 8.8kaB.P.and 7.9kaB.P.was reconstructed on 8 230Th dates,445 stable isotope measurements and 890±14 annual bands.The δ18O time series shifts within a range of 1.4‰ .Our high-resolution δ18O record reveals a striking weak summer event between 8.34-8.10kaB.P.,with a double-plunging structure.This characteristic has been reported previously in cave records from Southern China and Oman,and appears to different from the δ18O record from the Nuanhe cave,Northern China.In comparison with the recent model simulations and δ18O record from Greenland ice cores,it is possible that the ＂8.2ka＂ event can be coupled to changes in the Atlantic Meridional Overturning Circulation triggered by a glacial lake outburst.However,the monsoonal ＂8.2ka＂ event appears to in

关 键 词：早全新世 “8 2ka”事件 太阳活动 年纹层石笋 青天洞 

分 类 号：P597[天文地球—地球化学] P534.632[天文地球—地质学]