中全新世东亚季风年至10年际气候变率:湖北青天洞5.56~4.84ka B.P.石笋年层厚度与地球化学证据  

ANNUAL-TO DECADAL-SCALE VARIABILITY OF ASIAN MONSOON CLIMATES DURING MID-HOLOCENE:EVIDENCE FROM PROXIES OF ANNUAL BANDS AND GEOCHEMICAL BEHAVIORS OF A SPELEOTHEM FROM 5.56ka B.P.TO 4.84ka B.P.IN QINGTIAN CAVE,CENTRAL CHINA

作　　者：张振球[1] 刘殿兵[1] 汪永进[1] 王权[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》2014年第6期1246-1255,共10页Quaternary Sciences

基　　金：国家自然科学基金重点项目(批准号:41130210)资助

摘　　要：中全新世年至10年际东亚季风气候变率及其动力学机制有助于深入了解当今全球气候变暖的自然变率贡献。本文基于湖北青天洞一支石笋的铀系年龄、年纹层计数、氧同位素和微量元素测量结果,建立了中全新世5.57~4.84ka B.P.时段平均分辨率为3~4年的东亚季风气候和洞穴地点环境演变序列。石笋年纹层由冬季亮色薄层和夏季暗色厚层组成,对应冬、夏季节层的δ^(18)O和δ^(13)C正负漂移与现今冬夏降水和岩溶环境同位素值变化基本吻合。然而,元素比值(Mg/Ca和Sr/Ca)揭示了冬夏季风降水与岩溶作用的复杂响应过程。在10年际尺度上,石笋氧同位素记录了3次间隔200年左右的弱季风事件,分别发生于5.56~5.50ka B.P.,5.26~5.20ka B.P.和5.01~4.94ka B.P.,每个事件大约持续60年,反映了太阳活动周期控制季风强度变化的频率。Mg/Ca和Sr/Ca比值与季风强弱变化不存在明显的对应关系,但其功率谱具有200年和40年左右周期,说明东亚季风气候和岩溶环境过程之间既有共同的控制因素又有不同的演化机理。Qingtian Cave （31 ° 30′N,110°22′E ; 1630m above sea level） is located between the northern slope of Mt.Shennongjia and the southern slope of Mt.Laojunshan,Hubei Province,Central China.The area was influenced by subtropical monsoon climate in China,with abundant rainfall and high temperature in summer,and vise versa in winter.The local mean annual temperature and rainfall are around 7.4℃ and 1500～ 2000mm,respectively.Relative humidity in the cave is around 100％.One stalagmite （QT33） was collected in the deep site of the cave.This stalagmite is 118mm in length and 80～95mm in diameter.It is composed of pure calcites,with no evidence for hiatuses on the polished surface.The sample shows nearly horizontal layers perpendicular to the growth axis throughout the whole vertical profile.These layers are composed of transparent and dark inclusion-rich calcite couplets,which have been proven to be annual bands.Three sub-samples were collected along the central growth axis with 0.9mm-diameter carbide dental burrs for 230Th datings.The measurements were performed by inductively coupled plasma mass spectrometry （ICP-MS） on a Finnigan-MAT Element at the Department of Geology and Geophysics,University of Minnesota,USA.The reported error is ± 26σ.A total of 224 sub-samples for o18O measurements were run with on-line automated carbonate preparation system （Kiel Carbonate Device） lirnked to finingan MAT-253 at Speleothem Isotope Laboratory of Nanjing Normal University,yielding a standard deviation error of 0.06‰o.Trace element analyses were performed using Avaatech XRF （X-ray fluorescence spectrometry） Core Scanner along the growth axis with an area of 0.5mm × 12mm at the Surficial Geochemical Laboratory,Nanjing University.The error for this measurement is less than 20％.Thirteen sets of Ca2＋,Mg2＋,Sr2＋ and Ba2＋ data within annual bands were analyzed by Optima-2100DV inductively coupled plasma emission spectrometer （ICP-OES） and Element XR ICP-MS at the Geochemical and Isotopic Labo

关 键 词：中全新世 地球化学指标 纹层石笋 湖北青天洞 

分 类 号：P534.632[天文地球—第四纪地质学]